OKLAHOMA CITY -- Despite the fact that winter is still technically a week away, the country's is caught in the middle of an early and especially frigid cold snap.

Winter Weather | Windchills | Car Care

Temperatures are expected to fall below zero Wednesday in at least 12 states in the Midwest and West. Winter weather advisories are already in effect across the Midwest, and from Texas to New England.

A band of snow, freezing rain and sleet has also been stretching from Kansas along the Ohio Valley to Maine. The weather service has posted winter storm warnings for the Ohio Valley and parts of the Southwest. New Mexico had numerous school closings, including those in Albuquerque.

In Chicago, more than 300 flights were canceled at O'Hare Airport, and about 50 at Midway Airport. In northern Texas, police closed some highway overpasses because of ice. Glazed roads were also a problem in parts of Oklahoma.

Snow was the headache in Kentucky, where up to a half-foot fell in some areas. One police dispatcher called the roads "pretty treacherous." Dozens of schools closed in Kentucky, Arkansas and Tennessee.

The cold wave and storms that accompanied had been blamed for at least 20 deaths, including 11 in traffic accidents.

An avalanche in Colorado killed a Ski Patrol member. Exposure likely killed an 87-year-old man found outside his Montana nursing home. Weather-related car accidents are responsible for three deaths in Oklahoma and two each in North Dakota and Missouri.

The California Highway Patrol said winter rain is responsible for the death an officer who was directing traffic around a vehicle that crashed in the rain east of Los Angeles. He was hit by a car that went out of control.

Another death involved an armored truck that slid off a wet highway in the San Diego area and rolled down an embankment.

In Anaheim, the roof of a classroom at a medical training school collapsed. Several people were taken to hospitals.