Woman crushed by fallen tree critically hurt

A woman has sustained critical injuries after being crushed by a fallen tree in Cambridge as wild weather sweeps up the North Island.

Locals and residents on Victoria, Queen, Hall, Wilson and Dick Streets reported seeing small tornados in the area.

Some say trees have fallen on cars and homes.

The woman has critical injuries and had to be freed from under the fallen tree by firefighters in Victoria Square.

The large tree toppled over on to a picnic table.

Northern Fire and Emergency shift manager Jordan Barnett said a fire appliance and two support vehicles also responded. The person was "removed from the tree" at about 10.50am.

Police received reports of the incident at 10.04am.

Meanwhile, Auckland Harbour Bridge has reopened after strong wind fears briefly forced all lanes to close as wild weather descended on the city.

Waka Kotahi warned Aucklanders to delay travel or use State Highway 16 via West Auckland, with winds tipped to hit more than 95kmh.

The Harbour Bridge was temporarily closed as a precaution, with some lanes reopening at 10.19am. All lanes were opened again at 10.26m.

The wild weather is ramping up across Auckland as heavy showers, thunderstorms and blustery winds start to batter the region.

It follows a tornado in Levin early today that carved a trail of destruction, damaging buildings, uprooting trees and closing streets.