Extreme cold can bring frostbite and hypothermia. Here are the symptoms to watch for

CTV National News: Maritimes in partial darkness CTV’s Hafsa Arif reports on some Maritimers being without power and running water after frigid temperatures broke weather records.

Canadians will continue to bundle up in the country's east this weekend as a recent bout of extreme cold persists in much of Quebec and the Atlantic provinces.

Extreme cold and snow squall warnings were in effect for many parts of Quebec, the Maritimes and Newfoundland and Labrador as of Saturday morning as a cold snap, brought in part by the Arctic's polar vortex, swept through the country this past week.

Thousands of people in the Maritimes have lost power due to the cold, while the opening of the Quebec Winter Carnival was postponed a day.

Although this blast of winter weather should be "short lived," Environment Canada senior climatologist David Phillips told CTVNews.ca previously, with temperatures expected to rise by the end of the weekend, experts say there are a number of signs of frostbite and others symptoms to watch for if exposed to extreme cold.

"If you start feeling unwell, that's a bad sign," Dr. Christopher Labos, a cardiologist at McGill University, told CTV Montreal on Wednesday.

"If you start losing the sensation in your fingers because they're getting cold, go inside and warm up. If you start seeing that you're neurologically a little bit sluggish, if you're stumbling a little bit, that's a sign that you've been out for too long. Get inside."

If you start hyperventilating or notice your heart is beating faster, Labos says that's another reason to get indoors.

Other cold-related symptoms cited by Environment Canada include shortness of breath, chest pain, muscle pain and weakness, numbness and colour change in fingers and toes.

Frostbite, the federal department says, can develop within minutes on exposed skin, especially with wind chill.

Labos says when exposed to extreme cold, the body tries to maintain its core temperature by increasing the heart rate and constricting the blood vessels to prevent heat loss.

After a while, the body is no longer able to maintain its core temperature and the opposite begins to happen — the heart rate slows, blood pressure drops, people start feeling sluggish and potentially fall into a coma, which Labos says is how people die from cold exposure.

"A lot of these things are reversible. All you have to do is warm up again and that's sort of the key point," he said.

WHO IS MORE VULNERABLE?

While everyone can be affected by extreme cold, some people are at greater risk.

These include infants and children, older adults, people with pre-existing medical conditions, those who lack proper shelter, newcomers to Canada, outdoor workers and sports or outdoor enthusiasts, the Simcoe Muskoka District Health Unit in Ontario says.

The Nova Scotia government adds that anyone with previous cold injuries, who suffers from fatigue, uses nicotine or certain medication or has a low calorie intake is also more vulnerable.

Labos says dehydration will put you at a higher risk along with drinking alcohol.

Despite popular belief that alcohol warms you up, Labos says it actually does the opposite and can make cold exposure even worse – the U.S.-based Mayo Clinic says alcohol causes your blood vessels to expand, resulting in more rapid heat loss.

A condition such as diabetes can "blunt" the body's response to cold exposure, Labos says, while anyone with cardiovascular issues that put more strain on the heart can also cause problems.

"If you have to do an outdoor activity like shovelling your driveway, the best thing to do is to break it up, go inside and warm up, because that's going to reverse all of these things before they start to cause permanent damage to your body, which happens in the later phases," he said.

With files from CTVNews.ca Writer Alexandra Mae Jones, CTVNews.ca Writer Daniel Otis, CTVNewsAtlantic.ca Digital Co-ordinator Stephen Wentzell and The Canadian Press