What Is UV Radiation?
Ultraviolet radiation is invisible energy from the sun that reaches Earth's surface. It is divided into UVA (ages skin) and UVB (burns skin). Both contribute to skin cancer risk.
Understanding the UV Index
| UV Index | Level | Time to Burn (fair skin) |
|---|---|---|
| 1-2 | Low | 60+ minutes |
| 3-5 | Moderate | 30-45 minutes |
| 6-7 | High | 15-25 minutes |
| 8-10 | Very High | 10-15 minutes |
| 11+ | Extreme | Under 10 minutes |
Factors That Increase UV
- Altitude: UV increases ~10% per 1,000m elevation
- Snow: Reflects up to 80% of UV rays (nearly doubling exposure)
- Water: Reflects 10-30% of UV
- Sand: Reflects 15-25% of UV
- Time of day: 60% of daily UV falls between 10am and 2pm
- Latitude: Closer to the equator = higher UV year-round
- Clouds: Thin clouds let through up to 80% of UV (you can burn on cloudy days)
Protection Guidelines
| UV Index | Action |
|---|---|
| 1-2 | Sunglasses on bright days |
| 3-5 | Sunscreen, hat, sunglasses |
| 6-7 | Sunscreen SPF 30+, seek shade at midday |
| 8-10 | Avoid midday sun, SPF 50+, protective clothing |
| 11+ | Stay indoors 10am-4pm if possible |
Sunscreen Guide
- Apply 20 minutes before sun exposure
- Use at least SPF 30 (SPF 50 for fair skin or high UV)
- Reapply every 2 hours, and immediately after swimming
- Do not rely on sunscreen alone — combine with shade, hats, and clothing
Check the UV index for your city on Weather Tomorrow.
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