There were multiple thunderstorm warnings throughout the country, which have now been lifted, except for Canterbury, which is in effect until 9pm.
Power slowly being restored to 50,000 people
One lightning strike had tripped the power supply to Hawke's Bay, Gisborne and Wairoa, the company said: a transmission tower had been hit.
A Transpower spokesperson said workers have been working to restore power as soon as possible, although it was not possible to provide a timeframe.
"We hope you can get back to enjoying your Saturday plans once your power is back on," the company said on Facebook.
The power would be restored gradually through the affected areas.
Transpower said while the power supply was fixed, restoring it to each area safely would take time.
"We know it's never easy to be without power, and especially at such a busy time of the year leading up to Christmas," it said in a statement.
"Lightning strikes are a regular hazard for our power system in New Zealand. While our system is pretty robust, from time to time a lightning strike does take out a circuit - it's impossible to protect against this."
On Saturday afternoon, the power cut affected much of the central North Island, including all Firstlight Network customers in Gisborne and Wairoa.
Line provider Unison said the outage had affected at least 50,000 people in Napier and Hastings.
"It's quite a major outage. We are still trying to confirm how many people have been affected," a Firstlight spokesperson said.
Hawke's Bay Regional Council said they have sent a generator to the Haumoana pump station, to keep it working during the power cut.
"Our team is on the ground monitoring river and stream levels across Hawke's Bay and is ready to deploy additional generators and/or portable pumps to other pump stations if required," a council spokesperson said.
RNZ listeners have been texting in about the power outage.
"What's happening with the power? Out in Clive, Napier ... perhaps even further," one said.
"No power as far north as Gisborne," another person reported.
Others on social media helped with brainstorming how to heat milk for babies to make it safe, during the power outages.
The outage website for Unison was also reportedly down.
Severe thunderstorm warnings
MetService had warned of thunderstorms in much of the North Island and parts of the South Island, on Saturday.
Thunderstorm warnings issued by the weather forecaster for the Bay of Plenty, South Waikato, Matamata Piako, Waipa, Taupō, Otorohanga and Rotorua were lifted by early Saturday evening, while a thunderstorm watch remained in place for the Canterbury Plains and High Country until 9pm Saturday.
Heavy rain watches remained for Clutha, Tasman, and areas about Motueka, for late into Saturday night.
For full MetService warnings and updates please go to their website.
RNZ is a statutory lifeline utility in civil defence emergencies which means we have specific duties under the Civil Defence Emergency Management Act 2002.
