National Weather Service United States Department of Commerce

Expect increasing heat and humidity the next 3 days, with the hottest day being Thursday. Chances of storms returns Thursday afternoon and evening, with a few severe storms possible.
A heat advisory is in effect from 1 to 9 pm Wednesday for areas west of I-55. Heat indices will peak from 100 to 106 degrees Wednesday afternoon over western IL. Drink plenty of water, and avoid prolonged outdoor activities especially from late morning through the afternoon hours. Never leave children or pets unattended in parked vehicles.
A line of severe storms could develop later Thursday afternoon across central Illinois, then progress southward through early Thursday evening. Primary hazards look to be damaging winds and hail up to 1". Potential of any tornadoes appears to be low. Plan ahead for the potential of severe storms, and know where you would take shelter if severe storms should approach your location.