Heavy rain and thunderstorms hit the Coromandel Peninsula overnight.
Forecasters recorded 500 lightning strikes near the Peninsula between midnight and 4.30am.
A slow-moving front was bringing rainfall to bringing rain northern parts of the country with more heavy falls expected in the Coromandel Peninsula and Tai Rāwhiti/Gisborne.
An orange heavy rain warning was issued for the Peninsula along with a severe thunderstorm watch to 3pm, and an orange heavy rain warning for Tai Rāwhiti from Tokomaru Bay northwards until evening.
MetService said 60mm of rain could fall in addition to the overnight rain, and local downpours of up to 40mm were possible, with a moderate risk of thunderstorms which could also produce hail.
"In Waihi we saw about 43 millimetres fall within one hour" - Mmathapelo Makgabutlane
"As we know with these thunderstorms they do have the potential of bringing a very heavy, intense burst of rain in quite a short time." MetService meteorologist Mmathapelo Makgabutlane said.
"Yesterday out in Waihi we saw about 43 millimetres fall within one hour, which is a lot of rain to fall in such a short time."
Rainfall of this intensity could cause surface flooding and flash flooding, especially around low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips, MetService said.
Heavy rain watches were lifted for north of Napier, and Gisborne south of Tokomaru Bay. Strong wind watches were lifted for Plenty east of Whakatāne, with southeast gales easing, and were lifted for the central North Island areas and Taranaki.
Temperatures In the South Island plummeted overnight, with Pukaki dropping to -5.2°C. Morning frosts would give way later in the day to mainly fine weather with a few areas of fog or low cloud, and shows along coastal Marlborough and North Canterbury.
The low pressure system moves off to the north east on Tuesday, though showers continue for the rest of the week on the east coast of the North Island - Tai Rāwhiti/Gisborne, Hawkes Bay and the Wairarapa, with sunnier weather on the west.
"There will be a wintery feel right across the North Island ... Auckland gets down to single digits overnight early this week," MetService meteorologist Andrew James said.
The South Island is due to have settled weather, except for showers on coastal Marlborough and North Canterbury later in the week.
More cold temperatures are on the cards there with Alexandra set to get as low as -5C on Wednesday and Thursday.