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A winter storm that could drop four to eight inches of snow in the Chicago area has prompted airlines to cancel more than 200 flights and sent snowplows to the streets for the Thursday evening rush.

Freezing rain is changing to snow Thursday afternoon and one to four inches of accumulation is possible in the city by midnight, according to the National Weather Service.

The Illinois Tollway deployed its full fleet of 182 plows Thursday afternoon, according to a release. The plows will patrol the 286 miles of toll road in 12 counties in northern Illinois.

Airlines canceled more than 200 flights at O'Hare International Airport, where delays are averaging 20 minutes, according to the city Department of Aviation. Midway International Airport is reporting normal operations as of 3:30 p.m.

The weather service has issued a winter weather advisory for the Chicago area until 9 p.m. A winter storm warning has been issued for Lake and McHenry counties, where the heaviest snow is expected.

Snow could accumulate at an inch per hour at times and two to four inches total are likely north of I-88, the weather service said. Four to eight inches possible across Lake and McHenry counties.

Once the storm passes Thursday night, the next chance of precipitation will be Sunday, the weather service says. But by then, the highs will be in the lower 40s and the precipitation will be all rain.

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