Up to 8cm of snow was forecast in the area today with a wind chill factor of -10C, said search coordinator Senior Constable Dave Colville.
Searchers are hopeful of getting back into the area mid-week when the weather is forecast to clear again.
Police want to speak to a German woman called Angela Bahr who is believed to have spoken with Mr Prehn at one of the huts.
Mr Prehn arrived in New Zealand in October on a one-year tourist visa.
Inquiries by police indicated the pack - which was full of gear and personal items - may have been there for up to a week before it was recovered.
His parents, who are in Germany, have spoken with police in New Zealand.
Anyone with information that may assist this search should call Nelson police on 03 546 3840.