Two US students survived a week lost in a blizzard-hit New Zealand mountain range by taking regular dips in hot thermal springs they had stumbled across, rescuers said Monday.

Alec Brown and Erica Klintworth, both 21, had planned a two day trek on the South Island's rugged West Coast but ended up spending more than a week in the wilderness after a snowstorm hit.

West Coast search and rescue leader Sean Judd said that with the ground covered in thick snow, the pair found their exit from the mountain pass where they were trapped blocked by a swollen river.

Rather than try to ford the river they set up hammocks and rationed their supplies of peanut butter, rice, fruit and nuts, he said.

Judd said they also found some thermal springs, which they sheltered in during the worst of the weather.

"In fact, I think when the snowstorm hit, they were sitting in there and quite comfortable really," he told Radio New Zealand.

Judd said the river eventually subsided enough for them to cross and they walked back to safety on Sunday.

He said hot springs were relatively rare in New Zealand and it was doubtful Brown and Klintworth would have survived had they not been lucky enough to find the thermal waters.