The warning comes from the charity Cancer Research UK, with the message most relevant for the Channel Islands which has one of the highest rates of skin cancer in the British Isles.
About 40 islanders a year are diagnosed with malignant melanoma, which if found at a late stage can prove fatal.
Experts say skin cancer is almost entirely preventable by covering up with cool clothing and a hat, using sunscreen over Factor 15, and seeking shade between 11am and 3pm.
Di Mathews from the Health Promotion Unit in Guernsey said: "We all need to look after our skin and keep our skin young and healthy looking, particularly young people actually. Perhaps the increase in incidents is due to better diagnosis, or perhaps they didn't take as much care of their skin when they were younger, so look after your skin throughout your life. You need it for your whole life so yeah look after it throughout your life."
With islanders and visitors making the most of the sunshine on what is the hottest week of the year so far, it is easy to forget the risks.
Those who deal with skin cancer hope their reminder about protection will be heeded as the advice could save your life.