Can you see the northern lights in Castlereagh in July?

On dark, clear nights with enough activity. 31 of 31 nights at Castlereagh have civil darkness, and 9% of past July days reached Kp 5.

How dark is Castlereagh in July?

Castlereagh averages 5.5 hours of civil night a night in July 2027, from 4 h 47 min on the 1st to 6 h 27 min on the last night.

How cloudy is Castlereagh in July?

NASA POWER's 2001 to 2020 climatology gives Castlereagh's 1 degree cell 77% mean cloud in July, against 77% for the whole year. It is an all-hours average, not a forecast.

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

By darkness and moon alone, Jul 31, with 3 h 43 min of moon-free darkness inside 10 PM to 2 AM at Castlereagh. Activity on that date will only be known hours ahead.

Is July or August better in Castlereagh?

By civil night times the clear share, July scores 1.2 hours at Castlereagh and August 1.8. August comes out ahead.

Castlereagh · July 2027

Northern lights in Castlereagh in July 2027

Answer

July gives Castlereagh 5.4 hours of civil night on the 15th, the 11th darkest of its 12 months, under 77% mean cloud. 9% of July days since 1996 reached Kp 5, enough for the oval edge to reach Castlereagh.

5.5 h

civil night, average night

SunCalc for 54.57, -5.88; NASA POWER; GFZ Kp

July against the rest of the year

2.8

2.7

2.6

2.4

1.9

1.2

1.8

2.4

2.6

2.8

3.0

July cloud at Castlereagh averages 77% in NASA POWER's 2001 to 2020 record, close to its yearly mean of 77%. May is Castlereagh's clearest month at 70%. By civil night times clear sky, July scores 1.2 hours at Castlereagh, 11th of 12. Belfast, 4 km away, averages the same 77%.

Civil night at Castlereagh starts July at 4 h 47 min and reaches 6 h 27 min by July 31 as the nights lengthen by 1.7 hours. No night keeps the 10 PM to 2 AM window fully dark at Castlereagh. The sun never reaches 18 degrees down, so Castlereagh gets no astronomical night in July.

July night by night

July opens toward a new moon on Jul 4, with full moon on Jul 18, in Europe/London dates. Castlereagh gets 78 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 31 (3 h 43 min), Jul 30 (3 h 41 min), Jul 5 (2 h 59 min).

1
7% lit
3.4 h
2
2% lit
4.4 h
3
0% lit
4.8 h
4
1% lit
4.9 h
New
5
5% lit
4.9 h
6
12% lit
4.7 h
7
20% lit
4.5 h
8
30% lit
4.3 h
9
41% lit
4.2 h
10
52% lit
4.0 h
11
63% lit
3.9 h
12
72% lit
3.6 h
13
81% lit
3.2 h
14
88% lit
2.7 h
15
93% lit
1.9 h
16
97% lit
0.9 h
17
100% lit
0.0 h
18
100% lit
0.0 h
Full
19
98% lit
0.0 h
20
95% lit
0.0 h
21
91% lit
0.0 h
22
84% lit
0.1 h
23
77% lit
0.3 h
24
68% lit
0.5 h
25
58% lit
0.7 h
26
47% lit
1.0 h
27
37% lit
1.3 h
28
26% lit
1.9 h
29
17% lit
2.7 h
30
9% lit
3.9 h
31
3% lit
5.5 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

Castlereagh needs Kp 5 for the average oval edge to sit overhead. 81 of the 930 July days from 1996 to 2025 (9%) reached it in the GFZ Potsdam record, 8th of 12 months; storm days with Kp 5 or more made up 9%. Castlereagh sits at 57.2 degrees geomagnetic. By SWPC's rule the average oval edge is overhead at Kp 5, and aurora is usually visible on the northern horizon at G1 (Kp 5) or less.

July across United Kingdom

Castlereagh ranks 19th in United Kingdom for civil night on July 15, behind Stoke-on-Trent at 5.9 hours. Coming from June (4.7 hours at Castlereagh), July adds darkness, and the nights keep growing into August (7.6 hours on the 15th).

