Thousands of lightning strikes were recorded overnight, but the weather is calmer than it was expected to be.
More than 17,000 strikes were recorded in the Tasman Sea, 3000 over the North Island and surrounding waters.
- Watch: Lightning strikes Auckland's Sky Tower
- Weather: Vicious thunderstorms, strong gusts to strike North Island, tornadoes possible
- Wild weather destroys houses in Auckland and Taranaki
NIWA forecaster Chris Brandolino told The AM Show there have been perfect conditions for unsettled weather.
"It's been a couple of pretty active days, we've had what we call low-pressure way upstairs, that has cold air.
"Whenever you put cold air over warm waters... it's like putting a cork at the bottom of a pool, the air wants to rise violently, [making] showers and storms."
The end of the week had been forecast to be very wet with possible flooding, but it was calmer than expected on Thursday.
August has been an unsettled month in New Zealand, with weather extremes causing havoc across the country.
Brandolino said September might still have some surprises in store.
"Gotta watch September, could be very active, colder than average, particularly after the first week of September.
"I think we're gonna end winter on a pretty cold note, which is 30/31st of August, so a quick, cold sharp cold snap and then things may need to warm up for a short time. Don't be fooled - September could be really active and chilly."