Preliminary Climate Summary for September of 2024:
Warm and dry are the succinct words for this September in Minnesota. This will be the first time in history that the statewide average September temperature will exceed 64°F, surpassing the previous warmest September of 2015 (63.8°F). Most climate stations will report an average monthly temperature that is 5°F to 8°F above normal. Counties of northwestern and north-central Minnesota were nearly 9°F warmer than normal. Extremes were 92°F at Granite Falls (Yellow Medicine County) on the 16th and 26°F at Ely (St Louis County) on the 7th. Within the state climate station network, there were 48 record daily high temperatures and 73 record daily warming minimum temperatures. Many nighttime temperatures remained in the 60s F, and even a few nights never went below 70°F at places like Milan (Chippewa County) and Alexandria (Douglas County).
September was drier than normal in almost all areas of Minnesota, except for the far northern sections of Lake of the Woods, Koochiching, Itasca, and St Louis Counties which received some heavy rains from isolated thunderstorms, and they totaled over 3 inches. Many climate stations reported less than a quarter of an inch of rainfall for the month, and some received less than a tenth of an inch. Some of the driest spots included Redwood Falls Municipal Airport with just a trace of rain, and Wolf Ridge ELC with only 0.05 inches. Over 40 climate stations reported the driest September in history, including Two Harbors and MSP with just 0.06 inches of rainfall.
On a statewide basis the average rainfall was 0.52 inches, which is the driest September on record back to 1895. As a result of the warm, dry month, Minnesota saw drought conditions return to some portions of the state. At the beginning of September less than 20 percent of the state landscape was designated to be abnormally dry and there were no areas in drought according to the U.S. Drought Monitor. However, as we end the month, over 80 percent of the state landscape is abnormally dry, and nearly 16 percent is in Moderate Drought (mostly southwestern counties and northeastern counties).
The NOAA Climate Prediction Center models all favor a warmer and drier than normal pattern to prevail across Minnesota through the first two weeks of October.
Weekly Weather Potpourri:
The Weather Underground was reporting updates on Hurricane Helene this week as it moved north offshore along the west coast of Florida. The hurricane brought heavy rains, high winds, and significant storm surge to many areas of Florida’s west coast, especially north of Venice. Some areas of the state had already received 4-6 inches of rainfall by midday on Thursday. The hurricane was expected to cause serious damage in the Big Bend area north of Tampa.In other news related to Hurricane Helene, the Wall Street Journal this week featured an interesting article about the use of drones to monitor and assess hurricanes as they form and develop. These drones are used to bring more frequent and multi-level measurement data to the National Hurricane Center forecasters and might be expected to be used routinely in the future as they are most cost-effective than hurricane hunter aircraft. (Thanks to Bob Potter formerly of MPR for this tip).
A recent study published in the journal Nature documents a case for more frequent and extreme El Nino episodes due to climate change impacts. The authors from the University of Colorado find that with continued warming of the equatorial bands of latitude, atmospheric and oceanic dynamics will favor more frequent El Nino formations, as well as strong episodes. Many of the strong El Nino episodes are associated with some of the warmest years in the global climate record.
This week’s AGU-EOS news contains an article about increased frequency of wildfires in the Arctic Region of Siberia. New research demonstrates that the rise in Siberian wildfires is related to drought, drying soils, and decreased rainfall caused by Arctic warming.
MPR listener question:
We noticed this week that the afternoon relative humidity values were in the teens in many parts of western Minnesota. Having lived in Arizona before moving to Minnesota a few years ago we grew accustomed to such dry air in September. But how often does this happen during September in Minnesota?Answer:
Yes, I noticed some readings as low as 16 percent in the Red River Valley this week. Such dry September air is unusual in Minnesota. In the western portions of the state, September relative humidity can drop below 20 percent about once per decade. In the eastern portions of the state, which are occupied by more lakes and forests, such low humidity in September only comes about once every two decades. If such conditions are accompanied by high winds and above normal temperatures the National Weather Service will release a Red Flag Warning for high fire danger.Twin Cities Almanac for September 27th:
The average MSP high temperature for this date is 68 degrees F (plus or minus 11 degrees F standard deviation), while the average low is 49 degrees F (plus or minus 8 degrees F standard deviation).MSP Local Records for September 27th:
MSP records for this date: highest daily maximum temperature of 88 degrees F in 1987; lowest daily maximum temperature of 40 degrees F in 1942; lowest daily minimum temperature of 29 degrees F in 1991; highest daily minimum temperature of 65 degrees F in 2013, and record precipitation of 0.54 inches in 1947. No snowfall has occurred on this date.
Average dew point for September 27th is 45°F; the maximum dew point on this date is 67°F in 1905 and the minimum dew point on this date is 24 degrees F in 1951.
All-time state records for September 27th:
The state record high temperature for this date is 97 degrees F at Beardsley (Big Stone County) in 1894, at Hallock (Kittson County) and Wheaton (Traverse County) in 1952, and at Canby (Yellow Medicine County) in 1956. The state record low temperature for this date is 13 degrees F at Beardsley (Big Stone County) in 1893. The state record precipitation for this date is 3.50 inches at Wolf Ridge ELC (Lake County) in 1996. The statewide snowfall record for this date is 2.0 inches at Tower (St Louis County) and Bemidji (Beltrami County) in 1899 and at Littlefork (Koochiching County) in 1912.Past Weather
Freezing temperatures brought an abrupt end to the Minnesota growing season on September 27 of 1893. Most parts of the state recorded morning low temperatures in the 20s F, while portions of western Minnesota saw temperatures in the teens. The afternoon high temperature only reached 47°F at Park Rapids.Avery early season snowstorm brought several inches to parts of Minnesota over September 26-27 of 1942. Several locations reported 2-4 inches, and a few like Willmar and Detroit Lakes reported 6 inches or more.
It felt like mid-July on September 27 of 1956 as most areas of the state reported afternoon temperatures between 85°F and 95°F. Canby reached 97°F. Humidity was so low that there was fire danger in many places.
Outlook:
Continued warm, sunny, and dry weather throughout the weekend and most of next week. Temperatures will average several degrees above normal.
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