Summer is a time for swimming, outings, picnics, and fun. But it's also the best time to get a bad sunburn or worse, a bad case of skin cancer.

Adequate sunlight helps your body make vitamin D but too much can kill you. Aside from premature aging, wrinkles and cataracts, long-term exposure to the sun's ultraviolet rays causes skin cells to grow abnormally and develop into a tumor that can be cancerous.

The most common types of skin cancers are basal cell and squamous cell cancers. Melanoma is less common but more serious. This usually occurs in the fourth or fifth decade of life but 80 to 90 percent of sun-related damage that leads to melanoma occurs before the age of 18.

"There are three major types of skin cancer - basal cell carcinoma, squamous cell carcinoma, and melanoma. Basal cell carcinomas and most squamous cell carcinomas are slow growing and highly treatable, especially if found early. Melanoma is the most serious form of skin cancer. It affects deeper layers of the skin and has the greatest potential to spread to other tissues in the body. Squamous cell carcinoma also can spread internally," according to the Mayo Clinic.

In the United States alone, there are over one million cases of skin cancer reported every year and thousands of deaths annually. This year, the Skin Cancer Foundation estimates that over 59,000 melanomas will be diagnosed and 8,810 people will die of the disease.

At risk are those who spend too much time under the sun like laborers, farmers, sailors as well as students undergoing military training, scouts, campers, athletes, sunbathers, and swimmers.

Others who need adequate sun protection are the elderly who have thin skin and are more vulnerable to the sun's deadly rays, babies with delicate skin that burns easily, those taking drugs like diuretics, tranquilizers, and antibiotics, and those applying astringents.

"Skin cancer begins in your skin's top layer - the epidermis. The epidermis is as thin as a pencil line, and it provides a protective layer of skin cells that your body continually sheds. Normally, skin cells within the epidermis develop in a controlled and orderly way. In general, healthy new cells push older cells toward the skin's surface, where they die and eventually are sloughed off. This process is controlled by DNA - the genetic material that contains the instructions for every chemical process in your body," the Mayo Clinic said

"Skin cancer occurs when this process malfunctions. When DNA is damaged, changes occur in the instructions, which can cause new cells to grow out of control and form a mass of cancer cells," it added.

Fair-skinned individuals are more likely to develop malignant melanoma but that's no reason for those with dark skin to rejoice. While people with dark skin have more melanin pigment which protects them from burning, experts say melanin-rich complexions are not immune from the sun's harmful rays. The longer you stay under the sun, the greater your risk of getting skin cancer regardless of the color of your skin.