Even before temperatures plunged into single digits late Monday, phones at the Metro Atlanta Task Force for the Homeless were ringing off the hook.

Paul Ballew, a case manager for the massive facility at Peachtree and Pine streets, said he might get 700 people on a typical winter’s night. This week, he is expecting more than 1,000 a night.

“People are being turned away from other cold-weather shelters, because they are already full,” Ballew said. “Our biggest fear is people dying on the streets.”

Meanwhile, public safety agencies sought to drive home the message that the “polar vortex” slicing through the state could pose serious dangers even for those with a roof over their heads. The Georgia Emergency Management Agency issued a news release urging residents to stock up on emergency rations, dress warmly and avoid prolonged exposure to the elements.

For firefighters, plunging temperatures brought the grim prospect of more house fires as residents turned to space heaters. Home fires are more prevalent in winter, and blazes caused by heating equipment are responsible one in five fire deaths nationally.

Fire officials urged anyone using a space heater to keep it at least three feet from anything flammable, connect it directly to a wall outlet rather than an extension cord, and turn it off when sleeping. Kerosene heaters should never be used indoors, officials warned, because they emit deadly carbon monoxide.

“Carbon monoxide can kill,” said Lt. Colin Rhoden, a spokesman for Gwinnett County Fire & Emergency Services.

The near-record cold snap was good news for one group: schoolchildren. One by one Monday, every major metro Atlanta school system cancelled Tuesday classes.

No precipitation was forecast, but school officials said they were taking the most prudent course.

“More than anything, you have to think about students standing out in sub-degree weather, waiting for buses to show up,” said Thomas Algarin, a spokesman for Marietta schools.

That theme, with minor variations, was voiced by officials at several school districts.

“It’s colder than it’s been in a number of years,” Clayton Superintendent Luvenia Jackson said. “We just want to make sure our children are safe.”

In DeKalb County, school officials pointed out that Southerners generally lack the proper clothing to protect them from sub-zero wind chills such as were forecast Tuesday morning.

“These kinds of temperatures, a jacket and a baseball cap aren’t going to cut it,” said Quentin Fretwell, the DeKalb safe schools coordinator.

Jean Warnken, who has a daughter in fourth grade at Davis Elementary in Cobb County, taught in Cobb for many years and said she couldn’t remember the schools closing just because it was cold. But the decision was fine with her.

“I don’t ever remember it being this cold,” she said. “What if the bus heater broke or something? I’m from the South so I’m not used to this kind of thing.”

Algarin, the Clayton spokesman, noted, too, that extreme cold affects buses as well as the humans. Many school buses run on diesel, he said, and as temperatures approach zero, “diesel changes its form: In cold weather it becomes more like a gel than liquid.”

That fact was very much on the minds of Georgia trucking company executives Monday.

As long as temperatures are above 20 and the weather is dry, the trucks keep rolling as usual, said Brian Kinsey, CEO of Lithonia-based Brown Integrated Logistics, which operates thousands of trucks. Single digits, he said, spell trouble.

“We do expect to see some disruptions at several of our terminals tomorrow through Wednesday,” Kinsey said. “It is going to be a challenging couple of mornings.”

However, for much of the state’s $71 billion agricultural sector, the timing was fortunate.

“The good thing is that the cold came kind of early,” said Mary Kathryn Yearta, a spokeswoman for the Georgia Department of Agriculture. “A lot of farms have just wrapped up getting the crops in – especially the cotton.”

More at-risk are the state’s cattle and poultry operations. Georgia produces about 1.3 million head of cattle and 1.4 million broiler chickens.

The cold may not threaten their survival, but farmers will find it more expensive to manage and transport them, said Michael Lacy, head of the department of poultry sciences at the College of Agricultural and Environmental Sciences at the University of Georgia.

“The poultry in Georgia is all housed in environmentally controlled buildings, so the cold weather doesn’t have an impact on the birds themselves,” Lacy said. “It does have an impact on the cost of raising the birds.”

Those concerns were mild, though, next to the mortal danger facing homeless humans.

Throughout the city Monday, organizations that provide shelter worked feverishly to meet the threat.

“I’m trying to squeeze beds in every single space that I can,” said Janeane Schmidt, director of the Salvation Army’s Red Shield Services. “I just can’t bear to see people out there in the cold.”

Covenant House, an emergency shelter for youth between ages 12 and 21, also expected an influx, said Simone Walker, director of development.

“We’ve already seen more youth in the last few weeks than we did over the summer,” she said.

The city of Atlanta turned a couple of recreation centers into impromptu shelters. Melissa Mullinax, a spokeswoman for Mayor Kasim Reed, said the Adamsville and Ben Hill recreation centers were to remain open overnight.

By early Monday afternoon, men and women were already starting to mill around outside the shelter at Peachtree and Pine.

Donna Pearson, who said she has been on the streets a year, held a crumpled bag of food that someone in a car had just given her — her first meal of the day.

“It is gonna be cold tonight, so I will pray to God and get ready to sleep on the concrete floor. But it is better than being outside all night,” she said.

A few miles away on Edgewood Avenue, beneath an overpass, about 15 piles of trash and blankets lined a fence. Each pile hid a homeless soul.

Cornelius Taylor, 35, said he hoped to spend the night with a friend who has an apartment. He said he spent Sunday night under the bridge, but he wasn’t taking any chances Monday night.

“I hope I find my friends,” Taylor said. “Or I’ll be dead out here.”