March - July is the best time to visit Northern Europe
Weather is agreeable during this time. There are many festivals that take place during these months. Although, hotel prices could be a bit steep.
The flowers are in full bloom and the trees start bearing fruit. The wildlife is easily spotted making it a good time to spend some time with nature while enjoying the natura beauty of this region. The weather could be slightly chilly at night with occasional rain.
There is a lot of greenery while trees are ornated with ripe fruits. Days are warms and at times hot. However, temperatures usually don't skyrocket. Many festivals take place during this time.
This is the harvest season but at the same time leaves start to change colour and fall. At the beginning the weather is warm but with time it starts becoming chilly. It's best to carry a light sweater.
Winters are very cold in this region. Additionally, it also rains during this time. However, there are plenty indoor activities and museums that you can visit. It is an ideal time to visit if you plan on induldging in winter sports.