UV Sun Exposure Risk
What is the UV Sun Exposure Risk?
The UV Index is an internationally standardized measurement that quantifies the intensity of ultraviolet (UV) radiation from the sun reaching the Earth's surface at a specific location and time. This index ranges from 0 to 11+ and is calculated based on multiple environmental factors, including the sun's position in the sky, altitude, cloud cover, surface reflection, and atmospheric ozone concentration. Higher values indicate greater risk of immediate and long-term damage to the skin (sunburn, premature aging, skin cancer) and eyes (cataracts, corneal burns). It is essential to adopt protective measures when the UV index reaches 3 or higher, especially during peak sun hours between 10 AM and 4 PM, when UV radiation is most intense and dangerous.
How is the UV Sun Exposure Risk calculated?
- Sun position: The higher the sun is in the sky (noon, equatorial latitudes), the greater the UV intensity. The index increases during summer and central hours of the day (10 AM-4 PM).
- Altitude: For every 1000 meters of altitude, UV radiation increases approximately 10-12% due to less atmospheric thickness filtering UV rays.
- Cloud cover: Thick clouds can reduce UV radiation by 50-90%, while thin clouds have little effect. Clear skies significantly increase the UV index.
- Surface reflection: Reflective surfaces like snow (up to 80% reflection), sand (15-25%), and water (10%) increase UV exposure by reflecting rays back to the skin.
- Ozone concentration: Stratospheric ozone absorbs UV radiation. Low ozone levels (such as in ozone holes) result in higher and more dangerous UV indices.
Understanding the UV Sun Exposure Risk Scale (0-11)
UV Sun Exposure Risk: Top Cities Comparison
| City | Country | Today | Tomorrow | Change |
|---|---|---|---|---|
| Tokyo | Japan | 0 / 11 Very Low | 0 / 11 Very Low | 0 |
| Osaka | Japan | 1 / 11 Very Low | 0 / 11 Very Low | -1 |
| Kyoto | Japan | 1 / 11 Very Low | 0 / 11 Very Low | -1 |
| London | United Kingdom | 0 / 11 Very Low | 0 / 11 Very Low | 0 |
| Rome | Italy | 0 / 11 Very Low | 0 / 11 Very Low | 0 |
| Paris | France | 0 / 11 Very Low | 0 / 11 Very Low | 0 |
| Delhi | India | 1 / 11 Very Low | 1 / 11 Very Low | 0 |
| Florence | Italy | 0 / 11 Very Low | 0 / 11 Very Low | 0 |
| New York City | United States | 0 / 11 Very Low | 0 / 11 Very Low | 0 |
| Hanoi | Vietnam | 1 / 11 Very Low | 1 / 11 Very Low | 0 |
UV Sun Exposure Risk: Tips & Recommendations
- Use SPF 30+ sunscreen when UV index is 3 or higher
- Seek shade between 10 AM and 4 PM when sun is strongest
- Wear UV-blocking sunglasses, hat, and protective clothing
- Reapply sunscreen every 2 hours