Tromsø is close enough to genuinely feel like two different cities depending on when you visit. Neither season is objectively "better," it depends entirely on what you're actually after.
Summer: endless light, mild weather
Summer in Tromsø is mild, usually 10 to 15°C, and bright, with the midnight sun lasting from around May 20 to July 22. The sun genuinely doesn't set, which takes some adjusting to (blackout curtains help). It's also festival season: the Midnight Sun Marathon in June runs under the midnight sun, Bukta Festival in July is a rock festival on the beach, and Rakettnatt in August is Northern Norway's biggest music festival. Expect windy, fast-changing conditions even in the middle of summer, this is still the Arctic.
Winter: polar night and the northern lights
Winter is cold and dark, with the polar night lasting from late November to mid-January, when the sun doesn't rise above the horizon at all. This is also exactly when the aurora season is in full swing, so if seeing the northern lights is your main goal, winter is non-negotiable. Snow, ice, and genuinely cold temperatures are part of the deal, pack in proper layers.
So which should you pick?
If the northern lights are the whole point of your trip, come between late August and mid-April, and understand winter (November through February) gives you the darkest skies and the most classic "Arctic" experience. If you'd rather hike, kayak, or just want daylight and milder weather, aim for June through August, and treat any aurora sighting as a bonus rather than the goal.
Planning around the seasons?
The full guide has a season-by-season packing list, festival dates, and tips for making the most of whichever window you pick.
Buy the guide (kr 180,-)Whichever season you choose, pack layers and check the forecast daily, Tromsø's weather changes faster than you'd expect, in both winter and summer.