Toasty summer: Midwest running warmer than average this summer
Temperatures and growing degree days running above average
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It’s not our imagination.
The summer of 2020 has been warm across the Upper Midwest. Temperatures in the Twin Cities ran 4 degrees warmer than average for the month of June. July is running about 2.5 degrees warmer than average overall.
And data from the Midwest Regional Climate Center shows most of the Midwest and Great Lakes running warm this month.
Growing degree days
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Gorwing degree days measure how much heat energy is available for crops. Here’s an explanation of growing degree days from the University of Illinois.
To calculate GDDs, you must first find the mean temperature for the day. The mean temperature is found by adding together the high and low temperatures for the day and dividing by two. If the mean temperature is at or below TBASE, then the Growing Degree Day value is zero. If the mean temperature is above TBASE, then the Growing Degree Day amount equals the mean temperature minus TBASE. For example, if the mean temperature was 75° F, then the GDD amount equals 10 for a TBASE of 65° F. You can think of Growing Degree Days as similar to Cooling Degree Days, only the base temperature can be something besides 65° F.
You can see that since April 1st there are a significant surplus of growing degree days compared to average.
So both crops and humans are feeling the effects of a warmer than average summer in the Midwest this year.