Doppler radar estimated rainfall totals around Sioux Falls, S.D. August 27, 2015. Note that radars often underestimate totals in extreme events like this. (NWS)

A deluge of epic proportions swamped portions of Sioux Falls, South Dakota Thursday evening.

Jay Trobec, the chief meteorologist  for Keloland TV out of Sioux Falls, said thunderstorms unloaded up to 4-8 inches of rain in less than an hour.  The torrential downpours blocked intersections and boats were dispatched on busy streets to assist stranded motorists.

The Associated Press reports that Sioux Falls’ mayor, Mike Huether, called it a “100-year rain.”

Water flooded basements and the Red Cross opened a shelter for those displaced, Keloland TV reports.

 

No injuries were reported.

The extraordinary rains were triggered by a slow-moving front, which drew extremely moist and unstable air out ahead of it into the Plains Thursday.

Here are some unbelievable photos and videos from Twitter: