<P> Spring in Chicago is perhaps the city's wettest season: Winter conditions can persist well into April and even occasionally into May . Thunderstorms are especially prevalent in the spring time as the city's lakeside location makes it a center of conflicts between large volumes of warm and cold air, which can trigger a wide variety of severe weather . </P> <P> On the other hand, large snowfalls can also occur in late March and in early April . For example, in 1970, over 10 in (25 cm) of snow fell in a storm that occurred on April 1--2 . Twelve years later, Opening Day for the Chicago White Sox was postponed due to another 9 - inch (23 cm) snowfall that had occurred on April 5 . Even more extraordinary, over 18 in (46 cm) of snow fell on March 25--26, 1930, which remains one of the city's five biggest recorded snowstorms despite it occurring past the vernal equinox . The average date for last measurable snowfall (≥ 0.1 in or 0.25 cm) is April 1 . </P> <P> Temperatures can vary tremendously in the springtime; at 100 ° F (38 ° C), March is the month with the greatest span between the record high and low . At O'Hare, temperatures as low as 7 ° F (− 14 ° C) and 31 ° F (− 1 ° C) have been recorded as late as April 7 and May 21, respectively . Conversely, in official records, the earliest triple - digit (100 ° F (38 ° C)) high occurred on June 1, 1934, when official readings were taken closer to Lake Michigan . Though rare, triple - digit heat has occurred in May at Midway Airport and in outlying suburban locations . Typically, the last freezing low of the season on average occurs on April 13 at Midway and ten days later at O'Hare . </P> <P> During the springtime, the effects of Lake Michigan are most prevalent . During this season, the lake is still quite cold, as the effects of much warmer temperatures are slow to affect the large body of water of Lake Michigan . It is common for Lake Michigan shoreline and water temperatures to remain in the 40s even into May . If the winds blow from the east, or from Lake Michigan into the city, a wide discrepancy in temperatures in a matter of miles can be found, especially on particularly warm days . It is not uncommon for high temperatures to be officially recorded in the 80s and occasionally 90s at O'Hare, Midway, and in suburban locations but to have temperatures be only in the 40s or 50s along the immediate lakeshore . </P>

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