Much of the upper North Island remains under a Severe Thunderstorm Watch until tonight

MetService says unstable showery conditions are spreading south onto the upper and central island, with a moderate risk of thunder.

It says some thunderstorms may become severe across eastern parts of Northland this morning and early afternoon, then Auckland around midday and through the afternoon.

Coromandel Peninsula, eastern parts of Waikato and Taupo, and Bay of Plenty could also be in the firing line.

Localised downpours and strong gusts are possible, with a slight chance of a damaging tornado.