Wet September 2010


Overview:

A preliminary analysis of Minnesota's rainfall totals indicates that September 2010 was the wettest September in Minnesota's modern climate record. The state-average September rainfall total was 6.47 inches, topping the previous high of 6.20 inches from 1900. Here are the ten wettest Septembers (using state-averaged data) from a rainfall database that extends back to 1891:

yearSeptember total (inches)
20106.47
19006.20
19656.10
20045.79
19865.65
19265.32
19035.30
19415.13
19914.92

The state-averaged monthly rainfall total of 6.47 inches incorporates data from throughout the state. By far, the biggest contribution to the new state-wide record comes from the southern one-third of Minnesota where monthly totals in excess of ten inches were common. For much of southern Minnesota, September rainfall totals exceeded the historical average by five or more inches. When compared with other Septembers in the historical record, September 2010 rainfall ranked near or above all-time high values for nearly every location in the southern three tiers of Minnesota counties.

The wet September came on the heels of a soggy summer. From June 2 through August 31, rainfall in many Minnesota counties topped historical averages by two to six inches. Summer rainfall in a some southern and east central Minnesota locales exceeded the historical average by six to eight inches. September continued the wet pattern with heavy rain and severe storms on September 2, an event which dumped up to five inches of rain in Lincoln County. The extraordinary rain event on September 22-23 assured that Minnesota would have, on average, the most rain for any September on record. There have been some wet Septembers in recent years including 2005 and 2004, especially over southern Minnesota.


Preliminary September 2010 rainfall precipitation maps:


total precipitation: September 1, 2010 - September 27, 2010 total precipitation departure: September 1, 2010 - September 27, 2010 precipitation rank: September 1, 2010 - September 27, 2010