May 22 | Climate Review and Weather Update

We had milder weather as we turned the corner in May. Average temperatures this week ranged from the low 60s in northern Illinois to the low 70s in southern Illinois, between 2 and 4 degrees above normal. Despite a bit more warmth this week, low humidity allowed nighttime temperatures to regularly drop into the 40s, including lows of 38 degrees in Decatur and 39 in Barrington. May temperatures to date have been 1 to 3 degrees below average statewide.

by Trent Ford, State Climatologist
ISWS PRI University of Illinois

Precipitation continued to be elusive in northern and far southern Illinois this week, while the Interstate 70 corridor continued to get rain they really didn’t need. 7-day totals ranged from less than a quarter of an inch in northeast Illinois to nearly 6 inches in south-central Illinois. Heavy rain from training thunderstorms caused isolated flash flooding in parts of Fayette and Marion Counties last week. May has been somewhat to very dry in much of the state, following a very wet April. Most of the northern half of the state and far southern parts of the state have had less than 50% of average May precipitation to date, and parts of northeast Illinois have had less than 25% of normal May precipitation. In fact, Rockford is on pace to have its driest May on record, following its second wettest April on record.

Looking ahead, I have good news for folks who are tired of cooler weather. Temperatures will quickly climb into the mid to upper 80s next week, providing a seamless transition to meteorological summer. On-again off-again showers and storms pepper the 7-day forecast, with expected totals ranging from 1.5 inches in far southern Illinois to less than a half an inch in northern Illinois. Farther out, the final summer weather outlooks from the Climate Prediction Center dropped this week, showing decidedly nothing for Illinois. That is, equal chance of warmer, cooler, wetter, and drier than normal summer weather. So, you can take that to the bank.