The magic snowy period from December through March is the best time to visit Finland. Snowmobiling, dog sledding, ice-fishing, and snowshoeing are there for you. And December is the time to meet Santa in his village!
Summer in Finland is warm and it's the right time for hiking, boating, and wild berry picking. Beer floating takes place in July. But it is also much more crowded with significantly higher prices. And remember that after the summer is over, from September through March, you have a reasonable chance to witness the Northern Lights.