Humidity levels on Monday were rather meager with dew points in the teens and even single digits Fahrenheit. Low humidities have been common so far this year as shown by the featured chart displaying daily relative humidity (RH) climatology, range of observed values and the frequency of having a daily min value below 25% (red line) for Des Moines. Qualitatively, almost all of the days shown have had a minimum RH value below the simple climatology. RH values below 25 percent are most common during April, which is a time of increasing solar heating and limited plant transpiration activity. Such low humidities lead to wild fire concerns as dry air helps to dry out the land surface and dead vegetation. Such conditions are often coincident with stronger near surface winds as dry air heats more rapidly and promotes mixing of warmer and often drier air aloft to the surface.

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