WINTER
During the Winter you will get some amazing scenery with snow capped peaks and powder white snow or you can marvel at the amazing Norther Lights (aurora borealis) in Tromso (weather permitting) the best time to experience this is September - April. You will also have the opportunity to do some fantastic trips during the winter months such as a dog sled rides across the crystal white landscape or snow mobile your way across! The weather can get as cold as -25 in places though so be prepared to take your thermals and wrap up!
SPRING
Some might say Spring would be the best time of year to go and I would have to say I may be inclined to agree. May - Mid June is when the scenery in Norway is at its most spectacular with trees and flowers waking into life. With the abundance of water due to the melting snow the waterfalls are always at their best cascading down. There is plenty of sunlight and the temperatures rise fairly nicely. There are also several public holidays in May, and the Norwegians make full use of them to celebrate springtime after a long winter.
You can also experince the land of the midnight sun June-July where you can sit up until the early hours and still feel like it is the middle of day...
SUMMER
Late June to early August is when the weather is warmest and the days are long and bright. Temperatures in July and August can reach 25°C - 30°C. At the same time there is hardly any humidity in the air so you can get some relaly beautiful weather. On the flip side the summer weather can be wet and changeable especially in Fjord Norway. If you want to experience the Land of the Midnight Sun you will have to travel to the northern part of the country in June - July.
AUTUMN
In the autumn the landscape is painted in golden colours very much like what you would find in Canada and New England. The temperature drops slowly through September, making for good berry and mushroom picking weather. During autumn the land areas lose more heat than the sea, and eventually the coastal areas have the highest temperatures. In September the outer part of the Oslofjord usually has the highest mean temperatures. Later in the autumn, the warmest areas are usually found on the coast of Rogaland and Hordaland.
So as you can see there really isn't a 'best' time to go as each season in Norway holds something a little bit special for you. With cruise lines such as Hurtigruten who specialise in Norway and Cruise and Maritime there are lots of choices and itineraries to choose from so if you are thinking about a cruise to Norway then hopefully this has helped in deciding for you when would be the best time for you to go.