<human>:  What is a polar vortex?
<bot>: A polar vortex is a large area of low pressure and cold air circling the Earth near one or both of the Earth's poles, with strong winds and cold temperatures. It is a persistent, large-scale cyclone, typically found in winter, around the poles and at the surface, with localised low-pressure winds circulating counter-clockwise in the northern hemisphere and clockwise in the southern hemisphere.