Between Thursday and Sunday in Chicago more than eight inches of rain fell on the metro area. Midway through the month we were already on the cusp of the wettest May ever according to the Chicago Tribune:
Several reached the damaging major flood stage. More than 8 inches of rain fell from Thursday through Sunday in the Chicago area, according to the National Weather Service, putting this May on the cusp of becoming the wettest ever on record for the city.
The deluge led the Chicago River to swell to its highest level in more than 60 years, swamping the downtown Riverwalk.