Afternoon storms brought heavy rains and flashing lightening into the Washington metropolitan area, after the National Weather Service issued a severe thunderstorm watch, effective until 10 p.m.

The storms provided some relief from a second day of stifling heat and humidity, with the temperature reaching 98 degrees, with a heat index of 105, earlier today. By 7 p.m., the temperature had dropped to 76 degrees, the weather service reported.

The weather service said a cold front would push through the region early this evening, ending the heat wave but bringing the prospect of severe thunderstorms with damaging winds.

In its latest bulletins, the weather service said the severe thunderstorm watch was in effect for Washington, D.C., 13 counties in Maryland, including the Washington suburbs, and 23 counties in Virginia, including Northern Virginia.

Scattered showers and thunderstorms started in the lat afternoon, slowing down commuters who were confronted with a brilliant lightening display, sheets of rain and downed tree branches on the outer loop of the Beltway in Montgomery County.

Lightening is blamed for igniting a fire at a home in Germantown, according to wire services. No injuries have been reported. A fire department spokesman said the house on the 12900 block of Churchill Ridge Circle was hit during the storm that moved into Montgomery County at around 6 p.m.

Earlier in the day, local authorities were struggling to respond to problems caused by the excessive heat.

District officials say there was an air conditioning problem on the second floor of the Department of Motor Vehicles office at 65 K Street, NE, wire services reported. That is where the department handles phone calls, permit reinstatements, driving records and insurance matters.

The DMV said it was moving everyone down to the first floor, where it was cooler. But they warned that services would be limited.

The car inspection station in Southwest closed at 1 p.m. today, also because of the heat.

A surge of demand for power left about 2,200 customers in Montgomery County without electricity to power their air conditioners this morning. About 500 District customers lost power because of a small substation fire at 10th and L streets, NW.

That was an improvement over last night.

More than 17,000 homes served by three utility companies were without power at times last night. They included 5,000 in Montgomery County, 3,800 in Anne Arundel County, 2,000 in Northern Virginia and 6,900 in the District.

Yesterday, Pepco broke its all-time peak demand at 5 p.m. as customers used 6,452 megawatts of power. The previous peak was 6,364 megawatts set on July 29, 2002, according to PEPCO.

PEPCO urged area residents to take steps to cut down on the costs of cooling their homes by dialing up the thermostat to 78 degrees -- "a temperature still within a reasonable comfort range," it said.

"For every degree increase, customers can save 3 percent to 5 percent," the company said in a statement. "Use of a fan in an occupied room will also make the air feel cooler than it actually is."

Officials at Baltimore Gas and Electric told wire services they, too, are bracing for what could be the third consecutive day of record-breaking demand for electricity in central Maryland.

Demand for power at the utility peaked yesterday afternoon at a single-day record of more than 7,000 megawatts, easily beating the new record that was set on Monday. Electric usage for a typical summer day is 5,500 megawatts.

The company said the hot weather and the high demand has caused some service interruptions. So far, the utility has not had to resort to voltage reductions but could consider them later.

Dominion Virginia Power reached its highest demand on record Monday for its service area in Virginia and North Carolina. Figures for yesterday will not be available until today, but the company said it might have broken that record.

Meanwhile, a cold front promised relief today for the middle of the country, the Associated Press reported. By late this morning, rain and thunderstorms marking the front stretched from Texas to northern New York state.

The front touched off storms yesterday that battered parts of northern Ohio with hurricane-force wind. At least 30,000 FirstEnergy Corp. customers were without power last night.

Cooler air behind the front promised highs only in the 70s today in northern Ohio and elsewhere in the upper Midwest.

Ahead of the front, however, New York's Central Park cooled only to 80 degrees during the night and headed for a high today in the upper 90s. Meteorologists warned of a third straight day of dangerously hot and humid weather in parts of the Southeast.

Florence, S.C., hit a record high of 101 on yesterday, toppling the old record of 99 that had been on the books since 1949, the weather Service said. Raleigh-Durham, N.C., also peaked at a record 101, and Lumberton, N.C., roasted at 102.

The heat wave this month has been blamed for at least 28 deaths in the Phoenix area, most of them homeless people, along with at least four in Missouri, two young children left in hot cars in Oklahoma, and one each in Kentucky, Ohio and Mississippi.

The heat also was blamed for at least 1,200 cattle deaths in Nebraska.

Farmers across the Midwest have been using everything from electric fans to cold showers to protect their livestock from the oppressive heat.

Staff writer Nick Anderson contributed to this report.