Visitors to the Tasman Glacier in the South Island need to take extra care in coming days as rain has made a large part of the ice mass unstable, a glaciologist warns.
Some 250 millimetres of rain has filtered through the glacier at Mt Cook raising its height to create a tall turquoise mass that could detach itself within days.
Glaciologist Trevor Chinn told Checkpoint when part of the glacier breaks off it may cause a massive surge of water.
That could pose dangers for anyone close to the water's edge at Lake Tasman and he is advising people to stick to higher vantage points.
"The whole thing is very unstable because the glacier has stayed the same size throughout a whole lot of climate warming in the last 100 years and it now has to shrink its size back to fit the climate."
Tasman Glacier is New Zealand's longest glacier, measuring 4km wide and 600 metres deep.