The Billy Goat Trail, off the C&O Canal is a rocky challenging trail between the C&O and the Potomac with views of the river. (Susan Biddle/The Washington Post)

A woman hiking the Billy Goat Trail in Montgomery County died Saturday in what authorities believe was a heat-related medical emergency during the hottest weekend of the year in the Washington region.

Temperatures soared to 99 degrees in the District and to 100 degrees at Dulles and in Baltimore, but some spots felt as hot as 115 degrees with humidity. Local governments urged residents to stay indoors or to find air-conditioned cooling centers, while extending hours at some swimming pools and other facilities. Weather forecasts showed some relief was expected early in the week.

Powerful thunderstorms tore through the area Sunday night, toppling trees onto streets and houses, and knocking out power to thousands.

The death of the hiker, who has not been publicly identified, is the first potential heat-related fatality reported over the scorching weekend by Washington-region officials.

Montgomery County Fire and Rescue Services and U.S. Park Police officials responded to emergency calls from the Billy Goat Trail slightly before 2 p.m. Saturday on the most strenuous section of the hike. They said the woman, who appeared to be in her 30s, was unconscious and being aided by other hikers.

The woman was taken by helicopter to Suburban Hospital in Bethesda, where she later died.

Andrea Prestipino, 34, decided to play tennis at Banneker Recreation Center despite scorching temperatures in Washington, D.C. on Sunday July 21, 2019. (Fenit Nirappil/Fenit Nirappil/The Washington Post)

Authorities evaluated about a dozen other hikers in this section who showed sign of heat exhaustion, Pete Piringer, spokesman for Montgomery County Fire and Rescue Services, said. He said two of them were also taken to medical facilities.

Montgomery County officials said they’ve rescued overheated hikers from the Great Falls area almost daily over the past several weeks, most commonly from Section A. Park officials had posted signs warning visitors to avoid hiking in the hottest hours of the day.

If the woman’s death is confirmed to be heat-related, it would bring Maryland’s toll of deaths relating to the recent extreme temperatures to five. One of those people was a man in Prince George’s County who died earlier in July.

In the District, the D.C. fire department received 24 heat-related calls Saturday, the most of any day in July.

Some of the places where city residents could normally get a break from the heat closed their doors because they could not keep up with the temperatures or they had other issues.

The Georgetown Library closed because building temperatures were too high, and Wilson Aquatic Center closed for several hours because of sewage issues. Takoma, Turkey Thicket and Barry Farm pools were also closed over the weekend because of heating issues. The Harriet Tubman Women’s Shelter had air-conditioning problems, and women seeking a safe place to sleep were instead directed to the Sherwood Recreation Center.

But some relief is now in sight.

Monday was shaping to be partly sunny and slightly less hot with evening storms likely, according to the Capital Weather Gang. The punishing heat is forecast to break Tuesday, with mostly cloudy skies and highs in the mid-80s.

That was welcome news for Washingtonians looking for an escape.

On Sunday morning, Hannah Roberts-Forest stood in front of her Petworth condominium building with her 1½ -year-old daughter, Kiera, waddling barefoot on the shaded pavement.

Kiera would normally be hanging out at the local playgrounds, which were mostly deserted.

“I love summer, and I’ll still take this over the winter,” said Roberts-Forest, 32, “but it hasn’t been fun staying inside multiple days with a toddler who always wants to run around outside.”

On the same block, a stream of senior citizens left their homes for the first time in the weekend to attend Sunday church services.

“I thought about skipping this morning, but I need the word,” said Phyllis Gordon, 70, wearing a wide-brimmed hat.

“I need the word, too,” added her friend, Patricia Williams, 75, “but there will be no extracurricular activities.”

Several miles away, Andrea Prestipino stood drenched in sweat outside Banneker Recreation Center, holding a tennis racket and panting as he waited for his Uber ride home to Shaw. He regretted keeping up his usual exercise routine: soccer on Saturday, tennis on Sunday.

“I’m trying to beat the heat, but not really managing,” said Prestipino, who is 34 but said he felt like he was 68. “I’m just going into A/C and staying there.”

Rob Scott, 63, was on a bench in McPherson Park on Sunday morning under the shade of tree and soaking in the wind. His doctor told him he needs to walk around more, but he can’t with the heat.To stay hydrated, he said he drank 20 bottles of water the day before.

“I’m excited for [the heat] to finally leave,” said Scott, holding a bottle of Arizona Iced Tea, “but we gotta let nature take its course.”

Martin Weil contributed to this report.