The weather forecast shows that ultraviolet rays are very weak. What do you mean?

Ultraviolet light is a kind of sunlight, which will do harm to living things for a long time. Generally, ultraviolet rays will be weakened by the weakening of sunlight and also by the ozone layer above the atmosphere. The weather forecast suggests that ultraviolet rays will be weak because of cloudy or cloudy days, because most of the sunlight is blocked at this time.