Your questions answered

Here, we answer the most commonly asked questions from the UVLens community. If you have a question that we haven't answered here, please contact us and we will be more than happy to help!

How does UVLens work?

UVLens helps you stay safe in the sun by providing you up to date forecasts of UV intensity over the day. It uses forecast models that power many weather services around the world combined with our team's own algorithms to ensure you get relevant, easy to understand information wherever you are in the world.

As well as informing you of the UV intensity, UVLens also helps you understand its effect on your own skin. To most people, a UV index of 8 doesn't mean much. Understanding that you could burn in as little as 15 minutes is a lot more practical in terms of knowing the precautions you need to take to protect yourself.

How do you calculate UV index?

The UV index is calculated using a computer model that relates the ground-level strength of solar ultraviolet (UV) radiation to forecasted stratospheric ozone concentration, forecasted cloud amounts, and elevation of the ground. The different spectrums of UV (UV-A, UV-B, UV-C) are then weighted according to sensitivity of the human skin to UV radiation.  For more information, see the link below.
EPA - Calculating the UV Index

Why is the UV index different from other weather apps?

Many weather services report only the maximum UV over the day. The UV index changes throughout the day due to the position of the sun in the sky. Typically, the UV is the highest around noon. This varies, however, by country depending on your timezone and whether daylight savings (summer time) is in effect. UVLens provides a forecast of the UV per hour so you can be more precise in your planning your time outdoors.

Another factor that affects UV is cloud cover. More often than not, services that report the current UV use the "clear sky UV". This is what the UV level would be if there were no clouds. However in reality, cloud cover can change (but not completely block) the amount of UV that reaches the surface of the earth. UVLens takes into account cloud cover, ozone, aerosol and other factors in the calculation.

The sun has not set but the app says there's no/little UV. Is something wrong?

Sunset can occur much later into the evening during summer, particularly in countries close to the poles. However, the amount of UV close to sunset is a lot lower than noon, despite there still being plenty of visible light.

The reason is when the sun is close to the horizon, light has to travel through a lot more atmosphere to reach the ground (compared to when it is directly above). By the time it reaches you, the particles in the atmosphere would have scattered most of the UV radiation.

This concept actually makes dawn and dusk perfect times to enjoy the sun. There's sunlight, yet you are still safe from getting sunburnt!

It's the middle of the day in winter and the sun is shining strong. UVLens says I'm safe in the sun. What gives?

During winter, the sun does not "rise" as high up in the sky. Like dusk and dawn, the closeness to the horizon means that a lot of UV is scattered by the atmosphere, giving rise to a lower UV index.

Are you bringing any new features such as Apple Watch support, or being able to load multiple profiles?

We would love to bring out new features! However they do take time and money to build. Right now, we are trying to build a community to support us in developing new features. If you would like to contribute in any way, whether it is suggestions, expertise or funding, please check out the page below.

Support Us