The thunderstorms are due to a very humid and unstable northwest airstream which lies over the North Island.
Locals were told to drive with caution.
Cyclone Ana has already made its impact felt in Fiji with extensive flooding of some areas and people seeking shelter.
Forecasters say it's still hard to tell just how big the impact could be.
Forecasters are also expecting an "exceptional amount" of snowfall for mid-summer.
"There's orchards out there that are going to be in that 80 to 100 percent loss of crop."
The cost of insurance payouts for weather events this year will be more than $200 million.
It's beginning to look a lot like a category 3 cyclone.
But Weather Watch says it may not make it as far south as Aotearoa.