NBC Chicago meteorologist Andy Avalos is tracking another potential 100-degree day along with storms later on.
High temperatures didn't quite break into the triple digits Wednesday in the midst of a heat advisory for the Chicago area.
Peak temperatures reached 98 degrees Wednesday, with a heat index of 104. The temperatures were expected to reach 100-104 degrees with a heat index between 105 and 108.
The 11 a.m. advisory for northern Illinois and northwest Indiana began after scattered morning showers cleared the area and skies turned mostly sunny. The advisory lasts until 10 p.m.
A heat advisory means hot and humid weather could cause illness. The record high for July 25 is 101 degrees set in 1940 at O'Hare Airport.
Meteorologists are predicting a 50 percent chance of thunderstorms Wednesday night and Thursday, and temperatures are expected to dip into the low to mid-80s the remainder of the week.
The weather service advises people to avoid working outside during the hottest parts of the day Wednesday to wear loose, lightweight clothing, and drink plenty of water.