Your location in Iowa on Tuesday likely made a big difference of your opinion of the weather! A staled out surface boundary split the state nearly in half with the southeastern half stuck with mid-summer quality steamy heat and the northwestern half experiencing Chamber of Commerce weather. The Des Moines airport was in the former half. The featured chart presents a climatology of dew point temperature by air temperature during May. The blue line represents an average dew point as computed via a mixing ratio calculation with the black line showing the associated relative humidity with that calculated dew point value. Percentile ranges are shown as well to give a handle on the distribution. To add more content to the plot, actual observations from Tuesday are included as well. The dew points over 70 are certainly at the top end of the range for the month of May. The chart nicely shows an inflection point at about 70 degrees, which is a sign of warming above that level typically lowering humidity levels due to vertical mixing and other processes. It is rather exceptional to see such high humidities this time of year.

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Tags:   dewpoint