Fermont
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fermont clear sky chart from 2005-11-06 to 2024-01-16.

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
27%
22684
7%
74956
5%
22632
31%
22632
11%
59722

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
31%
850
12%
2838
8%
847
36%
847
10%
2258
January11th to 20thNight
27%
829
9%
2787
5%
829
32%
829
10%
2182
January21st to endNight
32%
846
14%
2894
10%
846
39%
846
12%
2219
February1st to 10thNight
36%
720
12%
2504
8%
720
43%
720
14%
1837
February11th to 20thNight
28%
702
10%
2276
6%
699
35%
699
12%
1759
February21st to endNight
34%
592
12%
1902
8%
592
39%
592
14%
1415
March1st to 10thNight
34%
719
11%
2136
8%
719
38%
719
15%
1635
March11th to 20thNight
29%
720
12%
1980
6%
720
34%
720
14%
1565
March21st to endNight
25%
792
11%
2178
5%
792
29%
792
13%
1753
April1st to 10thNight
25%
595
8%
1692
5%
595
28%
595
11%
1394
April11th to 20thNight
31%
534
12%
1598
9%
534
35%
534
17%
1177
April21st to endNight
31%
540
9%
1620
7%
540
35%
540
14%
1249
May1st to 10thNight
28%
475
6%
1385
5%
475
30%
475
11%
1135
May11th to 20thNight
32%
354
6%
1238
4%
354
37%
354
14%
924
May21st to endNight
28%
388
1%
1356
0%
388
28%
388
11%
1047
June1st to 10thNight
35%
360
0%
1260
0%
360
35%
360
14%
926
June11th to 20thNight
33%
360
0%
1260
0%
360
33%
360
12%
945
June21st to endNight
38%
360
0%
1260
0%
360
38%
360
13%
948
July1st to 10thNight
37%
350
0%
1225
0%
350
37%
350
14%
918
July11th to 20thNight
36%
348
0%
1218
0%
348
36%
348
15%
908
July21st to endNight
39%
394
3%
1300
2%
372
42%
372
12%
1007
August1st to 10thNight
44%
358
6%
1316
8%
356
45%
356
11%
1013
August11th to 20thNight
38%
523
5%
1587
3%
523
40%
523
13%
1227
August21st to endNight
36%
594
8%
1782
5%
594
38%
594
15%
1347
September1st to 10thNight
28%
540
10%
1694
7%
540
32%
540
14%
1296
September11th to 20thNight
28%
705
7%
1965
4%
705
31%
705
14%
1548
September21st to endNight
23%
720
9%
1980
3%
720
28%
720
14%
1565
October1st to 10thNight
20%
720
9%
2142
4%
720
26%
720
13%
1661
October11th to 20thNight
23%
720
7%
2240
5%
720
25%
720
8%
1898
October21st to endNight
21%
819
6%
2628
5%
819
23%
819
8%
2204
November1st to 10thNight
13%
830
4%
2593
3%
830
15%
830
5%
2285
November11th to 20thNight
12%
850
3%
2721
2%
850
14%
850
5%
2404
November21st to endNight
20%
850
3%
2850
1%
850
22%
850
6%
2471
December1st to 10thNight
20%
850
5%
2850
3%
850
22%
850
6%
2459
December11th to 20thNight
21%
850
4%
3516
3%
849
24%
849
7%
2935
December21st to endNight
26%
927
7%
5185
5%
906
31%
906
5%
4208

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
18%14%6%11%9%5%6%5%5%6%16%
74650
Night
15%14%6%11%9%5%6%5%6%7%16%
75172
TransparencyDay
68%5%10%13%5%
74332
Night
66%5%10%13%6%1
75025
SeeingDay
24%9%25%23%14%4
14961
Night
21%9%28%29%12%2
22695

