Up to 700mm of rain has fallen in the area in the last 12 hours. MetService meteorologist John Law told First Up that Kahurangi National Park, Collingwood and Tākaka had been the most affected.
Nelson Tasman Civil Defence said about eight properties had been evacuated.
It said the worst affected areas were Riwaka, Wakefield and Spring Grove.
Several sections of State Highway 60 between Riwaka and Collingwood are closed due to flooding, treefall and downed powerlines.
State Highway 6 from Pelorus Bridge to Canvastown also remains closed due to flooding.
Civil Defence said conditions were starting to settle on Tuesday morning.
But while the heavy rain is abating, drivers are still being urged to take care and drive to the conditions.
MetService now has no severe weather watches or warnings in place for the area.
Earlier, MetService urged those in Golden Bay, Nelson and the entire Northland region to prepare for potential flooding.
NZTA advises that the bad weather and heavy rain has closed more roads overnight. Drivers should delay their travel and avoid affected areas until highways reopen.
Roads closed are:
• SH6 - Pelorus Bridge to Canvastown, flooding
• SH60 - Tākaka to Collingwood, flooding
• SH60 - between Park Avenue and Central Tākaka Road, treefall and downed powerlines. Local road detour available via Dodson Road.
• SH60 - between Riwaka River Bridge and Riwaka Kaiteriteri Road (Cook's Corner), flooding
