Last month was the warmest September on record for the contiguous United States, surpassing the previous record set in 1998, according to a new report from the National Oceanic and Atmospheric Administration (NOAA).
The Lower 48 recorded above-average temperatures for the 20th straight month, continuing a streak that began in February 2025. So far, four months this year have ranked as the warmest on record: March, July, August and September. NOAA’s temperature records date back to 1895.
Above-average temperatures were recorded in 43 states last month, with eight states experiencing their warmest September on record: Arkansas, Illinois, Kansas, Louisiana, Missouri, New Mexico, Oklahoma and Texas. In contrast, Oregon was the only state with below-average September temperatures.
The new record was primarily driven by exceptionally warm overnight low temperatures rather than extreme daytime highs. An estimated 80 million people experienced their warmest September nighttime temperatures on record, according to the report.
While parts of the contiguous U.S. experienced persistently drier-than-average conditions, some regions saw beneficial rainfall with above-average precipitation recorded.
In the Southwest, Arizona experienced its wettest September since 1983, with New Mexico seeing its wettest since 1941. Overall, the Southwest received more than twice its average September precipitation last month.
Hawaii experienced its wettest September since 2015, fueled in part by Hurricane Lowell. The state received 10.83 inches of precipitation, which is 6.42 inches above the monthly average.
According to the latest U.S. Drought Monitor report released on October 8, about 55% of the contiguous U.S. was in drought, a slight decrease compared to the beginning of September. Last month, drought expanded or intensified across much of the southern Plains, Lower Mississippi and Tennessee valleys.
Meanwhile, drought conditions improved in parts of the Southwest, northern Plains and Upper Midwest. In Puerto Rico, conditions improved significantly, with severe drought coverage dropping from more than 60% at the start of September to less than 30% by the end of the month.
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