When does winter officially start in New Zealand?

Monday, 27 May 2019

June 1 marks the official start of winter, according to meteorologists.

But it's not the only start date for the cold season.

'There are actually four different starts to winter, but the two that we usually talk about are the astronomical start date and the meteorological start date,' according to Phillip Duncan, head forecaster from Weather Watch.

The other two dates are derived by mother nature and tracked by the solar winter.

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There's an official date meteorologists follow, but that's not the only start date for the cold season.

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While the beginning of June marks the start date for meteorologists, those following the astronomical seasons won't welcome winter until June 22 - known as winter solstice, the shortest day of the year.

'A lot of people believe that's the proper start,' Niwa principal scientist forecaster Chris Brandolino told Stuff.

But the start of June was selected because it is easy to record.

'Using the first of the month, it's easy and convenient for book keeping,' Brandolino said.

He explained, the start date makes it easier to record data relating to average rainfall, temperatures and snowfall.

While the beginning of June marks the start date for meteorologists, those following the astronomical seasons won't welcome winter until June 22 - known as winter solstice, the shortest day of the year.

In contrast, the astronomical date is based on the Earth's position in relation to the sun. Brandolino described it as a time 'when the sun crosses an imaginary line on the equator'.

However, based on a national poll, the majority of Kiwis tend to rely on neither date - instead looking at mother nature as their guide.

A poll by Weather Watch found that around 40 per cent of respondents believe winter ends when mother nature says so, while just under 30 per cent rely on the astronomical date, around 24 per cent rely on the meteorological date, and only 5 per cent follow the solar dates.

Duncan noted the popularity of using mother nature as an indicator of the change in seasons is 'sort of the Kiwi way', but based on their regular polls, 'there doesn't seem to be one that is favoured'.

'In New Zealand, mother nature is probably the best guide and right now, people would argue this doesn't feel like winter,' he told Stuff.

Recently, much of New Zealand has enjoyed mild weather. However, recent forecasts predict a cold, wet start to the traditional winter season.

Niwa previously told Stuff many places around the country are on track for one of the driest autumns on record, and can expect a significant downpour before the end of the month.

The forecast for the week ahead aligned perfectly with the meteorological start date, with southerlies bringing a cool front across the country.

'It just worked out perfectly on the first of June we have that southerly… it's looking cool over the weekend,' MetService meteorologist April Clark said.

Unlike our across the ditch neighbours and those in the northern hemisphere, Duncan argued that New Zealand doesn't exactly have even and cyclical seasons.

'If anything, we have a two-month summer, a two-month winter, and eight months of spring and autumn.'

Clark, mirrored these sentiments by explaining the change in seasons isn't like flicking a switch.

'It's not like you go from warm to cool to coldest,' Clark told Stuff.

Though she noted June 1 as the official date observed by MetService, she explained the major indicator that winter has arrived is the length of each day.

'That change going into winter is really all about just the days getting shorter.'

Whichever cycle you follow, Brandolino and Duncan believe they each have their own issues.

For those who follow the meteorological dates, issue arises when the new season 'officially' starts, but the weather is yet to change.

'Obviously, you can get winter-like weather outside of winter,' Brandolino said.

Duncan explained the issue with the solar winter - which adds six weeks either side of the shortest day of the season - is when the weather changes but you're still in what you consider the season of winter.

'It means that in the middle of September you have to say it's still winter and that is so hard to do when the days are getting much longer, and it's warm… people are wearing t-shirts, rams are getting bigger.'

However, despite the various dates people use to indicate the start of the cold season, Duncan believes there are three main months that typically align with winter.

'June, July and August best represent the months of winter.'