Can you see the northern lights in Reykjavík in September?

On dark, clear nights with enough activity. 30 of 30 nights at Reykjavík have civil darkness, and 14% of past September days reached Kp 5.

How dark is Reykjavík in September?

Reykjavík averages 9.2 hours of civil night a night in September 2027, from 7 h 31 min on the 1st to 10 h 51 min on the last night.

How cloudy is Reykjavík in September?

NASA POWER's 2001 to 2020 climatology gives Reykjavík's 1 degree cell 80% mean cloud in September, against 79% for the whole year. It is an all-hours average, not a forecast.

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

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

Is September or October better in Reykjavík?

By civil night times the clear share, September scores 1.8 hours at Reykjavík and October 2.7. October comes out ahead.

Reykjavík · September 2027

Northern lights in Reykjavík in September 2027

Answer

September gives Reykjavík 9.2 hours of civil night on the 15th, the 7th darkest of its 12 months, under 80% mean cloud. 14% of September days since 1996 reached storm level, Kp 5.

9.2 h

civil night, average night

SunCalc for 64.14, -21.90; NASA POWER; GFZ Kp

September against the rest of the year

3.5

2.8

2.1

1.3

0.2

0.0

1.1

1.8

2.7

3.4

4.1

September cloud at Reykjavík averages 80% in NASA POWER's 2001 to 2020 record, close to its yearly mean of 79%. December is Reykjavík's clearest month at 76%. By civil night times clear sky, September scores 1.8 hours at Reykjavík, 7th of 12. Hafnarfjörður, 8 km away, averages the same 80%.

Civil night at Reykjavík starts September at 7 h 31 min and reaches 10 h 51 min by September 30 as the nights lengthen by 3.3 hours. SWPC's 10 PM to 2 AM window is fully dark on every night. True astronomical darkness, the sun 18 degrees down, lasts 4.6 hours on the 15th.

September night by night

Full moon comes first, on Sep 15, then the new moon on Sep 30, in Atlantic/Reykjavik dates. Reykjavík gets 141 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
7.5 h
2
7% lit
7.7 h
3
14% lit
7.8 h
4
23% lit
7.9 h
5
32% lit
8.0 h
6
42% lit
8.1 h
7
52% lit
8.3 h
8
62% lit
8.4 h
9
71% lit
8.5 h
10
79% lit
6.1 h
11
86% lit
4.3 h
12
92% lit
2.6 h
13
96% lit
1.1 h
14
99% lit
0.0 h
15
100% lit
0.0 h
Full
16
99% lit
0.0 h
17
96% lit
0.0 h
18
91% lit
0.0 h
19
84% lit
0.0 h
20
75% lit
0.0 h
21
66% lit
0.0 h
22
55% lit
0.0 h
23
44% lit
0.0 h
24
33% lit
2.5 h
25
22% lit
4.8 h
26
13% lit
6.8 h
27
6% lit
8.8 h
28
2% lit
10.6 h
29
0% lit
10.7 h
30
1% lit
10.8 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

Quiet activity already puts the oval edge over Reykjavík, so storm days matter more: 126 of the 900 September days from 1996 to 2025 (14%) reached Kp 5, one of the three most active months for that level. Reykjavík sits at 68.8 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 0.

September across Iceland

No month-page town in Iceland has more civil night on September 15 than Reykjavík; the national median is 9.2 hours. Coming from August (5.3 hours at Reykjavík), September adds darkness, and the nights keep growing into October (12.5 hours on the 15th). The September equinox falls on September 23, 05:56 Reykjavík time, inside the weeks SWPC links with larger storms.

Civil night on September 15 and September cloud, month-page towns in Iceland
Town	Civil night	Cloud
Reykjavík	9.2 h	80%
Hafnarfjörður	9.2 h	80%
Reykjanesbær	9.2 h	83%
Akureyri	9.0 h	83%

Darkness and moon, every night

Reykjavík, 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 31 min	0 min	7 h 31 min	4 h	2%
Thu Sep 2	7 h 39 min	0 min	7 h 39 min	4 h	7%
Fri Sep 3	7 h 46 min	31 min	7 h 46 min	4 h	14%
Sat Sep 4	7 h 53 min	1 h 23 min	7 h 53 min	4 h	23%
Sun Sep 5	8 h 1 min	1 h 54 min	8 h 1 min	4 h	32%
Mon Sep 6	8 h 8 min	2 h 17 min	8 h 8 min	4 h	42%
Tue Sep 7	8 h 15 min	2 h 38 min	8 h 15 min	4 h	52%
Wed Sep 8	8 h 22 min	2 h 56 min	8 h 22 min	4 h	62%
Thu Sep 9	8 h 29 min	3 h 13 min	8 h 29 min	4 h	71%
Fri Sep 10	8 h 36 min	3 h 28 min	6 h 4 min	2 h 21 min	79%
Sat Sep 11	8 h 44 min	3 h 42 min	4 h 16 min	30 min	86%
Sun Sep 12	8 h 51 min	3 h 56 min	2 h 39 min	0 min	92%
Mon Sep 13	8 h 57 min	4 h 9 min	1 h 8 min	0 min	96%
Tue Sep 14	9 h 4 min	4 h 21 min	0 min	0 min	99%
Wed Sep 15	9 h 11 min	4 h 33 min	0 min	0 min	100%
Thu Sep 16	9 h 18 min	4 h 44 min	0 min	0 min	99%
Fri Sep 17	9 h 25 min	4 h 55 min	0 min	0 min	96%
Sat Sep 18	9 h 32 min	5 h 6 min	0 min	0 min	91%
Sun Sep 19	9 h 38 min	5 h 16 min	0 min	0 min	84%
Mon Sep 20	9 h 45 min	5 h 26 min	0 min	0 min	75%
Tue Sep 21	9 h 52 min	5 h 36 min	0 min	0 min	66%
Wed Sep 22	9 h 59 min	5 h 45 min	0 min	0 min	55%
Thu Sep 23	10 h 5 min	5 h 54 min	0 min	0 min	44%
Fri Sep 24	10 h 12 min	6 h 4 min	2 h 32 min	46 min	33%
Sat Sep 25	10 h 18 min	6 h 12 min	4 h 46 min	2 h 57 min	22%
Sun Sep 26	10 h 25 min	6 h 21 min	6 h 51 min	4 h	13%
Mon Sep 27	10 h 31 min	6 h 30 min	8 h 50 min	4 h	6%
Tue Sep 28	10 h 38 min	6 h 38 min	10 h 38 min	4 h	2%
Wed Sep 29	10 h 44 min	6 h 46 min	10 h 44 min	4 h	0%
Thu Sep 30	10 h 51 min	6 h 54 min	10 h 51 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 Reykjavík in September?: On dark, clear nights with enough activity. 30 of 30 nights at Reykjavík have civil darkness, and 14% of past September days reached Kp 5.
How dark is Reykjavík in September?: Reykjavík averages 9.2 hours of civil night a night in September 2027, from 7 h 31 min on the 1st to 10 h 51 min on the last night.
How cloudy is Reykjavík in September?: NASA POWER's 2001 to 2020 climatology gives Reykjavík's 1 degree cell 80% mean cloud in September, against 79% for the whole year. It is an all-hours average, not a forecast.
What is the best night in September 2027 for aurora in Reykjavík?: By darkness and moon alone, Sep 1, with 4 h of moon-free darkness inside 10 PM to 2 AM at Reykjavík. Activity on that date will only be known hours ahead.
Is September or October better in Reykjavík?: By civil night times the clear share, September scores 1.8 hours at Reykjavík and October 2.7. 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.