The counties with the most 90-degree days, and Texas holds 49 of the top 56

Yuma County, Arizona, and Imperial County, California, each had 156 days that reached at least 90 degrees Fahrenheit in 2022, more than any other US county. That is more than five months of 90-degree heat, in the desert along the border with Mexico.

The counts come from weather data the U.S. Census Bureau distributes with its experimental Community Resilience Estimates for Heat, drawn from the National Oceanic and Atmospheric Administration's North American Regional Reanalysis. They cover a single year, 2022, for every county in the country.

Texas dominates

Fifty-six counties had at least 90 days of 90-degree heat in 2022, and Texas has 49 of them. Arizona has four and California three. The list runs to 56 because 11 Texas counties tie at exactly 90 days. The Texas counties stretch from the Rio Grande Valley, where Hidalgo and Starr counties each had 128 such days, north through San Antonio and the Hill Country, plus parts of West Texas.

Only 28 counties reached 100 or more days of 90-degree heat. At the other end, 453 of the country's 3,144 counties never reached 90 degrees at all in 2022.

Where the most people live with the heat

Among counties with at least a million residents, Maricopa County, home to Phoenix, had the most 90-degree days, 147. San Antonio's Bexar County was second with 117, followed by Travis County, Texas, home to Austin (89), San Bernardino County, California (84), and Dallas and Tarrant counties in Texas (80 each). Maricopa alone has about 4.6 million people.

Whether households can cool their homes is a separate question, covered in El Paso County households without air conditioning. The full ranking is at counties with the most extreme-heat days.

Sources

Days with a maximum temperature of at least 90°F in 2022 are from the heat-exposure data, based on the National Oceanic and Atmospheric Administration's North American Regional Reanalysis, distributed with the U.S. Census Bureau's experimental Community Resilience Estimates for Heat. The figures are modeled for each county and cover one year, so a single unusually hot or cool summer affects the ranking. County populations are from the 2020-2024 American Community Survey.