MetService has issued an orange rain warning for the upper North Island.

The warning covers Northland and Auckland, with other northern centres under a yellow rain warning.

For Northland the warning is in place until noon on Monday.

"Expect 90 to 120 mm of rain in the north and east, with lesser amounts in the west. However, localised areas may receive 150 to 200 mm. Peak rates of 10 to 20 mm/h, mainly in the north and east, but localised areas may see 25 to 40 mm/h especially in thunderstorms from this evening through to Monday morning."

For Auckland the warning lasts until 7am on Monday morning.

"Expect 50 to 90 mm of rain north of the City, but possibly 150 mm in localised places. Lesser amounts are likely about and south of the City but amounts may still exceed warning criteria in some places.

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"Peak rates of 10 to 20 mm/h, but localised areas may see downpours of 25 to 40 mm/h, especially in the north. Thunderstorms are also possible."

Earlier today, MetService's Auckland-based meteorologist Georgina Griffiths spoke with media about another system coming in.

"We're looking at a significant, potentially, system - a northeasterly rain and gale system coming in from the north again."

Griffiths said that Northland could be affected "quite significantly" by the system on Tuesday and that it would reach Auckland either later Tuesday or during Wednesday.

Given the vulnerability of the region at the moment, she warned that little rain would be needed to cause further slips and flooding.

"From an Auckland perspective, Wednesday details are not yet there and the timing is not yet firm," she said, "but we will update you in the coming few hours and days around that potential for some impacts on Wednesday in Auckland."

The region is currently reeling from a series of floods and slips caused by historic downpours on Friday.

Click here for the latest MetService weather warnings.

Northland Civil Defence Controller Graeme MacDonald said: "We know there have been a few weather warnings for the region recently and it’s easy to get complacent since we got off lightly last time, but Northlanders should take this one seriously and be prepared."

At least four have died as a result of the severe weather.