Weather information
Before you go out, always check and understand the marine weather forecast
Marine forecasts state what the weather is expected to do over the water.
Weather on the water is very different than on land, and you need a marine weather forecast. Marine forecasts include things like tidal information and sea states.
How to get forecasts when you’re out on the water
Given weather conditions can change quickly, it is important you regularly check the marine weather forecast when you are out on the water.
Maritime radio
The Maritime NZ maritime radio service provides forecasts at scheduled times. These are announced on VHF Channel 16 and you need to go to a working channel for your region at:
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0133, 0533, 0733, 1333, 1733, and 2133 (New Zealand local time).
For the Chatham Islands, forecasts are broadcast on channels 60 and 62 at:
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0603, 1403, 1803, and 2200 (Chatham Islands local time).
Coastguard on VHF radio
Forecasts are also available on your local Coastguard channel, including NowCasting continuous broadcasts on channels 20, 21, 22, and 23 in many coastal areas.
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Coastal forecast: Are forecasts for coastal areas around New Zealand. These focus on large-scale wind and swell systems.
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Recreational forecast: Forecasts for smaller areas where there is a lot of recreational boating activity. They focus on conditions that are relevant to small vessels.
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Boating forecast: Focus on local conditions at specific spots, often where fishing vessels will go. They give a score and what specific conditions are likely.
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Activity based forecasts: Forecasts that give information for local areas which are specific to surfing, paddleboarding and kayaking.
Marine forecasts are usually accurate for major weather events, such as gales. They can be less accurate in predicting local changes in conditions, so always be prepared for the unexpected.
Seek local knowledge from people who live in the area. Harbourmasters are an excellent source of local information along with sports clubs (for example yacht clubs).
A yacht in rough seas
Look ahead
If you are planning ahead or expect to be away for more than a day, get a long‑range marine weather forecast. The outlook will tell you what weather is predicted up to 5 days ahead.
Having information in advance gives you time to change your plans or wait for better boating conditions.
Prepare for the unexpected
Remember that the weather can change suddenly and without warning. While you are out:
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keep an eye on the sky and sea state
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listen to Maritime Radio and NowCasting in your area so you get warnings of increasing winds
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head for shelter at the first sign of worsening weather.
When the wind rises, the water can become rough very quickly, especially on lakes and rivers.
Forecasts are the best prediction available at the time. They are not a guarantee of actual conditions.
If in doubt, do not go out
It is important to respect the weather at sea.
Many accidents involving small vessels are weather‑related. Bad weather makes the environment on board extremely hazardous. It also puts strain on the vessel’s structure, equipment, and the people on board.
Skippers should:
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understand the different parts of a weather forecast
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know the best ways to find up‑to‑date local information.
Our boating expert says if the conditions at sea are not suitable, it's not worth the risk
A marine weather forecast may be broken down into the sections below.
Wind
Wind direction, such as north‑west, is the direction the wind is expected to come from.
Wind speed is given in knots. One knot is about 2 km/hour. The forecast gives an average speed, so expect gusts to be up to 50% higher. Wind can also funnel between headlands, which can roughly double the wind speed in those areas. Specific areas of New Zealand also have local wind conditions. For example, katabatic winds that are common in areas where there are mountains or steep hills.
Sea
“Sea” describes the waves created by the local wind.
Swell
A swell comes from either a distant disturbance, such as a cyclone or depression, or develops from wind waves that have been blowing from the same direction for some time. Swells increase in height and get steeper as they reach shallow water.
Swell heights are usually described as:
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low – under 2.0 metres
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moderate – 2 to 4 metres
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heavy – over 4 metres.
Wave height
Wave height refers to the size of significant waves generated by the wind in the area.
Approximate wind‑wave height descriptions are:
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calm – up to 0.1 metre
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smooth – up to 0.5 metre
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slight – up to 1.0 metre
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moderate – up to 2.0 metres
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rough – up to 3.0 metres
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very rough – up to 4.5 metres
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high – up to 6.5 metres
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very high – up to 8.5 metres
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phenomenal – 11.0 metres or more.
Visibility
The average visibility in New Zealand is about 15 nautical miles.
Forecasts usually include visibility when it is expected to be less than 6 nautical miles (about 10 km).
Visibility may be described as:
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fog – less than 1 nautical mile
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poor – 1 to 3 nautical miles
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fair – 3 to 6 nautical miles
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good – over 6 nautical miles.
Outlook
Marine forecasts generally cover up to 48 hours, with an outlook for a further 3 days.
Situation
The “situation” is a description of the position and movement of highs, lows, and frontal systems expected to affect the New Zealand coast within the next 36 hours. It also names areas affected by warnings.
Warnings
Warnings are issued for gales, storms, or squalls anywhere on the New Zealand coast. In recreational marine areas, a strong wind advisory is issued if the wind is expected to be over 25 knots (about 40 km/h).
If strong winds are associated with a cyclone from the tropics, this will be mentioned in the warning, but separate tropical cyclone warnings are not issued in New Zealand.
Warnings are as follow:
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strong wind– steady wind expected to constantly exceed 25 knots, or gusts of 33 knots
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gale – steady wind of 33 to 46 knots, with gusts up to 50% higher
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storm – steady wind of 47 knots or more, with gusts up to 50% higher.
Wind and tide
Remember to check the tides as the combination of wind and tide affects sea conditions:
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when the wind opposes the tide, seas will be much rougher
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when the wind flows with the tide, seas will be calmer.