The Hottest Summer Ever Recorded in These US Counties

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During the months of June, July, and August – the meteorological summer in the United States – the average temperature across the Lower 48 was 73.3°F, making 2025 the 12th warmest summer in U.S. history. While this year’s summer was about half a degree cooler than the summer of 2024, the average temperature from June through August was still nearly 2°F higher than the 20th century baseline average for the season.

Indeed, the global warming phenomenon – often most clearly evidenced in the U.S. by hotter summers and milder winters – is hardly slowing down. According to analysis from the U.K. based climate policy group Climate Brief, 2025 is on pace to be either the second or third hottest year on record, worldwide.

Even though average temperatures in 2025 will not likely break records around the world or in the United States, there are still several parts of the country where this past summer now stands as the hottest ever recorded.

Using data from the National Atmospheric and Oceanic Administration, Climate Crisis 247 identified the U.S. counties where summer 2025 now stands as the hottest summer on record. We reviewed data for over 3,100 counties and county equivalents in the U.S. and listed those in which average temperatures in summer 2025 were the highest in the last 131 years of available data. Counties are ranked on average local temperature between June and August, 2025, relative to the baseline average summer temperature. Baseline temperatures, as classified by NOAA, are average temperatures over the months of June, July, and August each year from 1901 through 2000. Supplemental population data are five-year estimates from the U.S. Census Bureau’s 2023 American Community Survey. Due to rounding, temperature anomalies may not represent the precise difference from noted 2025 and baseline averages.

The counties on this list span three states – Colorado, Ohio, and West Virginia – and are home to more than a quarter million Americans.