The last people to see missing American tramper Ed Reynolds alive say the weather conditions were bad and forecast to deteriorate.

Edward Dale Reynolds, 39, has not been seen for five weeks but police were only alerted to his situation earlier this week, when he failed to pick up gear from friends as arranged and missed his flight back to the United States.

An Interpol spokesman in Wellington said Mr Reynolds' bank accounts had not been touched since February 22, which was also the last entry date on his adventure blog.

The entry details Mr Reynolds' South Island tramping and hitchhiking trip through Picton, St Arnaud, Westport, the Heaphy Track, and Nelson.

He wrote of the dangers of tramping in rugged South Island back country and his desire to cover tracks at speed.

Mr Reynolds was last seen on February 23, when he breakfasted with three New Zealand trampers at Blue Lake.

"They said he was chatty and cheerful, but there was steady rain, predicted thunderstorms and it was cold with snow on the tops," Nelson search incident controller Senior Constable Dave Colville told The Press.

A check by searchers on Wednesday revealed Mr Reynolds' note in the national park's East Matakitaki Hut intention book, saying he was leaving the hut on February 24, intending to tramp over the Spencer Range and exit at Lewis Pass.

The tramp should have taken two to three days.

Eight South Island search teams are expected to finish scouring tracks near the Lewis Pass today.

Nelson assistant Search and Rescue co-ordinator Sherp Tucker said Mr Reynolds was a fast tramper who carried about 10kg of gear, minimal food, a sleeping bag and tent, and wore running shoes or sneakers and light clothing.

He was not carrying an emergency locator beacon.

"There is no room for error in what he takes," he said.

Hanmer Springs police constable Chris Hughey, who spoke to the missing man's Pennsylvania family yesterday, said "his mother is not coping well" but his father was remaining positive.

"It's a delicate situation and they have got their fingers crossed," he said.