6 signs that this winter's cold has been extreme

It's about to get very cold again in much of Canada. Are you ready?

A "weather bomb" is expected Thursday, bringing cold temperatures and messy weather to Eastern Canada. That will end a brief bump-up to single-digit, below-freezing temperatures in some parts of Canada.

Many Canadians have already made it through some record-breaking cold, and it's not just the numbers on the thermometer that show it — there have been a lot of other signs.

It's been so cold that…

1. Sharks have been found frozen to death on the East Coast.

The Atlantic White Shark Conservancy has so far found three dead male thresher sharks near Cape Cod, Mass., in the past couple of weeks that it said were "likely stranded due to cold shock."

2. The Calgary Zoo brought its penguins indoors.

The zoo's king penguins have been brought indoors multiple times this season, the Canadian Press reports. A zoo guideline says they shouldn't be outside if it's below –25 C, and temperatures averaged –28 C during the last week of December. The penguins are from subantarctic areas where temperatures can get pretty cold, but zookeepers say they want to be safe, given that the animals are not wild.

3. Some Canadian polar bear swims were cancelled for the first time.

The Toronto Polar Bear Club cancelled its annual New Year's Day dip in Lake Ontario for the first time in its 13-year history due to extreme cold and dangerous ice buildup. Shortly afterward in Oakville, Ontario's Courage Polar Bear Dip for World Vision cancelled its event for the first time in its 33-year history.

Instead of swimming in Lake Ontario, some people were skating.

4. Suspected ice quakes damaged homes and produced large cracks in the ground in Alberta Beach.

A spokesperson for the Alberta Energy Regulator said it believed the village of Alberta Beach was hit by two naturally caused ice quakes on Jan. 1. Ice quakes happen when cold winter temperatures quickly freeze groundwater, causing the ground to suddenly crack and make popping sounds.

5. Manatees have been huddling together for warmth at power plants and hot springs.

Reports and images from Florida suggest that manatees have been migrating south in large numbers, seeking warmth at hot springs and power plants in great numbers and huddling together for warmth.

6. Niagara Falls looks amazing.

With the cold temperatures, mist from the surging waters of Niagara Falls has been freezing instantly on everything it touches, coating trees, walkways, cliffs and overlooks in a dreamy, brilliant white, the Associated Press reports. And here are some photos to prove it.