The Iditarod Trail Sled Dog Race is the most popular sporting event in Alaska, and has long been a test of human and animal endurance. Traveling a 1,000-mile path across Arctic tundra from Willow to Nome (with a ceremonial start in Anchorage), mushers and their teams of 16 specially-trained dogs must withstand some of the most extreme winter weather on Earth: blizzards and whiteout conditions, along with freezing temperatures, are commonplace.

The major challenge that mushers had to contend with this year — and that forced many of the more experienced racers out of the event — was not unusual cold and snow. In fact, it was the opposite — a near total lack of snow with ice covering across large stretches of the course. Mushing over snow cover across steep, rugged terrain is difficult enough, but the sleds were not designed for traversing gravel.

Portions of the course did have snow and ice coverage, but overall it was thinner and far more sparse than average, according to race veterans.

The winner, who crossed the finish line at 4:04 am local time on Tuesday morning, was 27-year-old Dallas Seavey, who came back from third-place to win his second Iditarod. Despite the harsh conditions, he managed to finished the race in a record time of eight days, 13 hours, 4 minutes and 19 seconds, according to the Associated Press.

While much of the central and eastern U.S. has shivered through frequent outbreaks of Arctic air and heavy snows, Alaska has had an unusually warm winter. January was its third-warmest such month on record, for example, with an all-time monthly record high temperature of 51 degrees Fahrenheit set in Nome on Jan. 27. The statewide average January temperature was 14.8 degrees Fahrenheit above the 1971-2000 average, according to the National Oceanic and Atmospheric Administration.

The record warmth came courtesy of a large dome of high pressure, which drew relatively mild air north from the Gulf of Alaska, and redirected frigid air masses southeast, into Canada and the U.S. Similar weather patterns occurred at times in February and March, although the warmth in the Frontier State was not as pronounced.

According to a story in the LA Times, even the most experienced mushers could not finish the race this year. “It’s the roughest I’ve ever seen,” Jeff King, a 22-time race finisher, told the Times. Musher Aliy Zirkle said, “No snow. Zip. Zero. None.”

The challenging conditions caused many injuries, with media reports indicating that at least one musher had to be rescued by helicopter after breaking an ankle.