(AP) -- Forecasters say the heat index could climb into the triple digits as hot and steamy weather blankets parts of Illinois.

The National Weather Service says it will feel like 100 to 105 degrees in parts of southwestern Illinois by this (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 says that could trigger flash floods, large hail and strong winds that reach 60 to 80 miles per hour.

Dozens of cooling centers are opening across the region.

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