Graph of daily and 10-day accumulated temperature departures back to June 1, 2024 at St. Cloud, showing the greatest relative warmth occurring during the mid-September warm spell. Image created by Minnesota DNR State Climatology Office.
It wasn't the hottest September weather on record by far, but a warm spell that dominated the middle third of September 2024 was noteworthy for its depth, persistence, and uniformity across Minnesota. A second, only slightly lesser warm spell followed it just two days later and lasted through the final day of the month. After a cool start to the month, a much warmer air mass took over by September 9th or 10th. High temperatures rose into the 80s F on most days in most places, with little in the way of south-to-north contrast. Between the mornings of September 9th and September 21st, almost all reporting stations recorded at least six days with high temperatures of at least 80 degrees F, but the highest temperature during that time was just 92 F at Granite Falls, and only a few other stations in southwestern Minnesota hit 90F. After two normal to slightly cool days on the 22nd and 23rd, another surge of warm air moved into the state and remained in place through the 30th. This warm spell was marked by clear skies, light winds, and very dry air. High temperatures rose into or through the 80s again, but overnight temperatures fell to much more seasonable levels. Between the two, average daily temperatures were nevertheless 10-20 degrees above normal across the state during this time. The air temperatures during this warm spell would have been above-normal in the middle of July in most areas. And though these temperatures are not the highest of 2024, the large departures from normal over a relatively long period make this the largest warm spell since June 1, putting September on track to be among the warmest on record for the state. Updated October 3, 2024KAB
