It appears that the rainfall deficits accumulated over much of Iowa during the dry start to May were made up for over a two day stretch from Monday into Tuesday. Des Moines reported a daily rainfall record of 3.84" on 19 May (Monday), destroying the previous daily record of just 1.14" back in 1937. This total also established a new single day record during the month of May for the site as shown by the featured chart. The chart displays the single day largest precipitation totals by month. The right hand side cartoon just denotes which day of the given month had the record. These extreme precipitation events are in direct relation to the potential amount of water vapor held in the atmosphere. A warmer atmosphere can hold more water, so you find the largest totals when the atmosphere is the warmest (summer time). Additionally, summer events are aided by slower storm movements and more intense lower atmosphere moisture transport by the "Low Level Jet", which allows single storms to dump larger precipitation totals over a smaller area.

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