The SurfAid International aid organisation says a massive storm has moved into Indonesia's Mentawai Islands region making tsunami relief work difficult.
More than 400 people are confirmed dead after a tsunami was triggered by a 7.7-magnitude undersea earthquake on Monday.
Another 160 people are still missing and 27,000 were made homeless.
The storm is forecast to last up to four days and is creating hazardous ocean conditions for both the 150km crossing from Padang and access to the isolated villages.
SurfAid New Zealand's founder Dave Jenkins, says the weather is going to delay an already extreme challenge.
He says nine SurfAid boats, which include speedboats and luxury charter boats, are having difficulty getting to villages on islands tucked behind coral reefs.
130 missing people found alive
More than 130 people listed as missing after the tsunami have been found alive on high ground on a remote island, off western Sumatra.
A disaster management official said the missing people had been too scared of another tsunami to leave the forests and hills above their shattered homes.
SurfAid says it has been appointed as the lead Non Governmental Organisation and is co-ordinating the relief effort.
Chief executive Andrew Judge says the Indonesian Vice-President has asked for an assessment of the scale of the disaster.
Mr Judge says SurfAid is expanding its operations to complete that task, so it can help get to the areas in greatest need.