* WHAT. Heat index values up to 101. * WHERE. Central Pennsylvania. * WHEN. Until 8 PM EDT Saturday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Maximum heat index values 100-102 Friday afternoon. Maximum heat index values 100-104 Saturday afternoon. * WHERE. Central Pennsylvania. * WHEN. Until 8 PM EDT Saturday. * IMPACTS. Hot temperatures and high humidity may cause an increase in heat-related illnesses. * ADDITIONAL DETAILS. The risk of heat-related impacts is expected to reach its highest level over the weekend. The early arrival of the heat in the summer season, persistence of heat over multiple days, and very warm nights will be aggravating factors of overall heat stress.

* WHAT. Dangerously hot conditions with heat index values up to 110 possible. * WHERE. The District of Columbia, and portions of central, northeast, and southern Maryland, and central and northern Virginia. * WHEN. From Saturday afternoon through Saturday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events. * ADDITIONAL DETAILS. Oppressive heat and humidity will overspread the area Saturday and last into Sunday. Little relief from the heat is expected Saturday night with low temperatures in mid 70s to near 80 for most, which will compound heat stress on those without air conditioning.

* WHAT. For the Heat Advisory, heat index values up to 99. For the Excessive Heat Watch, dangerously hot conditions with heat index values up to 107 possible. * WHERE. Portions of northern Delaware, New Jersey, and southeast Pennsylvania. * WHEN. For the Heat Advisory, until 6 AM EDT Saturday. For the Excessive Heat Watch, from Saturday morning through Sunday evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events.

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

* WHAT. South winds 10 to 15 kt with gusts up to 20 kt expected. * WHERE. Chesapeake Bay and adjoining estuaries north of Smith Point VA, and Tidal Potomac from Cobb Island MD to Smith Point VA. * WHEN. From 4 PM this afternoon to 2 AM EDT Saturday. * IMPACTS. Conditions will be hazardous to small craft.

The Pennsylvania Department of Environmental Protection has issued a Code ORANGE Air Quality Alert on Friday for the Susquehanna Valley. A Code ORANGE Air Quality Alert means that air pollution concentrations within the region may become unhealthy for sensitive groups. Sensitive groups include children, people suffering from asthma, heart disease or other lung diseases, and the elderly. The effects of air pollution can be minimized by avoiding strenuous activity or exercise outdoors. For more information on ground-level ozone and fine particles, visit http://www.airnow.gov and http://www.aqpartners.state.pa.us.