Science of Weather: Different Air Masses 02:23. If you hear a meteorologist, say stormy weather is expected, we didn't just pull it out of thin air. Instead, we looked at weather models predicting ...

About 200 people gathered Wednesday in Resolute Bay, Nunavut, for an open house to celebrate the 51st anniversary of the Polar Continental Shelf Program, which helps researchers in Canada's Arctic.

The polar vortex changes periodically, allowing very cold air to move south. (Courtesy of NOAA) When there are extreme events like wind chills 50 below zero and actual temperatures not far off ...

Our cold air this week — continental polar air — arrived from the Nunavut region of Canada where temperatures are 20 to 40 degrees below zero. It’s also completely dark up there.

Continental tropical: hot and dry airmasses that form over the deserts of the western U.S. Maritime polar: most commonly helps form storm systems that move over the pacific northwest.