South Island braces for heavy rain, gales

The shortest day of the year is set to usher in heavy rain and strong winds, as a moist northwesterly brings unseasonably warm but unsettled conditions across much of the country.

Weather warnings and watches are in place across western and alpine areas of both islands, including Fiordland, Westland, Buller, Grey, Canterbury, Otago and parts of the lower North Island.

MetService meteorologist Heather Keats told Breakfast the shift was already underway, with conditions deteriorating later Friday as a series of fronts move in.

The system is expected to hit the lower South Island first before tracking north through Saturday and into Sunday, bringing periods of heavy rain and gale-force winds, particularly to western and exposed areas.

“There’s a lot of rain, embedded fronts. It’s going to move up the South Island… and then shimmy over parts of the North Island before petering out,” she said.

Western parts of the South Island were expected to bear the brunt of the system, with heavy falls and strong winds likely to create hazardous conditions.

By the winter solstice on Sunday, however, the rain band was forecast to move further north, bringing showers to more regions, though some areas will still escape the worst.

“That rain will spread north, so we can expect some showers… Auckland looking really good,” Keats said.

“If you want to go to Hawke’s Bay, [it] looks lovely there, actually.”

Daytime highs were expected to climb well above typical winter levels in several centres, with Christchurch forecast to reach 21C on Saturday, while inland areas will also be milder than usual.

“Places like Twizel… will be 15 degrees tomorrow, and overnight lows are sort of eight degrees, and even Hastings will hit 20 this weekend too.”

Keats said attention was already turning to another developing system early next week.

“We’ve got another low-pressure system kind of brewing out over the Tasman Sea. This is going to be the next significant rainmaker for the North Island.”

That system could bring much-needed rainfall to drier eastern regions, before a colder southerly change later in the week returns more typical winter conditions.

“Looks like a southerly shift too later in the week next week, so could be good news for the ski fields,” she said.

Meanwhile, those heading to Wellington for Saturday night’s sold-out Super Rugby final are being warned to prepare for classic capital conditions.

“Take a rain jacket, not an umbrella, because there are strong northwesterlies as well,” Keats said.

“Looks like there’ll be showers for most of the match — not too cold though, only about 15 degrees… so it should be a fun watch.”

NZTA reminded motorists to keep the weather in mind before heading off on any weekend travels on the South Island's state highways.

"Heavy rain means slippery roads and drivers should think about adjusting their speed and travelling distances, avoiding sudden braking, and staying visible (using headlights in daytime hours)," an NZTA spokesperson said.

"People are also urged to avoid driving through floodwaters where the depth is unclear and there may be hidden obstructions."

Those towing vehicles, or driving high-sided vehicles and motorcycles should take extra care while travelling in strong winds.

Full list of weather warnings and watches

Heavy Rain Warning - Orange

Coastal ranges of the districts of Buller and Grey - 15 hours from 11am Saturday to 2am Sunday

The ranges of Westland - 24 hours from 7pm Friday to 7pm Saturday

Headwaters of the Canterbury lakes and rivers south of the Hurunui River – 19 hours from midnight Friday to 7pm Saturday

Headwaters of the Otago lakes and rivers – 16 hours from 10pm Friday to 2pm Saturday

Fiordland – 18 hours from 7pm Friday to 1pm Saturday

Strong Wind Warning – Orange

Canterbury High Country – 12 hours from 3am to 3pm Saturday

Heavy Rain Watch

The Tararua Range – 9 hours from 11pm Saturday to 8am Sunday

Inland ranges of the Buller District and the Nelson Lakes – 15 hours from 11am Saturday to 2am Sunday

Strong Wind Watch

Wellington and Wairarapa south of Carterton – 17 hours from noon Saturday to 5am Sunday

Southland, inland Otago and western Clutha – 13 hours from 9pm Friday to 10am Saturday

Marlborough Sounds and inland ranges of Marlborough – 17 hours from 9am Saturday to 2am Sunday