Forecasters say the heat index could climb into the triple digits as hot and steamy weather blankets parts of Illinois.
Heavy rainfall and thunderstorms are likely in the early afternoon with high humidity and temperatures in the high 80s and light winds.
The National Weather Service in St. Louis says it will feel like 100 to 105 degrees in parts of southwestern Illinois by Tuesday afternoon. Temperatures in southwestern, northwestern and central Illinois will be in the 90s, but the humidity will make it feel even hotter.
Meanwhile, the blistering temperatures are expected to give way to strong storms, as the moist air mass over the state becomes unstable as the day progresses.
The weather agency's office in the Quad Cities says that could trigger flash floods, large hail and strong winds that reach 60 to 80 miles per hour.