UV RADIATION LEVELS ARE INFLUENCED BY:

SUN ELEVATION: The higher the sun in the sky, the higher the UV radiation level.
 
LATITUDE: The closer to equatorial regions, the higher the UV radiation levels.

CLOUD COVER: UV radiation levels are highest under cloudless skies but even with cloud cover, UV radiation levels can be high.

ALTITUDE: At higher altitudes, a thinner atmosphere absorbs less UV radiation.

OZONE: Ozone absorbs some of the UV radiation that would otherwise reach the Earth’s surface.

GROUND REFLECTION: UV radiation is reflected or scattered to varying extents by different surfaces.