As Te Papa boss Seddon Bennington and Marcella Jackson walked to their deaths in Tararua Forest Park, MetService was warning of deteriorating weather.
Just hours later, at an altitude of 1400 metres, the pair encountered 80kmh southerly winds that whipped up snow, reduced temperatures to minus 20 degrees celsius and visibility to almost zero.
"It was a blizzard up there," MetService forecaster Steve Ready said. "Trying to keep yourself upright in such atrocious conditions and with that wind-chill, it would have been horrific."
Search and rescue experts say the survival rate in such conditions without a tent would have been "hours rather than days".
Police believe Dr Bennington, 61, and his 54-year-old companion never made it to their destination, Kime Hut.
They could have died as early as Saturday afternoon, and remained covered in snow till found by searchers yesterday morning. Their bodies were just off the track, a kilometre short of the hut and about 300 metres apart.
It was unclear whether they had become separated. Neither appeared to have injuries that indicated a fall.
"It appears they were overcome by the weather conditions," Inspector Mark Harrison of Palmerston North said.
A MetService forecast posted on its website at 3.26am on Saturday warned of increasing cloud, cold southeasterlies rising to gale force, and freezing level dropping to below the pair's destination.
It is not known whether they saw it before departing from Otaki Forks. Dr Bennington was an experienced tramper and he and Mrs Jackson were thought to be well equipped. It is understood both had cellphones.
Family raised the alarm when the pair failed to return on Sunday evening. Police began their search on Monday, and it eventually grew to a 10-team, 50-strong search and rescue operation, using three helicopters to ferry in specialist search teams from as far away as Wellington and Taranaki.
The missing pair's families, who had gathered at the search base in Levin, received the news of their deaths about 11am yesterday.
Dr Bennington had been Te Papa chief executive for six years.
Michelle Hippolite, who shared strategic leadership of the museum, is now acting chief executive.
She said colleagues were devastated. "In the weekends he's out and about, so to learn that he hadn't returned and then to learn later that he'd passed away, it was a shock."
The flag outside Te Papa was lowered to half-mast yesterday, and a memorial area with a photograph and a condolence book will be set up.
Dr Bennington's wife, Frances, from whom he was separated, told The Dominion Post that he was a perfectionist who loved the arts, architecture and tramping. "Where he died is where he would have wanted to die."
He would often take the couple's two sons with him.
"He took the boys tramping, they enjoyed the outdoors with him."
Wellington search and rescue adviser Wayne Stevens could not understand how such experienced trampers had lost their lives, but said if something went wrong in such rough conditions, a person was very vulnerable.
David Naulls, a friend of Mrs Jackson who was known as Rosie for 30 years, said she was a lovely person. "Rosie was very kind and gentle, always watching out for other people."
Mrs Jackson, a widow, was a senior medical laboratory scientist at Aotea Pathology.
Chief executive Karen Wood said she was meticulous about her work in the biochemistry department and had many close friends among the staff, who were devastated. "Professionally and personally she leaves a big gap."
Arts, Culture and Heritage Minister Christopher Finlayson said Dr Bennington had served Te Papa and the people of New Zealand well and would be sorely missed.
Former prime minister Helen Clark, a keen tramper, was deeply saddened. "My heart goes out to his family and the Te Papa family at this sad time."
- By KAY BLUNDELL and TANYA KATTERNS, The Dominion Post