Flights Grounded in Texas; Arctic Air Returning to Northeast

— -- More than 1,000 flights into and out of Dallas/Fort Worth International Airport have been canceled today because of freezing rain, sleet and sub-freezing temperatures.

Meanwhile, Arctic air is returning to the Northeast, with chilling temperatures expected later today from Boston to Washington, D.C., following a milder Sunday reprieve.

At least 15 states from North Dakota to Maryland are under a wind chill advisory today. Wind chills in parts of the Midwest could drop to -40 degrees. Wind chill figures in the inland Northeast Tuesday could fall to similar figures -- near -35 degrees.

Winter storm warnings continue for a large portion of northern Louisiana and parts of Texas, Arkansas and Mississippi, which are under winter storm or freezing rain advisories.

One wave of the system moved through the deep south Sunday, producing multiple accidents and spin-offs in Texas and leading authorities at Dallas/Fort Worth International Airport and airlines to take extra precautions. A second round of freezing precipitation is expected in the Dallas area during the morning rush hour, with dangerous travel conditions expected.

In Colorado, people used cross-country skis, sleds and snowshoes as more than 2 feet of snow fell.

Additionally, a new storm system in the Southwest is expected to bring rain and snow to California, Nevada and Arizona.

The Associated Press contributed to this report.