Purnell Crockett, 65, stays warm by camping out over a steaming street grate at the corner of 18th and C Streets NW on Friday. (Jahi Chikwendiu/Washington Post)

On Sunday, temperatures in the Washington area are expected to climb to the low 40s, with a good chance of rain by nightfall.

Enjoy that. Relish it, even. Then make sure the outdoor faucets are shut off, get the cat or dog inside and bundle up.

By Monday, the weather will turn wicked. It’ll be as cold as seven degrees, with the wind making it seem like it’s 15 below zero, according to the National Weather Service.

As part of a record chill sweeping through the nation, the Washington region is bracing for its coldest week this winter.

“Basically we’re looking at the some of the coldest temperatures since 1994 in the region,” said Washington Post Capital Weather Gang meteorologist Jason Samenow. “It’s going to be borderline dangerous for people to be outside unless they are prepared and covered up.”

A new record for low temperatures could occur Tuesday, when the mercury drops toward the 5 degrees recorded on Jan. 7, 1884, the National Weather Service said.

In preparation Saturday, schools in the area were checking on classroom heating systems, police said they would keep special watch for hypothermia victims and the District made plans to make its recreation centers in parks available during the day to anyone in need of some warmth.

That it could get that cold seemed unfathomable to Miqueias Martins, 30, who was visiting Washington on Saturday from Brazil and was bundled up in 28-degree weather.

“This is new — this is very different for me,” he said of his first trip to the United States. “It’s very, very cold.”

Police and other local officials say they are primarily concerned with the homeless and elderly, who are the most vulnerable during extreme weather conditions.

On Saturday, D.C. police tweeted warnings to the department’s 33,000 Twitter followers, asking them to check on neighbors and to keep handy the district’s hypothermia hotline: 202-399-7093.

Pamela L. Michell, director of New Hope Housing, said her organization expects a surge of people inside its two shelters in Fairfax County, where scores of homeless people camp out in the woods.

“We have a no-turn-away policy, no matter how many zillion people we get,” Michell said.

Fire officials and utility companies said they’re worried about problems stemming from people cranking up the heat during the cold spell. They advised residents to insulate their homes now and to shut off water pipes that can freeze and burst.

Mark Brady, public information officer for the Prince George’s County Fire Department, said about 80 percent of fire fatalities involve the use of space heaters.

“Space heaters are a major concern for firefighters,” Brady said, noting that such fires typically occur when bedsheets dangling near space heaters combust while homeowners are asleep. It’s best to unplug the units before going to bed, Brady said.

Brady also said homeowners should ensure that chimneys and furnaces are cleaned and properly operating to keep poisonous carbon monoxide gas from collecting indoors.

Dan Genest, spokesman for Dominion Virginia Power, said the utility company is asking customers to keep their thermostats down as a way to prevent widespread power outages.

“If you’re comfortable with your thermostat at 68 degrees and using a blanket, you should do that,” he said. “Turn your thermostat down and save money.”

Nate Robinson, 60, planned to spread kitty litter in front of his home in Northeast Washington to provide grip against the ice forming on his sidewalk.

He wished he’d thought of that sooner, he said, after slipping while trying to heave a bag of trash into a bin Saturday.

“Next thing I knew, I was on my” derriere, Robinson said.