People in Northland, Auckland, and Bay of Plenty - should settle in for a drenching

They're also under watches for severe thunderstorms and wind - and rain watches apply for Tairawhiti, Waikato and inland Taranaki.

In the South, orange heavy rain warnings cover Nelson, Tasman, Marlborough, Westland District ranges, and the headwaters of Canterbury and Otago lakes.

MetService's Lewis Ferris says parts of Northland have already had 100 millimetres of rain in 12 hours.

Ferris says it will move eastwards, bringing potential downpours, with 25-to-30 millimetres an hour already seen.