Chicago, Illinois – The unusually comfortable stretch of late July weather across northern Illinois is coming to an end as heat and humidity rapidly build this weekend, bringing heat index values approaching 105 degrees and the potential for strong thunderstorms by Sunday and Monday.
According to the National Weather Service in Chicago, Friday will remain pleasant with highs ranging from 76 to 81 degrees. A few locations could see a brief morning sprinkle before skies gradually improve. Overnight lows will fall into the upper 50s to mid-60s, providing one more comfortable night across the region.
Saturday marks the beginning of a warming trend with highs between 78 and 83 degrees. A few early morning showers are possible, mainly south of Interstate 80, before increasing humidity makes conditions noticeably muggier by evening.
By Sunday, temperatures climb into the upper 80s to lower 90s, while peak heat index values rise into the upper 90s to around 105 degrees. A 20% to 30% chance of thunderstorms develops later in the day, and some storms could become severe. The hot, humid pattern continues Monday with highs of 88 to 93 degrees and another chance of evening thunderstorms across Chicago, Rockford, Joliet, Aurora, Elgin and surrounding communities.
Residents should stay hydrated, avoid prolonged outdoor activity during the hottest part of the afternoon and monitor forecasts if outdoor events are planned. Those attending festivals, sporting events or traveling should be prepared for rapidly changing weather if thunderstorms develop.
The National Weather Service says confidence is increasing that heat and humidity will dominate Sunday and Monday, with additional watches, Heat Advisories or severe weather alerts possible as the weekend progresses.
Five-Day Forecast for Chicago, Illinois
- Friday: A morning sprinkle possible, then partly sunny. High 76–81°F, low 58–66°F.
- Saturday: A few early morning showers possible south of I-80, then warmer and more humid. High 78–83°F, low 69–74°F.
- Sunday: Very humid with a 20–30% chance of thunderstorms. Peak heat index upper 90s to around 105°F. High 87–92°F, low 71–79°F.
- Monday: Very humid with a chance of evening thunderstorms. High 88–93°F, low 68–75°F.
