NEW YORK (AFP) - Hundreds of flights were cancelled or delayed on Wednesday in the US north-east as a winter storm delivered freezing rain and snow ahead of the Thanksgiving holiday, one of the year's biggest travel weekends.

A wintry mix was falling in Boston, Philadelphia, New York and Washington, according to the National Weather Service, which forecast "havoc" for travellers along the east coast from the Carolinas up through New England.

The storm is not predicted to leave more than an inch or two of snow.

But with the American Automobile Association predicting 46.3 million Americans will travel 80km or more for the holiday, most by car, the bad weather could create big problems on highways.

Wednesday morning, more than 100 flights were already cancelled and another 100 were delayed in the three major New York airports.

In Philadelphia, another 33 flights were cancelled and 30 delayed, according to Flightaware.com.

At Reagan International airport in Washington, there were around 20 cancellations and more delays, and flight traffic at Boston's Logan airport was also disrupted.

Thanksgiving, celebrated each year on the fourth Thursday in November, is a popular US holiday.

Americans gather with family for a big meal that traditionally features roast turkey, cranberry sauce, sweet potatoes, and pumpkin pie.