Weather: Ferries cancelled amid significant swells, heavy rain warnings for Coromandel, Bay of Plenty

Ferry sailings have been cancelled and motorists are being warned snow could cause potential disruption to travel tonight.

The interislander has cancelled sailings across the end of the week with significant swells and high winds forecast for the Cook Strait.

It was a wet Wednesday for much of the upper North Island, with heavy rain pelting Auckland, Northland, and Great Barrier Island.

Interislander said its 3.30pm sailing between Wellington and Picton and 9.30pm sailing from Picton to Wellington were cancelled on Thursday.

On Friday its 3.30am and 3.30pm sailings between Wellington and Picton were cancelled and its 9.30am and 9.30pm sailings between Picton and Wellington were too.

Interislander said all impacted passengers were being contacted directly and moved to alternative sailings or refunded.

A heavy rain warning had been issued for the Coromandel Peninsula until 8pm, as well as the Bay of Plenty, west of Kawerau, until 3am on Thursday, and inland parts of the Tasman District, west of Motueka, until midnight, as a low over the Tasman Sea moves closer to New Zealand.

MetService was forecasting up to 100 millimetres of rain.

A peak of up to 40 millimetres per hour was "likely" in localised downpours, with thunderstorms also possible.

MetService is also forecasting rain will turn to snow and impact some South Island's highways including parts of State Highways 73, 7, 8 and 94 as well as the Crown Range Road.

Transport Agency contractors will monitor the highways tonight and close roads or introduce restrictions where necessary.

They are advising motorists to check the latest weather reports and highway updates.

MetService has issued an Orange Wind Warning for Wellington, Marlborough east of Seddon and the Marlborough Sounds from Thursday night through to Friday evening.

NZTA said road users needed to be ready for strong winds, particularly drivers of high-sided vehicles (vans, trucks, campervans), towing vehicles, light vehicles, and motorcyclists.

"Caution will be needed on exposed routes like Wainui Saddle on State Highway 1 Transmission Gully and State Highway 2 Remutaka Hill. Cyclists and pedestrians should also exercise care on the Ngauranga to Petone shared path," the agency said.

"This will affect traffic on State Highway 1. People travelling between Picton and Ward should exercise caution on the route."

The agency said the severe winds also increased the risk of treefalls, downed power lines, and wind-blown debris.

"Road users must be prepared for such hazards and drive to the conditions."

Meanwhile, an Orange Rain Warning had been issued for inland parts of the Tasman District, west of Motueka from 11 am to midnight on Wednesday.

"This bad weather will affect State Highway 60 - Tākaka Hill and Tākaka Valley," the agency said.

It said road users could expect wet weather driving conditions and were encouraged to drive with caution.

"This means reducing speed, increasing following distances, avoiding sudden braking, using headlights when visibility is poor, and being ready for hazards such as localised flooding, slips and rockfalls."

Swell warnings

Wellington Civil Defence Emergency Management said a swell warning was in place for the southern coasts of Wellington and Wairarapa, but it was unlikely there would be any evacuations.

Metservice said waves rising to six metres could be expected early on Friday morning. with waves peaking near seven metres late on Friday morning.

However, Wellington Civil Defence Emergency Management said the swell heights in the warnings were not currently forecast to be at the same level as a few weeks ago.

It said significant impacts to roads and properties weren't expected at this stage.

A strong wind warning had also been issued for Wellington, also Marlborough east of Seddon, and the Marlborough Sounds, from 8pm on Thursday to 6pm on Friday.

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Northern parts of Auckland saw between 30 to 40 millimetres of rain earlier on Wednesday.

A strong wind watch was also in place for Northland, north of Whangārei, from 9am to 6pm on Thursday, Taranaki from 7pm on Thursday to 6pm on Friday, Horowhenua and Kapiti Coast from 8pm on Thursday and 3pm on Friday, as well as Buller, Grey, and Westland from 1pm on Thursday and 10am on Friday.

MetService meteorologist John Law said the weather was the result of low pressure pushing rain across from Northland west to the Bay of Plenty, while another front was moving up the country from the South Island - reintroducing some colder air.

He said the eastern coast of the Coromandel and the Bay of Plenty would likely get the most rain.

The cold air returned the risk of some snowfall over the higher mountain passes in the South Island, Law added.

MetService have issued a road snowfall warning for Lewis Pass or State Highway 7 from 3am on Thursday to 8am on Friday, Arthur's Pass or State Highway 73 from 11pm on Wednesday to 9am on Thursday, Porters Pass or State Highway 73 from 11pm on Wednesday to 3am on Friday, Lindis Pass or State Highway 8 from 5pm on Wednesday to 11am on Thursday, Milford Road or State Highway 94 from 4am to noon on Thursday, and Crown Range Road from 5am to noon on Thursday.

Further down the North Island, ferry operators Bluebridge has cancelled over half of its sailings tomorrow with heavy swells forecast through the Cook Strait.

Bluebridge has cancelled its 8.15 am, 1.30 pm and 8.30 pm sailings between Wellington and Picton and its 2pm and 7.15pm sailings between Picton and Wellington.

Strong winds and large swells, including throughout the Cook Strait, were expected until Saturday.

MetService issued a heavy swell warning for Wellington - Cape Terawhiti to Turakirae Head - and Wairarapa - Turakirae Head to Flat Point - from 3am to 6pm on Friday.

It warned of southerly combined waves rising to six metres early Friday morning, peaking around six metres late Friday morning, then easing Friday afternoon, as well as a southerly swell rising to between five and six metres Friday morning, then gradually easing Friday afternoon, and southerly wind waves of between three and four metres.

Interislander and Bluebridge are monitoring the weather, and say trips may have to be delayed or cancelled if conditions worsen.

Meanwhile, the National Institute of Water and Atmospheric Research (NIWA) had also warned of "active weather" on Wednesday.