The best period is March, isnt it?
Depends on what you're after. Snow is an uncertain project, often just old snow waiting to melt is left, and the threes and ground has not yet become green, but we Norwegians love March because it gets so much lighter then - it's the month with most gain in daylight. Also it tends to get warmer, though it can still be cold.
August is my favourite month. I don't think our friend Kalle's forum name is chosen randomly. He comes from as far North as I do.