The blizzard with up to 20 inches of snow, 60 mph winds and whiteout condition hit Chicago area on Tuesday, with over 1,300 flights canceled.

The snowstorm started at about 3 o’clock on the afternoon of Tuesday, falling at 1 to 2 inches per hour. The worst is expected to come between 9 p.m. Tuesday and 5 a.m. Wednesday with a snowfall rate of 3 to 4 inches per hour, according to the National Weather Service. Lake effect snow could add an additional 6 inches.

The National Weather Service said that the wind reached up to 50 mph inland and 60 mph near the lake to create whiteout conditions. The blizzard warning for Tuesday and Wednesday forecasts up to 20 inches of snow. Waves at the shoreline of Michigan Lake are expected to reach up to 25 feet.

Classes at Chicago Public Schools and Chicago City Colleges have been canceled for Wednesday due to the snowstorm pounding the city, said Chicago Mayor Daley.

According to Chicago Department of Aviation, more than 1,300 flights have been canceled at O’Hare international airport, and all flight operations have been canceled at Midway, though both airports remain open.

The blizzard is expected to finish on the afternoon of Wednesday.