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Preliminary Climate Summary for September 2021

Preliminary Climate Summary for September 2021

Very warm with highly variable rainfall are good descriptors for the month of September in Minnesota this year. Well over half of the days were above normal in temperature. Most climate stations reported a mean monthly temperature that ranged from 3 to 5 degrees F warmer than normal. Statewide September of 2021 ranked as the 8th warmest in history back to 1895. Extremes for the month ranged from 95°F at Milan (Chippewa County) on the 16th to just 29°F at Hibbing (22nd), at Embarrass (23rd), and at Brimson (25th). Over two dozen daily maximum temperature records were set or tied within the state climate network during the month.

Rainfall was highly variable, especially across northern sections of Minnesota. Many parts of the northwest along the Red River Valley saw only about 1 inch of rainfall, while portions of northeastern Minnesota reported over 5 inches of rainfall for the month. Other areas in west-central Minnesota received over 5 inches as well. Overall there were about as many climate stations reporting below normal precipitation as above normal. The statewide average monthly value for rainfall was just under 3 inches. Madison (Lac Qui Parle County) reported a new record rainfall on September 3rd with 2.80 inches, while Waskish (Beltrami County) reported a new daily record rainfall on September 20 with 2.93 inches. A few other climate stations reported record-setting daily rainfalls over 2 inches as well during the month.

There were between 12 and 14 days with gusty winds (over 30 mph). Thunderstorms on September 16th delivered strong straight-line winds over 60 mph to many parts of the state, and the National Weather Service reported 4 EF-0 tornadoes that day as well (estimated wind speeds of 85mph). Most damages reported by the National Weather Service were the results of trees falling on buildings or motor vehicles. Some areas also reported 1-2 inch diameter hail on that date as well.

According to the US Drought Monitor some areas of affected by drought shrunk slightly during September, but still about 50 percent of the state landscape (nearly all northern counties) are in the grip of Severe Drought or Extreme Drought. Very low flows are still being observed in more northern streams and rivers.

Weekly Weather Potpourri:

The NOAA Climate Program Office released a study of climate change and impacts on megadroughts in the southwestern USA. The study showed that, regardless of future levels of greenhouse gas emissions, the warming climate has locked in an elevated risk of intense megadroughts for the region. However, mitigation measures—efforts to reduce the amount of greenhouse gases in the atmosphere—can and do reduce the risk of intense single-year droughts. The severity of megadroughts declines with mitigation as well, making their impacts less damaging.

According to the Joint Typhoon Warning Center, Typhoon Mindulle will just give a glancing blow to Tokyo and other parts of Japan as it passes to the northeast over the weekend. It will still bring strong winds and heavy rains, perhaps 6-10 inches in places. At one time this typhoon had produced winds of 130 mph and sea wave heights over 40 feet.

The NOAA Climate Prediction Center Revised Outlook for October suggests a higher probability of above normal temperatures, as well as above normal precipitation during upcoming month. This would be welcome for farmers to wrap up harvesting and field work, but also see some soil moisture recharge take place before soils begin to freeze up for winter.

Congratulations to the University of Minnesota for obtaining a $4.5 million five-year grant to establish the Midwest Climate Adaptation Science Center. This new center is designed to generate research, data sets and tools that natural and cultural resource managers can use to help ecosystems and communities effectively respond to a changing climate. Dr. Heidi Roop, who replaced me on the faculty of the Department of Soil, Water, and Climate is one of the principal scientists involved.

MPR listener question:

We had 95°F earlier this month here in Milan, MN, which was a new record high for September 16th. Some of us were talking at the Glacial Plains Coop Elevator and wondered what is the latest calendar date for recording a 100°F in Minnesota?


Believe it or not September 22, 1936 brought a temperature of 101°F to Ada (Norman County), and then the very next year September 21, 1937 brought 101°F to Wheaton (Traverse County). Hard to believe it can get that hot when the sun is in roughly the same position in the sky as on March 21st (Vernal Equinox) when the hottest temperature in Minnesota history was only 81°F (March 21, 1910 at Montevideo (Chippewa County). BTW the latest 90°F reading In Minnesota was at Canby (Yellow Medicine County) on October 30, 1950.

Twin Cities Almanac for October 1st:

The average MSP high temperature for this date is 66 degrees F (plus or minus 10 degrees F standard deviation), while the average low is 47 degrees F (plus or minus 7 degrees F standard deviation).

MSP Local Records for October 1st:

MSP records for this date: highest daily maximum temperature of 87 degrees F in 1897; lowest daily maximum temperature of 45 degrees F in 1999; lowest daily minimum temperature of 24 degrees F in 1974; highest daily minimum temperature of 61 degrees F in 1971; record precipitation of 1.29 inches in 2009. No measurable snowfall has occurred on this date.

Average dew point for October 1st is 43°F; the maximum dew point on this date is 66°F in 1951; and the minimum dew point on this date is 18 degrees F in 2003.

All-time state records for October 1st:

The state record high temperature for this date is 93 degrees F at Browns Valley (Traverse County) in 1976. The state record low temperature for this date is 10 degrees F at Moorhead (Clay County) in 1886. The state record precipitation for this date is 4.25 inches at White Earth Nation Reservation (Mahnomen County) in 1869. Record snowfall is 8.5 inches at Isabella (Lake County) in 1985.

Past Weather Features:

Record-setting cold weather prevailed across Minnesota on October 1, 1886. Most areas reported morning low temperatures in the twenties. Albert Lea reported just 20°F, while Moorhead was just 10°F. Afternoon high temperatures only reached the 40s F in many areas that day.

October started out very wet in 1950. A slow moving low pressure system brought 2 to 4 inches of rainfall to most areas of the state, with the largest amounts along the Lake Superior north shore.

October 1, 1976 was the hottest in state history with most places reporting afternoon high temperatures in the 80s F. Portions of Wilkin, Houston, Fillmore, and Traverse Counties reported temperatures in the 90s F. The cool spot was Grand Marais Harbor with just 58°F.

An early taste of winter greeted many northern Minnesota citizens on October 1, 1985, as heavy, wet snow fell across portions of Koochiching, St Louis, Lake, and Cook Counties. Tower and Isabella both reported over 6 inches. The snow was short-lived as temperatures rebounded into the 50s and 60s F the next day.


Chance for widely scattered showers and thunderstorms on Saturday into early Sunday with above normal temperatures. Drier for Sunday through Thursday next week with temperatures generally a few degrees warmer than normal.

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