From Balloons to Lightning
You rubbed a balloon and created a small spark of static electricity. But nature creates static electricity too, on a MASSIVE scale. That is lightning!
Inside a thundercloud, tiny ice crystals and water droplets are swirling around, bumping into each other. Just like rubbing a balloon on wool, all that bumping moves electrons from one place to another.
The top of the cloud becomes positively charged, and the bottom becomes negatively charged. The ground below becomes positively charged too. When the difference in charges gets big enough, ZAP! A giant spark jumps between the cloud and the ground. That spark is lightning!
Lightning is the same thing as the tiny spark you feel when you touch a doorknob after walking on carpet, just millions of times bigger!