WeatherWatch: Antarctic chill brings still, sunny days

Kiwifruit farmers use helicopters to keep frosts off kiwifruit. Photo / Kenny Rodger

What a classic autumn it has been.

March was stormy for the North Island with three big rains causing major slips in Gisborne and prompting rain warnings across the island.

In April, blue skies, warm days and light winds were familiar forecasts from day to day for much of the country apart from Gisborne which, again, had more rain and cold winds.

When May arrived the weather finally became truly autumnal with a fairly even mix of warm and cold, wet and dry, windy and calm.

Auckland had frosts much earlier this year than last - that doesn't equal a brutal winter ahead. This past week, the frosts returned as far north as Auckland, with a few fog patches across the country.

Gary Shaw of Featherston said: "Had a pretty bitey one. Froze a plate of water that had been left out for a foolhardy hedgehog."

Kat Roverts of Rangiora noted: "Very, very thick frost; kids thought it had snowed! Was still -2 degrees at 8.30am."

In the Bay of Plenty, frosts have come at a critical time for kiwifruit growers, where they can cause significant damage. "Helicopters were buzzing kiwifruit blocks lower down on the other side of the valley all night," David Harris told us, as a large high drifted in bringing clear, calm, nights.

The weather pattern around New Zealand is still dominated by intense highs - the bigger the highs the bigger the reach they have across the planet. A large high centred near Tasmania can help bring in polar air from the Antarctic ice caps and as the high moves it locks in that cold air, producing severe frosts. As these intense highs depart they can pull down warm subtropical air, too.

For that reason we say there is about a 35 per cent chance of a nationwide polar blast like last August, normally the risk is just 5 per cent.

In the meantime, flying saucer watchers have reported sightings of UFOs and other bright lights over New Zealand. When you Google "meteors eyewitness reports" WeatherWatch.co.nz comes up first worldwide. We have had a surge in reports of meteors over central New Zealand, too, this past week including one on Monday night, then another on Wednesday morning. I've seen two meteors in my life and they really are breathtaking and beautiful.