The northern lights—also known as the aurora borealis—is a natural phenomenon that illuminates the night sky in northern regions of the Earth throughout the year. However, when it comes to seeing this brilliant light display for yourself, you'll have to visit a dimly-lit destination in the auroral zone, where the northern lights are likely to occur, preferably from September to April. The weather conditions on the sun and earth determine whether or not the aurora can be seen, as do the light pollution levels of where you're viewing it.
What Causes the Northern Lights
The aurora is caused by large numbers of electrons from the sun colliding with air particles along Earth's magnetic field. 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 are caused by these reactions reflecting onto the gases in Earth's atmosphere. It is most common to see green lights, though a reddish glow that appears like a dark sunrise is also sometimes visible.
Best Places to See the Aurora Borealis
While you might be able to see the northern lights from anywhere in the auroral zone, the aurora is almost always visible from locations beyond the Arctic Circle, which marks the 66th degree of latitude on the globe. The four largest populated areas above the Arctic Circle where you can visit to see the northern lights include Tromsø, Norway, and Murmansk, Norilsk, and Vorkuta in Russia.
However, you don't need to go above the Arctic Circle to see the lights and can visit other popular destinations like Iceland, Alaska, Northern Canada, Greenland, Norway Sweden, Finland, and Russia where the lights will still often be visible during the winter months.
Best Time to See the Aurora Borealis
Although the northern lights are constantly happening above the Earth on some level, it may be harder to see them from the ground at different times of the year. As a result, the best times to see the lights are when it's dark out longer, which is why places near and above the Arctic Circle, which get less light year-round, typically experience the best viewing season any time between September and late April.
The further south in you go, the shorter the aurora borealis season will be, meaning you'll likely only see the northern lights between mid-October and March in those regions.
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. 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.
Predicting Visibility of the Northern Lights
How often the northern lights are visible depends on where you are trying to see them. In locations nearer the Arctic Circle, like Tromsø and at the North Cape of Norway, you can see the northern lights every other clear night, if not even more frequently. On the other hand, you may only see them two or three times a month in more southern locations like central and southern Sweden.
To scientifically forecast the northern lights, you need to know the location where you will be watching them and the expected geomagnetic activity on the night of your trip, which is measured by a Kp index from 1 to 10. A higher Kp value in the forecast means the lights are more likely to be visible.
Geomagnetic activity is forecast year-round, but the northern lights generally cannot be seen May through September. Visibility also depends on local weather conditions and clouds and rain can obscure the lights even if there is high geomagnetic activity.