A large storm is about to blast the South Island and lower North Island, bringing with it the potential for a tornado in the South Island.
Several weather warnings have been issued by MetService, including a heavy rain warning for much of the West Coast, and a warning that gales up to 130kmh could pound the Wairarapa, Wellington, Marlborough and Canterbury.
WeatherWatch forecaster Philip Duncan said thunderstorms were also likely on the West Coast of the South Island today, and on the west coast of the North Island overnight and into tomorrow.
"This is a significant storm and while the centre of the low won't actually come near New Zealand it is large enough to push gales, heavy rain and potentially damaging squalls up the South Island and lower North Island today.''
The sudden storm could also whip up a tornado in western areas of the South Island, as well as produce damaging winds, hail storms, and thunder, Mr Duncan said.
The predicted wind speeds were high enough to uproot trees, break branches, lift roofing iron and making driving extremely difficult. The rain could also be heavy enough to spillover into the east coast waterways, causing rivers in places like Canterbury to rise without warning, Mr Duncan said.
"Certainly West Coast centres will see some rough weather today and those winds will howl through central New Zealand as the day wears on.''
The bad weather would build over the South Island throughout Sunday and develop over the lower North Island into the afternoon.
Windy and showery weather is predicted for many areas on Monday which should ease on Tuesday.