In many parts of the country, the sun is still shining strong — and that means your sunscreen should be able to stand up to the heat. But a new study from the McGraw Medical Center at Northeastern University found that nearly half of all sunscreens don’t meet the American Academy of Dermatology’s basic safety standards.

The study inspected the labels of more than 65 sunscreens sold online and checked them for minimal resistance to sweat and water. While 40 percent failed, researchers suggested that could be because many products, while labeled sunscreen, are not the kind formulated for long days of exposure to sun, sand and water that you find at the beach.

Dermatologists recommend that people wear sunscreen with a sunscreen protection factor of at least 30 to block 97 percent of the sun’s rays no matter what activity they’re doing, whether it’s commuting to work or spending a day at the beach. Look for labels that are marked “broad-spectrum protection,” which suggests that the formula blocks the ultraviolet rays that cause sunburn and give the skin an aged look. And if you are planning to sweat and swim, go for the added protection of sweat- and water-resistant sunscreen.

Don’t limit your protection to sunscreen, though. Plan ahead for long exposure to rays and wear sunglasses, wide-brimmed hats and clothes made of tightly woven fabrics. Some clothes even come formulated with extra SPF protection in the fibers. Shade helps, but the sun’s rays can still bounce off the sand and water, so don’t skip protection. And when you do find that perfect bottle of sunscreen, be sure to keep track of its expiration date. Sunscreens are generally good for three years. Now, your fun in the sun can be safer.