Freezing temperatures finally arrived in Iowa on Thursday with some locations, like Ames, even reaching sub 29 degrees. Cloudy conditions on Wednesday gave way to clear skies overnight, which greatly helped the atmosphere cool off. Do skies always need to be clear on the first fall occurrence of sub 29 degree temperatures? The feature chart looks at the hourly sky coverage as reported by the Ames Airport for the 24 hour period before and after the first sub 29 degree temperature event. All but two years since 1996 are indicated to be clear skies at the time of sub 29 (denoted as 0 hour on x axis).

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Tags:   freeze   clouds