The physics of the problem are deceptively simple. When ambient temperature and humidity rise, the temperature gradient between the skin and the surrounding air shrinks, and evaporative cooling through sweat becomes less efficient. The body must then rely on increased heart rate and blood flow to the skin to dissipate heat, straining the cardiovascular system. When internal temperature regulation fails, the result can be heat exhaustion or the far more dangerous heat stroke, in which core temperatures exceed the thresholds at which enzymes and cell membranes function normally. But the editorial emphasizes that the acute syndromes are only part of the picture. Repeated exposure over months and years is linked to chronic kidney disease, sustained cardiovascular strain, and impaired mental health, making heat a slow-acting occupational hazard as well as a sudden one.

Heat also degrades the very capacities that keep workers safe. Elevated thermal load reduces both cognitive performance, including attention and decision-making, and physical performance, including strength and endurance. That combination increases the likelihood of occupational injuries, from machinery errors on a factory floor to falls on a construction site. The risks are compounded, the authors note, by high physical workloads, inadequate rest breaks, limited hydration, and insufficient workplace protections, factors that determine how much heat burden a worker actually absorbs on any given shift.

Workers in construction, agriculture, manufacturing, warehousing, and emergency response face significant risks from both outdoor and indoor heat exposure. Indoor settings are not refuges: warehouses, foundries, and kitchens can generate heat loads comparable to outdoor extremes, particularly where ventilation is poor. What unites these sectors is that heat exposure is often a structural feature of the job rather than an occasional weather event, which means prevention must be built into how work is organized, not improvised when the forecast turns hot.

A central theme of the editorial is that the burden of occupational heat exposure is not equally distributed. Migrant workers, temporary laborers, and those in low-resource or informally regulated environments are disproportionately affected, often because they lack access to shade, water, rest, health insurance, or the legal standing to refuse unsafe conditions. These inequities, the authors argue, highlight the need for targeted research and interventions that address the structural and social determinants of exposure and risk, rather than treating heat vulnerability as a purely individual or physiological matter.

The special issue showcases advances in exposure science that are enabling more precise and dynamic characterization of heat exposure. Wearable sensors, real-time environmental monitoring, and physiological measurements offer new opportunities to quantify individual-level exposures and link them to health outcomes. One methodological study deployed small, lightweight personal sensors among agricultural workers to examine the relationship between heat exposure and heart rate variability, a physiological signal that reflects how the autonomic nervous system responds to thermal strain. Such approaches are essential for improving risk assessment and informing evidence-based standards, because they capture what a specific worker actually experiences rather than what a distant weather station records.

The epidemiological contributions sharpen the picture of who is affected. One analysis examined cardiovascular risk factors among migrant and seasonal farmworkers using two decades of National Agricultural Workers Survey data, providing longitudinal evidence on a population that is both heavily exposed and hard to study. Another assessed the incidence and sociodemographic disparities of heat-related illness among outdoor workers in the United States from 2010 to 2019, documenting how risk is patterned by social position. A policy-focused case study from Italy evaluated the effectiveness of a heat-related occupational prevention strategy, offering rare real-world insight into how national prevention programs perform when temperatures spike.

Heat reaches beyond the cardiovascular system, and the special issue reflects that breadth. One contribution investigates the effects of high ambient temperatures on liver function, exploring inflammatory pathways and age-related susceptibility. The work suggests that thermal stress may trigger systemic inflammatory responses with organ-level consequences, and that older workers may be biologically more vulnerable to the same exposure. Rounding out the collection, a forward-looking perspective emphasizes integrating worker protection into climate action, underscoring the importance of climate-responsive occupational health frameworks that treat heat adaptation as a core component of climate policy rather than an afterthought.

Beyond characterizing exposure, the editorial stresses a critical need to evaluate and implement effective interventions. Engineering controls such as ventilation and shading, administrative measures such as work-rest cycles, and policy initiatives including occupational heat standards and early warning systems are central to prevention efforts. The challenge, the authors write, is ensuring that these interventions are feasible, scalable, and equitable across occupational settings, from large regulated industries to informal economies where enforcement is limited. The interdisciplinary studies in the special issue, integrating exposure science, epidemiology, and occupational health, contribute to the growing evidence base needed to inform such policies and practices.

