Extremely cold weather brings special hazards and problems for the unprepared.

The most dangerous are frostbite and accidental hypothermia--abnormally low body temperature. Frostbite can be avoided by covering as much of the body as possible, including the face. Mittens are better than gloves for maintaining warmth. If hands or feet become pale, waxy and without sensation, then cool--not warm or hot--water should be run over them to warm them without accidental scalding.

Older persons are especially vulnerable to hypothermia, which is particularly dangerous since the victim has no sensation of being cold even though the body's temperature is dropping. Keeping room temperature at 68 degrees or above, wearing gloves, warm socks and gloves or mittens even while indoors can help prevent hypothermia. Persons suspected of suffering from hypothermia should be taken to a hospital for treatment. Efforts should not be made to warm them quickly and alcohol should not be given since it reduces body temperature.

Joggers should dress warmly since rapid movement increases the wind chill factor and thus the amount of heat the body loses, according to Dr. Richard A. Kenney of George Washington University Medical Center. Jogging, although good in the sense that it produces body heat, is bad because the increase in air intake can result in irritation of the upper respiratory tract. On balance, Kenney said, "it's better not to jog at the sorts of temperatures we had Sunday morning or yesterday."

For cold weather starting of a car, nothing takes the place of keeping it tuned, according to John Fobian of the American Automobile Association. The best battery in the world won't start a neglected engine. Turning the headlights on for no more than 30 seconds--all other electrical accessories should be turned off--will help warm the battery and improve starting. Beyond that, Fobian recommends that drivers read their owner's manual carefully before trying to start their cars since each car has its own recommended procedure.

Short runs in very cold weather increase the wear on a car and shorten its life, Fobian said. Better to drive a little further--more than five miles--and pay more for gas now, he said, than to take the short route to work and have to pay the cost in repairs to the engine later. Also, it is not a good idea to drive at high speeds soon after starting the car. Fobian said the car should be driven three or four miles at no more than 30 to 35 mph before driving at high speeds.

In the house, cold weather increases the temptation to light a fire which will, paradoxically, wind up making the house colder. Fireplaces require enormous quantities of air and they draw it from the house, resulting in cold air being drawn in from outside as the hot air goes up the chimney.

When attempting to thaw frozen pipes, pouring hot water on a pipe or using an electric hair-dryer is all right, but a blow torch in the hands of an amateur could result in a burst pipe, according to Alvin Sacks of Claxton Walker and Associates, a home inspection service. Pipes under kitchen sinks can be thawed or kept from freezing by leaving the cabinet doors open. Insulation between pipes and exterior walls also can prevent freezing, or electrical tape can be purchased to keep pipes warmer in cold weather. Sacks also recommends checking attics with blown insulation to make sure that air moving through hasn't moved the insulation to one end, leaving bare, uninsulated spots.