Muggy conditions were again in Iowa on Thursday with dew point temperatures reaching the lower 70s. How common are such high dew points? The featured chart displays a two dimensional histogram of 70+ degree dew point reports for Des Moines. As you may have suspected, these events are mostly limited to the summer months. Frequencies start to increase around the second week of June and last into the end of August and even September. It is interesting to note the increased frequencies during the afternoon hours in the summer time. Our intensive agriculture in the state is a large source of water vapor in the lower atmosphere during this time and help to boost dew points.

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