September 2025 Climate Summary
September 2025 was the warmest September on record in Washington back to at least 1979 and likely the warmest on record back to 1895*. Temperatures were +5.7°F* warmer than normal when averaged statewide. Much warmer than normal temperatures observed across the eastern slopes of the Cascades and across much of eastern Washington. In these warmest areas, temperatures were nearly 5-8°F above normal. In isolated locations, temperatures were around 10°F above normal. These conditions represent record warm conditions for most of the state aside from small portions of interior western Washington and the Pacific Coast, where temperatures were not record breaking but were above normal.
September ranked as the 32nd driest September on record since 1895* with 61%* of normal precipitation statewide. Regionally, precipitation was near or just above normal precipitation along the coast and lower Columbia Basin. Slightly below normal precipitation occurred along the eastern shores of Puget Sound, the Cascades, and in northeastern Washington.
Although precipitation was also below the long-term statewide average, it was temperatures that were truly impressive this past month. A scatterplot of September precipitation versus September temperature for every September dating back to 1979 demonstrates just how anomalous temperatures were in September 2025 (denoted by the bright red dot on the bottom righthand quadrant of the scatter plot).
Many locations, particularly in eastern Washington, broke all-time September temperature records. The upper portion of the table below shows selected stations that observed their warmest September in their respective periods of record.
Not only did these records occur across a large geographic area from Pullman to Yakima to Spokane, but previous monthly records fell by impressive margins. Spokane’s longstanding September monthly record from 1938 fell by an entire 1.0°F. Wenatchee, Yakima, and Tri-Cities/Pasco also broke their previous September record by around 1.0°F. These three cities also had just set their previous record last September in 2024. Stations in eastern Washington generally ran 5-8°F above normal while stations in western Washington ran 1-4°F above normal.
*Statewide normals and rankings are estimated from gridMET data due to the government shutdown. Anomalies are based on 1991-2020 normals.