Mount Forest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Forest clear sky chart from 2005-11-06 to 2024-02-05.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
30%
23227
11%
80269
8%
23130
35%
23130
13%
61003

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
11%
941
3%
4708
2%
925
15%
925
4%
4175
January11th to 20thNight
12%
755
2%
4120
2%
740
15%
740
2%
3804
January21st to endNight
16%
832
3%
4530
3%
814
19%
814
3%
3943
February1st to 10thNight
12%
739
5%
2399
2%
739
17%
739
6%
2042
February11th to 20thNight
16%
700
8%
2275
3%
700
22%
700
9%
1844
February21st to endNight
16%
592
10%
1821
3%
592
23%
592
9%
1454
March1st to 10thNight
19%
720
13%
2019
6%
720
26%
720
15%
1529
March11th to 20thNight
21%
720
16%
1980
8%
720
29%
720
16%
1471
March21st to endNight
28%
792
16%
2178
8%
792
34%
792
18%
1596
April1st to 10thNight
24%
720
12%
1884
4%
720
29%
720
17%
1447
April11th to 20thNight
33%
579
18%
1643
10%
579
38%
579
22%
1153
April21st to endNight
30%
540
15%
1620
7%
540
35%
540
17%
1163
May1st to 10thNight
37%
540
15%
1620
9%
540
43%
540
22%
1116
May11th to 20thNight
41%
442
19%
1504
15%
442
50%
442
22%
954
May21st to endNight
49%
388
17%
1551
16%
388
59%
388
27%
873
June1st to 10thNight
42%
360
14%
1412
14%
360
52%
360
23%
831
June11th to 20thNight
45%
360
17%
1260
18%
360
53%
360
25%
764
June21st to endNight
49%
360
16%
1260
17%
360
55%
360
25%
767
July1st to 10thNight
66%
350
19%
1225
24%
350
70%
350
36%
644
July11th to 20thNight
56%
402
18%
1366
21%
402
61%
402
30%
800
July21st to endNight
57%
591
16%
1672
13%
558
59%
558
31%
1021
August1st to 10thNight
60%
537
18%
1600
15%
534
62%
534
31%
990
August11th to 20thNight
62%
534
22%
1598
14%
534
66%
534
34%
948
August21st to endNight
53%
615
19%
1803
13%
615
56%
615
29%
1161
September1st to 10thNight
53%
720
16%
1802
10%
720
54%
720
32%
1208
September11th to 20thNight
52%
720
24%
1980
16%
720
56%
720
34%
1217
September21st to endNight
45%
720
18%
1980
13%
720
49%
720
25%
1352
October1st to 10thNight
38%
720
15%
2146
13%
720
43%
720
20%
1512
October11th to 20thNight
28%
720
12%
2160
7%
720
34%
720
14%
1641
October21st to endNight
20%
792
11%
2402
7%
792
27%
792
11%
1930
November1st to 10thNight
27%
740
14%
2444
10%
740
33%
740
14%
1785
November11th to 20thNight
19%
760
10%
2660
7%
760
25%
760
10%
2071
November21st to endNight
18%
760
7%
2660
6%
760
22%
760
8%
2160
December1st to 10thNight
11%
760
3%
2660
2%
760
12%
760
4%
2339
December11th to 20thNight
9%
760
4%
3264
1%
759
13%
759
4%
2706
December21st to endNight
8%
946
2%
5063
0%
935
11%
935
2%
4592

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
16%12%5%9%7%45%45%6%27%
78344
Night
16%13%6%10%7%45%446%26%
80485
TransparencyDay
56%6%11%17%9%1
78052
Night
59%6%10%15%9%1
80312
SeeingDay
21%13%29%22%12%4
13943
Night
21%11%30%26%10%1
23256

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
14%19%13%14%9%4432414%
2244
11th to 20thDay
11%21%10%18%13%8%5%3236%
