Clouds and clear skies: the real key to seeing the aurora

Clouds are the most common reason people miss the aurora, even in Northern Norway and even on nights with high Kp. The aurora forms around 100 kilometres above the ground, far above any cloud, so a thick cloud layer shuts it out completely. The single best thing you can do for your chances is to read the cloud forecast as carefully as the space weather, and to be willing to move to wherever the sky is clear.

Why clouds decide

The Norwegian Centre for Space Weather at UiT (the Arctic University of Norway) names the weather as the biggest obstacle to seeing the aurora. The northern coast has relatively mild winters, but also a lot of cloud. Many people therefore travel a little inland to escape it, even though that means colder nights.

The good news is that the sky does not have to be perfectly clear. The aurora can fill large parts of the sky, and a few gaps in the cloud may be enough. Scattered cloud can even look good in photos; see photographing the aurora with a camera.

Low, medium and high cloud

The Norwegian Meteorological Institute (MET Norway) splits cloud cover into three layers:

Total cloud cover is the percentage of the sky covered at any height. On Yr (Norway's main weather site, run by the broadcaster NRK and MET Norway), the "Andre varsler" (other forecasts) page for a place shows aurora activity, Kp and the split between high, medium and low cloud and fog, hour by hour. It is a good place to start.

Forecasts for the Nordic region come from a model with 2.5-kilometre resolution that is updated every hour, and for the Arctic from a similar model updated four times a day. Beyond two to three days, MET Norway relies on coarser global models. Tonight's cloud forecast is therefore far more reliable than next weekend's.

Nordlys i natt? counts an hour as clear enough when total cloud cover is below 40 percent, and as a possible near miss up to 70 percent if activity is close to what is needed. More in how Nordlys i natt? works.

Coast or inland?

In Norway, high mountains act as a wall against moist air from the sea. Lille norske leksikon (the children's edition of the national encyclopedia) describes how the coast gets a lot of rain while it is drier on the inland side of the mountains. For aurora hunting this means that inland areas and the heads of fjords on the lee side of the mountains often have better odds when the coast is clouded over.

A few weather stations show how big the difference can be. In a 2016 article on Yr, state meteorologist Magnus Ovhed gave annual precipitation of about 300 millimetres in Skibotn in Troms, 282 millimetres in Dividalen in Troms and 300 millimetres at Levajok in Finnmark. Longyearbyen on Svalbard had only about 190 millimetres. By comparison, parts of the west coast can get up to 3000 millimetres a year.

Low precipitation is not the same as a clear sky every night. But the numbers help explain why so many aurora trips from Tromsø head inland towards Skibotn and beyond, and why inland Finnmark has a reputation for clearer skies than the coast. See also the aurora in Tromsø and the aurora in Alta and Finnmark.

How to hunt for gaps in the cloud

• Compare several places. Check the hourly forecast where you are and for places one or two hours away. The difference between the coast and a sheltered fjord head can be large on the same evening.
• Look at the layers, not just the total. 60 percent thin high cloud is very different from 60 percent low cloud.
• Face north. Further south in Norway, the aurora usually sits low in the north. A clear sky to the south helps little if the northern horizon is blocked, and a forecast for one point says little about the direction you are looking in.
• Use webcams. Yr shows webcams near many places, useful for checking whether the forecast is right.
• Watch for fog. According to Lille norske leksikon, the mountains have the most fog, and fog inland is most common in autumn.
• Plan the drive back. From Skibotn, the E8 road climbs Skibotndalen towards Finland. Check road reports and weather warnings before you drive, and read safety and clothing.
• Decide early. New forecasts arrive regularly, but the weather can change quickly. Make up your mind about driving in good time.

The Moon

NOAA explains that a full moon makes the aurora look fainter without actually weakening it. The Norwegian Centre for Space Weather recommends checking when the Moon rises and sets. Around new moon the sky is darkest. At full moon you will still see strong aurora, but faint bands are more easily lost in the moonlight. Yr shows the Moon's phase, how much of it is lit and the dates of the next full and new moon for every place. For Tromsø on 18 October 2026, Yr listed the next full moon on 26 October and the next new moon on 9 November.

Light pollution

Street lighting and other lights send light up into the air, where it scatters and creates a bright glow over towns. Store norske leksikon notes that whiter LED lighting can make the problem worse. Even a small town can make faint aurora hard to see. Drive a few kilometres out, find a spot with an open view to the north, and turn off your headlights. Twilight matters too: Nordlys i natt? only counts hours when the Sun is at least 6 degrees below the horizon. More in the best time of night.

In short

• Check the cloud forecast hour by hour, and look at low, medium and high cloud separately.
• Inland areas and fjord heads behind the mountains are often clearer than the coast, but not always.
• Moonlight and city glow reduce what you see. Dark, clear and an open view north is the goal.
• Check tonight's verdict for your location for a combined read of cloud, darkness and Kp.