Can you see the northern lights in Viljandi in July?

On dark, clear nights with enough activity. 31 of 31 nights at Viljandi have civil darkness, and 3% of past July days reached Kp 6.

How dark is Viljandi in July?

Viljandi averages 4.1 hours of civil night a night in July 2027, from 2 h 58 min on the 1st to 5 h 25 min on the last night.

How cloudy is Viljandi in July?

NASA POWER's 2001 to 2020 climatology gives Viljandi's 1 degree cell 63% mean cloud in July, against 71% for the whole year. It is an all-hours average, not a forecast.

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

By darkness and moon alone, Jul 31, with 3 h 18 min of moon-free darkness inside 10 PM to 2 AM at Viljandi. Activity on that date will only be known hours ahead.

Is July or August better in Viljandi?

By civil night times the clear share, July scores 1.5 hours at Viljandi and August 2.6. August comes out ahead.

Viljandi · July 2027

Northern lights in Viljandi in July 2027

Answer

July gives Viljandi 4.0 hours of civil night on the 15th, the 11th darkest of its 12 months, under 63% mean cloud. 3% of July days since 1996 reached Kp 6, enough for the oval edge to reach Viljandi.

4.1 h

civil night, average night

SunCalc for 58.36, 25.59; NASA POWER; GFZ Kp

July against the rest of the year

2.4

2.9

3.5

3.1

2.2

1.0

1.5

2.6

3.1

2.3

2.2

July cloud at Viljandi averages 63% in NASA POWER's 2001 to 2020 record, 8 points clearer than its yearly mean. May is Viljandi's clearest month at 56%. By civil night times clear sky, July scores 1.5 hours at Viljandi, 11th of 12. Tallinn, 129 km away, averages 61%, clearer by 2 points.

Civil night at Viljandi starts July at 2 h 58 min and reaches 5 h 25 min by July 31 as the nights lengthen by 2.5 hours. No night keeps the 10 PM to 2 AM window fully dark at Viljandi. The sun never reaches 18 degrees down, so Viljandi 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/Tallinn dates. Viljandi gets 56 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 18 min), Jul 30 (2 h 39 min), Jul 9 (2 h 21 min).

1
7% lit
1.8 h
2
2% lit
2.7 h
3
0% lit
3.1 h
4
1% lit
3.1 h
New
5
5% lit
3.2 h
6
11% lit
3.3 h
7
20% lit
3.3 h
8
30% lit
3.4 h
9
40% lit
3.5 h
10
51% lit
3.5 h
11
62% lit
3.4 h
12
71% lit
3.3 h
13
80% lit
3.1 h
14
87% lit
2.7 h
15
93% lit
2.0 h
16
97% lit
1.0 h
17
99% lit
0.0 h
18
100% lit
0.0 h
Full
19
99% lit
0.0 h
20
96% lit
0.0 h
21
91% lit
0.0 h
22
85% lit
0.0 h
23
77% lit
0.0 h
24
68% lit
0.0 h
25
59% lit
0.0 h
26
48% lit
0.1 h
27
38% lit
0.3 h
28
27% lit
0.7 h
29
18% lit
1.4 h
30
10% lit
2.6 h
31
4% lit
4.3 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

Viljandi needs Kp 6 for the average oval edge to sit overhead. 26 of the 930 July days from 1996 to 2025 (3%) reached it in the GFZ Potsdam record, 9th of 12 months; storm days with Kp 5 or more made up 9%. Viljandi sits at 55.9 degrees geomagnetic. By SWPC's rule the average oval edge is overhead at Kp 6, and aurora is usually visible on the northern horizon at G1 (Kp 5) or less.

July across Estonia

No month-page town in Estonia has more civil night on July 15 than Viljandi; the national median is 3.7 hours. Coming from June (2.8 hours at Viljandi), July adds darkness, and the nights keep growing into August (6.9 hours on the 15th).

Civil night on July 15 and July cloud, month-page towns in Estonia
Town	Civil night	Cloud
Viljandi	4.0 h	63%
Tallinn	3.4 h	61%

Darkness and moon, every night

Viljandi, 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	2 h 58 min	1 h 46 min	1 h 46 min	7%
Fri Jul 2	3 h 1 min	2 h 42 min	2 h 9 min	2%
Sat Jul 3	3 h 5 min	3 h 5 min	2 h 10 min	0%
Sun Jul 4	3 h 8 min	3 h 8 min	2 h 12 min	1%
Mon Jul 5	3 h 12 min	3 h 12 min	2 h 14 min	5%
Tue Jul 6	3 h 16 min	3 h 16 min	2 h 15 min	11%
Wed Jul 7	3 h 20 min	3 h 20 min	2 h 17 min	20%
Thu Jul 8	3 h 24 min	3 h 24 min	2 h 19 min	30%
Fri Jul 9	3 h 29 min	3 h 29 min	2 h 21 min	40%
Sat Jul 10	3 h 33 min	3 h 28 min	2 h 18 min	51%
Sun Jul 11	3 h 38 min	3 h 24 min	2 h 12 min	62%
Mon Jul 12	3 h 43 min	3 h 17 min	2 h 2 min	71%
Tue Jul 13	3 h 47 min	3 h 5 min	1 h 48 min	80%
Wed Jul 14	3 h 52 min	2 h 42 min	1 h 22 min	87%
Thu Jul 15	3 h 58 min	2 h 2 min	39 min	93%
Fri Jul 16	4 h 3 min	1 h	0 min	97%
Sat Jul 17	4 h 8 min	0 min	0 min	99%
Sun Jul 18	4 h 13 min	0 min	0 min	100%
Mon Jul 19	4 h 18 min	0 min	0 min	99%
Tue Jul 20	4 h 24 min	0 min	0 min	96%
Wed Jul 21	4 h 29 min	0 min	0 min	91%
Thu Jul 22	4 h 35 min	0 min	0 min	85%
Fri Jul 23	4 h 40 min	0 min	0 min	77%
Sat Jul 24	4 h 46 min	0 min	0 min	68%
Sun Jul 25	4 h 51 min	0 min	0 min	59%
Mon Jul 26	4 h 57 min	4 min	4 min	48%
Tue Jul 27	5 h 3 min	19 min	19 min	38%
Wed Jul 28	5 h 8 min	43 min	43 min	27%
Thu Jul 29	5 h 14 min	1 h 26 min	1 h 26 min	18%
Fri Jul 30	5 h 20 min	2 h 39 min	2 h 39 min	10%
Sat Jul 31	5 h 25 min	4 h 18 min	3 h 18 min	4%

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

Questions

Can you see the northern lights in Viljandi in July?: On dark, clear nights with enough activity. 31 of 31 nights at Viljandi have civil darkness, and 3% of past July days reached Kp 6.
How dark is Viljandi in July?: Viljandi averages 4.1 hours of civil night a night in July 2027, from 2 h 58 min on the 1st to 5 h 25 min on the last night.
How cloudy is Viljandi in July?: NASA POWER's 2001 to 2020 climatology gives Viljandi's 1 degree cell 63% mean cloud in July, against 71% for the whole year. It is an all-hours average, not a forecast.
What is the best night in July 2027 for aurora in Viljandi?: By darkness and moon alone, Jul 31, with 3 h 18 min of moon-free darkness inside 10 PM to 2 AM at Viljandi. Activity on that date will only be known hours ahead.
Is July or August better in Viljandi?: By civil night times the clear share, July scores 1.5 hours at Viljandi and August 2.6. 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.