Oh, the misery: Cold followed by snow, then a solid dose of rain and finally the lowest temperatures in two decades are about to toss across Washington the same frigid blanket that has smothered most of the nation.

Unlike with many a weather crisis, this one’s on you. It’s your car battery that could die, your pipes that could burst, your know-nothing kids who could head out without a hat or gloves.

You won’t be able to point the finger at Pepco or tardy snowplows in this joust with Mother Nature.

Temperatures fell to 7 degrees in Washington early Tuesday morning.

The forecast freeze prompted some area school officials, including those in Fairfax, Loudoun and Prince William counties and Manassas to decide late Monday to close Tuesday.

Robert Ross, who has been homeless for nine years and hangs around McPherson Square in Northwest Washington, said he will ask the city’s shelter workers for a few more blankets to swathe around his new forest-green sleeping bag.

“I will sleep outside. There’s too many bugs and too many crazy people in the shelters,” said Ross, 57, as he pointed to a shopping cart filled with his possessions and tugged at a stain on the collar of his tan trench coat. “Hopefully, my sleeping bag here will keep me warm. I’ll think of a warm woman.”

Tuesday’s high temperature may struggle to reach 15, and if it’s below 8 degrees at daybreak, that will match a low temperature not seen here since 1996.

“This is going to be a shock to the system. It will be almost as cold at noon as it is at 8 in the morning,” said Jason Samenow of The Washington Post’s Capital Weather Gang.

“It’s really unexpected cold,” said Jesse Strauss, 22, an American University student from New York City. “You don’t buy an apartment expecting it’ll be below zero in D.C., because it’s never below zero in D.C.”

Nationally, the weather map that was ablaze with the yellows and oranges of summer five months ago turned more somber shades of blue, purple and gray as Arctic weather swept higher temperatures to the southern tips of California and Florida. The swath of extreme weather was driven by a shift in a circular pattern known as the polar vortex, which rotates around the North Pole.

The severe weather closed schools in states such as Minnesota and North Dakota and cities such as Chicago, Milwaukee and Des Moines, where the norm is so frigid in January that the sheer cold usually gets no more than a shrug. But wind chills of 50 to 60 degrees below zero get noticed even in those frozen tundras.

In western Minnesota, frigid weather caused diesel fuel in several school buses to congeal. “They can’t run — that’s the bottom line,” said Bryan Thygeson, superintendent of the Dilworth-Glyndon-Felton school district. “You have to get the buses inside and warm them up.”

Schools in Prince George’s and Arlington counties and Alexandria planned to open two hours late. D.C. officials said that school would begin on time but that school buildings would open earlier than normal to accommodate early-arriving students. Montgomery County public schools expected to open on schedule.

“The severe cold is just another way of Mother Nature reminding us we’re not in charge,” said Jeff Platenberg, Fairfax County schools’ assistant superintendent for facilities.

In the District, school heating systems were being checked in advance of students’ return Tuesday after a two-week winter break.

“We are closely monitoring the situation,” schools spokeswoman Melissa Salmanowitz said.

The District’s homeless were being directed to beds in shelters for the night. The city has regular and cold weather overflow shelter for 1,346 men and 426 women. The city already had put about 240 families in hotel rooms, said Michele Williams, of the organization that runs the District’s homeless shelters. “There is certainly a risk for people to be severely injured or to die in these cold temperatures,” Williams said.

Avni Jain, a family medicine physician at Adventist Medical Group, is familiar with extreme cold, having lived in Minnesota for more than a decade.

The notion that you lose 80 percent of your body heat through your head isn’t true, Jain said, noting that the head makes up only 10 percent of your body.

When temperatures reach freezing, it’s best to spend as little time outside as possible, she said. If you have to be outside, dress in layers, which can be easily removed if you feel yourself overheating. Consider goggles if the wind is fierce because cold winds can freeze your corneas, Jain said.

Leana Wen, director of patient-centered care research at George Washington University Hospital said your mother was right – you should wear your hat and gloves and ear muffs. It’s the hands, fingers, toes and ears that are at most risk during extreme cold.

Hypothermia and frostbite are the main dangers during extremely cold weather. If you are out and begin to feel lightheaded or have trouble thinking clearly, it’s probably best to move indoors.

As for the expression “bone-chilling” cold, Wen said she’s not sure where that originated, but theorized that sometimes we feel cold so deep down we may feel like it’s penetrated every bit of our body.

The very people who normally rush to the rescue when the weather turns threatening — who have plows “at the ready” and power-line repair crews “poised to roll” — were wringing their hands.

“The greatest impact to motorists will be slick or even icy conditions on what appears to be just wet pavement — so staying alert and slowing down will be critical for your safety and others,” said Melinda B. Peters, administrator of the Maryland State Highway Administration.

That moves road service groups such as AAA to the first line of defense.

“These Arctic temperatures can be especially hard on vehicles,” said AAA Mid-Atlantic’s Lon Anderson. “Emergency road service calls to AAA, especially for dead batteries and lockouts, always rise sharply when temperatures plunge.”

Anderson tossed out several frigid facts and bits of advice: When the temperature hits zero, a car battery loses about 60 percent of its strength. When car door locks freeze, try heating the key with a match or lighter. Tires lose pressure in the cold, and gas lines can freeze.

Although the movie “Doctor Zhivago” would have you believe that trains run merrily through Siberia all winter, here, Metro’s rails expand and contract with the temperature.

“There’s a potential for rail cracks or breaks,” Caroline Laurin, a Metro spokeswoman, said.

“If a crack or break is detected, we will need to temporarily take that section of track out of service until repairs are made,” she said.

She urged commuters to use smartphones to check the next-bus and next-train features on the Metro’s mobile Web site, to minimize their waiting times at bus stops and outdoor rail stations.

Prince George’s schools will open with a two-hour delay to give maintenance workers enough time to resolve any issues.

“The biggest issue will be broken pipes,” said Sam Stefanelli, the acting director of building services. Stefanelli said that ordinarily the school system turns down the heating system at schools at night to conserve energy. On Monday night, the heat was to stay on to keep water flowing in the pipes.

Stefanelli said teachers in the county’s 540 portable classrooms have individual thermostats so “they are probably better off than anyone.”

Traditionally, Montgomery County’s 202 schools don’t close for cold weather, “but it’s going to be colder than it usually is tomorrow, so we will be looking at it and considering it,” said Montgomery schools spokesman Dana Tofig.

Tofig said the district is prepared for the bitter chill: Buses are heated, as are schools and portable classrooms. “If for some reason, the heater wasn’t working, we would close that school,” he said.

Children assigned to trailers may have to venture outside (for restroom trips, for example), but he said that “in most cases, it’s a very short distance.”

Platenberg said Fairfax County had not canceled school because of cold weather in recent decades. He said school engineers and maintenance workers have been checking on heating units.

“We have also taken some precautionary measures to prevent freezing issues at facilities where we have had similar experience in the past,” he said.

Lori Aratani, Emma Brown, Paul Duggan, Justin Jouvenal, Lyndsey Layton, Robert Samuels, T. Rees Shapiro, Donna St. George and Victoria St. Martin contributed to this report.