Wet Christmas Day for Northland, Auckland, Bay of Plenty, Waikato, fresh heavy rain warnings issued

Fresh heavy rain warnings have been issued tonight as large swathes of the country prepare for a sodden but humid Christmas Day.

Usually a haven of sunshine and warm weather, the Bay of Plenty, Auckland and the Waikato are all in for less-than-stellar weather tomorrow as MetService predicts high chances of an indoor Christmas dinner.

The clouds rolling in over New Zealand today will keep many parts of the country drenched on Christmas Day, though muggy conditions are also likely to linger.

MetService meteorologist Clare O’Connor is advising people in the upper North Island they’d “best rely on an indoor option”.

An unsettled and humid northwest flow is expected to cover northern and central New Zealand.

In the North Island, rain is likely in the north and west, with fine spells and isolated showers elsewhere.

In the South Island, rain with heavy falls is likely in the west and south but easing, and a few showers elsewhere.

Thunderstorms are possible in both islands, with moderate confidence that rainfall amounts will reach warning criteria over many areas from Fiordland to East Cape.

Thunderstorms could produce localised downpours over northern North Island regions, mainly in the afternoon and evening.

Mainly fine weather is expected for Christchurch and Marlborough.

Severe thunderstorm watch for Auckland

Scattered heavy showers and/or thunderstorms are expected about the greater Auckland region between about 1pm and 8pm today and may produce localised downpours of 25-40mm/h or more.

Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips. Driving conditions will also be hazardous, with heavy rain leading to surface flooding and poor visibility.

MetService also said there was a further risk of thunderstorms and downpours over Auckland again on Christmas Day.

Heavy rain warning for Wellington

The Wellington Region Emergency Management Office said from 12pm today to 9am tomorrow, about 120mm of rain is expected in Tararua, Kāpiti-Horowhenua, Wairarapa and Wellington.

“Waterways could rise rapidly and surface flooding and slips are possible. Driving conditions may be hazardous.”

These thunderstorms will be accompanied by heavy rain and have the potential to produce localised downpours in excess of 25mm/h.

Severe thunderstorm watch for parts of Hawke’s Bay

Central and southern Hawke’s Bay and the Tararua district are at the highest risk of downpours this afternoon and evening.

A severe thunderstorm watch is in force for these areas, where rainfall rates of 25-40mm/h, or potentially more, can be expected to come with the thunderstorms.

MetService warned of possible surface and flash flooding, especially in low-lying areas such as streams, rivers or narrow valleys, and the weather may also lead to slips.

Although the thunderstorms should ease this evening, further thunderstorms are likely on Christmas Day.

O’Connor said the eastern areas of both islands are looking to be the driest and warmest locations tomorrow.

“Napier and Hastings are forecast to reach 31C; Blenheim, Christchurch and Ashburton could all reach 29C,” she said.

Heavy rain warning for Taranaki

A heavy rain warning is in place for Mt Taranaki from 8pm this evening to 9am tomorrow.

“Expect a further 50 to 80mm of rain near the summit on top of what has already accumulated, with lesser amounts at lower levels of the mountain.

“Peak intensities of 15 to 25mm/h early Monday morning with possible thunderstorms.”

Heavy rain warning for the West Coast

A heavy rain warning is in place for Westland ranges south of Otira from this evening to 8am tomorrow.

A MetService spokesperson said to expect a further 60 to 80mm of rain on top of what has already accumulated.

“Peak intensities of 15 to 20mm/h this evening with possible thunderstorms.

“Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.”

Chance of a Christmas barbecue in parts of the South Island

O’Connor said that “for those eastern South Island areas though, the northerly winds will drop out in the afternoon and turn [into] light southerlies, which will drop the temperatures slightly – this will lead to cooler overnight temperatures (around 12C), which may be a welcome respite”.

She brings good news for those in the west of the South Island, where the rain looks to ease during the afternoon.

“The chance of a Christmas barbecue is still on the cards there,” she said.

Southland and Otago should also expect a few showers, and Dunedin looks to be wettest in the evening.

Rain or showers throughout the day are forecast for Northland, Auckland, Waikato, the Bay of Plenty and Taranaki.

“Best to rely on the indoor option in those areas,” O’Connor said.

For Wellington and Manawatū-Whanganui, it will be raining in the morning, especially about the ranges, but most of that rain should clear in the afternoon.