UV Index
Sunburn risk from ultraviolet radiation
What is it?
The UV Index measures the strength of sunburn-producing ultraviolet radiation at the Earth's surface. It was standardized by the World Health Organization so a given number means the same risk anywhere in the world.
How we measure it
Daily maximum UV index (unitless, open-ended scale starting at 0) from the Open-Meteo forecast, which models solar elevation, ozone and cloud cover.
WHO UV Index categories
- 0–2LowMinimal risk for most people
- 3–5ModerateSeek shade during midday hours
- 6–7HighProtection required — sunburn possible in ~30 min
- 8–10Very highExtra protection — unprotected skin burns quickly
- 11+ExtremeUnprotected skin can burn in minutes
Within safe range
At Low (0–2) most people can stay outside without special protection, though reflective surfaces like snow and water can still roughly double exposure.
Beyond the range
From High (6+) upward, unprotected exposure causes sunburn in under half an hour, accelerates skin ageing, and raises long-term skin-cancer and cataract risk. UV peaks between about 10 am and 4 pm even when the air feels cool — UV is radiation, not heat.
Precautions
- Check the daily max before planning outdoor time; schedule around the 10 am–4 pm peak.
- Broad-spectrum SPF 30+ sunscreen, reapplied every 2 hours and after swimming.
- Wide-brim hat, UV-blocking sunglasses, long sleeves at High or above.
- Seek shade — shadows shorter than you mean UV is strong.
- Children and high-altitude locations need extra care (UV rises ~10% per 1000 m).