The Chicago area is expected to see storms that may bring hail and periods of heavy rainfall, just days removed from record-breaking precipitation earlier this week.
A flood advisory is in effect until 10 p.m. for portions of northeast Illinois, including Cook, DuPage and Will counties, according to the National Weather Service.
Pea-sized hail is possible in some storm cells, and rain falling at a rate of 1 to 2 inches per hour can be expected in some of the affected areas. Winds up to 50 mph are also possible.
The advisory means minor flooding along waterways and other poor drainage areas is imminent or may already be occurring, NWS said. This is because some of the area is still saturated from the massive downpours Sunday.
By 10 p.m., Midway International Airport saw more than an inch and a half of rain, meteorologists said.
Some parts of the Chicago area saw up to 9 inches during the storm that caused widespread flash flooding and delayed the inaugural NASCAR Grant Park 220 Street Race, the NWS reported.
The rains were heavy enough to cause the Chicago River to swell and flood parts of the River Walk. To ease the flooding, the Metropolitan Water Reclamation District of Greater Chicago made the decision to release floodwater collected in the system and reverse the flow of the river toward Lake Michigan.
The MWRD does this by opening lock gates near Navy Pier that separate the lake waters from river waters, allowing the river to flow into the lake. It is a step that isn’t taken often, partly because allowing untreated flood water to flow into the lake leads to pollution.
After the reversal due to Sunday’s storms, swimming bans were put in place because of water quality concerns.
There is also a slight chance of showers and thunderstorms in the Chicago area before 7 a.m. Thursday, the NWS said.
