The northeastern United States on Friday faced a cold snap so severe that even world-class ski jumpers preparing for a night-time competition at Boston's Fenway Park worried about the frigid weather.

Forecasters warned that temperatures would plummet below 0 degrees Fahrenheit in Boston over the weekend and wind chill warnings were in effect over much of seven states, from New York to Maine, with winds forecast to gust up to 45 miles per hour.

At Boston's historic Fenway Park, ski jumpers were practicing their tricks on a 140-foot-high ski jump covered in artificial snow that towered over the stadium's famed "Green Monster" left field wall.

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Some competitors fretted that the 21 degree Fahrenheit temperatures forecast for the evening would harden the snow make their landings tougher than normal.

"Some of us would have liked it to be a little bit warmer," said Keri Herman, 33, of Breckenridge, Colorado. "The snow is pretty bulletproof."

The storm had officials throughout the region scrambling to prepare shelters for the homeless and urging their residents not to spend too long outdoors when the weekend low temperatures set in.

"Extremely low temperatures present challenges for our city," said Boston Mayor Martin Walsh. "I ask each and every single Boston resident to stay safe and to look after their neighbors."

National Weather Service meteorologists said the conditions would be the coldest seen in the region this year.

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"It hasn't been this cold this winter," said meteorologist Alan Dunham. "The wind chill temperatures will be getting more extreme."

The forecast was so daunting that organizers of New York City's annual Central Park Ice Festival canceled the event, citing "extreme temperatures."

The cold snap follows several weeks of unseasonably warm weather, which caused the organizers of an annual dog sled race in New Hampshire to cancel their event for lack of snow while the course for Maine's U.S. National Toboggan Championships, which draws hundreds of competitors, was shortened last weekend because of thin ice on the pond where racers finish their high-speed runs.

As he oversaw preparations for the final night of the International Ski Federation's "Polartec Big Air at Fenway" competition, Boston Red Sox President Sam Kennedy was breathing a sigh of relief about the cold.

"We were worried about the warm weather," Kennedy said. "Now we have to worry about the wind, but it's been OK."