Best time to see the northern lights in Great Falls, United States
Updated • 21:02 UTC
Great Falls gets the aurora on 2.1 clear nights in a typical year. September is the best month at 0.38 of them, and nights were counted at Kp 6 or higher, which the planetary index last reached on 4 July 2026.
Typical-year figures: a 1996–2026 planetary Kp record crossed with a 2001–2020 cloud normal. They describe a normal year, not tonight — the live Great Falls forecast shows the actual cloud, moon and darkness right now. Check tonight's forecast for Great Falls →
🌌 Clear nights a year
2.1
Fair — 2.1 clear aurora nights in a typical year Compare with United States
🌟 Best Month
September
0.38 clear nights in a typical year
🌙 Peak Hours
23:00-01:00
Magnetic midnight
⚡ Required Kp
Kp 6.0–8.0
Served for the live forecast; nights counted at Kp 6, last reached 4 July 2026
🧭 Auroral oval (model)
58.2° above the northern horizon
Model estimate at Kp 6
Month by month in Great Falls
Astronomical darkness, the nights on which planetary Kp reached Kp 6 inside that darkness, the local cloud normal, and what the cloud leaves of the count.
| Month | Astronomical darkness | Opportunity nights | Mean cloud | Clear opportunity nights | Moon-free |
|---|---|---|---|---|---|
| January | 11.4h | 0.33 | 70.4% | 52.6% | |
| February | 10.24h | 0.2 | 69.7% | 53% | |
| March | 8.56h | 0.46 | 71.3% | 53.8% | |
| April | 6.44h | 0.59 | 69.3% | 55.1% | |
| May | 3.97h | 0.46 | 65.4% | 52.4% | |
| June | 2.08h | 0.23 | 57.3% | 51.3% | |
| July | 3.24h | 0.2 | 38.3% | 53.1% | |
| August | 5.74h | 0.33 | 44% | 55.8% | |
| September | 7.95h | 0.78 | 51.9% | 56% | |
| October | 9.77h | 0.81 | 63.2% | 54.6% | |
| November | 11.13h | 0.91 | 69% | 54% | |
| December | 11.77h | 0.23 | 69.4% | 54.4% |
Opportunity nights are the whole 1996–2026 record. In the current solar cycle alone (since 2023), September has averaged 1.09 rather than 0.78.
- September: 7.95h of astronomical darkness a night
- September: 0.78 nights reach the Kp threshold inside that darkness
- September: 51.9% mean cloud leaves 0.38 of them clear
- September: 56% of those nights are moon-free
Similar timing: Saint George , Mažeikiai , Jelgava
Higher-odds destinations: Fairbanks , Yellowknife , Tromsø
Nearby in Montana
The strongest tracked locations in the same region, by clear aurora nights a year.
How these numbers were made
- Evaluated at
- Great Falls, 47.4941° N 111.3008° W — darkness and cloud are properties of that point, not of a region.
- Darkness
- Sun at or below 18° under the horizon (astronomical twilight), sampled every 10 minutes across every year of the Kp record and averaged per night of each month rather than on one representative day.
- Geomagnetic record
- GFZ Potsdam planetary Kp index, 3-hourly, 1996–2026 — 89,662 intervals, licensed CC BY 4.0.
- Cloud
- NASA POWER 20-year monthly climatology (2001–2020), parameter CLOUD_AMT. A monthly mean, not a forecast.
- Moon
- A night counts as moon-free below 35% lunar illumination while the moon is up.
- Auroral oval
- NOAA auroral-oval model, equatorward boundary near magnetic latitude 67 − 2 × Kp. A model estimate shown beside the measured record; it never replaces it.
- Clear opportunity nights
- Nights on which at least one 3-hour Kp interval falls inside local astronomical darkness and reaches the count threshold, scaled by one minus the monthly mean cloud amount.
- Kp threshold
- Nights were counted at Kp 6 or higher, the same threshold the live forecast serves.
- Dataset version
- Version 2026-09-07, computed offline from the closed record — the page is regenerated, not forecast.
Kp record: GFZ Potsdam (CC BY 4.0). Cloud normal: NASA POWER. How the live forecast is built: methodology page.
Frequently Asked Questions
When can you see the northern lights in Great Falls?
September is the best month, with 0.38 clear nights in a typical year out of 2.1 across the whole year. Every month of the year carries some chance.
What Kp is needed to see the aurora from Great Falls?
Great Falls needs Kp 6 or higher for aurora low on the northern horizon, Kp 7 for a noticeable display and Kp 8 for a bright one. The NOAA auroral-oval model puts the edge of the oval about 58.2° above the northern horizon at Great Falls at Kp 6. That is a model estimate, separate from the measured Kp record.
Has the aurora ever been visible from Great Falls?
Yes. In the 1996–2026 planetary Kp record the index reached Kp 6, the threshold these nights were counted at for Great Falls, most recently on 4 July 2026. The Kp 7 needed for a noticeable display was last reached on 21 January 2026. Whether anyone saw it also depended on the cloud, moonlight and darkness of that night, which the Kp record does not carry.
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