A civil engineer, Amid Bhasin likens the process to a chain reaction:
It starts slowly at a weak spot, and once it starts falling apart, that creates larger cracks; then more water gets into it, and the cracks grow larger.
Bruce Hucker, an engineer with the Illinois DOT, explained that potholes could also emerge after the ground beneath the road gets wet and sinks down.
When you step on a dry yard, you don't leave any indentation because it's hard and it fully supports your weight. But when it gets wet, your shoe sinks down in it.
The pavement will eventually crack after traffic drives over these spots and weakens the pavement.
To read more about how these annoying potholes form, check out Popular Mechanics.