Weather: 100km/h gusts forecast for lower South Island, large swells forecast

The watch has a moderate (30-60%) chance of being upgraded to a warning.

Winds will begin to be felt this evening and peak around midnight before easing tomorrow morning, Marshall said.

The same low-pressure system bringing the wind will also create large offshore swells in exposed eastern waters.

Some swells could be as high as 9m, but will be away from beaches and coastal towns and will not have an in-shore impact, Marshall said.

🌊 Marine Forecast Heads Up 🌊

Combined wave heights in eastern offshore waters could reach or exceed the height of the Ohakune Carrot🥕

Hazardous conditions mainly for offshore vessels operating in exposed eastern waters.

Forecasts will be updated at midday, so keep an eye on… pic.twitter.com/Ln3Jnk69bZ

— MetService NZ (@MetService) June 6, 2026

The Chatham Islands may receive large swells on Tuesday.

A heavy swell warning has been issued for Cape Terawhiti to Turakirae Head in Wellington from 6am on Tuesday until the same time on Wednesday.

Waves could be as high as 7-8m around noon on Tuesday before easing that evening.

The same swell warning has been issued for Turakirae Head to Mataikona in Wairarapa with 9-10m waves forecast for late Tuesday morning, then easing on Wednesday morning.

The Wairarapa warning lasts from midnight until noon on Wednesday.

Elsewhere in the country, Northland and Auckland are forecast to have cloudy periods with some showers tomorrow, while Waikato to Kāpiti Coast is mainly fine, before cloudy periods and isolated showers.

El Nino

The warnings and watches come as Earth Sciences New Zealand monitors signs of a developing El Nino.

The climate phenomenon would mean surface water in the eastern Pacific is hotter than usual and shifts tropical rainfall to central and eastern areas of the ocean.

🌊 Forecasters are watching the Niño 3.4 region of the tropical Pacific closely.

This key El Niño monitoring region is already warmer than average, and will likely continue to warm further in the coming months, suggesting the possibility of a strong El Niño. 👀 pic.twitter.com/vmwRi6Ns8j

— NIWA Weather (@NiwaWeather) June 6, 2026

“This could bring increased rainfall to Southland, parts of Otago, and western-facing areas, primarily of the South Island, but reduced rainfall for much of the remainder of the country,” Earth Sciences New Zealand and MetService meteorologist Jon Tunster said.