U.S. Records Hottest June-August Period on Record, Surpassing 1936 Heat

New data from the National Oceanic and Atmospheric Administration indicate that the contiguous United States and Washington, D.C. recorded an average temperature of 74.4 °F for the June-August period, the warmest on record and 0.4 °F above the previous best set in 1936 and tied in 2021. The agency documented 1,571 monthly high-temperature records across the country, while only 87 monthly lows were recorded.

Analysis of nighttime temperatures shows 2026 set a new benchmark for high overnight lows, with an estimated 133 million Americans living in counties where at least 25 % of nights were classified as "extremely hot" compared with the previous 45 years. An additional 56.8 million people reside in areas where one in four days reached extreme heat levels.

The heat wave began early in the western United States, where eight states from Texas to California experienced their warmest January-May stretch on record. Colorado, New Mexico and Utah each recorded their hottest summers, while Arizona matched its previous record.

Four of the six warmest U.S. summers have occurred since 2021, and scientists note that marine heat waves now affect about 40 % of the world's oceans. The previous month was the warmest worldwide on record, and with a strong El Niño developing, researchers estimate a 95 % probability that 2027 could become the hottest year globally.

"The 1936 heat wave was largely a human-induced disaster. The over-plowing of the Great Plains that helped foster the Dust Bowl left the landscape so denuded that water evaporated quickly and the landscape warmed up fast," meteorologist Bob Henson said.

"It's a flashing red light that we're now able to get US summers even hotter than those in the Dust Bowl," Henson added.