Query: This means the jet stream meanders more, with big loops bringing warm air to the frozen north and cold air into warmer southern climes.”

Relevant passages:
Early 2014 North American cold wave <=SEP=> The 2014 North American cold wave was an extreme weather event that extended through the late winter months of the 2013 -- 2014 winter season , and was also part of an unusually cold winter affecting parts of Canada and parts of the north-central and upper eastern United States . The event occurred in early 2014 and was caused by a southward shift of the North Polar Vortex . Record-low temperatures also extended well into March .   On January 2 , an Arctic cold front initially associated with a nor'easter tracked across Canada and the United States , resulting in heavy snowfall . Temperatures fell to unprecedented levels , and low temperature records were broken across the United States . Business , school , and road closures were common , as well as mass flight cancellations . Altogether , more than 200 million people were affected , in an area ranging from the Rocky Mountains to the Atlantic Ocean and extending south to include roughly 187 million residents of the Continental United States .

Jet stream <=SEP=> Jet streams are fast flowing , narrow , meandering air currents found in the atmosphere of some planets , including Earth . On Earth , the main jet streams are located near the altitude of the tropopause and are westerly winds ( flowing west to east ) . Their paths typically have a meandering shape . Jet streams may start , stop , split into two or more parts , combine into one stream , or flow in various directions including opposite to the direction of the remainder of the jet . The strongest jet streams are the polar jets , at 9 - above sea level , and the higher altitude and somewhat weaker subtropical jets at 10 - . The Northern Hemisphere and the Southern Hemisphere each have a polar jet and a subtropical jet . The northern hemisphere polar jet flows over the middle to northern latitudes of North America , Europe , and Asia and their intervening oceans , while the southern hemisphere polar jet mostly circles Antarctica all year round .   Jet streams are the product of two factors : the atmospheric heating by solar radiation that produces the large scale Polar , Ferrel , and Hadley circulation cells , and the action of the Coriolis force acting on those moving masses . The Coriolis force is caused by the planet 's rotation on its axis . On other planets , internal heat rather than solar heating drives their jet streams . The Polar jet stream forms near the interface of the Polar and Ferrel circulation cells ; while the subtropical jet forms near the boundary of the Ferrel and Hadley circulation cells .   Other jet streams also exist . During the Northern Hemisphere summer , easterly jets can form in tropical regions , typically where dry air encounters more humid air at high altitudes . Low-level jets also are typical of various regions such as the central United States .   Meteorologists use the location of some of the jet streams as an aid in weather forecasting . The main commercial relevance of the jet streams is in air travel , as flight time can be dramatically affected by either flying with the flow or against , which results in significant fuel and time cost savings for airlines . Often , the airlines work to fly ` with ' the jet stream for this reason . Dynamic North Atlantic Tracks are one example of how airlines and air traffic control work together to accommodate the jet steam and winds aloft that results in the maximum benefit for airlines and other users . Clear-air turbulence , a potential hazard to aircraft passenger safety , is often found in a jet stream 's vicinity , but it does not create a substantial alteration on flight times .