There was a climate change in Saskatoon New Year's Eve - and it had nothing to do with the temperature plummeting to -31C.
This shift took place in the hockey rink where, for the first time since the World Junior Hockey Championship got underway in this city, there was tension on the ice.
There always is, of course, whenever Canada and the United States meet at the men's, women's or junior level in the game that Canada gave the world but cannot bear the world actually taking.
This game was hardly life-and-death - the loser would play stumbling Finland while the winner would receive a bye into the semi-final; Sweden in Group A would also receive a bye while Russia and Switzerland would meet to see who continues on - but it was played at gold-medal intensity right from beginning to Alex Pietrangelo's short-handed goal that spoiled the American party and put the 4-4 match into overtime.
When five minutes of overtime solved nothing, a shootout was held, with all three Canadian shooters - Jordan Eberle, Nazem Kadri and Brandon Kozun - scoring while the Americans scored twice, the 5-4 victory giving Canada the prized bye to the semi-finals.
It marked a magnificent comeback from being down two goals to the Americans well into the third period.
"That's the big thing with Canadians," said Eberle, who also scored twice in regulation.
"We believe - we don't expect to lose."
Nor did the Americans this night, having gone ahead 4-2 on a surprising two shorthanded goals and completely stymieing the vaunted Canadian power play.
"We let it slip right at the end," said a disappointed Jordan Schroeder, who played a terrific game but was unable to score when it mattered most in the shootout.
To no surprise, this heartstopping game - complete with a U.S. penalty shot that Canadian goaltender Jake Allen turned aside -- was the best match of the tournament, just as the best last year had been the New Year's Eve meeting between Canada and the United States, a game that saw Team U.S.A. spurt ahead 3-0 only to have Canada claw its way back on a John Tavares hattrick to a 7-4 win.
Two years earlier, it was again Canada vs USA in a semi-final match that went to a seven-round shootout - Canada's Carey Price taking care of the goaltending and Jonathan Toews scoring three times in the shootout to send Canada to the gold medal game, which they won by beating Russia 4-2. The Americans, however, had proved the tougher opponent.
It isn't always a fairytale story for the Canadian juniors over the Americans. In 2004 the Sidney Crosby-led Canadians took a 3-1 lead, only to have Team USA tie the game in the third period. Then, with time winding down, Canadian goaltender Marc-Andre Fleury made a clearing mistake and bounced the puck off his own defenceman into the Canadian net to give the Americans their first-ever gold medal in the World Juniors.
It is, in so many ways, an acquired hate, and a shared one.
It can be seen in any match between the only two women's teams that matter, the Canadians and the Americans, where suddenly the "incidental contact" of the women's game ratchets up to solid contact and punches have even been thrown.
The rivalry was seen most dramatically at the 1996 World Cup, where U.S. forward Keith Tkachuk blithely told the media that "They hate us and we hate them."
Tkachuk also said the Americans felt "There's no point in winning this thing without going through Canada" - which the Americans promptly did. That American victory was avenged six years later in Salt Lake City, when Team Canada took the Olympic gold medal by defeating Team USA 5-2.
This bitterly cold New Year's Eve in Saskatoon saw both coaches fully aware that tension and rivalry and emotion would likely factor as much as skating, skill and shooting.
"We have to get in the game, stay in the game, and not get too rattled," said U.S. head coach Dean Blais, though his team seemed clearly rattled as Canada began its third-period comeback.
"There will be lots of emotion," said Team Canada coach Willie Desjardins, "and you've got to stay under control
"We know it's going to be a big challenge."
Part of meeting that challenge involved Desjardins electing to start Allen in goal. After playing the first two games - a 16-0 shellacking of Latvia and a 6-0 victory over Switzerland - Allen had a chance to tie a World Juniors record with a third shutout. That possibility vanished less than four minutes into the game when U.S.A. matched Canada's early opening score by Stefan Della Rovere.
At Wednesday evening's team dinner, Olympic team executive director Steve Yzerman mad a surprise appearance, wishing the young Canadians luck and leaving a simple message: "Stay calm for the whole game."
It turned out to be sage advice.
Those who had played last year in Ottawa knew exactly what he meant. Eberle, who scored twice in regular time, recalled how "hyped up" he and his teammates were when they skated out on the Scotiabank Place ice surface. That over-abundance of energy almost doomed
This year, they almost doomed themselves by a slow start. Desjardins thought his team "didn't play good, [while]the U.S. just played unreal. We were lucky tonight.
"They played a smarter game than we did tonight."
"Good teams find a way to win," said American coach Blais.
And on this night, two good teams found a way to give Saskatoon a New Year's Party it won't soon forget.