UVR
UVR is strongest between 10:00AM and 2:00PM. Clouds filter some but not most of the UVR so it's still possible to get burned on a cloudy day. Some ground surfaces such as sand and snow reflect most of the UVR. For instance snow can reflect as much as 80% on the incident UVR Water actually reflects very little UVR. For every 1000 feet increase in altitude the UVR increases by 4%.
