Nineteen competitors are braving Arctic conditions as they run through northern Yukon and the Northwest Territories in the 6633 Extreme Ultra Marathon this weekend.

Dubbed by organizers as the "toughest, coldest and windiest extreme ultra marathon on the planet," the race began Friday morning in Eagle Plains, Yukon, north of the Arctic Circle.

Competitors are running — and pulling all their gear in sleds — in one of two distance races: 193 kilometres to Fort McPherson, N.W.T., or 563 kilometres to the banks of the Arctic Ocean at Tuktoyaktuk, N.W.T.

"The racers were pretty much all organized last night. They had all their kit packed and ready to go," Stan McNevin, owner of the Eagle Plains Lodge, told CBC News on Friday.

"It was a matter of putting as much breakfast into the guys as we could and as much hot water as we could possibly muster up for them, and they were good to go at 9."

The first runners are expected to arrive in Fort McPherson sometime on Saturday night.

British runner aims for record

Among the participants in this year's race is Mike Buss, a former British soldier who plans to run the 193 kilometres to Fort McPherson within 36 hours.

Soon after he finishes that race, Buss said he will travel to Africa to compete in a 256-kilometre race across the Sahara Desert.

Buss said he hopes to set a world record for completing consecutive ultra marathons, as well as raise money for British military veterans' groups.

"One person had tried to do it last year and didn't complete the two ultras, so I'll become the first person on the planet to run an Arctic ultra and a desert ultra race back to back," he told CBC News earlier this week.

Buss said he is raising awareness about the issues former British soldiers face, such as mental-health problems and homelessness, after they leave the military.