Can you see the northern lights in Sarnia in July?

On dark, clear nights with enough activity. 31 of 31 nights at Sarnia have civil darkness, and 1% of past July days reached Kp 7.

How dark is Sarnia in July?

Sarnia averages 7.8 hours of civil night a night in July 2027, from 7 h 25 min on the 1st to 8 h 18 min on the last night.

How cloudy is Sarnia in July?

NASA POWER's 2001 to 2020 climatology gives Sarnia's 1 degree cell 50% mean cloud in July, against 64% for the whole year. It is an all-hours average, not a forecast.

What is the best night in July 2027 for aurora in Sarnia?

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

Is July or August better in Sarnia?

By civil night times the clear share, July scores 3.9 hours at Sarnia and August 4.3. August comes out ahead.

Sarnia · July 2027

Northern lights in Sarnia in July 2027

Answer

July gives Sarnia 7.7 hours of civil night on the 15th, the 11th darkest of its 12 months, under 50% mean cloud. 1% of July days since 1996 reached Kp 7, enough for the oval edge to reach Sarnia.

7.8 h

civil night, average night

SunCalc for 42.98, -82.40; NASA POWER; GFZ Kp

July against the rest of the year

3.1

3.2

3.3

2.8

3.2

3.9

4.3

5.4

4.5

4.2

2.9

July cloud at Sarnia averages 50% in NASA POWER's 2001 to 2020 record, 14 points clearer than its yearly mean. September is Sarnia's clearest month at 49%. By civil night times clear sky, July scores 3.9 hours at Sarnia, 5th of 12. Buffalo, 287 km away, averages 56%, cloudier by 6 points.

Civil night at Sarnia starts July at 7 h 25 min and reaches 8 h 18 min by July 31 as the nights lengthen by 0.9 hours. SWPC's 10 PM to 2 AM window is fully dark on every night. True astronomical darkness, the sun 18 degrees down, lasts 4.5 hours on the 15th.

July night by night

July opens toward a new moon on Jul 3, with full moon on Jul 18, in America/Toronto dates. Sarnia gets 116 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: Jul 1 (4 h), Jul 2 (4 h), Jul 3 (4 h).

1
6% lit
6.0 h
2
1% lit
7.1 h
3
0% lit
7.5 h
New
4
2% lit
7.3 h
5
6% lit
6.7 h
6
13% lit
6.3 h
7
22% lit
5.8 h
8
33% lit
5.5 h
9
43% lit
5.1 h
10
54% lit
4.7 h
11
65% lit
4.3 h
12
74% lit
3.8 h
13
82% lit
3.2 h
14
89% lit
2.5 h
15
94% lit
1.6 h
16
98% lit
0.7 h
17
100% lit
0.0 h
18
100% lit
0.0 h
Full
19
98% lit
0.1 h
20
94% lit
0.5 h
21
89% lit
0.8 h
22
83% lit
1.2 h
23
75% lit
1.5 h
24
66% lit
1.9 h
25
56% lit
2.3 h
26
45% lit
2.8 h
27
35% lit
3.3 h
28
24% lit
4.1 h
29
15% lit
5.1 h
30
8% lit
6.3 h
31
2% lit
7.7 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 Julys

Sarnia needs Kp 7 for the average oval edge to sit overhead. 10 of the 930 July days from 1996 to 2025 (1%) reached it in the GFZ Potsdam record, 8th of 12 months; storm days with Kp 5 or more made up 9%. Sarnia sits at 52.0 degrees geomagnetic. The lowest NOAA storm level whose typical viewing latitude reaches it is G3 (Kp = 7). By SWPC's rule the average oval edge is overhead only at Kp 7.

July across Canada

No month-page town in Canada has more civil night on July 15 than Sarnia; the national median is 6.5 hours. Coming from June (7.4 hours at Sarnia), July adds darkness, and the nights keep growing into August (9.0 hours on the 15th).

