Snow was expected to 600m overnight in parts of the South Island.
At 5.30am there were no reports of snow, but road warnings were in place for the Desert Road (SH1) in the central North Island, and Lewis Pass (SH7), Arthur's Pass (SH73) and Porters Pass (SH73) in the South Island, to 10am.
The severe weather was all on an "easing trend" today, Martens said.
Showers, possible hail and thunderstorms would ease through the morning in Auckland, becoming isolated by the afternoon with a high of 14C.
It was a similar pattern across the North Island, with a few lingering showers and thunderstorms clearing through the morning for a fine afternoon.
The South Island was also on an improving trend, with Canterbury to Nelson in for a fine day, and showers in Southland and Otago clearing by the afternoon.
The next system would arrive in the South Island tonight, bringing another shot of cold air.
It would move on to the North Island Thursday, before a ridge builds into Friday, providing a brief settled period of weather.
Another system was forecast to arrive in the South Island Friday evening, leading to an "unsettled" weekend, Martens said.
Today's weather
Whangārei
Showers, some possibly heavy with hail. Showers gradually clearing from afternoon. Westerlies dying out evening. 15C high, 7C overnight.
Auckland
Showers, some heavy, possible hail and morning thunder, then becoming isolated from afternoon. Westerlies. 14C high, 9C overnight.
Hamilton
Showers, some heavy with possible thunderstorms and hail, easing afternoon and becoming fine. Westerlies easing afternoon. 13C high, 3C overnight.
Tauranga
A morning shower or two then increasing fine breaks. Westerlies dying out evening. 14C high, 4C overnight.
New Plymouth Showers, some heavy with possible thunderstorm and hail, easing from afternoon with increasing fine breaks. Strong morning southwest change. 13C high, 5C overnight.
Napier Mainly fine, but chance shower late morning and afternoon as northwesterlies turn southwest. 13C high, 0C overnight.
Wellington Early showers with a brief southerly change, possibly heavy with hail. Becoming fine from mid-morning. 10C high, 5C overnight.
Nelson Chance shower before dawn, then becoming fine in the morning. Southwesterlies. 13C high, 1C overnight.
Christchurch A few showers retreating to Banks Peninsula early morning, then becoming fine by afternoon. Southwesterly. 12C high, -1C overnight.
Dunedin Showers clearing to fine in the morning. Southwesterlies. 10C high, 4C overnight.
