Area residents experienced slightly less sweltering temperatures and relatively quiet roads on Monday, as utility companies continued to battle massive power outages from Friday’s severe storms, and authorities raised the death toll from the storms and accompanying heat wave.

Officials in Virginia, Maryland and the District of Columbia reported Monday that at least 17 people died as a result of the storms. In addition, Virginia reported six heat-related deaths since June 20, but it was not clear how many of those — if any — resulted from losing electricity because of the violent weather.

Virginia Gov. Robert F. McDonnell (R) said in a statement Monday that of the 10 storm-related fatalities in his state, three occurred in Fairfax County. McDonnell said power outages in Virginia were at “historic levels ... typically seen only after hurricanes.”

Maryland Gov. Martin O’Malley (D) told a news conference Monday afternoon that six people died as a result of the storms and that three of the fatalities were “heat-related.” One storm-related death has been reported in the District.

O’Malley described the storms as “a hurricane-type punch without the hurricane warning” and acknowledged that not as many crews were out repairing utilities as people expected. “We suffered a hit that was the equivalent of a hurricane impact ... and yet we did not have the four days of warning that would have allowed us” to bring in crews from other states,” he said.

Maryland health officials reported the first three deaths related to the heat wave — one in Montgomery County, one in Wicomico County and one in Baltimore city. Officials declined to provide specifics except to say that the person who died in Montgomery County was a man between 18 and 65 and that the other two victims were men 65 or older. Health officials cautioned residents about the potential dangers from heat stroke and heat exhaustion that can develop from the hot, humid conditions typically associated with Maryland summers. In 2011, there were 34 confirmed heat-related deaths in Maryland, up from 32 in 2010.

In Montgomery County, officials canceled two July 4 fireworks events in Germantown and Wheaton in the aftermath of the storms. County Executive Isiah Leggett (D) said at a news conference Monday that police and fire personnel who would have been needed at those events would be better employed helping with recovery efforts.

“We need to take as many resources [as] we can” and direct them toward the recovery, he told reporters at the Springvale Terrace senior living facility in Silver Spring.

Gaithersburg also canceled its annual July 4 fireworks show because the Potomac Electric Power Co. (Pepco) has based its primary power-recovery operations on the fairgrounds, the city said in a statement Monday.

About 419,400 businesses and households in the District, Northern Virginia and Montgomery and Prince George’s counties in Maryland — 22.3 percent of customers — remained without electricity as of 2:30 p.m. Monday, according to data on the utilities’ Web sites.

That was down from 34 percent of households and businesses late Sunday afternoon, and hundreds of thousands more who had no power Friday night and Saturday.

But some areas experienced an increase in power outages Monday as utility companies sought to deal with the overall power crisis.

Among them was Fort Washington, Md., where Sarah Williams had thought she was one of the lucky ones. She and many of her neighbors had power all weekend. That luck seemed to run out just after noon Monday when her home and many others in her neighborhood lost electricity.

Williams, 52, said she called Pepco and was told that many homes are losing power for several reasons. One reason, she was told, was that Pepco was taking down some areas that had power in order work on blacked-out areas. She said she was also told that trees weakened by the storm have begun to fall, taking power lines down with them.

“I was so hopeful and excited that we escaped everything,” she said, adding that she even invited friends to store food in her freezer. “Now, I don’t know what’s going to happen.”

In the District, the Department of Public Works announced that it would collect spoiled food at six schools from residents who did not want to wait until their regular garbage pickups.

According to Pepco spokeswoman Courtney Nogas, “an enormous amount of work was done overnight” to restore electricity to affected customers.

The utility company said it had restored power to about half of the 440,000 customers who lost it in the storms, and on Wednesday will update its timeline for restoring power to 90 percent or more of its customers. On Sunday, officials said they would reach that milestone by Friday night, a schedule that Leggett, the Montgomery County executive, called “unacceptable.”

“We want to give people realistic expectations, but we are making progress,” Nogas said. “We do believe we will be able to move up that time.”

Among those who had power restored was Marty Williams, of Clarksburg, Md., who relied for two days on a small generator that kept essentials going. When the power came back on, Williams said, “We immediately turned on every light in the house, just because we could.”

The decline in outage numbers was little comfort to those residents bracing for another 90-degree-plus day without air conditioning or working appliances, or to those depending on hundreds of summer school and camp sites that were forced to close because they lacked electricity.

In hard-hit Montgomery County, the ratio of customers without electricity remained disproportionately high, at 38.6 percent.

The vast crescent of storms that swept across the Appalachians into the region on Friday night struck a swath of mid-Atlantic states reaching from New Jersey to Kentucky.

Among the Washington-area fatalities was a man who was struck by a car and killed in Arlington Sunday night as he walked through an intersection on Columbia Pike whose traffic lights were not working because of the storm.

Virginia state officials reported six heat-related deaths statewide, three more than they had logged as of Friday. No details were released, so it was not clear how many, if any, of the deaths were related to the storm and resulting power outages.

