Who Is at Risk for Heat Waves, Droughts and Wildfires?

To see how cities are responding to these hazards, read this companion piece on the rise of the chief heat officer.
On July 20, more than 154 million people — 46 percent of the American population — were in an area under National Weather Service extreme heat advisories, watches and warnings, according to the National Integrated Heat Health Information System.

This rash of heat waves has led the federal government to announce $2.3 billion in grant funding, through the Federal Emergency Management Agency’s Building Resilient Infrastructure and Communities program to help local governments prepare for future high heat conditions. The White House also announced in July expansions to the Low Income Home Energy Assistance Program and the launch of heat.gov, a website offering resources and data on extreme heat for local government planners and officials.

Communities around the country are responding to the risks they face from extreme heat by creating or expanding offices dedicated to resilience. Some are even hiring chief heat officers, like the city of Los Angeles. The city of Miami and Miami-Dade County created a collaborative office to handle resiliency and recently announced the county’s first CHO.

But these cities aren’t alone in facing risks due to heat. In fact, the cities and counties at highest risk from heat waves are mostly in the Midwest and Northeast, according to data from FEMA.
Using historical data on local heat wave frequency as well as data on property value, population size, community reliance and social vulnerability, FEMA identifies areas at risk of dangerous heat waves.

The county-level areas at highest risk of heat waves are:

1. St. Louis, Mo. 
2. Philadelphia County, Pa.
3. Bronx County, N.Y.
4. St. Louis County, Mo.
5. Kings County, N.Y.
6. Cook County, Ill. 
7. Clark County, Nev.
8. Tulsa County, Okla.
9. Shelby County, Tenn.
10. Jackson County, Mo.
    

High heat can bring damaging wildfires and droughts as well, and the communities at highest risk to these hazards aren’t always the same ones that face risk from high air temperatures.

The county-level areas at highest risk of droughts are:

1. Santa Barbara County, Calif.
2. Glenn County, Calif.
3. Colusa County, Calif.
4. Sutter County, Calif.
5. Sacramento County, Calif.
6. Butte County, Calif.
7. Parmer County, Texas
8. Yolo County, Calif.
9. Merced County, Calif.
10. Napa County, Calif.

The county-level areas at highest risk of wildfires are:

1. Riverside County, Calif.
2. Los Angeles County, Calif.
3. San Diego County, Calif.
4. San Bernardino County, Calif.
5. Navajo County, Ariz.
6. Gila County, Ariz.
7. Yavapai County, Ariz.
8. Coconino County, Ariz.
9. Marion County, Fla.
10. Pima County, Ariz.

About one-quarter of Americans live in a county designated at very high or relatively high risk of heat waves, according to data from FEMA.

High heat is a problem that more cities will face more often in coming decades. The average annual temperature around the country has been increasing in recent years, according to data from the National Oceanic and Atmospheric Administration (NOAA). The hottest seven years on record in the U.S. all happened in the past 16 years.
The number of high-temperature days cities face each year is projected to increase as well. Data from NOAA projects that Philadelphia County, for example, will have 65 days with temperatures above 95 degrees Fahrenheit by the year 2090, more than three times its number of projected high-temperature days in 2030.

While many cities are facing high heat, these considerations are often taken in a broader conversation about resilience. For many cities, they must weigh the risks of heat waves alongside flooding, drought, hurricanes and other natural disasters.

FEMA also tracks counties’ risks of natural hazards based on historical data from more than a half dozen federal agencies. The agency creates an overall risk index using that data alongside metrics developed by the University of South Carolina’s Hazards Vulnerability and Resilience Institute. These include a social vulnerability metric based on susceptibility of social groups to the adverse impacts and a resilience metric based on the ability of a community to prepare for and adapt to natural hazards. The overall risk also accounts for the expected annual financial impacts of natural hazards based on data from Arizona State University.

“This data helps policymakers and elected officials prioritize projects that save lives, protect property and reduce disaster suffering from the devastating effects of natural hazards,” said Michael Grimm, FEMA’s assistant administrator for risk management, in an email interview. “With the increasing threat of climate change, the index informs risk-based decisions, supporting the adoption of and enforcement of enhanced building codes and more resilient infrastructures across the nation.”