When is the strongest ultraviolet ray? Is it cloudy? Will it be reflected like sunlight? Will it be folded? Will the intensity change?

The ultraviolet intensity is divided into five levels: 1 level is the weakest, which usually indicates rain; Level 2 is weak and generally cloudy; Level 3 is medium, generally cloudy, and occasionally a little sun can be seen from the clouds; Level 4 is strong, generally sunny; Level 5 is the strongest, usually showing particularly sunny weather. April-September is the season with the strongest ultraviolet radiation; 10 is the strongest period of ultraviolet radiation from morning to 2 pm; Noon is the peak of ultraviolet radiation.

It will reflect and refract, for example, it will reflect on the surface of glass, tiles, buildings, etc., and it will refract in water when swimming. The intensity will change, for example, the intensity of cloudy days will be weakened by clouds.