Climate and health governance: Opportunities and challenges addressing extreme heat in the United States

Abstract

The increasing frequency and severity of extreme heat events is an intersectional issue that poses significant risk to human health and livelihood. This article examines the challenges and opportunities of addressing the health consequences of extreme heat events in the United States. American federalism and political polarization constrain innovation and hamper the development and implementation of solutions to mitigate negative health consequences of extreme heat. The United States is unprepared for the health consequences of extreme heat events. Fragmentation of the medicolegal death investigation system contributes to an underreporting of heat-related mortality in federal repositories. Without reliable data, the scope of heat-related mortality cannot be fully understood and this limits the ability to effectively intervene. Despite this gap in our knowledge, it is clear that there are profound socioeconomic and racial disparities in health, and extreme heat events will amplify these disparities. We consider opportunities for local government action in this area, yet, federal leadership is required to bolster national efforts in addressing extreme heat.

1. Introduction

Extreme heat results in higher rates of human mortality than any other severe weather event [1,2]. Globally, prior heatwaves have ravaged vulnerable and underprepared communities across all latitudes, killing thousands over relatively short periods of time [3,4]. In 2023 alone, heat-related mortality in the US exceeded 2,300 deaths with correspondingly high heat-related emergency room visits [5], [6]. Communities across the US will continue to experience record-breaking temperatures [7,8] as extreme heat events (EHEs) increase in frequency, severity and duration in our changing global climate [9]. The physiological and mental impacts of extreme heat are well documented [[10], [11], [12]], yet the relationship between EHEs and health outcomes is complex. However, increases in extreme heat will amplify existing health disparities.

Extreme heat refers to significant deviations of temperatures from regional historic averages, posing significant health risks. Thresholds for what temperatures are considered extreme varies according to regional climatology. National reports often use a threshold of 95°F to classify extreme heat, and the number of days per year surpassing 95°F has increased in recent decades for western states. A 2°C warming of global average temperatures is projected to increase the number of extreme heat days across the US, with the greatest change occurring in southern states [13]. Negative impacts of extreme heat are worse during multiday events [14]. Heatwave frequency increased from an average of two to six per year, duration of the heatwave season increased from 24 to 70 days, and intensity increased from 2.0°F to 2.5°F above the 85^th percentile of historical local temperatures [15].

Prolonged exposure to extreme heat is associated with adverse physiological and mental health effects. Extreme heat exacerbates pre-existing medical conditions, increasing the risk of illness or death from cardiovascular, renal or respiratory disease [16,17]. High temperatures are especially dangerous when combined with humid conditions as this impairs the biology of evaporative cooling [18]. Emergency room visits and hospitalizations correspondingly increase during periods of extreme heat [12,19]. Excess mortality increases during and immediately following heatwaves [10,20]. Risk of heat-related illness increases for those taking certain medications for cardiovascular disease or mental health disorders. Heat-related health impacts are greatest among children, adults over 65, individuals experiencing poverty, and racial or ethnic minorities [16].

The racial and economic gaps in climate-related health outcomes are well documented: poverty, long-term divestment in communities, legacy impacts of segregation, and structural racism leave communities of color and poor communities more vulnerable to extreme heat [[21], [22], [23], [24], [25]]. Addressing negative health consequences from extreme heat is possible, but innovative, multi-sector policy combined with adequate investment for implementation is necessary. In the US, the federal commitment to address climate change, and by extension extreme heat events, has been inconsistent [26]. Without clear federal leadership, states and localities are left to consider how best, if at all, to address the health risks of EHEs. This fragmented approach creates challenges as subnational governments may lack the funding, personnel, and collaborative capacity to address EHEs across vulnerable populations and different implementation contexts, i.e., residential, occupational, and educational. But federalism can also spur innovation, as subnational governments may be best suited to develop successful climate solutions tailored to local behavior. Effective mitigation for at-risk communities requires understanding and targeting factors influencing the deeply rooted inequities that contribute to unequal health outcomes.

