Is Public Health Ready for the Deadliest Weather Threat in America?
Extreme heat is the leading weather-related cause of death in the United States. It kills more people most years than hurricanes, floods, and tornadoes combined. According to the Centers for Disease Control and Prevention, heat claims roughly 2,000 lives annually, and that number is almost certainly an undercount.
Heat-related illness is frequently underdiagnosed, and official tallies often miss deaths where heat was a contributing factor rather than the listed cause. Part of what makes accurate counting so difficult is that there has never been a standardized national definition for heat-related mortality. Without consistent case definitions, every jurisdiction counts these deaths differently, making it nearly impossible to build a reliable national picture of the true toll.
State vital statistics and death certificate data are essential for accurately counting heat-related mortality; however, these data often undercount heat impacts unless medical certifiers explicitly document heat as a contributing factor. Some jurisdictions are beginning to address this gap through practical interventions, including alerts to clinicians during extreme heat events, prompts in vital records systems reminding medical certifiers to note when heat contributed to a death, standardized coding guidance from the Environmental Protection Agency, and integration with real-time surveillance dashboards. Ongoing efforts to enhance training for medical certifiers, expand data linkages and improve real-time monitoring are critical to more accurately capturing the true burden of heat-related deaths.
Public concern is growing alongside the risk. A 2024 Yale survey found that 63 percent of Americans believe people in the United States will be harmed by global warming, with extreme heat ranking among their top concerns. That worry is grounded in reality. The question is whether public health systems are equipped to respond when a heat emergency unfolds.
Most are not, at least not in the way the threat demands.
When a heat wave strikes, public health agencies typically lack the interoperable data infrastructure to quickly identify who is being affected, where, and how severely. Emergency department visits rise. Hospitalizations climb. Vulnerable populations bear the heaviest burden: older adults, people with chronic conditions, outdoor workers, and low-income communities without reliable access to air conditioning. The data systems that could connect those emergency department visits to heat exposure, flag geographic concentrations of risk, and trigger a coordinated response are not built to do that work in real time in most jurisdictions. This is not a knowledge problem. It is an infrastructure problem.
The consequences of that gap are not hypothetical. They play out every summer across communities that lack the tools to see what is happening until after it has already happened.
Public health has demonstrated what is possible when the infrastructure exists. When wildfires destroyed much of Lahaina in August 2023 and thousands of people were displaced, the Hawai'i Department of Health ran daily syndromic surveillance reports to track emergency department and urgent care utilization across the island in near real time. Staff on Oahu were able to support the Maui team remotely, distinguishing acute injury visits from chronic disease management needs and directing resources accordingly. The response worked because the data infrastructure was already in place. That kind of situational awareness, geographically specific, timely, and actionable, is precisely what an extreme heat response requires. Hawaii's legislature, recognizing the value of that infrastructure, has since moved to codify and expand the state's syndromic surveillance authority.
The tools that would make heat surveillance possible already being applied to other public health threats. Oregon has used syndromic surveillance linked to near real-time emergency department data to identify and investigate pesticide exposure cases, an environmental health problem with no single laboratory test and no straightforward reporting pathway. Minnesota has built syndromic surveillance infrastructure that now supports stroke reporting, traumatic brain injury tracking, and poison center data, all flowing through a unified data connection that reduces the burden on health systems and keeps information moving to public health partners. Dallas County built enterprise-level surveillance infrastructure specifically capable of neighborhood-level visibility to identify at-risk populations and inform resource allocation during public health events. Each of these represents a building block for heat surveillance. The architecture is there. The next step is pointing these best practices and tools at this problem consistently and at scale.
The urgency is compounded by the current funding environment. The data modernization progress of recent years is under serious pressure. Federal funding cuts in 2025 have forced health departments across the country to suspend surveillance programs, lay off epidemiologists and informatics staff, and halt system upgrades mid-implementation. Agencies already working with constrained resources are being asked to do more with significantly less. That context makes intentional prioritization more important, not less. The systems being built now need to be durable, multifunctional, and capable of serving multiple health priorities rather than single-disease solutions that disappear when a crisis fades from public attention.
Funding cuts have hit hard, but training and community-level action have continued to gain ground. The American Public Health Association (APHA), ecoAmerica, NACHC (National Association of Community Health Centers), and the National Network of Public Health Institutes (NNPHI) recently partnered on a live training on public health actions for extreme heat protections, reaching public health professionals across the country on Global Heat Action Day. A new Train-the-Trainer model from APHA and Climate for Health is now available, providing a free, CE-accredited course that equips practitioners and community leaders with tools to prevent heat-related illness and bring that knowledge directly into their communities. The Alliance for Heat Resilience and Health, of which APHA is a convening partner, launched a Heat Safety Awareness Toolkit this spring, organized around three levels of engagement: spreading awareness, working with local leaders to issue official recognition, and advancing policy protections at the state and community level. These efforts are reaching people who show up, who seek out training, who engage with health departments, who know to look for resources. Data systems reach everyone else, including people who will not make it to a clinic or a cooling center until it is too late.
Closing the gap between extreme heat events and public health data response is a readiness problem, and it is one the informatics community is positioned to help solve. Progress is already underway. At the Council of State and Territorial Epidemiologists (CSTE) Annual Conference this June, CSTE members and CDC worked toward a position statement on heat-related mortality case definitions, an effort years in the making. When finalized, it will give every jurisdiction in the country a shared, standardized way to count heat deaths consistently, the foundational step that makes everything else, better surveillance, smarter resource allocation, more targeted intervention, possible. It is the kind of unglamorous consensus work that holds the public health data system together.
JPHIT members bring the cross-sector relationships, the technical expertise, and the policy reach to advance this work. That means advocating for heat as a recognized priority within public health data systems, supporting agencies in building interoperable infrastructure that can serve multiple conditions and threats, and making clear to policymakers that data modernization is not an abstraction. It is what stands between a community and a preventable death on a summer afternoon.
Additional Resources
Public health agencies and community partners are actively working to monitor, prevent, and respond to heat-related illness and deaths. In Puerto Rico, the Puerto Rico Vital Records Office participates in several related efforts, including providing death reports to the Puerto Rico Department of Health’s Heat-Related Illnesses Surveillance Team and participating in the Puerto Rico Heat Community of Practice.
For readers interested in learning more, the following public resources offer additional data, guidance, and examples of heat surveillance efforts:
Puerto Rico resources
Sistema de vigilancia sindrómica: Enfermedades relacionadas al calor
Puerto Rico fortalece esfuerzos para enfrentar el calor extremo | Metro Puerto Rico
Public health guidance and examples from other jurisdictions