Is the higher the temperature, the stronger the ultraviolet rays?

Not necessarily. Ultraviolet rays are strongest in dry heat (this is the case in the Qinghai-Tibet Plateau). Sometimes the air humidity is high and the weather is sultry, but the ultraviolet rays are not very strong. However, there is little difference in the damage caused by ultraviolet rays, because 8% of ultraviolet rays can penetrate when the skin is dry and 38% of ultraviolet rays can penetrate when the skin is wet. Even on rainy days, you can get sunburned. Don't pay attention to sun protection just because you think the sun is not big.