In Prince William County, a storm-related 911 outage delayed paramedics from getting to a person suffering from a cardiac issue over the weekend, said Jason D. Grant, a county spokesman. Grant said the party reporting the emergency got a busy signal when calling 911 initially, but eventually was able to get through on an emergency or non-emergency line.

Instead of the normal three- to five-minute response, it took emergency crews about 10 minutes to get to the patient, Grant said. The patient had a pulse upon reaching the hospital, Grant said. Additional details about the patient’s condition and the incident were not immediately available.

Grant said he was not aware of any other problems caused by outages of the 911 system.

“We put out very early that people would have to call non-emergency numbers to get emergency service,” Grant said. “That helped us address some of those issues.”

Downed trees and darkened traffic lights prompted fears of massive gridlock during Monday morning’s commute. But area highways were noticeably emptier than usual, thanks to residents who had departed on planned Fourth of July vacations, or who left town to escape sweltering homes and rapidly defrosting refrigerators.

The federal government and other employers also helped by offering those who had power at home the option of teleworking.

Out-of-service traffic signals remained the biggest problem for drivers, with 240 intersections without lights in Montgomery County, more than 120 such intersections in Northern Virginia and more than 60 dark signals in the District. Transportation officials in Northern Virginia reported 52 roads with blockages or closures due to downed power lines or trees, the majority of them in Fairfax.

The Virginia Department of Transportation is lifting the HOV restrictions on westbound I-66 inside the Beltway for the afternoon and evening. Restrictions will remain in place on I-395, I-95 and on I-66 outside the Beltway.

For the morning commute, HOV restrictions were eased on Interstate 270 in Montgomery County and on eastbound Interstate 66 inside the Beltway in Northern Virginia.

Maryland Area Regional Commuter (MARC) trains on the Brunswick Line experienced severe delays Monday morning because of signal issues and power outages, and Metro was accepting MARC tickets.

The District and Montgomery and Prince George’s counties were among the jurisdictions that canceled public school summer classes and programs for Monday, citing power outages. Montgomery County said its school buildings will be closed Tuesday as well.

Pepco cut the percentage of households and businesses without power in Montgomery County from 60 percent Sunday night to about 42 percent Monday morning, assisted by crews from Florida, Georgia, Maine and New Brunswick, Canada. The percentage ticked back up to 43.4 percent by late morning, a change that is not uncommon while large outages are being addressed.

Overall in the county, about 138,153 households and businesses — 39.2 percent — remained in the dark as of 11 a.m. Monday. (While Pepco serves the vast majority of Montgomery County customers, some homes and businesses get electricity from either Baltimore Gas and Electric or Potomac Edison.)

“For the most part, customers have been very understanding,” Pepco spokeswoman Nogas said. “We really appreciate our customers being so patient.”

Utility companies chipped away at the outages in other counties and the District as well.

In Prince George’s County, about 56,331 Pepco customers remained without power early Monday, a drop of about 30,000 from Sunday afternoon. But that number jumped back up to 66,333 by 11 a.m.

Prince George’s is also served by Baltimore Gas and Electric, which reported 25,672 customers out of power as of 11 a.m., or 32 percent, a slight increase from earlier in the morning but still far below the 45 percent of customers who were without electricity Sunday afternoon.

In Northern Virginia, Dominion Virginia Power reported that 170,853 households and businesses lacked electricity, about 20 percent of the total served. And in the District, Pepco reported 41,207 without power — 16 percent of its customer base, compared to 25 percent of D.C. residents without power as of Sunday at 4 p.m.

Novec, which serves parts of Fairfax and Prince William counties and other Northern Virginia jurisdictions, reported that 11.5 percent of its customers had no power in Loudoun County, but nearly all customers in Fairfax, Manassas Park and Prince William had electricity.

Dominion officials said most of its customers would have power by Tuesday, with some repairs taking until the weekend. BG&E officials also said it would take most of the week to get all the power up and running.

Pepco said it requested 1,000 additional crew members but initially found fewer than 200 available. Many of the utilities Pepco typically relies on for “mutual aid” in Ohio, Pennsylvania and New Jersey were also severely affected by the storm.

One caravan of repair trucks from Connecticut got stuck in a giant traffic jam Sunday on the New Jersey Turnpike and faced a substantial delay in arrival.

Flanked Sunday by Maryland Gov. Martin O’Malley (D), Leggett said at a news briefing Sunday in Gaithersburg that almost two days after the storm, more reinforcement crews should be in place.

“We have known since 40 hours ago that the storm hit and we didn’t have the availability of crews on the immediate area,” Leggett said. A week-long power outage in such scorching weather was “an unacceptable number.... That’s setting the bar too low.”

“I will not accept the timetable of July the sixth,” he said. “Today is just July the first. Having our citizens go seven days without utilities, in my opinion, is not the kind of service we should expect.”

O’Malley said the problem was that the storm produced effects akin to those of a hurricane, but it descended on the area without an early alert. “This sudden storm had a hurricane impact without a hurricane warning,” he said. “Nobody predicted this storm would be of the magnitude it was or the violence it was.”

Thomas H. Graham, Pepco’s region president, said the fault did not lie with Pepco, which has been sharply criticized in the past for its response to storm-related outages.

