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The sun is strongest during the hours of 10:00 AM and 4:00 PM. If you can avoid spending extending periods of time in the sun between these hours, do it. Go outdoors in the early mornings or in the late afternoon/evening. You still need to protect your skin from the sun during the early morning and evening, but you'll be less likely to get burned by the most powerful rays. When you're outside, always be in the shade when possible. This is particularly crucial during the peak hours when the sun is most dangerous. If you're at an outdoor restaurant, request a table in the shade. Sit under a tree, enjoy the beach under a canopy, and keep making sure that you're fully covered by shade. Sitting in direct sunlight without sunscreen is dangerous, even if you aren't getting a visible burn. If you are going to be outdoors, do whatever you can to be out of the most powerful rays. In an ideal world, everyone would don sun safe clothing daily, shade would be readily available, and it would be possible to always stay indoors during the sun's peak hours. Of course, that's not always possible. It's useful to keep a UV protection umbrella with you whenever possible, whether that's in your car, your purse, or stashed in your office. The UPF (or the Ultraviolet Protection Factor) will be listed on the umbrella. Choose one with a UPF of 50 or more. These travel sun umbrellas can be purchased on Amazon, or at most stores that sell outdoor equipment and sun safe clothing.
Stay indoors during the sunniest hours. Find shade. Keep an umbrella handy.