A heavy rain warning has been issued for Northland with up to 100mm possible tomorrow.
The MetService is warning that the heavy rain could make the region's roads dangerous and is urging people to take care.
MetService Meteorologist April Clark said while today seems fine, a deepening low over the Tasman Sea is moving slowly southeastwards, bringing rain and strong or gale easterly winds to the upper North Island during tomorrow and Thursday.
"That front will bring down some quite moist, of sub-tropical air,'' she said.
Clark said this will bring a lot of rain for the upper North Island, particularly in Northland and Auckland from about 9am tomorrow.
The biggest rainfall accumulations are expected over Northland, mainly about the eastern hills, and a Heavy Rain Warning is now in force, with localised downpours of 10mm-20mm an hour and up to 100mm for the day. And the rain will extend into Thursday and beyond, but will probably not be as heavy as tomorrow.
Clark said the downpours will likely leave the region's roads treacherous and people should take care on the roads. The front will also bring gale force winds to Northland, but the easterly winds are a likely to have greater impact on Auckland - which has a wind watch in place.
She said despite heavy rain forecast, it's unlikely to end Northland's drought.
''Though with some prolonged heavy rain, it will certainly help the situation up there,'' she said.
Another aspect of the front is that it will bring some big swells of up to two metres along Northland's east coast today, growing to three metre swells later in the week.
Clark said people should stay up to date with the latest forecasts and warnings as things can change rapidly.