Can you see the northern lights in Yellowknife in September?

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

How dark is Yellowknife in September?

Yellowknife averages 9.4 hours of civil night a night in September 2027, from 7 h 52 min on the 1st to 10 h 56 min on the last night.

How cloudy is Yellowknife in September?

NASA POWER's 2001 to 2020 climatology gives Yellowknife's 1 degree cell 66% mean cloud in September, against 63% for the whole year. It is an all-hours average, not a forecast.

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

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

Is September or October better in Yellowknife?

By civil night times the clear share, September scores 3.2 hours at Yellowknife and October 2.4. September comes out ahead.

Yellowknife · September 2027

Northern lights in Yellowknife in September 2027

Answer

September gives Yellowknife 9.4 hours of civil night on the 15th, the 7th darkest of its 12 months, under 66% mean cloud. 14% of September days since 1996 reached storm level, Kp 5.

9.4 h

civil night, average night

SunCalc for 62.45, -114.37; NASA POWER; GFZ Kp

September against the rest of the year

7.0

6.5

5.4

3.0

1.0

0.0

2.1

3.2

2.4

3.8

7.0

September cloud at Yellowknife averages 66% in NASA POWER's 2001 to 2020 record, 3 points cloudier than its yearly mean. March is Yellowknife's clearest month at 49%. By civil night times clear sky, September scores 3.2 hours at Yellowknife, 6th of 12. Fort McMurray, 659 km away, averages 64%, clearer by 2 points.

Civil night at Yellowknife starts September at 7 h 52 min and reaches 10 h 56 min by September 30 as the nights lengthen by 3.1 hours. SWPC's 10 PM to 2 AM window is fully dark on every night. True astronomical darkness, the sun 18 degrees down, lasts 5.3 hours on the 15th.

September night by night

Full moon comes first, on Sep 15, then the new moon on Sep 29, in America/Edmonton dates. Yellowknife gets 145 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
3% lit
7.9 h
2
9% lit
8.0 h
3
16% lit
8.1 h
4
25% lit
8.2 h
5
35% lit
8.3 h
6
45% lit
8.4 h
7
55% lit
8.5 h
8
64% lit
8.7 h
9
73% lit
6.9 h
10
81% lit
5.3 h
11
88% lit
3.7 h
12
93% lit
2.2 h
13
97% lit
0.8 h
14
99% lit
0.0 h
15
100% lit
0.0 h
Full
16
98% lit
0.0 h
17
95% lit
0.0 h
18
89% lit
0.0 h
19
82% lit
0.0 h
20
73% lit
0.0 h
21
63% lit
0.0 h
22
52% lit
0.0 h
23
41% lit
1.6 h
24
30% lit
3.6 h
25
20% lit
5.6 h
26
11% lit
7.5 h
27
5% lit
9.4 h
28
1% lit
10.7 h
29
0% lit
10.8 h
New
30
2% lit
10.9 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

Quiet activity already puts the oval edge over Yellowknife, 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. Yellowknife sits at 68.5 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 Canada

Yellowknife ranks 23rd in Canada for civil night on September 15, behind Québec at 10.4 hours. Coming from August (5.9 hours at Yellowknife), September adds darkness, and the nights keep growing into October (12.4 hours on the 15th). The September equinox falls on September 22, 23:56 Yellowknife time, inside the weeks SWPC links with larger storms.

