Warm Nights and High Dew Points:
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:
Weekly Weather Potpourri:
MPR Listener Question:
Twin Cities Almanac for September 18th:
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:
Past Weather Features:
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).