While autumn began like summer and ended like winter, the state experienced more heat than cold during the season, which tied the record for Wisconsin’s warmest fall. Autumn was also more dry than wet, especially until drought-busting rains finally arrived during November.
Summer Slow to Leave
Although summer heat often lingers into September, this year the persistence was exceptional in lasting off-and-on throughout the fall. All three autumn months were much warmer than average in Wisconsin — third warmest September, 12th warmest October, and seventh warmest November — tying with autumn 2016 for the state’s warmest on record since 1895. The three-month statewide average of 51.5 degrees was an impressive 4.9 degrees above normal (Figure 1).
The northern half of the state (northwestern Wisconsin in particular) experienced the most anomalous temperatures, with 24 counties experiencing their warmest fall on record. For example, Douglas County averaged 49.6 degrees this fall, which was 5.7 degrees warmer than its normal 43.9 degrees.
Thanks to plentiful sunshine during September and October, the season’s daily high temperatures stood out as the highest autumn average on record (62.7 degrees), compared with the season’s fourth highest average of daily low temperatures (Figure 2). In fact, every Wisconsin county except Vernon saw their warmest September through November maximum temperatures, and 10 counties — all in northern Wisconsin — fell one rank short of seeing their warmest minimum temperatures.
Dry, Dry, then Wet
Most of autumn was very dry in Wisconsin, as persistent high pressure blocked rain from reaching the state during the first two months of the season. As a matter of fact, this year’s September through October period was the state’s sixth driest on record, with a statewide average of 3.12 inches that fell in those 60 days.
In November, the state flipped into a wet pattern (11th wettest) to temper the overall autumn dryness, such that most (52 percent) of the season’s total precipitation fell just in the final month. Wisconsin ended up finishing the season with a statewide average of 6.54 inches, which was 2.05 inches below normal and the 33rd driest fall on record (Figure 3).
The dry conditions were particularly harsh in north and northwest Wisconsin, where many counties ranked among the top third driest falls on record. Douglas, Dunn, and St. Croix Counties, for example, endured their ninth driest fall, with each seeing just 50 percent of their normal season precipitation.
However, a different story played out across the southern part of the state. From southwestern Wisconsin to Green Bay, the season’s precipitation was closer to normal, thanks to a period of heavy rain that fell between the tail end of October and the first week of November. This brief but intense stretch brought approximately three and a half inches of rain, helping to boost totals and provide some relief to an otherwise dry season.
Record Drought Extent Reached
Autumn was topsy-turvy for drought in Wisconsin, thanks to the highly variable rainfall. Because of a wet summer, the fall season began with none of Wisconsin in drought and only 13 percent of the state abnormally dry (Figure 4).
But the extreme dryness during September and October led to all of Wisconsin falling into drought (D1 and D2) by late October for the first time in the history of the U.S. Drought Monitor (Figure 5).
Fortunately, a wet November greatly eased the aridity and enabled most of Wisconsin (56 percent) to shift out of drought classification when the season ended. The rest of the state remained in moderate or severe drought when the calendar flipped to meteorological winter in December (Figure 6).
