South to southeast winds may occasionally gust to around 20 knots through 2 AM on the Chesapeake Bay from Pooles Island to Smith Point and the tidal Potomac River downriver from Port Tobacco River. Inexperienced mariners, especially those in small craft, should exercise caution and be prepared for locally higher winds and waves.

* 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 central, northern, and northwest 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 upper 70s to near 80 for most.

* WHAT. For the Heat Advisory, heat index values ranging from 95 to 100 degrees. For the Excessive Heat Watch, dangerously hot conditions with heat index values ranging from 100 to 105 degrees possible. * WHERE. Portions of northern Delaware, central, northern, and southern 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 ranging from 105 to 110 degrees 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.

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.

* 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.