WHAT AFFECTS THE LEVELS OF UVR?

The angle of the sun - the higher the sun is in the sky, the shorter the path the UVR travels to reach the earth's surface. Therefore, less radiation is absorbed by the atmosphere.

Geography - the closer you are to the equator, the higher the amount of radiation to which you will be exposed. 

The season - during the winter months, the sun is lower in the sky, so UVR levels are lower.

Cloud - UVR is able to penetrate light cloud cover, so on lightly overcast days the levels can be similar to a cloud-free day. Heavy cloud can reduce the intensity of UV radiation.

Ozone - this is a form of oxygen, which occurs naturally in the earth's upper atmosphere, and is capable of absorbing most UVB and all UVC radiation. Levels of ozone change from day to day and season to season. An ozone ‘hole' has been discovered over Antarctica. Winds in the stratosphere sometimes carry ozone-depleted air towards Australia, causing increases in radiation levels.

Scattering - UVR is easily scattered by particles in the atmosphere, so you are still at risk of scattered UVR exposure, while you're in the shade.

Environment - highly reflective surfaces such as snow, sand, water, white paint and concrete can reflect UV radiation onto your skin.

Altitude - for every kilometre increase in altitude, the intensity of UVR increases by about 12%. This is due to the thinner atmosphere at high altitudes, which allows more radiation through.

Thank you to the Australian Radiation Protection and Nuclear Safety Agency for providing information.