Flash. Count. Boom.
Lightning and thunder happen at the same moment, but the light gets to you first. Count the gap and you can tell how far away the storm is. Try it below, indoors.
The flash-to-bang counter
Real storm: tap the yellow button when you see a flash, then again when you hear the thunder. Or try a practice storm.
How it works
- Thunder is always heard after the lightning is seen, because light travels much faster than sound. [source]
- Count the seconds from the flash to the start of the thunder. Divide by three for a rough distance in kilometres, or by five for miles. [source]
- The Met Office gives the speed of light as 299,792,458 m/s and the speed of sound as 340.29 m/s. [source]
Our working: at 340.29 m/s, sound takes about 2.9 seconds to travel 1 km and about 4.7 seconds to travel a mile. That’s where the “divide by 3” and “divide by 5” come from. The speed of sound changes with the temperature of the air, so treat the answer as a rough guide.
Stay safe
- If you can hear thunder, you are already within range of where the next ground flash may occur. [source]
- When thunder roars, go indoors, and stay there until 30 minutes after the last clap of thunder. [source]
So count from indoors, never go outside to do it.
Is there a storm with your name?
The 2026/27 list of UK, Irish and Dutch storm names, announced on 1 September 2026.
About storm names
- The UK storm-naming scheme began in 2015, and a new list of names comes out each September. [source]
- Storm names are chosen jointly by the Met Office, Met Éireann (Ireland) and KNMI (the Netherlands). [source]
- In the UK, a storm is named when it could cause disruption or damage that might lead to an amber or red warning. [source]
- The 2026/27 list of 21 names runs from 1 September 2026 to 31 August 2027. The letters Q, U, X, Y and Z are left out, in line with the US National Hurricane Center. [source]
To see which names have been used so far this season, check the Met Office UK Storm Centre.
What is storms.im?
storms.im is a small hub for wild weather, made for curious kids, families and anyone who runs to the window when it thunders. Each kind of storm gets its own site with sourced facts, games and printables. The first, lightning.storms.im, is open now. Some true things to start with:
Thunder is hot air, really
A lightning channel heats the air for a moment to around 50,000 °F, much hotter than the surface of the Sun. The air explodes outwards, and that is thunder. [source]
Tornadoes aren’t just American
A tornado is a narrow, violently rotating column of air that reaches from a thunderstorm to the ground. [source] Tornadoes happen in many parts of the world, including Europe, not just the USA. [source]
When is it a hurricane?
A tropical cyclone is called a hurricane when its maximum sustained winds reach 74 mph. [source]
The biggest storm we know of next door
Jupiter’s Great Red Spot is a giant storm that is bigger than Earth. [source]
Open now
Lightning is open, on its own site: lightning.storms.im, with how lightning works, thunder and flash-to-bang, safety tips, myths, four games and printables.
Coming soon
Here’s what is brewing next.
- Named storms
named.storms.imPlanned: how UK and Irish storms get their names, the Beaufort scale and a storm-name finder.
Coming soon - Hurricanes
hurricanes.storms.imPlanned: how hurricanes form, the Saffir-Simpson categories and the hurricane season.
Coming soon - Tornadoes
tornadoes.storms.imPlanned: what a tornado is, where they happen (Europe too) and how they are measured.
Coming soon - Isle of Man storms
manx.storms.imPlanned: storms and sea weather around the Isle of Man, told from the island.
Coming soon - Storms in space
space.storms.imPlanned: storms on other planets, like Jupiter’s Great Red Spot. A crossover with planets.im.
Coming soon
Sister hubs
storms.im is part of the same ReallyByte family as these hubs:
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