* WHAT. Dangerously hot conditions with heat index values over 105 possible. * WHERE. A portion of central Pennsylvania east of I-99 and south of I-80. * WHEN. From Sunday morning through Wednesday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. * ADDITIONAL DETAILS. Heat index values and the associated risk of heat-related impacts will be highest on Monday and Tuesday.

* WHAT. Dangerously hot conditions with heat index values over 105 possible. * WHERE. A portion of central Pennsylvania. * WHEN. From Sunday morning through Wednesday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. * ADDITIONAL DETAILS. Heat index values and the associated risk of heat-related impacts will be highest on Monday and Tuesday.

* WHAT. For the Heat Advisory, heat index values up to 103 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 107 possible. * WHERE. In Maryland, Washington County. In Virginia, Clarke, Frederick, Page, Shenandoah, and Warren Counties. In West Virginia, Berkeley and Jefferson Counties. * WHEN. For the Heat Advisory, from noon to 8 PM EDT Sunday. For the Extreme Heat Watch, from late Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Dangerously hot conditions with heat index values up to 110 possible. * WHERE. Washington DC, and portions of central and northern Maryland, and northern Virginia. * WHEN. From late Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events.

* WHAT. Heat index values up to 102 expected in the valleys. * WHERE. In Maryland, Central and Eastern Allegany County. In West Virginia, Eastern Grant, Eastern Mineral, Hampshire, Hardy, and Morgan Counties. * WHEN. From noon to 8 PM EDT Sunday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. For the Heat Advisory, heat index values up to 103 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 107 possible. * WHERE. In Maryland, Washington County. In Virginia, Clarke, Frederick, Page, Shenandoah, and Warren Counties. In West Virginia, Berkeley and Jefferson Counties. * WHEN. For the Heat Advisory, from noon to 8 PM EDT Sunday. For the Extreme Heat Watch, from late Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. For the Heat Advisory, heat index values up to 103 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 107 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 Heat Advisory, from noon to 8 PM EDT Sunday. For the Extreme Heat Watch, from Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. For the Heat Advisory, heat index values up to 103 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 107 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 Heat Advisory, from noon to 8 PM EDT Sunday. For the Extreme Heat Watch, from Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Dangerously hot conditions with heat index values up to 110 possible. * WHERE. Washington DC, and portions of central and northern Maryland and northern Virginia. * WHEN. From Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events.

* WHAT. Heat index values up to 102 expected in the valleys. * WHERE. In Maryland, Central and Eastern Allegany County. In West Virginia, Eastern Grant, Eastern Mineral, Hampshire, Hardy, and Morgan Counties. * WHEN. From noon to 8 PM EDT Sunday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Dangerously hot conditions with heat index values over 105 expected for the Lower Susquehanna Valley. * WHERE. Adams, Cumberland, Dauphin, Franklin, Lancaster, Lebanon, Perry, and York Counties. * WHEN. From 11 AM Sunday to 8 PM EDT Wednesday. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. * ADDITIONAL DETAILS. Heat index values and the associated risk of heat-related impacts will be highest on Monday and Tuesday.

* WHAT. For the Heat Advisory, heat index values up to 103 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 107 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 Heat Advisory, from noon today to 8 PM EDT this evening. For the Extreme Heat Watch, from Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. For the Heat Advisory, heat index values up to 105 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 110 possible. * WHERE. In Maryland, Northwest Montgomery and Frederick MD Counties. In Virginia, Eastern Loudoun and Western Loudoun Counties. * WHEN. For the Heat Advisory, from noon today to 8 PM EDT this evening. For the Extreme Heat Watch, from Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. For the Heat Advisory, heat index values up to 105 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 110 possible. * WHERE. In Maryland, Northwest Montgomery and Frederick MD Counties. In Virginia, Eastern Loudoun and Western Loudoun Counties. * WHEN. For the Heat Advisory, from noon today to 8 PM EDT this evening. For the Extreme Heat Watch, from Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Heat index values up to 102 expected in the valleys. * WHERE. In Maryland, Central and Eastern Allegany County. In West Virginia, Eastern Grant, Eastern Mineral, Hampshire, Hardy, and Morgan Counties. * WHEN. From noon today to 8 PM EDT this evening. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Dangerously hot conditions with heat index values up to 110 possible. * WHERE. Portions of DC, central, north central, northeast, northern, and southern Maryland, and northern Virginia. * WHEN. From Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events.

* WHAT. For the Heat Advisory, heat index values up to 103 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 107 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 Heat Advisory, from noon today to 8 PM EDT this evening. For the Extreme Heat Watch, from Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

A few west to southwesterly wind gusts to near 20 knots are possible through midday. Inexperienced mariners, especially those operating smaller vessels, should exercise extra caution if navigating the waters during this time.

* WHAT. For the Heat Advisory, heat index values up to 105 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 110 possible. * WHERE. In Maryland, Northwest Montgomery and Frederick Counties. In Virginia, Loudoun County. * WHEN. For the Heat Advisory, from noon today to 8 PM EDT this evening. For the Extreme Heat Watch, from Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. For the Heat Advisory, heat index values up to 104 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, Page, Shenandoah, and Warren Counties. In West Virginia, Berkeley and Jefferson Counties. * WHEN. For the Heat Advisory, from noon today to 8 PM EDT this evening. For the Extreme Heat Watch, from Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. For the Heat Advisory, heat index values up to 105 expected. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 110 possible. * WHERE. In Maryland, Northwest Montgomery and Frederick Counties. In Virginia, Loudoun County. * WHEN. For the Heat Advisory, from noon today to 8 PM EDT this evening. For the Extreme Heat Watch, from Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Heat index values up to 102 expected in the valleys. * WHERE. In Maryland, Central and Eastern Allegany County. In West Virginia, Eastern Grant, Eastern Mineral, Hampshire, Hardy, and Morgan Counties. * WHEN. From noon today to 8 PM EDT this evening. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Dangerously hot conditions with heat index values up to 110 possible. * WHERE. Washington DC, and portions of central and northern Maryland, and northern Virginia. * WHEN. From Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events.

* WHAT. For the Heat Advisory, heat index values up to 104 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, Page, Shenandoah, and Warren Counties. In West Virginia, Berkeley and Jefferson Counties. * WHEN. For the Heat Advisory, from noon today to 8 PM EDT this evening. For the Extreme Heat Watch, from Monday morning through Monday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Dangerously hot conditions with heat index values over 105 expected for the Lower Susquehanna Valley. * WHERE. Adams, Cumberland, Dauphin, Franklin, Lancaster, Lebanon, Perry, and York Counties. * WHEN. From 11 AM this morning to 8 PM EDT Wednesday. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. * ADDITIONAL DETAILS. Heat index values and the associated risk of heat-related impacts will be highest on Monday and Tuesday.