About the UV index

What is the UV Index?

The UV Index is a simple and informative way of describing the daily danger of solar UV radiation intensity. Each point on the Index scale is equivalent to 25 milliWatts/square metre of UV radiation.

Types of UV Index forecasts

The UV Index forecast is issued in four types of format. It is presented as a map of Australia as well as graphs and text tables for over 200 cities and towns. A plain text version is also available on the Bureau's FTP site. The graphs and text UV Index forecasts include the SunSmart UV Alert.

What are the sun protection times?

The sun protection times in the forecast are the times of the day when sun protection measures are recommended such as slip, slop, slap, seek and slide. This is the time of the day when the UV Index is 3 or above in clear sky conditions.

UV Radiation - a healthy balance

The sun's ultraviolet (UV) radiation is the major cause of skin cancer and also the best source of vitamin D. In Australia we need to balance the risk of skin cancer from too much sun exposure with maintaining adequate vitamin D levels.

Australia has the highest incidence of skin cancer in the world. More than 1700 Australians die from skin cancer each year, and two out of three Australians will get a skin cancer before the age of 70.

You can't see and you can't feel ultraviolet (UV) radiation - heat or high temperatures are not an indication of UV radiation.

We need vitamin D for good health and to keep bones and muscles strong. Sensible sun protection does not put people at risk of vitamin D deficiency.

5 steps to be SunSmart

Cancer Council Australia recommends Australians take five steps to protect against sun damage when the SunSmart UV Alert indicates the UV Index is at 3 or above:

1. Slip on some sun-protective clothing - that covers as much skin as possible
2. Slop on SPF50 or SPF50+ sunscreen - make sure it is broad spectrum and water resistant. Put it on 20 minutes before you go outdoors and every two hours afterwards. Sunscreen should never be used to extend the time you spend in the sun.
3. Slap on a hat - that protects your face, head, neck and ears
4. Seek shade
5. Slide on some sunglasses - make sure they meet Australian Standards

If UV levels are low (i.e. less than 3) sun protection is not recommended unless you work outdoors, or are near reflective surfaces (like snow) or outside for extended periods.

Facts about UV Radiation

• The sun emits UVA, UVB and UVC radiation. The ozone layer blocks all UVC radiation, most UVB but none of the UVA radiation.
• UVA penetrates deep into the skin causing damage like wrinkles and discolouration.
• Exposure to UVB causes sunburn. Sunburn, whether severe or mild, can cause permanent skin damage.
• Skin cancer is a disease of the body's skin cells caused mainly by overexposure to UV radiation.
• Heat or high temperatures are not an indication of UV levels.
• Factors such as latitude, ozone, cloud, reflection from surfaces, time of year and time of day determine UV levels.
• UV levels vary in intensity and level across Australia on any given day.
• When the UV Index reaches 3, sensible sun protection is warranted and is unlikely to put people at risk of Vitamin D deficiency.

Calculating the danger

A computer model is used to forecast the UV radiation at ground level. It takes into account information on the time of day, date, latitude, altitude and ozone concentrations.

The maximum UV Index is calculated for midday assuming cloud-free skies. Only clear-sky UV Index values are included in the tabular forecast, charts and graphs.

View our FAQ's for more information about how UV levels may be affected.