Thunderstorms can develop rapidly and cause major damage. Unlike other severe weather warnings, thunderstorm advisories follow a unique two-colour system.
MetServices’ Head of Weather News Heather Keats said "when forecasters at MetService see the potential for Thunderstorms, they will issue one of two advisories: a Yellow Severe Thunderstorm Watch or a Red Severe Thunderstorm Warning,"
"There's no orange thunderstorm warning—it just goes from yellow to red. And that's because of the nature of thunderstorms,” said Keats.
Keats said thunderstorms are a threat to people, property and livestock.
Yellow Severe Thunderstorm Watches
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Issued when atmospheric conditions are ripe for a thunderstorm to develop.
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Usually provided up to 12 hours before a potential storm forming.
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A signal that you need to be checking forecasts more frequently.
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Particularly important if you’re doing or planning outdoor activities:
- Tramping
- Boating
- Farming
- Sports events
- Outdoor work
Take action – What you need to do under a Yellow Severe Thunderstorm Watch
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Stay updated with forecasts and enable push notifications on the MetService app.
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Be prepared to take immediate action if a red warning follows.
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Consider rescheduling outdoor activities.
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Review your emergency plans.
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Clear drains and gutters.
"A thunderstorm doesn't just produce lightning. They have the potential to create a whole range of weather," Keats said. "So yes—lightning, but also intense heavy rain, a downpour—which can cause flash flooding and rapidly rise rivers and streams."
Red Severe Thunderstorm Warnings
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Issued when a severe thunderstorm has been detected on the forecasters’ radar.
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Warning time can range from minutes to approximately one hour.
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Covers specific areas in the predicted storm path.
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Potential hazards include:
- Lightning strikes
- Intense downpours causing flash flooding
- Rapidly rising rivers and streams
- Hail up to 2cm in diameter (capable of injury and damage).
- Sudden strong wind gusts that can topple trees and damage structures.
- In rare cases, they may cause tornadoes.
Act Immediately – What you need to do under a Red Severe Thunderstorm Warning
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Go inside immediately.
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Stay away from windows.
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Avoid using electrical equipment or landline phones.
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If you’re driving, if possible pull over safely, make sure you’re away from trees.
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Do not shelter under trees if you’re outside.
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If you’re boating, head back to shore if it's safe to do so.
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Stay informed through official channels like MetService, your local emergency management office and NEMA’s Civil Defence website and their social media pages.
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Be prepared for power outages.
Further information
MetService - For accurate weather forecasts and alerts
NEMA (National Emergency Management Agency) - Get Ready
Your local emergency management office - Local civil defence emergency management groups
Resources for an emergency
In the event of a civil defence emergency listen to your radio.
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A resource for getting you and your whānau prepared and ready for an emergency.
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The Agency responsible for national emergency management planning and leading or supporting the response and recovery from emergencies.
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Warnings, watches and severe weather outlook.
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A list of local and regional councils who will provide civil defence information for your area.
Emergency Guides
Metservice weather explainer: Severe weather
MetService weather explainer: thunderstorms
Mis and disinformation and how to spot it
Getting your flat emergency ready
Your community is your best resource in an emergency
Managing your medication during an emergency
MetService's Head of Weather News, Heather Keats. Photo:
"Thunderstorms affect relatively small areas over short time periods but can be incredibly destructive once they form." - Heather Keats
