It looks like Mother Nature's Halloween curveball will affect more than just Chicago-area trick-or-treaters.
As of 3:45 p.m., O'Hare International Airport canceled more than 700 flights because of windy, rainy and snowy conditions. Delays and cancellations are expected to increase throughout the day. Midway International Airport reported normal operations as of Friday afternoon.
Snow was spotted in Chicago's north and west suburbs during the morning commute, from Waukegan to Elgin. By 8 a.m. the snow had moved into the city, and it could get worse as the day goes on.
The National Weather Service issued a Wind Advisory for the area, from 10 a.m. to 6 p.m. Friday.
The NWS reports winds near Lake Michigan could reach 45 mph with gusts of up to 65 mph. In the suburbs, winds could gust to 45 mph.
NBC 5 weather models show lake-effect rain showers mixing with snow at times, and a few thunderstorms will be possible along the South Shore.
In northwest Indiana, a Winter Weather Advisory was issued for Jasper, Lake, Newton and Porter counties from 10 a.m. to 10 p.m. ahead of reports of up to 3 inches of snow.
Winds of between 25 mph and 35 mph with gusts of up to 50 mph are expected by early Friday afternoon, according to the NWS, and even stronger winds are likely near Lake Michigan.
There also is a threat for heavy bursts of lake-effect snow showers Friday afternoon and evening, resulting in isolated accumulations of one to two inches.
Some heavy snowfall could limit visibility under a mile and make travel hazardous across the area, the NWS reports.
Forecast models show a cold front arriving in the Chicago area after midnight, particularly between 2 a.m. and 3 a.m., bringing winds from the north.
Temperatures early Friday aren't expected to climb much higher than the low 40s. Factor in the wind, and it'll be considerably colder.
The system that puts a damper on Halloween Friday will be out of the area by Saturday. While the weekend begins on a cold note but will improve a bit. Sunday will begin with some sunshine before clouds increase later in the day with temperatures in the 50s.