The high of 48 was the tenth time since 2000 that the high in May was 48 degrees or colder.
Last may actually saw a colder high, with 46 degrees on May 16, 2014. Snow was actually observed in parts of Northern Illinois that day.
This was only the seventh day since the official observation site moved away from very near to Lake Michigan - in 1942 - that a high temperature remained below 50 degrees this late into spring. Click on the photo for a list of those seven dates from May 20th or later!