The foundation shook and windows shattered Sunday morning when a propane-fueled auxiliary heating unit pressed into service due to the subzero cold exploded outside an apartment complex in ­Rogers. Some residents were knocked off their feet or out of bed by the blast but no one was seriously injured.

As dangerous cold settled over much of Minnesota Sunday morning, 400 to 500 residents of the Preserve at Commerce, a 192-unit complex at 13600 Commerce Blvd., fled their apartments into the frigid air, one wearing only boxer shorts and another without shoes or socks. Most were allowed back into their homes by midafternoon, but 10 to 12 units still need repairs, Rogers Police Chief Jeff Beahen said.

Metro area temperatures sank to the 20s below in the ­predawn hours Monday, while the day’s high is forecast to be 15 below, 5 degrees lower than the point where boiling water tossed in the air turns to snow. A windchill of 50s below meant that bare skin will freeze in less than 5 ­minutes. A thaw isn’t ­predicted until Friday.

Preparations were largely in place o keep as many people out of the cold as possible. Utilities have ramped up staff to handle ­electrical outages and furnaces that quit working.

Xcel reported more than 300 customers were without power in Maplewood until at least 1:30 a.m. Dakota Electric reported that 1,100 customers lost power around 4 a.m. in Lakeville and Burnsville. Power was restored within the hour.

The Salvation Army Harbor Light Center, St. Stephen’s Shelter, the Dorothy Day Center and other adult shelters are keeping their doors open 24 hours a day. YouthLink, a ­drop-in center for young people, ages 16 to 24, said it would stay open around the clock until 8 a.m. Wednesday.

YouthLink executive director Heather Huseby said two or three people stayed overnight Saturday. She expected five or six Sunday and a whole lot more Monday. Minneapolis police kept an eye out for homeless or vulnerable adults who need a place to stay, said spokesman John Elder. Although people can’t be forced to go into shelter, “we have other places, detox and other places we can take them,” he said.

Hennepin County Medical Center didn’t see any frostbite or hypothermia Sunday; Regions Hospital in St. Paul has treated two cases of frostbite in the past three days.

Schools closed

On the order of Gov. Mark Dayton, schools statewide will be closed ­Monday. Some businesses, such as 3M, told employees to take the day off, too.

Jefferson Bus Lines canceled some routes Sunday and Monday, including Minneapolis to Duluth, Duluth to Fargo, N.D., and shuttles between Minneapolis and St. Paul.

Patrick Hogan, a spokesman for the Metropolitan Airports Commission, said the cold isn’t likely to affect air travel out of the Twin Cities.

The Duluth International Airport, however, reported that United flights between Duluth and Chicago had been canceled for Sunday and Monday. That’s likely because of the snowstorm in Chicago, though, rather than the bitter cold.

Meanwhile, AAA, Xcel Energy and CenterPoint Energy geared up to handle service calls if cars and furnaces quit Monday.

Lest the animals be forgotten, the Facebook pages of animal rescue and advocacy groups urged pet owners to bring their animals indoors.

Water main break

In Chanhassen, three restaurants on W. 79th Street — Applebee’s, Buffalo Wild Wings and Chipotle — had to close Sunday night due to a water main break. About 9:30 p.m., the city announced that crews repaired the break.

The cause of the explosion in Rogers on Sunday wasn’t known, the police chief said. The State Fire Marshal’s Office and the Office of Pipeline Safety were there to investigating. After the initial blast, fireballs continued intermittently for 35 to 40 minutes until authorities found and shut off the fuel valve.

Centerpoint’s Virden said the apartments were using an auxiliary heating unit because they have an “interruptible contract” with CenterPoint.

The contract is optional and is used when there is peak demand for natural gas, she said. That type of contract allows large businesses to use alternative heat sources for, at most, a couple of days and to save money on their gas rates.

Apartment residents had the good fortune of living close to two emergency destinations: a multi-screen movie theater and the Hampton Inn, just down the street.

Nathan and Kerry Hochhalter and their two children stayed at the motel overnight so that broken glass could be cleaned from their apartment. They were a little unsettled by the explosion outside their building. But being from North Dakota, they weren’t fazed by the wind and cold.

“People here comment about the wind and I say, ‘This is nothing compared to what we’re used to,’ ” Kerry ­Hochhalter said.