* WHAT...For the Heat Advisory, heat index values of 100 to 104 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values of 105 to 110 possible.
* WHERE...In Maryland, Washington County. In Virginia, Clarke, Frederick, Page, Shenandoah, and Warren Counties. In West Virginia, Berkeley, Jefferson, and Morgan Counties.
* WHEN...For the Heat Advisory, from 11 AM to 8 PM EDT Wednesday. For the Extreme Heat Watch, from Thursday morning through Friday evening.
* IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.
* ADDITIONAL DETAILS...Dangerous heat may linger into Saturday. Prolonged extreme heat could impact power, water, and transportation systems.