Addressing occupational heat stress, Choi and Zhang conclude, is both an environmental and public health imperative. As extreme heat events grow more frequent, the editorial and the research it introduces aim to stimulate further study and support the development of effective strategies to safeguard workers’ health and well-being, before the warming climate turns an already measurable hazard into an unmanageable one.

Subject of Research: Editorial: heat stress and worker health, safety, and well-being

Article Title: Editorial: heat stress and worker health, safety, and well-being

Article References: Choi, S. D., & Zhang, K. (2026). Editorial: heat stress and worker health, safety, and well-being. Journal of Exposure Science & Environmental Epidemiology. https://doi.org/10.1038/s41370-026-00991-3

Image Credits: AI Generated

DOI: 10.1038/s41370-026-00991-3

Keywords: heat stress, occupational health, climate change, worker safety, exposure science, heat stroke, farmworkers, wearable sensors, public health, heat-related illness, occupational epidemiology, workplace interventions

The scale of the dataset is what makes the analysis unusual. Most studies of heat and health have focused on single cities, limited age groups, or narrow sets of diagnoses. This study, by contrast, drew on statewide emergency department records from the California Department of Health Care Access and Information, covering every visit in the state over a 13-year span. The researchers sorted the visits into three clinical groupings: heat-related physical illness, which includes septicemia, fluid and electrolyte disorders, congestive heart failure, renal failure, urinary tract infections, and heat stroke; heat-related mental health visits, spanning diagnoses from anxiety and mood disorders to schizophrenia, substance use, and intentional self-injury; and all-cause visits, meaning every emergency department encounter regardless of diagnosis. In total, the physical illness grouping contained more than 13.8 million visits and the mental health grouping more than 15.7 million.

To connect those visits to temperature, the team used daily gridded mean temperature data at 4-kilometer resolution from the PRISM Climate Group, a statistical mapping system that blends observations from federal, state, and local weather station networks with a digital elevation model to account for California’s notoriously complex topography, including rain shadows, temperature inversions, slope aspect, and coastal proximity. Using Google Earth Engine, the researchers performed a spatial join that computed the area-weighted mean of all grid cells intersecting each ZIP code polygon on each day. Over the study period, the statewide average temperature was 16.2 degrees Celsius, with ZIP code averages ranging from 12.6 to 18.1 degrees across the state’s six Health Officer Regions, which span everything from the cool, foggy Bay Area to the scorching agricultural interior of Central California.

The statistical engine of the study was the distributed lag nonlinear model, or DLNM, a framework widely used in environmental epidemiology that can simultaneously capture two features of the temperature-health relationship: its nonlinearity and its timing. In the first stage, the researchers fitted a quasi-Poisson time-series regression for each individual ZIP code, modeling the exposure-response curve with a quadratic B-spline whose three internal knots were placed at the 10th, 75th, and 90th percentiles of each location’s temperature distribution. The lag-response curve, which describes how risk evolves after exposure, was modeled with a natural cubic spline over a three-day window, reflecting evidence from prior heat-health studies that most excess risk occurs within zero to three days of exposure. Alternative specifications with longer lags and different spline complexity were compared using the Akaike Information Criterion, and the final model produced smooth, epidemiologically plausible curves, with risk peaking within a day of exposure and declining toward zero by day three.

Because small ZIP codes with few emergency visits produce noisy estimates, the second stage pooled the location-specific results with a multivariate meta-regression and derived best linear unbiased predictions for each ZIP code, allowing sparsely populated areas to borrow statistical strength from larger, climatically similar neighbors. Local average temperature and temperature range were included as meta-predictors, since local climate is known to modify how temperature affects health. From these fitted curves, the team calculated each ZIP code’s minimum morbidity temperature, the point at which heat-related illness is minimized, and used it as the reference for computing attributable fractions: the proportion of emergency visits that would not have occurred had temperatures stayed at that optimum.

The headline numbers are striking. Statewide, 5.1 percent of heat-related physical illness visits, 5.4 percent of heat-related mental health visits, and just under 1 percent of all-cause emergency visits were attributable to heat. Regionally, Central California and Los Angeles carried the largest heat-attributable fractions for physical illness, at 6.5 percent and 6.1 percent respectively, while Los Angeles, Southern California, and Central California led for mental health visits. The Rural North and Greater Sierra-Sacramento regions, despite their cooler average temperatures, had the largest fractions of all-cause heat-attributable visits, a pattern the authors suggest may reflect lower acclimatization and weaker adaptive capacity in communities unaccustomed to extreme heat.