Civil night on September 15 and September cloud, month-page towns in Canada
Town	Civil night	Cloud
Québec	10.4 h	57%
Greater Sudbury	10.4 h	58%
Trois-Rivières	10.4 h	56%
Sydney	10.4 h	64%
Saguenay	10.3 h	65%
St. John's	10.3 h	69%
Thunder Bay	10.3 h	65%
Calgary	10.2 h	62%
Winnipeg	10.2 h	55%
Regina	10.2 h	55%
Kelowna	10.2 h	53%
Kamloops	10.2 h	58%
Yellowknife	9.4 h	66%

Darkness and moon, every night

Yellowknife, 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 52 min	2 h 10 min	7 h 52 min	4 h	3%
Thu Sep 2	7 h 59 min	2 h 30 min	7 h 59 min	4 h	9%
Fri Sep 3	8 h 6 min	2 h 47 min	8 h 6 min	4 h	16%
Sat Sep 4	8 h 12 min	3 h 3 min	8 h 12 min	4 h	25%
Sun Sep 5	8 h 19 min	3 h 18 min	8 h 19 min	4 h	35%
Mon Sep 6	8 h 26 min	3 h 32 min	8 h 26 min	4 h	45%
Tue Sep 7	8 h 32 min	3 h 45 min	8 h 32 min	4 h	55%
Wed Sep 8	8 h 39 min	3 h 58 min	8 h 39 min	4 h	64%
Thu Sep 9	8 h 45 min	4 h 10 min	6 h 56 min	2 h 58 min	73%
Fri Sep 10	8 h 52 min	4 h 21 min	5 h 15 min	1 h 15 min	81%
Sat Sep 11	8 h 58 min	4 h 32 min	3 h 41 min	0 min	88%
Sun Sep 12	9 h 4 min	4 h 43 min	2 h 11 min	0 min	93%
Mon Sep 13	9 h 11 min	4 h 53 min	45 min	0 min	97%
Tue Sep 14	9 h 17 min	5 h 3 min	0 min	0 min	99%
Wed Sep 15	9 h 24 min	5 h 13 min	0 min	0 min	100%
Thu Sep 16	9 h 30 min	5 h 22 min	0 min	0 min	98%
Fri Sep 17	9 h 36 min	5 h 31 min	0 min	0 min	95%
Sat Sep 18	9 h 42 min	5 h 40 min	0 min	0 min	89%
Sun Sep 19	9 h 49 min	5 h 49 min	0 min	0 min	82%
Mon Sep 20	9 h 55 min	5 h 58 min	0 min	0 min	73%
Tue Sep 21	10 h 1 min	6 h 6 min	0 min	0 min	63%
Wed Sep 22	10 h 7 min	6 h 14 min	0 min	0 min	52%
Thu Sep 23	10 h 13 min	6 h 22 min	1 h 34 min	0 min	41%
Fri Sep 24	10 h 19 min	6 h 30 min	3 h 35 min	1 h 55 min	30%
Sat Sep 25	10 h 26 min	6 h 38 min	5 h 36 min	3 h 52 min	20%
Sun Sep 26	10 h 32 min	6 h 46 min	7 h 32 min	4 h	11%
Mon Sep 27	10 h 38 min	6 h 53 min	9 h 25 min	4 h	5%
Tue Sep 28	10 h 44 min	7 h 1 min	10 h 44 min	4 h	1%
Wed Sep 29	10 h 50 min	7 h 8 min	10 h 50 min	4 h	0%
Thu Sep 30	10 h 56 min	7 h 15 min	10 h 56 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 Yellowknife in September?: On dark, clear nights with enough activity. 30 of 30 nights at Yellowknife have civil darkness, and 14% of past September days reached Kp 5.
How dark is Yellowknife in September?: Yellowknife averages 9.4 hours of civil night a night in September 2027, from 7 h 52 min on the 1st to 10 h 56 min on the last night.
How cloudy is Yellowknife in September?: NASA POWER's 2001 to 2020 climatology gives Yellowknife's 1 degree cell 66% mean cloud in September, against 63% for the whole year. It is an all-hours average, not a forecast.
What is the best night in September 2027 for aurora in Yellowknife?: By darkness and moon alone, Sep 1, with 4 h of moon-free darkness inside 10 PM to 2 AM at Yellowknife. Activity on that date will only be known hours ahead.
Is September or October better in Yellowknife?: By civil night times the clear share, September scores 3.2 hours at Yellowknife and October 2.4. September 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.