As the Baltimore area braced for another day of 100-degree heat, state health officials added an elderly Baltimore County man to the death toll from a heat wave and storm, bringing the total number of fatalities to 12.

County and state governments, meanwhile, stepped up aid to the 14,000 Baltimore-area households bearing the weather without power, many of them for a week. A blast of heat is expected Saturday, and more severe storms could arrive by Sunday, ahead of a cool-down expected Monday.

By 10 a.m. Saturday, the number of outages had declined to about 9,500.

The National Weather Service issued an excessive-heat warning for all of Central and Southern Maryland on Saturday from 11 a.m. to 10 p.m. High temperatures up to 104 degrees and heat index values of 110 degrees are expected.

Meeting by conference call in emergency session late Friday afternoon, the city Board of Estimates unanimously approved a seven-day extension of the state of emergency. MayorStephanie Rawlings-Blakedeclared the emergency June 30 to ensure a comprehensive storm response and to allow for potential federal reimbursement of storm-related costs, according to spokesman Ryan O'Doherty.

Robert Maloney, city director of emergency management, said that about 6,000Baltimore Gas and Electric Co.customers remain without power in Baltimore, and city outreach teams will be going door to door through the weekend checking on people, distributing ice, flashlights or other emergency supplies. BGE is supplying the city with information on which blocks still have customers without power.

Using that information, outreach teams on Thursday night found an apartment complex without electricity and sent two residents to the hospital for treatment, Maloney said.

"It's just so dangerous, especially with tomorrow getting to the temperature it is," he said. "So far, so good; the nighttime temperatures being cool have helped," and neighbors have been looking out for one another. "But until we get through Sunday and this heat breaks and everyone who has been without power since the storm has power, we can't relax."

The latest heat fatality announced Friday was a Baltimore County man older than 65. No other information was available.

High temperatures have reached 90 degrees or above for 10 straight days in the Baltimore area, including 99 degrees at Baltimore-Washington International Thurgood Marshall Airportand 103 degrees downtown at the Maryland Science Center on Friday. State health officials have confirmed nine heat-related deaths since Monday, four of them elderly Baltimore men, in addition to two Baltimore County men. Three people also died during the storm.

A statewide heat emergency plan is expected to be in effect through the weekend, spurring local governments to offer aid to residents. High temperatures are forecast to drop into the high 80s for a stretch starting Monday.

In Howard County, Columbia Association pools are open free of charge to county residents who are still without power. That county also extended hours Thursday through Saturday at its Alpha Ridge Landfill to allow residents to drop off storm debris from 7 a.m. to 6 p.m.

About 95 cooling centers are open at community and senior centers and public libraries across the state, according to the Maryland Emergency Management Agency, and state and local agencies are offering free transportation to the centers for those without air conditioning. Residents across the state can dial 211 to request a ride; in Baltimore, they can also call 311.

The Maryland Department of the Environment is predicting that air quality in the Baltimore area could reach Code Red unhealthful levels on Saturday, meaning ozone pollution is severe enough to pose health risks for all people. Even healthy individuals are urged to limit outdoor activities. Ozone levels reached Code Orange levels Friday in Anne Arundel County, bad enough to pose risks for children, the elderly, asthmatics and others with respiratory or heart conditions.

BGE officials said they are taking precautions to keep workers safe during repairs in the heat. One BGE employee was injured in single-car accident in Anne Arundel County early Wednesday morning, spokeswoman Rachael Lighty said. The employee was taken to University of Maryland Medical Center, treated and released the same day.

Field crews work shifts as long as 16 hours, and supervisors communicate with them frequently to ensure they have enough water and ice and are feeling up to work, Lighty said.

Baltimore Sun reporter Timothy B. Wheeler contributed to this article.