Robert Clark had no choice but to work in the stifling heat yesterday.
He had to repave the sidewalk near the Library of Congress.
“It’s mandatory that we be out here today. It’s our job,” said Mr. Clark, 38. “This weather feels terrible, but you gotta do what you gotta do.”
Mr. Clark was one of many workers who were required to stay outside as temperatures soared to 99 degrees. Combined with humidity, the temperature felt like 101 degrees.
Tourists and those who work in office buildings took refuge inside air-conditioned buildings, under trees, or on shady steps or benches.
Those who work in construction and law enforcement had no such shelter.
“We sweat like crazy and it’s hard to breathe, not because of heavy pollution or anything but because of the humidity,” said Stephen Karlinchak, an officer with U.S. Capitol Police.
One of the few officers who volunteer to patrol outside year-round, Officer Karlinchak is used to all kinds of weather, but yesterday was one of the hottest days he said he could remember.
Today won’t be much better.
The National Weather Service forecast temperatures in the mid-90s with a heat index from 102 to 107 degrees. The index uses temperature and humidity levels to gauge how hot it feels outside.
“In the sun it feels awful,” said Tina McBride, 42, a landscaper who was working beside Mr. Clark.
Working outdoors often leads to heatstroke, heat exhaustion and other heat-related illnesses.
“I passed out last week,” Mr. Clark said. “People pass out a lot.”
Last week, a stonemason collapsed on scaffolding near the Mall. Since then, the masons have been brought inside until the heat advisory ends, Mrs. McBride said.
U.S. Capitol Police officers wear bulletproof armor, and their stiff, white uniforms become sweat-laden and bulky in summer, making the vests even more uncomfortable.
“I can’t believe technology hasn’t invented something cooler,” Officer Karlinchak said. “Now I know how our troops in the Middle East feel. They have to wear this stuff in much more strenuous activity and worse temperatures.”
Capitol Police have required the armor since a fatal shooting of two officers on the force in 1998.
Coping with the extreme temperatures tends to be easier for those from naturally warm regions.
“It’s really OK,” said Jimmy Oko, a security officer. “I’m from Africa, and it’s much hotter than this.”
Outdoor workers are taking measures to stay cool and hydrated.
Some work earlier shifts or take breaks during the hottest part of the day, between 11 a.m. and 3 p.m.
“Sunblock helps a lot, and also light-colored clothes,” Mr. Clark said while taking a quick break.
Construction supervisors at the Woodrow Wilson Bridge said they were holding frequent “toolbox talks” during which they encouraged workers to drink plenty of fluids throughout the day.
“I drink like 2 gallons of water a day at a minimum,” said Jesse Childers, 21, a construction worker from Missouri toiling at an apartment complex in Northeast. “You only use the bathroom once a day because you sweat so much.”
The searing heat also has taken a toll on vehicles.
Ena Sorzano, a dispatcher with ANT Towing in Northeast, said the company towed about 20 vehicles that had overheated yesterday.
“Now that the heat’s started, things pick up more,” she said. “Cars start breaking down.”
PJM Interconnection, the electricity grid operator for 51 million people in 13 states and the District, reported that customers set a record peak demand for electricity yesterday.
At 4 p.m., peak demand in the PJM region was about 135,000 megawatts of electricity, exceeding the grid operator’s previous record of 130,574 megawatts reached July 18.
PJM reported that demand was met without problems and that generation supplies were adequate. One megawatt is enough electricity to power about 800 homes.
Cardozo High School shut its doors early yesterday because of the heat.
Gary Emerling contributed to this report.