The National Weather Service has issued a heat advisory for parts of northern Illinois and northwest Indiana, warning that heat index values could approach 105 degrees Fahrenheit. The advisory covers ten counties and is in effect from noon to 9 p.m. on September 1 and September 2, 2026.
In Illinois, the counties named are LaSalle, Kendall, Grundy, Kankakee, Will and the southern portion of Cook County. In Indiana, the advisory includes Lake, Porter, Newton and Jasper counties. Residents in these areas are advised to take precautions during the specified hours.
The advisory comes as a late‑summer heat wave moves through the Chicago region, producing unusually high feels‑like temperatures for early September. The National Weather Service highlighted that the heat index, which combines temperature and humidity, is expected to reach the 105‑degree mark during the afternoon and early evening periods.
The advisory period runs from 12:00 PM to 9:00 PM each day, encompassing the time when outdoor activity is most common. The service recommends that people stay hydrated, limit strenuous activity, and seek air‑conditioned environments when possible.
Authorities have previously used similar advisories to alert the public when heat conditions pose health risks. While no specific health alerts have been issued for this event, the warning serves to inform residents of the potential for heat‑related illness if precautions are ignored.
The heat advisory will be reviewed after the two‑day period, and any extensions or additional warnings will be communicated by the National Weather Service.
Heat index values near 105 degrees are considered extreme for the region at this time of year, and they can increase the risk of dehydration and heat exhaustion if people remain outdoors for extended periods.