Two foreign tourists rescued after a freezing -19 degree Celsius night on a Nelson Lakes mountain should not have been in the area, a DoC worker says.

The pair, an Irish woman and a Latvian man both in their 20s, were unable to be rescued by helicopter on Sunday morning due to high winds and bad weather, but a team of rescuers did reach them and warmed them up from their hypothermic states.

They were picked up at about 1pm during a break in the weather and were checked over by an advanced paramedic who determined they should not need further medical treatment.

Nelson Marlborough Rescue Helicopter A rescue helicopter is unable to reach two trampers stuck in the Nelson Lakes, due to high winds and bad weather.

Department of Conservation conservation services manager John Wotherspoon later said it was disappointing people had been up on the mountain given the bad weather that had been forecasted.

"It was well predicted, it did exactly what it said it would do," he said.

"If they were in a hut and the weather was bad they should have just stayed in the hut. You don't set off late in the afternoon, which is sounds like they did, to head away in deteriorating weather, that just doesn't make sense."

He said too often people made the mistake of going into the Nelson Lakes area without adequate experience or equipment, or without taking heed of the weather forecast.

Peoples' safety was their own responsibility, but DOC was there to give information, he said.

"Always check the weather forecast. Make sure you don't go anywhere where you don't have the right experience or equipment to take on that sort of country and if you're unsure talk to the front desk staff in the visitor centres they'll give you good information, and people should follow it."

Wotherspoon said he did not think the pair had gone to the visitor centre to ask for information about the route.

The pair became stranded after the woman fell on the route from Mt Angelus to Speargrass on Saturday evening, at an altitude of 1600 metres. It was snowing at the time.

The man went to assist her, then the pair called police at 5.45pm, search coordinator senior constable Dave Colville said.

"Why they were up there so late, I'll never know."

A police search and rescue team reached the trampers at 5.30am, and erected tents to try and warm the patients up. A doctor was among the rescuers, Colville said. The trampers were found 25m below the saddle in a hypothermic state, unable to assist themselves or rescuers. There was a wind chill of -19C and heavy blowing snow.

Colville said the rescuers had warmed them and their body temperatures had risen taking them out of danger of being hypothermic.

Neither of the trampers was injured, he said. Their level of experience and equipment was not yet known.

Colville said the first rescue team to reach the pair early on Sunday had done an outstanding job to bring them back from a severely hypothermic state prior to the helicopter's arrival.

Colville said the trampers were extremely lucky to have been rescued as their condition when they were found meant they were unable to help themselves.

"Without a doubt if they didn't have a cellphone and couldn't call us they would've been brown bread (dead)," he said.

"They might've survived to the morning but they couldn't walk out as their boots were frozen solid."

Police were speaking to the pair at St Arnaud.

The Nelson Marlborough Rescue Helicopter was able to fly the two search teams out as well.