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Warmest Week of the Month

Warmest Week of the Month:

This week, especially September 22-24, brought the warmest temperatures of the month to most parts of Minnesota. Over 85 climate stations reported daytime highs in the 80s F, as high as 88°F at Marshall (Lyon County), Granite Falls (Yellow Medicine County), and Sabin (Clay County). MSP had its warmest reading of the month on Wednesday (September 23) with a high of 84°F.

A few climate stations even set new record high temperature: On the 22nd Brimson (St Louis County) reported a new record high of 77°F; on the 23rd Cass Lake (Cass County) reported a new record high of 820176F; and on the 24th Redwood Falls reported a new record high temperature of 86°F.

Temperatures are expected to decline the rest of the month, so on balance I would not be surprised to see September finish with cooler than normal monthly mean temperatures. This would be the first cooler than normal month for the state since last May.

Weekly Weather Potpourri:

The NOAA National Snow and Ice Data Center reported that Arctic sea ice reached its seasonal minimum on September 15th, covering 1.44 million square miles, the second lowest seasonal minimum observed in the 42-year satellite record. The average seasonal minimum Arctic sea ice extent for the period 1981-2010 was 2.46 million square miles, so 2020 was over a million square miles less.

NOAA also reports that earlier in the week Tropical Storm Beta brought heavy rains to southeastern Texas, especially the area around Houston where 10-14 inches of rain fell. There was widespread flooding, and many vehicles were abandoned. The Weather Underground reported in detail on this storm.

A recent research study from Stanford University reports that some droughts form as a result of pressure patterns over the oceans. These ocean-based drought areas are extensive and when they make landfall they can persist for long periods of time. As many as one in six droughts may be related to these atmospheric pressure patterns over the oceans. Science Daily reported on this study.

The AGU-EOS Bulletin this week highlights a study that found a dramatic decrease in lightning across the USA during the months of May and June this year. The researchers attribute this to an unusual high-pressure atmospheric pattern that set up over the Southern Plains.

MPR listener question:

It seems like this month has been very dry throughout Minnesota. Many places have reported less than one inch of rain. Is there anywhere in the state that has had surplus rainfall this month?


The notable exception this month is southeastern Minnesota where 3-4 inches of rainfall has been pretty common. Both La Crescent (Winona County) and Caledonia (Houston County) are reporting over 4 inches so far. The surplus rain in September is welcome in those communities because they had an unusually dry August. In fact Caledonia reported its driest August in history (back to 1892) with only 0.64 inches of rain last month.

Twin Cities Almanac for September 25th:

The average MSP high temperature for this date is 68 degrees F (plus or minus 10 degrees F standard deviation), while the average low is 48 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for September 25th:

MSP records for this date include: highest daily maximum temperature of 91 degrees F in 1920; lowest daily maximum temperature of 44 degrees F in 1926; lowest daily minimum temperature of 31 degrees F in 1926; highest daily minimum temperature of 68 degrees F in 1908; record precipitation of 1.34 inches in 1934. No snowfall has been reported on this date.

Average dew point for September 25th is 45°F; the maximum dew point on this date is 70°F in 1903; and the minimum dew point on this date is 14°F in 1926.

All-time state records for September 25th:

The state record high temperature for this date is 95 degrees F at Angus (Polk County) in 1938. The state record low temperature for this date is 11 degrees F at Alborn (St Louis County) in 1947. The state record precipitation for this date is 8.64 inches at Winnebago (Faribault County) in 2005. Record snowfall for this date is 6.5 inches at Fosston (Polk County) in 1912.

Past Weather Features:

A significant early season snowstorm abruptly brought an end to the agricultural season in northwestern Minnesota over September 24-25, 1912. Many areas reported from 2 to 6 inches of snow with temperatures falling into the 20s and 30s F.

Frigid temperatures dominated Minnesota on September 25, 1926. Most places reported morning low temperatures in the 20s F. Daytime high temperatures only climbed into the 40s F, and International Falls had a record cold maximum temperature of just 35°F.

September 25, 1938 was the warmest in state history with most communities seeing afternoon temperatures in the 80s F. At least a dozen climate stations surpassed 90°F.


Partly cloudy Saturday and still warmer than normal most places. Increasing chances for rain on Saturday night and Sunday, then cooler for Sunday through Thursday with chances for showers especially in northern areas. A chance for some frost by Wednesday and Thursday next week in many areas of the state.

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weaa said…
Great info