system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is some thunder longer than others?
gpt
There are a few factors here.  Thunder is created when lightning zips through the air, causing a sudden heating up of the air, that causes a blast wave to go out from that point.

Not all lightning is straight down from the clouds.  Some of it kinda does a zig zaggy thing which will cause longer thunder.  But also, sometimes there isn't a single strike.  Sometimes there are 2+ strikes all within just like 1 or 2 seconds in the same area.  So this action causes several waves of thunder to be really close in time to each other.  So you hear it as a longer rolling thunder.

The other thing that can happen in a very active storm is that a lightning strike can happen way off in the distance and then one closer a couple second later, so the sound waves hit your ears pretty close together.  So they sound more like rolling thunder.