Sep 20, 2018
A nearly stationary west to east frontal boundary was located across Nebraska and Iowa for several days. With an extremely moist atmosphere featuring near record precipitable water in place, several weak disturbances resulted in prolific rainfall from 3 to as much as 10 inches. Sioux Falls, South Dakota established a new 24-hour rainfall record of 5.07 ending 1600LST September 20, as well as daily records for both September 19 and 20.
Source: NOAA National Weather Service Storm Events Database (event 782582). Narrative written by NWS staff at the time of the event.
This event is one of many recorded floods in Union County. See the full FEMA flood zone map, NFIP claim totals, and disaster history for the area.