The climate of Tromsø is subarctic, with very cold winters and cool summers.
The city is located on the northern Norwegian coast, in an area of fjords and islands. Since we are at the 69th parallel, therefore north of the Polar Circle, the sun does not rise (polar night) from November 28th to January 14th, while it does not set (midnight sun) from May 19th to July 26th. The white nights occur as early as April 12th and until September 1st.
The average temperature of the coldest month (February) is of -3.7 °C (25 °F), that of the warmest month (July) is of 12.4 °C (54 °F). The temperature dropped to -20 °C (-4 °F) in February 1985, while it reached 29 °C (84 °F) in July 2018. Here are the average temperatures.
Tromso - Average temperatures
Min (°C)-6-6-5-2269851-3-5
Max (°C)-1-104813161410510
Min (°F)212123283643484641342723
Max (°F)303032394655615750413432

Precipitation amounts to 1,080 millimeters (42.5 inches) per year: so, it is at an intermediate level. It ranges from 55 mm (2.2 in) in the driest months (May, June) to 135 mm (5.3 in) in the wettest (October). Here is the average precipitation.
Tromso - Average precipitation

On average, there are around 1,265 sunshine hours per year. The sun is not seen very often even in summer: in June, the sunniest month, the sun shines on average for 7 hours and a half per day, which, compared to the 24 hours available, it's about 30% of the time. Here are the average sunshine hours per day.
Tromso - Sunshine

The sea temperature ranges between 5 °C (41 °F) and 12 °C (54 °F). So, it is cold all year round. Here are the average sea temperatures.
Tromso - Sea temperature
Temp (°C)555568101110876
Temp (°F)414141414346505250464543


Best Time

The best time to visit Tromsø is the summer, from June to August, since it is the mildest season. However, you must take into account cloudy skies, some rain and a bit of cold at night.