The thunderstorms were working their way up the coast, beginning in Fiordland at 1am.
Newshub reports at one point lightning bolts were flashing 45 times per minute.
The West Coast is also being battered with heavy rainfall, with up to 160mm over a 36-hour period in Westland and 120mm in the Canterbury and Otago headwaters, according to MetService.
MetService has issued a severe wind warning for Otago and Canterbury as well as Wellington and the Wairarapa.
It said storms would continue to barrage the entire West Coast for the rest of the day.