The seasons in Norway differ considerably depending on where in the country you plan to go - and whether you plan to stay below or above the tree line (around 700-900 masl.). At higher altitudes, such as Sognefjellet (1300-1400 masl.), the western part of Hardangervidda (1200-1600 masl.) and Jotunheimen (900-2400 masl.) the first snow often fall in the month of October, but the snow conditions may still be insufficient for skiing until December or January. The rugged topography of Norway is one of the main reasons for large local differences over short distances. The result may be that we have several meters of snow in the western mountain areas, while almost no snow cover in the eastern mountains, especially early in the winter season.
Winter (December - February)
Skiing conditions from November through January may be treacherous with unfrozen lakes and streams and the hours of daylight are few. In general we have more precipitation and warmer temperatures in the western part of Norway, while it is dryer and colder in the east. It may be very unstable snow conditions for backcountry skiing/ski touring the first months of winter, and we recommend less skilled skiers to avoid steep and remote terrain. It is a better option to either participate on a guided tour or stick to terrain below the treeline - or it may even be possible to go hiking in some of the forest areas in the lowlands of Southern Norway. Around the middle/end of February, many self-serviced cabins open for the season, and many of the staffed cabins also open for the Norwegian winter holidays in week 8 and 9.
Late winter/Spring (March - May)
In the mountains, the skiing season always last until the end of May - and some years it may be skiing conditions far into July. March and April are the top months for ski touring cabin to cabin in the mountains, and the peak of skiing activity is always the Easter holiday. Around the Easter holiday, DNT waymark the skiing routes between many cabins with tree branches in the snow, called "kvisting". These show the recommended route, but there are not groomed tracks in the mountains - wind and snowfall can often make the tracks disappear, so you need to know how to orient by map and compass.
Summer (June -August)
In summer the warmest areas are the southern part of Østlandet and the coastal areas of Sørlandet, where the temperature often can reach 20-30 °C. While in the mountains, you have to be prepared for temperatures dropping below zero degrees Celsius, and rain, hail and even wet snow occur during summer. The weather may change rapidly form +15C and sun to 0C with wet snow and thick fog.
Autumn (September - November)
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 has the highest mean temperatures in the country. The first snowfall is typically making it difficult to hike by foot during late October, and many of DNT Oslo's self-serviced mountain cabins also close in the period from 15th of October to around the 15th of February.