In this article, we examine the challenges and opportunities of addressing EHEs in the US. We consider the impact of federalism, fragmentation, and political polarization on addressing EHEs. Climate change and EHEs are part of a complex set of determinants of health outcomes, and this complexity creates decision-making challenges. Effective, evidence-based policy must be based on reliable and valid evidence on dimensions of the problem, yet fragmentation and inconsistent data reporting create challenges to understanding heat-related mortality. Policies and programs are more likely to be successful when they are developed with a clear understanding of the problem, including its causes and consequences. Socioeconomic, behavioral, and clinical factors all matter in shaping heat-related health outcomes. Existing health disparities combined with a range of different heat exposure profiles create challenges in developing effective interventions. Despite these challenges, we highlight possible opportunities to innovate and address EHEs. Some states and localities have developed heat action plans (HAPs), which could offer an opportunity to build local capacity to address extreme heat. Along with this, we consider the role of local health departments. While many local health departments are still rebuilding post-COVID, these long-standing institutions may be in a position to innovate and mitigate heat mortality and morbidity.

2. Decision making in the United States: federalism, devolution & climate-health governance

Divided authority and fragmentation are the norm for climate and health policy in the United States. American federalism results in federal and state governments having some level of authority over environmental/climate and health policy. This, combined with the formal separation of powers between executive, legislative, and judicial branches of government at both state and federal levels, creates a complex institutional tapestry for policy adoption and implementation. This multi-level, overlapping institutional arrangement provides citizens (or organized interest groups) with ample opportunity to access decision-making processes. However, the complexity of the system can be daunting, and organized interests (for or against any issue) tend to be more equipped to successfully navigate this system. They have experience accessing multiple decision-making venues across levels of government to pursue their goals. This porous system often results in gridlock and conflict [27,28].

At the federal level, responsibility for understanding, documenting, and responding to EHEs is spread across federal agencies. All fifty states and thousands of local governments (regional entities, counties, metros, cities, townships and other units of government) also have some measure of responsibility in reacting to and mitigating the negative health consequences of EHEs. When problems cross political boundaries, like climate change and the health consequences of EHEs, the role of the federal government is often focused on harmonization and coordination between states and regions. Federal action on climate change has been inconsistent at best, resulting in a patchwork of multi-sector initiatives from state and local governments, leaving the US underprepared for EHEs [29,30].

Given the second Trump administration’s deprioritization of actions to address the impacts of climate change, state and local government capacity and leadership are critical. Yet, across the country, political polarization limits opportunities to innovatively address climate change, extreme heat and health. Public opinion data indicate that a majority of American voters support government action to address climate change [31], however, Republican controlled states have used and continue to threaten the power of preemption to restrict local government climate action [32].

3. National action

At the national level, there have been limited efforts to use federal power to provide coordinated regional responses to heat. Under the Biden administration, the federal government launched the National Integrated Heat Health Information System (NIHHIS), a broad collaboration of federal agencies and partner organizations. The goal of this initiative was to improve our understanding of extreme heat and develop effective interventions to mitigate the negative consequences of heat risks. The NIHHIS developed a National Heat Strategy for 2024-2030, providing recommendations to reduce heat-related health impacts. This integrated information system approach coordinates communication across multiple federal agencies to provide state and local governments a necessary framework for the creation and implementation of regional HAPs that seek to foster engagement and address the inequitable impact of extreme heat on disadvantaged communities 33. Bolstering community-level resilience requires advancing our current knowledge as to how heat impacts health at the community level. It is relatively unknown to what extent local health departments implement HAPs, or how well existing HAPs approach the multifaceted issue of heat-related mortality.

The early months of the second Trump administration have ushered in unprecedented changes to federal agencies under executive authority. These broad changes include substantial reductions in budgets and workforce, with a concerted effort to shift the focus away from climate change, including the negative consequences of more frequent and intense heat events. These actions have added additional uncertainty and complications to the implementation of regional HAPs.

