National Weather Service United States Department of Commerce

Cooler temperatures will start off the week. A reinforcing shot of colder air will bring low temperatures into the 30s and possibly the upper 20s in northern areas before temperatures begin warming by midweek.
A light freeze is possible Monday night, mainly across parts of northeast Missouri and west-central Illinois. This is where chances of subfreezing lows are 30-50+%. Further south, chances dwindle quickly.