Central Otago growers crank up frost fighting efforts to preserve millions of dollars worth of fruit

Frost-fighting efforts are cranking up in central Otago to preserve the buds of millions of dollars worth of fruit.

Incredible pictures show wind machines and helicopters being used to protect the precious crop.

Forecasters say the central Otago region plummeted to -5C on Tuesday morning.

Tim Jones, chief executive of 45 South Orchard and Packhouse in Cromwell, says the cold is expected to stick around for another month.

"NIWA has got some news out there that this could be a challenging spring," he told Newshub. 

A sudden stratospheric warming (SSW) was anticipated by NIWA. This means the air above Antarctica warms more than 25C above normal, and the usual westerly winds in the stratosphere - 30 to 50km above the ground - reverse direction, disrupting the stable status quo.

The vortex of "stormy and freezing weather" surrounding Antarctica then weakens, letting cold air from the south rush north. The last time this happened - in 2002 - New Zealand suffered temperatures that were, on average, between 2C and 3C colder than normal.

Jones told Newshub he remembers that challenging spring well.

"The last one in 2002 I do recall had an awful lot of frosts right throughout the spring," he said. "Particularly leading on into October and November.

"Who knows whether we're up for that again this year, but the key thing is that we're prepared for it."