Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.

* WHAT...For the Heat Advisory, heat index values up to 105 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 110 possible. * WHERE...In Maryland, Northwest Montgomery and Frederick Counties. In Virginia, Loudoun County. * WHEN...For the Heat Advisory, from noon today to 8 PM EDT this evening. For the Extreme Heat Watch, from Monday morning through Monday evening. * IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.