Calculate thunderstorm distance

Calculate thunderstorm distance: Lightning and thunder

How far away is the thunderstorm? Calculate the distance from the time between lightning and thunder - with safety recommendations:

• Distance calculation: Time (seconds) × 343 m/s (speed of sound)
• Rule of thumb: Time in seconds / 3 ≈ kilometers
• Safety distance: Less than 10 km danger!
• 30-30 rule: Seek shelter if <30s, wait 30 min after last thunder
• How to behave during thunderstorms: Where is it safe?

Physical background: Light (lightning) travels at 300,000 km/s - practically instantaneous. Sound (thunder) at only 343 m/s (1,235 km/h). The thunderstorm is approx. 343 m away per second of delay.

Examples:

• 3 second delay: approx. 1 km away (danger!)
• 10 seconds: approx. 3.4 km (search for safety!)
• 30 seconds: approx. 10 km (border area)

Safety rules:

• Safe: Building with lightning conductor, closed car
• Dangerous: Open field, trees, bodies of water, metal fences
• Emergency behavior: Crouch, feet together, avoid dips
• Lightning strike: 30m stride radius! Take small steps

30-30 rule: If there is less than 30 seconds between lightning and thunder: Seek shelter immediately! Wait 30 minutes after the last thunder before going outside. Thunderstorms can return!