Northern Lights in Lapland

The three things that have to line up

The Northern Lights, or aurora borealis, are the most visible form of space weather: the effects of the solar wind and solar flares in the space around the Earth and in the upper atmosphere. They glow far above the weather, typically 80 to 500 km up. You see them only when three conditions hold at the same time.

Weather does not decide whether an aurora happens, only whether you can see it. The usual time is around midnight: the Finnish Meteorological Institute (FMI) gives 9 pm to 1 am local time as the strongest window, and Visit Finland gives 9 pm to 2 am.

The best places to see the Northern Lights

The honest answer starts with latitude. FMI explains that the Northern Lights form an oval band around the Earth’s geomagnetic poles, and that about 2,500 km from those poles the chance of seeing them is almost 100%. Finland sits on the southern rim of that oval, so the further north you go, the more often the sky shows them. In FMI’s words, the chance is best in the northernmost part of the country, in Lapland. That is why this site plans aurora trips in Finnish Lapland, and it is where our own checking is done.

Inside Lapland, north still beats south. Kilpisjärvi is in the top band. Levi, Ylläs and Saariselkä are in the middle one. Rovaniemi lies further south, between Oulu and those resorts, and FMI’s aurora pages give it no figure of its own. If you base yourself there, plan more evenings for the aurora to make up the difference. Wherever you stay, the spot matters as much as the town: FMI advises open, dark ground away from settlements, and says an open view to the northern horizon is essential.

Outside Finland, FMI names the latitudes where auroras can typically be seen: northern Fennoscandia, Svalbard, Iceland, northern Canada, Alaska and Siberia. Of those, we compare two with Finnish Lapland. The Norwegian coast around Tromsø is in the sections below and in Finland or Norway for the Northern Lights. Swedish Lapland, with Abisko and Kiruna, is in Finnish or Swedish Lapland. Iceland is on FMI’s list too, but this site does not cover it and we have not checked it, so we make no claim about it.

How many nights give you a fair chance

FMI’s figures in the table above are the place to start. Read them carefully. They count only the dark, cloud-free nights, so they are a ceiling, not your chance. Your real chance on a trip is lower by however many of your nights are cloudy, and nobody can tell you that when you book. We looked for an official figure for how many winter nights are clear in Rovaniemi and could not find one, so we will not turn this into a percentage.

The tourist boards count differently. Visit Finland says the lights appear on roughly 200 nights a year in northern Finland, and Visit Rovaniemi says around 150 nights a year in Finnish Lapland when conditions are favourable. Neither figure is the number of nights you will see them from one place.

What the arithmetic does show is simple: each evening you are there, dark and free, is one more chance for a clear sky and activity to coincide. So we plan aurora trips around the number of evenings first and the place second.

Our planning rule is at least four nights. Your arrival evening often goes to travel and unpacking, so four nights leaves you three full evenings. Three nights leaves two, and one cloudy spell can take both. This is planning judgement, not a statistic: four nights can still bring nothing, and a single night can bring a strong display.

• Keep your evenings free rather than booking a dinner or activity for each one.
• If you book a guided aurora trip, put it early in your stay, so a clouded-out night is not your last.
• Dress for standing still. FMI notes that the dark, cloudless nights you want are practically always cold in Finland.

Northern Lights inland or on the coast

The main alternative to inland Finnish Lapland is the Arctic Ocean coast of northern Norway, around Tromsø. Rovaniemi sits on the Arctic Circle; Visit Tromsø puts Tromsø about 350 km north of it, and FMI says the lights can be seen on that coast almost every night. The coast is also milder: Visit Tromsø gives an average winter temperature of about −4 °C, while at Rovaniemi airport the January average is −10.3 °C (FMI, 1991 to 2020).

Cloud is the catch on both sides of the border. One operator listed by Visit Tromsø says its tours follow no fixed route: it uses the live weather to search for clearer skies, and may drive more than 200 km or cross into Finland. We could not find an official comparison of how often the sky is clear on the coast and inland, so we do not claim that either is clearer.

The trade, then: the coast gives you milder nights and a more northerly position, sometimes with a long drive on a chase night. Inland Finland is colder, and in Rovaniemi Visit Rovaniemi lists viewing places a short walk from the city centre, though darker ground further out shows more.

The whole comparison, with getting there from the UK, is in Finland or Norway for the Northern Lights, and the one-town version in Tromsø or Rovaniemi. If you are weighing a ship on the Norwegian coast against a week on land, read a Northern Lights cruise or Lapland.

When the Northern Lights season runs

The season runs from late August to early April, the months when the nights are dark enough. Visit Rovaniemi says the lights can still appear until around mid-April, with the chance falling as the evenings get lighter. From mid-April to late August the nights are too light.

FMI names February to March and September to October as the strongest months, and its page on auroras in Finland adds that March and early April are the strongest time in the north. FMI’s statistics show auroras slightly more frequent in spring and autumn than in midwinter, and NOAA also points to the weeks around the spring and autumn equinoxes.

