Extreme Heat Warning issued for much of Wisconsin

The National Weather Service has issued an Extreme Heat Warning for Fond du Lac County beginning at noon Monday, June 29, 2026, and continuing through 7:00 p.m. Tuesday evening. Afternoon temperatures are expected to climb into the lower 90s through Thursday, but the high humidity will make it feel much hotter, with heat index values reaching between 100 and 108 degrees.

Forecasters say this level of heat can become dangerous in a short amount of time, especially for older adults, young children, people with chronic health conditions, and anyone working or exercising outdoors.

Residents are encouraged to drink plenty of water, spend time in air-conditioned buildings whenever possible, wear lightweight, loose-fitting clothing, and avoid strenuous outdoor activities during the hottest part of the day. It’s also important to check on neighbors and relatives who may be more vulnerable to the heat and to never leave children or pets inside parked vehicles.

The heat doesn’t disappear when the sun goes down, either. Overnight lows will only fall into the mid-70s, offering little relief and increasing the risk of heat-related illness for those without air conditioning.

Looking ahead, the hottest conditions are expected through Thursday. While temperatures should ease slightly beginning Friday, highs will remain close to 90 degrees with continued humidity and periodic chances for thunderstorms into the weekend.

Stay with KFIZ for the latest forecast updates as this dangerous stretch of summer weather continues.