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
9%15%8%14%10%5%6%6%7%10%11%
1327
11th to 20thDay
7%12%8%14%9%5%6%46%14%15%
1295
21st to endDay
5%10%7%12%11%6%7%7%9%12%13%
1460
February1st to 10thDay
49%7%11%8%5%7%9%10%11%18%
1455
11th to 20thDay
415%8%13%11%6%6%6%8%11%13%
1573
21st to endDay
5%13%7%8%10%49%6%9%10%17%
1354
March1st to 10thDay
412%7%19%12%5%6%8%6%8%13%
1819
11th to 20thDay
9%15%8%12%9%5%7%7%6%6%17%
1980
21st to endDay
7%18%7%12%10%6%7%7%5%6%16%
2178
April1st to 10thDay
14%18%7%14%10%5%7%5%4412%
2266
11th to 20thDay
11%16%5%11%9%45%45%6%24%
2312
21st to endDay
18%17%6%10%8%45%445%18%
2340
May1st to 10thDay
22%20%7%9%6%3433318%
2589
11th to 20thDay
17%14%7%11%9%4445%6%20%
2655
21st to endDay
22%16%6%10%6%45%445%18%
2919
June1st to 10thDay
24%14%5%9%6%34345%23%
2700
11th to 20thDay
23%13%48%6%35%45%7%21%
2700
21st to endDay
26%10%48%8%35%5%6%6%19%
2700
July1st to 10thDay
24%11%5%8%7%45%5%5%6%19%
2700
11th to 20thDay
26%10%48%7%46%5%5%6%18%
2700
21st to endDay
23%11%410%9%6%6%6%5%5%14%
2941
August1st to 10thDay
26%11%5%10%8%5%5%45%5%15%
2602
11th to 20thDay
26%10%310%8%46%5%5%6%18%
2304
21st to endDay
26%10%48%8%45%5%5%6%18%
2574
September1st to 10thDay
22%13%49%7%45%46%5%21%
2266
11th to 20thDay
24%14%5%11%7%45%435%17%
1994
21st to endDay
22%20%5%9%5%35%445%18%
1980
October1st to 10thDay
21%20%6%7%8%44445%17%
1818
11th to 20thDay
25%19%8%10%7%33435%14%
1718
21st to endDay
22%21%8%12%8%3443411%
1728
November1st to 10thDay
20%19%6%16%11%45%4347%
1485
11th to 20thDay
15%20%8%16%12%6%5%5%347%
1459
21st to endDay
15%17%8%14%11%8%8%5%5%47%
1330
December1st to 10thDay
8%15%7%15%12%8%7%6%5%6%9%
1330
11th to 20thDay
10%16%6%12%11%8%8%6%6%8%8%
1668
21st to endDay
7%13%8%14%11%10%8%6%6%7%12%
2431
January1st to 10thNight
8%15%7%12%10%5%9%7%7%12%10%
2838
11th to 20thNight
8%13%6%12%11%5%7%7%7%13%10%
2787
21st to endNight
5%11%7%15%11%6%7%7%8%11%13%
2894
February1st to 10thNight
49%7%9%11%7%8%8%8%12%16%
2504
11th to 20thNight
6%14%9%13%10%5%6%6%8%11%14%
2273
21st to endNight
7%12%5%11%9%6%7%9%8%9%18%
1902
March1st to 10thNight
5%12%6%13%9%5%7%7%8%9%19%
2127
11th to 20thNight
8%16%7%11%8%46%6%7%5%21%
1979
21st to endNight
8%18%8%11%8%46%5%5%5%21%
2178
April1st to 10thNight
14%17%7%12%9%46%445%18%
1692
11th to 20thNight
14%13%5%9%8%44446%28%
1598
21st to endNight
16%14%6%9%8%45%445%24%
1620
May1st to 10thNight
22%16%7%10%7%34345%18%
1385
11th to 20thNight
18%13%6%7%5%445%6%6%27%
1238
21st to endNight
21%13%7%7%7%335%5%5%23%
1356
June1st to 10thNight
19%11%5%8%7%36%45%5%27%
1260
11th to 20thNight
23%11%47%7%35%6%5%6%25%
1260
21st to endNight
24%9%28%7%46%5%5%6%25%
1260
July1st to 10thNight
21%10%5%7%7%4447%6%25%
1260
11th to 20thNight
24%8%37%7%45%5%5%5%27%
1260
21st to endNight
19%11%49%8%46%6%7%6%20%
1377
August1st to 10thNight
22%9%5%7%8%45%5%7%7%21%
1325
11th to 20thNight
22%9%48%8%47%5%46%23%
1587
21st to endNight
23%10%46%6%35%5%6%8%23%
1782
September1st to 10thNight
20%12%48%8%445%45%26%
1694
11th to 20thNight
22%12%5%8%7%445%5%6%21%
1965
21st to endNight
21%14%49%8%35%45%6%21%
1980
October1st to 10thNight
21%16%48%6%345%5%6%23%
2142
11th to 20thNight
24%18%8%9%7%3444415%
2240
21st to endNight
23%17%7%10%8%35%5%5%414%
2628
November1st to 10thNight
19%20%7%15%12%444448%
2593
11th to 20thNight
18%20%7%14%12%6%5%4447%
2721
21st to endNight
15%18%6%14%11%5%7%6%5%6%7%
2850
December1st to 10thNight
10%16%9%14%12%8%8%6%5%7%7%
2850
11th to 20thNight
13%16%7%12%11%6%7%5%5%8%8%
3531
21st to endNight
7%15%9%13%11%10%9%6%5%6%10%
5236

