These thunderstorms were likely to produce localised heavy rain of 10 to 25mm per hour and there was also a slight risk of a small tornado near the coast.
A Fire and Emergency spokeswoman this morning said there were no weather-related callouts in the northern region last night.
The weather would ease for a time about the upper western North Island this morning, before a southwesterly change brought heavy showers and strong winds from mid-morning.
There was also a moderate risk of thunderstorms developing about the west coast of the North Island from the west of Auckland to North Taranaki late morning ahead of an approaching front over the Tasman Sea.
These thunderstorms were likely to produce localised heavy rain of five to 15mm per hour and small hail.
Auckland, including Great Barrier Island, Coromandel Peninsula, Waikato and Bay Of Plenty west of Te Puke were under a strong wind watch from 4pm to 1am Wednesday.
Martens said these winds could approach 100km/h.
Winds would ease by late evening, with showers persisting.
The rest of the country was not looking too bad today, Martens said.
"South of the Central Plateau winds and rain will be lighter. There will be periods of rain across the South Island, but it will gradually clear."
Tomorrow a weak ridge would spread over the country ahead of a front arriving tomorrow night, bringing heavy rain to the West Coast and light falls in the east.
The front would spread on to the North Island late Thursday followed by a showery Friday across most of the country along with some colder air.
"Not unseasonably cold, but back to average," Martens said.
The snow level would lower to about 1000m across the South Island.
Another weak ridge would form early Saturday bringing some respite in the North Island, before another front arrived in the South Island.
"Overall the weekend is not looking too good, except in the North Island on Saturday," Martens said.
"But there will be more rain in both islands on Sunday."
Today's weather
Whangārei
Showers, heavier from afternoon. Strong, gusty westerlies. 16C high, 9C overnight.
Auckland
Showers, some heavy, chance squally and thundery from midday. Westerly gales from midday, gusting 100 km/h. 15C high, 10C overnight.
Hamilton
Showers, frequent and heavier from late morning. Strong, gusty westerlies from about midday. 14C high, 8C overnight.
Tauranga
Rain turning to showers morning, chance thunderstorm throughout the day. Northeast turning gusty westerly morning. 15C high, 9C overnight.
New Plymouth Showers, heavier from late morning, chance thundery. Northeasterly easing morning, then turning strong southwest evening. 14C high, 9C overnight.
Napier Morning rain, then showers, frequent in the evening. Northeasterlies. 16C high, 7C overnight.
Wellington Periods of rain, clearing for a time this afternoon. Northeast dying out, then southerlies from late afternoon. 14C high, 9C overnight.
Nelson Occasional rain, gradually easing. Light winds, then southwesterlies developing afternoon. 14C high, 6C overnight.
Christchurch High cloud, then occasional rain from late afternoon and northerlies turning southwest. 12C high, 7C overnight.
Dunedin Mostly cloudy. Occasional rain, clearing evening. Light winds. 10C high, 5C overnight.
