TimeOut Chicago: Record rainfall caused flooding throughout the city, most noticeably on the banks of the Chicago River.

According to the National Weather Service, nearly eight inches of rain fell at O'Hare Airport over the past four days, with 3.53 inches falling on Thursday, May 14—the wettest day of May in Chicago on record. With rain continuing to fall throughout the day on Sunday, Cook County was put under a flash flood warning (which continues until 1pm on Monday, May 18) as rivers and sewers throughout the region began to overflow under the deluge of precipitation.

In Chicago, many basements and streets were at least partially underwater on Sunday, but the flooding was most visible in the Loop, where the Chicago River spilled over onto the Riverwalk (which was already closed to the public by Mayor Lori Lightfoot) and into Lower Wacker Drive. The Chicago Fire Department deployed inflatable watercraft to rescue people trapped on Lower Wacker by the rising water, getting at least six people to safety according to the department's Twitter account. The rising water also made its way into a subterranean ComEd substation in the Loop, knocking out power to Willis Tower, according to a Chicago Tribune report.

While the Chicago River typically flows inland from Lake Michigan, thanks to a civil engineering project that Illinois undertook to reserve the river's flow in the late 1800s, the Metropolitan Water Reclamation District of Greater Chicago reconfigured pumping stations to allow the river to flow into Lake Michigan late last night.

With additional rain in the forecast this evening and throughout Memorial Day weekend, this May is likely to be the wettest on record in Chicago, beating last year's record of 8.25 inches in May. Flooding could continue throughout the week, so if you encounter a pool of water that looks exceedingly deep, it's best not to attempt to walk (or drive) through it.

Take a look at some scenes from the Chicago Riverwalk and Lower Wacker Drive, documenting just how much water poured into Chicago over the weekend.