The most consequential findings, however, concern social inequality. To measure it, the researchers turned to the California Healthy Places Index, or HPI, a composite metric developed by health departments and community organizations that ranks every census tract on a 0-to-100 scale based on 23 social determinants of health most strongly associated with life expectancy at birth. These indicators are grouped into eight policy-action domains covering the economy, education, transportation, housing, social resources, the built and clean environment, and health-care access. Low-scoring communities are marked by poverty, unemployment, overcrowded and cost-burdened housing, limited car ownership, long commutes, sparse tree canopy, higher pollution, and low insurance coverage. When the researchers divided ZIP codes into HPI quartiles, a clear gradient emerged: as community conditions improved, emergency visit rates and heat-attributable rates fell for all three outcome categories. ZIP codes in the lowest quartile held 27 percent of the state’s population but contributed 33 percent of physical illness visits, 32 percent of mental health visits, and 35 percent of all-cause visits, and had 2.2 times more total emergency visits than the healthiest quartile.

Expressed as rates, the disparity becomes even sharper. Statewide, heat-attributable visits averaged 141 per 100,000 people annually for physical illness, 165 for mental health, and 317 for all causes. In the lowest HPI quartile, the rate ratios relative to the healthiest quartile were 4.3 for physical illness, 2.1 for mental health, and 2.6 for all-cause visits, with confidence intervals that did not overlap across quartiles. Central California recorded the highest physical illness rate at 218 visits per 100,000, a rate ratio of 3.4 relative to the Bay Area, while the Rural North posted the highest mental health and all-cause rates at 234 and 852 per 100,000. The authors point to mechanisms embedded in the HPI itself: limited access to parks, beaches, shade, and transportation, combined with less air conditioning and fewer green spaces, can raise both heat exposure and vulnerability, while higher stress and reduced access to health services may amplify the physiological and psychological toll.

The study also exposed a systematic blind spot in official statistics. When the researchers compared their population-weighted county estimates with crude heat-associated emergency visit rates in Tracking California, the state’s environmental public health tracking network, their estimates were on average seven times higher, with a range of 2.3 to 18 times. Tracking California relies on heat-specific diagnosis codes appearing in medical records, which the authors argue captures only direct attribution and misses the many heat-related illnesses that present as cardiac, renal, or psychiatric emergencies. Correlations between the two data sources were strong for physical outcomes but weak and statistically insignificant for mental health, suggesting that the psychological burden of heat is the most undercounted of all.

With climate projections pointing to more frequent, intense, and longer-lasting heat waves, the authors frame their results as a conservative baseline rather than a worst case, noting that the study period ends before California’s recent record-breaking heat. They argue that extreme heat action plans, such as California’s 2022 state resilience strategy, could be made more effective by directing investments toward the ZIP codes this analysis identifies as having both unhealthy conditions and high heat-attributable rates: more trees and shaded areas, public air-conditioned spaces, cooling stations, cool roofs and pavement, and housing-focused measures such as weatherization incentives, subsidies for cooling technologies, and utility assistance. Because the study assigned visits to residential ZIP codes, it excluded people experiencing homelessness, who are among the most heat-vulnerable, and the authors caution that humidity and air pollution were not controlled. Even so, the message is unambiguous: heat is not an equal-opportunity hazard, and protecting the communities with the fewest resources for healthy living is both an equity imperative and the most efficient way to reduce the strain that rising temperatures place on emergency care.

Subject of Research: Inequities in heat-attributable emergency department visits across California communities

Article Title: Inequities in heat-related emergency department visits in California from 2005 – 2017

Article References: Donnelly, M., Lappe, B., Milet, M., & Vargo, J. (2026). Inequities in heat-related emergency department visits in California from 2005 – 2017. PLOS Climate, 5(10), e0000586. https://doi.org/10.1371/journal.pclm.0000586

Image Credits: AI Generated

DOI: 10.1371/journal.pclm.0000586

Keywords: extreme heat, emergency department visits, California, health equity, Healthy Places Index, distributed lag nonlinear model, climate change, mental health, social determinants of health, heat-attributable fraction, public health surveillance, acclimatization

The editorial is authored by senior author Eileen T. Lake, the Edith Clemmer Steinbright Professor in Gerontology, Professor of Nursing and Sociology, and Associate Director of the Center for Health Outcomes and Policy Research, together with Domenique Villani, a predoctoral fellow at the center, and Ysabella Perez, a recent Penn graduate and research assistant at the center. Their central argument is straightforward but consequential: building genuine climate resilience into the health system requires ensuring that bedside nurses have the organizational capacity and the material resources needed to deliver timely care and continuous surveillance during heat events, when patient volumes can spike suddenly and patient conditions can deteriorate rapidly.

