The National Weather Service in Paducah has upgraded the existing heat advisory to an excessive heat warning for portions of western Kentucky, Missouri and Illinois.
In Kentucky the warning includes Christian, Trigg and Hopkins Counties as well as many other counties further west.
The warning is effective until Thursday at 8 p.m. High temperatures and humidity will combine to create heat index values between 110 and 115 degrees. Scattered thunderstorms Thursday afternoon may provide some relief from the heat.
For those who must be outdoors, stay hydrated and take frequent breaks in air-conditioning and never leave a child or a pet in a hot vehicle, as temperatures inside can quickly become fatal.