Why is there a traffic jam when it rains?

The biggest reason should also be slippery roads. On rainy days, there is water on the road surface, which leads to slow braking, so people can't help but slow down when driving, which will inevitably lead to normal road congestion and traffic jam.

Then if the rain is heavy, it will also cause bad vision, and it is necessary to reduce the speed to ensure driving safety.

So rain is also the cause of many accidents. Often a traffic accident in one place will definitely affect the already congested traffic flow and become completely blocked.