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September Climate Update

September Climate Update:

Since last Saturday we have seen some of the warmest weather since early August prevail across much of the state. Over 100 climate stations have reported daytime highs above 80°F this week and in western Minnesota places like Windom, Marshall, Browns Valley, Milan, and Redwood Falls saw temperatures of 90° or higher. Of further note is that warm nights have prevailed as well, with seven climate stations reporting new record high minimum temperatures including 71°F at Canby, 69°F at Lamberton, and 66°F at Ada in the early morning of the 17th.

Minnesota farmers were happy to see the return of warmer than normal weather this week as it was needed to speed up corn development towards maturity. Most of the state corn crop is in the dough or dent state (condition of the kernels) and needs some more time to mature and dry down before harvest. The warm temperatures also help soybeans turn color and drop leaves this week as they progress to maturity.

It was good to see that rainfall abated for a few days as many areas of the state have already seen twice normal rainfall totals for the month. Normal rainfall for September typically ranges from 2.25 inches to 3.50 inches around the state, and so far over 40 Minnesota climate stations have reported 6 inches or more of rainfall this month. With 9.40 inches Pipestone has already reported its 3rd wettest September in history, and with 8.19 inches Preston September rainfall ranks 5th wettest historically. For the year-to-date Rochester has received 44.05” of precipitation which is already a new annual record. Unfortunately, the weather outlook to the end of the month favors above normal precipitation to continue.

Weekly Weather Potpourri:

At 2:50am CDT on Monday, September 23 the sun will be directly over the Earth’s equator marking the autumnal equinox.

The Twin Cities, along with Northfield: Baudette, Bemidji, Center City, Duluth, Grand Marais, Grand Rapids, Moose Lake, Morris, Rochester, St. Joseph, St. Paul, Virginia, Willmar and Winona are hosting activities today in coordination with the Global Climate Strike to raise awareness and demand more aggressive action to respond to climate change and help mitigate it. MPR features an excellent story about this. Kudos to all the organizers of these events and the call for action.

According to the MN-DNR some areas of north-central and northeastern Minnesota are showing over 50 percent color change, while yet a larger share of the state’s northern wooded landscapes are showing 25-50 percent color change. Maples on the uplands of the north shore counties (Lake Superior) are showing orange and reds for this weekend.

Remnants of Tropical Storm Imelda dumped a load of rainfall over eastern Texas and Louisiana this week. There were many reports of flash floods, as well as closed roads and highways. Some climate stations in Jefferson County (where Beaumont and Port Arthur are located) reported 25 to 35 inches of rainfall from the storm. Many people were evacuated due to flooding across Jefferson County. To the east across the border into Louisiana, Lake Charles reported over 21 inches of rain, the most since Hurricane Harvey two years ago.

It was a busy week for tropical storm activity as on Wednesday, September 18th the NOAA – National Hurricane Center was tracking named storms Humberto, Jerry, and Imelda in the Atlantic Basin, as well as Kiko, Mario and Lorena in the Eastern Pacific Basin. Staff from the National Hurricane Center tweeted this combined number of active storms in both basins was believed to tie a modern record from September of 1992. You can read more from the WeatherUnderground.

In this week’s AGU-EOS bulletin, there is an interesting article how scientists from Denmark, Finland, and Norway joined forces to develop a suite of open access tools for climate assessment. Long-term planning and decision-making for societal infrastructure needs to take a changing climate into account. Transportation, energy supply, and water and drainage systems are better managed with this information. Typically, the relevant climate projections include substantial inherent uncertainty, and appropriately accounting for this uncertainty is critical to good decision-making. These scientists are developing tools for assessing this uncertainty.

MPR listener question:

This inquiry comes from our group at the Phat Pheasant Pub in Windom, MN where it has been raining over 8 inches this month. What is the state record for the most ever rainfall in September?


The statewide record for rainfall in September comes from the University of Minnesota Southern Research and Outreach Center at Waseca, MN where they recorded 14.80 inches of rain in September of 1990. Suffice to say their drain tile were running most of the month and it was a difficult harvest.

Twin Cities Almanac for September 20th:

The average MSP high temperature for this date is 70 degrees F (plus or minus 10 degrees F standard deviation), while the average low is 50 degrees F (plus or minus 9 degrees F standard deviation).

MSP Local Records for September 20th:

MSP weather records for this date include: highest daily maximum temperature of 91 degrees F in 1931: lowest daily maximum temperature of 47 degrees F in 1875; lowest daily minimum temperature is 28 degrees F in 1962; highest daily minimum temperature of 75 degrees F in 1895; record precipitation of 1.82 inches in 1902; and there was a trace of snow in 1927.

Average dew point for September 20ths 48 degrees F, with a maximum of 75 degrees F in 1970 and a minimum of 33 degrees F in 1956.

All-time state records for September 20th:

The state record high temperature for this date is 99 degrees F at Fairmont (Martin County) in 1891. The state record low temperature for this date is 14 degrees F at Karlstad (Kittson County) in 1973. State record precipitation for this date is 4.97 inches at Harmony (Fillmore County) in 1983; and record snowfall of 0.4 inches at International Falls (Koochiching County) in 1945.

Past Weather Features:

September 20, 1973 was the coldest in state history with over 100 climate stations reporting frost. In northwestern Minnesota morning low temperatures ranged from 14 to 20°F.

September 19-20, 1983 brought heavy thunderstorms to many areas of the state, especially southeastern counties. Portions of Houston, Mower, and Fillmore Counties reported over 4 inches of rain with widespread flooding and closure of roads. Harmony reported 5 inches of rain.

September 19-20 brought an autumn Heat Wave with temperatures soaring to 90°F or higher in over 80 Minnesota communities. Tower, MN reported frost that morning with a reading of 32°F, then the afternoon temperature climbed all the way up to 86°F.


Saturday will be breezy with a chance for showers and thunderstorms, especially eastern and southern sections of the state. Sunday and Monday look dry, but then another chance for showers by Tuesday through Thursday. The temperature pattern will be falling during the period and they will be closer to normal by the middle of next week.

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