The physiological rationale behind this argument is well established in clinical medicine. Extreme heat places severe stress on the human body, particularly the cardiovascular system, which must work harder to dissipate heat through increased blood flow to the skin. In vulnerable populations, including older adults, people with chronic cardiovascular or respiratory disease, patients taking medications that impair thermoregulation, and those with limited access to cooling, prolonged heat exposure can progress from heat exhaustion to life-threatening heat stroke. Heat stroke is a medical emergency characterized by core body temperatures above roughly 40 degrees Celsius and central nervous system dysfunction, and it can trigger a cascade of complications including rhabdomyolysis, acute kidney injury, coagulopathy, and multi-organ failure. Surviving such a cascade depends heavily on early recognition and rapid, sustained intervention.

This is precisely where nursing care becomes decisive. The editorial emphasizes that the management of heat-related illness requires immediate and resource-intensive nursing surveillance to prevent complications and to catch the signs of rapid patient deterioration before they become irreversible. Continuous monitoring of vital signs, fluid balance, electrolyte status, and neurological function is the daily work of bedside nurses, and during a heat wave the volume of patients needing this level of attention can rise sharply at exactly the moment when a hospital’s workforce is under maximum strain. Nurses themselves are also exposed to the same environmental conditions, and heat events can affect staff wellbeing and performance, adding another layer of pressure on the workforce during surges.

The authors warn that insufficient staffing and inadequate organizational support can severely limit a health system’s ability to deliver standard-of-care treatments during the sudden volume surges that heat waves produce. A hospital may have the physical beds, the cooling capacity, and the IV fluids to handle an influx of heat-affected patients, but if there are not enough nurses to perform the frequent assessments, administer cooling protocols, titrate fluids, and escalate deteriorating patients to higher levels of care, the theoretical surge capacity fails in practice. In this sense, the editorial reframes nurse staffing not as a cost line to be minimized but as a functional limit on how much emergency care a hospital can actually deliver when environmental disasters strike.

The argument rests on a substantial body of research from the Center for Health Outcomes and Policy Research and collaborators, which has repeatedly demonstrated that the ratio of patients to nurses and the quality of the nurse work environment are associated with patient outcomes including mortality, failure to rescue, lengths of stay, and rates of complications. Studies in this tradition have shown that hospitals with better work environments, characterized by adequate staffing, strong nurse-physician relationships, nurse participation in decision-making, and supportive management, achieve better outcomes even at similar staffing levels. Extending this evidence base to climate-driven emergencies is a natural progression, and it suggests that the organizational features that protect patients in ordinary times become even more critical when the system is stressed by a heat crisis.

Looking forward, the editorial does not stop at diagnosis. It outlines actionable recommendations across four domains: research, education, practice, and policy. On the research side, the authors call for studies that specifically examine how staffing and work environment characteristics shape outcomes during heat events, filling a gap in the disaster preparedness literature that has traditionally focused on infectious disease outbreaks, mass casualty trauma, and hurricanes. On education, the implication is that nursing curricula and continuing professional development should prepare clinicians to recognize and manage heat-related illness and to understand the systems-level factors that determine whether such care can be delivered effectively during a surge.

In the domain of practice, the editorial urges health system leaders to incorporate nurse staffing and workplace environment investments directly into disaster preparedness planning, rather than treating workforce questions as separate from emergency management. Concretely, this could mean including staffing models in heat response plans, ensuring that nurses have the equipment and authority to implement cooling and monitoring protocols efficiently, and designing work environments that protect staff as well as patients during extreme temperatures. On the policy front, the authors’ message is directed at regulators, accreditors, and hospital administrators: if extreme heat is now a recurring, predictable public health emergency, then the workforce that delivers the front-line response deserves the same strategic investment and planning attention as any other piece of emergency infrastructure.

