Up to six centimetres of rain an hour and severe thunderstorms that are forecast to begin mid-afternoon have prompted warnings of flash flooding and slips across the top of the North Island.

MetService has issued a 19-hour orange heavy-rain warning for Northland as a subtropical low and preceding fronts move slowly southwards across the top of the country. It will come into place at 3pm and lapse at 10am tomorrow.

“Expect up to 90 to 120mm of rain, mostly in the north and east,” MetService said.

“25 to 60mm an hour possible in localised thunderstorms and downpours overnight.

“Streams and rivers may rise rapidly. Surface flooding, slips and difficult driving conditions possible,” the forecaster said.

“Clear your drains and gutters to prepare for heavy rain. Avoid low-lying areas and drive cautiously.”

A severe thunderstorm watch coincides with the rain warning for Northland.

MetService said: “A band of heavy rain with embedded thunderstorms is expected to move southwards over Northland overnight”.

An orange heavy rain warning will also come into effect for the Coromandel Peninsula from 6am to 9pm Tuesday, with downpours expected in the morning and early afternoon with possible thunderstorms, MetService said.

MetService has also issued heavy rain watches for Auckland, Great Barrier Island and Gisborne north of Tologa Bay. These are in force from 4am until 9am Wednesday.

Auckland, Great Barrier Island and the Coromandel Peninsula will also be under a strong wind watch tonight, coming into effect from 1am and lasting to midday.

‘Take extra care’ - Northland Civil Defence

Northland’s Civil Defence group has warned people to “keep an eye on the weather and take extra care” ahead of the forecast 19 hours of torrential rain.

“We will continue to monitor this weather system as it passes through,” the group said.

Meanwhile today, Auckland had a mostly cloudy forecast with scattered rain predicted to ease to isolated showers. The daily high was tipped to reach 25C before falling to 22C tomorrow.

The rest of the country south of the Central Plateau was expected to miss the downpours and thunder.

The National Institute of Water and Atmospheric Research (Niwa) said the South Island’s weather would remain settled early this week before a front brought showers from Thursday.

Raphael Franks is an Auckland-based reporter who covers breaking news. He joined the Herald as a Te Rito cadet in 2022.