Severe Weather Warnings and Watches
MetService is New Zealand’s only authorised provider of Severe Weather Warnings. We provide land-based severe weather forecasts through a system of Outlooks, Watches, and Warnings.
Types of Warnings and Watches
Severe Weather Watch
Issued for heavy rain, strong wind, or heavy snow when a weather event is likely to require a Warning but the impact area and level of severity are under assessment. A Watch may remain in place during an event if impacts are near, but not quite reaching, warning criteria. Severe Weather Watches are yellow.
Watch - stay alert.
Watches are represented by a yellow colour-code and accompanied by a circle icon. When a Watch is in place, stay alert and keep an eye on your local forecast for updates. Watches are used when severe weather conditions are likely, but not imminent or certain.
Severe Weather Warnings
Severe Weather Warnings for heavy rain, strong wind, or heavy snow are issued when weather will meet or exceed our Severe Weather Warning Criteria and are classified into one of two categories: Orange or Red.
Orange Warning - take action.
Used when the forecast indicates incoming bad weather (expected heavy rain, strong wind, or heavy snow) will meet our Severe Weather Criteria. It signifies that people need to be prepared and take action as appropriate because there may be disruption to their day and potential risk to people, animals and property. The majority of warnings issued by MetService will be orange. An Orange Warning will always be displayed as a hexagon icon.
Red Warning - take immediate action, act now!
Reserved for only the most extreme weather events, such as the severe weather resulting from ex-tropical cyclones, where significant impact and disruption is expected. It signifies that people need to act now as immediate action is required to protect people, animals, and property from the impact of the weather. People should also be prepared to follow the advice of official authorities and emergency services. Red Warning icons will always be displayed as a triangle.
Thunderstorms
Due to the rapid onset and damaging nature of Severe Thunderstorms, the warning system is adapted to the shorter time frames associated with these events.
Thunderstorm Watch - stay alert, be prepared.
Thunderstorm Watches are issued when there is a heightened risk of Severe Thunderstorms developing. People in a Watch area should be prepared for the sudden onset of strong winds, heavy rain and hail. Be on the lookout for threatening weather conditions and check regularly for Severe Thunderstorm Warnings.
Thunderstorm Warning - take immediate action, act now!
A Thunderstorm Warning is issued when an active Severe Thunderstorm* is detected by our network. Thunderstorm Warnings will only ever be signified by the colour red.
*Severe Thunderstorm criteria:
Heavy rain (from thunderstorms) bringing rainfall of 25 millimetres per hour or greater.
Hailstones 20 millimetres in diameter or greater.
Strong wind gusts (from thunderstorms) of 110 kilometres per hour (60 knots) or greater.
Damaging tornadoes: Fujita F1 or greater, where F1 is defined as having wind speeds greater than 116 kilometres per hour (63 knots)
What is the difference between Outlooks, Watches, and Warnings?
Severe Weather Outlooks
The Severe Weather Outlook is a ‘heads up’. We can see something coming, but because it is still a few days away there is uncertainty about what might happen and where.
Covers severe weather that may happen three to six days from when you see it.
Indicates areas around NZ where rain, snow, or wind may reach warning criteria.
Areas are assigned a confidence level (minimal, low, moderate, and high), reflecting the likelihood that the weather will reach warning levels.
Severe Weather Watches
A Watch is typically issued two to three days before a potential severe weather event.
Watches contain more specific details for timing, location, and intensity than an Outlook.
Usually, a Watch is issued for an event then becomes a Warning as the event draws closer. Watches provide a ‘chance of upgrade’ to show the likelihood it will become a Warning (high, moderate, low, or minimal).
Severe Weather Warnings
Severe Weather Warnings are typically issued 24 hours before a severe weather event, or when our forecasters have a high level of certainty that an event will exceed MetService severe weather criteria.
They are assigned one of two colours based on the expected severity of impacts, Orange or Red.
Orange Warnings:
Orange Warning events are significant weather events. They signal you need to take appropriate action to avoid disruption and reduce risk to people, property, and animals.
Orange Warnings contain a ‘chance of upgrade’ to show the likelihood it will be changed to a Red Warning (high, moderate, low, or minimal).
Red Warnings:
Red Warnings are used when conditions are expected to be among the worst we see in New Zealand – it will have significant impact, and it is possible that a lot of people will be affected.
During a Red Warning, act now! Immediate action is required to protect property, people, and animals from the impact of the weather.
It is important during Red Warning events that you follow the advice of official authorities and emergency services.
What is in a Severe Weather Warning?
Each Severe Weather Warning is made up of the following features:
Area - The location that is likely to be affected.
Period of validity - When the severe weather is expected to happen.
Forecast - Detailed information about the predicted weather conditions.
Chance of upgrade - The likelihood that the current Watch or Warning will change to a higher warning level as the area of impact and severity become more certain.
We use four levels to describe this chance:
Minimal: Less than 10%
Low: 10-30%
Moderate: 30-60%
High: Greater than 60%
Impact statements - An explanation of how the predicted weather could affect the area. These appear on all Warnings and will be shown on a Watch if there is a ’High’ chance of upgrade to a Warning.
Action statements - Practical steps you can take to be weather ready. This advice is informed by the National Emergency Management Agency and tailored for different types of weather and severity. Actions will only appear on a Watch if there is a ‘High’ chance of upgrade.
Time of issue - When the Watch or Warning was last issued or updated by MetService.
Next update - The expected time the forecast will be updated, usually by 10am or 10pm.