* WHAT...For the Extreme Heat Warning, dangerously hot conditions with heat index values up to 113. For the Heat Advisory, heat index values up to 110 expected. * WHERE...Lincoln, Payne, Atoka, Bryan, Coal, and Hughes Counties. * WHEN...For the Extreme Heat Warning, until 9 PM CDT this evening. For the Heat Advisory, from noon to 9 PM CDT Thursday. * IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses. Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.