The last day of May saw a remarkably cool and drizzly day. The Des Moines ASOS weather sensor reported measurable precipitation for 15 of the 24 hours during the day. The featured chart presents the frequency of hourly reports of precipitation per day of the year based on hourly reports back to 1933. There is a clear signal in this chart showing maximums in precipitation duration in mid spring and late fall. These are common times for large storm systems that could produce precipitation over longer time periods than summer when our weather is dominated by smaller scale storm systems and individual thunderstorms. One caveat to this plot is that our summertime storm systems frequent the state in the late evening into the next morning, so their time totals would be split over two days moreso than other times of the year.

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Tags:   precip   climate