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.

Last Updated: December 21, 2009

Author: Jan Nissl, RN, BS

Medical Review: H. Michael O'Connor, MD - Emergency Medicine & Martin Gabica, MD - Family Medicine

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