2821
21st to endDay
17%22%10%16%8%45%33410%
3124
February1st to 10thDay
14%18%8%17%12%5%5%43311%
1656
11th to 20thDay
14%14%8%16%12%345%5%414%
1573
21st to endDay
15%19%8%12%10%35%35%416%
1431
March1st to 10thDay
14%13%5%12%10%44345%26%
1937
11th to 20thDay
12%13%8%11%6%46%436%28%
1980
21st to endDay
17%13%5%8%7%35%5%5%6%28%
2178
April1st to 10thDay
18%15%6%9%6%3445%5%25%
2075
11th to 20thDay
19%12%45%4335%5%6%35%
2283
21st to endDay
21%11%5%6%5%2435%7%31%
2340
May1st to 10thDay
18%10%37%5%3446%7%34%
2340
11th to 20thDay
17%9%36%6%34446%38%
2388
21st to endDay
14%6%35%436%5%5%8%41%
2725
June1st to 10thDay
15%6%36%5%35%5%5%7%38%
2543
11th to 20thDay
13%6%25%5%35%5%6%9%40%
2700
21st to endDay
16%6%35%5%35%5%6%8%39%
2700
July1st to 10thDay
11%425%5%35%5%7%9%44%
2700
11th to 20thDay
12%7%36%5%46%5%7%9%37%
2544
21st to endDay
11%6%36%6%36%6%6%9%37%
2547
August1st to 10thDay
11%6%25%7%46%6%7%11%34%
2327
11th to 20thDay
12%6%27%6%47%7%7%9%34%
2303
21st to endDay
13%7%26%6%45%5%7%8%37%
2534
September1st to 10thDay
14%8%37%6%35%46%8%37%
2156
11th to 20thDay
13%6%36%5%3446%9%40%
1980
21st to endDay
17%8%37%6%345%6%7%33%
1980
October1st to 10thDay
21%10%37%6%245%5%6%31%
1814
11th to 20thDay
25%14%47%6%445%45%21%
1800
21st to endDay
27%17%5%7%6%345%46%16%
1949
November1st to 10thDay
17%18%47%6%44447%25%
1633
11th to 20thDay
18%17%6%10%6%45%45%6%18%
1520
21st to endDay
19%21%10%9%6%25%6%46%13%
1520
December1st to 10thDay
15%24%12%17%7%343338%
1520
11th to 20thDay
18%20%9%13%8%34445%12%
1906
21st to endDay
25%22%9%13%6%333339%
2573
January1st to 10thNight
15%20%10%20%10%443338%
4708
11th to 20thNight
12%15%9%20%16%7%6%4236%
4120
21st to endNight
18%17%10%15%10%5%5%4449%
4532
February1st to 10thNight
15%19%8%12%11%5%5%44413%
2399
11th to 20thNight
14%15%9%14%9%45%445%17%
2273
21st to endNight
16%13%7%13%8%45%5%5%5%20%
1821
March1st to 10thNight
14%11%6%11%8%45%45%5%28%
2009
11th to 20thNight
13%13%6%9%7%35%45%6%30%
1979
21st to endNight
16%13%5%7%6%35%435%33%
2178
April1st to 10thNight
20%12%5%8%5%34446%28%
1884
11th to 20thNight
17%11%45%5%345%47%36%
1643
21st to endNight
15%12%48%7%445%5%5%31%
1620
May1st to 10thNight
15%9%36%6%25%5%6%7%36%
1620
11th to 20thNight
16%8%25%435%5%5%6%42%
1503
21st to endNight
10%435%5%45%5%6%8%48%
1550
June1st to 10thNight
13%5%36%6%3445%8%42%
1412
11th to 20thNight
13%5%25%6%45%5%6%9%40%
1260
21st to endNight
13%7%34425%5%5%8%44%
1260
July1st to 10thNight
6%5%24325%45%8%54%
1260
11th to 20thNight
10%6%25%4345%6%8%47%
1409
21st to endNight
9%5%35%6%346%6%7%46%
1771
August1st to 10thNight
11%5%245%35%5%6%8%46%
1611
11th to 20thNight
8%6%244345%7%9%48%
1598
21st to endNight
11%7%26%5%45%5%46%44%
1803
September1st to 10thNight
11%6%35%5%35%5%5%7%44%
1802
11th to 20thNight
13%5%345%3346%6%48%
1980
21st to endNight
14%9%36%6%3445%7%39%
1980
October1st to 10thNight
18%9%36%6%3445%7%35%
2146
11th to 20thNight
24%11%5%6%5%35%45%6%26%
2160
21st to endNight
24%15%47%6%35%45%6%21%
