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 is the UV Alert?
The UV Alert is issued when the UV Index forecast is 3 or above, a level that can damage your skin and lead to skin cancer. The higher the Index value, the greater the potential for damage to your skin. The UV Alert shows the time of the day people need to be SunSmart.
The UV Alert is an initiative of Cancer Council Australia, the Bureau of Meteorology and the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). It is based on the World Health Organisation's Global Solar UV Index.
The UV Alert can be found on the weather page of most Australian daily newspapers. SunSmart UV Alerts are linked from the forecast pages for each State and Territory.
How to read the UV Alert
The sample UV alert graph shows time, in two hour blocks, on the x (horizontal) axis and UV index (see below) on the y (vertical) axes. The period of day that you sould be SunSmart is in the top left corner of the chart. In this case that is between 8:50am and 4:00pm. Underneath the UV alert period the maximum UV Index level forecast for this day is shown as a number. In this example 12 - which is extreme.
UV index range
The UV index range is expressed as a numeric value from 0 to 20 and as bands of colour representing the risk level of skin damage due to UV exposure from Low (0-2), Green, to Extreme (11+), Purple.
- Low (0-2): Green
- Moderate (3-5): Yellow
- High (6-7): Orange
- Very High (8-10): Red
- Extreme (11+): Purple
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:
- Slip on some sun-protective clothing - that covers as much skin as possible
- Slop on SPF30+ 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.
- Slap on a hat - that protects your face, head, neck and ears
- Seek shade
- Slide on some sunglasses - make sure they meet Australian Standards
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.