The Northern Lights (also called Aurora Borealis) stem from when large numbers of electrons, originating from the sun, stream in toward the Earth along its magnetic field and collide with air particles. The air then lights up in a similar manner to what happens in a fluorescent light tube, around 60 miles (100 kilometers) above the earth's surface. The resulting colors of the Northern Lights reflect gases we find up there. It is most common to see green lights, though a reddish glow that appears like a dark sunrise is also sometimes visible, specifically in Scandinavia.
The lit-up skies are also referred to as "polar aurora" and "aurora polaris".
The weather conditions on the sun and earth determine whether or not the aurora can be seen. When visible, the lights can be seen up to 260 miles (400 kilometers) away on the horizon, due to the curvature of the earth.
Best Places to See the Aurora Borealis
To see this phenomenon, visit the auroral zone (or any location beyond the Arctic Circle) where the Northern Lights occur. Prime locations are the coasts of the Norwegian counties of Tromsø, Norway (near the North Cape), and Reykjavik, Iceland, even at the minimal level of northern lights activity. Out of all Nordic destinations, these places provide you with an optimal chance of seeing the famous phenomenon. In addition, both destinations provide a long, dark viewing season since they are located beyond the Arctic Circle (especially during polar nights, when there is no sunlight).
If you don't want to go that far north, the next-best location to see the northern lights is the region between the Finnish town Rovaniemi and the Norwegian town Bodø, just along the edge of the arctic circle. From here, you can still see the northern lights on a regular basis.
Locations as far south as Umeå, Sweden, and Trondheim, Norway, are not as reliable but a good alternative for the average traveler. These places require only slightly stronger northern lights geomagnetic activity to enjoy the natural phenomenon up close, so you won't see them as often.
The Northern Lights can be viewed from other northern locations as well, but the northern half of Norway and Sweden, as well as all of Iceland, are famous for having "the best seats" for viewing the Aurora Borealis.
Best Time to See the Aurora Borealis
We associate the Aurora Borealis with dark, cold, winter nights, although this natural phenomenon happens all the time (it's just harder to see in lighter conditions).
The best time to see the northern lights from anywhere around or above the Arctic Circle (which lies near the towns of Rovaniemi, Finland, and Bodø, Norway) is anytime between September and late April. You'll experience long winter nights here.
The further south in Scandinavia you go, the shorter the Aurora Borealis season will be, partly because there is more light in the months before and after winter. Between mid-October and March is the best time to see the northern lights in that region.
The optimal time of night for the northern lights is 11 p.m. to 2 a.m. Keep in mind that most visitors head out to begin their watch around 10 p.m. and conclude their night around 4 a.m. since the northern lights can be hard to predict (just like the weather in Scandinavia).
If you do not see the northern lights as expected even if the timing is right, locals recommend to simply wait for one to two hours. Nature tends to reward the most patient.
How Often Are They Visible
This depends on your location. In Norway's city of Tromso (Tromsø) and at the North Cape (Nordkapp), you can see the Northern Lights every other clear night, if not even more frequently. The same goes for locations further north.
Toward the south (e.g. central/south Sweden), it is harder to see the Aurora Borealis, and it may only occur 2 to 3 times a month.
How to Forecast the Likelihood of Northern Lights in a Specific Location
To forecast the northern lights, you need to know the location where you will be watching them. The forecast of the northern lights measures the expected geomagnetic activity on the so-called Kp index (1 to 10).
Here are some tips to help you forecast:
- Check your travel dates in the official NOAA Space Weather Outlook, which is always predicted for the next 27 days.
- Get the Kp number listed for the date you're interested in. The higher the Kp value in the forecast is, the farther south the northern lights will be visible.
- Compare the number you find with your location to determine if the Northern Lights will be visible:
- Northern lights predictions for locations like Tromsø and Reykjavik show the northern lights on the horizon even at 0 Kp from autumn to spring. At least 1 to 2 Kp (and higher) will guarantee that the northern lights are directly overhead at these locations.
- Rovaniemi, Finland, also only needs a Kp index of 1 for visibility of the northern lights on the northern horizon.
- As far south as Umeå and Trondheim, you'll need at least 2 Kp to predict seeing the lights on the horizon, or a Kp value of 4 to enjoy them overhead.
- And when you are down in areas around the Scandinavian capitals Oslo, Stockholm, and Helsinki, the Kp index has to be at least 4 for northern lights visibility on the northern horizon or 6 for the northern lights to take place directly overhead.
- In comparison, central Europe requires 8 to 9 Kp (very high auroral activity) to see the northern lights at all.
Remember: While activity is forecast year-round, the northern lights generally cannot be seen May through September. The visibility of the northern lights also depends on local weather conditions. Cloud cover will hide the northern lights even if the prediction points to a likely occurrence.