MetService and Civil Defence warn Bay beachgoers after Cyclone Cody and Tonga eruption

Bay of Plenty residents are being advised to stay out of the water and off the beaches, rivers and harbours after a volcanic eruption in Tonga and Cyclone Cody bringing big swells.

While the region may have "dodged" Cyclone Cody's stormy weather conditions, MetService was predicting big waves up to 5m along the region's coastline.

The Mauao base track has also been closed due to "strong and unpredictable surges".

Today, Civil Defence New Zealand issued a national advisory of tsunami activity following a massive undersea volcano eruption in Tonga, where surging seas caused campers to evacuate and boats to be damaged after losing their moorings.

The organisation expects New Zealand coastal areas on the north and east coast of the North Island and the Chatham Islands to experience strong and unusual currents and unpredictable surges at the shore.

MetService said Cyclone Cody was also expected to bring "hazardous" sea conditions for eastern coastlines of the North Island and around Chatham Islands.

A strong wind watch has also been issued for the Bay of Plenty.

Mount Main Beach. Photo / Zoe Hunter

Bay of Plenty Civil Defence emergency management Bay of Plenty director, Clinton Naude, said the national advisory to stay out of the water, off the beaches, shore areas, rivers and harbours had been extended until further notice.

"There is still volcanic activity in Tonga and our thoughts are with everyone there.

"Keep safe and we'll update the Bay of Plenty Civil Defence channels again when we have more information."

Naude said precautions are also still in place for Cyclone Cody and he advised people to check the MetService website and Facebook page for the latest weather updates.

MetService meteorologist Ashlee Parkes said models initially tracked Cyclone Cody towards the Bay of Plenty but it was now looking like the cyclone will pass east of the country.

The cyclone was expected to impact the Bay of Plenty from later today.

"The Bay of Plenty will see little to no weather associated with the system."

Parkes said the main thing was keeping a close eye on sea and swell conditions in the region.

At 8.30am, the maximum wave height recorded in Tauranga Harbour area was 3.6m which was "not massive but it is a good wave".

The combined waves to the northeast will reach up to 5m later today, she said.

"Combined wave conditions will be hazardous...

Tay St Beach. Photo / Zoe Hunter

"There is potential for significant sea surges, rip currents, and coastal inundation.

"We are encouraging people to stay out of the waters because of the large swells with the system as it passes through."

But she said the sea conditions will deteriorate late Monday.

Parkes said tomorrow was looking to be "quite warm" with Tauranga recording a high of 31 degrees.

However, she said it will be a "bit windy" with strong southwesterlies across the country.

The Mauao base track has been closed as a precaution due to "strong and unpredictable surges", the Tauranga City Council said in a media statement.

This closure is to ensure public safety and signage and barriers will be in place at all closure points.

The closure will be reassessed tomorrow.