The country is about to be “plunged into winter” with snow to sea level possible in Canterbury and Otago by the weekend, according to the MetService.

A list of 21 rain and wind warnings and watches are in place as a winter blast is set to converge on both islands.

The South Island’s orange-level rain warnings cover the Tasman District, west of Motueka, from 6am on Wednesday; and Marlborough, northwest of the Richmond Range, and Nelson, east of the city, from 9am.

Orange warnings for the North Island kick in for Taranaki Maunga from 7am; Northern Taihape and the southern parts of Taupō and Taumarunui from 10am; the Tararua Range from 11am.

Most of these places can expect up to 150mm of rain with peak intensities of 20-30mm per hour, though the upper slopes of Taranaki Maunga could see heavier rain of up to 220mm.

A further orange heavy rain warning is in place for Bay of Plenty, east of Whakatāne, and inland Gisborne/Tai Rāwhiti from 8pm on Wednesday into Thursday morning.

Heavy rain watches are in place for Fiordland, north of Breaksea Sound, overnight; and Horowhenua, Kāpiti Coast and Wellington from Wednesday morning.

Similar watches are in effect from Wednesday afternoon for Northland, Auckland and Great Barrier Island; Buller and Grey Districts south of Karamea; and Westland District, north of Fox Glacier.

Concern over downpours

MetService head of weather news Heather Keats described the list of warnings and watches as “huge” as the system begins to affect the country.

She said “significant” wind and rain watches were in place, with some areas under orange rain warnings.

“There’s also thunderstorms again tied up in this system. So as the fronts travel across, they’re going to possibly bring more downpours and we’re expecting them to spark up from this afternoon…

“We’re talking again from about Westland all the way up the west of the entire North Island and as far east as Bay of Plenty.”

They could deliver up to 40mm of rain in an hour, Keats said, and a potential for flooding.

“That warm northerly system meets a very biting southerly and that’s when the snow kicks off from about midnight tonight.”

Canterbury, excluding Banks Peninsula, was under a heavy snow watch, with snow expected to fall above 300m, Keats said.

There was the potential for snow at sea level for Otago and Canterbury from overnight on Friday.

“So Christchurch, Dunedin you could be seeing some snow for winter as early as Friday night, Saturday.

“It does feel like we’re going to be plunged into winter because this biting southerly is for the entire country.”

It meant temperatures would be much colder than usual for this time of year, she said.

Strong winds were expected for Wellington, Taranaki, Auckland and Northland. It might make conditions difficult for commuters in major cities, such as Auckland.

It was unlikely the rain warnings would be upgraded to red although it paid to keep an eye on the rain radar, she said.

Nelson region on alert

Intense rain caused flash flooding in the Nelson CBD a week ago and now Nelson east of Nelson city is under an orange level warning until midnight.

Nelson Tasman Civil Defence public information manager Paul Shattock said it had begun raining and was expected to continue all day, with more intense bursts in the mix.

With the amount of rain expected, the rivers could reach flood levels so a close eye would be kept on them, especially this afternoon when the high tides would occur.

“Unfortunately when that heavy rain falls in high tide the heavy rain doesn’t have anywhere to go and that’s what caused those floods that occurred last Monday.”

He was hoping for a lesser impact this week due to the tide levels and the atmospheric pressure being a lot lower.

People were being asked to avoid driving through surface flooding.

Streams and river levels could rise quickly so caution was necessary, he said.