Temperatures have been mild overnight with much of the state at or above freezing at 5 AM this morning. The featured chart presents the frequency by hour for the temperature being at or above 32°F during December for Des Moines. The diurnal signal is clear with the lowest frequencies happening during the early morning hours before whatever meager daytime heating that does exist can start to raise near surface air temperatures. For most hours of the day, being below freezing is more common than not. The overnight frequencies are all around 1/4 of the time or higher, so having such temperatures isn't necessarily all that rare for this time of the year.

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Tags:   dec