Three new search teams and a search and rescue dog have joined the hunt for missing tramper Alistair Levy in Kahurangi National Park.
Search co-ordinator Sergeant Mike Fitzsimons said intermittent rain and limited visibility was expected to clear later today.
Levy reached the summit of Mt Owen on Sunday and had been expected to join wife Tracy and other family members in Christchurch on Monday.
The search for him started on Christmas Day in rugged country.
Police yesterday found a bicycle left by the 54-year-old Palmerston North teacher at the Kohatu cafe where he had arranged to leave it with the cafe owners.
Fitzsimons said it supported the theory that Levy had intended to tramp from Mt Owen and use the bike to get back to his vehicle parked at Courthouse Flat.
Helicopter pilot Tim Douglas-Clifford, who used night-vision goggles to search yesterday morning, described the area as hostile terrain and said the search was challenging.
"Going out on the south side, it's very steep, with a lot of caves, big craters, jagged rocks and deep crevasses. It drops down into heavy bush and it's almost impossible to see through," he said.
It was an area where the ending of the first The Lord of the Rings movie was filmed.
Christchurch man John van den Bosch, a friend of Levy's for more than 20 years, described him as a highly experienced tramper who meticulously planned his trips.
"He has this great ambition to cover the whole of the South Island from north to south," he said.
Van den Bosch, who used to live in Palmerston North, accompanied Levy on many trips in the 1990s. They included a six-day crossing of the South Island from the West Coast to the Rakaia Gorge.
Levy tried to get others to go with him on tramping trips but it did not always suit them, he said.
Levy is believed to be carrying a purple and black backpack. He did not have an emergency locator beacon.
It was raining in the area yesterday but the weather was expected to clear today.
Search teams remained in the area overnight and the search continued today.
Police would like to speak to anyone who has been tramping around Mt Owen since Saturday. Anyone with information is asked to call the Nelson police on 03 546 3840.
- The Press
Which memorial design do you like most?Related story: Christchurch earthquake memorial designs unveiled