Tropical Cyclone Tam - which has brought wind and rain across the upper North Island has now been classified a subtropical low

The widespread system's prompted warnings of heavy rain and strong winds in periods - progressively from Northland, to Auckland, Coromandel, Bay of Plenty, Gisborne - and Tasman, until midnight Friday.

Travellers are warned to take care, with danger from trees and power lines - and coastguard's urging people to stay off the water.

MetService Meteorologist Mmathapelo Makgabutlane says Northland could get wind blowing up to 140 kilometres an hour.

She says for the region, that is very strong - especially from that direction.