Norway is a sparsely populated country with a lot of wonderful nature: a very long coast line, lots of islands, deep fjords, a plethora of lakes and forests, and last but not least, mountains. All this provides plenty opportunities to swim or be in the sun with or without clothes.
Admittently, the weather in Norway is not as stable as further south, however, in return, we have long summer days - and the further north you get, the longer they are. So despite some occational clouds and rain, the southeast part of the country is very high on the European statistics on the number of hours of sunshine per day - in the summer.
If you would like to behave naturistic you have the following possibilities:
Visit one of the three naturist centers in Norway: Isefjær between Kristansand and Lillesand, Sjøhaug by Moss or Skovly by Halden. Visits for more than two days require membership in a naturist association affiliated with the International Naturist Federation INF/FNI.
Visit an official or unofficial naturist beach. Official beaches are established by the local authorities, whereas the unofficial ones are established through custom. The naturist beaches are public areas and can be visited by everyone.
Information about the naturist beaches and their location can be found in the Scandinavian Naturist Portal.
Visit a secluded beach at the coast, on an island or at a lake in the inland. The laws and regulations give you and everybody else free access on foot, by canoe or on bicycle to the Norwegian nature.
Recommended sites for the practise of "inofficial naturism" are the many small islands in the archpelagoes in southern Norway (a boat of some sort is recommended), several of the lakes in the south-west Norway and in the forests around Oslo (a canoe is a good help) and the mountains off the marked footpaths.