Heavy rain warnings have been issued across parts of the country this King's Birthday weekend, as a slow-moving weather system brings the possibility of heavy rainfall and strong winds for the start of the meteorological winter.
MetService said an "active trough" embedded in a humid, northerly air was forecast for the long weekend, with prolonged heavy rain forecast for northern and western regions of the South Island before approaching the North Island on Monday.
An orange heavy rain warning was in force for the Tasman District northwest of Motueka, with between 400m to 500m of rain forecast and the possibility of 600m during peak conditions.
Heavy rain warnings were also in place for the ranges of Buller, the Richmond and Bryant Ranges including the Rai Valley, Westland south of Hokitika, Fiordland north of Charles Sound and the headwaters of the Canterbury Lakes and Rivers.
MetService meteorologist Gerard Bellam told 1News the Tasman District would be the likely "pinch point" of the long weekend's wet weather, with moisture-laden northerlies from the system intensifying rain in the region.
"The warm, moist air will come straight down onto the Kahurangi ranges, which enhances the rainfall," Bellam said.
"Because of that, there is a moderate chance of upgrading to a red warning in that area."
Strong north to northwest winds were also expected in the Canterbury High Country on Sunday, with a wind watch in place for possible severe gale conditions in exposed areas.
Heavy rain was expected to spread into the North Island from Monday, with Northland and Taranaki Maunga under heavy rain watches.
MetService said further watches and warnings were likely to be issued as the trough progressed, with rain expected to continue into Tuesday across much of the country.
Temperatures 'way above normal' for start of winter
Bellam said the system marked a sharp change after a prolonged period of settled and dry weather across much of the country.
“We’re on the turn really. Today’s the last of the settled weather,” he said.
The wet weather followed what had been an exceptionally dry May for many regions, with Christchurch, Ashburton, Timaru, Whanganui and Palmerston North all tracking towards their driest May on record.
Despite the incoming rain, temperatures were expected to remain unusually mild for the start of winter, with a strong northerly flow keeping overnight conditions well above average.
Bellam said some northern areas would stay warm overnight, with Kaitaia forecast to remain around 18C, while Alexandra was expected to sit near 8C — significantly higher than typical early winter lows.
"It's very warm. A lot warmer than usual," he said.
The winter season was already forecast to bring a mixed bag of conditions, with talk of a potential super El Niño bringing extreme rainfall, heat, drought and destructive flooding around parts of the world.
Full list of watches and warnings:
Heavy Rain Warning - Orange
Tasman District northwest of Motueka - 41hrs from 9am Sunday to 2am Tuesday.
Ranges of Buller - 36hrs from midday Sunday to midnight Monday.
Richmond and Bryant Ranges, including the Rai Valley - 40hrs from midday Sunday to 4am Tuesday.
Headwaters of the Canterbury Lakes and Rivers - 37hrs from 6am Sunday to 7pm Monday.
Westland south of Hokitika - 42hrs from 2am Sunday to 8pm Monday.
Fiordland north of Charles Sound - 12hrs from 6am to 6pm Sunday.
Heavy Rain Watch
Northland - 25hrs from 11am Monday to midday Tuesday.
Taranaki Maunga - 33hrs from midnight Sunday to 9am Tuesday.
Headwaters of the Otago lakes and rivers - 12hrs from 6am to 6pm Sunday.
Strong Wind Watch
The Canterbury High Country - 12hrs from 5am to 5pm Sunday.
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