It's that time of year where we head outdoors to enjoy a picnic or jump in the pool for a swim. The sun's rays may feel great after the long winter, but to keep your skin from crisping, you're going to need to slather on the sunscreen.

There are three things to keep in mind when choosing a sunscreen: It should protect against both the damaging UVA and UVB rays, have an SPF of 30 or greater, and be water-resistant.

It's important to apply it about 15 to 30 minutes before you go outside so it has time to form a protective layer, said Katie Lockwood, an attending physician at Children's Hospital of Philadelphia. It is also important to reapply after about 40 minutes of activity or just after swimming, she said.

One in five Americans will develop skin cancer over the course of a lifetime. It is estimated that about 178,500 new cases of melanoma, the most deadly form of skin cancer, will be diagnosed in the United States in 2018, according to the American Academy of Dermatology.

Sunscreen goes only so far. Hats and other protective clothing will help you avoid sunburn. Plan activities early or late in the day when the sun isn't as strong. Pack an umbrella or tent to create your own shade.

Don't forget sunglasses – your eyes need protection from UV rays, too – and an SPF lip balm.

Spray vs. lotion

With a spray sunscreen it is harder to know whether you are getting full coverage. Some companies make zinc oxide sunscreens with white spray, making it easier to see how much of the skin is covered. It's important to know that aerosol sprays can be inhaled, making them a trigger for kids with asthma or allergies. The best solution is to spray your hands and apply it liberally on your body, Lockwood said.

"For any kid, we don't want it to end up in their lungs," she said.

Is a higher SPF better?

Pick a product with an SPF of at least 30. Sunscreen with an SPF of greater than 50 provides only  marginally better protection. A higher SPF number may give the user a false sense of security; it may not be reapplied when needed, Lockwood said.

"There is no reason to go higher than 50," she said. Look for products with active ingredients such as zinc oxide and titanium dioxide, she said.

What about sunscreen for infants?

Sunscreen products are not tested for children younger than 6 months of age. The best protection for infants is sun avoidance. Use big hats and sun shirts, and keep them in the shade.

For kids older than 6 months, sunscreen doesn't have to be specifically developed for children as long as it meets the needed criteria. The advantage of sunscreens aimed at kids is that they don't have added fragrance or perfumes, she said.

Are teens good about using sunscreen?

Teens should be encouraged to reapply sunscreen often, something they may not think to do when they are out and about, Lockwood said.

There is a misconception among teens when it comes to tanning salons. They tend to want a "base" tan before they head to the beach so their skin won't look pale. But use of tanning beds, which can increase the risk of deadly melanoma skin cancer, will not give any added protection from sunburn, she said.

What to do if you get a sunburn

If you get sunburned, try cool compresses. Calamine lotion or an aloe vera-based gel can also provide some relief. For painful burns, take an anti-inflammatory such as ibuprofen, Lockwood said.

"If you have any blisters, don't deliberately pop them," she said. Clean any broken blisters with soap and water and use Vaseline or topical ointment to keep them from getting infected, she said.

Which sunscreens work best?

The nonprofit Environmental Working Group publishes an annual guide to sunscreens, which rates the effectiveness and safety of U.S. products.

There are 216 beach and sport sunscreens with a green rating in EWG's 12th annual sunscreen guide. The group rated 23 of the best-scoring sunscreens specifically marketed for use on babies and kids: