The warmest temperatures so far this year are expected today with morning clouds and fog eventually giving way to sunshine and temperatures close to 80 degrees! Does having such warm temperatures in April require the help of the sunshine? The featured chart presents the frequency of having overcast (cloudy) conditions by a given air temperature during April based on hourly data from the Des Moines Airport. There certainly appears to be a relationship with increasingly warmer temperature coincident with decreasing frequency of overcast clouds. Conversely, the same relationship exists with very cold temperatures as well. At cold temperatures, the absence of clouds allows for higher rates of radiational cooling. At warm temperatures, fewer clouds allow for more insolation (heating of the ground) and likely better lower atmosphere mixing to transport warmer air aloft to the surface. Enjoy this weather as cooler temperatures are coming!

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