Frosts in some parts of the country early Tuesday were an early taste of the incoming cold surge that could bring one of the coldest October nights on record to many places.
Temperatures fell to under 3C in several regions, including Canterbury, early on Tuesday, MetService meteorologist Larissa Marintchenko said.
About 7am on Tuesday, MetService was showing temperatures of 0.7C in Timaru, -0.9C in Queenstown, 1.1C in Gore, 2.5C (feels like -2C) in Christchurch, 5.2C in Wellington, 1C in Masterton, -1C (feels like -6C) in Waiouru, and 12.2C in Auckland.
While Auckland was warmer than most of the rest of the country, and slipped a little further to 11.5C by 8am, that was still around 3C cooler than the same time on Monday.
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The coldest temperatures are forecast to reach the city towards the end of the week, with a daytime high of just 13C on Thursday, and early morning lows of 6C on Friday and Saturday.
The cold snap was due to start being felt in the south from Tuesday evening, after the arrival of a front expected to reach southern Fiordland about midday, Marintchenko said.
Peter Meecham/Stuff
Snow in Springfield, inland Canterbury, in August. An unseasonal cold snap in the next few days could bring more snow to low levels in much of the South Island and lower North Island.
MetService is forecasting snow could lower to 200m in the south on Tuesday night It could fall to 200m in the north of the South Island, and to sea level from Canterbury southwards, during Wednesday.
In the North Island, snow could lower to 200m in Wellington on Wednesday evening, and to 500m in Manawatu.
MetService is warning of a chance the “intense cold outbreak” could bring heavy snow above 400m overnight, or above 600m in the deep south, to much of the east of the South Island.
Christchurch is expected to have a fine Tuesday after the frosty start, with a high of 20C. That all changes with an overnight southerly change, and on Wednesday and Thursday daytime highs of just 10C are expected, with an early Thursday low of -1C.
MetService is forecasting the temperature will drop to -3C in Alexandra early Thursday.
Southerlies are forecast to arrive in Wellington late morning Wednesday, with snow possible to 200m from evening, with the temperature dropping to 2C early Thursday – which would equal it’s second-lowest October temperature – and only getting to 8C later that day.
MetService metrologist Angus Hines described the air as “taking a direct line from the Antarctic ice sheet to the South Island”, bringing with it strong winds, snow and bitterly cold temperatures.
Those conditions could stress livestock, while frosts could damage newly planted crops. There was also the possibility of seven metre waves around coastal parts of Southland on Wednesday night.
Many South Island roads are likely to be affected and possibly closed, as well as some roads over the lower and central North Island.
NIWA/Supplied
A Niwa graphic shows a blast of cold air from Antarctica moving up Aotearoa, covering the whole country by Thursday.
Niwa forecaster Chris Brandolino predicted there could be “sleety, snow-mixed flakes” in Wellington on Thursday morning – probably in the hilly suburbs, but possibly at sea level.
MetService were predicting record-setting lows that day for some parts of the country. Masterton, for instance, is looking at a high of 7C on Thursday – the lowest October high ever so far recorded is 8.4C. Invercargill is forecast for a 6C high, the lowest high on record for the month is 5.8C.
Blenheim is forecast for a low of -2C, the equal fourth-coldest October temperature. It would only need to undershoot that projection by a half a degree to become the third-coldest October day.
Even areas that don’t get snow will notice a drop in temperature. Hamilton started the week at 18C but would drop to a high of 12C on Thursday, with a sub-zero overnight minimum.
Stuff/Stuff
Many South Island roads are likely to be affected and possibly closed.
It was previously reported that there had not been October snow in Christchurch for over 50 years – however, MetService walked back that statement, clarifying that data for two decades was incomplete.
“It’s certainly very uncommon. It is possible that it happened during those incomplete years, but it hasn’t happened much,” Hines said.
Conditions were expected to ease on Friday, giving way to a sunny weekend for most parts of the country.
“Even when the rainy and snowy weather clears, the overnight temperatures are still going to be really cold.”