The broader context gives this argument urgency. Heat waves in the United States have grown more frequent, more intense, and longer-lasting in recent decades, consistent with the warming trend driven by climate change, and emergency departments in many regions have reported rising numbers of heat-related visits during recent summer seasons. Public health agencies have long emphasized individual-level precautions, such as hydration, air conditioning, and checking on vulnerable neighbors, but the hospital-level response has received comparatively less attention. The editorial’s contribution is to shift the focus from the community to the bedside, insisting that what happens inside the hospital, and specifically how many nurses are available and how well supported they are, is a measurable determinant of who survives a heat emergency.

The authors state their conclusion plainly: extreme heat is no longer just a public health issue, but an immediate hospital preparedness priority that requires treating nurse staffing and supportive work environments as essential emergency infrastructure. As climate projections indicate that dangerous heat events will become more common in the coming decades, hospitals that invest now in their nursing workforce, in both numbers and working conditions, may find themselves measurably better equipped to protect their patients when the next heat wave arrives. The editorial, titled How Nursing Can Strengthen Hospital Preparedness for Extreme Heat, was published in Public Health Nursing in September 2026 and represents a call to action for health system leaders, educators, researchers, and policymakers alike to place the nursing workforce at the center of climate resilience planning.

Subject of Research: The role of hospital nurse staffing and work environments in extreme heat emergency preparedness

Article Title: New editorial calls for investing in hospital nursing workforce to address health impacts of extreme heat

Article References: New editorial calls for investing in hospital nursing workforce to address health impacts of extreme heat. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: extreme heat, nurse staffing, hospital preparedness, Public Health Nursing, climate resilience, heat-related illness, emergency department, patient outcomes, nursing workforce, health policy, University of Pennsylvania, heat wave

The survey, the 30th wave of a nationally representative panel study, was conducted Aug. 4-17, 2026, among 1,904 empaneled U.S. adults by SSRS, an independent research company, using both web and telephone interviews. The margin of sampling error for the full sample is plus or minus 3.2 percentage points at the 95 percent confidence level, and the data were weighted to reflect the U.S. adult population. Sixty-five percent of respondents said climate change is increasing the risk of heat-related illnesses, respiratory diseases, and insect-borne diseases. That figure is unchanged from August 2025, when it also stood at 65 percent, and from July 2024, when it reached 67 percent, but it is significantly higher than the 58 percent recorded in November 2023. The trajectory suggests a durable shift in public perception rather than a temporary spike tied to any single weather event.

Americans also broadly recognize that heat waves themselves are intensifying. Sixty-two percent say U.S. heat waves are becoming more frequent and more intense than in the past, statistically unchanged from 61 percent in August 2025, 65 percent in July 2024, and 58 percent in November 2023. The survey measured four categories of extreme weather and their effects on daily routines. Extreme outdoor heat topped the list, with 76 percent of respondents reporting that it affected their daily activities at least sometimes over the past year. Poor air quality resulting from wildfire smoke came next at 38 percent, while flooding (20 percent) and tornadoes or hurricanes (11 percent) were cited far less often, consistent with their lower frequency. Notably, the more frequently respondents reported that extreme heat, poor air quality, or flooding had disrupted their daily activities, the more likely they were to believe that climate change is raising the risk of heat-related, respiratory, and insect-borne illnesses.

The financial toll of extreme weather is also registering in household budgets. Nearly half of Americans, 46 percent, say that during the past year they faced unexpected utility expenses caused by storms, flooding, heat, or wildfires, statistically unchanged from 45 percent in August 2025. Thirteen percent reported unexpected homeowner’s insurance premium expenses from these causes, a significant decline from 18 percent a year earlier, while 8 percent reported unexpected health care expenses, unchanged from August 2025. Ken Winneg, APPC’s managing director of survey research, said the pattern reflects a broader transformation in how extreme heat fits into everyday life. “Extreme heat is no longer just an occasional inconvenience,” Winneg said. “It is affecting Americans’ household budgets and daily routines, from electricity bills to simply going outside.”

When asked specifically about the impact of extreme heat on their activities and lifestyle over the past year, majorities reported at least a minor effect across several domains. Eighty-two percent said extreme heat had a major or minor impact on their electricity bills, 75 percent on outdoor activities, 56 percent on exercise routines, and 56 percent on sleep. Several of these measures have climbed since August 2025: the share reporting a major or minor impact on exercise and sleep rose to 56 percent from 50 percent, and the proportion reporting effects on pets increased to 45 percent from 37 percent, all statistically significant increases. The data paint a picture of heat as a persistent, ambient stressor that shapes decisions about when to exercise, how well people sleep, and even how families care for their animals, rather than a rare emergency confined to the hottest afternoons of the season.

