* WHAT...Heat index values up to 108 expected. * WHERE...Atoka, Bryan, Coal, Hughes, Johnston, and Marshall Counties. * WHEN...Until 7 PM CDT this evening, and from noon to 7 PM CDT Monday. * IMPACTS...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. Take extra precautions when outside. Wear lightweight and loose fitting clothing. Try to limit strenuous activities to early morning or evening. Take action when you see symptoms of heat exhaustion and heat stroke.