The polar night in Tromsø, Norway

In winter, the sun in Tromsø stays below the horizon.

It does not come up at all for many weeks. This time is called the polar night. In summer, it is the other way around: the sun never sets!

Earth's axis is tilted. In winter, the north of the planet leans away from the sun, so places very far north get no sunrise at all for a while. In Norwegian this is called mørketid, the dark time.

In Tromsø, the polar night lasts from about 26 November to 17 January, so for about seven and a half weeks no part of the sun shows above the horizon (if the view is not blocked). The dates can shift by a day from year to year. In summer it flips: from about 18 May to 25 July, the sun stays up all day and night. This is the midnight sun.

NASA gives Earth's axial tilt as 23.4 degrees, the cause of the seasons. North of the Arctic Circle, the winter hemisphere's tilt away from the sun brings days when the sun never clears the horizon. Store norske leksikon (SNL) defines mørketid as the time when the sun's center (sometimes its upper rim) stays below a place's horizon for a whole day. Because the atmosphere bends sunlight, the southern limit at sea level is 67°8' N, not the Arctic Circle at 66°33'.

SNL's table gives Tromsø (69°42' N) mørketid from 26 November to 17 January, counting the upper rim of the sun and a free horizon, with dates varying by a day between years. Its midnight-sun table gives 18 May to 25 July. The tables assume a free horizon, so they do not take local mountains into account. Farther north the dark time grows: Longyearbyen, in Svalbard, has it from 26 October to 16 February.

The polar night is not black all day.

Around the middle of the day, the sky gets lighter for a few hours. Then it gets dark again.

Even when the sun does not rise, the sky does not stay black. Twilight is the in-between time when the sun is just below the horizon and the sky still glows with sunlight scattered by the air. In Norwegian, the dusk hour on clear evenings is often called blåtimen, the blue hour.

In Tromsø on the shortest day, the sun at midday is only a few degrees below the horizon. Researchers writing about Tromsø say that during the polar night it gets between 2 and 5 hours of twilight each day.

SNL describes twilight (tussmørke) in three stages, set by how far the sun's center is below the horizon: civil twilight ends at 6°, when you can still read by a west-facing window on a clear evening; nautical twilight ends at 12°; and astronomical twilight ends at 18°, when night begins. The glow comes from sunlight scattered by air molecules and dust in the part of the sky still outside Earth's shadow.

A simple calculation shows why Tromsø's polar night is not pitch-black: at the December solstice the sun's noon altitude is about 90° − 69.7° − 23.4° ≈ −3°, inside the civil-twilight band. This ignores refraction and the mountains, which change the exact light a person sees, so treat it as an estimate. Leibowitz and Vittersø (2020) describe the Tromsø area as getting no direct sunlight from mid-November to mid-January but 2 to 5 hours of civil twilight each day.

In the dark, cars may not see people walking.

So people in Norway are told to wear a shiny reflector. When car lights hit it, it glows bright.

With so many dark hours, walking to school or the shops means walking in the dark. Norway's road authority, Statens vegvesen, tells people to wear a reflector, a small shiny tag, so that drivers can see them sooner.

In a 2018 article it said that without a reflector, a driver using low beams first sees a person 25 to 30 meters away. With one, the driver can see them 140 meters away. It advised hanging the reflector at knee height, where it catches the most light from headlights.

The Norwegian Public Roads Administration (Statens vegvesen) gave these figures in October 2018 and notes the article may be outdated: on low beam, a pedestrian without a reflector is first noticed at 25-30 m; with a reflector, at 140 m; with high beam, visibility rises to 400 m. At 50 km/h, it said, a driver has about two seconds to see a walker without a reflector and about ten seconds with one. It recommended reflectors at knee height to catch the most headlight. It also advised using two reflectors, to be seen from both sides, and noted that approved reflectors are marked EN 13356.

These are national safety figures, not Tromsø measurements.

Some people think long, dark winters must feel gloomy.

But scientists asked people in the north of Norway and other places. People farther north tended to feel better about winter.

You might guess that weeks without sunrise would make everyone unhappy. Researchers from Stanford University and the University of Tromsø decided to ask. Between 16 January and 7 February 2015, they surveyed 238 people in Oslo in the south, in Troms county in the north, which includes Tromsø, and on the Arctic islands of Svalbard.

They measured each person's winter mindset: whether they saw winter as something to enjoy or something to put up with. People farther north tended to have a more positive winter mindset, and a positive mindset went along with feeling more satisfied with life. The study shows a link, not proof that one causes the other.

Kari Leibowitz (Stanford University) and Joar Vittersø (University of Tromsø) published 'Winter is coming: Wintertime mindset and wellbeing in Norway' in the International Journal of Wellbeing (2020). Using a Wintertime Mindset Scale with 238 respondents in southern Norway, northern Norway and Svalbard (randomly invited by letter in Oslo, Troms county and Svalbard, and surveyed between 16 January and 7 February 2015), they found that a positive wintertime mindset correlated with life satisfaction and positive emotions, that more northern residents, who face significantly more darkness and somewhat colder winters, held more positive mindsets, and that mindset statistically mediated the link between location and wellbeing.

The design is cross-sectional and correlational, so it cannot show cause. The authors call mindset a previously overlooked factor in seasonal wellbeing, especially where winter darkness is extreme.

Winters in Tromsø can bring lots of snow.

One spring, the snow was deeper than a grown-up is tall! The coldest day ever measured there was more than 100 years ago.

Tromsø can get deep snow. On 29 April 1997, the snow in Tromsø was 240 centimeters deep, taller than most grown-ups. Science Norway notes that this was not a national record: Norway's deepest snow, 585 centimeters, was measured on a mountain in 1918.

The average temperature in the municipality, across records since 1868, is about 3 °C, and the coldest temperature ever measured there is -22 °C, back in 1910.

Science Norway (January 2025) reports a snow depth of 240 cm in Tromsø on 29 April 1997 and notes it was not a record; Norway's record, 585 cm, was measured on a mountain near Ulvik in 1918. SNL gives the municipality's mean temperature as 2.92 °C over available records since 1868 and mean annual precipitation of 1,018 mm over the last 150 years; the highest temperature recorded, 30.4 °C, came at the Holt station in 2014, and the lowest, -22 °C, in 1910.

The photo from Fjellstua shows the town under snow with its lights on.