Numbers Prove May 2017 in Sioux Falls Was Chilly
From September 2015 to April 2017, each calendar month has recorded an above average temperature in Sioux Falls. May 2017 has broken that 20-month stretch.
Initially, that record looked almost certain to stay intact through the first sixteen days of the month. Twelve of the first 16 days had daytime highs running hot. During the night, low temps were close to average early in the month.
The next 15 days were sharply colder with the temperature balance shifting to the blue side for good on Saturday May 27. A single rise to 75 on May 28 was not enough to counteract the chill.
As a reminder, the formula for determining average temperature for the month is adding each high and low temperature then dividing by double the number of days in the month.
Average compiled high temps for May = 2165 May 2017 Actual = 2154
Average compiled low temps for May = 1433 May 2017 Actual = 1415
Combined average temperature = 3598 May 2017 Actual = 3569
Divide by double number of days in month (62) = 58.03 May 2017 Actual = 57.56
A cooler than normal month is nothing new. The length it took for such a month to return to Sioux Falls is the bigger point.