4. Heat action plans

Heat-related mortality is complex. While EHEs impact an entire community, the health consequences of EHEs are uneven and intertwined with broader, often overlapping forces shaping health. EHEs disproportionately impact poor and historically vulnerable communities [34]. HAPs are policy tools that can assist action coordination across multiple organizations with the goal of reducing the impacts of extreme temperatures and promoting community resiliency. HAPs may include details regarding surveillance, risk communication, health care, energy assistance programs, cooling centers and heat alert systems [30].

Current recommendations for HAP development are reactive by design, treating heat as an emergency rather than focusing on long-term efforts to reduce disproportionate heat exposure [34]. For example, heat warning systems are a common component of HAPs. These often rely on National Weather Service (NWS) extreme heat advisories for plan activation and, subsequently, the opening of cooling centers [30]. Heat advisories and excessive heat warnings require sustained heat index above a certain threshold (often 104°F) for multiple days, though this may be detrimental considering a significant portion of heat-related mortality occurs during periods for which excessive heat advisories were not issued [34,35].

5. Role of local health departments

Local health departments (LHDs) are an integral component of public health infrastructure in the US, coordinating with local, state, and federal agencies to provide a breadth of services to their communities and advance the nation’s health. Health departments are largely responsible for creating systemic changes through policy implementation to address chronic conditions, promote healthy environments, combat the adverse impacts of climate change, and address health inequities and the social determinants of health (SDOH) [36]. The network of 2,500 agencies that constitute the LHD network within the US allows for collaboration with community leaders to improve health outcomes within a regional context, an important component considering the disparate impacts of climate change. However, a majority of LHDs feel ill-equipped to handle climate change mitigation efforts and responses [37,38].

In a survey of 985 LHDs, only 33 % of LHDs reported they were well prepared to handle extreme heat events, while 52 % expressed high levels of concern regarding extreme temperatures. More than half of LHDs reported no activities towards climate change preparedness, and only 25 % dedicated at least one employee towards full-time preparedness efforts, the latter of which predominantly occurred in large metropolitan areas. Only one in three LHDs was aware of the National Health Security Strategy, a document providing approaches to prepare for and respond to public health emergencies and disasters [38,39]. This puts LHDs in a difficult position. They are responsible for developing HAPs and monitoring heat-related mortality, yet may lack the necessary resources, leaving them unable to allocate time towards mitigation efforts.

Inadequate preparedness of LHDs is primarily attributed to administrative barriers, such as limited resources or data availability. Indeed, nearly half of LHDs lacked sufficient data for studying 10-year trends of heat-related mortality [37], hindering their knowledge regarding the potential severity of heat-related mortality while limiting their ability to observe the effectiveness of any policy implementations. This may contribute to an unintended consequence wherein poor data availability undermines the perceived severity of heat-related mortality. This, in turn, may limit the resources LHDs are willing to allocate towards monitoring, preparedness or mitigation of heat-related mortality. The issue becomes cyclical in the absence of external factors that can assist already resource-limited health departments.

6. Fragmented reporting of heat-related mortality

Federal repositories that document heat-related mortality rely on death certificate data listing heat as a primary or contributing factor. Inadequate and inconsistent documentation of heat-related mortality results in underreporting and measurement error. The current medicolegal death investigation system consists of over 2,000 medical examiner or coroner offices under state or local jurisdiction; there is currently no single federal agency providing standardized oversight for this system [40,41]. Sixteen states have centralized medical examiner systems, with the remainder comprised of decentralized city, county, district, or regional-based medicolegal systems. Federal accreditation or certification for death investigators is voluntary, and only 17 % of death investigation offices were accredited in 2018 [42]. Resource limitations may prevent coroner office accreditation, especially in rural areas. This contributes to the fractured design and implementation of investigation reporting standards.

