How far back must we go to find snow in Chicago during the third week of April?

Dear Tom,
I do not recall a spring like this during my 60 years living in Chicago. How far back must we go to find snow during the third week of April?
— Eric Field
Dear Eric,
Measurable snow in mid-April is not an every-year occurrence in Chicago, but it does occur with some regularity. Recent occurrences include 1.4 inches on April 14, 2014; 0.6 inches on April 18, 2011; 0.3 inches on April 16, 2001; 0.1 inches on April 18, 1989; 1.2 inches on April 16, 1983; and 3.1 inches on April 21, 1967, in the wake of the Oak Lawn tornado. The city’s heaviest late-season snow occurred on April 15-17, 1961, when 6.8 inches blasted the city. The city has also recorded measurable snow in early May with 2.2 inches falling on May 1-2, 1940, with areas northwest of the city logging as much as 5 inches. The city’s latest measurable snow was 0.2 inches on May 11, 1966.