A major winter storm continued to bring heavy snow, sleet and freezing rain from the Midwest to the mid-Atlantic region, leaving at least six people reported dead.

Officials in Jackson County, Mo., said a 61-year-old man died on Sunday when he was struck by a sliding dump truck. In Wichita, Kan., a 24-year-old man and 26-year-old woman were killed in a rollover crash, when the vehicle they were traveling in spun out on the interstate and flew down an embankment, police said.

States of emergency were declared in seven states and the District of Columbia, where 16 inches of snow was forecast. Up to 18 inches of snow fell in Kansas, forcing the closure of I-70. More than 5 feet of snow was reported in western New York.

More than 1,900 flights in and out of the U.S. were canceled on Monday, and more than 5,000 were delayed. Hundreds of thousands of utility customers were without power.

The storm’s arrival comes as an Arctic air mass is expected to send temperatures plunging as far south as the Gulf Coast. Forecasters say those frigid temperatures will likely remain through mid-January.