Heavy rain across the upper North Island overnight is expected to continue this morning.

MetService said Auckland and Waikato saw the heaviest rainfall overnight, with rural Waiuku recording around 30mm of rain.

The area between Hamilton and Pukekohe recorded about 27mm overnight, while Coromandel Peninsula received about 10mm in the past hour.

A low-risk thunderstorm was forecast for the west of the North Island from Taranaki to Cape Reinga, MetService said.

Wellington and the east coast are set to stay dry.

Moderate thunderstorms have been forecast across the South Island, expected to bring up to 25mm to Fiordland and Stewart Island and then North Otago and South Canterbury later in the day.