If you’ve ever seen a “Severe Thunderstorm Warning” pop up on your phone and wondered how serious is this, really?—you’re not alone. The key is knowing what each warning type covers, what triggers it, and why your suburb might be inside a big shaded warning area even if you barely get a drop of rain.
Here’s how to read BOM storm warnings like a local who’s been burned (and hailed-on) before.
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Is it a robot or a human issuing the warning?
Both—kind of.
The warning system automates the “structure” (things like mapped areas, locations, and timestamps). But every warning is edited and reviewed by a real BOM meteorologist before it goes public. In other words: software helps assemble it fast, but a human signs off on what it means.
Broadcasters like ABC then help relay the warning and translate technical language into plain-English updates—especially during emergency coverage.
The main warning types you’ll see (and what they’re for)
1) Severe Weather Warnings
These cover hazardous weather that isn’t specifically a thunderstorm warning, cyclone warning, fire weather warning, etc. They can include:
- Damaging winds: gusts over 90 km/h or average winds over 63 km/h
- Heavy rainfall: rainfall exceeding the 10% Annual Exceedance Probability (AEP) threshold (roughly a “1 in 10” chance for that intensity over that period)
- Blizzards: issued for parts of New South Wales and Victoria above 1200 m
2) Severe Thunderstorm Warnings
These are specifically for dangerous thunderstorms (storms with lightning). Lightning isn’t just dramatic— it can ignite bushfires, take down trees, and knock out power and telecommunications.
3) Coastal Hazard Warnings
Used for abnormally high tides or storm tides, and threats like coastal erosion, large waves, and inundation.
4) Everyday and sector-specific advice
These include things like Marine Wind Warnings, Frost Warnings, and agricultural alerts (for example Sheep Graziers’ Warnings), plus a Bushwalkers’ Alert (Tasmania only).
5) Other major warnings
Heatwaves, Tropical Cyclones, Fire Weather, Floods, Tsunamis, Damaging & Dangerous Surf, High Seas, and Geomagnetic Storms also sit in the broader warning ecosystem.
What triggers a Severe Thunderstorm Warning?
The BOM issues a Severe Thunderstorm Warning when forecasters detect or expect thunderstorms with any of the following:
- Large hail: 2 cm diameter or larger
- Damaging wind gusts: 90 km/h or greater
- Heavy rainfall: rainfall exceeding the 10% AEP threshold
- Tornado
If you’re seeing this warning, it’s not “maybe a bit of rain.” It’s “this storm can damage property and put people at risk.”
Why does the warning sometimes say “DANGEROUS”?
“Dangerous” (or “high-end”) is used when the storm is expected to produce the upper tier of impacts:
- Destructive wind gusts: over 125 km/h
- Giant hail: over 5 cm diameter
- Intense rainfall: exceeding the 2% AEP threshold (roughly a “1 in 50” intensity)
- Tornado: violently rotating column of air over land
There are also rainfall call-outs used in New South Wales:
- >70 mm in up to 1 hour, or
- >150 mm in up to 3 hours
…can be considered intense.
Bottom line: “Dangerous” is the BOM telling you the storm is capable of extreme damage—not just messy weather.
Where does the BOM get its storm information?
Warnings aren’t based on one radar scan and a hunch. BOM forecasts and warnings draw on data from a network of more than 11,000 pieces of equipment, across land, sea, air and even space—such as radars, automatic weather stations, flood gauges, upper-atmosphere monitors, and ocean wave buoys.
Why is the warning area so big if only a small spot gets smashed?
Because thunderstorms don’t behave like tidy blobs on a map.
The BOM can identify when conditions are favourable for severe storms, but pinpointing the exact street a storm cell will track over ahead of time isn’t realistic, because:
- Storms form fast and shift quickly, driven by temperature and moisture changes, sea breezes, and terrain effects|
- Storm cells can be tiny (hundreds of metres across), while many forecast models work at kilometre-scale grids
- The most severe impacts often happen directly under the core, so a path shift of 200 metres can mean the difference between wild hail and nothing much at all
When storms approach populated areas, the BOM may issue Detailed Severe Thunderstorm Warnings that track individual storm cells, showing red dots for cells and arrows for movement direction—basically “this specific storm is heading this way.”
What you should do when a storm warning is issued
Because the storm core can miss you by a suburb—or hit you dead-on—your best move is to act when the warning covers your area, not when you see the first raindrop.
Practical steps that actually reduce damage:
- Move cars under cover if you can (hail doesn’t negotiate)
- Secure loose outdoor items (chairs, umbrellas, trampolines)
- Unplug sensitive electronics if lightning is close
- Stay off roads if visibility drops or flash flooding begins
In the end, BOM storm warnings aren’t “weather hype” — they’re a structured heads-up about specific hazards and clear thresholds, reviewed by a real meteorologist before they go public.
The catch is that thunderstorms are messy and fast-moving, so a big warning zone doesn’t mean everyone gets hit — it means conditions are right and the impact can swing by a few streets.
If your area is included, treat it as your cue to act early: bring cars under cover, secure loose items, and stay alert for updates as individual storm cells are tracked in real time.
