With the official start of summer just a couple of weeks away — the summer solstice, the longest day of the year, is June 21 — there’s one big number to keep in mind: More than 91,000 people will be diagnosed with melanoma, the most serious and deadly type of skin cancer, in 2018, and 9,320 people will die of the disease, according to estimates by the American Cancer Society. Another 5.4 million cases of the less-serious types of skin cancer, basal cell and squamous cell, are expected to be diagnosed this year. These numbers are what makes skin cancer the most common cancer in the country. Excessive exposure to the sun’s ultraviolet (UV) rays is to blame. The Skin Cancer Foundation says that having five or more blistering sunburns throughout your life more than doubles your odds of developing melanoma. To protect yourself, it’s critical to apply sunscreen with an SPF rating of at least 15 and both UVA and UVB protection whenever you’re exposed to the sun. Your skin will be exposed to UV rays even on a cloudy day, so don’t skimp on sunscreen then, either. Dermatologists advise applying sunscreen liberally before you go out and then reapplying every two hours. And if you’re in and out of the pool or the ocean, reapply each time you come out of the water.