Clouds and infrared and UV

Infrared radiation actually composes a range of wavelengths. From [near infrared] to [far infrared].

Near infrared radiation, because of its wavelength is close to that of red light, could be partially absorbed by clouds. However, clouds itself could also emit infrared radiation, but of longer wavelengths because of their lower temperature.

Ultraviolet could penetrate clouds unless the clouds are froming very thick layer, such as those in thunderstorm. As you may aware that the UV index reported by the Hong Kong Observatory could be HIGH (UV index of 6 or above) on overcast days.