You can travel all the countries below year-round. Green marks, sure best times to visit but mind that it will be the most crowded months. Red marks doesn’t mean you shouldn’t go, just be aware of you may not enjoy all of the things because of rough weather conditions. Be prepared and flexible. Yellow marks pointing also good times to visit with slightly changed weather conditions that won’t affect your trip.
This table is a generalized best season info for the countries. For a certain part, place, city.. etc you are advised to research more details of it.