A state of emergency has been declared in Marlborough, with more heavy rain expected to fall on the water-saturated region overnight.
Mayor John Leggett says it will ensure the emergency response team has the resources it needs to support communities affected by heavy rain.
He says the Rai River had its biggest flood on record last night and the Tunakino Valley has had more than 760 millimetres of rainfall since Tuesday. Leggett says communities in Canvastown and Rai Valley are cut off from Marlborough and Nelson, with roads damaged by flooding and slips.
He says access in and out of the Marlborough Sounds was also very fragile.
There is also new damage to the Kenepuru Road and Queen Charlotte Drive, Croisilles Road French Pass and Port Underwood Roads that could be worse than the damage caused last July.
SH6 is currently open to residents only between Rapaura Road and Havelock. From 7pm tonight, SH6 will be reclosed for all traffic from Rapaura Road/SH62 to Hira.
MetService is expecting another 140-190mm of rain to fall about the ranges and 70-110mm elsewhere.
Meanwhile, Nelson's mayor said every part of the city has been hit by flooding and slips.
Hundreds of evacuated people will have to spend another night away from their homes with more heavy rain setting in tonight.
Rachel Reese told Checkpoint that she did not yet have a figure for the number of houses that are uninhabitable, but it was a grim situation.
Reese said the council was working as hard as it can to assess damaged homes.
See how the day's events unfolded with RNZ's live blog:
