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Warm, then wet this week

Warm Nights and High Dew Points:

This week brought another round of warm temperatures to Minnesota, but more noteworthy for warm nights rather than hot days.  Several climate stations reported new record high minimum temperatures on September 15 and 16  (Tue-Wed) this week.  On September 15 new record high minimum temperatures were reported from Park Rapids (65F), Alexandria (66F), and Fargo, ND (69F).  Then on September 16th even more new records were reported from International Falls (66F), Duluth (67F), Detroit Lakes (73F), Itasca State Park (69F), Cass Lake (71F), Ely (69F), Little Falls (71F), Mora (71F), and Minnesota City (70F).

The warm weather also brought with it higher dew points which reached into the 70s F on the 16th and 17th.  The precipitable water measured in the Chanhassen balloon sounding on September 17th was a record amount at 1.91 inches, a remarkably large number for the month of September.  This helped fuel some thunderstorm activity that dropped significant rainfall in many places.  Many observers reported from 0.50 inches to 1.50 inches of rain, and Stillwater received between 2.50 and 3.00 inches.  Mahtomedi reported 3.43 inches, and MSP airport set a new daily record with 2.37 inches.  In some areas the National Weather Service put out flash flood warnings.

September has been tracking warm across the state through the first 17 days of the month, averaging 5 to 8 degrees F warmer than normal. The outlook continues to favor warmer and wetter than normal conditions throughout the rest of September.

Farewell to Susan Weller:

The University of Minnesota will miss Dr. Susan Weller, Director of the Bell Museum and Professor of Entomology since 2008.  She has been a champion advocate for science education and the Bell Museum for many years.  She helped lead the effort to secure state funding for the New Bell Museum and Planetarium which will be located on the St Paul Campus, and she enriched the life of the community by offering more outreach educational programs from the museum.  I want to wish her all the best in her new position as Director of the University of Nebraska State Museum of Natural History.

Weekly Weather Potpourri:

The United Kingdom Met Office and NOAA reported this week that Arctic sea ice during the 2015 summer season dropped to the 4th lowest level of ice extent since satellite measurements began in 1979.  This continues a dramatic downward trend. 

According to data analysis by NASA scientists this past summer season (June-August) was the hottest of record for the Northern Hemisphere.  This is coherent with the strong El Nino pattern that is in place across the Pacific Ocean, and combines with warming trends in the other months of the year to suggest that 2015 may end up being the warmest year globally over the period 1880-2015.   

NOAA also reported this week on the severity of the California drought.  The 4-year drought has built up a very large precipitation deficit that will likely take years to erase. Some areas of the state need nearly 300 percent of normal precipitation to get back to pre-drought conditions.   

Typhoon Krovanh gained strength in the Western Pacific Ocean this week, southeast of Japan.  It was producing winds up to 130 mph and sea wave heights of 35-40 feet.  The storm was expected to remain out to sea and not directly affect the island nation of Japan.

MPR Listener Question:

At Bridge Club the other night our friends who recently moved to Minnesota from Kentucky asked what the maximum snowfall was in the month of September.  We did not know, so we thought we would ask you?


The most snowfall ever received in the Twin Cities during the month of September was 1.7 inches in 1942.  Of course it did not last long.  The most September snowfall on a statewide basis was 16.7 inches at Milaca in 1905, a rather frightening value!

Twin Cities Almanac for September 18th:

 The average MSP high temperature for this date is 71 degrees F (plus or minus 10 degrees F standard deviation), while the average low is 51 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for September 18th:

MSP weather records for this date include: highest daily maximum temperature of 93 degrees F in 1891; lowest daily maximum temperature of 47 degrees F in 1991: lowest daily minimum temperature is 32 degrees F in 1929; highest daily minimum temperature of 71 F in 1955; record precipitation of 3.75 inches 1905; and no snowfall has been recorded on this date.

Average dew point for September 18th is 52 degrees F, with a maximum of 73 degrees F in 1947 and a minimum of 23 degrees F in 1929.

All-time state records for September 18th:

The state record high temperature for this date is 100 degrees F at Montevideo (Chippewa County) in 1891. The state record low temperature for this date is 12 degrees F at Littlefork (Koochiching County) in 1929.  State record precipitation for this date is 7.25 inches at Albert Lea (Freeborn County) in 1926; and record snowfall is 2.4 inches at Duluth (St Louis County) in 1991.  

Past Weather Features:

The warmest September 18th on a statewide basis occurred in 1891.  Minnesota was dominated by a late season Heat Wave over September 16-24 pushing temperatures into the 90s F just about everywhere in the state. The mercury reached 100F at Montevideo achieving an all-time high temperature record for the date.

Strong thunderstorms brought heavy rains to many parts of the state over September 17-18, 1926. Several observers reported over 3 inches, while Mankato and St Peter received over 4 inches, and Albert Lea over 7 inches.  Crop harvesting was delayed for many days. It proved to be one of the wettest Septembers in Minnesota history with several observers reporting over 10 inches for the month.

The 1929 growing season came to an abrupt end with a widespread freeze on September 18th.  Many northern and central Minnesota observers reported low temperatures that morning in the teens F, and it was just 25F as far south as Grand Meadow (Mower County). Temperatures rebounded into the 80s F the next week.

September 18, 1991 brought snow to many parts of Minnesota, albeit just a trace in most cases.  Duluth reported 2.4 inches, while at least a trace of snow was observed as far south as Worthington (Nobles County).


 Sunny, and warm most of the weekend.  Continued warm next week as well with a chance for showers and thunderstorms again by Wednesday and Thursday.

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