Can you see the northern lights in Isle of Lewis in September?

On dark, clear nights with enough activity. 30 of 30 nights at Isle of Lewis have civil darkness, and 57% of past September days reached Kp 3.

How dark is Isle of Lewis in September?

Isle of Lewis averages 9.8 hours of civil night a night in September 2027, from 8 h 28 min on the 1st to 11 h on the last night.

How cloudy is Isle of Lewis in September?

NASA POWER's 2001 to 2020 climatology gives Isle of Lewis's 1 degree cell 84% mean cloud in September, against 85% for the whole year. It is an all-hours average, not a forecast.

What is the best night in September 2027 for aurora in Isle of Lewis?

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

Is September or October better in Isle of Lewis?

By civil night times the clear share, September scores 1.6 hours at Isle of Lewis and October 1.8. October comes out ahead.

Isle of Lewis · September 2027

Northern lights in Isle of Lewis in September 2027

Answer

September gives Isle of Lewis 9.7 hours of civil night on the 15th, the 7th darkest of its 12 months, under 84% mean cloud. 57% of September days since 1996 reached Kp 3, enough for the oval edge to reach Isle of Lewis.

9.8 h

civil night, average night

SunCalc for 58.22, -6.39; NASA POWER; GFZ Kp

September against the rest of the year

1.7

1.5

1.0

0.4

0.5

1.0

1.6

1.8

1.7

September cloud at Isle of Lewis averages 84% in NASA POWER's 2001 to 2020 record, close to its yearly mean of 85%. May is Isle of Lewis's clearest month at 80%. By civil night times clear sky, September scores 1.6 hours at Isle of Lewis, 7th of 12. Aberdeen, 282 km away, averages 77%, clearer by 7 points.

Civil night at Isle of Lewis starts September at 8 h 28 min and reaches 11 h by September 30 as the nights lengthen by 2.5 hours. SWPC's 10 PM to 2 AM window is fully dark on every night. True astronomical darkness, the sun 18 degrees down, lasts 6.3 hours on the 15th.

September night by night

Full moon comes first, on Sep 16, then the new moon on Sep 30, in Europe/London dates. Isle of Lewis gets 149 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
8.5 h
2
7% lit
8.6 h
3
14% lit
8.7 h
4
23% lit
8.8 h
5
32% lit
8.8 h
6
42% lit
8.9 h
7
52% lit
8.4 h
8
62% lit
7.6 h
9
71% lit
6.5 h
10
79% lit
5.2 h
11
86% lit
3.8 h
12
92% lit
2.5 h
13
96% lit
1.1 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
84% lit
0.0 h
20
76% lit
0.0 h
21
66% lit
0.2 h
22
55% lit
1.0 h
23
44% lit
2.3 h
24
33% lit
3.9 h
25
23% lit
5.6 h
26
14% lit
7.3 h
27
6% lit
9.1 h
28
2% lit
10.8 h
29
0% lit
10.9 h
30
1% lit
11.0 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

Isle of Lewis needs Kp 3 for the average oval edge to sit overhead. 514 of the 900 September days from 1996 to 2025 (57%) 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%. Isle of Lewis sits at 60.8 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 3.

September across United Kingdom

Isle of Lewis ranks 27th in United Kingdom for civil night on September 15, behind Stoke-on-Trent at 10.1 hours. Coming from August (6.9 hours at Isle of Lewis), September adds darkness, and the nights keep growing into October (12.3 hours on the 15th). The September equinox falls on September 23, 06:56 Isle of Lewis time, inside the weeks SWPC links with larger storms.

