The featured chart presents a histogram of reported daily high and low temperatures on 16 August for all long term climate sites in Iowa over the period of record for each site. A simple normal distribution line is plotted based on the computed mean and standard deviation. There are a few interesting quirks to point out. First, the low and high temperature populations both show increased frequencies just above the mean value. Rewording, the mode of each is a number of degrees warmer than the mean. The reason likely has to do with increased humidity levels decreasing temperature variability. When humidity levels drop though, then more cooler values occur and the mean gets pulled down. There's an additional bump in frequency at values just above 100 degrees. This likely is due to a preferred threshold for reporting temperatures back in the old days and a concentration of these temperatures at those levels when August conditions create very hot days. The forecast today will fit the mode of both distributions pretty closely and much warmer temperatures are in the forecast for the weekend! Summer is not done yet!

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