The featured map is from a recently added "autoplot" that allows plotting the percentage of years over a given period of days that had at least one day below or above some threshold. In this case, the map shows the frequency of having at least one daily low temperature below 20°F between 10 April an 31 May. There is certainly a north to south gradient to be found with some locations near one third and others in far southeastern Iowa closer to zero. The near term forecast has plenty of warm weather and little in the way of cold temperatures, but there is still plenty of time yet for sub freezing temperatures. In fact, you can follow the generate this chart link and re-generate this chart but for a threshold of 32°F and find out!

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