December and January give you the longest nights, which means more hours to watch, not more activity. Each choice trades something:

• September and October: aurora nights without deep cold, and calm lakes that can reflect the lights, but no snow to rely on. See Lapland in September and Lapland in October.
• February and March: strong months with snow on the ground and longer days, but cold nights. See Lapland in February and Lapland in March.
• December: the longest darkness and the Christmas crowds. See Lapland in December.

For the whole year, month by month, see when to go.

What causes the Northern Lights

The source is the Sun. FMI explains that particles leave the Sun all the time, in a stream called the solar wind, and some of them end up in the Earth’s atmosphere. There, electrons plunging down along the Earth’s magnetic field collide with oxygen atoms and nitrogen molecules in the ionosphere. Each collision lifts the atom or molecule briefly into a higher energy state, and as it falls back the energy is released as light. FMI compares the process to a fluorescent tube.

The colour depends on what is hit: oxygen gives green and red light, nitrogen a bluish one. FMI places the light itself at about 100 to 200 km above the ground; NOAA’s wider range for where the aurora forms is the one given at the top of this page.

The oval of light is there all the time, over both hemispheres. FMI notes that daylight hides it, except in the darkest polar-night areas in winter, and that most of it lies over uninhabited areas. The time of year matters too: around the spring and autumn equinoxes, FMI says, the Earth’s position in the solar wind is at its most favourable for the wind’s energy to pass into the Earth’s magnetic field, which is one reason the equinox months appear in the season above.

Can you see the Northern Lights with the naked eye?

Yes. FMI says you see faint aurora light best with the naked eye when you stand under a clear, dark sky, away from the lights of towns and traffic. But the photographs you have seen are not quite what you will see. NOAA says modern digital cameras are often more sensitive than the human eye, and can record an aurora and its colours when it is too dim for you to see. In dim light the eye picks out brightness before colour, which is why people often describe a faint aurora as pale white. Only a fairly bright display shows its true green or red to the naked eye.

The most common colour is a pale green, and red is less common. FMI lists green, red and violet as typical colours, and says the aurora looks paler to the eye than in photographs because the eye separates colours poorly in dim light.

Two practical points from FMI. Give your eyes time: full night vision takes tens of minutes. And for photographs, you need a camera with full manual controls. The settings, and what a phone can do, are in how to photograph the Northern Lights.

The Northern Lights forecast, and how to read it

No forecast can tell you on booking day whether a given night will have an aurora. FMI says auroras cannot be reliably predicted, and estimates only the chance for the coming nights. NOAA says an accurate forecast is possible only a short time ahead, measured in minutes, from measurements of the solar wind before it reaches the Earth. Use these on the day, not to choose your dates.

FMI sets out what can be forecast, and how far ahead. A single display, it says, is a random event that can never be forecast exactly; only the amount of activity and how visible it is likely to be can be estimated.

• Years ahead: the Sun’s activity rises and falls in cycles of about 11 years.
• Weeks ahead: seen from the Earth, the Sun turns about once every 27 days, and large holes in its corona can keep much the same shape for several turns.
• One to three days ahead: images of the Sun show coronal holes and mass ejections heading for the Earth. The solar wind typically takes about three days to arrive, the most violent ejections less than a day, and FMI puts the uncertainty in their arrival time at about half a day either way. The bigger the display on its way, the shorter the warning.
• About an hour ahead: satellites upstream of the Earth, at a point called L1, measure the solar wind as it passes, including the direction of its magnetic field. Ordinary solar wind takes about an hour from there to the Earth.
• Now: FMI follows small changes in the magnetic field at about ten stations across Finland. It calls this real-time monitoring, not a forecast, because the disturbances happen at about the same time as the aurora you can see.

Reading FMI’s aurora and space weather page

The value FMI shows is the R-index, which measures how fast the magnetic field changes within a 10-minute interval. A bar chart shows the last 24 hours, and a map shows the latest reading at each station.

• Yellow bars, and yellow squares on the map: the lower threshold is crossed. Auroras are possible, but usually dim.
• Red bars, and red rhombuses on the map: the upper threshold is exceeded, and FMI says it is very likely that auroras can be seen.

FMI’s own advice for using it: if the station nearest to where you are has measured strong disturbances in the last hour, it is a good moment to go out. All of it still assumes a dark, clear sky, so check the cloud forecast too.

• FMI auroras and space weather: the chance of auroras in Finland, from FMI’s own magnetometer stations.
• Space weather in Finland: FMI’s live geomagnetic activity, an aurora probability map, and an all-sky camera in Muonio.
• NOAA 30-minute aurora forecast: the short-term view of where the aurora is and how bright.
• FMI weather forecast for Rovaniemi: its weather symbols show whether clear or cloudy skies are expected, which matters as much as activity.