Chicago has basked in many spring-like days this year, the majority of them during the amazing mid-February warm spell that registered a six day run with highs in the 60s and lower 70s. Since then, there has been a smattering of warm days, but also a wintry chill, accompanied by a major snow event. Temperatures will climb into the lower and middle 50s Monday morning, but the mild conditions will be accompanied by clusters of showers and thunderstorms, Chillier weather will return in the wake of the storms as afternoon temperatures fall back through the 40s as north winds increase. However, large high pressure building across the upper Midwest by midweek will propel another shot of chilly air into the area. Highs on Wednesday will struggle to 40 at a time of the year when they should be closer to 50. Warmer conditions with highs reaching the 60s will arrive Friday as a major storm system approaches from the Plains; but the price for the warm-up will be several rounds of potentially strong showers and thunderstorms.