Incredible moment forks of lightning illuminate Auckland sky

Incredible photos of lightning over the Auckland region on Wednesday night have emerged online.

There were a total of 42 lightning strikes over the Rodney District between 9pm and 11pm, MetService says.

Video shows the moment a fork of lightning moves across the sky above Mt Rangitoto in a flash of purple.

On Thursday morning another thunderstorm warning was put in place over Hawke's Bay.

MetService says some areas had up to 50mm of rain within an hour, which has likely caused some localised flooding.

The warning says it could affect people in Hastings and Napier.

MetService warns those in the area to take shelter, beware of fallen trees and power lines and avoid streams and drains "as you may be swept away in flash flooding".