Northburn competitors have faced gale force winds and snowstorms in the past, but relentless heat was the leveller this year.
''I guess we're keeping up our reputation for extreme weather and as well as being known for the extreme cold and high winds, we'll add heat to the mix,'' race director Terry Davis said yesterday.
''This year, it's been the toughest conditions we've ever had for competitors.
''We've lost more people from the race this year due to the heat, than we ever did due to the cold or wind in other years.''
Race co-owner and ultra runner Lisa Tamati estimated up to a third of the 120-strong field in the 100 mile, 100km and 50km events pulled out because of the heat.
''It was brutal, especially in the desert-like territory here where there's no shade, '' she said. Competitors in the event, now in its fourth year, had experienced blizzards, sleet and snow and high winds in other years.''
This year, the problem is the weather is so good, we've had a fall-out from the heat,'' she said. Mr Davis said the temperature climbed to more than 30degC on Saturday and extra water was provided for competitors.
''With no breeze it was just relentless on those steep climbs.''
Competitors in the 100 mile race, which began at 6am on Saturday, have until 6am today to complete the course.
''I think last time, our last competitor finished at 5.30 on the Monday - which meant they'd been on the course for almost 48 hours,'' Mr Davis said. He paid tribute to the 50 volunteers who worked at the event, some completing 12-hour shifts as marshalls.
''Our volunteers are just incredible and they help us keep track of where the competitors are, radioing in reports as people go through the various checkpoints.''
The marshalls ranged from teenagers through to 83-year-old Don Morrison, of Alexandra, ''and he scored an all-nighter shift'', he said. Tamati said the event had also gained a reputation for having a great atmosphere.
''People tell us it has a great feel, compared to some other races, where it's all about the elite competitors.''
Just getting over the finish line is an achievement and we celebrate that.''
After 100 miles, winner found the finish 'pretty tough'
Ultra-marathon runner Wouter Hamelinck had no need for a ride from Queenstown airport to Cromwell for the Northburn 100 mile race. He simply jogged there - heavy backpack and all.
But the 60km ''training run'' did not do him any harm. Two days later, he won the event, after running for 24 hours and 33 minutes.
It was his first attempt at the race, which was staged on steep high-country terrain on Northburn Station, near Cromwell, at the weekend.
The 31-year-old statistician travelled to New Zealand especially for the event and camped on site before and after the race.
He was matter-of-fact when asked about getting from the airport to the venue.
''I ran and walked,'' Hamelinck said.
Carrying your own luggage?
''Of course.''
The Northburn was one of about 130 ultra-marathons he has completed around the world in the past decade, winning 25 to 30 of them.
He planned a holiday in New Zealand around the Northburn race and said he was unlikely to defend his title next year: ''It's so expensive for me to get here.''
Hamelinck was impressed by the course and the ''great views'' over the countryside.
''It was a bit hot during the race and I found the end of it pretty tough - but that's often the case,'' he said.
Asked about the toll the endurance race had taken on his body, he said: ''I'm not looking too closely to see.
''There's more general soreness than anything else.''
Ultra-marathon runner Lisa Tamati, who designed the 160km course on Northburn Station and co-owns the race, said Hamelinck was seen as a ''a dark horse'' before the race.
He was one of a growing number of international competitors in the 100 mile (160km) 100km and 50km Northburn events. Almost half the 120-strong field were overseas ultra runners, with athletes from as far afield as Europe, the United States and Japan.
''There's huge international interest in the Northburn event and that will continue to grow as competitors spread the word about it,'' Tamati said.
Second home in the 100 miler was 2012 winner Glenn Sutton, of Dunedin, in 26hr 9min, 14 minutes ahead of first woman Jean Beaumont, of Porirua, and Malcolm McLeod, of Alexandra, who shared third.
United States ultra runner Sage Canaday (28), won the 50km race and set a record time of 4hr 45min, carving 20 minutes off the previous record.
Canaday began competing in ultra-marathons two years ago and won the Tarawera ultra-marathon last weekend.
He said competing in New Zealand was the highlight of his racing career and the Northburn course was ''definitely challenging - lots of ups and downs''.
His girlfriend, Sandi Nypaver, was the first woman home in the 50km race, setting a record of 6hr 8min.
Australian Matty Abel won the 100km men's race and Carla Lucas, of Kurow, won the women's 100km distance.
