Dubrovnik is enjoyable throughout the year, but in wintertime you might find some restaurants to be closed and there will likely be fewer flights scheduled. Spring and Autumn are ideal if you are just visiting the charming city to enjoy its history and the unmissable medieval city center and fortified citadel. If swimming and sunbathing are your goal, then summer is the recommended seasons. August is the busiest summer month, with numerous school groups, which you could avoid by travelling on shoulder summer months.