Heavy rain and isolated thunderstorms are about to lash the Coromandel, while the thirsty Auckland region is also due for a dousing.

MetService has a severe weather warning in place for eastern areas of Northland, which is to come under the gun at 4pm today.

The Coromandel is in line for heavy rain and isolated thunderstorms with between 100 to 150mm of rain expected.

That will include peak rates of 20 to 40mm/h from thunderstorms, the remnants of which will produce showers into tomorrow.

"Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous," MetService wrote in its warning.

However, the weather is set to move one way and that was south, meaning a wet weekend for many parts of the country.

The rain would hopefully provide a welcome boost to Auckland's dam,s which are today sitting at 44.8 per cent, down 0.2 per cent on yesterday.

The dams normally sit around 78 per cent at this time of the year.

The Hūnua Ranges had received 57.5mm of rain the past week, while 41.5mm had fallen in the Waitākere Ranges.

In the north and east of Northland for the 11 hours from 4pm, there would be periods of heavy rain with isolated thunderstorms and possible downpours.

Northeast gales were also likely, especially in exposed places.

Meanwhile, in the Auckland region north of Orewa, including Great Barrier Island, Waiheke and the Hunua ranges, the heavy rain and possible downpours were expected to land at 8pm through till Friday morning.

Gales should also be expected.

A MetService spokesman earlier said a low-pressure system over the Tasman Sea, and its associated fronts, were forecast to move southeastwards onto the North Island over the next few days - bringing with it bad weather.

"The weather system should bring rain to much of the North Island by the weekend, but especially northern and eastern regions."

The weather will move down to the Bay of Plenty and west of Te Puke, including the Kaimai Range, tomorrow morning.

A heavy rain watch is also in place for Gisborne, north of Tolaga Bay.