Can you see the northern lights in Trondheim in September?

On dark, clear nights with enough activity. 30 of 30 nights at Trondheim have civil darkness, and 83% of past September days reached Kp 2.

How dark is Trondheim in September?

Trondheim averages 9.3 hours of civil night a night in September 2027, from 7 h 39 min on the 1st to 10 h 52 min on the last night.

How cloudy is Trondheim in September?

NASA POWER's 2001 to 2020 climatology gives Trondheim's 1 degree cell 78% mean cloud in September, against 80% for the whole year. It is an all-hours average, not a forecast.

What is the best night in September 2027 for aurora in Trondheim?

By darkness and moon alone, Sep 1, with 4 h of moon-free darkness inside 10 PM to 2 AM at Trondheim. Activity on that date will only be known hours ahead.

Is September or October better in Trondheim?

By civil night times the clear share, September scores 2.0 hours at Trondheim and October 2.5. October comes out ahead.

Trondheim · September 2027

Northern lights in Trondheim in September 2027

Answer

September gives Trondheim 9.3 hours of civil night on the 15th, the 7th darkest of its 12 months, under 78% mean cloud. 83% of September days since 1996 reached Kp 2, enough for the oval edge to reach Trondheim.

9.3 h

civil night, average night

SunCalc for 63.43, 10.40; NASA POWER; GFZ Kp

September against the rest of the year

2.7

2.4

1.9

1.5

0.4

0.0

1.3

2.0

2.5

2.7

3.2

September cloud at Trondheim averages 78% in NASA POWER's 2001 to 2020 record, 2 points clearer than its yearly mean. August is Trondheim's clearest month at 76%. By civil night times clear sky, September scores 2.0 hours at Trondheim, 6th of 12. Stjørdalshalsen, 27 km away, averages the same 78%.

Civil night at Trondheim starts September at 7 h 39 min and reaches 10 h 52 min by September 30 as the nights lengthen by 3.2 hours. SWPC's 10 PM to 2 AM window is fully dark on every night. True astronomical darkness, the sun 18 degrees down, lasts 4.8 hours on the 15th.

September night by night

Full moon comes first, on Sep 16, then the new moon on Sep 30, in Europe/Oslo dates. Trondheim gets 142 hours of civil night with the moon below the horizon across the month. The best of them for moon-free darkness inside 10 PM to 2 AM: Sep 1 (4 h), Sep 2 (4 h), Sep 3 (4 h).

1
2% lit
7.7 h
2
7% lit
7.8 h
3
14% lit
7.9 h
4
22% lit
8.0 h
5
32% lit
8.1 h
6
42% lit
8.2 h
7
52% lit
8.3 h
8
61% lit
8.5 h
9
70% lit
8.1 h
10
79% lit
6.0 h
11
86% lit
4.3 h
12
92% lit
2.8 h
13
96% lit
1.3 h
14
99% lit
0.0 h
15
100% lit
0.0 h
16
99% lit
0.0 h
Full
17
96% lit
0.0 h
18
91% lit
0.0 h
19
85% lit
0.0 h
20
76% lit
0.0 h
21
67% lit
0.0 h
22
56% lit
0.0 h
23
45% lit
0.4 h
24
33% lit
2.6 h
25
23% lit
4.7 h
26
14% lit
6.8 h
27
7% lit
8.7 h
28
2% lit
10.6 h
29
0% lit
10.8 h
30
1% lit
10.9 h
New

Each cell is the night that starts on that date. Hours are civil-dark time with the moon below the horizon; the green rule scales with them. Green outline: new moon. Bone outline: full moon.

Activity in past Septembers

Trondheim needs Kp 2 for the average oval edge to sit overhead. 745 of the 900 September days from 1996 to 2025 (83%) reached it in the GFZ Potsdam record, one of the three most active months for that level; storm days with Kp 5 or more made up 14%. Trondheim sits at 63.0 degrees geomagnetic, inside SWPC's 60 to 75 degree band, where aurora can be seen on more than half of all nights. No storm is needed: by SWPC's rule the average oval edge is overhead at Kp 2.

September across Norway

Trondheim ranks 12th in Norway for civil night on September 15, behind Kristiansand at 9.8 hours. Coming from August (5.5 hours at Trondheim), September adds darkness, and the nights keep growing into October (12.4 hours on the 15th). The September equinox falls on September 23, 07:56 Trondheim time, inside the weeks SWPC links with larger storms.

