What do Chicago weather records show for the earliest and latest occurrences of 90-degrees days?

Dear Tom,
What do Chicago weather records show for the earliest and latest occurrences of 90-degrees days?
— Lloyd Fry, Chicago
Dear Lloyd,
In a typical year, Chicago officially records 17 days of at least 90 degrees, spanning about a three-month period from early June to early September. That has varied tremendously over the 147 years of the city’s climate records. Chicago weather historian Frank Wachowski tells us that the earliest onset of 90s was in 1930, with back-to-back 90-degree highs April 10-11 and the latest a 94-degree high Oct. 6, 1963.
The year that produced the most 90s was 1988, with 47 occurrences during that torrid drought summer. Only one year, 1875, failed to produce a 90-degree day, and three years — 1882, 1884 and 1915 — logged just one; but in that era, the city’s official thermometer was located downtown near Lake Michigan.