A polar vortex collapse. Now, meteorologists are calling for another collapse in the middle of March, one that could plunge the U.S., Canada, and parts of Europe into a bitterly cold spell just days before the official arrival of spring.

The National Oceanic and Atmospheric Administration (NOAA) explains that a polar vortex is a large area of low pressure and cold air currents which circulate around both of the Earth’s poles. It has a circular shape and is at it’s peak during the winter months.

A polar vortex collapse is predicted to hit over the coming weeks, resulting in severe winter weather and travel disruptions throughout North America. Parts of the US and Canada are predicted to see very cold temperatures when the weather phenomena develops in mid-March.