Damaging winds, lightning, rainfall and even tornadoes could hit the North Island tonight and MetService has put several areas around the Auckland and Marlborough regions under a severe thunderstorm warning.
Meanwhile the South Island is dealing with heavy rain, flooding and snow-related issues.
They came as a front in the Tasman Sea moved across central New Zealand through the night bringing a band of rain and embedded thunderstorms.
MetService said a severe thunderstorm watch remained in force for Taranaki, Kapiti-Horowhenua and Marlborough after the forecaster detected severe thunderstorms near Wellington and Porirua at 8.30pm.
The thunderstorms would be accompanied by a short period of heavy rain, small hail, strong northwest wind gusts, and possibly a small tornado, MetService severe weather forecaster John Crouch said.
"Wind gusts of this strength can cause some structural damage, including to trees and power lines, and may make driving hazardous."
The thunderstorms were moving towards the southeast, and are expected to lie near Lake Ferry, Palliser Bay, Pirinoa and the Southern Rimutaka Range at 09.07pm.
Auckland Emergency Management said it had been notified by MetService the region could be in for a night of damaging localised winds, lightning and rainfall.
The gale force winds had forced the LUX Light Festival in Wellington to be cancelled for the night.
The festival was marked to run from May 18 to May 27.
Thunderstorms and hail were noted in Wellington just before 10pm.
Meanwhile an active cold front is moving northeast over the South Island and lower North Island today bringing heavy rain causing flooding as well as strong winds.
The Milford Rd had been closed and a car was stuck on the Crown Range Road due to heavy snow this afternoon.
The road is likely to reopen by 10am tomorrow, but ''significant snow'' is forecast down to low level on Thursday (40cm-60cm expected in the Homer Tunnel area), which could mean an all-day closure.
Snow is also forecast for Saturday.
The chilly blast is also forecast to bring snow down to 400m in the south of the South Island, and many alpine roads were subject to road snow warnings through to tonight including Arthur's Pass (SH73), Lindis Pass (SH8), Crown Range road, and Dunedin's Northern Motorway (SH1).
The NZ Transport Agency has issued two flooding warnings for inland Otago. Road users are asked to take care and drive to the conditions.
Southern District police said there was reported flooding in various locations on State Highway 6 between Cromwell and Makarora this afternoon.
The heaviest rain is expected in Fiordland, Westland south of Otira, and the headwaters of the Otago and Canterbury Lakes and Rivers, with 100mm-150mm expected in places.
A very unstable west to southwest flow is expected to cover northern and central New Zealand tomorrow, bringing more heavy showers, thunderstorms and hail.