As eastern-facing parts of the country gear up for a stellar day thunderstorms and heavy downpours are rumbling up the South Island's west coast.

The best of the North Island weather will be in Napier, cracking 27C today and tomorrow, while Gisborne is forecast to reach 26C today and 28C tomorrow.

In the South Island, Christchurch is the place to be, with 27C and warm northwesterlies forecast today.

The rest of the North Island is also in for a mostly fine day, with Tauranga reaching 25C and Auckland 24C, with just a bit of cloud and light westerly winds forecast.

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But in Westland and Fiordland it is another story, MetService meteorologist Stephen Glassey says.

Thunderstorms are rattling those regions right now, and heavy downpours that began yesterday afternoon will continue through the morning. Severe rain and thunderstorm warnings are in place.

The heaviest rain down near the coast has been in Milford Sound with 90.6mm, and Hokitika with 54mm, recorded since yesterday afternoon.

There have been heavier falls in the ranges with 122mm recorded at Mt Browning Station.

The rain band is moving over Southland and into Otago this morning, but will weaken as it moves north to Canterbury later this morning.

"Once it reaches Canterbury the main areas of rain will be in the high country," Glassey said.

As the front moves over the North Island this afternoon it will have further weakened.

"Northern areas south of Waitomo can expect a few showers today, but everywhere else is pretty much dry and warm," Glassey said.

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Tomorrow there will be a westerly flow over the country, continuing much of the same weather, with a few showers in the west and warm and dry conditions in the east.

On Thursday a ridge of high pressure will build over the North Island, bringing more fine weather, before another front arrives in the South Island on Friday.

"Temperatures have cooled slightly overall with the arrival of autumn, but there have been no big southerlies yet to really change things," Glassey said.

And with no big southerly systems in the near future either the mild autumn continues for a while longer.

Tropical Cyclone Josie, which devastated Fiji with major flooding from late Saturday into Sunday, is forecast to be downgraded to an ex-tropical cyclone today.

The Category 1 cyclone brought heavy rain and strong winds to parts of Fiji, causing flooding which killed four people. One person is still missing.

Glassey said the cyclone was forecast to track further southeast today.

"But it will be well away from New Zealand."

Tropical Cyclone Iris has been renamed in the Coral Sea, north of Australia.

It was a tropical cyclone about a week ago before it weakened, and then reintensified.

"That is also not expected to come here, but it could affect Australia," Glassey said.


Today's weather
• Whangarei

Mostly sunny. Light winds. 23C high, 14C overnight.

• Auckland

Cloudy at times. Westerly breezes. 24C high, 17C overnight.

• Hamilton

Cloudy at times. Westerly breezes. 24C high, 14C overnight.

• Tauranga

Fine. Light winds. 25C high, 15C overnight.

• New Plymouth

Often cloudy, morning drizzle, late evening showers. Northwesterlies. 22C high, 16C overnight.

• Napier

Fine with high cloud. Northwesterlies. 27C high, 15C overnight.

• Wellington

Cloudy with showers in north. Becoming fine by late afternoon as strong northerlies ease. 21C high, 15C overnight.

• Nelson

High cloud, brief rain at times, then becoming fine this afternoon. Northerlies turn southwest. 23C high, 12C overnight.

• Christchurch

Fine with high cloud at times. Gusty and warm northwesterlies turn cooler southerly around midday. 27C high, 9C overnight.

• Dunedin

A period of rain around dawn otherwise fine, Southwesterlies to northwest later this afternoon. 20C high, 13C overnight.