Most of us glance at the temperature and decide whether to grab a jacket. Far fewer of us pay attention to the UV index — and that's a mistake. The UV index is one of the most practically useful numbers in any weather forecast, directly affecting your risk of sunburn, eye damage, and long-term skin health.
Here's everything you need to know about it.
The UV index (UVI) is an international standard measurement of the strength of ultraviolet radiation from the sun at a particular place and time. It was developed by the World Health Organisation (WHO) and ranges from 0 (no UV radiation, e.g. at night) upward, with values above 11 classified as "extreme."
The higher the number, the less time it takes for unprotected skin to burn.
| UV Index | Risk Level | Recommended Protection |
|---|---|---|
| 0–2 | 🟢 Low | No protection needed for most people |
| 3–5 | 🟡 Moderate | Sunscreen SPF 30+, hat recommended |
| 6–7 | 🟠 High | SPF 30-50+, seek shade during midday |
| 8–10 | 🔴 Very High | SPF 50+, protective clothing, limit sun exposure |
| 11+ | 🟣 Extreme | Avoid direct sun. Unprotected skin can burn in minutes |
UV radiation is strongest between 10am and 4pm, peaking around solar noon (typically 12–2pm local time). UV levels are also higher in summer, at higher altitudes, closer to the equator, and when reflected off snow, water, or sand.
This is one of the biggest misconceptions in weather. Cloud cover can reduce UV radiation by 10–80%, depending on cloud thickness and type. On a partly cloudy day, UV levels may still be high enough to cause sunburn — particularly if the UV index is 6 or above.
UV 0–2: Enjoy the outdoors freely. Still worth applying SPF moisturiser as a daily habit.
UV 3–5: Apply SPF 30 sunscreen if you'll be out for more than 30 minutes. Sunglasses are a good idea.
UV 6–7: Reapply sunscreen every 2 hours. A wide-brimmed hat will protect your face and neck significantly.
UV 8+: Minimise time outdoors around midday. If outside, cover exposed skin and stay in shaded areas as much as possible.
ClearCast displays the current UV index for any location worldwide, with a colour-coded visual bar showing exactly where today's UV level sits on the scale — from Low to Extreme. Simply search your city and scroll to the UV Index section to check before you head out.