2402
November1st to 10thNight
18%12%48%6%45%446%28%
2444
11th to 20thNight
17%16%6%9%8%35%5%6%5%21%
2660
21st to endNight
20%18%7%9%7%35%45%6%17%
2660
December1st to 10thNight
19%22%10%13%6%4434410%
2660
11th to 20thNight
14%20%10%14%7%4444415%
3288
21st to endNight
24%21%8%14%7%45%3446%
5080

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
75%49%7%4
2245
11th to 20thDay
86%44331
2821
21st to endDay
80%47%5%3
3124
February1st to 10thDay
78%5%49%31
1656
11th to 20thDay
71%5%7%10%5%1
1582
21st to endDay
71%5%8%11%5%1
1431
March1st to 10thDay
62%412%12%9%1
1940
11th to 20thDay
59%5%9%15%10%2
1980
21st to endDay
57%5%9%16%11%2
2178
April1st to 10thDay
61%5%9%16%9%
2075
11th to 20thDay
51%6%11%19%13%1
2283
21st to endDay
54%5%10%17%11%2
2340
May1st to 10thDay
50%5%10%21%13%1
2340
11th to 20thDay
47%6%10%24%12%1
2392
21st to endDay
40%6%15%22%14%2
2725
June1st to 10thDay
44%7%11%22%15%1
2543
11th to 20thDay
40%7%12%25%15%1
2700
21st to endDay
41%8%14%24%13%1
2700
July1st to 10thDay
35%8%13%24%19%2
2626
11th to 20thDay
41%9%13%26%11%1
2464
21st to endDay
42%8%13%23%13%1
2405
August1st to 10thDay
42%9%14%23%9%2
2314
11th to 20thDay
44%9%15%22%10%
2303
21st to endDay
43%7%14%24%11%1
2534
September1st to 10thDay
44%7%13%23%10%2
2156
11th to 20thDay
39%7%13%29%11%
1980
21st to endDay
48%8%13%23%8%1
1980
October1st to 10thDay
53%6%11%17%12%2
1814
11th to 20thDay
63%6%10%14%6%1
1800
21st to endDay
69%7%9%10%5%
1949
November1st to 10thDay
59%7%10%16%7%
1633
11th to 20thDay
64%7%11%10%6%1
1520
21st to endDay
70%8%9%10%3
1520
December1st to 10thDay
79%7%7%6%2
1520
11th to 20thDay
75%5%9%7%3
1906
21st to endDay
82%5%6%5%1
2573
January1st to 10thNight
80%5%7%6%3
4708
11th to 20thNight
85%5%5%32
4120
21st to endNight
77%6%8%5%31
4532
February1st to 10thNight
73%5%8%11%21
2399
11th to 20thNight
67%6%9%12%6%
2275
21st to endNight
64%6%9%12%8%
1821
March1st to 10thNight
56%6%11%16%9%1
2019
11th to 20thNight
54%6%10%17%11%2
1980
21st to endNight
54%5%8%17%14%2
2178
April1st to 10thNight
57%5%8%16%13%1
1884
11th to 20thNight
49%5%8%20%16%2
1643
21st to endNight
52%6%9%16%14%2
1620
May1st to 10thNight
46%7%9%22%15%2
1620
11th to 20thNight
42%7%9%23%16%3
1504
21st to endNight
32%8%14%26%16%3
1551
June1st to 10thNight
39%6%11%26%17%1
1412
11th to 20thNight
38%7%12%24%17%2
1260
21st to endNight
38%7%12%27%16%1
1260
July1st to 10thNight
27%7%12%28%24%3
1225
11th to 20thNight
34%7%13%29%17%1
1366
21st to endNight
34%8%15%26%16%2
1672
August1st to 10thNight
34%8%15%29%13%1
1600
11th to 20thNight
31%8%15%29%15%1
1598
21st to endNight
40%6%13%26%14%1
1803
September1st to 10thNight
37%8%12%27%14%2
1802
11th to 20thNight
35%5%13%30%17%1
1980
21st to endNight
44%7%13%25%11%
1980
October1st to 10thNight
49%7%10%19%14%1
2146
11th to 20thNight
57%7%12%17%7%
2160
21st to endNight
63%7%10%12%8%
2402
November1st to 10thNight
54%8%12%17%9%1
2444
11th to 20thNight
62%7%12%13%5%2
2660
21st to endNight
66%8%12%11%31
