All of the Ozarks is under at least a Heat Advisory through Thursday evening, with areas north and west of Springfield now under an Excessive Heat Warning.
The National Weather Service says the warning is for dangerous heat index values up to 110.
Forecasters say extreme heat and humidity will significantly increase the potential for heat related illnesses, particularly for those working for participating in outdoor activities.
Drink plenty of fluids and stay in an air-conditioned room.
Take extra precautions by rescheduling strenuous outdoor activities to the early morning or evening, and know the signs and symptoms of heat exhaustion and heat stroke.