The extreme weather is being caused by the polar vortex, an area of cold air that circulates around the Arctic.

Watch a live tracker of a powerful winter storm that is expected to bring heavy snow and significant ice across much of the U.S. over the weekend and into Monday.

A winter storm system is expected to bring up to eight inches of mixed precipitation to the St. Louis area, with areas north of I-70 seeing mainly snow, areas south of metro St. Louis facing significant icing, and the metro area in a transition zone with many forms of winter precipitation in the forecast.

Currently, a winter storm watch is in effect for Sunday and Monday in Central Indiana, but what does that actually mean? What about a winter storm warning?

On Saturday at 3:02 a.m. an updated winter storm watch was issued by the NWS Blacksburg VA valid from Sunday 7 a.m. until Monday 7 p.m.

The National Weather Service has issued a Winter Storm Watch that goes into effect starting Sunday morning for Butler, Champaign, Clark, Clinton, Darke, Greene, Logan, Mercer, Miami, Montgomery, Preble, Shelby, and Warren counties in Ohio through Monday evening. It also includes Randolph, Union, and Wayne counties in Indiana.

A winter storm watch was issued by the National Weather Service on Saturday at 7:13 p.m. valid from Sunday 7 p.m. until Monday 7 p.m. for Washington and Westmoreland counties.

A winter storm watch for central and southern Indiana has been upgraded to a warning as the state braces for cold temperatures.

The severe weather, spanning from the Midwest to Washington DC, is a "potential disaster", says one forecaster.

The National Weather Service has upgraded a winter storm watch to a winter storm warning for central and southern Indiana, which is expected to receive up to 8 inches of snow on Sunday. The warning will remain in place from Sunday morning until Monday afternoon.