* WHAT. Heat index values up to 109 expected. * WHERE. Portions of central and northern Maryland, and central and northern Virginia. * WHEN. From noon to 8 PM EDT Wednesday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

* WHAT. Heat index values up to 109 expected. * WHERE. Portions of central, northern and southern Maryland, The District of Columbia and northern Virginia. * WHEN. From noon to 8 PM EDT Wednesday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

* WHAT. Heat index values up to 104 expected. * WHERE. In Maryland, Washington County. In Virginia, Rockingham, Shenandoah, Frederick, Page, Warren and Clarke Counties. In West Virginia, Morgan, Berkeley and Jefferson Counties. * WHEN. From noon to 8 PM EDT Wednesday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

* WHAT. Heat index values up to 109 expected. * WHERE. Portions of central, northern and southern Maryland, The District of Columbia, and central and northern Virginia. * WHEN. From noon to 8 PM EDT Wednesday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

* WHAT. Heat index values up to 104 expected. * WHERE. Portions of north central and western Maryland, northwest and western Virginia and eastern West Virginia. * WHEN. From noon to 8 PM EDT Wednesday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

* WHAT. For the first Small Craft Advisory, south winds 10 to 15 kt with gusts up to 20 kt. For the second Small Craft Advisory, south winds 10 to 20 kt with gusts up to 30 kt expected. * WHERE. Chesapeake Bay from Pooles Island MD to Drum Point MD, Tidal Potomac from Cobb Island MD to Smith Point VA, Chester River to Queenstown MD, Eastern Bay, Choptank River to Cambridge MD and the Little Choptank River, and Patuxent River to Broomes Island MD. * WHEN. For the first Small Craft Advisory, until 2 AM EDT Wednesday. For the second Small Craft Advisory, from 10 AM to 6 PM EDT Wednesday. * IMPACTS. Conditions will be hazardous to small craft.

* WHAT. South winds 10 to 20 kt with gusts up to 25 kt expected. * WHERE. Tidal Potomac River from Key Bridge to Cobb Island MD, Chesapeake Bay north of Pooles Island MD, and Patapsco River including Baltimore Harbor. * WHEN. From 10 AM to 6 PM EDT Wednesday. * IMPACTS. Conditions will be hazardous to small craft.

* WHAT. For the Small Craft Advisory, south winds 10 to 20 kt with gusts up to 30 kt expected. * WHERE. Chesapeake Bay from Pooles Island MD to Drum Point MD, Tidal Potomac from Cobb Island MD to Smith Point VA, Chester River to Queenstown MD, Eastern Bay, Choptank River to Cambridge MD and the Little Choptank River, and Patuxent River to Broomes Island MD. * WHEN. Until 6 PM EDT this evening. * IMPACTS. Conditions will be hazardous to small craft.

* WHAT. South winds 10 to 20 kt with gusts up to 25 kt expected. * WHERE. Tidal Potomac River from Key Bridge to Cobb Island MD, Chesapeake Bay north of Pooles Island MD, and Patapsco River including Baltimore Harbor. * WHEN. From 10 AM to 6 PM EDT Today. * IMPACTS. Conditions will be hazardous to small craft.

* WHAT. Heat index values up to 104 expected. * WHERE. Portions of north central and western Maryland, northwest and western Virginia and eastern West Virginia. * WHEN. From noon to 8 PM EDT Wednesday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

* WHAT. Heat index values up to 109 expected. * WHERE. Portions of central, northern and southern Maryland, The District of Columbia, and central and northern Virginia. * WHEN. From noon to 8 PM EDT Wednesday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

* WHAT. Oppressive heat with afternoon heat index values between 100 and 105. * WHERE. A portion of South-Central PA and the Lower Susquehanna Valley * WHEN. Until 8 PM EDT Wednesday. * IMPACTS. High temperatures and humidity may cause heat illnesses. * ADDITIONAL DETAILS. In addition to the daytime heat, overnight low temperatures will also be very warm and oppressively muggy.