Lightning Risk
Thunderstorm electrical activity
What is it?
Lightning is the electrical discharge of a thunderstorm. It kills and injures more people annually than most storm hazards, mostly people caught outdoors before or after the rain itself.
How we measure it
Forecast thunderstorm probability and CAPE-based instability from Open-Meteo weather codes; the engine flags windows with thunderstorm conditions.
Practical risk guide
- No storms forecastMinimalNo thunderstorm conditions expected
- Storms possibleWatchUnstable air — storms could develop
- Storms forecastActThunder expected — plan around it
- Thunder audibleDanger nowYou are within strike range
Within safe range
With no storms forecast, outdoor plans are unaffected — but conditions can change; recheck for long outings.
Beyond the range
If you can hear thunder, lightning can reach you — strikes commonly land 10–15 km from the rain core, in clear air. Direct strikes are rare; most injuries come from ground current and side flashes near trees or open water.
Precautions
- 'When thunder roars, go indoors' — wait 30 minutes after the last thunder.
- Avoid open fields, ridgelines, isolated trees, and water.
- A hard-topped vehicle is safe shelter; a shed or tent is not.
- Indoors: avoid plumbing and corded electronics during the storm.
- If caught in the open, crouch low on the balls of your feet — never lie flat.