Weather warnings and watches are in place around the country, with heavy rain forecast throughout Friday.
Auckland, Northland and Great Barrier Island have been placed under severe thunderstorm watches, as rain from a complex trough moves over the top of the country.
MetService says these areas could see rainfall peak at 40 mm/h.
The Coromandel Peninsula, Taupō, and the Bay of Plenty are also affected.
Rivers are forecast to rise in Bay of Plenty, Rotorua and Tasman northwest of Motueka.
Slips and localised surface flooding can also be expected, MetService says.
In the South Island, Tasman District Council has been monitoring the heavy rain forecast for parts of the region.
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