A skin tan is a sign that your skin has absorbed ultraviolet radiation (UV rays) and been damaged. Your skin releases melanin, which darkens your skin, and the three factors in suntanning are your skin, the sun, and protection.
We measure UV rays on the UV index from zero to 10+, the higher the more dangerous, and though there are two types of rays, UVA and UVB, both are bad for your skin.
To counteract UV we have SPF, the Sun Protection Factor of sunscreen creams, which lower your risk of burning by screening out an amount of UV rays. The SPF's range from four to 50, with SPF-15 considered the bare minimum and SPF-30 probably being only adequate for sunning in Hawaii.
The other factor in suntanning, besides UV and SPF, is the lightness or darkness of your skin. Pale skin needs a higher SPF to protect it from the UV, and usually darker complexions need somewhat less.
Because no two people tan alike, everyone should figure out has to protect their own skin. You're best bet is to pick up a bottle of sunscreen and use it.
Protection
Use waterproof sunscreen. UV rays are just as strong on land as when your splashing around in the ocean.
Freshen your sunscreen every 20 minutes.
Dress in loose, light-colored clothes during the day and wear a wide-brimmed hat.
Your sunglasses, which are somewhat mandatory, have to be able to block both UVA and UVB.
The medicine you are taking can sometimes make you more prone to burn. Read those labels. Oral contraceptives, antibiotics, antihistamines, and other drugs can make you more susceptible to burn.
The Sun
Avoid the sun between ten a.m. and four p.m., when UV is strongest.
Sand and water reflect UV rays so you can "overdo it" even under an umbrella.
Clouds only block about 20% of UV.
If you go to Halekahala or Mauna Kea, etc., remember that for every 1,000 feet you go up over sea level UV rays increase by about five percent.
The sun is strongest at the Equator, and Hawaii is pretty damn close. It's in the tropics, which means the sun is directly overhead for most of the day.
