The plunging polar vortex brought subfreezing temperatures Tuesday to some of the southernmost points of the U.S., threatening to dump snow on parts of Texas and Oklahoma in coming days and contributing to a power outage in Virginia's capital that made the water unsafe to drink.

Multiple rounds of frigid, arctic air could sweep across the eastern half of U.S. in the coming weeks, ushering in an abnormally cold start to 2025.

The cold is expected to persist throughout January, with relief coming once February rolls around. Such plunges occur when the air currents that keep frigid air over the North Pole — the polar vortex — weaken, and the freezing arctic air slips south and pushes the vortex down with it.

In Indiana, the National Guard was activated to help stranded motorists. The storm was expected to reach the Mid-Atlantic states on Monday and bitter cold temperatures could grip much of the East Coast deep into the South.