Heat waves do not knock down buildings, so they rarely make the evening news the way hurricanes do. But extreme heat kills more Americans than any other weather hazard, according to the National Weather Service.
FEMA’s National Risk Index estimates expected yearly heat wave losses at about $7.1 billion nationwide. Most of that estimate comes from the value FEMA places on lives lost and injuries, not property damage.
11 counties are rated Very High for heat waves and 98 are Relatively High.
Counties with the highest expected heat wave losses
| Rank | County | Expected loss a year |
|---|---|---|
| 1 | Maricopa County, AZ | $958 million |
| 2 | Clark County, NV | $295 million |
| 3 | Dallas County, TX | $288 million |
| 4 | Philadelphia County, PA | $256 million |
| 5 | St. Louis County, MO | $253 million |
| 6 | Cook County, IL | $193 million |
| 7 | St. Louis City, MO | $172 million |
| 8 | Pima County, AZ | $133 million |
Source: FEMA National Risk Index, December 2025.
Maricopa County, which includes Phoenix, is far ahead of everywhere else. Phoenix regularly sees long runs of days above 110°F, and the county reports hundreds of heat-related deaths in bad years.
Not just the desert
Philadelphia, St. Louis and Chicago may surprise people on this list. Heat waves in these cities are less frequent than in Phoenix, but older housing without air conditioning, dense neighborhoods that hold heat overnight, and humid air make them dangerous. The 1995 Chicago heat wave killed more than 700 people in about a week.
Per resident, among counties with at least 100,000 people, the highest expected losses are in:
- St. Louis City, Missouri: about $572 a year
- St. Louis County, Missouri: about $252
- Maricopa County, Arizona: about $217
- Washington County, Arkansas: about $192
- Cochise County, Arizona: about $178
Who is most at risk?
Adults over 65, young children, people with heart or lung conditions, outdoor workers and people living alone are most vulnerable. Homes without working air conditioning, top-floor apartments and neighborhoods with little shade get hotter.
How to prepare
- Check that air conditioning works before summer, and have a plan if the power goes out.
- Find the nearest cooling center. Many cities list them online and open libraries and community centers during heat emergencies.
- Drink water before you feel thirsty and avoid heavy outdoor work in the afternoon.
- Check on older neighbors and relatives, especially those who live alone.
- Never leave children or pets in a parked car, even for a few minutes.
Questions people ask
What counts as a heat wave? There is no single national definition. The National Weather Service issues heat advisories and excessive heat warnings based on local temperatures and humidity, because what is dangerous in Seattle differs from what is dangerous in Phoenix.
Does insurance cover heat waves? Home insurance does not cover heat itself. It may cover related damage, such as a fire, depending on the policy.
Is heat getting worse? US heat waves have become more frequent since the 1960s, according to the Environmental Protection Agency’s climate indicators. Nights are also staying warmer, which gives the body less chance to recover.
See the heat wave hazard page for the full ranking, or look up any county with the search box.