Heavy rain warnings are in place for central and southern New Zealand, with up to 400mm of rainfall expected in the Westland ranges and Canterbury divide.
MetService said a slow-moving front drifting northwards over New Zealand today and Monday would bring with it heavy northwesterly rain to the western South Island and the Tararua Range.
Severe northwest gales were also possible about the Canterbury High Country, Wellington and Wairarapa.
Orange heavy rain warnings for Westland District and the headwaters of the Canterbury lakes and rivers about and south of Arthur's Pass were in place from this afternoon.
The same warnings were also in place for Tararua Range from 3pm Monday until 4am Tuesday and the ranges of the Buller District from 3am to 5pm Monday.
The Tararua Range was expected to receive 100 to 150mm of rain; the Buller ranges 90 to 130 mm of rain; and 100 to 130mm of rain in the ranges of the Grey District.
The heaviest rainfall was expected in the Westland ranges and Canterbury main divide, where 300 to 400mm of rain was expected. Peak rates of 30 to 40mm/h of rain was expected for both areas on Monday morning.
"Streams and rivers may rise rapidly. Surface flooding, slips, and difficult driving conditions possible," the forecaster warned.
"Clear your drains and gutters to prepare for heavy rain. Avoid low-lying areas and drive cautiously."
The New Zealand Transport Agency said crews were ready to respond to flooding, slips and debris affecting roads and highways.
"Heavy rain means slippery roads and drivers should think about adjusting their speed and travelling distances, avoiding sudden braking, and staying visible," NZTA said.
"People should also avoid travelling through floodwaters where the depth is unclear or there may be hidden obstructions."
Meanwhile, a strong wind watch was in place for Wellington and Wairarapa south of Masterton from noon until 8pm Wednesday; and the Canterbury High Country from 10pm Sunday until 10am Monday.
"Northwest winds may approach severe gale in exposed places," MetService said.
There was a moderate chance the watch would be upgraded to a warning,
Full list of watches and warnings
Heavy Rain Warning - Orange
Tararua Range - from 3pm Monday to 4am Tuesday
Ranges of the Buller District - from 3am to 5pm Monday
Ranges of the Grey District - from 10pm Sunday to 2pm Monday
Westland District - from 12pm Sunday to 1pm Monday
The headwaters of the Canterbury lakes and rivers, south of Arthur's Pass - from 2pm Sunday to 2pm Monday
Strong Wind Watch
Wellington and Wairarapa south of Masterton - from 12pm to 8pm Monday
Canterbury High Country - from 10pm Sunday to 10am Monday
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