Despite this widespread exposure, public awareness of protective resources remains strikingly low. Sixty-five percent of Americans say they do not know the location of a cooling center they could go to in the event of extreme heat, while just 35 percent say they know where one is located. That knowledge level has shown little recent movement: 35 percent knew a cooling center location in August 2025 and 33 percent in July 2024, although the current figure is significantly higher than the 30 percent recorded in November 2023. Laura A. Gibson, an APPC research analyst, argued that the gap represents a communication failure that communities can address. “As we continue to experience extreme heat,” Gibson said, “communities need to do more to make the public, particularly vulnerable populations, aware of these cooling facilities.”

Unhealthy air quality, which is closely related to extreme heat through wildfire activity, has also become a more visible problem. During the summer of 2026, much of the nation experienced smoky and hazy conditions from wildfires. Six in 10 Americans, 60 percent, say the area where they live experienced days in the past three months when local health authorities reported that the air quality was unhealthy, up significantly from 48 percent in August 2025. Another 24 percent said their area did not experience such days, and 16 percent were unsure. The American Lung Association’s “State of the Air” 2026 report found that 44 percent of Americans live in areas earning failing grades for unhealthy levels of ozone or particle pollution, providing an independent corroboration of the public’s reported experience.

People who reported unhealthy air in their area took a variety of protective measures, several of which have become more common over time. Eighty-two percent said they responded to local authorities’ air-quality warnings by staying indoors more than they typically would, up from 76 percent in August 2025 and 74 percent in August 2023. Fifty-one percent closed their windows, compared with 45 percent in August 2025 and 48 percent in August 2023. Forty-eight percent turned on the air conditioning, statistically unchanged from 47 percent in August 2025 but significantly higher than 37 percent in August 2023. Twenty-two percent used a room-air purifier, compared with 19 percent in August 2025 and 17 percent in August 2023, and 12 percent wore a KN95 or N95 mask outdoors, up significantly from 7 percent in August 2025 and statistically similar to 9 percent in August 2023.

Looking ahead, a majority of Americans expect the dangers of extreme heat to intensify. Nearly six in 10, 59 percent, say people in their community will be more likely to experience heat stroke caused by extreme heat waves in the next 10 years. Twenty-nine percent said people will be about as likely to experience it, 4 percent said less likely, and 8 percent were unsure. That expectation is essentially unchanged from August 2025, when 59 percent anticipated greater risk, and July 2024, when 58 percent did, but it remains significantly higher than the 52 percent recorded in November 2023. The consistency of this outlook across three annual survey waves indicates that anticipation of worsening heat risk has become a settled feature of public opinion rather than a reaction to any single summer.

Knowledge of the specific symptoms of heat-related illness, however, remains uneven, and the survey identified notable gaps in health literacy. In August 2026, 88 percent of Americans correctly identified dizziness as a sign of heat-related illness, 83 percent identified nausea, and 72 percent identified hot, red, dry, or damp skin. But only 47 percent identified cold, pale, and clammy skin as a symptom, even though that presentation is a recognized warning sign. Just 5 percent incorrectly identified hunger as a symptom. “Most Americans recognize that climate change is increasing the risk of heat-related and other illnesses, but our findings show that recognizing the risk doesn’t always translate into knowing the signs of heat-related illness,” Winneg said. “That knowledge can be especially important as extreme heat becomes an increasingly common part of Americans’ lives.”

Two further knowledge gaps stand out in the data. Only 32 percent of Americans know that pregnant people exposed to extreme heat are more likely to deliver their babies early than pregnant people who are not exposed. Nearly half, 49 percent, said they were not sure, 17 percent incorrectly said exposed pregnant people are just as likely to deliver early, and 3 percent said they are less likely to do so. That level of knowledge has not changed significantly from August 2025, when 33 percent knew the fact, or July 2024, when 30 percent did, although it is significantly higher than the 24 percent recorded in November 2023. Meanwhile, most Americans do correctly identify who is most vulnerable to fatal heat: 69 percent said heat-related deaths are most common among adults ages 65 and older, while 8 percent said children, 2 percent said adults ages 21 to 40, and 4 percent said adults ages 41 to 64, with 16 percent unsure. That figure is unchanged from August 2025 but significantly higher than the 62 percent recorded in August 2022.

