Trick-or-treaters might want to think about adding boots and a raincoat to their costumes as a record-breaking snowfall moves through the Chicago area on Halloween.

O’Hare International Airport recorded 1.2 inches of snow at 1 p.m. over a 12-hour period, crushing a previous Halloween snowfall record from 2014, when 0.1 inches was recored, according to National Weather Service meteorologist Mark Ratzer.

The heaviest snow is expected to fall in Chicago during the evening commute, Ratzer said. The weather service’s winter weather advisory expires at 6 p.m. in Cook County.

“It’s going to continue to snow lightly through the evening, although it’ll be lighter than we’re seeing now,” Ratzer said at 3 p.m.

The weather service was recording visibility as low as a half mile is some areas.

Snowfall totals will be lowest near the lake, where only a half inch of snow is expected to fall.

By the mid-afternoon, airlines had canceled more than 300 flights, and more than 1,000 were delayed at O’Hare and Midway airports, the Chicago Department of Aviation said.

An expected low of 26 degrees at night will approach the record set in 1873, when temperatures fell to 23 degrees, forecasters said.

Earlier in the day, the Illinois Tollway has dispatched its full fleet of 196 snowplows to assist in the morning commute and with daytime travel, spokesman Dan Rozek said.

Grid View A man rides a Divvy bike through the Loop as several inches of snow falls on the Chicago area, Thursday afternoon, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A cleans snow off the sidewalk in the Loop as several inches of snow falls on the Chicago area, Thursday afternoon, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A woman walks on West Randolph Street in the Loop as several inches of snow falls on the Chicago area, Thursday afternoon, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

People walk in the crosswalk at North Clark Street in the Loop as several inches of snow falls on the Chicago area, Thursday afternoon, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A man cleans snow off his car on North Clark Street in the Loop as several inches of snow falls on the Chicago area, Thursday afternoon, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A woman walks on North Clark Street in the Loop as several inches of snow falls on the Chicago area, Thursday afternoon, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A woman walks on North Clark Street in the Loop as several inches of snow falls on the Chicago area, Thursday afternoon, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A boy is dressed for the weather while walking down West Madison Street in the West Loop as several inches of snow fell on the Chicago area during the morning commute, Thursday morning, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A man rides a bike down West Washington Boulevard through West Loop as several inches of snow fell on the Chicago area during the morning commute, Thursday morning, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A skeleton decoration in the Halloween morning snow in the 1500 block of West Jackson Boulevard, Oct. 31, 2019. Brian Ernst/Sun-Times

A woman in a Halloween costume walks down West Madison Street in the West Loop as several inches of snow fell on the Chicago area during the morning commute, Thursday morning, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A pair of women try to stay warm and dry while walking down West Washington Boulevard in the West Loop as several inches of snow fell on the Chicago area during the morning commute, Thursday morning, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A CTA Blue Line train heads towards Forest Park during a snowy Halloween morning commute, Oct. 31, 2019. Brian Ernst/Sun-Times

A man walks his dogs down West Madison Street in the West Loop as several inches of snow fell on the Chicago area during the morning commute, Thursday morning, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A family walks down West Madison Street in the West Loop as several inches of snow fell on the Chicago area during the morning commute, Thursday morning, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A pedestrian walks past Halloween decorations in the 1500 block of West Jackson Boulevard as several inches of snow fell on the Chicago area during the morning commute, Thursday morning, Oct. 31, 2019 Brian Ernst/Sun-Times

A woman tries to stay warm while walking down West Madison Street in the West Loop as several inches of snow fell on the Chicago area during the morning commute, Thursday morning, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

A man rides a bike down West Washington Boulevard through West Loop as several inches of snow fell on the Chicago area during the morning commute, Thursday morning, Oct. 31, 2019. Ashlee Rezin Garcia/Sun-Times

Commuters wait at the Western Blue Line station during a snowy Halloween morning commute, Oct. 31, 2019. Brian Ernst/Sun-Times

On Wednesday, a messy mix of rain and snow traveled through Chicago, marking a record-breaking and unseasonably early first snowfall for Oct. 30.

By 1 p.m. Wednesday, the storm dumped 1.2 inches of snow over a 12-hour period at O’Hare International Airport and left 48,000 ComEd customers without power before turning into mainly rain.

The snowfall was the first of the season and came weeks earlier than the average, Kluber said.

While Oct. 30 is the average day for the first snowflakes of the year, Chicago doesn’t get its first measurable snowfall until Nov. 17 on average, Kluber said.

Wednesday’s storm also broke a snowfall record for Oct. 30 previously held in 1923, when Chicago got 0.7 inches of snow, according to weather service meteorologist Jake Petr. Chicago had that record beat by 7 a.m., when O’Hare was recording 0.9 inches.

The storm hit the western suburbs the hardest, dropping 3.4 inches of snow on Downers Grove by 7 a.m., Petr said. Other suburbs got between 2 and 3 inches.

Here's the forecasted timing of the expected worst conditions. Rockford area Thursday morning, Chicago late morning into afternoon. #ILWX pic.twitter.com/7YiQmzA07B — NWS Chicago (@NWSChicago) October 31, 2019

The storm not only hampered the commute, but left thousands of ComEd customers without power.

ComEd reported that a total of 48,000 customers lost power at some time Wednesday, but that power was quickly restored to 44,000 of them, company spokeswoman Cristina Messenburg said. About 5,000 customers were still without power by 3 p.m., she said.

There’s a risk that melting snow Thursday night and Friday morning could create hazardous driving conditions.

The weekend is expected to be dry, the weather service said, with temperatures staying mostly in the 30s.