Some coastal roads in Coromandel have been flooded as high sea levels and rain affect the peninsula, while flooding is expected in Bay of Plenty.
MetService is warning waterways will rise quickly in some areas, with heavy rain expected to spread over most North Island regions on Saturday and Sunday.
It says the heaviest rain is expected to be about Northland, Coromandel, Bay of Plenty, the central North Island high country and the ranges of Gisborne and Hawke's Bay.
It says 200 to 400mm of rain could accumulate in these areas from overnight Saturday until midnight Sunday, with 100 to 200mm in other areas.
Bay of Plenty Regional Council spokesperson, Bronwyn Campbell, says the Rangitaiki, Whakatane and Waimana rivers are being closely watched.
She says none of them are expected to burst their banks. But the council does advise farmers to move stock to higher ground by nightfall and is warning people not to travel in really bad weather if they can avoid the trip.
Waikato Civil Defence duty officer Greg Ryan says people need to watch out for the rising Waihou and Piako rivers on the Hauraki Plains, as well as rivers leading into Lake Taupo.
Campers in parts of Waikato and Taupo have been told to find higher ground, as rain and gale force winds start to hit the region.
Around the Coromandel coastline, water is washing over some roads because of high sea levels resulting from the strong north to northeast onshore winds and high tide.
In Gisborne, the district council says it's concerned about the impact from the predicted heavy rainfalls particularly as it's been very dry around the Gisborne-East Coast region for some time.
Emergency manager Richard Steele says the 150-250mm forecast for the region will fill up the catchment much more quickly and he fells it has the potential to cause localised flooding issues.
Mr Steele is urging drivers on State Highway 35, commonly known as the East Coast highway, and through the Waioeka Gorge, to take extra care especially during Saturday night/ Sunday morning when the heaviest rains are expected