Civil night on July 15 and July cloud, month-page towns in Canada
Town	Civil night	Cloud
Sarnia	7.7 h	50%
Sydney	7.3 h	66%
Québec	7.2 h	62%
Greater Sudbury	7.2 h	54%
Trois-Rivières	7.2 h	60%
St. John's	7.0 h	73%
Saguenay	6.9 h	70%
Thunder Bay	6.9 h	65%
Winnipeg	6.6 h	50%
Kelowna	6.6 h	44%
Lethbridge	6.6 h	42%
Regina	6.5 h	49%

Darkness and moon, every night

Sarnia, July 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
Thu Jul 1	7 h 25 min	3 h 59 min	6 h 2 min	4 h	6%
Fri Jul 2	7 h 26 min	4 h	7 h 8 min	4 h	1%
Sat Jul 3	7 h 27 min	4 h 2 min	7 h 27 min	4 h	0%
Sun Jul 4	7 h 28 min	4 h 4 min	7 h 19 min	4 h	2%
Mon Jul 5	7 h 29 min	4 h 6 min	6 h 44 min	3 h 25 min	6%
Tue Jul 6	7 h 30 min	4 h 8 min	6 h 15 min	2 h 55 min	13%
Wed Jul 7	7 h 32 min	4 h 10 min	5 h 51 min	2 h 30 min	22%
Thu Jul 8	7 h 33 min	4 h 12 min	5 h 29 min	2 h 7 min	33%
Fri Jul 9	7 h 34 min	4 h 15 min	5 h 7 min	1 h 45 min	43%
Sat Jul 10	7 h 36 min	4 h 17 min	4 h 44 min	1 h 21 min	54%
Sun Jul 11	7 h 37 min	4 h 20 min	4 h 19 min	55 min	65%
Mon Jul 12	7 h 39 min	4 h 22 min	3 h 49 min	24 min	74%
Tue Jul 13	7 h 40 min	4 h 25 min	3 h 13 min	0 min	82%
Wed Jul 14	7 h 42 min	4 h 28 min	2 h 30 min	0 min	89%
Thu Jul 15	7 h 44 min	4 h 31 min	1 h 39 min	0 min	94%
Fri Jul 16	7 h 45 min	4 h 34 min	42 min	0 min	98%
Sat Jul 17	7 h 47 min	4 h 37 min	0 min	0 min	100%
Sun Jul 18	7 h 49 min	4 h 40 min	0 min	0 min	100%
Mon Jul 19	7 h 51 min	4 h 43 min	7 min	0 min	98%
Tue Jul 20	7 h 53 min	4 h 46 min	30 min	10 min	94%
Wed Jul 21	7 h 55 min	4 h 50 min	51 min	30 min	89%
Thu Jul 22	7 h 57 min	4 h 53 min	1 h 11 min	49 min	83%
Fri Jul 23	7 h 59 min	4 h 56 min	1 h 31 min	1 h 7 min	75%
Sat Jul 24	8 h 1 min	5 h	1 h 52 min	1 h 28 min	66%
Sun Jul 25	8 h 4 min	5 h 3 min	2 h 16 min	1 h 51 min	56%
Mon Jul 26	8 h 6 min	5 h 7 min	2 h 45 min	2 h 18 min	45%
Tue Jul 27	8 h 8 min	5 h 10 min	3 h 20 min	2 h 53 min	35%
Wed Jul 28	8 h 10 min	5 h 14 min	4 h 7 min	3 h 38 min	24%
Thu Jul 29	8 h 13 min	5 h 17 min	5 h 6 min	4 h	15%
Fri Jul 30	8 h 15 min	5 h 21 min	6 h 18 min	4 h	8%
Sat Jul 31	8 h 18 min	5 h 24 min	7 h 39 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 Sarnia in July?: On dark, clear nights with enough activity. 31 of 31 nights at Sarnia have civil darkness, and 1% of past July days reached Kp 7.
How dark is Sarnia in July?: Sarnia averages 7.8 hours of civil night a night in July 2027, from 7 h 25 min on the 1st to 8 h 18 min on the last night.
How cloudy is Sarnia in July?: NASA POWER's 2001 to 2020 climatology gives Sarnia's 1 degree cell 50% mean cloud in July, against 64% for the whole year. It is an all-hours average, not a forecast.
What is the best night in July 2027 for aurora in Sarnia?: By darkness and moon alone, Jul 1, with 4 h of moon-free darkness inside 10 PM to 2 AM at Sarnia. Activity on that date will only be known hours ahead.
Is July or August better in Sarnia?: By civil night times the clear share, July scores 3.9 hours at Sarnia and August 4.3. August 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.