September is not only an important month for harvesting crops in Minnesota, but it also marks the beginning of the fall recharge season in terms of soil moisture.

Studies have shown that a large fraction of the precipitation that falls during the September-to-November period goes into soil moisture storage, replenishing what was lost during the cropping season.

In Minnesota climate history, two Septembers stand out as the driest ever, 1952 and 2012. In both years, the statewide average rainfall was only 0.61 inch, about 2.5 inches less than average. Many areas of the state had only one to three days of measurable rainfall during those Septembers. Fire danger across the state was amplified, and crops dried down for harvest extremely fast.

Thirty-five long-term climate stations report September 1952 as the driest in history. Some of these are in prime agricultural counties of Minnesota, including Faribault with 0.26 inch, St Cloud with 0.07 inch, Preston with 0.33 inch, Winsted with 0.21 inch, and Bird Island with 0.33 inch.

As a result of the very dry September, much of the state’s corn crop was already harvested by the end of the month.

Climate stations disagree about which year was driest

More than 40 long-term climate stations reported September 2012 as the driest in history. Again, many of these stations are in prime agricultural regions of Minnesota. Some of these included Olivia with 0.06 inch, Windom with 0.3 inch, Morris with 0.03 inch, Litchfield with 0.2 inch, and Alexandria with 0.11 inch.

The dry September across Minnesota was widespread and contributed to an early harvest season. The dry pattern continued until December, which was wetter than normal. Then a wet spring in 2013 helped alleviate fears of drought carrying over into the next growing season.

In viewing the September rainfall statistics for the state since 2012, six of the nine years have brought normal or above-normal rainfall during the month.

With a drier-than-normal growing season in 2022, for many areas of the state it will be valuable to see a wetter-than-normal September occur again this year — from the standpoint of recharging our agricultural soils.

Seeley is an Extension professor emeritus of meteorology and climatology at the University of Minnesota.