Overview
- The National Centers for Environmental Information report published October 8 showed the contiguous U.S. averaged about 69.4°F in September, the warmest September since records began in 1895 and surpassing the 1998 mark.
- The lower 48 have been warmer than 20th-century averages for 20 straight months through September, and January–September 2026 is the hottest first nine months on record.
- Nighttime minimum temperatures were the main driver of the September record, with more than 30 percent of the country and an estimated 80 million people experiencing their warmest September nights on record.
- Hydrologic extremes were mixed in September as drought expanded across the U.S. South—reaching 89 percent of the region on the September 29 U.S. Drought Monitor—while the Southwest and Hawaiʻi saw much-above-average rain, including heavy September rainfall tied to Hurricane Lowell.
- Global context and outlook show unusually warm oceans and a strong El Niño that helped make September the second-warmest globally and that forecasters expect to favor continued above-average U.S. temperatures and persistent regional drought risks this fall.