In a span of four hours from late morning, New Zealand experienced 1,018 lightning strikes, with most of them felt at the top of the North Island, MetService meteorologist Daniel Corbett said.

He warned of more lightning strikes as a band of severe thunderstorms moves in from the Tasman Sea. As a result, a severe thunderstorm watch would still be in place for Auckland, Northland, Great Barrier Island and the Coromandel Peninsula at least until Thursday, May 23.

Because of the bad weather forecast in many places, plus the risk of hail and frequent lighting, Mr Corbett urged New Zealanders to remain indoors.

"I wouldn't be out there with my picnic basket," The New Zealand Herald quoted Mr Corbett.

The MetService added there is a potential for a few small tornadoes, while wind gusts are expected to exceed 110 km/h and hail could be bigger than 20 mm in diameter.

Waikato, Waitomo, northern Taranaki, the Bay of Plenty and northern Gisborne were also placed on a moderate risk of thunderstorms, while Taranaki was also placed under risk of small tornadoes.