For the third year in a row, 2025 turned out a very warm September. The month was persistently warm, and even hot at times, but thanks to a cool snap early on was not as persistently or significantly warm as either 2023 or 2024. Still, it was much warmer than 1991-2020 averages.
Indeed, after a mild first 1-2 days of September, a cold front brought an early taste of fall, with temperatures falling well below normal across Minnesota for 5-7 days. Frost nipped at parts of central and northern Minnesota on some of the coolest mornings, with temperatures below freezing in some areas on the mornings of the 7th, 8th, and 9th.
Warmer air soon surged back into the state, with temperatures rising to above normal, and even much-above normal by the middle of the month, when every part of the state had high temperatures in the 80s F, with many 90s reported from southern Minnesota all the way up to the northwest corner. Sherburne, in the far south, recorded 94 degrees F on the 14th, and the Twin Cities hit 92 F on the 16th.
The heat gave way to a "mild-down," which consisted of clouds and stormy weather dropping temperatures into the 60s and 70s for several days, but still remaining warmer than normal. In the final week of the month, temperatures surged upwards yet again, with widespread highs in the 70s, 80s, and even 90s F as the month drew to a close. Milan, in western Minnesota recorded a high of 94 F on September 29th, and Sabin, in northwestern Minnesota, recorded a high of 91 F on the 30th.
Based on preliminary data, it looks like Minnesota was somewhere between 3.5 and 4.5 degrees F above 1991-2020 averages during September 2025. This would place it among the 10 warmest Septembers on record, and possibly among the top five. Last September, 2024, was the state's warmest on record, averaging 6.5 F above normal.
October 1, 2025
KAB