Northern lights in Alta in September
71%
of 4-night stays in September saw the northern lights at least once, by our estimate. On any one night the chance was 26%. September is one of the weaker months in Alta; January (88%) was much better.
How long to stay in September
Chance of at least one good night, by length of stay, Alta in September, 2015–2025. 5 nights got you to about 3 in 4.
In a typical September, the longest run of nights without a single clear, dark hour was 7 nights. A stay shorter than that can fall entirely into one cloudy spell.
Week by week in September (4-night stay)
- 2 Sep – 8 Sep71%
- 9 Sep – 15 Sep70%
- 16 Sep – 22 Sep70%
- 23 Sep – 29 Sep71%
September in Alta, year by year
Good nights in September, each year 2015–2025. The typical September had 7 good nights; the worst, 2019, had 5 and the best, 2024, had 12. 2023–2025, around the solar maximum, averaged 9 against 7 before.
A good night = at least one hour that was dark (sun below −12°), mostly clear (NASA POWER cloud data, calibrated on FMI weather stations) and had a Kp index at or above the Kp 0.9 that Alta needs (GFZ Potsdam). These are estimates, not sightings. How it works
Other destinations in September
Alta ranks 3rd of 21 popular aurora destinations for September (4-night stays, 2015–2025).
Yellowknife
94%Churchill
92%Lofoten
69%Kilpisjärvi
67%Abisko
65%Tromsø
63%Aurora tours in Alta in September
A guide with a car can drive to wherever the clouds break. With cloudy spells of 7 nights in a typical September, that matters here. Booking for your first night leaves the rest of the stay to try again if it's cloudy.
Alta in September: questions
September is one of the weaker months in Alta; January (88%) was much better. In 2015–2025, 71% of 4-night stays in September saw the northern lights at least once, and an average September had 8 good nights (clear, dark and with auroras strong enough) out of 30. These are estimates from NASA cloud records and the Kp index, not sightings.
2 nights gave 45%, 4 nights gave 71%, 7 nights gave 89% odds of at least one good night in September (2015–2025). For about 3-in-4 odds, plan 5 nights or more. In a typical September, the longest run of nights without a single clear, dark hour was 7 nights. A stay shorter than that can fall entirely into one cloudy spell.
About 5.6 hours a night with the sun more than 12° below the horizon, which is dark enough for faint auroras. Of those, 1.2 hours a night were mostly clear on average, and 9 nights in an average September had at least one clear, dark hour.
Auroras can appear any time it's dark, but activity usually peaks around midnight, roughly 22:00 to 02:00. With about 5.6 hours of darkness a night in September, start looking as soon as it's dark and stay out past midnight if you can. The live forecast shows tonight's best hour.