Heat Advisory

* WHAT...For the Heat Advisory, heat index values of 100 to 104. For the Extreme Heat Watch, dangerously hot conditions with heat index values of 105 to 110 possible.

* WHERE...In Maryland, Central and Eastern Allegany County. In West Virginia, Eastern Grant, Eastern Mineral, Hampshire, and Hardy Counties.

* WHEN...For the Heat Advisory, until 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.