2660
December1st to 10thNight
76%7%8%7%2
2660
11th to 20thNight
72%6%12%8%2
3288
21st to endNight
81%7%7%5%1
5080

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
24%17%37%17%42
191
11th to 20thDay
20%24%37%14%41
270
21st to endDay
25%16%36%18%4
297
February1st to 10thDay
28%19%40%10%4
252
11th to 20thDay
23%21%44%10%1
240
21st to endDay
32%30%29%8%1
198
March1st to 10thDay
26%17%36%14%7%1
380
11th to 20thDay
23%16%35%18%6%1
420
21st to endDay
29%13%33%18%7%1
462
April1st to 10thDay
23%18%34%18%6%1
420
11th to 20thDay
27%17%26%15%10%5%
412
21st to endDay
28%12%31%20%7%2
420
May1st to 10thDay
24%12%27%24%11%3
423
11th to 20thDay
21%10%27%24%14%4
447
21st to endDay
18%7%23%30%16%7%
485
June1st to 10thDay
15%12%27%30%14%3
473
11th to 20thDay
15%10%30%28%14%3
630
21st to endDay
17%9%30%29%13%3
630
July1st to 10thDay
10%7%24%27%24%8%
621
11th to 20thDay
15%8%25%27%17%8%
521
21st to endDay
11%5%29%34%16%6%
488
August1st to 10thDay
12%6%22%27%21%12%
446
11th to 20thDay
14%420%27%22%13%
439
21st to endDay
15%7%23%27%18%10%
495
September1st to 10thDay
15%8%26%24%16%10%
450
11th to 20thDay
11%6%22%27%22%11%
450
21st to endDay
15%14%26%24%14%7%
450
October1st to 10thDay
23%11%26%20%14%4
450
11th to 20thDay
28%19%30%18%4
450
21st to endDay
34%16%28%17%5%
464
November1st to 10thDay
29%17%30%18%6%
251
11th to 20thDay
26%23%35%11%33
180
21st to endDay
28%18%39%13%1
180
December1st to 10thDay
31%26%27%14%2
180
11th to 20thDay
26%29%31%12%3
180
21st to endDay
36%15%37%10%2
198
January1st to 10thNight
23%17%38%17%5%1
949
11th to 20thNight
27%17%30%21%4
760
21st to endNight
19%12%39%24%6%
836
February1st to 10thNight
23%18%37%19%3
739
11th to 20thNight
22%15%37%22%4
703
21st to endNight
25%17%34%20%3
592
March1st to 10thNight
19%15%39%19%7%1
720
11th to 20thNight
21%15%37%20%6%1
720
21st to endNight
23%12%32%23%9%1
792
April1st to 10thNight
25%13%31%26%4
720
11th to 20thNight
21%14%29%23%11%2
579
21st to endNight
21%11%32%27%9%1
540
May1st to 10thNight
18%7%29%30%14%1
540
11th to 20thNight
20%5%29%33%12%1
442
21st to endNight
12%5%28%37%18%
389
June1st to 10thNight
14%430%38%13%
360
11th to 20thNight
15%5%29%37%14%
360
21st to endNight
16%6%24%38%15%1
360
July1st to 10thNight
7%417%49%23%1
350
11th to 20thNight
11%5%22%38%23%1
402
21st to endNight
11%320%45%20%1
591
August1st to 10thNight
12%218%38%29%1
537
11th to 20thNight
10%119%35%29%4
534
21st to endNight
14%422%33%26%2
615
September1st to 10thNight
13%6%24%33%19%5%
720
11th to 20thNight
14%423%32%22%5%
720
21st to endNight
18%8%23%32%16%4
720
October1st to 10thNight
23%7%26%28%14%2
720
11th to 20thNight
28%12%26%26%7%2
720
21st to endNight
31%12%30%23%3
792
November1st to 10thNight
24%12%29%26%7%1
740
11th to 20thNight
24%18%32%18%6%1
760
21st to endNight
27%15%33%21%3
760
December1st to 10thNight
30%16%33%17%4
760
11th to 20thNight
23%19%39%16%31
760
21st to endNight
31%16%35%17%2
954
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