It's a warm, slushy anniversary for the Canadian Ski Marathon.

The 160-kilometre course from Gatineau to Lachute, Que., — which organizers call the largest cross-country ski event in Canada and the oldest in North America — is turning 50 years old this weekend.

Despite warm temperatures and the constant threat of rain, more than 2,400 skiers are churning their way through the trails, said marathon director Frédéric Ménard.

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As fireworks explode in the distance, skiers leave the starting gate at the Canadian Ski Marathon in west Quebec. (CBC)

Part of the reason why the two-day marathon has been so popular, Ménard said, is because skiers can devote as much effort as they want to it.

"You can be a gold coureur de bois, start at 5:30 [a.m.] before the sun comes up. You ski with your head lamp. You sleep outside with the fire camp," said Ménard.

"Or, you're just a kid, you want to ski 12K? That's great. We're open-minded and we just want to have fun, enjoy the Canadian winter."

The CBC's Steve Fischer was at the marathon, and sends back this report.