A colder-than-normal start to spring is in the cards for the U.S. Northeast this year, signaling an extended heating season in the world's largest heating oil market, forecasters say.

"For the remainder of winter and the first half of spring, temperatures will be a little below average in the Northeast ... then in the second half it will start to go above average," said Jeff Johnson, long-range forecaster at DTN Meteorlogix.

Forecasters say spring-like temperatures which straddled the 60s Fahrenheit in some areas of the Northeast last week gave way by Thursday to below normal temperatures in the 20s to 40s Fahrenheit (minus 7 to plus 4.5 Celsius) in the region.

"The milder temperatures in the Mid-Atlantic on Wednesday will be a thing of the past on Thursday," Weather.com said in its near-term outlook, adding it sees cooler temperatures from New York State to New England with highs running below average.

"Expect temperatures to range from the teens in far northern Maine to the 20s and 30s over upstate New York and the 40s in southern New England," it said on its website.

Forecasters say the intermittent cold this month could even return snow and bitter cold back to parts of the Northeast.

Manager of Energy Weather Matt Rogers at EarthSat, a Rockville, Maryland-based private forecaster, says he is looking at highs in the low-to-mid 30s in New England by mid-March, well below last weekend temperature highs in the 60s.

"March is looking like an extremely volatile month for the Northeast," Rogers told Reuters. "There is more cold on the way but it's back and forth ... It will be a little of everything."

AccuWeather.com Chief Long-Range Forecaster Joe Bastardi said in a recent forecast a so-called negative North Atlantic Oscillation Pattern (NAO) is notorious this time of year and could lead to storminess along the Eastern Seaboard.

"March and April are predicted to be colder-than-normal months, but by May, the weather will warm above normal across much of the country as true spring finally starts," he said.

"Each warm surge that we see in the next couple of weeks won't be the true end of winter," he added.

Agrees Johnson of Meteorlogix also sees a continuation of the NAO pattern which essentially causes cold air masses from Canada to slide down into the eastern United States.

"We've seen a lot of that this winter, with a tendency for cold air extending its stay in the Northeast; we are likely to see this pattern hang on," Johnson told Reuters.

Johnson, based in Minneapolis, Minnesota, also expects a colder-than-normal start to spring for the Northern Plains and Great Lakes region where bitter cold currently holds.