Winter storm sweeps through Chicago, Central U.S.

A strong winter storm is sweeping through Central United States on Thursday, with temperatures expected to drop 20-30 degrees Fahrenheit within hours.

Snow began to fall in Chicago, the third most populous city in the country, around 11 a.m. local time and grows heavy as the day goes on. Winds of up to 45-50 mph will blow the fine, fluffy snow, thus reducing visibility considerably, creating near-whiteout conditions at times, Chicago Tribune quoted the National Weather Service of Chicago as saying.

A winter weather warning has been issued for the Chicago area Thursday, and is not set to expire until 6 a.m. Saturday.

As of 2 p.m., 536 flights scheduled for Thursday had been canceled at O'Hare International Airport, and 249 had been canceled at Midway, according to the website FlightAware. Airlines companies had already canceled dozens of flights scheduled for Friday out of the two Chicago airports.

The weather also prompted Amtrak to change its schedules including Christmas Day travel. Metra service posted a few modifications for Friday's service and asked commuters to monitor weather conditions before making plans.

Several Chicago area school districts announced closures Thursday. Classes for Chicago Public School students, all after-school, after-care, and out-of-school-time programming have been canceled for Thursday.

Most recreations, museums and attractions in Chicago closed early Thursday, and will remain closed through Friday to Sunday. The Christkindlmarket in the Daley Plaza and Aurora close at 4 p.m. Thursday and will not reopen again this season. The festive market originally plans to close on Christmas Eve.

Warming centers have been opened for those who lack adequate heat. Cook County has opened three courthouse buildings as warming centers. Chicago is operating warming centers throughout the city. Besides, most park district fieldhouses are open as warming shelters.