There is a moderate risk of thunderstorms about northern Canterbury, the Kaikoura Coast, Wellington, southern Taranaki, Whanganui, Wairarapa, coastal Hawke's Bay and southern Gisborne.
During the afternoon the low risk of thunderstorms in Northland and Auckland increases to moderate north of Auckland City.
A heavy rain warning is in force for Taranaki and Whanganui to 8pm, where up to 100mm and isolated thunderstorms are forecast.
Hawke's Bay hill country east of Wairoa is also in for a wet day and night, as showers turn to rain overnight. Up to 120mm of rain may fall to 1am tomorrow.
Taihape had a heavy dumping of rain overnight, turning to snow above 700m.
Martens said wind gusts in Auckland were between 100-140km/h at the storm's peak between 8 and 10pm last night.
The strongest gust recorded was 213km/h at Manukau Heads.
"The winds have abated a bit, but are still about 80-100km/h this morning."
Martens said such strong winds were "unusual" for Auckland, which was why they were so damaging.
"If those gusts were in Wellington it would not be such a problem. But that is not a normal experience for Auckland, which was why there was so much damage to trees and houses."
About 15-35mm of rain was recorded across Auckland in the past 18 hours.
It was also the coldest morning for Auckland this year, dropping to 9C.
The rest of the North Island is down to between 3C to 8C, except Gisborne, where the cold air has not quite reached, which is sitting around 11C.
Wellington and Taupo will be among the coldest of the North Island today, as they are forecast to reach highs of just 10C.
Higher areas are frosty and snow has fallen over the Central Plateau.
State Highway 1's Desert Rd from Rangipo to Waiouru has closed in snow and ice. The NZ Transport Agency has a detour in place.
Showers would be also move onto the South Island, which is in for another cold day.
"Generally temperatures in the South Island are between 1C to 6C this morning," Martens said.
The best places appear to be Nelson on 15C and Greymouth on 14C, where fine weather forecast.
Some higher and more central areas were in the negatives overnight and more snow fell.
"There was probably not as much snow as on Monday night, but there are snow showers across the island as we speak."
Some areas around the Canterbury High Country and Kaikoura Ranges were forecast to receive over 40cm of snow.
Martens said lahtough it was unseasonably cold, it would be much colder if not for the unusually warm seas.
"If not for the warm seas, we would see snow to sea level in the South Island."
There will be no respite tomorrow though, as a new system arrives in the South Island from the west.
The fast-moving front should cross most of New Zealand tomorrow, bringing a burst of heavy rain to western areas of the South Island, and strong southwesterlies to many parts of the country.
Over Fiordland and southern parts of Southland and Clutha has the low risk of rainfall reaching warning levels tomorrow and early Friday, and a moderate risk that southwesterlies gales may become severe for a time.
"It will spread more rain across the country, with potentially heavy falls and there may be snow to 800m above sea level," Martens said.
The rain will spread onto the North Island from tomorrow afternoon, bringing strong southwesterlies.
Looking ahead to the weekend there may be some brief periods of respite, before another front arrives late Friday and into Saturday.
The southwesterlies are forecast to ease on Friday as a ridge approaches New Zealand from the west, which then crosses the country during Saturday and Sunday.
Northeasterlies spread over the country on Sunday, and rain may develop about the South Island's West Coast. Rainfall accumulations may reach warning amounts about Fiordland and Westland on Sunday.
"This system may also bring heavy rain to the North Island," Martens said.
"We are looking at a pretty unsettled period."
Today's weather
Whangarei Showers, some heavy with hail and possible afternoon thunderstorms. Brisk southwesterlies. 15C high, 9C overnight.
Auckland Showers, some heavy with hail, becoming isolated afternoon. Cold southwesterlies, strong and gusty at times. 14C high, 10C overnight.
Hamilton Showers, possibly heavy with hail, easing this morning and fine spells increasing. Cold southwesterlies. 14C high, 6C overnight.
Tauranga Showers, possible heavy with hail from afternoon. Cold winds turn southerly. 17C high, 6C overnight.
New Plymouth Showers, possibly heavy with hail, easing afternoon with increasing fine spells. Breezy cold southerlies. 13C high, 6C overnight.
Napier Morning rain then showers, possibly heavy with hail. Strong cold southwesterlies. 13C high, 7C overnight.
Wellingtonβ Showers, some heavy with hail, and possible thunderstorms. Strong or gale cold southerlies. 10C high, 7C overnight.
Nelsonβ Fine. Cold southwesterlies gradually easing. 15C high, 3C overnight.
Christchurchβ Showers, some heavy, chance thunder and hail. Strong cold southwesterly, easing evening. 11C high, 1C overnight.
Dunedinβ Showers clearing and strong cold southerly easing evening. 11C high, 5C overnight.
