The country is about to be buffeted by strong winds and heavy rainfall thanks to two simultaneous weather events.
A combination of a fairly typical front in the far South and the Category One Cyclone Fehi hitting New Zealand at the same time will bring an abrupt end to the warm weather.
The front, while not unusual in itself, will enhance the intensity of the tropical cyclone, which formed near New Caledonia on Monday.
MetService meteorologist Tui McInnes says the storm will be a "tomorrow event", with heavy rain starting on Wednesday night and subsiding by late Thursday evening.
Warmer than average water temperatures have contributed to the storm's intensity.
Temperatures across the South Island will cool dramatically after the week's heatwave, with Alexandra and Queenstown predicted to experience a drop of as much as 20degC.
The West Coast will see the most rainfall as well as high winds thanks to its exposed position.
Mr McInnes says Fiordland is expected to see some "fairly significant rainfall", and areas south of Otira could see between 250mm and 400mm of rain.
The strongest winds will be felt in Nelson, Marlborough, the Canterbury plains and, predictably, Wellington.
Mr McInnes advises those in affected areas to stay safe and obey all instructions from officials and Civil Defence.
"Common sense really prevails in times like these."
Civil Defence recommends people visit their advice website before the storm hits so they are prepared in case of power cuts or flooding.