Moisture
Warm, humid air near the ground is the fuel. As it rises and cools, its water vapour condenses and releases heat, which drives the air higher still.
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Feel the
charge.
The science, power and beauty of thunderstorms over Britain and beyond.
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The science
Three ingredients. One explosive sky.
Every thunderstorm needs the same recipe. Take one away and the storm never gets going.
Instability
When rising air stays warmer than its surroundings, it keeps climbing like a hot-air balloon. The bigger that difference, the more violent the updraft.
Lift
Something has to give the air its first push. Sun-baked ground, a cold front, sea breezes or hills all do the job.
The life of a storm
A single storm cell usually lives for less than an hour, passing through three stages.
Stage 1
Developing
Strong updrafts build a towering cumulus cloud. There is little rain yet, but the cloud is growing fast.
Stage 2
Mature
The cloud hits the top of the lower atmosphere and spreads into an anvil. Heavy rain, hail, lightning and gusty winds all peak now.
Stage 3
Dissipating
Cold downdrafts choke off the warm air supply. Rain eases, the anvil drifts away, and the storm quietly falls apart.
Lightning
A giant spark between sky and ground
Inside the cloud, ice crystals and soft hail collide in the updraft and swap electric charge. The top of the cloud turns positive and the base turns negative. When the difference gets big enough, the air breaks down and a spark jumps across.
30,000°C
The air in a lightning channel can reach around five times the temperature of the Sun's surface.
44/sec
Roughly how many lightning flashes happen worldwide every second, according to NASA satellite data.
343m/s
The speed of sound. Light reaches you almost instantly, so the gap before thunder tells you the distance.
10miles
Lightning can strike this far from the storm, out of what looks like clear sky. It's called a "bolt from the blue".
2–3cm
The rough width of the white-hot channel itself. The glow you see is far wider than the bolt.
Boom
Thunder is the sound of air heated so fast it expands explosively. You rarely hear it beyond about 10 miles away.
Storms over Britain
When the Spanish plume arrives
Most British thunderstorms happen in summer, when the afternoon sun heats the ground. The most dramatic ones often come with a Spanish plume. Hot air drifts up from Iberia, a cooler Atlantic system pushes in underneath, and the sky can erupt into storms that light up the whole night. Winter brings its own surprises too: thunder on exposed western coasts, and occasionally thundersnow.
Flash to bang
How far away is that storm?
Tap the button the moment you see lightning, then tap again when you hear the thunder. Or drag the slider if you counted in your head.
12.0
seconds
4.1
kilometres
2.6
miles
Stay safe
The 30 / 30 rule
30seconds
If the thunder comes less than 30 seconds after the flash, the storm is close enough to hit you. Get indoors.
30minutes
Wait 30 minutes after the last rumble before heading back out. The trailing edge of a storm can still strike.
Do
- Shelter in a solid building or a hard-topped car with the windows closed.
- Head down from hills and ridges if you're caught outdoors.
- Get out of the water and off beaches, lakes and boats.
- Check Met Office warnings before hikes, golf or fishing on stormy days.
Don't
- Shelter under a lone tree. It's one of the most dangerous places to be.
- Hold golf clubs, fishing rods, umbrellas or other long metal objects.
- Use corded phones or take a bath or shower during the storm.
- Assume you're safe because it isn't raining yet.
Right now
Watch the storms live
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