Chicago weather: Cook County to remain under flash flood warning until late Sunday afternoon

A flash flood warning for Cook County — which had been in effect much of Sunday afternoon as more than 3 inches of rain fell locally — was allowed to expire at 3 p.m. as both the threat of damage, and the water itself, subsided.

The warning went into effect at 11:54 a.m., when a Doppler radar detected thunderstorms across southeastern Cook County and central Will County. At that time, as much as 2.5 inches of rain already had fallen and another 1 to 2 inches had been forecast, according to the weather service website.

“Flash flooding is ongoing or expected to begin shortly,” the warning read.

Oak Forest, Frankfort, Dolton, Chicago Heights, Tinley Park and Homewood were among the municipalities under the flash flood warning, according to forecasters.

In a Sunday morning Twitter post, the weather service said “multiple rounds of storms” increased the risk of flash flooding, as a rainfall rate of 2 to 3 inches per hour had been expected. Small creeks and streams, urban areas, highways, streets and low-lying areas were particularly vulnerable, it said.

“I think the key message would be if you happen to see any flooding on roadways, turn around and don’t drive through it,” said Jake Petr, a meteorologist with the weather service’s Romeoville office.

Rainfall was moving east across northern and northwestern Illinois during the afternoon, with the possibility of some lightning strikes.

Cook County residents can expect more rainfall Monday, followed by several days of cloudy skies and temperatures in the 70s and 80s through Friday, forecasters said.

For more detailed forecast information, visit the Tribune’s weather page.