(Reuters) - A winter storm pummeled the southern and western United States on Monday, forcing authorities to cancel flights and close schools as most of the country braced for another bout of freezing weather.

A storm warning was issued from southeastern California through Louisiana as an arctic cold front expands south and east after dropping heavy snow on Colorado, the National Weather Service said.

In Denver, residents were digging out from between six and 12 inches of snow (15-30 cm), while higher elevations in the Rocky Mountains got up to two feet (61 cm), the Service said.

The front even sent temperatures tumbling below freezing in parts of Texas and Louisiana and Arkansas, some 25 degrees Fahrenheit (14 degrees Celsius) below average. Sleet and freezing rain was making road travel there treacherous.

More than 1,000 flights were canceled in and out of Dallas/Fort Worth International Airport by early on Monday, according to the airline tracking site FlightAware.

Several school districts around the Dallas-Fort Worth area had canceled class, local officials said.

In Louisiana, Governor Bobby Jindal issued a state of emergency late Sunday due to the storm and potentially hazardous travel conditions, and schools and state offices in 23 Louisiana parishes were closed, his office said.

Meantime, millions of people along the East Coast were in store for another bone-chilling blast of arctic air on the heels of a weekend snow storm, the Weather Service said.

After a brief reprieve on Sunday, residents from Washington D.C. to Boston would see temperatures drop dramatically on Monday.

In New York City, lows could reach five degrees Fahrenheit (minus 15 degrees Celsius).

Last week, a shot of cold air that marched through the Northeast broke decades-old record low temperatures.