Chicago weather: The first heat wave of 2026

CHICAGO - The first heat wave of the year begins today and will continue unabated through Wednesday.

Peak heat indexes will reach around 105° each of the next three days. A heat advisory is in effect for most of Chicagoland, but in Cook County, including the city of Chicago, there is an extreme heat warning. Both of these alerts are essentially for the same temperature and humidity combination.

Skies each of the next three days will be mostly sunny and humidity levels will be very uncomfortable. High temperatures will be in the mid to upper 90s all three days. There are two main things to stress from a safety perspective during this period: water and access to air-conditioning.

What we learned from the 1995 deadly heat wave is that even brief exposure to air-conditioning will help reduce people’s core body temperature enough to help them during intense heat waves — particularly in the city where it will remain much warmer at night.

What's next:

Beyond Wednesday, it will still be hot, but on each day, there will be opportunities for showers and thunderstorms to develop which would take the edge off the heat at least briefly. This will likely continue into the holiday weekend, so those with outdoor plans will need to keep close tabs on the forecast as our timing becomes refined.

Highs going into the weekend will more likely be around 90 or in the low 90s. In the event that thunderstorms do not happen (which is still a possibility, though less likely) highs would maintain the mid 90s.

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