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Great Falls

47.500° N   111.301° W  ·  1014 M
43 /100
PEAK
Marginal, but there is a 1 hour gap from 01:00.
BEST WINDOW 01:00–02:00 · ASTRO DARK 23:00–05:00 · MOON 1%
Transparency
0.33
Seeing
0.80
Cloud
31%
Moon
1%

Fair tonight

Hour by hour, local to Great Falls. Colour encodes the score and nothing else; every other measurement is luminance.

Sky state
Lighter = daylight and twilight  ·  unshaded = astronomical dark
Score
21
22
23
00
01
02
03
04
05
06
0
18
5
34
43
3
15
13
10
0
BEST WINDOW
Low cloud
11%
21%
82%
2%
10%
92%
47%
20%
31%
94%
Mid cloud
23%
28%
57%
41%
18%
37%
52%
79%
59%
100%
High cloud
8%
6%
13%
10%
7%
9%
16%
8%
2%
0%
Transparency
0.81
0.33
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.21
Seeing
0.52
0.51
0.61
0.65
0.72
0.75
0.77
0.80
0.80
0.76
Moon clear
0%
down
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down
down
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down
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Inspect

Cloud tracks show clear sky — a longer bar is better. The figure inside each track is the raw measurement.

Why this hour scored what it did
21 Clouded out · 0/100
Starting from
100
Cloud
−33
Transparency
−5
Seeing
−7
Moonlight
−0
Darkness
−55
Score
0
CLOUD 36% LOW 11% MID 23% HIGH 8% SUN -3.4° MOON 0.1° / 0% WIND 7 TEMP 19°
Excellent 75+ Good 55+ Fair 35+ Poor 15+ Not worth it Seeing is estimated from surface wind — see how we score.

What are you doing tonight?

The same forecast, weighted for the target. Planetary work barely cares about moonlight; long exposures die on high cloud a visual observer would never notice.

SET UP 23:30 · OBSERVE 00:00–02:00 · 2H · MEAN 41

Darkness and moonlight dominate. Faint fuzzies need a genuinely dark sky more than they need steady air.

2123010305
CLOUD BREAKS 00:00CLOUD RETURNS 02:00
SET UP 23:30 · OBSERVE 00:00–02:00 · 2H · MEAN 46

Seeing is everything and moonlight is irrelevant. Bright targets punch through twilight, so darkness barely counts.

2123010305
CLOUD BREAKS 00:00CLOUD RETURNS 02:00MOONLIGHT IGNORED FOR THIS TARGET
SET UP 00:30 · OBSERVE 01:00–02:00 · 1H · MEAN 41

Tolerates soft seeing, but high cloud wrecks a wide frame and moonlight raises the background everywhere.

2123010305
CLOUD BREAKS 01:00CLOUD RETURNS 02:00
NO USABLE WINDOW FOR THIS TARGET TONIGHT

Needs conditions to hold still for hours. Sustained transparency matters more than any single good hour.

2123010305
CONDITIONS STAY BELOW THE USABLE THRESHOLD
SET UP 23:30 · OBSERVE 00:00–02:00 · 2H · MEAN 42

Naked eye, whole sky. Total cloud and moonlight are the only things that count.

2123010305
CLOUD BREAKS 00:00CLOUD RETURNS 02:00
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The next week of nights

Tonight · 12 Aug
43
Fair
MOON 0%
01:00–02:00
Tomorrow · 13 Aug
2
Clouded out
MOON 3%
Friday · 14 Aug
44
Fair
MOON 7%
23:00–00:00
Saturday · 15 Aug
79
Excellent
MOON 15%
00:00–01:00
Sunday · 16 Aug
50
Fair
MOON 23%
00:00–01:00
Monday · 17 Aug
40
Fair
MOON 32%
00:00–01:00
Tuesday · 18 Aug
39
Fair
MOON 42%
00:00–01:00
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Nearby locations

About this forecast

Conditions for Great Falls, Montana, United States are computed from the MET Norway forecast model for these exact coordinates, combined with sun and moon positions we calculate directly. The score weighs cloud cover by layer, atmospheric transparency, estimated seeing, moonlight and how dark the sky actually gets. Read the full method →