Sweden is a year round destination, with long warm summer days and crisp white snow covered winters.
The best time to visit for warmer activities is early summer, when the temperatures are pleasant and the days are long. It may be best to avoid midsummer, as Swedes vacate the cities for their summerhouses, and attractions may close during this time.
Late November and December are also wonderful times to visit, when you get to see Sweden in a different light, with the chance to explore the Christmas markets and head up north for winter activities.