The thunderstorms are forecast to roll through between 4 p.m. and 10 p.m.
Some of the storms could bring damaging winds and large hail. The National Weather Service said the severe risk exists across the Chicago area, but the most likely spots for the worst storms are south of I-88 in areas including Aurora, Naperville, Bolingbrook, Orland Park, Oak Lawn, Hammond and the south side of Chicago.
There is also the chance of light showers overnight Sunday into Monday.
Monday's highs are expected to be in the 70 to 77 degree range. Temperatures on Tuesday will fall dramatically, with highs from 56 to 61 degrees.