The Midnight Sun occurs from about 18 May to 26 July, although the mountains in the north block the view of the midnight sun for a few days, meaning that one can see the sun from about 21 May to 21 July. Owing to Tromsø’s high latitude, twilight is long, meaning there is no real darkness between late April and mid-August.
The sun remains below the horizon during the Polar Night from about 26 November to 15 January, but owing to the mountains the sun is not visible from 21 November to 21 January. The return of the sun is an occasion for celebration. However, because of the twilight, there is some daylight for a couple of hours even around midwinter, often with beautiful bluish light. The nights shorten quickly, and by 21 February the sun is above the horizon from 7:45 am to 4:10 pm, and 1 April from 5:50 am to 7:50 pm (daylight saving time).
The combination of snow cover and sunshine often creates intense light conditions from late February until the snow melts in the lowland (usually late April), and sunglasses are essential when skiing. Because of these diametrically different light conditions in winter, Norwegians often divide it into two seasons: Mørketid (Polar Night) and Seinvinter (late winter).
Tromsø is in the middle of the Aurora Borealis (Northern Lights) zone, and is in fact one of the best places in the world to observe this phenomenon. Because of the planet’s rotation, Tromsø moves into the aurora zone around 6 pm, and moves out again around midnight. As it is light round the clock in the summer, no aurora is visible between late April and mid-August.