Science Policy
day one project

Tracking and Preventing the Health Impacts of Extreme Heat

04.05.24 | 8 min read | Text by Alistair Hayden & Nathaniel Hupert & Vivian Lam & Rebecca Morgenstern Brenner & Amie Patchen

The response to the 9/11 terrorist attacks included building from scratch a bioterrorism-monitoring system that remains a model for public health systems worldwide. Today we face a similarly galvanizing moment: weather-related hazards cause multiple times the 9/11 death toll each year, with extreme heat often termed the “top weather killer,” at 1,670 official deaths a year and 10,000 attributed via excess deaths analysis. Extreme cold and dense wildfire smoke each cause comparable numbers of deaths. By rapidly upgrading and expanding the health-tracking systems of the Centers for Disease Control (CDC), Veterans Health Administration (VHA), and Centers for Medicare and Medicaid (CMS) to improve real-time surveillance of health impacts of climate change, the U.S. can similarly meet the current moment to promote climate-conscientious care that save lives.

Challenge and Opportunity

The official death toll of extreme heat since 1979 stands at over 11,000, but the methods used to develop this count are known to underestimate the true impacts of heat waves. The undercounting of deaths related to extreme heat and other people-centered disasters — like extreme cold and smoke waves — hinders the political and public drive to address the problem and adds difficulty to declaring heat waves as disasters despite the massive loss of life. Similarly, the lack of integration of critical environmental data like “wet bulb” temperature alongside these health impacts in electronic data systems hinders the provision of medical care.

National Accounting

The national reaction to the 9/11 terrorist attacks provides a roadmap forward: improved data and tracking is fundamental to a nation’s evidence-based threat response. Operated by federal, state, and local public health professionals who comprise the CDC’s National Syndromic Surveillance Program (NSSP), surveillance systems were developed across the nation to meet new challenges in disease detection and situational awareness. Since 2020, the CDC’s Data Modernization Initiative (DMI) has provided a framework for this transformation, with the stated goal of improving the nation’s ability to predict, understand, and share data on new health threats in real time. While the DMI has focused on the pioneering role of new technologies for health protection, this effort also offers a once-in-a-generation opportunity for the public health and medical surveillance establishment to increase their capacity to address pressing future threats to the nation’s welfare, including the evolving climate crisis. Increasingly, extreme weather is responsible for both near-term disasters (more frequent and intense heat waves, dense smoke waves, and cold waves) and the long-term exacerbation of prevalent health conditions (such as heart, lung, and neurological disease). Its increasingly severe  impacts demand a detailed and funded roadmap to attain the DMI’s goals of “real-time, scalable emergency response” capability. 

Patient Care

Syndromic surveillance systems track the impacts of events at a population level, but other resources are needed to directly help individual patients during a disaster. Electronic health records (EHRs) allow medical providers to track relevant information that could help diagnose arising health conditions. Some medical systems have begun tracking nonmedical information to assist in diagnosis, such as the social determinants of health (e.g., housing and food availability) that are linked to improving patient outcomes. However, the environmental conditions a patient has experienced are not typically linked to health records. Improving the links between environmental conditions and EHRs will help patients—for example, by determining if a new asthma diagnosis is related to recent smoke waves—and also support syndromic surveillance.

A similar effect occurs with death records. Death records are typically logged at the patient level with free-form text that is mostly up to a medical professional who is often under time pressure. Text for each death record is later coded to fit into specific cause codes as it is aggregated into population-level datasets such as the National Vital Statistics System. Information about the environmental conditions that contributed to the death can be lost at any step along the process, resulting in the undercount of climate-related mortality. Improved tracking at the individual level will improve accounting at the national level.

Plan of Action

In order to track the health impacts from extreme weather events and thereby enhance the provision of medical care during such events, both disaster and health data must be improved.

Recommendation 1. National accounting for health impacts of the climate crisis

The National Syndromic Surveillance Program provides a world-class starting point for better tracking of climate health impacts, both in terms of technology and a dedicated and knowledgeable workforce.  The following plan will permit the evolution of this underlying infrastructure to provide health systems and policy makers with real-time and forecast impacts.

To modernize real-time monitoring of health impacts:

To improve forecasting capabilities of health impacts:

To improve the ability to track health impacts:

Recommendation 2. Improving Patient Care

To integrate environmental conditions into EHRs nationwide:

To support patients during extreme heat:


Deaths from extreme conditions, already high, are forecast to increase in the coming years and decades and potentially define a new modern era. It is vital to prepare our health system for these threats, including accurate accounting of their toll, and better prepare healthcare providers and the public for the conditions they will face.

This idea of merit originated from our Extreme Heat Ideas Challenge. Scientific and technical experts across disciplines worked with FAS to develop potential solutions in various realms: infrastructure and the built environment, workforce safety and development, public health, food security and resilience, emergency planning and response, and data indices. Review ideas to combat extreme heat here.

Frequently Asked Questions
How would including environmental data on EHRs help patients?

While some emergency care providers might be aware of the extreme weather events unfolding outside and therefore be prepared to treat related illness, the situation can change during lengthy shifts, leaving them less well prepared. This disparity between patient exposure and provider expectations can be even greater in rural areas, where patients might travel significant distances and across diverse terrain such that their exposure differs from conditions at the medical facility.

Time is also a factor. For longer-term impacts like asthma complications that could be related to smoke waves, a medical provider might be unaware that a patient experienced heavy smoke and be less able to diagnose the resulting respiratory issues