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Understanding the UV Index: Your Guide to Sun Safety

June 17, 2026 · The Clime Team
Understanding the UV Index: Your Guide to Sun Safety

The Ultraviolet (UV) Index is a daily forecast that indicates the expected risk of overexposure to UV radiation from the sun. Developed by the U.S. Environmental Protection Agency (EPA) and the National Weather Service, it helps individuals make informed decisions about sun protection. (epa.gov)

What Does the UV Index Measure?

The UV Index predicts the intensity of UV radiation on a scale from 1 (low) to 11+ (extremely high). This scale considers factors such as ozone depletion, time of year, and local weather conditions to estimate the potential for skin damage. (epa.gov)

Understanding the UV Index Scale

  • Low (1-2): Minimal risk. No protection needed. You can safely enjoy being outside. (epa.gov)

  • Moderate (3-5): Moderate risk. Protection needed. Seek shade during midday hours. Wear protective clothing, a wide-brimmed hat, and sunglasses. Apply broad-spectrum SPF 30+ sunscreen. (epa.gov)

  • High (6-7): High risk. Protection needed. Reduce time in the sun between 10 a.m. and 4 p.m. Seek shade, wear protective clothing, a wide-brimmed hat, and sunglasses. Apply broad-spectrum SPF 30+ sunscreen. (epa.gov)

  • Very High (8-10): Very high risk. Extra protection needed. Take all precautions. If your shadow is shorter than you, seek shade. Wear protective clothing, a wide-brimmed hat, and sunglasses. Apply broad-spectrum SPF 30+ sunscreen. (epa.gov)

  • Extreme (11+): Extreme risk. Take all precautions. Avoid sun exposure between 10 a.m. and 4 p.m. Seek shade, wear protective clothing, a wide-brimmed hat, and sunglasses. Apply broad-spectrum SPF 30+ sunscreen. (epa.gov)

How Is the UV Index Calculated?

The UV Index is calculated using a computer model that relates the ground-level strength of solar UV radiation to forecasted stratospheric ozone concentration, forecasted cloud amounts, and elevation of the ground. This model provides a daily forecast of the expected intensity of UV radiation from the sun. (epa.gov)

Sun Safety Tips

  • Limit Sun Exposure: Especially between 10 a.m. and 4 p.m., when UV radiation is strongest.

  • Seek Shade: Use umbrellas, trees, or other shelters to reduce direct sun exposure.

  • Wear Protective Clothing: Opt for long-sleeved shirts, pants, and wide-brimmed hats.

  • Use Sunscreen: Apply broad-spectrum SPF 30+ sunscreen generously and reapply every two hours, or after swimming or sweating.

  • Wear Sunglasses: Choose sunglasses that block 100% of UVA and UVB rays to protect your eyes.

UV Alerts

The EPA issues UV Alerts when the UV Index is unusually high for a specific area. These alerts provide additional sun safety recommendations to help reduce the risk of overexposure. (epa.gov)

Conclusion

Understanding the UV Index is essential for making informed decisions about sun exposure and protecting your skin and eyes from harmful UV radiation. By staying informed and following sun safety guidelines, you can enjoy outdoor activities while minimizing health risks.

Highlights:

  • Learn About the UV Index | US EPA, Published on Monday, January 26
  • UV Index Overview | US EPA, Published on Monday, March 23
  • UV Index Scale | US EPA, Published on Wednesday, January 21

Frequently Asked Questions