Heat Advisory

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

* WHERE...Portions of north central Maryland, northwest Virginia, and eastern West Virginia.

* WHEN...For the Extreme Heat Warning, until 8 PM EDT this evening. For the Heat Advisory, from 10 AM to 8 PM EDT Saturday.

* IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

* ADDITIONAL DETAILS...Early morning low temperatures in the 70s combined with oppressive humidity will result in little to no overnight relief. Prolonged excessive heat may impact power, water, and transportation systems. Heat index values of 95 to 100 are possible again Sunday afternoon.