Labor Day was quite warm with high temperatures well into the 90s and even a few 100 degree observations found in the state. Ample sunshine along with dry surface conditions allowed temperatures to quickly warm during the day. The lack of clouds is the focus of today's feature plot showing the frequency of having overcast sky conditions reported by air temperature for Des Moines during September. A clear relationship is shown with both very warm and very cool temperatures having the least amount of overcast clouds present. For the warm temperatures, sunshine is needed to help push temperatures well above average. For the cool temperatures, clear skies allow for more efficient cooling and cooler temperatures. So clouds effectively help to moderate temperatures and temperatures with the highest frequencies are found at approximate values of common near surface soil temperatures for this time of year.

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