A blast of cold air threatens to bring one of the coldest October nights on record, plunging the country back into sub-zero mid-winter temperatures.
The surge of cold air will move across the country on Wednesday and Thursday, most likely bringing snow to sea level in main centres of the South Island.
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.
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The cold front was expected to arrive in Southland about midday on Tuesday and arrive in the North Island late on Tuesday into Wednesday.
“With the cold comes the risk of snow as well, especially for Southland and Otago. However, snow showers could well be seen as far north as the lower North Island during Thursday,” MetService said.
A heavy snow watch is in force for the south and east of the South Island above 400 metres, with the possibility of snow in Invercargill, Gore, Oamaru and Christchurch on Wednesday afternoon or Thursday morning.
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 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.
Wellington was forecast for a low of 2C, which would be its equal second-lowest October low. A strong wind chill would make the temperature “feel sub-zero”, Brandolino said.
NIWA/Supplied
A Niwa graphic shows a blast of cold air from Antarctica moving up Aotearoa, covering the whole country by Thursday.
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.
Auckland would fare better than most on Thursday, with a high of 13C and an overnight low of 5C.
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 on Wednesday afternoon, 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.”
