Weather: Buller residents spend another night away from homes, Marlborough roads remain closed after flooding

The aftermath of damaging floods across the top of the South Island and West Coast is expected to be revealed on Monday.

Roads throughout Marlborough remain closed or have limited access on Monday morning, including State Highway 65.

In Buller, those evacuated at the weekend have spent another night out of their homes as emergency management crews assess their properties.

The Ministry for Primary Industries is working with groups on the ground to support farmers dealing with the devastating aftermath, Agriculture Minister Damien O'Connor said.

States of emergency remain in place for both Buller and Marlborough.

"If you have evacuated, please stay where you are until you are given the all-clear to go home," Civil Defence said in an update on Sunday.

"Stay away from floodwater. Always assume that all floodwater is potentially contaminated.

"Travel around the West Coast and Marlborough is still limited, and people should not travel unless absolutely necessary."

The Government said on Sunday it would contribute $600,000 to help residents affected by the floods.

"While it is too early to know the full cost of the damage, we expect it to be significant and this contribution will help communities to start to get back on their feet," acting Emergency Management Minister Kris Faafoi said.

"I know it's been a really rough weekend for the people of Buller, Marlborough and Tasman and I'd like to acknowledge how disruptive and distressing this flooding has been for all affected communities.

"This has been a massive effort with multiple agencies working across a range of areas." 

State highways that remained closed overnight included SH65 between SH6 and Spring Junction and SH6 between Renwick and Tophouse in the top of the South Island, and SH6 between Inangahua and Westport and SH6 between Murchison and Inangahua, the NZ Transport Agency said.