VIDEO: Torrential rain forces city to reverse flow of the Chicago River back into Lake Michigan

Breaking news out of Chicago where a flash flood warning is in effect as thunderstorms pass through the area:

A slow moving band of heavy thunderstorms continues to move northeastward across the Chicago metro and areas along and east of I-55. 1.5 to 2 inches of rain has fallen in the last hour. Flash flooding may develop near the IL/IN border and northwest IN over the next 1-3 hours. pic.twitter.com/x0faOAwIh5

— NWS Chicago (@NWSChicago) May 18, 2020

There’s so much rain that the city was forced to reverse the flow of the Chicago River back into Lake Michigan:

We have reversed the flow of the Chicago Area Waterway system to Lake Michigan at the Wilmette Pumping Station and at the Chicago River Controlling Works downtown to prevent overbank flooding. https://t.co/PC0N7kjCfU

— MWRD (@MWRDGC) May 18, 2020

There are several factors we consider when determining to release floodwater to the lake, including the rate the river water level is rising at each lakefront control location, whether the rainfall intensity is continuing or decreasing, and the storm conditions on the radar.

— MWRD (@MWRDGC) May 18, 2020

We will continue to monitor the situation. During severe weather such as we are experiencing today the safety and health of our residents is our top priority. Please exercise caution and avoid flooded areas.

— MWRD (@MWRDGC) May 18, 2020

Video via NBC’s Mary Ann Ahern:

Witness says “The river is higher than the actual lake and finally the river is moving toward the lake. Don’t think this has ever happened” #ChicagoRiver pic.twitter.com/j1cED1occ5

— Mary Ann Ahern (@MaryAnnAhernNBC) May 18, 2020

The flow of the Chicago River was reversed in 1887 to flow into the Mississippi River instead of emptying into Lake Michigan:

River so high, near Marina City – tables are floating away pic.twitter.com/B3utrwLccz

— Mary Ann Ahern (@MaryAnnAhernNBC) May 18, 2020

The worry now isn’t just pollution, but the invasive Asian Carp getting in Lake Michigan where it could wreak havoc on the ecosystem:

Heavy rains causing boat owners who dock under Marina City to move boats out into the #ChicagoRiver pic.twitter.com/PIdE1U2eYC

— Mary Ann Ahern (@MaryAnnAhernNBC) May 18, 2020

More photos and video from around the area:

I-80 at Ridge Road Flooding, this was taken a little bit ago. #ilwx @NWSChicago

pic – Erin Mroz pic.twitter.com/bdww1qMd2J

— Bob Waszak (@nilwxreports) May 18, 2020

Well. The Flash Flood Warning verified. #Chicago northwest side #JeffersonPark neighborhood

Very rarely has it made it all the way into the garage.

Permission to use with credit@NWSChicago @WGNNews @CherylScottWX @WeatherNation @TWCBreaking pic.twitter.com/wDVVj3vhd6

— WindyCity Weather and News (@WindyCityWxMan) May 18, 2020