Snow storm in rural AmericaThough the holidays were relatively warm this year, forecasts call for a chilly January. Arctic air is expected to blow through most of North America starting mid-month. Several factors are pulling temperatures down, including a La Niña pattern that has been forming in the Pacific Ocean for some time.

Other weather events worldwide can contribute to the cold. For example, the surface temperature of the ocean, thunderstorms near the equator or high-pressure air in the Himalayas and Tibet could potentially change the jet stream, encouraging frigid air to settle over the Northern Hemisphere.

Even so, it seems cold weather in January won’t be due to a change in the polar vortex so it won’t be as cold as it could have been.

Read more on expected weather conditions here.