Chicago’s string of cloudless days is due to end Saturday as increasing south to southwest winds mix 80-degree temperatures with a modest increase in humidity. As the air becomes more unstable, cloudiness is forecast to increase in coverage. Showers and possible thunderstorms are expected to accompany a cold front across the region Saturday night. As showers and storms exit the area overnight, a brief period of cooling is forecast. Sunday’s highs are expected to lower by about 10 degrees from Saturday’s July-level warmth. The cooling trend is forecast to last less than 24 hours. By Sunday night, winds are due to back into the south, cutting off the flow of cooler air, and ensuring that September, 2013 is recorded as a warm, dry month. Like its predecessor, October is forecast to open with temperatures running well above normal.