It was the city’s coldest Easter in four decades as the mercury struggled to afternoon highs only in the lower and middle 30s. Conditions were even worse Downstate, where several inches of snow covered the ground as the mercury hovered close to freezing. Sunshine should return for a while early Monday, allowing temperatures to climb back into the 40s, but the price for the warm-up will be rain and possible thunderstorms as a new storm system passes through central Illinois. The same storm will produce heavy snow across the upper Midwest Tuesday and the Chicago area could even see some snow before the precipitation exits Tuesday night as colder air sweeps into the area in the storm’s wake. The cold will take up residence for the remainder of the week, with the mercury finally returning to the 40s by next weekend. With the cold upper air pattern in place, real spring warmth is not in the cards here as least through mid-April.