FEMA National Risk Index hazard
Prepare your home for heat wave
Periods of extreme heat that strain people, power grids and cooling equipment.
109 US counties are rated Relatively High or Very High for heat wave by FEMA’s National Risk Index. The three things that matter most at home: 1. Service the AC before the hot season and clear the outdoor unit of debris. 2. Change the AC filter; a clogged filter cuts cooling. 3. Plan a cool place to go if the power or AC fails.
Before the season
- Have the AC or heat pump checked before peak season.
- Close gaps around window units and add shades on sun-facing windows.
- Check on older neighbors and relatives and plan a cooling center.
When a warning comes
- Keep blinds closed during the day; run fans and the AC early.
- Avoid using the oven and dryer during the hottest hours.
- Drink water and check on vulnerable people twice a day.
After
- If the AC failed, check the breaker and the outdoor disconnect before calling for service.
- Clear the condensate drain line; heavy use clogs it.
- Note when the system struggled; it helps a technician diagnose it.
Ask your insurer
If you rely on medical equipment, ask your utility about medical-need programs during outages. We explain and organize; we never predict coverage.
Ready.gov: Extreme heat Checklist: original casaq guidance
Counties with the highest heat wave scores
Top 25 by FEMA NRI risk score for this hazard. Scores and ratings are relative to other US counties, not probabilities of a loss.
| # | County | Rating | Score | Recorded events |
|---|---|---|---|---|
| 1 | Maricopa County, AZ | Very High | 100.0 | 154 |
| 2 | Philadelphia County, PA | Very High | 100.0 | 125 |
| 3 | Dallas County, TX | Very High | 99.9 | 314 |
| 4 | Clark County, NV | Very High | 99.9 | 78 |
| 5 | St. Louis County, MO | Very High | 99.9 | 153 |
| 6 | Cook County, IL | Very High | 99.8 | 21 |
| 7 | St. Louis City, MO | Very High | 99.8 | 157 |
| 8 | Pima County, AZ | Very High | 99.8 | 93 |
| 9 | Kings County, NY | Very High | 99.7 | 145 |
| 10 | Harris County, TX | Very High | 99.7 | 250 |
| 11 | Queens County, NY | Very High | 99.7 | 112 |
| 12 | Tulsa County, OK | Relatively High | 99.6 | 309 |
| 13 | Bronx County, NY | Relatively High | 99.6 | 153 |
| 14 | New York County, NY | Relatively High | 99.6 | 146 |
| 15 | Shelby County, TN | Relatively High | 99.6 | 353 |
| 16 | Oklahoma County, OK | Relatively High | 99.5 | 286 |
| 17 | Kern County, CA | Relatively High | 99.5 | 73 |
| 18 | Tarrant County, TX | Relatively High | 99.5 | 314 |
| 19 | Baltimore City, MD | Relatively High | 99.4 | 100 |
| 20 | Bexar County, TX | Relatively High | 99.4 | 170 |
| 21 | Washington County, AR | Relatively High | 99.4 | 148 |
| 22 | Los Angeles County, CA | Relatively High | 99.3 | 85 |
| 23 | Wayne County, MI | Relatively High | 99.3 | 68 |
| 24 | Miami-Dade County, FL | Relatively High | 99.3 | 50 |
| 25 | Baltimore County, MD | Relatively High | 99.2 | 84 |