"The thunderstorms are moving on to the Auckland area as we speak, it's already looking dark on the webcam around the airport."
The Gisborne region had a stormy night, with MetService reporting "thunderous activity" and 63 lightning strikes from 7.30pm.
Nearby, Tolaga Bay was lashed with periods of torrential rain - 50mm fell in three hours.
In the South Island, State Highway 6 between Korere and Glenhope remains closed due to slips.
For the rest of the country today, Hayes said there was a frosty start for Alexandra this morning, with 0C for the Central Otago town.
"It's pretty much fining up for the South Island - and just a few showers around Wairarapa, Wellington, some parts of the North Island but those are all clearing today as well.
"The Gisborne and the Bay of Plenty areas will have continuing showers today."
Today's weather
Whangārei Showers, some heavy with hail and possible thunderstorms. Becoming fine early evening. Southwesterlies. High of 18C, low 9C.
Auckland Showers, some heavy with hail and possible thunderstorms. 17C, 11C.
Hamilton Showers, some heavy and possibly thundery with hail. Becoming fine from afternoon. Southwesterlies. 18C, 7C.
Tauranga Partly cloudy. A few showers in the afternoon, possibly heavy with hail, clearing evening. Southwesterlies. 19C, 10C.
New Plymouth Fine spells. Chance morning showers. Southwesterlies gradually easing. 17C, 10C.
Napier Showers, some possibly heavy from afternoon, clearing by evening. Southerlies gradually easing. 17C, 8C.
Whanganui Partly cloudy with a shower or two, becoming fine in the afternoon. Southerly breezes turning westerly. 17C, 10C.
Wellington A morning shower or two, then fine. Southerlies easing and turning northerly in the afternoon. 15C, 11C.
Nelson Mainly fine, although a chance afternoon shower. Light winds and afternoon sea breezes. 16C, 8C.
Christchurch Becoming fine this morning. Northeasterlies developing in the afternoon. 17C, 6C.
Dunedin Fine, then evening high cloud. Northeasterlies developing by afternoon. 17C, 10C.