A heat wave that has sent temperatures climbing close to 100 degrees in some parts of the region will continue today and through tomorrow, but an approaching cold front should bring some relief by the end of the week, forecasters say.
"It looks like [the heat wave] will probably last through Wednesday," said Brian Lasorsa, a National Weather Service meteorologist, "but it should cool off Thursday."
Weather forecasts call for a slight chance of thunderstorms today but a better chance tomorrow, Mr. Lasorsa said. The parched area has seen only 1.52 inches of precipitation since June 1, significantly less than the 3.92-inch average for that period.
Highs in the District yesterday reached 97 degrees, with highs today and tomorrow expected to be about 95 degrees.
Although the high temperatures are uncomfortable, they are far from record-breaking. The record high for today was 105 degrees, set in 1936.
It is, however, hotter than average. Mr. Lasorsa said the normal temperature for today is 88 degrees.
The Metropolitan Washington Council of Governments issued a "Code Orange" air-quality alert through tomorrow, meaning that air quality can be unhealthy for children, the elderly and those with respiratory problems and other health conditions.
Moderate "Code Yellow" air quality is expected Thursday.
The District opened four cooling centers at noon yesterday to provide residents with relief.
The city's heat-response plan, which includes the opening of cooling shelters and other services, goes into effect when the heat index reaches 95, said Jo'Ellen Countee, a spokeswoman for the Department of Homeland Security and Emergency Management.
The Department of Human Services kept homeless shelters open beyond their usual 7-p.m.-to-7-a.m. hours so homeless people could stay inside during the day, Mrs. Countee said.
The Department of Motor Vehicles (DMV) yesterday observed shortened "Code Red extreme heat service hours" at its inspection station in Southwest and will continue with those hours through tomorrow, officials said.
The station opened an hour early and closed five hours early because of the high temperatures and poor air quality.
The DMV Brentwood Service Center closed early yesterday because of an air-conditioning outage, officials said. The facility was working to fix the air conditioning and planned to reopen for normal hours today.
Other DMV locations are maintaining regular hours.
But for workers whose jobs forced them to be outside, there was no choice but to put up with the heat.
"Sometimes the heat bothers," said Hugo Gonzales, 32. "This is very hot. I drink a lot."
Mr. Gonzales was part of a 25-man construction crew working the second shift, the hottest shift, from 2 p.m. to midnight at the Frederick Douglass Memorial Bridge.
"It is not as hard on them as it would be on office workers," said Bobby Burton, 45, a superintendent for Corman Construction Co. "It's like winter. They're used to being out in the cold, so it doesn't bother."
A light breeze also helped ease the heat.
"This is OK," said Mr. Burton, who has been in construction 22 years. "Even when the temperature is 99 degrees."
D.C. firefighters felt the heat as well.
"When it's hot out, we respond to more heat-related issues," spokesman Alan Etter said. "There have not been an overwhelming number of calls. But we know that the temperature is very hot, and we're certainly prepared."
He said the department makes an effort to keep firefighters safe and healthy in the heat.
The department often dispatches "rehab resources" when responding to major fires, Mr. Etter said. They cycle firefighters in and out quickly and often have a "canteen unit" that supplies water, sports drinks and food to working firefighters, he said.
"If we don't keep our own people safe and healthy, the fire doesn't go out," he said.