Taken together, the survey results suggest a public that has absorbed the reality of a hotter, smokier, more disruptive climate into its everyday routines and expectations, even as critical gaps persist in knowledge about protective resources and medical warning signs. The APPC’s Annenberg Science and Public Health survey panel has been tracking American public knowledge, beliefs, and behaviors regarding vaccination, Covid-19, flu, RSV, climate, and other consequential health issues, providing one of the longest-running longitudinal windows into how health perceptions evolve alongside environmental change. In addition to Gibson and Winneg, the ASAPH survey team includes Patrick E. Jamieson, director of the Annenberg Health and Risk Communication Institute, which oversees the survey; research analyst Shawn Patterson Jr.; and Kathleen Hall Jamieson, APPC’s director emerita. As records continue to fall and heat becomes a structural feature of American life, the survey’s authors suggest, closing the gap between risk awareness and practical preparedness will be one of the most consequential public health communication challenges of the coming decade.

Subject of Research: Public perceptions of climate change's health effects during the hottest U.S. summer on record

Article Title: In hottest summer on record, 2 in 3 Americans say climate change is increasing heat-related illnesses

Article References: In hottest summer on record, 2 in 3 Americans say climate change is increasing heat-related illnesses. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: extreme heat, climate change, heat-related illness, Annenberg Public Policy Center, ASAPH survey, air quality, wildfire smoke, cooling centers, heat stroke, public health, NOAA, household costs

The study, led by environmental epidemiologist Amruta Nori-Sarma of Harvard T.H. Chan School of Public Health in collaboration with colleagues at Truveta, Harvard, and Boston University, exploited a technological capability that earlier generations of heat researchers lacked: continuously refreshed electronic health record data. Rather than waiting months for claims data to be processed and aggregated, the team drew on state-day counts of emergency department visits from 19 eastern states, allowing them to quantify the health burden of the summer 2025 heatwaves while the season was still underway. In total, the analysis encompassed 8,169,637 emergency department visits recorded during the warm seasons of 2023 through 2025, providing a robust historical baseline against which the 2025 episodes could be compared.

The two heatwaves under scrutiny were stark in their timing and severity. The first gripped the region from 22 to 25 June 2025, and the second returned from 10 to 13 August 2025, engulfing the eastern United States in conditions that triggered National Weather Service heat alerts across much of the study area. To estimate how many visits these episodes caused, the researchers compared observed visit counts during the heatwave windows with counterfactual predictions of what visits would have been under typical temperature conditions, using temperature-health associations estimated from the prior three warm seasons.

Technically, the analysis rested on a conditional Poisson model, a statistical framework well suited to time-series data on disease counts. The researchers stratified time by year, calendar month, and day of week, with stratum-specific fixed effects that absorb routine patterns in healthcare utilization, such as weekday and seasonal variation. This design effectively compares hot days with cooler days occurring under otherwise similar conditions, a strategy closely related to the time-stratified case-crossover approach widely used in environmental epidemiology. Temperature exposure was modeled using distributed lag non-linear models, or DLNMs, which capture two crucial features of heat’s health effects simultaneously: the non-linear dose-response relationship between temperature and risk, and the fact that effects unfold over multiple days, with heat stress on one day influencing emergency visits over a window of zero to four days afterward.

The headline numbers were striking. During the June 2025 heatwave, the researchers estimated that 9.2 percent of all-cause emergency department visits were attributable to heat over the zero-to-four-day lag window, with a 95 percent confidence interval of 6.2 to 11.6 percent. During the August heatwave, the attributable fraction was 8.3 percent, with a confidence interval of 6.0 to 10.1 percent. In plain terms, roughly one in every eleven or twelve people who walked into an emergency department in these nineteen states during those weeks was there, at least in part, because of extreme heat. Similar patterns emerged when the team examined cumulative lags and cause-specific outcomes, indicating that the association was not an artifact of a single modeling choice.