Civil night on September 15 and September cloud, month-page towns in Norway
Town	Civil night	Cloud
Kristiansand	9.8 h	74%
Stavanger	9.7 h	79%
Haugesund	9.7 h	78%
Oslo	9.6 h	73%
Bergen	9.6 h	79%
Drammen	9.6 h	73%
Hamar	9.5 h	70%
Lillehammer	9.5 h	74%
Gjøvik	9.5 h	70%
Ålesund	9.4 h	82%
Molde	9.4 h	82%
Trondheim	9.3 h	78%

Darkness and moon, every night

Trondheim, September 2027: each night from local noon to the next noon
Night	Civil	Astronomical	Moon-free dark	Moon-free, 10 PM to 2 AM	Moon lit
Wed Sep 1	7 h 39 min	7 min	7 h 39 min	4 h	2%
Thu Sep 2	7 h 46 min	1 h 16 min	7 h 46 min	4 h	7%
Fri Sep 3	7 h 53 min	1 h 47 min	7 h 53 min	4 h	14%
Sat Sep 4	8 h	2 h 12 min	8 h	4 h	22%
Sun Sep 5	8 h 7 min	2 h 32 min	8 h 7 min	4 h	32%
Mon Sep 6	8 h 14 min	2 h 50 min	8 h 14 min	4 h	42%
Tue Sep 7	8 h 21 min	3 h 7 min	8 h 21 min	4 h	52%
Wed Sep 8	8 h 28 min	3 h 22 min	8 h 28 min	4 h	61%
Thu Sep 9	8 h 35 min	3 h 36 min	8 h 8 min	4 h	70%
Fri Sep 10	8 h 42 min	3 h 50 min	6 h 3 min	2 h 26 min	79%
Sat Sep 11	8 h 49 min	4 h 3 min	4 h 20 min	40 min	86%
Sun Sep 12	8 h 55 min	4 h 15 min	2 h 45 min	0 min	92%
Mon Sep 13	9 h 2 min	4 h 26 min	1 h 15 min	0 min	96%
Tue Sep 14	9 h 9 min	4 h 38 min	0 min	0 min	99%
Wed Sep 15	9 h 15 min	4 h 49 min	0 min	0 min	100%
Thu Sep 16	9 h 22 min	4 h 59 min	0 min	0 min	99%
Fri Sep 17	9 h 29 min	5 h 9 min	0 min	0 min	96%
Sat Sep 18	9 h 35 min	5 h 19 min	0 min	0 min	91%
Sun Sep 19	9 h 42 min	5 h 29 min	0 min	0 min	85%
Mon Sep 20	9 h 48 min	5 h 38 min	0 min	0 min	76%
Tue Sep 21	9 h 55 min	5 h 47 min	0 min	0 min	67%
Wed Sep 22	10 h 1 min	5 h 56 min	0 min	0 min	56%
Thu Sep 23	10 h 7 min	6 h 5 min	22 min	0 min	45%
Fri Sep 24	10 h 14 min	6 h 14 min	2 h 35 min	39 min	33%
Sat Sep 25	10 h 20 min	6 h 22 min	4 h 43 min	2 h 44 min	23%
Sun Sep 26	10 h 27 min	6 h 30 min	6 h 46 min	4 h	14%
Mon Sep 27	10 h 33 min	6 h 39 min	8 h 43 min	4 h	7%
Tue Sep 28	10 h 39 min	6 h 47 min	10 h 36 min	4 h	2%
Wed Sep 29	10 h 46 min	6 h 54 min	10 h 46 min	4 h	0%
Thu Sep 30	10 h 52 min	7 h 2 min	10 h 52 min	4 h	1%

Moon lit: SunCalc illuminated fraction at the middle of the 10 PM to 2 AM window.

Questions

Can you see the northern lights in Trondheim in September?: On dark, clear nights with enough activity. 30 of 30 nights at Trondheim have civil darkness, and 83% of past September days reached Kp 2.
How dark is Trondheim in September?: Trondheim averages 9.3 hours of civil night a night in September 2027, from 7 h 39 min on the 1st to 10 h 52 min on the last night.
How cloudy is Trondheim in September?: NASA POWER's 2001 to 2020 climatology gives Trondheim's 1 degree cell 78% mean cloud in September, against 80% for the whole year. It is an all-hours average, not a forecast.
What is the best night in September 2027 for aurora in Trondheim?: By darkness and moon alone, Sep 1, with 4 h of moon-free darkness inside 10 PM to 2 AM at Trondheim. Activity on that date will only be known hours ahead.
Is September or October better in Trondheim?: By civil night times the clear share, September scores 2.0 hours at Trondheim and October 2.5. October comes out ahead.

Sources and verification

SunCalchttps://github.com/mourner/suncalc
NASA POWER climatologyhttps://power.larc.nasa.gov/docs/services/api/temporal/climatology/
GFZ Potsdam Kp indexhttps://kp.gfz.de/en/data
NOAA SWPC, Tips on viewing the aurorahttps://www.spaceweather.gov/content/tips-viewing-aurora

Quoted figures last checked against their sources on 2026-09-30; next review 2026-12-31. Computed figures come from SunCalc and the IGRF-14 dipole as described in the methodology. Every quote is listed in the sources ledger.