Auckland is in line to be hit by thunderstorms on Monday afternoon.
The storm system is currently north of the city where it has unleashed intense rain and hail on Whangārei and is moving southward.
It is expected to hit during school commutes and the rush hour.
NIWA said Northland had 300 lightning strikes between 1 and 2pm on Monday.
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The New Zealand Transport Agency reminded drivers to slow down, keep lights on, increase following distances and allow extra time in the poor weather.
MetService meteorologist April Clark said thunderstorms are usually small weather features that move through quite quickly and should ease off within the hour.
However, the potential for more thunderstorms developing would continue into the evening, she said.
More persistent heavy rain was also expected to continue into Monday evening.
Aucklanders should prepare for small hail, lightning and surface flooding in brief heavy rain.
"It should ease as we head into tomorrow. But a very wet day for Auckland," Clark said.
