Two under-prepared trampers who got lost in Golden Bay in bitterly cold weather over the weekend "put themselves and their rescuers at risk", say police.

The pair, a Christchurch man and woman in their mid- to late-20s, entered the Boulder Lake track near Takaka late on Saturday afternoon and became lost in darkness and horrendous weather.

The trampers became wet and freezing, and one tramper developed hypothermia. The pair called police about 8.30pm.

Searchers were able to locate the trampers' exact position using "mobile locate" technology and rescue teams were dispatched.

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The Nelson rescue helicopter had to be called in due to the pair's remote location and the deteriorating conditions.

The helicopter was unable to rescue the pair until 3.40am due to the extreme weather.
Sergeant Malcolm York said the rescued trampers were at real risk of losing their lives, and search and rescue staff were also put in danger.

He said police were disappointed with the decisions the trampers had made.

"They were inexperienced for the route and the weather they took on.

They were woefully under-prepared and the equipment and clothing they were using was not appropriate for the winter alpine environment."