Police are advising motorists to take extra care as a subtropical storm batters the country

MetService has issued Heavy Rain Warnings for Northland, the Coromandel Peninsula, western Bay of Plenty and northern Tasman.

Severe weather watches are also hanging over the wider upper, central and western North island, the Nelson Ranges and Westland.

Northland police are urging people to drive to the conditions, delay unnecessary travel, be patient and allow extra time on the roads.

Boaties are also warned to stay off the water -- forecaster Aidan Pyselman says there's some decent swells.

He says there's big northeasterly swells right from North Cape, down to Gisborne and into the Wairarapa.