The first snow of the season is coming overnight Saturday and into the morning Sunday, according to the National Weather Service St. Louis office.
Meteorologist Lydia Jaja said the best chances for snow are in northeast Missouri and west-central Illinois north of I-70, with one to three inches forecasted.
South of I-70 in the St. Louis metro area, including Belleville, there will be mostly rain, she said.
The office has issued a winter weather advisory for portions of northeast Missouri and west-central Illinois from 9 p.m. Saturday night until 9 a.m. Sunday morning.
Snow will begin to move in by 9 p.m. Saturday and taper off by 9 a.m. Sunday, according to the forecast.
Temperatures will start in the mid-30s and drop to near freezing, creating a wet, heavy snow in the affected areas.
How much snow any given place gets will depend on the overnight temperatures.
Drivers may experience slick spots on roads with more snow.