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
68%47%16%5%
1328
11th to 20thDay
62%39%17%9%1
1295
21st to endDay
60%5%8%15%10%1
1460
February1st to 10thDay
55%49%22%10%
1455
11th to 20thDay
64%48%15%9%
1581
21st to endDay
58%48%18%11%2
1354
March1st to 10thDay
67%48%11%7%2
1823
11th to 20thDay
67%37%16%7%2
1980
21st to endDay
68%5%7%11%8%1
2178
April1st to 10thDay
74%48%9%5%
2266
11th to 20thDay
62%38%14%12%1
2312
21st to endDay
68%411%10%7%
2340
May1st to 10thDay
72%38%11%6%
2589
11th to 20thDay
64%5%10%15%6%
2659
21st to endDay
68%49%13%5%
2919
June1st to 10thDay
64%39%16%7%1
2700
11th to 20thDay
61%5%11%16%6%
2700
21st to endDay
63%6%12%14%5%
2700
July1st to 10thDay
65%6%11%13%5%
2625
11th to 20thDay
65%6%13%14%2
2619
21st to endDay
69%8%13%10%1
2777
August1st to 10thDay
70%6%11%11%1
2587
11th to 20thDay
65%6%13%13%3
2304
21st to endDay
65%6%13%13%2
2574
September1st to 10thDay
64%5%12%14%4
2266
11th to 20thDay
70%5%12%11%2
1994
21st to endDay
69%410%14%3
1980
October1st to 10thDay
70%5%10%11%3
1818
11th to 20thDay
75%5%8%10%3
1718
21st to endDay
78%29%9%21
1728
November1st to 10thDay
81%48%6%2
1485
11th to 20thDay
80%311%5%1
1459
21st to endDay
79%39%7%2
1330
December1st to 10thDay
72%5%12%8%21
1330
11th to 20thDay
71%5%12%9%4
1668
21st to endDay
70%47%12%6%1
2431
January1st to 10thNight
67%48%14%7%1
2838
11th to 20thNight
65%5%9%14%7%1
2787
21st to endNight
63%48%15%9%2
2894
February1st to 10thNight
58%49%18%10%
2504
11th to 20thNight
63%48%15%9%
2276
21st to endNight
59%410%15%10%2
1902
March1st to 10thNight
60%410%17%7%2
2136
11th to 20thNight
63%37%14%10%2
1980
21st to endNight
65%47%13%10%1
2178
April1st to 10thNight
69%38%9%10%1
1692
11th to 20thNight
56%48%16%14%2
1598
21st to endNight
62%410%17%7%
1620
May1st to 10thNight
69%48%13%6%
1385
11th to 20thNight
57%6%10%18%9%
1239
21st to endNight
62%5%9%16%8%
1357
June1st to 10thNight
57%5%12%17%8%
1260
11th to 20thNight
58%7%11%19%5%
1260
21st to endNight
59%6%10%18%6%
1260
July1st to 10thNight
55%9%14%17%5%
1225
11th to 20thNight
57%6%15%19%3
1218
21st to endNight
60%8%15%16%1
1300
August1st to 10thNight
60%8%17%14%2
1316
11th to 20thNight
60%7%17%13%3
1587
21st to endNight
57%7%18%16%3
1782
September1st to 10thNight
59%6%12%20%3
1694
11th to 20thNight
62%5%15%16%2
1965
21st to endNight
62%5%14%16%3
1980
October1st to 10thNight
61%5%14%15%5%
2142
11th to 20thNight
74%49%11%2
2240
21st to endNight
72%410%8%5%1
2628
November1st to 10thNight
80%38%8%1
2593
11th to 20thNight
80%39%7%1
2721
21st to endNight
76%5%10%7%2
2850
December1st to 10thNight
76%49%8%2
2850
11th to 20thNight
73%410%9%5%
3532
21st to endNight
73%28%9%5%3
5236

