* WHAT. Heat index values up to 110 expected. * WHERE. Portions of central and north central Maryland and central, northern and northwest Virginia. * WHEN. From 11 AM to 8 PM EDT Tuesday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur. * ADDITIONAL DETAILS. Very warm and humid conditions will persist into the overnight hours, adding heat stress to those without air conditioning. Ensure to stay hydrated and find ways to stay cool.

* WHAT. Dangerously hot conditions with heat index values up to 111 expected. * WHERE. Portions of central, northeast, northern and southern Maryland, The District of Columbia and central and northern Virginia. * WHEN. From 11 AM to 8 PM EDT Tuesday. * IMPACTS. Extreme heat and humidity will significantly increase the potential for heat related illnesses, particularly for those working or participating in outdoor activities. * ADDITIONAL DETAILS. Very warm and humid conditions will persist into the overnight hours, adding heat stress to those without air conditioning. Ensure to stay hydrated and find ways to stay cool.

* WHAT. Dangerously hot conditions with heat index values up to 109 expected. * WHERE. In Maryland, Washington County. In Virginia, Shenandoah, Frederick VA, Page, Warren and Clarke Counties. In West Virginia, Morgan, Berkeley and Jefferson Counties. * WHEN. From 11 AM to 8 PM EDT Tuesday. * IMPACTS. Extreme heat and humidity will significantly increase the potential for heat related illnesses, particularly for those working or participating in outdoor activities. * ADDITIONAL DETAILS. Very warm and humid conditions will persist into the overnight hours, adding heat stress to those without air conditioning. Ensure to stay hydrated and find ways to stay cool.

* WHAT. Heat index values up to 105 degrees Tuesday afternoon and near 100 degrees Wednesday afternoon. * WHERE. Adams, Cumberland, Dauphin, Franklin, Lancaster, Lebanon, Perry, and York Counties. * WHEN. For the Excessive Heat Warning, until 8 PM EDT Tuesday. For the Heat Advisory, from 8 PM Tuesday to 8 PM EDT Wednesday. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events.