hi there,
The Finnish Northern Lights are best viewed in the winter, when the sun barely rises and an almost complete darkness settles in.
There are some unique
Finland tours that include attempts at seeing the
Finnish Northern Lights, and though you are never guaranteed to see them, your chances are pretty good up north.
I would say, the opportunities to see the Northern Lights on a Finland vacation decrease in the summertime, which as opposed to winter, sees an unusual amount of daylight.
In fact, come midsummer, 21 hours of daylight is the norm, so you can enjoy all kinds of outdoor activities long into the night when you enjoy Finland travel in the summer.