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
8%7%28%31%20%7%
180
11th to 20thDay
13%9%31%28%15%4
170
21st to endDay
10%6%35%30%16%3
176
February1st to 10thDay
7%11%36%26%13%6%
175
11th to 20thDay
8%8%37%29%14%4
336
21st to endDay
11%9%32%28%16%4
290
March1st to 10thDay
11%10%30%27%17%5%
420
11th to 20thDay
14%11%29%27%15%4
420
21st to endDay
16%13%31%25%12%2
462
April1st to 10thDay
21%13%32%20%11%2
420
11th to 20thDay
17%10%26%27%14%6%
412
21st to endDay
22%11%22%25%13%7%
420
May1st to 10thDay
32%7%21%23%11%5%
592
11th to 20thDay
20%9%24%23%17%8%
624
21st to endDay
29%10%23%24%13%3
680
June1st to 10thDay
30%6%21%26%15%3
630
11th to 20thDay
30%7%22%22%15%5%
630
21st to endDay
27%7%24%21%15%6%
630
July1st to 10thDay
26%7%22%22%17%6%
620
11th to 20thDay
28%6%23%26%13%4
618
21st to endDay
28%5%14%26%20%7%
685
August1st to 10thDay
33%6%16%22%17%6%
550
11th to 20thDay
25%7%15%25%20%8%
439
21st to endDay
27%5%21%24%17%5%
495
September1st to 10thDay
30%13%24%21%9%3
450
11th to 20thDay
28%10%30%20%9%3
450
21st to endDay
28%16%31%15%8%3
450
October1st to 10thDay
26%16%31%18%7%2
369
11th to 20thDay
36%9%24%18%9%5%
360
21st to endDay
30%12%25%18%12%4
396
November1st to 10thDay
29%13%31%20%5%1
365
11th to 20thDay
23%12%29%24%12%1
309
21st to endDay
16%12%38%22%9%3
180
December1st to 10thDay
13%7%27%28%19%6%
180
11th to 20thDay
13%14%36%25%10%2
180
21st to endDay
15%10%34%24%14%4
198
January1st to 10thNight
14%7%29%31%16%3
850
11th to 20thNight
15%8%33%32%10%2
829
21st to endNight
10%7%32%35%14%2
846
February1st to 10thNight
7%10%31%33%16%4
720
11th to 20thNight
12%10%32%30%13%3
703
21st to endNight
11%8%31%31%15%4
592
March1st to 10thNight
11%7%31%33%16%3
720
11th to 20thNight
15%9%33%28%14%2
720
21st to endNight
16%11%33%28%10%3
792
April1st to 10thNight
23%8%30%31%8%1
595
11th to 20thNight
19%8%31%28%10%4
534
21st to endNight
25%8%25%31%9%2
540
May1st to 10thNight
28%7%23%29%11%2
475
11th to 20thNight
25%7%25%25%15%3
354
21st to endNight
25%10%26%30%10%1
389
June1st to 10thNight
24%426%37%8%1
360
11th to 20thNight
29%7%20%30%14%
360
21st to endNight
26%6%22%28%17%1
360
July1st to 10thNight
24%6%22%31%17%1
350
11th to 20thNight
24%5%23%34%12%1
348
21st to endNight
21%5%18%32%21%3
394
August1st to 10thNight
24%6%14%34%20%1
358
11th to 20thNight
24%5%19%32%19%1
523
21st to endNight
27%6%22%32%11%2
594
September1st to 10thNight
28%9%27%28%8%1
540
11th to 20thNight
27%9%29%26%8%1
705
21st to endNight
26%11%33%24%7%
720
October1st to 10thNight
30%12%30%23%5%
720
11th to 20thNight
34%8%22%25%10%2
720
21st to endNight
33%11%22%23%9%2
819
November1st to 10thNight
28%14%28%22%6%2
830
11th to 20thNight
28%12%27%22%9%1
850
21st to endNight
24%9%31%26%10%1
850
December1st to 10thNight
17%9%32%28%11%3
850
11th to 20thNight
15%10%34%29%11%1
850
21st to endNight
16%11%27%28%15%3
935
Page generated at 2024-01-13 09:37:52. Version ac07

Copyright 2024 Attilla Danko


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