Two trampers survived sub-zero temperatures in the Southern Alps by sitting face to face and putting their feet in each other's jackets, eating muesli bars and nuts.

Sleep was fitful, said Nic Gordon. "Our toes kept us awake."

Mr Gordon and his fellow Canterbury University engineering student and flatmate Craig Helm endured their three-night ordeal with a Snickers bar to spare. Yesterday a 10-minute break in the clouds allowed rescuers to swoop down on a cliff-face above Arthurs Pass and pluck the two day-trampers to safety.

There were tears and hugs as the men told how they tried to keep warm without sleeping bags.

They spent part of Tuesday night sitting with their feet cocooned in each other's jackets.

The old Snickers bar was discovered in a jacket pocket yesterday morning, Mr Gordon said, "so that was a bit of a bonus".

Last night the two men were in Christchurch Hospital for observation - in particular their hands and feet were being checked for frostbite - but both were able to walk from their rescue helicopters and declared themselves to be "feeling pretty good".

It marked the end of a frustrating few days for the search and rescue teams who had pinpointed the lost men on Tuesday morning but were grounded by blizzard conditions high above the tiny Arthurs Pass village.

After miscalculating the amount of daylight they had left, Mr Gordon and Mr Helm were initially stranded by darkness on Sunday night. But in the early hours the weather turned, covering them in snow and cloud.

Their worried girlfriends, who had elected to go snowboarding at a nearby skifield, called police early that evening and remained in their agreed waiting place hoping to see the men walk out during the night.

For rescuers and worried family the most frustrating part was knowing the men were stuck only a few kilometres from the rescue base.

But at 2.20pm an alpine cliff rescue team monitoring the weather from Mt Temple made a hurried call to base and both rescue helicopters were quickly fired into action.

Sergeant Peter Summerfield, who had just over from rescue veteran Senior Constable Phil Simmonds, said the base soon received "a sketchy radio call" to say the men had both been picked up and were heading back to ground.

At about 1pm Mr Gordon and Mr Helm had started walking down the mountain face from the snow trench they had made their home for three nights to look for water.

"We didn't know where we were going, we just thought we'd give it a go," a relaxed Mr Helm said.

Their parents were more emotional. Sue Helm choked back tears as she thanked rescuers and told how she forced herself not to lose hope.

"Last night was the hardest," her husband Barry said.

"It was raining down here [in the village] so we knew it was snowing up there ... We can't thank these wonderful professionals enough."