Wednesday will be the busiest travel day of the year in the United States, and it could be a rough one for millions of people.

A major winter storm called a nor'easter is forecast to hit the Eastern seaboard from Maine to North Carolina — the day Americans hit the roads, rails and skies for Thursday's Thanksgiving holiday.

Major Storm Could Snarl US Holiday Travel

Meteorologists said coastal regions could expect heavy rain and high winds, while some areas to the west could see as much as 40 centimeters (15 inches) of snow.

Major Storm Could Snarl US Holiday Travel

Large cities including Boston, New York and Philadelphia will feel the impact.

Major Storm Could Snarl US Holiday Travel

Travelers are warned to get an early start and to expect delays at airports.

Conditions are expected to be much better for Thanksgiving Day, when families gather to enjoy turkey dinners, football and parades.