Historic Autumn Heat, September 30 - October 3, 2023

people at a lake
Swimming in October? Minnesotans took to the water to beat the heat at Square Lake Park in Washington County on October 1, 2023. Courtesy: Minnesota State Climatology Office

An extraordinary burst of summer-like heat closed out September and opened October, prompting a rare cancellation of the Twin Cities Marathon, and breaking a slew of daily, and all-time monthly high temperature records for October across the state.

The heat ramped up first on Saturday September 30, 2023, following what had been a very stormy night across eastern, central, and southern Minnesota. Temperatures soared through the 80s F and climbed into the low 90s F across the southern quarter of Minnesota. Rochester and the Twin Cities set daily high temperature records for the date, with 90 F and 88 F, respectively.

The heat reached its peak intensity on Sunday October 1st, as temperatures climbed to 90F or higher over all of western, central, and southern Minnesota. The high temperature of 92 F in the Twin Cities was the highest for the date, the highest for any October date on record and, therefore, the highest temperature ever recorded so late in the season. The same was true for the 91 F high temperature recorded in St. Cloud. Rochester again set a daily record with 90 F, as did International Falls, with 84 F.

Owing to the unusual risks to runners, the heat prompted organizers to cancel the Twin Cities Marathon on Sunday October 1st for the first time in the the event's history, back to 1982.

Hot weather continued on Monday, though with slightly less bite. International Falls, St. Cloud, and the Twin Cities each tied their daily high temperature records for October 2nd, with 87 F, 90 F, and 89 F, respectively. Although the overall magnitude of the heat had begun declining by Tuesday October 3rd, it was still uniformly warm across the state with widespread 80s F reported--still 20-30 degrees above normals for this time of the year. International Falls set another daily high temperature record with 84 F, and Duluth did also, by reaching 82 F.

The morning low temperatures during this heat wave were also unusually high. International Falls had its highest October daily minimum temperature on record, with a low of 69 F on October 2nd. The previous record had been 64 F, making the record-breaking margin unusually large. Duluth also set its all-time October "warm low" record on two consecutive days, recording a minimum of 63 F on the 2nd, and then edging it out on the 3rd with a low of 64 F; the previous record had been 62 F.   Additionally, daily "high-minimum" temperature records were also set at International Falls (62 F on 10/1), Rochester, (67 F on 9/30), St. Cloud (64 F on 9/30, 65 F on 10/1, and 64 on 10/3), and the Twin Cities (69 F on 10/1 and 67 F on 10/2).

The highest temperature recorded by a National Weather Service cooperative observer was 95 F at Milan and Lamberton. The highest temperature on record anywhere in the state during October is 98 F, observed at Beardsley on October 5, 1963.

Updated October 8, 2023

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