A polar vortex has tens of millions of people caught in its grasp. But what exactly is a polar vortex?

In this episode of the Global News podcast This is Why, Global News meteorologist Anthony Farnell chats with Niki Reitmayer and examines the cold snap that is sending shivers through the spines of a lot of people.

Also, senior digital journalist for Global National, Jeff Semple, talks about his new podcast Russia Rising, as he investigates how Russian internet trolls operate and whether other countries, specifically Canada, are targeted too.

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