Robot lawn mowers can mow in the rain so long as they are cutting the grass every day i.e. it is not too long. Some makes have rain sensors which allow you to send them back to the base when it rains, but this feature is usually configurable. We advise putting your mower into storage for the winter as the grass is not growing and the ground usually gets very soft. We put ours away in October/ November and get it out again in March/ April…it depends on the weather and lawn conditions. You can use a robot mower when a conventional mower would be too heavy and damage the ground.
Most robot now come with a recommended procedure for winterising your robot lawn mower.