Lightning strikes in Alexandria Friday night. (Craig Hudson/THE WASHINGTON POST)

More than 1.5 million homes and businesses across Maryland and Virginia lost power Friday night as one of the most powerful and punishing storms in months swept across the Washington region.

Two fatalities were reported in the Springfield area of Fairfax County. A falling tree struck a car at Old Keene Mill Road and Bauer Drive, killing the male driver, said Officer Don Gotthardt, a Fairfax County police spokesman. The Associated Press, citing county police spokeswoman Mary Ann Jennings, reported that a 90-year-old woman, who was sleeping, was killed after a tree fell on her house.

In addition, a park police officer was injured by a falling tree and an 18-year-old man was struck by a power line, according to the AP. The man was in stable condition after receiving CPR.

The ferocity of the storm appeared to reflect the intensity of the daytime heat that set records across the region, as the mercury at Reagan National Airport rose to 104 degrees.

As the storm raced eastward, fueled by heat and humidity, wind gusts were estimated as high as 80 mph near Fredericksburg, 79 mph in the Reston area, 76 mph in the Seat Pleasant area of Prince George’s County and at 60 mph in other spots.

Lightning flashed, winds rose to tornadic levels, and rain and hail pelted one spot after another, striking many areas around 8:45 p.m.

As of 7 a.m. Saturday Pepco reported more than 426,000 homes and businesses were without electricity in its service area, which includes Montgomery and Prince George’s counties and the District of Columbia. The largest number of outages was reported in Montgomery.

Dominion Virginia Power gave a figure of 780,000, which included customers throughout Virginia. Fairfax County appeared hard-hit.

In the area served by Baltimore Gas and Electric, more than 400,000 homes and businesses lacked electricity as of 7 a.m. Saturday.

Meanwhile, the Washington Suburban Sanitary Commission issued mandatory water restrictions Saturday for all residential and commercial customers in Montgomery and Prince George’s counties because the storms had knocked out power to WSSC’s two water filtration plants and other facilities.

A WSSC statement urges customers to stop all outside water use such as watering lawns or washing cars, postpone using washing machines and dishwashers, and not to flush toilets after every use.

It remained uncertain when power would be restored, and it appeared that, on Saturday at least, many residents would face heat similar to Friday’s without the benefit of air conditioning.

Saturday will bring more oppressive heat and humidity to the area with a 20 percent chance of thunderstorms during the day and the high again aiming to reach at least 100.

A Pepco spokeswoman, Myra Oppel, said “it’s very safe to say multi-day outage.” She said early Saturday tyhat a more precise estimate would await a full assessment of the damage.

Witnesses expressed awe and astonishment at the unceasing flashes of lightning that punctuated the storm’s swift progress eastward across the region.

In Riverdale, the roof of an apartment house was reportedly ripped off.

Trees littered fields, streets and roads in many parts of the area, and some toppled onto houses.

The Chesapeake Bay Bridge, where traffic can be vulnerable to wind, was reported closed. Saturday morning, Amtrak suspended its service from Washington to Philadelphia at least until mid-morning, the Associated Press reported.

Residents of the Mount Vernon area of Fairfax County said the number of falling trees and broken branches littering their neighborhood suggested the sudden and powerful gusts of a powerful downdraft, possibly a microburst.

Metro service was severely affected. Trains were returned to their starting points. At least one tree was reported down on Orange Line tracks.

No power was available between Grosvenor and Shady Grove on the Red Line.

The transit agency said it was trying to fill gaps and come to the aid of stranded riders by creating a bus shuttle, but the heavy weather was delaying the buses.

Whipped by the wind, rain fell sideways in Georgetown. Trees fell onto cars on downtown streets and branches skittered across 12th Street NW.

An opera was halted in the middle of Act II at Wolf Trap. Witnesses said the skies seemed to suggest the onset of a hurricane.

The fury of the storm seemed to be at least in part a product of the record-setting heat of the afternoon. It was the hottest June day on record in the District.

Friday afternoon, on the National Airport tarmac, three men stood in the midst of a swelter that may have been as high as 130 degrees.

Dennis Frederick, Nathan Laryea and Tito Williams stood, arms folded, in sweat-soaked T-shirts and bright orange vests, as they contemplated what awaited them in the cargo hold of the AirTran flight.

They figured 145 degrees, at least? Maybe 120 bags each? About 30 or 40 pounds per bag? Everything off and the new load packed after about 30 minutes in the hold?

It was hot Friday. Everywhere, people chattered about it, notably complete strangers who tend to break the normal silence in elevators and grocery lines whenever the weather — hot, cold, snowy or rainy — gives them something in common to discuss.

Predictable things happened Friday: Swimming pools were busy, people ate more ice cream and those who could do so fled town early for the beaches. The laundry list of heat warnings was trundled out for amnesiacs and visitors who have never known Washington on the eve of July.

The people whose jobs allow them no escape — hot dog vendors, construction workers, bike messengers, meter maids, baggage handlers — sweated.

Some folks sought satisfaction or acclaim by exercising outdoors during the worst of it and sweated along with them. How hot was it?

Records were set across the region as the heat wave that had bedeviled the Midwest reached full blossom here.

The thermometer hit 104 degrees at National and hung there most of the afternoon. Dulles International Airport broke 100 degrees. All-time records also fell all over the South— 109 degrees in Nashville; 108 in Columbia, S.C.; 105 in Raleigh, N.C.; and 104 in Charlotte.

Just as it had been in the Midwest, the heat was blamed for several deaths, including three in Virginia.

“You need to drink a lot of water and stay in the shade,” said Williams, who acknowledged that shade is in short supply on an airport taxiway. At 35, he’s worked for eight years with Flight Service, the contractor that supplies baggage handlers for AirTran and several other airlines.

Frederick figured they each muscle about 1,000 bags a day.

“This humidity is unhealthy,” added Laryea, who is spending his first summer on the crew. “We’ve had a couple of hot ones, but this takes the cake.”

In McPherson Square, members of the Occupy D.C. movement returned to reclaim the ground where they camped out through the winter until departing two weeks ago.

But Friday’s fiery temperatures ruined some of their planned protests, and they headed instead for air-conditioned museums and cafes nearby.

Annie Gowen, Lena Sun, Mihir Zaveri and Susan Svrluga contributed to this report.