Heavy rain has started lashing Northland and a wind warning is in place.

"It's only really just beginning," says MetService meteorologist Lewis Ferris.

Kerikeri airport has reported 19.6mm of rain in the four hours to 2pm, he said, and 90km/h gusts have been recorded in exposed parts of Northland.

"The rain warning for Northland begun at 1pm and the wind watch kicks off at 3pm," Lewis said.

The upper North Island is in for a stormy few days as driving rain, thunderstorms and gale force wind hammer the regions.

Heavy rain watches and warnings are in force from Coromandel Peninsula to Auckland north, and parts of Northland can expect to be drenched with up to 100mm of rain in intense downpours.

A heavy rain warning has been issued for Northland starting Wednesday morning with localised downpours possible evening. This could cause surface flooding & hazardous driving conditions so be prepared & keep updated at https://t.co/hnwmGxU1gR and https://t.co/JgRL98vtxw ^AC pic.twitter.com/K7kYzhh6IR

— MetService (@MetService) July 13, 2020

Along with the rain, the thunderstorm risk is increasing over Northland throughout the day, with the potential for localised deluges.

Damaging winds were expected to hit Auckland and Northland this evening and northeasterly gales will pound the regions until dawn. MetService had issued a severe wind watch from 6pm until 9am tomorrow. Winds are expected to reach up to 90km/h.

With the school holidays ending, motorists are being warned to take care in potentially hazardous conditions. Flooding and slips are possible. People are also being warned to watch for rivers and streams rising rapidly.

Further to the east, Coromandel and Great Barrier Island are in for a dousing. A heavy rain watch is in place overnight, when up to 90mm of rain is expected.

The wild weather was expected to track east tomorrow and Friday, potentially bringing warning-level amounts of rain about western Bay of Plenty, Gisborne and the ranges of Hawke's Bay.