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A Taste of Autumn Weather the Second Full Week of September

A Taste of Autumn Weather the Second Full Week of September:

The first taste of autumn weather appeared this week with low relative humidity and overnight temperatures in the 30s and 40s F, especially over September 13-15. Many communities in western and northern Minnesota reported overnight lows in the 30s F and a number of places reported frosts, including:

31°F at Cass Lake (Cass County)
29°F at Brimson (St Louis County)
31°F at Cotton (St Louis County)
29°F at Embarrass (St Louis County)
32°F at Orr (St Louis County)
30°F at Hibbing (St Louis County)

It was 39°F as far south as Lake Wilson (Murray County).

Humidity exhibited a roller coaster pattern this week with readings from 70 to 90 percent earlier in the week, falling off to 20 to 30 percent during the middle of the week. The cooler and drier air was having its effects on native vegetation as the autumn color changes were beginning to appear more abundantly in northern and western counties. Remember you can track fall color changes to help schedule any leaf peeping trips you may plan by going to the MN-DNR Fall Color Finder Web Site.

More heavy doses of rain:

Thursday, September 15 brought some widespread rains to many parts of the state. Lighter amounts, less than half an inch fell in many northern areas, but a number of observers in central and southern Minnesota reported from half an inch to over 1 inch of rainfall. A few southern Minnesota communities reported over 2 inches, and some reported record rainfall amounts for the date, including, New Prague with 1.20 inches, Fairmont with 2.26 inches, and Luverne with 2.32 inches. Sioux Falls, SD reported a new record 3.61 inches for September 15th.

Climate Adaptation: Transforming Awareness Into Action:

I will be offering a one-night program on this topic through the University of Minnesota College of Continuing Education's LearningLife Program on October 5th at at 630 pm on the St Paul Campus. If you are interested about enrollment you can find out more at the LearningLife web site.

Weekly Weather Potpourri:

The National Snow and Ice Center reported this week that the Arctic Sea Ice reached its minimum extent for the season on September 10th, covering an area of only 1.6 million square miles, statistically tied with 2007 as the 2nd lowest of the satellite record. September 17, 2012 remains the lowest measured Arctic sea ice extent at 1.31 million square miles. You can read more about this at the Science Daily web site.

Earlier this week Super Typhoon Meranti caused widespread damage to Taiwan and brought heavy rains to portions of China. It was one of the largest and strongest typhoons ever measured with wind speeds up to 190 mph, rainfall measurements over 15 inches, and wave heights close to 50 feet. Central pressure dropped to 890 mb, or 26.28 inches. Following Meranti is Typhoon Malakas which is forecasted to pass over northern Taiwan this weekend, with wind speeds near 130 mph and wave heights of 35 to 40 feet.

NASA scientists say that a La Nina episode is now unlikely to develop in late 2016 and that Equatorial Pacific Ocean temperatures may hover around normal for the remainder of the year. This will have implications for the winter season outlook, slated to be released next month, covering the November through January period.

MPR listener question:

Someone mentioned the possible snow season in Minnesota starts on September 14th. How is that figured and which places have had snow that early?


The start date of the possible snow season in Minnesota is based on the measurement of 0.3 inches at International Falls on September 14, 1964, the earliest date for measurable snow in the state climate data base. Also on that date communities in Kittson, Roseau, Lake of the Woods, St Louis, Cook, and Lake Counties reported traces of snowfall. A similar storm occurred on September 15, 1916 delivering 0.2 inches at Warroad and a trace amount in several other places, including the Twin Cities. In the Pioneer Era climate records the Twin Cities reported snowfall on September 18, 1863 (amount unknown) and September 23, 1868 (0.2"). So it is possible, but not of the current models show possibilities for snowfall anywhere in the state the rest of this month.

Twin Cities Almanac for September 16th:

The average MSP high temperature for this date is 72 degrees F (plus or minus 9 degrees F standard deviation), while the average low is 52 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for September 16th:

MSP weather records for this date include: highest daily maximum temperature of 94 degrees F in 1955; lowest daily maximum temperature of 50 degrees F in 1916; lowest daily minimum temperature is 38 degrees F in 1873; highest daily minimum temperature of 74 degrees F in 1955; record precipitation of 1.97 inches in 1900; and no snowfall has occurred on this date.

Average dew point for September 16th is 49 degrees F, with a maximum of 71 degrees F in 1997 and a minimum of 29 degrees F in 1959.

All-time state records for September 16th:

The state record high temperature for this date is 101 degrees F at Montevideo (Chippewa County) in 1891. The state record low temperature for this date is 17 degrees F at Karlstad (Kittson County) in 1973. State record precipitation for this date is 7.07 inches at Red Wing (Goodhue County) in 1992 and no measurable snowfall has occurred on this date.

Past Weather Features:

The hottest September 16th in western Minnesota occurred in 1891 when observers there reported daytime temperatures in the 90s F. It reached 101 degrees F at Montevideo (the state record). The mid-September heat wave lasted from the 16th to the 23rd, one of the longest ever for the month.

Another mid-September heat wave prevailed in 1955, lasting from the 16th to the 19th. Over 30 climate stations set daytime maximum temperature records with readings in the 90s F.
For some nighttime lows remained in the 70s F.

September 16-20, 1973 brought widespread frosts to many parts of the state. Low temperatures in the 20s F ended the gardening and growing season as far south as Wabasha County. Much of the corn was not yet mature and suffered damage.

September 16-18, 1992 brought heavy rains to many areas of the state, delaying the harvest season for corn. Portions of southeastern Minnesota reported over 6 inches of rain.
Ten years ago, September 16, 2006 a rapidly formed and relatively short-live tornado struck near Rogers, MN causing damage to many homes and killing a 10-year old girl.


Mostly sunny weekend, with a uptick in temperatures on Sunday and Monday. Increasing chance for showers late Tuesday through Thursday with temperatures near seasonal normals.




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