OKLAHOMA CITY (AP) _ Commuters contended with treacherous roads Monday from the southern Plains to the Northeast as a storm spread a coating of ice and freezing rain linked to at least 12 traffic deaths.
Thousands of people had no electricity and airline flights were canceled Monday in Oklahoma.
Winter weather warnings and advisories were posted along a cold front that stretched from Texas to New Hampshire. The wintry weather was expected to continue through midweek.
Oklahoma was especially hard hit, with more than a quarter-million customers blacked out Monday morning as ice-laden trees crashed onto homes and power lines. Schools were closed across the state and the Highway Patrol discouraged travel.
Ice accumulations already a half-inch thick were reported Sunday in parts of Oklahoma and could build up to as much as an inch thick in the Oklahoma City metropolitan area, the weather service said.
Most morning flights were canceled at Oklahoma City's Will Rogers World Airport, where two of the three runways were iced over.
Oklahoma utilities said about 300,000 homes and businesses were blacked out Monday, mostly in the Oklahoma City and Tulsa areas. There was no way to estimate when power might be restored, said Oklahoma Gas & Electric spokesman Gil Broyles.
``This is a big one, we've got a massive situation here and it's probably going to be a week to 10 days before we get power on to everybody,'' said Ed Bettinger, a spokesman for Public Service Company. ``It looks like a war zone.''
The Oklahoma City suburb of Jones, a town of 2,500 people, had very low water pressure because there was no electricity to run well pumps, and firefighters said an early morning fire destroyed most of the local high school.
The utility AmerenUE said more than 30,000 customers remained without power Monday in Missouri and roughly 11,000 were blacked out in southern Illinois. On Sunday, blackouts affecting thousands of customers also were reported in parts of Illinois and Kansas.
The sound of branches snapping under the weight of ice echoed through Oklahoma City neighborhoods.
``You can hear them falling everywhere,'' Lonnie Compton said Monday as he shoveled ice off his driveway.
In the Northeast on Monday, many schools across upstate New York were closed or started late because of icy roads. Last Monday, a mixture of snow, rain and sleet closed schools across a large area of upstate New York state.
On ice-covered Interstate 40 west of Okemah, Okla., four people died in ``one huge cluster of an accident'' that involved 11 vehicles, including a tractor-trailer rig, said Highway Patrol Trooper Betsey Randolph. All 11 vehicles burned, she said.
Eight other people also died on icy Oklahoma roads. In addition, a transient died of hypothermia in Oklahoma City, the state medical examiner's office said.
Missouri Gov. Matt Blunt declared a state of emergency Sunday and activated the National Guard to aid communities affected by the storm.
In Chicago, poor weather and low visibility forced the cancellation of more than 400 flights Sunday at O'Hare International Airport, authorities said. Several flights were canceled at Kansas City International Airport and at Lambert International Airport in St. Louis.