Cause of death is determined using the death investigator’s best judgment [43], yet qualification requirements vary depending on regional jurisdiction. Coroners may be elected laypersons, such as sheriffs, prosecutors, or funeral directors. These medicolegal systems are prone to deficiencies in medical knowledge and competency, conflicts of interest, and may lack the resources or skills necessary for forensic autopsies. Investigation standards of coroner systems tend to be incremental responses to inadequacies rather than planned systems utilizing medical knowledge and may place less focus on bolstering reporting requirements. Medical examiners are appointed, requiring board certification in a medical field. State examiner systems can increase surveillance uniformity and quality of death investigations as services become independent of population size and variations in county budgets [44]. However, numerous medicolegal death investigation offices experience funding deficiencies, forensic pathologist shortages, and outdated equipment stock [40,45]. Regional shortcomings in surveillance aggregate to the federal level when reported in national repositories, ultimately contributing to the underestimation of heat-related mortality.

The divergence of heat-related mortality estimates between official reports and independent researchers illustrates this measurement challenge. For instance, the Centers for Disease Control and Prevention (CDC) and the NNWS reported 1,153 and 350 heat-related deaths occurred in 2020, respectively [46,47]. Better estimates may be obtained by using excess deaths during and after heat events [48], with studies conducted in smaller study areas providing values exceeding national reports. From 1997 to 2006, approximately 5,608 excess deaths per year were attributable to heat events across 297 counties [20], while a similar study estimated 4,819 excess deaths related to heat events between 1987 and 2000 in 106 U.S. cities [49]. But the methodological approach does not substitute for improved public health surveillance data.

Without reliable and valid data documenting heat-related mortality, practitioners and researchers are constrained in understanding the full scope of the problem. This hinders developing targeted evidence-based policy on heat mortality, and importantly, also limits the ability to evaluate the effectiveness of interventions. Systematic underreporting in a fragmented system creates challenges to understanding how policies and programs may reduce heat-related mortality. Lack of intervention will further the disparate impacts of extreme heat burdening vulnerable communities.

7. Socioeconomic and racial disparities in health & heat

Persistent poverty, economic inequality, and structural racism profoundly shape health outcomes in the US. The wealth-health gradient highlights the power of material resources in shaping well-being. Poverty, and particularly childhood poverty, can underpin health disparities such as poor quality housing, under-resourced neighborhoods, failing schools, community blight, and a range of other determinants of health overlap.

Historically marginalized groups experiencing systemic inequality are more vulnerable to the health-damaging impacts of climate change [50,51]. Causal factors contributing to heat vulnerability are multifaceted, interrelated and rooted in the SDOH. Systemic underinvestment results in disenfranchised communities that simultaneously face increased vulnerability to EHEs while lacking the resources necessary to bolster coping and adaptive capacities. These effects disproportionately impact communities of color in urban and rural settings.

Many marginalized communities still experience discriminatory practices that deepen vulnerability and contribute to adverse health outcomes during EHEs. In the US, African American and Hispanic populations constitute a disproportionate percentage of low-income tax brackets [52]. Previously redlined communities in urban areas remain segregated as decades of disinvestment have limited socioeconomic mobility. Limited greenspace and the impact of the urban heat island effect result in these neighborhoods being 2.6°C warmer on average [53]. Aging housing stock, access to air conditioning and other housing-related determinants may lead to higher indoor air temperatures during heat events [54,55]. Intentional placement of highways and industrial or hazardous waste facilities near marginalized communities increases exposure to harmful pollutants, such as PM_2.5 or NO₂ [[56], [57], [58]].

Compounding factors of adverse SDOH and systemic discrimination contribute to worse health outcomes experienced by marginalized groups during EHEs. Rates of cardiovascular, respiratory and renal diseases are greater among marginalized groups and may be exacerbated by exposure to extreme heat [59]. Implicit bias of an individual’s perceived race increases barriers to care and leads to differential treatment in clinical settings; African Americans experience longer treatment wait times, triage acuity times, hospital bed stays and lower admission rates [59]. Underfunded hospitals lacking necessary facilities to handle patient surge during EHEs may quickly reach capacity and turn away individuals seeking care for heat-related illness. The impact of these confluent factors is evident in the rates of heat-related mortality experienced by minority groups. For instance, during the 1995 Chicago heatwave, heat-related mortality rates in impoverished, predominantly black communities were twice that of more affluent areas [60]. Similar results were reported for New York City, wherein African Americans had greater all-cause mortality rates during heat events and were twice as likely to suffer heat-related morbidity and mortality during the warm season [61,62]. Across an additional four U.S. cities, people of color were found to be 5.3 % more likely to face heat-related mortality [63]. This list is not extensive yet begins to highlight the unequal impact faced by disadvantaged communities lacking the financial means to simply survive during extreme heat events.

