Moisture
Warm, humid air is the fuel. As it rises and cools, its water vapour turns into cloud and gives off heat, which pushes the air even higher.
Hooray for storms
Bring on
the boom!
We absolutely love a good thunderstorm. The flashes, the rumbles, the smell of rain on hot pavements. Here's everything that makes them amazing.
Tap the sky to make lightning!
Since you arrived, lightning has flashed about 0 times around the world!
The science
Three ingredients. One spectacular sky.
Every thunderstorm follows the same recipe. Mix these together on a warm day and stand well back.
Instability
When rising air stays warmer than the air around it, up it goes like a hot-air balloon. The bigger the difference, the wilder the storm.
Lift
Something gives the air its first nudge. Sun-baked ground, a cold front, a sea breeze or a hill will all do the trick.
The life of a storm
A single storm cell usually lives for less than an hour. It packs a lot into that time.
Stage 1
Growing
Powerful updrafts build a towering cloud that bubbles upwards like a cauliflower. Not much rain yet, but it's growing fast.
Stage 2
Showtime!
The cloud hits the ceiling of the lower atmosphere and spreads into a giant anvil. Heavy rain, hail, lightning and gusts all arrive together.
Stage 3
Fading away
Cold downdrafts cut off the supply of warm air. The rain eases, the anvil drifts off, and the sky often clears to a gorgeous sunset.
Lightning
A giant spark, hotter than the Sun
Inside the cloud, ice crystals and soft hail crash into each other and swap electric charge. The top of the cloud turns positive and the bottom turns negative. When the difference gets too big, zap! A spark leaps across.
30,000°C
The air in a lightning bolt can reach around five times the temperature of the Sun's surface.
44/sec
Roughly how many lightning flashes happen worldwide every single second, according to NASA satellites.
343m/s
The speed of sound. Light arrives almost instantly, so counting to the thunder tells you how far away the storm is.
10miles
Lightning can strike this far from its storm, out of a clear-looking 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 air heated so fast it expands with a bang. You can hear it up to about 10 miles away.
Storms over Britain
Hooray, a Spanish plume!
Most British thunderstorms pop up in summer, when the afternoon sun heats the ground. The really spectacular ones often arrive with a Spanish plume. Hot air drifts up from Iberia, cooler Atlantic air pushes in underneath, and the night sky can light up for hours. Winter has its own treats too: thunder on wild western coasts, and every now and then, thundersnow!
Flash to bang
How far away is that storm?
Forget counting elephants. Tap the button when you see the flash, then tap again when the thunder rolls in. Or drag the slider if you counted in your head.
12.0
seconds
4.1
kilometres
2.6
miles
Have fun, stay safe
The 30 / 30 rule
Storms are best enjoyed from somewhere safe. Two numbers are all you need.
30seconds
If the thunder comes less than 30 seconds after the flash, the storm is close enough to hit you. Head indoors and enjoy the show from the window.
30minutes
Wait 30 minutes after the last rumble before heading back out. The tail end of a storm can still strike.
Do
- Watch from a solid building, or a hard-topped car with the windows shut.
- Head down from hills and ridges if you're caught outdoors.
- Get out of the water and off beaches, lakes and boats.
- Check the Met Office warnings before a hike, a round of golf or a fishing trip.
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 things.
- Use a corded phone or have a bath or shower during the storm.
- Assume you're safe just because it isn't raining yet.
Right now
Chase storms from your sofa
Thousands of volunteer detectors around the world spot lightning strikes the moment they happen. Pop the kettle on and watch them light up the map.