Heat Wave Hits Chicago
After a couple of days of seasonal temperatures, a significant wave of dangerous heat and humidity moves into the Chicago area on Saturday and is poised to impact the region into next week.
The heat is felt early, with temperatures in the low 80s during the mid-morning hours across the area, with humidity already up to 79%.
Winds are expected to pick up throughout the day as the mercury rises into the late afternoon hours, with highs reaching the mid 90s.
The oppressive heat is forecasted to hover over the Chicago area through at least Monday evening, with some areas possibly seeing dangerous heat into Tuesday as well.
Heat and Humidity
There will be little relief in the evening hours this weekend, with low temperatures only falling to around or just below 80 degrees as humidity levels remain stable.
Gusty winds on Saturday are expected to add to the discomfort outdoors, with gusts as high as 45 miles per hour possible in areas around and north of Chicago, creating a “blast furnace” effect.
Throughout the next three days, peak heat indices throughout the region are expected to reach around 105 degrees, with minimal relief along the shores of Lake Michigan.
Southwest winds will gust as high as 35 to 45 mph near and north of I-80 today. The strong winds amid such hot air will not provide any reprieve from the heat and may actually make conditions feel even more oppressive. #ILwx #INwx
(🧵2/5) pic.twitter.com/7EAh5KD5Pf
— NWS Chicago (@NWSChicago) June 21, 2025
Extent of the Heat
The extent of the heat leaves little variance across the Chicago area, with daytime high heat indices expected to reach the triple digits on each of the next three days across all parts of the region.
From today through Monday, the majority of the daytime will be spent with heat indices in the upper 90s and 100s! Conditions will also remain plenty warm during the next few nights. #ILwx #INwx
(🧵3/5) pic.twitter.com/5Q9faSa7px
— NWS Chicago (@NWSChicago) June 21, 2025
Comparison to Desert Cities
While desert climate cities such as Phoenix, Arizona and Las Vegas, Nevada routinely see higher air temperatures than what Chicago will experience with this heat wave, those cities’ lack of humidity allows temperatures to significantly decrease at night, which will not happen in Chicago this weekend.
In addition to high humidity, residents within the city will also feel extra nighttime heat due to the urban heat island effect, in which concrete, asphalt and large buildings radiate heat absorbed during the day at night.
Impact on the Body
The abnormally warm overnight temperatures, which are close to daytime highs for this time of year, limit the body’s ability cool down and prepare for the next day’s heat without access to air conditioning.
Though the heat could stretch into Tuesday in parts of the region, chances for rain in the area return mid-week, coinciding with a drop in high temperatures.
Prepare for extreme heat over the next few days with afternoon heat indices over 100° expected through Monday. Conditions should begin to cool off toward midweek as rain chances make a return. #ILwx #INwx
(🧵5/5) pic.twitter.com/m2zBwU6rxU
— NWS Chicago (@NWSChicago) June 21, 2025
Thunderstorms
There are currently forecasted possibilities of thunderstorms several days next week, though more on the timing and severity of the storms will become clear as the date approaches.
Conclusion
The heat wave hitting Chicago is expected to bring extremely high temperatures and humidity, with little relief in sight until mid-week. Residents are advised to take precautions to stay cool and safe, especially during the hottest parts of the day.
Frequently Asked Questions
Q: How long will the heat wave last?
A: The heat wave is expected to last through at least Monday evening, with some areas possibly seeing dangerous heat into Tuesday as well.
Q: What are the peak heat indices expected to reach?
A: Peak heat indices are expected to reach around 105 degrees throughout the region, with minimal relief along the shores of Lake Michigan.
Q: Are there any chances of rain in the area?
A: Yes, chances for rain in the area return mid-week, coinciding with a drop in high temperatures.
Q: What is the urban heat island effect?
A: The urban heat island effect is a phenomenon in which concrete, asphalt, and large buildings radiate heat absorbed during the day at night, making the city feel hotter than surrounding areas.
Q: How can I stay safe during the heat wave?
A: To stay safe during the heat wave, stay hydrated, stay indoors during the hottest parts of the day, and take breaks in cool, well-ventilated areas. Avoid strenuous activities and wear light, loose-fitting clothing.
