Polar Vortex

Explanation :

Polar Vortex is a band of winds around the poles that keeps the cold air locked near the poles itself. The polar vortex extends from the tropopause, (8–11 km in altitude), to the stratopause (50–60 km in altitude).

How does Polar Vortex affect the Climate?

When the Polar Vortex is strongest, cold air is less likely to plunge into the US & Eurasia as air is trapped into that vortex, but sometimes this vortex is disrupted (breaks into sister vortex) or it shifts southwards, due to wave energy propagated upward from the lower atmosphere (troposphere). This shifting of the Polar Vortex southwards led to sudden gust of chilled and frozen air into the US /Eurasia.

Source: IE