Extreme Heat Undermines Safe Water Access, Even in Wealthy Cities

As climate change accelerates, urban centers in the Global North — encompassing regions such as North America and Europe — face an unprecedented challenge: adapting to soaring temperatures exacerbated by frequent heatwaves. Beyond the well-publicized need for cooling systems, a less heralded yet critical resource in this adaptation battle is water security. Recent research led by experts at the Universitat Oberta de Catalunya (UOC) has uncovered the vital role safe and accessible water plays in protecting urban populations, especially vulnerable groups, from the increasing onslaught of extreme heat.

In many developed cities, access to clean and affordable water is often assumed to be an unproblematic given. However, the reality on the ground presents a starkly different picture. This discrepancy arises partly because water is not merely a consumable resource in these communities but is increasingly becoming the primary means of natural “air conditioning” for individuals and households unable to reliably use electrical cooling devices. As energy poverty affects a growing number of families, water’s function transitions from basic hydration to a crucial physiologic cooling agent.

Hug March, principal investigator of the study and joint head of the TURBA Lab at UOC, emphasizes water’s multifaceted role in thermal regulation for the body. When conventional air conditioning is unaffordable or unavailable, the ability to shower, access public fountains, or swim can drastically reduce physiological heat stress. This adaptive mechanism, however, hinges on the assumption of continuous and equitable water availability, something not guaranteed even in wealthy urban centers.

The research identifies a growing phenomenon termed “systemic cooling poverty,” wherein low-income households, often composed of marginalized communities, elderly individuals, or persons with chronic diseases, bear a disproportionate share of heat-related risks. These groups frequently face household water insecurity, creating an uneven landscape of heat resilience across cities. Vulnerabilities multifold: financial constraints force these populations to ration water use, thereby limiting their capacity to employ water as a cooling resource during intense heat spells.

Extreme heat events have shifted from occasional anomalies to persistent conditions, demanding sustained adaptation strategies. Urban heat islands compound the challenges faced by city dwellers, concentrating heat risks in densely populated neighborhoods that often coincide with socioeconomically disadvantaged populations. In southern European cities such as Barcelona, the reliance on water-based cooling practices—like using public swimming pools or fountains—has become essential survival strategies. Yet, financial pressures create paradoxical situations where residents prioritize water conservation to curb bills, undermining their ability to mitigate heat effects.

The escalation of water and sewerage fees in cities such as Portland, USA—projected to reach nearly $2,400 by 2030—exemplifies the growing economic barriers to water security. These cost increases threaten to widen health disparities, reinforcing existing social and spatial inequalities. When water becomes unaffordable, vulnerable communities confront compounded risks of heat exposure, dehydration, and associated health consequences, forming a dire feedback loop of environmental and economic injustice.

To confront these interlinked crises, the research team advocates for a transformative policy framework centered on “heat justice” — a paradigm that prioritizes water security as foundational to climate adaptation efforts. Such an agenda must incorporate comprehensive data collection and inclusive policy designs that ensure water systems are not only reliable but accessible to the most at-risk urban populations. Crucially, this involves safeguarding household water security, which has been traditionally overlooked in urban climate resilience planning.

Water scarcity driven by increasing drought frequency is further pushing cities toward alternative water sourcing methods, such as desalination. While these technologies promise supply augmentation, they also introduce elevated operational costs, which, if not carefully managed through socio-environmentally just policies, risk exacerbating water insecurity for the poor. Thus, costs and access must be balanced to avoid perpetuating inequalities under the guise of technological progress.

Ultimately, the research underscores that water security is not just an infrastructural or environmental issue but a linchpin of social equity in the age of climate emergency. Without guaranteeing safe, affordable, and dependable water access, measures to adapt urban centres to chronic and acute heat are fundamentally undermined. The widening gaps in heat resilience mirror and deepen divisions across socioeconomic lines, emphasizing the need for holistic, justice-oriented approaches to climate adaptation.

This pioneering study, published in the journal npj Urban Sustainability under an open-access license, contributes significantly to climate resilience discourse. It aligns with planetary health and sustainability goals targeting water security and livable cities, reinforcing the urgency of integrating social dimensions into climate action plans. Funded by ICREA and UKRI Horizon Europe Guarantee, it spotlights how seemingly mundane resources like household water can determine survival during climate crises.

By centering water security within heat adaptation strategies, urban planners and policymakers have a powerful tool to mitigate not only heat-related health risks but also underlying inequities. As cities worldwide grapple with the dual challenges of warming climates and escalating resource competition, the nexus of water access and thermal comfort demands urgent attention. Adopting a heat justice framework grounded in equitable water provision might well be the defining climate resilience strategy for the decades ahead.

News Publication Date: 20-Jan-2026

Web References:
Journal Link

References:
March, H., Meehan, K., Domene, E., Satorras, M., & Saurí, D. (2026). Why water security matters to cities under extreme heat in the Global North. npj Urban Sustainability. https://doi.org/10.1038/s42949-025-00317-6