Heavy rain is set to hit Fiordland and Westland, while a strong wind watch is in place for Southland from late tonight.
MetService says a front is forecast to move out of the Tasman Sea and across the lower South Island overnight Wednesday and Thursday, preceded by a period of heavy rain for western regions and northwest gales.
In Southland, an orange rain warning north of Doubtful Sound is in place from midnight today until 1pm tomorrow and MetService advised 80mm to 100mm of rain was expected.
Heavy rain was also expected to hit the ranges of the Westland District from 3am tomorrow until 2am on Friday.
MetService said 130 to 180mm of rain was forecast. Peak rates of 15 to 25 mm/h were expected tomorrow afternoon and evening.
However, conditions were likely to ease from the Glaciers southwards from late afternoon.
A heavy rain watch is in place for Fiordland about and south of Doubtful Sound, and Southland, west of Lumsden, from 10pm today until 9am tomorrow.
The Buller and Grey Districts south of Hector were also in for a period of heavy rain from midnight tomorrow until noon on Friday.
Rainfall amounts may approach warning criteria, especially about the ranges.
Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips were also possible and driving conditions may be hazardous.
Meanwhile, a strong wind watch has been issued for Fiordland and Southland, including Stewart Island, from 3pm today until 2am tomorrow.
Northwest winds may approach severe gale in exposed places, MetService said.
