An early "March summer" in Canada and the United States with record high temperatures may be a symptom of global warming, researchers said.

Record-breaking summer-like conditions have been reported across North America following an unusually mild winter, meteorologists said.

In Canada, the temperature in Saint John, New Brunswick, hit 77 degrees Fahrenheit on March 21, smashing the previous record high for March of 64 degrees, NewScientist.com reported.

"We've never seen these kinds of temperatures before," Dave Phillips, a senior climatologist at Environment Canada, said. "It's quite remarkable."

"The duration, areal size, and intensity of the 'summer in March' heat wave are simply off-scale," Jeff Masters of the Weather Underground Web site in San Francisco said. "The event ranks as one of North America's most extraordinary weather events in recorded history."

A large loop in the jet stream over the continent, funneling warm air northward from the Gulf of Mexico, remained "stuck" in place for more than a week, a phenomenon known as a blocking pattern, Masters said.

And Phillips points out that air flowing northward in the spring would normally be cooled as it passes over cold, snowy ground, but the mild winter has left very little snow on the ground and the air is hardly cooling at all.

There is evidence global warming can both reduce snow amounts on the ground and influence atmospheric conditions aloft such as the jet stream, researchers said.

"Global warming boosts the probability of really extreme events, like the recent U.S. heat wave, far more than it boosts more moderate events," climate scientists Stefan Rahmstorf and Dim Coumou of RealClimate.org wrote in a blog post.