In most parts of Australia, the UV Index reaches 11 or more in the middle of summer.
In WA, sun protection is required all year round north of Perth.North of Perth, midday average UV levels are always above 3.
You get sunburnt fastest when your shadow is shortest.When the UV is high the sun is also high in the sky causing it to cast a shorter shadow.
UV levels are just as strong at 9am as they are at 3pm.The UV peaks at solar noon. On a clear sky day, the UV level will be similar at the same interval either side of solar noon. Therefore, UV levels will be similar 3 hours before and 3 hours after solar noon.
UV radiation is invisible and can not be felt.It is infrared radiation that causes heat, not UV radiation.
In Perth there are only 35 days per year in midwinter that you can’t get sunburnt.In June and July the average daily UV Index is less than 3.
UV levels peak at midday even though temperatures continue to rise into the afternoon.UV radiation is not dependant on temperature. You can have high UV even on a cool day.
In December in Perth you need sun protection from around 8.10am to 4.30pmUV levels reach 3 at 8.10am in December and fall below 3 at 4.30pm
You are safe from sunburn after 4.30pm in Perth even during the height of summer.While it may still be warm at 4.30pm in summer the UV levels generally fall below 3 after 4.30pm. UV radiation is not dependent on temperature.
Image courtesy of QLD Health