Clouds provide little protection from the sun's rays. Kids should wear photoprotective clothing and wide-brimmed hats. Just wearing a white T-shirt isn't good enough. A wet, light-colored shirt transmits almost as much light to a child as does his bare skin. So dress them in dark colors with long sleeves and pants whenever possible.
Some companies specialize in designing photoprotective clothing.
Your dermatologist can recommend an appropriate brand. Sit in the shade when outdoors. Use a lip balm with an SPF of 15. Apply it liberally on all exposed skin a half-hour before going in the sun, and reapply after swimming or perspiring, even if the label says the product is waterproof. Regardless of activity, reapply sunscreen every two hours, even on cloudy days.