MetService has issued a severe weather warning for parts of the the South Island, with heavy rain expected in Fiordland, Westland and the Otago and South Canterbury headwaters until Tuesday morning.
Meteorologist Ciaran Doolin said more than 500mm of rain could fall in some of those areas, meaning rivers and streams would rise rapidly and flash flooding and slips were likely.
"Some of the accumulations we're expecting are quite substantial, even for the West Coast, which is pretty used to rain."
Mr Doolin said the severe weather was likely to spread to Southland and Clutha districts tomorrow.
