Temperatures throughout much of Monday hovered in the upper 50s and low 60s. Low, leaden clouds and brisk NW winds compounded the effect of the chilly temps which were more typical of mid October. Chicago and its environs sat directly beneath a “cold core” upper-level low which circulated rain-cooled air around its center. The sluggish system is forecast to eject eastward on Tuesday allowing skies to clear after two straight days with little or no sunshine. In response, temps are expected to run closer to the seasonal normal for mid-September. Warming is to begin in earnest after midweek when a pattern shift will allow sustained SW winds to overspread the area, thus beginning a series of 80-degree days. Warmth is expected to peak over the weekend and extend into early next week. Current forecasts suggest average daily temps during the period will run 10-15 degrees above normal with highs reaching well into the 80s.