A couple were rescued after spending hours stuck in the cold on Mount Robert in Nelson on Saturday.

Nelson Police Sergeant Steve Savage says the couple were tramping about 700 metres from Angelus Hut but could not continue because of insufficient gear for the alpine environment.

They found themselves on a snowy ridge in the dark, but were able to find cellphone coverage.

They called police, and the Nelson Marlborough Rescue Helicopter located them around midnight.

"Both were feeling the cold, but otherwise in good health," said Savage.

"This is a route in which conditions can change from being hot and sunny to strong winds, snow or rain with subzero temperatures in the matter of one hour."

Savage says the couple were lucky to be located as they did not have enough gear to spend the night out in the snow.

There have been two fatalities in this area in recent years, and numerous lives saved.

Advice for trampers:

"A quality PLB can be purchased for under $500 which will last up to 10 years, that's $50 a year to potentially save your life, alternatively you can hire them from various trusts for the price of a box of beer," said Savage.

Distress beacons work almost anywhere in the world, showing rescuers the user's approximate location, taking the "search" out of search and rescue.

"The sooner rescuers can help you, the more likely you are to survive."

Police say trampers should not be afraid to turn back when it becomes clear that they will not make it to their destination.

They should also have another location organised to tramp to in case the weather at the first location is not right.

People heading into the mountains should seek information from Department of Conversation visitor centres or via the DoC website for weather forecasts, track issues and snow conditions.