Large swathes of the South Island and eastern parts of the lower North Island are expected to face heavy rain and severe gales to kick off the working week.
MetService said a front preceded by a strong and humid northwest flow was forecast to move over New Zealand from Monday into Tuesday.
Potential for 'highly impactful event' as 'volatile' fronts move in - watch on TVNZ+
Heavy rain was forecast for regions including Fiordland, Otago, Westland, Canterbury, Buller, Tasman, and parts of Marlborough.
Rainfall totals could be significant, especially around the main divide and alpine areas, with potential for rising rivers, surface flooding, and slips, the forecaster said.
Strong wind warnings were also issued for exposed areas across Fiordland, Southland, Otago, Canterbury, Marlborough, Wellington, Wairarapa, and the Tararua District.
Gusts could reach severe gale strength of up to 130km/h and may pose a risk to trees, powerlines, and high-sided vehicles, MetService said.
"Prepare your property by securing items that can be picked up by strong winds. Drive cautiously."
On Tuesday, conditions were expected to intensify further in central regions, with watches in place for Hawke's Bay, Horowhenua, the Kapiti Coast and the Tararua Range.
MetService said there was a high chance the Hawke's Bay wind watch could be upgraded to a warning.
West Coast highway reopens following slip
Part of State Highway 73 on the West Coast has reopened to traffic under a temporary 30km/h speed limit after heavy rain caused slips yesterday, the New Zealand Transport Agency Waka Kotahi (NZTA) said.
"Road users are asked to continue taking extra care along this route," a spokesperson said.
Full list of weather warnings and watches
Heavy Rain Warning - Orange
Grey, Buller and Tasman district west of Takaka, also Nelson Lakes National Park and the Spenser and St Arnaud Ranges of Marlborough – 16 hours from 10pm Monday.
Headwaters of the Canterbury lakes and rivers – 17 hours from 11am Monday.
Ranges of Westland – 18 hours from 10am Monday.
Headwaters of the Otago lakes and rivers – 12 hours from 7am to 7pm Monday
Fiordland north of Doubtful Sound – 15 hours from 2am to 5pm Monday
Strong Wind Warning - Orange
Canterbury High Country and foothills of the Canterbury Plains – 14 hours from 9am to 11pm Monday
Otago – nine hours from 5am to 2pm Monday
Fiordland, Southland and Stewart Island – 10 hours from 2am to midday Monday
Wellington, Wairarapa and Tararua District – 20 hours from 10pm Monday.
Marlborough – 22 hours from 2pm Monday.
Heavy Rain Watch
Tararua Range – 11 hours from 6am to 5pm Tuesday.
Strong Wind Watch
Hawke's Bay – ten hours from 10am to 8pm Tuesday
Horowhenua and Kapiti Coast – 15 hours from 2am to 5pm Tuesday
Road Snowfall Warnings
Milford Road (SH94) – two hours from 11am to 1pm Sunday.
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