One of the negative things about the cold season in Iowa is the increased number of gloomy days. The gloomy days being a result of decreased sunshine intensity and overcast cloudiness happening more frequently and at lower heights. The featured chart illustrates this by presenting a 2D histogram of reported overcast conditions by week of the year and height above ground level. The major caveat to charts like these are instrumentation and reporting quirks with how cloud levels are reported. This chart is for Davenport and you see no data above about 12 thousand feet. Overcast conditions have occurred above that level, but the instrumentation is unable to "see" it. Those issues aside, the difference between the warm and cold half of the year is readily apparent with much elevated frequencies happening during the cold season. As lower atmosphere mixing decreases due to less solar input, moisture (clouds) can become trapped/persistent near the surface.

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