Thunderstorms and heavy rain could cause flooding and slips from Auckland down to Taupō from this afternoon.
A torrential downpour caused homes to be evacuated in Piha at the weekend.
MetService has issued a severe thunderstorm watch for Auckland, Waikato, Coromandel Peninsula, Rotorua and the Bay of Plenty.
"Warm and moist conditions at the surface and sea level convergence are likely to trigger frequent showers," the agency said.
"Some of these may be slow moving and thundery."
It said thunderstorms could bring between 10 and 25mm of rain an hour, and there could be localised downpours of up to 40mm of rain in some areas.
Up to 22mm of hail could also fall.
The amount of rain could cause slips, flooding and rapidly rising rivers and streams, MetService said.
Thunderstorms underway in the upper North Island. 33 strikes so far. Thunderstorm Watch is current so keep up to date with the latest https://t.co/BZWb7ZPiRd and https://t.co/GZIq9Jlbrw ^Cam pic.twitter.com/piVzvvdd0g— MetService (@MetService) February 5, 2018