UV Index & Sun Safety · 8 articles
UV Index Guides & Sun Safety
Practical, science-backed guides to the UV index and sun safety. Learn what the UV index means, which levels are safe, what raises UV exposure through the day and the seasons, and how to protect your skin and eyes — with every figure sourced from the WHO, the US EPA and the CAMS forecast model behind UVI.today.
How Fast the UV Index Falls in Autumn, City by City
In September the clear-sky midday UV index falls by about 2 points across most of Europe, the US and China. Values for 24 cities.
Why You Can Get Sunburned on a Cold or Cloudy Day
Sunburn comes from UV, not heat, and the two regularly part ways. Why a cool spring afternoon or a grey overcast sky can still carry high UV, and how to read the UV index instead of the thermometer.
How UV Forecasts Work, and How Far Ahead to Trust Them
A UV forecast is two forecasts in one: a fixed astronomical ceiling and a changeable cloud forecast. How the UV index is built, and how far ahead it can be trusted.
Does UV Go Through Clouds, Windows, and Water?
Cloud, glass, and water all feel like shade, but each cuts the sun's heat and glare far more than its UV. Here is how much ultraviolet really gets through.
What Is a Safe UV Index, and What Counts as Dangerous?
A UV index of 0 to 2 needs no sun protection; from 3 up it does. Here is what each level of the UV index scale means according to WHO and the US EPA, and why fair skin should take more care.
When Is UV Strongest? Hour-by-Hour UV Patterns Worldwide
Clear-sky UV index curves for six cities, hour by hour: when UV peaks, how long it stays high, and why the strongest summer UV isn't at the equator.
What Affects the UV Index? 7 Key Factors Explained
Solar angle, latitude, altitude, ozone, clouds, surface reflection, and air quality all shape how much UV reaches you — numbers included.
UV Index Official Sources and Resources
A reference list of official organizations, data services, and tools used to monitor UV radiation, generate UV index forecasts, and publish sun safety guidelines.
