A state of civil emergency has been declared in Thames-Coromandel as the district braces for the full force of Cyclone Cook.

The declaration follows one in the Bay of Plenty, with Cook expected to hit the east coast of the North Island on Thursday afternoon or evening.

Thames-Coromandel mayor Sandra Goudie says there is concern for people in low coastal areas and who may need to evacuate.

With the Easter break coming up, she advises visitors to stay away from the Coromandel Peninsula until as least Saturday.

"If people do decide to make the journey, they must be prepared to be turned back, isolated and have their journeys severely disrupted," she says.

"We are just seeing the fringes of the weather event, and we still have two more days to go."

MetService is also urging holiday makers to reconsider travel plans for the weekend.

Meteorologist Lisa Murray says disruptions and damage are inevitable, and people need to be prepared for power cuts and road closures.

Although fast-moving, Cyclone Cook will be destructive and the ground is already saturated after last week's storm, she says.

A severe weather warning is in place for many parts of the country.

As well as heavy rain, flood-hit Bay of Plenty is forecast to be buffeted by severe gales, with gusts of 150 km/h, from late Thursday afternoon.

Auckland is expected to be drenched by up to 160mm of rain in a 33-hour period until 6pm on Thursday.

The NZ Transport Agency is calling on drivers to slow down and keep lights on with rain expected to lash the city's major highways and close roads.

Travellers on the city's southern train line are being told to expect cancellations and delays due to flooding in Manurewa.

Ferry services between Gulf Harbour and Auckland have been suspended and are being replaced by buses for the rest of the day.