The National Weather Service in Paducah said the entire region is now under an Excessive Heat Warning until 9 Thursday night.
Forecasters said dangerously hot conditions with daily heat index values up to 114 are expected.
Extreme heat and humidity will significantly increase the potential for heat related illnesses, particularly for those working or participating in outdoor activities.
Low temperatures will generally be in the mid to upper 70s, which will not provide much relief from the heat even at night. Daily chances of isolated thunderstorms will provide relief to very few.
To beat the heat, officials said to drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. Young children and pets should never be left unattended in vehicles under any circumstances.
Take extra precautions should be taken by those woring or spending time outside. When possible, reschedule strenuous activities to early morning or evening. Know the signs and symptoms of heat exhaustion and heat stroke. Wear lightweight and loose fitting clothing when possible.
To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air conditioned environments.
Anyone overcome by heat should be moved to a cool and shaded location.