A sudden stratospheric warming (SSW) is a meteorological event where polar vortex winds in the Northern Hemisphere abruptly slow or reverse, accompanied by a rise in stratospheric temperature. SSWs are classified as major, minor, or final. Major SSWs completely disrupt the polar vortex through wind reversal. Minor SSWs slow winds but do not reverse them. A final SSW occurs on the transition from winter to summer winds and is the last warming of the winter season.