Frequently Asked Questions
What does this tool show? This tool maps the gap between how serious extreme heat risk actually is in U.S. counties—based on a comprehensive public health index—and how worried residents of those counties say they are about heat. When assessed risk and public worry don’t match, it can signal communities that may need more targeted outreach and preparedness support.
Where does the heat risk data come from? Assessed heat risk is based on the CDC’s Heat & Health Index (HHI), which integrates 25 indicators across four dimensions: historical heat exposure and heat-related illness; pre-existing health conditions such as heart disease, diabetes, and respiratory illness; sociodemographic factors including poverty, age, lack of health insurance, and social isolation; and features of the natural and built environment like tree canopy, impervious surfaces, and air quality. The index was developed at the ZIP code level and aggregated to counties and states.
Where does the public worry data come from? Estimates of public worry come from a multi-year national survey (2018–2022) of over 11,000 U.S. adults conducted through the IPSOS KnowledgePanel. Respondents were asked how worried they are that extreme heat might harm their local area. Those who answered “very worried” or “moderately worried” were classified as worried. Researchers at Yale University and George Mason University then used advanced statistical modeling—multilevel regression with poststratification, enhanced with machine learning—to produce reliable estimates for every county in the contiguous United States, even those with few or no direct survey respondents.
What do the four categories on the map mean?
The maps sort every county into one of four groups based on whether its assessed heat risk and public worry each fall above or below a threshold:
Higher Risk, Lower Worry (Danger Zone): These counties face elevated health vulnerability from extreme heat, but a relatively small share of residents report being worried. This is the most common pattern nationwide—nearly half of all counties fall into this category—and it is especially prevalent across the Pacific Northwest, Appalachia, Michigan, Georgia, and Maine. The mismatch may leave these communities less prepared when dangerous heat arrives.
Higher Risk, Higher Worry: In these counties, public concern roughly matches the level of assessed risk. They are concentrated along the southwestern border and in parts of Texas and California—places with long histories of intense heat where experiential knowledge aligns more closely with expert assessments. Even here, though, familiarity with heat can breed complacency.
Lower Risk, Higher Worry: These counties have lower assessed health risk but higher-than-expected public concern. Only a handful of counties fall into this category nationwide, which suggests that Americans rarely overestimate heat risk relative to expert assessments.
Lower Risk, Lower Worry: These counties currently face lower assessed risk, and residents report relatively low concern. They are concentrated in the upper Midwest, New England, and parts of the southern Appalachians. However, many of these areas are warming rapidly, have limited cooling infrastructure, and may be unprepared for future heat events.
Why doesn’t the risk map just show the hottest places? Because heat risk to human health depends on much more than temperature. A county with moderate summer temperatures but high rates of chronic disease, widespread poverty, limited healthcare access, older housing stock, or an aging population can face serious health consequences during a heat wave. The CDC’s Heat & Health Index captures this full spectrum of vulnerability, which is why the geographic pattern may look quite different from a simple temperature map.
How is public worry measured and modeled? Survey respondents were asked a single question: “How worried are you that extreme heat might harm your local area?” The research team used a technique called multilevel regression with poststratification (MRP), enhanced with machine learning algorithms (XGBoost, Random Forest, and Elastic Net), to generate county-level estimates from individual survey responses. The models incorporated local climate data, sociodemographic characteristics, and other contextual factors. The final ensemble model achieved a mean absolute error of about 1.6 percentage points when validated against the most heavily surveyed counties.
How is the “gap” between risk and worry calculated? The CDC’s Heat & Health Index was rescaled to a 0–100 range to match the percentage scale of the worry estimates. The gap for each county is simply the rescaled HHI score minus the estimated percentage of residents who are worried about extreme heat. Positive values mean assessed risk exceeds public worry; negative values mean worry exceeds assessed risk.
What are the thresholds for “higher” vs. “lower” risk and worry? Counties are classified as higher or lower assessed risk based on the national median of the Heat & Health Index. For worry, the threshold is 50 percent—whether a majority of residents report being at least moderately worried. Because only about 35 percent of Americans overall say they are worried about extreme heat, very few counties cross the majority-worry threshold, which is why the “higher worry” categories contain far fewer counties.
How many counties fall into each category? The largest group by far is Higher Risk, Lower Worry, with roughly 1,440 counties. Lower Risk, Lower Worry accounts for about 1,550 counties. Higher Risk, Higher Worry contains around 113 counties. Lower Risk, Higher Worry includes just two counties nationwide—Bossier Parish, Louisiana and Tom Green County, Texas—underscoring that underestimation of heat risk is a far more common pattern than overestimation.
Why might people underestimate heat risk? The study finds that risk perceptions are shaped heavily by personal experience—how hot it has felt recently, whether heat has caused visible harm nearby. In regions without a long cultural memory of dangerous heat, or where heat’s health impacts are less visible than those of hurricanes or floods, residents may not recognize their vulnerability. Counties with higher poverty rates and larger shares of residents over 65 tend to show bigger gaps between assessed risk and public concern. Limited historical exposure, older housing without adequate cooling, barriers to healthcare access, and cultural norms of self-reliance can all contribute.
What factors predict the gap between risk and worry? Statistical analysis identified several demographic and socioeconomic factors associated with the size and direction of the gap. Higher poverty rates and larger proportions of residents over 65 are associated with underestimating heat risk relative to expert assessments. Higher educational attainment and larger Black populations are associated with higher perceived risk relative to assessments. Hispanic population share is associated with underestimation, but this pattern reverses in high-poverty Hispanic communities. These relationships likely reflect a complex mix of lived experience, cultural knowledge, access to information, and structural vulnerability.
Does the map show future heat risk? No. The assessed risk reflects current and historical conditions as captured by the CDC’s Heat & Health Index, and the worry estimates are based on surveys from 2018 through 2022. The maps do not project future climate conditions. However, many counties currently classified as lower risk—particularly in the northern United States—are warming rapidly and may face significantly higher heat-health risks in the coming decades, often without the cooling infrastructure or public awareness needed to respond.
Can I look up a specific county? Yes. Use the interactive tool above to search for or click on any county in the contiguous United States. The tool will display that county’s assessed heat risk, estimated public worry, and which of the four gap categories it falls into.
Where can I learn more about the research behind these maps? These maps are based on the study “Experience-driven perceptions misalign with assessed heat risk in the United States” by J.R. Marlon, N. Begotka, and colleagues at Yale University, ClimateCheck, Tulane University, Georgia State University and Georgia Tech, and George Mason University. The study introduces the Risk Analysis–Perception (RAP) framework for systematically quantifying gaps between expert risk assessments and public perceptions. More information about the CDC’s Heat & Health Index is available at the CDC’s Environmental Public Health Tracking Network.