Beaches have a high hedonic value and economic potential; they are pillars of tourism which has been increasingly associated with vacationing wholly, or partially, at coastal locations and beach recreational activities according to the 3S (Sun, Sea and Sand) touristic model. The visitor’s satisfaction and the attractiveness of a beach depends on several climatic factors such as temperature (i.e., thermal sensation index - PET), wind, cloudiness and rain. Future changes in the climatic conditions under Climate Change, such as temperature increases (and corresponding thermal discomfort) can affect the attractiveness of the beaches. A specialized bio-climatic index (the Climate Index for Tourism – CIT) was used in this contribution in order to assess the ideal climate conditions for a tourist to visit the beach and to evaluate the present and future attractiveness of the island 3S destinations of Kos and Santorini, as a touristic product.