You should always wear sunscreen during outdoor activities, and cloudy days are no exception. Clouds can reduce the amount of ultraviolet light that reaches the Earth. However, in some circumstances, they amplify UV rays, increasing their intensity. When this happens, you can burn faster on a cloudy day than on a clear one.

Clouds as UV Filters

Clouds block some UV rays, but not all of them. Thick, dense clouds greatly reduce the amount of harmful UV rays that reach you, but the amount of UV light filtered by thin clouds is negligible. On partly cloudy days, clouds can increase your UV exposure, providing numerous edges and surfaces that reflect the UV rays rather than blocking them. Cloudy days are make you less cautious because they are cooler than sunny days. You may be tempted to stay outside longer on a cool, cloudy day, counteracting the filtering effect of the clouds by exposing yourself for a longer time.

Better Safe Than Sunburned and Sorry

Wear sunscreen with an SPF of 15 or higher whenever you head outdoors regardless of cloud cover or season. For the best protection, apply sunscreen 15 to 30 minutes before heading outside for hiking, biking, raking leaves, shoveling snow and other outdoor activities. Reapply every two hours or more frequently when you are swimming or sweating.