While a high-pressure weather system brought warmer than normal temperatures to Greenland and northern Canada in March 2013, much of North America, Europe, and Asia shivered through weeks of unseasonably cool temperatures.

The contrasting temperatures are no coincidence: the same unusual pressure pattern in the upper atmosphere caused both events.Atmospheric pressure patterns are constantly in flux, as air masses of differing temperatures and densities move around the skies.

Nasa.gov