Chicago typically sees its first trace of snow on Oct. 31, and this year will be no different, the NBC 5 Storm Team said.
"We're right on target," NBC 5 Meteorologist Pete Sack said, with snowflakes already falling in some parts.
Aside from light snow sticking on grassy areas, the Halloween snow isn't expected to be much in the form of accumulation, Sack said. However, some parts in Northwest Indiana may see heavy slush, while others in Illinois will see quick "bursts" of snow or squalls coating roadways, creating potentially hazardous travel conditions at times.
As the first flakes move into northern Illinois, here's a timeline of what to expect and when.
Tuesday morning
Tuesday morning starts out cold, with a freeze warning in effect until 9 a.m. for Kankakee, parts of Cook and Will counties in Illinois and Lake, Porter, Newton and Jasper counties in Indiana.
Local
"Sub-freezing temperatures in the mid 20s expected," an alert from the National Weather Service said. "Frost and freezing conditions will kill crops, other sensitive vegetation and possible damage unprotected outdoor plumbing."
As of 5:15 a.m., temperatures at O'Hare International Airport clocked in at 31 degrees, with wind chill values only in the upper teens.
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According to the NWS, a "burst" of gusty snow moving in from the west is expected to hit parts of Northern Illinois in Tuesday morning through through 10 a.m. Although the snow could lead to slick spots on the road, it's only expected to result in a "coating," the NWS said, as temperatures are expected to warm above freezing through the mid-to-late morning.
In addition, "waves of snow showers and squalls" are expected to hit the Chicago area Tuesday morning and afternoon."
According to the NWS, a snow squall is described as a quick-moving wintertime weather hazard that can result in dangerous driving conditions.
"Snow squalls are intense, but limited duration, periods of moderate to heavy snowfall, accompanied by gusty surface winds resulting in reduced visibilities and whiteout conditions," the NWS said.
"Squalls can occur where there is no large-scale winter storm in progress and might only produce minor accumulations," the NWS added.
Tuesday afternoon
According to Sack, one of the waves is expected to hit around 4 p.m. -- just in time for trick-or-treating -- when widely scattered snow showers are likely to mix with rain.
"We'll be wavering right around that freezing mark so we have the opportunity of seeing rain mixed in" Sack said, creating the potential for slushy conditions.
Although temperatures are expected to rise into the upper 30s as the day goes on, wind chill values are expected to remain only in 20s, Sack said.
"Maybe have that long underwear ready to go underneath those costumes if you're going trick-or-treating," NBC 5 Meteolrogist Pete Sack said.
Northeast Illinois will see the chance for a "final burst" of snow between 5 p.m. and 10 p.m., the NWS said, with the possibility of slushy snow falling at a rate of one inch per hour, the NWS said.
In Northwest Indiana, lake effect snow will likely see moderate to heavy snow in the evening and overnight, with one to two inches possible, the NWS said. Closer to the lake, the snow will be mixed with rain.
When will it warm up?
Although the trick-or-treat forecast looks mostly dreary, some relief is in sight, the NBC 5 Storm Team said, as temperatures are expected to reach back into the upper 50s by the end of the week.
