Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. Do not leave young children and pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes.

* WHAT...For the Extreme Heat Warning, dangerously hot conditions with heat index values up to 107 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 109 possible. * WHERE...In Maryland, Washington County. In Virginia, Clarke, Frederick VA, Page, Shenandoah, and Warren Counties. In West Virginia, Berkeley and Jefferson Counties. * WHEN...For the Extreme Heat Warning, from 11 AM this morning to 9 PM EDT this evening. For the Extreme Heat Watch, from Tuesday morning through Tuesday evening. * IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events.