A rare weather event could bring another bitterly cold blast to New Zealand.
When temperatures over the South Pole climb by more than 25 C, it kicks off a "sudden stratospheric warning".
Meteorologists think it will happen next week.
NIWA forecaster Ben Noll told Simon and Phil the warming can allow cold stormy air to escape the pole.
He says there's a lot of ocean in the Southern Hemisphere - so it doesn't mean New Zealand will feel the worst of it.