NEW YORK, March 16: Airlines were forced to cancel hundreds of flights in the northeast United States on Friday as a winter storm closed in, bringing a grim mixture of snow, sleet and freezing rain.

Up to 45 centimetres (18 inches) of snow were forecast to fall on Friday in upstate New York, while New York City was expecting 20 centimetres, said Kevin Lipton, a meteorologist with the National Weather Service.

Much of the United States has experienced a milder than usual winter with many in the northeast thinking spring had sprung early this week, but Lipton said the flurries were not unusual for the time of year.

“You get snow sometimes in late March, sometimes you get it in April, we even have snow in May. In fact February and March are usually the snowiest months here in the Albany area of upstate New York,” he said.

“This is more normal than abnormal,” he added.

Nevertheless, airlines cancelled flights as a precaution with Delta and budget carrier Jet Blue between them grounding almost 500 flights.

“The reason we do this is that proactively cancelling flights allows Delta to begin re-accommodating customers in advance of a storm,” said Delta spokesman Kent Landers.

“We've learned over time it ensures that we can minimize the delay and cancellation impact throughout the storm.”

JetBlue spokesman Bryan Baldwin said the airline had cancelled more than 200 flights as a precaution, mostly domestic services into and out of New York's Kennedy airport, but expected traffic to return to normal over the weekend.

It has been an unusual year for weather in the northeast with unseasonably mild temperatures in January, when the mercury hit 21 degrees Celsius (70 degrees Fahrenheit), followed by record snow in parts of New York in February.

Spring seemed to have come early this week, when temperatures in New York City briefly hit 21 C, but it proved a brief respite.

Denis Feltgen, a meteorologist with the National Weather Service, said earlier in the year that a moderate El Nino was behind the unusual conditions.

The cyclical phenomenon involves warmer sea temperatures in the Pacific Ocean that raise air temperatures and disrupt normal weather patterns.

The phenomenon is named El Nino -- which means “the child” in Spanish and refers to Jesus -- because its effects are usually noticed around Christmas.

“In a typical El Nino year, and this is certainly one of them, temperatures in the northern half of the country typically average out above normal -- well above normal,” Feltgen said.

A US government report released on Thursday said the Earth had experienced its warmest December-February since records began 128 years ago.—AFP