Earliest first 90-degree high for Chicago

Dear Tom,
What is the earliest date that Chicago has ever reached 90 degrees?
—Wayne Griffin
Dear Wayne,
Chicago’s earliest hot weather occurred nearly 80 years ago, with highs of 90 degrees
on April 10-11, 1930. Just two days earlier, with high pressure over the area, the
mercury dipped to 34 degrees. As the high moved east, strengthening southwest winds
delivered a flood of warm air. The mercury jumped to 70 on April 9, then soared to the
two record early-season 90s. Since 1871, the city has reached the 90-degree hot
weather benchmark only four times in April. The other two occurrences were a high of
90 degrees on April 30, 1942, and a 91 on April 22, 1980. The 1980 high of 91 was
notable because just a week earlier, the city was hit with nearly 4 inches of snow on
April 14-15, a testament to the huge temperature fluctuations Chicago can experience
in the spring.