Can you see the northern lights in Juneau in September?

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

How dark is Juneau in September?

Juneau averages 9.8 hours of civil night a night in September 2027, from 8 h 30 min on the 1st to 11 h 2 min on the last night.

How cloudy is Juneau in September?

NASA POWER's 2001 to 2020 climatology gives Juneau's 1 degree cell 81% 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 Juneau?

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

Is September or October better in Juneau?

By civil night times the clear share, September scores 1.9 hours at Juneau and October 2.3. October comes out ahead.

Juneau · September 2027

Northern lights in Juneau in September 2027

Answer

September gives Juneau 9.8 hours of civil night on the 15th, the 7th darkest of its 12 months, under 81% mean cloud. 57% of September days since 1996 reached Kp 3, enough for the oval edge to reach Juneau.

9.8 h

civil night, average night

SunCalc for 58.30, -134.42; NASA POWER; GFZ Kp

September against the rest of the year

3.0

3.3

2.6

2.0

1.3

0.5

0.8

1.4

1.9

2.3

3.0

3.1

September cloud at Juneau averages 81% in NASA POWER's 2001 to 2020 record, 2 points cloudier than its yearly mean. May is Juneau's clearest month at 74%. By civil night times clear sky, September scores 1.9 hours at Juneau, 8th of 12. Whitehorse, 271 km away, averages 74%, clearer by 7 points.

Civil night at Juneau starts September at 8 h 30 min and reaches 11 h 2 min 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 15, then the new moon on Sep 29, in America/Juneau dates. Juneau gets 150 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
4% lit
8.5 h
2
9% lit
8.6 h
3
17% lit
8.7 h
4
26% lit
8.8 h
5
36% lit
8.8 h
6
46% lit
8.8 h
7
56% lit
8.2 h
8
65% lit
7.2 h
9
74% lit
6.0 h
10
82% lit
4.7 h
11
88% lit
3.3 h
12
94% lit
2.0 h
13
98% lit
0.7 h
14
100% lit
0.0 h
15
100% lit
0.0 h
Full
16
98% lit
0.0 h
17
94% lit
0.0 h
18
89% lit
0.0 h
19
81% lit
0.0 h
20
72% lit
0.0 h
21
62% lit
0.4 h
22
51% lit
1.4 h
23
40% lit
2.8 h
24
29% lit
4.5 h
25
19% lit
6.2 h
26
11% lit
8.0 h
27
4% lit
9.7 h
28
1% lit
10.9 h
29
0% lit
10.9 h
New
30
2% lit
11.0 h

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

Juneau 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%. Juneau sits at 61.6 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 States

Juneau ranks 7th in United States for civil night on September 15, behind Buffalo at 10.5 hours. Coming from August (6.9 hours at Juneau), September adds darkness, and the nights keep growing into October (12.3 hours on the 15th). The September equinox falls on September 22, 21:56 Juneau time, inside the weeks SWPC links with larger storms.

Civil night on September 15 and September cloud, month-page towns in United States
Town	Civil night	Cloud
Buffalo	10.5 h	57%
Portland, Maine	10.5 h	50%
Minneapolis	10.4 h	49%
Duluth	10.4 h	56%
Fargo	10.4 h	50%
Seattle	10.3 h	53%
Juneau	9.8 h	81%
Anchorage	9.5 h	78%
Eagle River	9.5 h	78%
Fairbanks	9.2 h	72%

Darkness and moon, every night

Juneau, 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 30 min	4 h 27 min	8 h 30 min	4 h	4%
Thu Sep 2	8 h 35 min	4 h 36 min	8 h 35 min	4 h	9%
Fri Sep 3	8 h 41 min	4 h 45 min	8 h 41 min	4 h	17%
Sat Sep 4	8 h 46 min	4 h 54 min	8 h 46 min	4 h	26%
Sun Sep 5	8 h 51 min	5 h 2 min	8 h 51 min	4 h	36%
Mon Sep 6	8 h 57 min	5 h 10 min	8 h 49 min	4 h	46%
Tue Sep 7	9 h 2 min	5 h 18 min	8 h 11 min	4 h	56%
Wed Sep 8	9 h 8 min	5 h 26 min	7 h 14 min	3 h 44 min	65%
Thu Sep 9	9 h 13 min	5 h 34 min	6 h	2 h 29 min	74%
Fri Sep 10	9 h 18 min	5 h 41 min	4 h 40 min	1 h 6 min	82%
Sat Sep 11	9 h 24 min	5 h 49 min	3 h 19 min	0 min	88%
Sun Sep 12	9 h 29 min	5 h 56 min	2 h	0 min	94%
Mon Sep 13	9 h 34 min	6 h 3 min	42 min	0 min	98%
Tue Sep 14	9 h 39 min	6 h 11 min	0 min	0 min	100%
Wed Sep 15	9 h 45 min	6 h 18 min	0 min	0 min	100%
Thu Sep 16	9 h 50 min	6 h 24 min	0 min	0 min	98%
Fri Sep 17	9 h 55 min	6 h 31 min	0 min	0 min	94%
Sat Sep 18	10 h	6 h 38 min	0 min	0 min	89%
Sun Sep 19	10 h 6 min	6 h 44 min	0 min	0 min	81%
Mon Sep 20	10 h 11 min	6 h 51 min	0 min	0 min	72%
Tue Sep 21	10 h 16 min	6 h 57 min	24 min	0 min	62%
Wed Sep 22	10 h 21 min	7 h 4 min	1 h 23 min	0 min	51%
Thu Sep 23	10 h 26 min	7 h 10 min	2 h 48 min	25 min	40%
Fri Sep 24	10 h 31 min	7 h 16 min	4 h 28 min	2 h 2 min	29%
Sat Sep 25	10 h 37 min	7 h 22 min	6 h 13 min	3 h 44 min	19%
Sun Sep 26	10 h 42 min	7 h 28 min	7 h 57 min	4 h	11%
Mon Sep 27	10 h 47 min	7 h 34 min	9 h 40 min	4 h	4%
Tue Sep 28	10 h 52 min	7 h 40 min	10 h 52 min	4 h	1%
Wed Sep 29	10 h 57 min	7 h 46 min	10 h 57 min	4 h	0%
Thu Sep 30	11 h 2 min	7 h 52 min	11 h 2 min	4 h	2%

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

Questions

Can you see the northern lights in Juneau in September?: On dark, clear nights with enough activity. 30 of 30 nights at Juneau have civil darkness, and 57% of past September days reached Kp 3.
How dark is Juneau in September?: Juneau averages 9.8 hours of civil night a night in September 2027, from 8 h 30 min on the 1st to 11 h 2 min on the last night.
How cloudy is Juneau in September?: NASA POWER's 2001 to 2020 climatology gives Juneau's 1 degree cell 81% 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 Juneau?: By darkness and moon alone, Sep 1, with 4 h of moon-free darkness inside 10 PM to 2 AM at Juneau. Activity on that date will only be known hours ahead.
Is September or October better in Juneau?: By civil night times the clear share, September scores 1.9 hours at Juneau and October 2.3. 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.