Auckland has broken a new record today for the most rain days in a single month - 29 days in August to be exact.

And it doesn't stop there - tomorrow is also likely to bring patches of light showers meaning the new record will likely reach 30 rain days by the time the month is over.

MetService confirmed the miserable milestone to the Herald this morning.

MetService meteorologist Philippa Murdoch said the light showers spraying the city this morning meant the record for the most rain days in a single month was officially broken.

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"As far as our records go, 29 days of rain in one month is a new record," Murdoch said.

It also means Auckland has now had two record months in a row after there was also 28 days of rain in July - a feat of Mother Nature that broke an earlier record dating back 10 years.

That previous rainiest month had been in August 2010 with 27 rain days.

Why is spring so volatile, and is it going to get stormy? Spring weather in New Zealand is characterised by high pressure to the north and disturbed westerly winds over the country, including regular blasts of polar air from the south. This can be exacerbated by a negative SAM index, which is a way of describing how far north these polar blasts can reach. Negative SAM means more stormy conditions with polar air reaching further north. We are moving into spring, with a negative SAM, and signs are good that SAM will stay negative or even become more negative. This means that spring will be changeable, like always, but also that next week and the following few weeks could be more changeable than normal. In the GIF you can see that the ring of jet streams that surround the pole become very disjointed, and regular surges of cold (blue) air make their way towards New Zealand. Our meteorologists monitor the SAM index and many other atmospheric indicators, and any time there is the potential for severe weather this will be communicated as early as possible through our forecasts, watches and warnings. This weekend is looking great, with no severe weather, but a subtropical low next week will bring warm but wet conditions to northern New Zealand. This is followed by another round of southerlies. For more information on the SAM index, head to https://blog.metservice.com/Southern-Annular-Mode ^TA

Posted by MetService New Zealand on Wednesday, 28 August 2019

Niwa figures showed, up until Sunday, Auckland had received 182mm of rain for the month – that's 165 per cent of normal – while the mean daily temperature had been running at a slightly-above-average 12.1C.

Auckland's rainy month had eclipsed that of other centres, such as Wellington (90mm so far), Christchurch (37mm), Hamilton (124mm) and Tauranga (124mm).

Luckily, it's not all miserable as spring weather is due to kick in just in time for Father's Day on Sunday, with fine spells spread across the country.

Murdoch said most of the country was in luck for some warmer weather this weekend particularly on the east coast of the North Island and upper South Island.

"Temperatures are expected to mid teens for most of the country and high teens for much of the east coast," Murdoch said.

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Antarctic door ajar

Niwa meteorologist Ben Noll said as the Southern Hemisphere sudden stratospheric warming continues next week, a highly amplified pattern will develop near New Zealand.

"The Antarctic door was still set to be ajar during mid-September," Noll said in a tweet this morning.

What will be driving our spring weather patterns❓ 1️⃣ El Niño has ended in the tropical Pacific, fading to...

Posted by NIWA Weather on Thursday, 29 August 2019

A sudden stratospheric warming (SSW) event kicks off when the temperature of the stratosphere – that's 30km to 50km above ground – over the South Pole climbs by more than 25C. Meteorologists expected it was likely to happen next week.

For New Zealand, it's extremely rare. There have been only two in New Zealand in recorded times, or since the late 1950s - one in September 2002 and the other in September 2010.

TODAY'S FORECAST

Auckland:

High 16C, low 9C. Cloudy periods and isolated showers, then some evening rain. Northwesterly breezes changing southwest at night.

Whangārei: High 18C, low 10C. Fine, then evening cloud. Northwesterly breezes.

Hamilton: High 15C, low 4C. Cloudy periods and chance shower, then rain from late afternoon, clearing at night. Northwesterly breezes.

Tauranga: High 17C, low 7C. Fine, then rain from late afternoon. Southwesterly breezes.

Napier: High 18C, low 4C. Fine, then cloud increasing afternoon and few spots of rain possible. Light winds.

New Plymouth: High 15C, low 5C. Cloudy periods, and a few showers clearing in the evening. Winds turning southwesterly.

Wellington: High 13C, low 6C. Fine. Light winds.

Nelson: High 15C, low 4C. Fine. Southwesterlies tending northerly for a time afternoon.

Christchurch: High 14C, low 1C. Fine. Light winds.

Dunedin: High 13C, 7C. Partly cloudy. Southwesterlies.

Invercargill: High 10C, 6C. A few showers. Brisk westerlies.