Civil night on September 15 and September cloud, month-page towns in United Kingdom
Town	Civil night	Cloud
Stoke-on-Trent	10.1 h	75%
Mansfield	10.1 h	71%
Chesterfield	10.1 h	71%
Lincoln	10.1 h	71%
Manchester, England	10.0 h	75%
Sheffield	10.0 h	71%
Leeds	10.0 h	71%
Liverpool	10.0 h	75%
Belfast	10.0 h	76%
Kingston upon Hull	10.0 h	71%
Preston	10.0 h	75%
Newcastle upon Tyne	10.0 h	75%
Isle of Lewis	9.7 h	84%

Darkness and moon, every night

Isle of Lewis, 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	8 h 28 min	4 h 26 min	8 h 28 min	4 h	2%
Thu Sep 2	8 h 34 min	4 h 35 min	8 h 34 min	4 h	7%
Fri Sep 3	8 h 39 min	4 h 43 min	8 h 39 min	4 h	14%
Sat Sep 4	8 h 45 min	4 h 52 min	8 h 45 min	4 h	23%
Sun Sep 5	8 h 50 min	5 h 1 min	8 h 50 min	4 h	32%
Mon Sep 6	8 h 55 min	5 h 9 min	8 h 55 min	4 h	42%
Tue Sep 7	9 h 1 min	5 h 17 min	8 h 26 min	4 h	52%
Wed Sep 8	9 h 6 min	5 h 25 min	7 h 36 min	3 h 39 min	62%
Thu Sep 9	9 h 11 min	5 h 32 min	6 h 27 min	2 h 28 min	71%
Fri Sep 10	9 h 17 min	5 h 40 min	5 h 9 min	1 h 7 min	79%
Sat Sep 11	9 h 22 min	5 h 47 min	3 h 48 min	0 min	86%
Sun Sep 12	9 h 27 min	5 h 55 min	2 h 28 min	0 min	92%
Mon Sep 13	9 h 33 min	6 h 2 min	1 h 9 min	0 min	96%
Tue Sep 14	9 h 38 min	6 h 9 min	0 min	0 min	99%
Wed Sep 15	9 h 43 min	6 h 16 min	0 min	0 min	100%
Thu Sep 16	9 h 48 min	6 h 23 min	0 min	0 min	99%
Fri Sep 17	9 h 54 min	6 h 30 min	0 min	0 min	96%
Sat Sep 18	9 h 59 min	6 h 36 min	0 min	0 min	91%
Sun Sep 19	10 h 4 min	6 h 43 min	0 min	0 min	84%
Mon Sep 20	10 h 9 min	6 h 50 min	0 min	0 min	76%
Tue Sep 21	10 h 14 min	6 h 56 min	11 min	0 min	66%
Wed Sep 22	10 h 20 min	7 h 2 min	1 h	0 min	55%
Thu Sep 23	10 h 25 min	7 h 9 min	2 h 16 min	22 min	44%
Fri Sep 24	10 h 30 min	7 h 15 min	3 h 52 min	1 h 55 min	33%
Sat Sep 25	10 h 35 min	7 h 21 min	5 h 36 min	3 h 36 min	23%
Sun Sep 26	10 h 40 min	7 h 27 min	7 h 21 min	4 h	14%
Mon Sep 27	10 h 45 min	7 h 33 min	9 h 4 min	4 h	6%
Tue Sep 28	10 h 50 min	7 h 39 min	10 h 45 min	4 h	2%
Wed Sep 29	10 h 55 min	7 h 45 min	10 h 55 min	4 h	0%
Thu Sep 30	11 h	7 h 50 min	11 h	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 Isle of Lewis in September?: On dark, clear nights with enough activity. 30 of 30 nights at Isle of Lewis have civil darkness, and 57% of past September days reached Kp 3.
How dark is Isle of Lewis in September?: Isle of Lewis averages 9.8 hours of civil night a night in September 2027, from 8 h 28 min on the 1st to 11 h on the last night.
How cloudy is Isle of Lewis in September?: NASA POWER's 2001 to 2020 climatology gives Isle of Lewis's 1 degree cell 84% mean cloud in September, against 85% for the whole year. It is an all-hours average, not a forecast.
What is the best night in September 2027 for aurora in Isle of Lewis?: By darkness and moon alone, Sep 1, with 4 h of moon-free darkness inside 10 PM to 2 AM at Isle of Lewis. Activity on that date will only be known hours ahead.
Is September or October better in Isle of Lewis?: By civil night times the clear share, September scores 1.6 hours at Isle of Lewis and October 1.8. 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.