What Causes Thunder and Lightning?

How Lightning Forms

Inside a cumulonimbus cloud, updrafts and downdrafts cause ice crystals and water droplets to collide violently. These collisions separate electrical charges — positive charges rise to the top of the cloud, negative charges accumulate at the bottom.

When the charge difference becomes strong enough, the air between them (or between the cloud and the ground) breaks down, creating a conductive channel. A massive electrical discharge — lightning — bridges the gap in milliseconds.

Why We Hear Thunder

Lightning superheats the air around it to 30,000°C — five times hotter than the surface of the sun. This extreme heating causes the air to expand explosively, creating a shockwave. That shockwave is thunder.

Why Thunder Rumbles

If lightning were a single point, you would hear one sharp crack. But a lightning bolt is a long, jagged channel. Sound from the nearest part reaches you first, followed by sound from further sections, creating the rolling rumble.

Lightning Facts

• A single bolt carries up to 1 billion volts
• Lightning strikes Earth about 100 times per second
• The average bolt is 3-5 km long but can extend over 100 km
• Lightning can strike the same place repeatedly — the Empire State Building is hit about 25 times per year

The 30-30 Rule for Safety

• If the time between seeing lightning and hearing thunder is less than 30 seconds, seek shelter
• Stay inside for at least 30 minutes after the last thunder

---

Track storm forecasts on Weather Tomorrow.