Parts of the South Island are in for heavy rain and possible severe gales today.
MetService has issued a severe weather watch, as a weather system moves slowly northwards across lower and central parts of the island.
A front, preceded by a strong and moist northwesterly flow, was expected to move slowly northwards over the lower and central South Island on Sunday and Monday.
"Expect heavy rain in the west of the South Island and about the headwaters of the Otago and Canterbury Lakes and Rivers. Also, severe gales could affect exposed parts of the lower and central South Island."
A heavy rain warning is in place for the headwaters of the Otago lakes and rivers from noon on Sunday until 3am on Monday.
Expect 110 to 150mm about the divide, with 80 to 110mm within 15km east of the divide. Peak rates of 15 to 25mm/h expected about the divide.
A heavy rain warning is also place for Westland and south of Otira from 3pm on Sunday until 3am on Monday.
Expect 110 to 160mm of rain to accumulate about the ranges, with 70 to 100mm near the coast. Peak rates of 15 to 25mm/h and possible thunderstorms from Sunday evening.
The rain was set to clear south of the glaciers early on Monday morning.
In Fiordland about and north of Doubtful Sound, expect a further 100 to 130mm of rain on Sunday to accumulate on top of what has already fallen.
From mid-afternoon on Sunday the Canterbury lakes area can expect heavy rain, possibly reaching warning criteria.
Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.
There could also be strong winds in the Canterbury High Country and about and south of Arthur's Pass from Sunday morning until 6am on Monday.
North to northwest winds may approach severe gale at times, MetService said.
Meanwhile, strong north-to-northwest winds are likely about Fiordland, inland Otago, Clutha and northern and western parts of Southland on Sunday.
The winds were expected to ease in the afternoon.