Heavy rain, damaging winds, severe thunderstorms and a chance of small tornadoes are on the way after a warm couple of days.
A thunderstorm warning has been issued for nearly all of the North Island and the upper South Island, MetService says.
MetService tweeted that there was a risk of severe thunderstorms with downpours for the central west.
The thunderstorms look likely to hit this afternoon through to the evening from the upper North Island down to the top of the South Island.
A chance of small tornadoes was also possible, the MetService thunderstorm outlook map showed.
Heavy rain for the evening commute in Wellington. Chart shows model rain calibrated to appear the same as the MetService rain radar, and winds. Heavy rain expected through Wellington around 5-6pm, then cooler southerlies with possible thunder. https://t.co/tr7q4POIHO ^TA pic.twitter.com/7Pbx65UAyh— MetService (@MetService) May 16, 2018
A severe weather watch warning has been issued for Waitomo, Taranaki, Wellington, Marlborough and Nelson.
The past couple of days were relatively warm with Auckland recording its third warmest May temperature in nine years.
After yesterday's warmth, more today.— NIWA Weather (@NiwaWeather) May 14, 2018
A big reason for the warmth is the position of the low relative to NZ.
Watch how the movement of the low influences temperature. Compare temperatures with the low to our west (NW wind) versus the low to our east (SW wind).
Tomorrow a weak trough crosses the North Island, while a front moves on to the lower South Island.
This front then moves slowly up the South Island on Friday and the North Island on Saturday, followed by another front over the South Island on Sunday.
Fog delays flights
Fog in Christchurch and Dunedin this morning has led to flights being cancelled and delayed.
Air New Zealand said there have been some delays, but no cancellations to its jet services, but three of its turboprop services in and out of Christchurch have been cancelled.
In Dunedin some flights were also delayed and cancelled.
Both airports were encouraging passengers to contact their airlines for updates.
The fog was expected to clear in both Dunedin and Christchurch.