Around the world, lightning happens about 3 million times a year, or about 30 times a second.

Not all lightning strikes the ground — lightning can also occur within a cloud or go between clouds. Most of us associate lightning with rainstorms because that is where it is most commonly seen. However, lightning can also happen in volcanic eruptions. In arid climates, lightning often happens in storms producing little or no rain. In winter, lightning occasionally happens when it is snowing.

We usually don’t think about weather on other planets, but lightning has been observed in the atmospheres of Mars, Venus, Jupiter and Saturn. In all of these cases, lightning is a big spark caused by charge separation due to static electricity. The spark heats the air it passes through, causing the air to suddenly expand, which causes a shock wave we hear as thunder.