Through May 12, April is averaging warmer than May by nearly three degrees. Has there even been a full month of May that ended up with a lower mean temperature than the preceding April?
— Chuck Sabr, Chicago
It’s rare, but it has happened once. Citing Chicago weather records dating back to 1871, Chicago climatologist Frank Wachowski reports that in 1915, April averaged 56.3 degrees and May just 54.2 degrees. April 1915 was characterized by an incredibly warm back half. The warmth set in on April 18 with a high of 79, and 10 of the month’s last 12 days reached at least 70 degrees, including seven days in the 80s. The warmest day was April 26 with a high of 88 and a low of 69. In contrast, May was quite chilly, logging just four days of 70 degrees or higher, including the month’s lone 80, an 86-degree high on May 12.