Honolulu is likely to continue to get "extreme" doses of ultraviolet radiation from the sun over the summer months, putting people at high risk for sunburns and increasing long-term risks for developing skin cancers, say weather and medical experts.

The National Weather Service predicts today will reach the "extreme" ultraviolet index level of 12 in Hono­lulu — which is tied with three other U.S. cities for the highest risk of overexposure.

The index measures the amount of UV radiation that penetrates the atmosphere and reaches Earth’s surface. It ranges from 0, when there’s no sunlight, to a maximum of 15. At level three, UV radiation can start to cause skin damage.

An exposure level of 10 or greater means a fair-skinned person could burn in as little as 10 minutes if not protected. Hono­lulu saw an average 11 rating for June.

"It’s summertime, and the sun is right overhead as opposed to other times of the year. When you have lighter winds and little cloud cover, you’re going to get a lot of sun," said Victor DeJesus, a meteorologist with the National Weather Service’s Hono­lulu office.

He said the exposure level isn’t unusual for the summer months here.

"Throughout the tropics we’re seeing 12s now," DeJesus said. "It doesn’t relate to anything unusual happening in the atmosphere."

Overexposure to UV radiation can cause severe sunburn in the short term and skin cancers after long-term overexposure.

"In Hawaii, when the skies are clear, it’s usually in the 10-to-15 range," said Dr. Kevin Dawson, a dermatologist at the Queen’s Medical Center. "Because we’re much closer to the equator, that already puts us at high risk, but with it also being summertime, the sun is even higher overhead, so we’re getting much more direct exposure."

He said the best protection is to avoid direct sunlight during the middle of the day.

"For things like surfing, running, it’s best to keep out of the sun during the hottest parts of the day. With the days being longer in the summer, I tell patients that if they’re outside anywhere between 9 in the morning and 3, they need to be really careful," said Dawson, who’s also an assistant clinical professor at the University of Hawaii’s John A. Burns School of Medicine.

He recommends physical protection — such as umbrellas, hats, rash guards and dry-fit shirts — coupled with sunscreen of at least 30-SPF strength for anyone staying outdoors.

"I see extreme sunburns all year round, but with kids on summer break and families barbecuing and staying at the beach all day, I am seeing more cases," Dawson said. "Every time you get a sunburn, you significantly increase your long-term risk of getting skin cancer."

To treat a mild sunburn, Dawson recommends moisturizing to keep the skin cool. Aspirin or ibuprofen can be taken to help stop inflammation.

"If there’s blistering or they’re feeling tired or have a lack of energy after a burn, they should seek medical attention," he said.

Dawson said children have a higher risk of sun damage.

"Most of our sun damage happens early in life, so we need to be most careful with kids who tend to spend a lot of time outdoors," he said. "Parents can play a big role in that."