8. Occupational hazards

Extreme heat poses further concern for occupational safety. Official counts show that heat-related workplace deaths exceeded 436 between 2011 and 2021 [64]. However, it is possible that official estimates do not accurately portray the scope of the issue. Minority populations, noncitizen immigrants, and individuals with limited education are disproportionately employed in occupations facing climate-related risks [65]. The lowest wage earners experience heat-related injuries at a rate five times that of high-income earners. Outdoor occupations, such as agriculture and construction, constitute a large majority of workplace heat-related fatalities; one-third of these deaths are comprised of Latino workers. Undocumented immigrants constitute approximately 45 % of farm workers, an occupation with heat-related mortality rates 35 times higher than other industries [66,67]. Indoor workers, such as those in manufacturing or warehouses, are similarly at risk for heat-related mortality [68]. This may be further impacted by aging infrastructure and poor cooling systems that are inadequately prepared for extreme heat.

The Occupational Safety and Health Administration (OSHA) lacks federal regulations that protect workers from extreme heat. Hazard-free workplaces are guaranteed under the OSH General Duty Clause, yet heat-illness precautions, such as water, access to shade and regular breaks, are not required by OSHA. Workplace heat fatalities are poorly documented as OSHA primarily relies on companies to self-report heat-related deaths. Fines may be issued after a fatality, but businesses may negotiate with OSHA officials for lower fines, providing little incentive for employers to enact worker heat protections. As of 2025, only seven states provide regulations for heat-related occupational hazards. Two states, Texas and Florida, have enacted laws that prevent local ordinances from mandating worker heat protections [69].

9. Moving forward

EHEs in the United States will continue and will likely increase in intensity, duration and frequency [70]. Federal leadership on climate change has evaporated under the second Trump Administration. Given the dire health consequences of EHEs, it is possible that federal leadership could emerge on this as an issue decoupled from climate change. Federal resources could help activate and coordinate state and local action to address extreme heat, as outlined in the National Heat Strategy. Absent federal leadership, states and localities will be responsible for mitigating the negative consequences of EHEs, including the health consequences.

State and local capacity to address EHEs varies considerably across the country. Public health surveillance data that includes valid and reliable measures of heat-related mortality remains a critical need. Without this, any interventions to address the health consequences of extreme heat will be difficult to evaluate.

Heat action plans should be considered dynamic documents to better help communities understand what works to build resiliency in the face of EHEs. Intergovernmental coordination and adequate funding are also critical components to address the health consequences of EHEs. This makes the haphazard dismantling and defunding of the federal government (and its consequences for states and localities) all the more concerning.

While the challenges are significant, they are manageable. Addressing the health consequences of EHEs is well within the capability of the public sector in the United States. Systematic and high-quality evidence on the nature of the problem (vulnerable populations and heat exposure profiles), multisector plans that activate expertise in health care, social work, community and behavioral health, landscape architecture, infrastructure, and communication, and adaptive management to ensure systematic assessment of interventions to understand what works and why.

Finally, if federal leadership and support emerged, there is an opportunity to leverage the power and creativity of local governments to innovate and find new and tailored ways to address the health consequences of EHEs.

CRediT authorship contribution statement

Noah L. Ring: Writing – review & editing, Writing – original draft, Investigation. Dorothy M. Daley: Writing – review & editing, Supervision, Investigation, Conceptualization. Nathaniel A. Brunsell: Writing – review & editing, Supervision, Conceptualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.