Civil night on July 15 and July cloud, month-page towns in United Kingdom
Town	Civil night	Cloud
Stoke-on-Trent	5.9 h	75%
Sheffield	5.8 h	74%
Mansfield	5.8 h	74%
Chesterfield	5.8 h	74%
Lincoln	5.8 h	74%
Manchester, England	5.7 h	75%
Liverpool	5.7 h	75%
Kingston upon Hull	5.7 h	74%
St Helens	5.7 h	75%
Huddersfield	5.7 h	74%
Bolton	5.7 h	75%
Doncaster	5.7 h	74%
Castlereagh	5.4 h	77%

Darkness and moon, every night

Castlereagh, July 2027: each night from local noon to the next noon
Night	Civil	Moon-free dark	Moon-free, 10 PM to 2 AM	Moon lit
Thu Jul 1	4 h 47 min	3 h 22 min	2 h 56 min	7%
Fri Jul 2	4 h 49 min	4 h 23 min	2 h 57 min	2%
Sat Jul 3	4 h 51 min	4 h 51 min	2 h 57 min	0%
Sun Jul 4	4 h 53 min	4 h 53 min	2 h 58 min	1%
Mon Jul 5	4 h 55 min	4 h 55 min	2 h 59 min	5%
Tue Jul 6	4 h 57 min	4 h 40 min	2 h 43 min	12%
Wed Jul 7	5 h	4 h 29 min	2 h 30 min	20%
Thu Jul 8	5 h 2 min	4 h 20 min	2 h 20 min	30%
Fri Jul 9	5 h 5 min	4 h 11 min	2 h 10 min	41%
Sat Jul 10	5 h 8 min	4 h 2 min	1 h 59 min	52%
Sun Jul 11	5 h 11 min	3 h 51 min	1 h 46 min	63%
Mon Jul 12	5 h 14 min	3 h 36 min	1 h 29 min	72%
Tue Jul 13	5 h 17 min	3 h 14 min	1 h 6 min	81%
Wed Jul 14	5 h 20 min	2 h 42 min	32 min	88%
Thu Jul 15	5 h 24 min	1 h 56 min	0 min	93%
Fri Jul 16	5 h 27 min	56 min	0 min	97%
Sat Jul 17	5 h 31 min	0 min	0 min	100%
Sun Jul 18	5 h 34 min	0 min	0 min	100%
Mon Jul 19	5 h 38 min	0 min	0 min	98%
Tue Jul 20	5 h 42 min	0 min	0 min	95%
Wed Jul 21	5 h 45 min	0 min	0 min	91%
Thu Jul 22	5 h 49 min	9 min	9 min	84%
Fri Jul 23	5 h 53 min	19 min	19 min	77%
Sat Jul 24	5 h 57 min	29 min	29 min	68%
Sun Jul 25	6 h 1 min	42 min	42 min	58%
Mon Jul 26	6 h 5 min	58 min	58 min	47%
Tue Jul 27	6 h 10 min	1 h 20 min	1 h 20 min	37%
Wed Jul 28	6 h 14 min	1 h 53 min	1 h 53 min	26%
Thu Jul 29	6 h 18 min	2 h 43 min	2 h 43 min	17%
Fri Jul 30	6 h 22 min	3 h 56 min	3 h 41 min	9%
Sat Jul 31	6 h 27 min	5 h 28 min	3 h 43 min	3%

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

Questions

Can you see the northern lights in Castlereagh in July?: On dark, clear nights with enough activity. 31 of 31 nights at Castlereagh have civil darkness, and 9% of past July days reached Kp 5.
How dark is Castlereagh in July?: Castlereagh averages 5.5 hours of civil night a night in July 2027, from 4 h 47 min on the 1st to 6 h 27 min on the last night.
How cloudy is Castlereagh in July?: NASA POWER's 2001 to 2020 climatology gives Castlereagh's 1 degree cell 77% mean cloud in July, against 77% for the whole year. It is an all-hours average, not a forecast.
What is the best night in July 2027 for aurora in Castlereagh?: By darkness and moon alone, Jul 31, with 3 h 43 min of moon-free darkness inside 10 PM to 2 AM at Castlereagh. Activity on that date will only be known hours ahead.
Is July or August better in Castlereagh?: By civil night times the clear share, July scores 1.2 hours at Castlereagh and August 1.8. 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.