WASHINGTON (Reuters) - Record-breaking cold gripped the United States from Texas to New York on Friday, causing school closures and snarled traffic, as a storm that dropped roughly 2 feet (61 cm) of snow on some eastern parts of the country moved out to sea.

Forecasts called for temperatures 10 to 30 degrees below normal through Friday in the eastern and southern United States, with unusual cold continuing through the weekend.

Snowfall and blustery weather forced public schools in the metropolitan areas of New York and the District of Columbia to cancel classes.

Just shy of 800 flights had been canceled and nearly 2,300 delayed nationwide as of Friday afternoon, according to FlightAware.com. On Thursday, there were 4,957 cancellations and 4,528 delays.

The National Weather Service warned of flooding and told commuters from the lower Mississippi valley to the mid-Atlantic to be wary of dangerous road conditions created by the snow, ice and slush.

Low temperatures shattered records in Texas, Arkansas, Louisiana, Mississippi, Kentucky, Ohio, Illinois, Michigan, Maryland, Virginia, Pennsylvania and New York, said NWS meteorologist Bruce Terry.

"Even in the deep South, it's very, very cold," Terry said. "It will be another cold night tonight. But we are at the end of this record-breaking cold spell."

Saranac Lake in New York's Adirondack Mountains was the coldest spot in the country on Friday, with the mercury registering minus 29 degrees Fahrenheit (minus 33 degrees Celsius), he said.

Cities reaching new lows for the day included Detroit at zero F (minus 17 C), breaking the previous record of 2 degrees F (minus 16 C) set in 1901. The temperature in Austin, Texas, reached 21 degrees F (minus 6 C), breaking the previous record of 28 F (minus 2 C) set in 2011.

In Kentucky, where cities were buried under as many as 23 inches (58 cm) of snow, Governor Steve Beshear declared a state of emergency on Thursday as traffic was halted on interstate highways and motorists were stranded.

Stalled tractor-trailers were removed from Interstate 65 overnight, and traffic was inching along the major commuter route by Friday morning.

Parts of Massachusetts got up to 12 inches (19 cm) of snow, but Boston only received trace amounts, NWS meteorologist Bob Oravec said. The city would have needed 2 inches (5 cm) to break its annual snowfall record of nearly 108 inches (274 cm) set in the year that ended in June 1996.

(Reporting by Ian Simpson and Curtis Skinner; Additional reporting by Barbara Goldberg, Laila Kearney in New York and Steve Bittenbender in Kentucky.; Editing by Gareth Jones, Lisa Von Ahn and David Gregorio)