* WHAT. Heat index values as high as 104. * WHERE. A portion of central Pennsylvania. * WHEN. Until 8 PM EDT Sunday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Heat index values at or above 100. * WHERE. South-central Pennsylvania. * WHEN. Until 8 PM EDT Sunday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses. * ADDITIONAL DETAILS. Sunday should be the last of this string of the hot and muggy days. Hot and muggy weather returns for many places in Central PA on Tuesday and Wednesday.

* WHAT. South winds 10 to 15 kt with gusts up to 25 kt. * WHERE. Chesapeake Bay from Smith Point VA to Pooles Island MD and adjoining estuaries, and Tidal Potomac from Cobb Island MD to Smith Point VA. * WHEN. Until 6 PM EDT Sunday. * IMPACTS. Conditions will be hazardous to small craft.

* WHAT. Southwest winds 10 to 15 kt with gusts up to 20 kt expected. * WHERE. Tidal Potomac River from Key Bridge to Cobb Island MD. * WHEN. From 11 AM to 6 PM EDT Sunday. * IMPACTS. Conditions will be hazardous to small craft.

* WHAT. Heat index values up to 108 expected. * WHERE. Portions of central, north central, northeast, northern and southern Maryland, The District of Columbia and central, northern and northwest Virginia. * WHEN. From 11 AM to 7 PM EDT Sunday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur. * ADDITIONAL DETAILS. Oppressive heat and humidity will overspread the area through Sunday before a cold front tracks through early Monday. Little relief from the heat is expected tonight with low temperatures in the 70s, with lower 80s near Washington, D.C. and Baltimore. This will compound heat stress on those without air conditioning.

The Maryland Department of the Environment has issued a Code ORANGE Air Quality Alert Saturday for the Baltimore City Metro and Annapolis region. 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 the web site mde.maryland.gov/programs/air/AirQualityMonitoring/Pages/index.aspx.

The Maryland Department of the Environment has issued a Code ORANGE Air Quality Alert Saturday for Northern Baltimore. 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 the web site mde.maryland.gov/programs/air/AirQualityMonitoring/Pages/index.aspx.