Skip to main content

First Half of September: Warm and Highly Variable Rainfall

First Half of September: Warm and Highly Variable Rainfall

Following the 2nd hottest summer in state history, it should not be surprising that temperatures have been above normal during the first half of September, though only modestly by 1 to 3 degrees F. A few places in the state have reported 80°F or higher on two or three days, while Thursday, September 16th brought the first 90°F readings of the month. On Thursday at least 18 climate stations reported a high temperature of 90°F or higher, topped by 95°F at Milan (Chippewa County). A few places like Embarrass, Brimson, and Hibbing have reported frost already this month, but frost has been absent across most of the state.

Rainfall so far in September has been surplus in many western counties, including Pipestone, Stevens, Traverse, Grant, and Lac Qui Parle, all of which have recorded over 2 inches so far. But much of the state is only near normal or below normal in rainfall so far. The big rainfall event for some was on September 3rd when some climate stations reported record daily amounts, including:
2.12 inches at Browns Valley
2.10 inches at Dawson
2.00 inches at Pipestone
1.95 inches at Wheaton
1.67 inches at Marshall

During Thursday afternoon and evening a strong cold front brought high winds, thunderstorm rain and hail to many parts of central and northern Minnesota. Some areas reported between a half inch and an inch of rainfall from the rapidly moving thunderstorms. A few spots reported record daily rainfall from these thunderstorms, including Mora (1.74”), Babbitt (1.44”), Wold Ridge Environmental Learning Center (1.51”), and Embarrass (1.20”). Many areas reported wind gusts from 45 to 65 mph. MSP airport, along with climate stations in Murray and Brown Counties reported wind gusts over 60 mph, and some areas of the state reported uprooted trees. Hail from 2 to 2.5 inches in diameter was reported from Morrison County in the central part of the state.

Despite the rainfall for some areas the area of Minnesota affected by Severe to Exception Drought has remained the same, about 59 percent, much of it located across the northern third of the state.

Weekly Weather Potpourri:

NOAA reported this week that the global climate summary for August of 2021 showed it to be the 6th warmest in history back to 1880. Nine of the ten warmest months of August globally have occurred since 2009.

The NOAA Climate Prediction Center outlook for the month of October favors warmer than normal conditions to prevail across Minnesota. No surprise there. But somewhat surprising is that the models favor a wetter than normal month of October for most of the state, a hopeful sign for some mitigation of the drought situation.

A new study in the journal Nature documents how the 2019-2020 wildfires in Australia produced some significant anomalous phytoplankton blooms (algal) in the Southern Ocean downwind from the fires. Significant macronutrients and trace metals were carried in the smoke and ash for many hundreds of miles.

MPR listener question:

My uncle and aunt just moved to Minnesota from Hawaii last month. They were asking me how cold it gets in September. What are the record lows for this month?


Not sure about what Minnesota geography to use for the answer. If they moved to the Twin Cities the typical low temperatures are in the 40s and 50s F during September, but it has been as cold as 26°F on several occasions. Statewide the lows typically range from the upper 30s to low 50s F, but have been as low as just 10°F (at Ada on September 22, 1974 and at Montevideo on September 30, 1930).

Twin Cities Almanac for September 17th:

The average MSP high temperature for this date is 73 degrees F (plus or minus 10 degrees F standard deviation), while the average low is 54 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for September 17th:

MSP records for this date: highest daily maximum temperature of 96 degrees F in 1895; lowest daily maximum temperature of 47 degrees F in 1918; lowest daily minimum temperature of 34 degrees F in 1943; highest daily minimum temperature of 75 degrees F in 1948; record precipitation of 2.37 inches in 2015. No snowfall has occurred on this date.

Average dew point for September 17th is 52°F; the maximum dew point on this date is 71°F in 1963; and the minimum dew point on this date is 26 degrees F in 1929.

All-time state records for September 17th:

The state record high temperature for this date is 105 degrees F at Granite Falls (Yellow Medicine County) in 1895. The state record low temperature for this date is 14 degrees F at Mahnomen (Mahnomen County) in 1929. The state record precipitation for this date is 4.02 inches at Two Harbors (Lake County) in 1955. No snowfall on this date.

Past Weather Features:

The warmest September 17th in state history was a long time ago, 1895 when over half of the state saw afternoon temperatures reach the 90s F. Portions of Renville, Lyon, McLeod, Chippewa, and Yellow Medicine Counties saw the temperature exceed 100°F.

The coldest September 17th was in 1929. Clear skies, light winds, and low humidity brought widespread frosts to much of the state. Temperatures fell into the 20s F in many central and northern counties. The afternoon high at Babbitt (St Louis County) only reached 43°F.

Thunderstorms brought heavy rains to many northeastern parts of the state over September 16-17, 1955. Many areas saw 3 to 4 inches of rain which flooded some streets and highways in both Duluth and Two Harbors. Large hail was reported as well in some areas.


Mostly sunny with warming temperatures over the weekend. Many parts of the state will see temperatures in the mid to upper 80s F by Sunday afternoon. Chance for showers and thunderstorms later in the day on Sunday. Continued warm on Monday but with an increasing chance for showers and thunderstorms. Cooler by the middle of next week with below normal temperatures through the balance of the week.

Print Friendly and PDF


WannaskaWriter said…
I live in Palmville Township, Roseau County. Along with many areas of the state, we've been hard hit with the on-going drought of 2021, watching as much needed precipitation went north or east of us. Crops south of Roseau and east toward Warroad and Lake of The Woods look pretty good; not so, here along our southern border with Marshall County.

Even so, our trees here are over-producing seeds: For instance, there’s an abundance of acorns from our bur oaks, seemingly tons of winged seeds from green ash and ginnala maple as well as astonishing clusters of seed cones on our northern white cedar. Only a few trees in our fields show any kind of distress, and in fact others put on some real height. I wonder if they're preparing for something unknown to us,