A pair of overdue Canterbury trampers had a lucky escape from predicted bad weather last evening after their delayed arrival at the Wanganui River near Hari Hari prompted a police search and rescue operation.

Greymouth prevention sergeant Paul Watson said the two men aged 30 from Christchurch had headed up through the upper Rakaia River headwaters on November 30 to make their way over the Southern Alps through the Ramsey Glacier and over the top into the headwaters of the Wanganui River.

They were due out at a pre-arranged meeting point by the Wanganui River on Sunday afternoon.

By yesterday they were well overdue and with the weather deteriorating the police launched a preliminary search.

"A friend who was supposed to meet them called the police when they were 48 hours overdue," Mr Watson said.

Police deployed the Franz Josef alpine cliff rescue team which were dispatched into the Smyth Range on the northern side of the Wanganui River where the two trampers were located "safe and well" early last evening.

"The were running short on food and water and were getting quite exhausted," Mr Watson said.

While the men were very experienced and were well prepared, they had not anticipated how difficult it was to descend to the Wanganui River from the Smyth Range.

"They just totally under-estimated the terrain really."

They were carrying a personal locator beacon although this had not been activated.

Luckily their failure to meet their pre-arranged pick up prompted the search - which was timely given the weather was deteriorating at the time.

When found the pair declined to be lifted out and walked out under their own steam, Mr Watson said.

"They were determined to finish it."

Mr Watson praised the efforts of the Franz Josef alpine cliff rescue team which "did an awesome job" searching for the men in the rugged terrain.

- Greymouth Star