ATLANTA (AP) — Freezing temperatures and wind speeds are creating dangerously cold conditions in a large part of the U.S. stretching from Montana to northern Florida. The region is not expected to begin thawing out until Monday.

Here are some of the dangers the winter blast poses and how to protect against them:

WIND CHILL

Wind chill describes what the air temperature feels like to human skin from the combination of wind speed and temperature. It is expected to be in the single digits in parts of the southern U.S., including the Florida Panhandle, that are typically much warmer.

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In other places, it will drop below zero. Portions of Kansas will feel like 15 degrees below zero Fahrenheit (minus 26 degrees Celsius) on Saturday, according to the National Weather Service. In other areas, bitterly frigid air from Canada and wind will make it feel like minus 30 degrees Fahrenheit (minus 34 degrees Celsius) outside.

FROST BITE AND HYPOTHERMIA

Forecasters say the risk of developing frostbite and hypothermia increases as the wind chill temperature falls.

Hypothermia occurs when the body’s stored energy is used up, causing its temperature to drop. People who remain outdoors for long periods — such as those who are homeless — are particularly at risk.

A series of storms before this weekend’s cold weather were blamed for at least 55 deaths around the country, many of them involving hypothermia.

In Tennessee, a 25-year-old man was found dead on the floor of a mobile home in Lewisburg after a space heater overturned and turned off, said Bob Johnson, chief deputy for the Marshall County Sheriff’s Office. “There was ice on the walls in there,” Johnson said.

Though less serious, frostbite is also a concern in cold weather. It occurs when skin — and sometimes underlying tissue — freezes. To prevent it, the American Academy of Dermatology advises people going outside to dress in layers and wear two pairs of socks, a heavy wool or fleece hat that covers the ears, a face mask or scarf and insulated mittens or gloves. It also advises people to stay hydrated and avoid alcohol.

In Atlanta, city officials announced two sites where people can go to stay warm will remain open through the weekend.

BROKEN PIPES

Water pipes are at risk of freezing and bursting in cold temperatures. In Memphis, Tennessee, officials urged residents to boil water after days of cold temperatures led to broken water mains.

So many lines broke, that water pressure throughout the city dropped. That could allow contaminants to enter the system.

Forecasters were warning home and business owners as far south as northern Florida to wrap or drain outdoor water pipes to prevent damage. Another strategy is to allow a faucet to drip slowly.

STAYING WARM INSIDE YOUR HOME

Officials say that during a winter storm, people should stay indoors. But home heating systems running for hours can increase the risk of carbon monoxide poisoning as the deadly fumes can be produced by furnaces, stoves and heaters, according to the U.S. Centers for Disease Control and Prevention.

Carbon monoxide can also be created when people use portable generators or run cars in their garages to stay warm or charge their phones. Generators should not be operated inside homes or even in garages, experts say.

BLACK ICE

Snow and ice can make driving and walking treacherous. Heavier-than-forecast snow fell in New York City, Baltimore and Washington, D.C., on Friday.

New Yorkers have been warned that roads could be covered with black ice this weekend. Black ice is a glaze that forms on roads, sidewalks and driveways. It is not easily seen and is often clear, making a black road surface visible underneath. It is most likely to be present during the early morning hours and on bridges, elevated overpasses and shaded spots on the road.

People should avoid driving during such conditions. If they must be on the road, they are encouraged to slow down and maintain even more distance than normal from the vehicle ahead of them. If they do hit ice, they should avoid braking and instead ease off the accelerator. Sudden turns of the steering wheel are also not advised.