More heavy rain is forecast to fall in already wet parts of the West Coast, Otago and Southland, MetService says.
MetService said heavy rain was forecast for those areas today and into tomorrow morning.
It said a front was to move northeast across the South Island, bringing rain that could cause surface flooding and slips, and could make driving hazardous.
Westland south of Otira was expected to get a further 150mm to 200mm in the ranges on top what had already fallen, with 70 to 90mm near the coast, MetService said.
The headwaters of the Otago Lakes and Rivers could get up to 110mm near the main divide, and Fiordland north of Doubtful Sound could get a further 50mm on top of what has already fallen.
Rain watches are in place for Buller and the Canterbury lakes from the Rakaia River southwards.
Heavy rain caused severe flooding on the West Coast late last month, washing out parts of an old landfill near Fox Glacier and damaging Waiho Bridge, closing access between Franz Josef and Fox townships on State Highway 6.