“You can’t say this was a Pepco issue. It’s a catastrophic weather event that millions of individuals are experiencing right now,” Graham said. “I can only think of one or two occasions when the damage has been greater.” He cited Hurricane Isabel in September 2003 and a January 1999 ice storm.

Facing an unknown stretch of time without power, many people used generators to produce electricity. Five people in the District were taken to hospitals Sunday with carbon-monoxide poisoning, and officials said generators should never be operated indoors.

The National Weather Service predicted slightly cooler readings — in the low 90s — for Monday, Tuesday and Wednesday, after days of record-breaking heat in which the mercury approached 100 degrees and the heat index easily exceeded that mark.

But meteorologists warned of extremely hot and threatening weather again by Thursday, with heat indexes of 105 and readings in the upper 90s through the weekend.

In Virginia, Rodney Blevins, Dominion Power’s vice president of electric distribution operations, said the storm caused the third-worst power failure in company history. It is the only event in its five largest mass outages not caused by a hurricane, he said. Blevins said Dominion has secured 1,000 additional line workers, coming from 13 states and Quebec. He estimated that 80 to 85 percent of Dominion customers still in the dark will have power restored by Tuesday night, with nearly all restoration done by Saturday. “A lot of hard work happens in that last 5 to 10 percent,” he said.

Across the area, people whose homes lacked power snapped up free bags of ice, moved to air-conditioned hotel rooms and drove around in air-conditioned cars to escape the heat.

“I’ve been living in the swimming pool,” said Bob Ambrosini, who had no power in his Great Falls home.

Fairfax officials said Sunday morning that 911 service, which was disrupted as a result of the storm, was only partially restored. People who could not reach 911 were urged to call 703 691-7561 or 703 691-3680.

The failure of 911 service in Northern Virginia on Saturday cut off many residents in Fairfax, Arlington and Prince William counties from emergency operators from about 6 a.m. until partial restoration started in early afternoon.

“I don’t ever remember the 911 system going down, and it happened exactly at the time when we needed it most,” said Sharon Bulova (D), chairman of the Fairfax County Board of Supervisors. “Why was there not a backup or something? That’s a question regional leaders will be focusing on with our state partners in the aftermath of the storm.”

Steve Souder, director of Fairfax County’s 911 Center, said that the county was prepared to respond to emergencies but that it depends upon the Verizon network to convey the calls. “The storm itself, we handled quite well. We rocked and rolled and handled a zillion calls,” he said. When the 911 service went down about 6 a.m. and non-emergency phone lines also failed, “it literally made us dead in the water.”

A Verizon spokesman said that a power failure in one of its Arlington facilities caused technical and mechanical damage that resulted in the 911 outage but that the company has been working around the clock to restore full service.

The Fairfax and Prince William 911 call centers are receiving most emergency calls, said Harry J. Mitchell, Verizon’s director of public relations. But Manassas and Manassas Park are still without 911. The facility that went down “provided routing for the 911 call centers. Some 911 calls were sent without addresses,” Mitchell said. “Full power is now back on, and we’re working to resolve whatever issues remain.”

The 911 failure was a unique event, he said. “We have extensive plans for backup power, and they work without a hitch most of the time. In the case of Arlington, this issue affected both our primary and backup systems.”

Although plenty of gas stations reopened Sunday, one in Annandale stood out: It was charging almost $4 for a gallon of regular unleaded, at least 50 cents more per gallon than the other stations.

“There’s a shortage of gas in the area,” said the manager of the Annandale Exxon station on Little River Turnpike, just inside the Beltway. He declined to give his name or comment further.

“It’s absolutely ridiculous,” said Mike Nolan of Annandale. It took him $95 to fill up his sport-utility vehicle.

Still, there was no shortage of customers along an otherwise electricity-free stretch of Annandale sometimes called Korea Town. Nearby stations on Little River Turnpike were dark.

“It’s a rip-off,” said Abdi Rashid of Annandale. “I don’t know why they’re doing that.”

He had two children in the car, ages 15 and 1 1 / 2. His home had no electricity. “We have to do it,” he said about paying the high price. “You have to go outside to get food for the kids. To go outside, you have to have gas.”

He said the same station was charging $3.49 on Friday.

Along a long stretch of Little River Turnpike in Fairfax and Annandale, and Columbia Pike in Annandale and Falls Church, most stoplights remained dark except at major intersections. Strip malls and fast-food restaurants that would normally be bustling on a Sunday afternoon were deserted.

But drivers were starting to get into the habit of stopping at intersections, allowing cars from side streets to enter without incident. Doug Henken of the Seven Corners area said he drove west to Centreville in search of a cool place to eat Saturday night.

All along Route 50, he said, “people were behaving themselves. I was shocked.”

Justin Jouvenal, Mark Berman, Emma Brown, Mike DeBonis, Maggie Fazelli Fard, Marc Fisher, Ashley Halsey III, Hamil R. Harris, Tom Jackman, Anita Kumar, Donna St. George, Patricia Sullivan, Lena Sun, Ted Trautman, Martin Weil, Ovetta Wiggins, Mihir Zaveri and Victor Zapana contributed to this report.