Because the underlying data included diagnostic information, the researchers could decompose the burden by cause. Beyond direct heat-related illness diagnoses, they tracked emergency visits for kidney disease and for mental health conditions, both of which have well-documented physiological links to heat exposure. Kidney disease is acutely sensitive to dehydration and thermal strain, while a growing body of literature connects high ambient temperatures to psychiatric crises, including exacerbations of mood disorders and substance-related emergencies. The lag-specific analyses showed that the association between the 99th percentile of daily maximum temperature, about 36.9 degrees Celsius, and the sample median of 27 degrees Celsius was strongest on the same day for direct heat illness, while kidney and mental health outcomes followed somewhat different lag structures, consistent with the diverse physiological pathways through which heat injures the human body.

Those pathways are worth spelling out. Extreme heat forces the cardiovascular system to work harder, shunting blood toward the skin to dissipate warmth and increasing cardiac output, changes that laboratory studies involving more than 400 controlled heat exposure experiments have documented in detail. In people with preexisting heart disease, this added strain can precipitate decompensation. Dehydration concentrates the blood and promotes the formation of kidney stones and acute kidney injury, particularly in older adults and in people taking common medications that impair thermoregulation or fluid balance. Meanwhile, heat disrupts sleep, alters neurotransmitter function, and can increase impulsivity and aggression, mechanisms that plausibly underlie the observed rise in mental health emergency visits during hot weather.

The heterogeneity analyses added an important dimension to the findings. By fitting subgroup models for six age groups, three US census regions, and both sexes, the researchers probed whether the temperature-emergency visit association varied across populations. The results, visualized in forest plots comparing rate ratios at lag zero, showed differences by age, region, and sex, echoing decades of evidence that the very young, older adults, and residents of areas unaccustomed to extreme heat bear disproportionate risk. The state-specific exposure-response functions also revealed geographic variation: states with historically milder summers tended to show steeper increases in emergency visits per degree of warming, a pattern consistent with the idea that populations adapt, physiologically and infrastructurally, to the temperatures they usually experience, and that anomalous heat is most damaging where it is least familiar.

Methodological sensitivity checks strengthened the study’s credibility. The team replicated the primary analysis using daily average temperature instead of daily maximum temperature, and separately extended the lag window from four to seven days; both variations reproduced the central findings. Exposure data were drawn from the Open-Meteo weather API and National Weather Service records, and heat alert dates by state were compiled from National Weather Service advisories, allowing the investigators to anchor their heatwave definitions in the same official warnings that reached the public during those weeks. All analytic code, including the data extraction scripts, DLNM fitting routines, meta-analysis, and attributable burden estimation, has been made publicly available on GitHub, an unusual and welcome degree of transparency for a rapidly produced surveillance analysis.

The broader significance of the study lies less in any single percentage than in what it demonstrates about the future of climate-health surveillance. Traditional epidemiology delivers its verdicts long after the disaster has passed, when the findings can inform the next heat season but not the current one. By contrast, a near-real-time pipeline built on continuously refreshed electronic health records can tell public health officials, while a heatwave is still unfolding, how many excess patients are arriving, which conditions are driving the surge, and where resources are most strained. The authors argue that this capability should become a standing component of heat preparedness, complementing heat action plans and warning systems whose effectiveness, demonstrated in cities from Philadelphia to Montreal, depends on knowing when and where the danger peaks. As climate change renders summers like 2025 more frequent and more intense, the study suggests that the emergency department itself, properly instrumented, can serve as an early-warning sensor for the health impacts of a warming world, and that the true toll of extreme heat is far larger than the narrow category of heatstroke diagnoses would suggest. Nearly a tenth of all emergency care during those scorching weeks was heat’s shadow, and counting it in real time may be the first step toward preventing it.

Subject of Research: Attribution of summer 2025 US heatwave emergency department visits using electronic health records

Article Title: Impact of the summer 2025 heatwaves on emergency department visits in the USA

Article References: Nori-Sarma, A., Cartwright, B. M., Zanobetti, A., Pastwa, A., Stucky, N., & Willis, M. D. (2026). Impact of the summer 2025 heatwaves on emergency department visits in the USA. Nature Health. https://doi.org/10.1038/s44360-026-00194-y

Image Credits: AI Generated

DOI: 10.1038/s44360-026-00194-y

Keywords: heatwaves, emergency department visits, electronic health records, extreme heat, public health surveillance, climate change, epidemiology, distributed lag non-linear models, heat-related illness, kidney disease, mental health, United States