The climate of Patmos island is Mediterranean with mild winter and cool summer. It is also wet the main cause being the rainfalls caused due to north and west sea winds. The best time for travelling to Patmos depends on what you want to do. If you go for swimming and leisure, end of May through September is the best time for travelling. In October the sea is still warm enough (20 degrees C) but it more often rains and who wants something like that in a holiday! The most rain falls in December but as a tourist you normally won't be there. For wandering April, May and September are the best months to visit Patmos.