Climate and light
Svalbard's latitude in the high Arctic is denoted both by its climate and by the prevalent conditions of light. The mean annual temperature is four degree below zero (Centigrade), and life takes its cues from the midnight sun and the polar night.
Although the average temperature is below the freezing point, Svalbard has a relatively clement climate compared to other areas at the same latitude. In January, the mean temperature is 16 degrees below zero; in July it is plus 6 degrees. If you would like to know the present temperature and wind conditions in Svalbard, you can enter the University Centre in Svalbard's (UNIS) automatic weather station outside Longyearbyen, here.
There are considerable climatic variations throughout the archipelago. The west coast of Spitsbergen - the largest of the islands - is the warmest and most humid part, where the comparatively high temperatures stem from warm currents of air from the south. Moreover, the Gulf Stream carries warm seawater along the west coast all year round.
The weather in Svalbard is very unstable. Basically, this is due to the encounter between significant amounts of water and warm air transported from the south and the cold water and air from the Polar regions. Stark temperature contrasts and lots of wind are the result. However, annual precipitation does not exceed an average of 190 mm. Hence Svalbard is commonly characterised as an Arctic desert.
Conditions of Light
The midnight sun and the polar night charaterise much of the year. In Longyearbyen, the midnight sun lasts from 20 April till 23 August. In mid-summer, the sun is 35 degrees over the horizon during the day, 11 degrees at night.
On the other hand, dusk and polar night last several months. Polar night means that it is absolutely dark: by definition, the sun is at least 6 degrees below the horizon. In Longyearbyen, the period of polar night lasts from 11 November till 30 January. On a clear day, however, the sky is often illuminated by flares of northern lights.