CHICAGO (CBS) The clouds and occasional bursts of rain and thunder will give way to sunshine – and yet another day of extreme heat – Wednesday afternoon.

CBS 2 Meteorologist Ed Curran says during the 6 a.m. hour Wednesday, it was a mere 72 degrees. But later in the day, hot air will shoot up from the southwest as the clouds dissipate.

In the afternoon, the high will climb to 99 degrees, and Curran says the temperature could hit 100 or 101 south of the city and 105 in Peoria.

A heat advisory is in effect for the entire the Chicago area and most of Illinois, Indiana and southern Wisconsin. The advisory begins at 11 a.m. and continues through 10 p.m.

The National Weather Service warns that the heat index could hit 105 degrees north of Interstate 80 and 105 to 110 south of the expressway.

The conditions carry a risk for heat-related illness. Everyone is advised to drink plenty of fluids, stay out of the sun and in an air-conditioned indoor space, and check op on relatives or neighbors.

The normal high for the day is 84 – a figure that might seem like 64 given the conditions we’ve seen lately. The record for July 24 is 101 degrees, set in 1940.

On Wednesday night, the temperature drops to 77, followed by a high for Thursday of 88. The high for Friday is 85, Saturday 83, Sunday 84, Monday 86, and Tuesday 87.