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Shadow rule for preventing sunburn

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Shadow rule for preventing sunburn

The shadow rule is a way to estimate exposure to ultraviolet (UV) light on a sunny day. A shadow that is longer than the person means UV exposure is low; a shadow that is shorter than the person means the UV exposure is high.

The risk of sunburn and skin damage is greater at higher levels of UV exposure. During times when a person's shadow is short, usually between 10 a.m. and 4 p.m., it is best to stay indoors or in the shade. If outside, wearing sunscreen, sunglasses, and a hat can help protect a person's skin and eyes.

Current as of: May 1, 2026

Author: WebMD Ignite Staff

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This information does not replace the advice of a doctor. WebMD Ignite, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.

NOTICE: This health information was not created by Columbia University Irving Medical Center and may not necessarily reflect specific CUIMC practices. For medical advice to your personal condition, please consult your doctor. Medical advice disclaimer.