Cowansville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cowansville clear sky chart from 2005-11-06 to 2024-01-27.

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
26%
22641
12%
74922
8%
22598
32%
22598
13%
56595

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%
760
6%
2649
3%
757
15%
757
4%
2311
January11th to 20thNight
13%
760
7%
2660
4%
760
17%
760
5%
2239
January21st to endNight
18%
820
9%
2868
6%
820
24%
820
8%
2299
February1st to 10thNight
11%
720
7%
2416
2%
720
19%
720
6%
2037
February11th to 20thNight
14%
703
9%
2132
3%
700
22%
700
9%
1742
February21st to endNight
19%
592
12%
1776
6%
592
27%
592
10%
1406
March1st to 10thNight
21%
720
13%
2160
9%
720
27%
720
11%
1692
March11th to 20thNight
23%
720
13%
2111
7%
720
29%
720
13%
1613
March21st to endNight
24%
792
19%
1980
7%
792
31%
792
17%
1508
April1st to 10thNight
20%
720
12%
1800
3%
720
25%
720
15%
1431
April11th to 20thNight
25%
711
13%
1775
5%
711
30%
711
18%
1349
April21st to endNight
21%
540
15%
1620
6%
540
29%
540
15%
1190
May1st to 10thNight
26%
482
15%
1562
9%
482
34%
482
15%
1127
May11th to 20thNight
30%
354
17%
1416
15%
354
40%
354
16%
927
May21st to endNight
34%
388
12%
1551
11%
388
44%
388
17%
1014
June1st to 10thNight
32%
360
11%
1440
12%
360
42%
360
14%
987
June11th to 20thNight
39%
360
11%
1440
14%
360
45%
360
17%
921
June21st to endNight
39%
360
9%
1440
12%
360
45%
360
15%
979
July1st to 10thNight
44%
350
12%
1400
15%
350
50%
350
20%
873
July11th to 20thNight
53%
348
13%
1392
20%
348
57%
348
21%
853
July21st to endNight
47%
394
13%
1486
17%
372
51%
372
19%
939
August1st to 10thNight
51%
358
15%
1422
20%
356
54%
356
22%
872
August11th to 20thNight
52%
536
16%
1600
11%
536
55%
536
25%
1064
August21st to endNight
46%
792
16%
1980
9%
792
48%
792
28%
1381
September1st to 10thNight
43%
720
13%
1800
6%
720
45%
720
28%
1245
September11th to 20thNight
48%
720
18%
1912
12%
720
50%
720
31%
1231
September21st to endNight
39%
720
20%
1980
15%
720
42%
720
25%
1345
October1st to 10thNight
32%
720
17%
2040
10%
720
39%
720
18%
1465
October11th to 20thNight
26%
720
14%
2235
8%
720
34%
720
13%
1684
October21st to endNight
20%
792
11%
2574
6%
792
26%
792
11%
1991
November1st to 10thNight
21%
740
13%
2407
7%
740
29%
740
11%
1803
November11th to 20thNight
22%
760
15%
2474
11%
760
28%
760
12%
1900
November21st to endNight
17%
760
9%
2660
6%
760
22%
760
8%
2136
December1st to 10thNight
13%
760
5%
2660
2%
760
16%
760
5%
2293
December11th to 20thNight
12%
760
7%
3256
3%
759
16%
759
4%
2750
December21st to endNight
10%
829
4%
4848
2%
817
14%
817
2%
3998

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
20%11%47%6%35%45%6%29%
74888
Night
20%13%5%8%6%34445%28%
75161
TransparencyDay
57%411%18%8%1
74593
Night
60%49%17%8%1
74990
SeeingDay
29%15%28%18%8%2
13574
Night
29%13%25%23%9%1
22649

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
19%25%7%12%6%4433414%
1517
11th to 20thDay
18%18%8%14%6%45%44414%
1520
21st to endDay
12%15%7%11%8%5%6%5%5%5%20%
1632
February1st to 10thDay
16%17%7%13%9%5%6%43317%
1544
11th to 20thDay
16%17%7%12%8%36%445%19%
1716
21st to endDay
15%18%6%9%8%4445%5%21%
1480
March1st to 10thDay
17%15%6%10%7%45%345%24%
1797
11th to 20thDay
19%14%5%8%7%34435%29%
1844
21st to endDay
21%14%5%8%6%33345%30%
2376
April1st to 10thDay
24%14%5%8%43434426%
2160
11th to 20thDay
21%12%45%424445%35%
2134
21st to endDay
26%11%45%5%44445%28%
2340
May1st to 10thDay
23%9%36%6%34447%32%
2414
11th to 20thDay
21%7%46%6%3445%6%34%
2478
21st to endDay
20%7%37%5%35%6%6%7%32%
2725
June1st to 10thDay
28%6%345%35%5%6%7%29%
2520
11th to 20thDay
19%5%35%6%35%5%6%7%37%
2520
21st to endDay
24%7%36%5%35%5%47%29%
2520
July1st to 10thDay
16%6%35%5%35%6%5%10%37%
2520
11th to 20thDay
16%6%36%6%45%6%7%9%34%
2520
21st to endDay
16%8%25%5%45%6%6%8%34%
2744
August1st to 10thDay
17%6%37%6%46%5%6%8%33%
2506
11th to 20thDay
16%6%25%6%45%5%6%9%36%
2281
21st to endDay
17%6%25%5%45%45%9%38%
2376
September1st to 10thDay
18%7%245%345%5%6%40%
2160
11th to 20thDay
19%5%24434447%45%
2048
21st to endDay
19%6%25%4345%6%9%37%
1980
October1st to 10thDay
26%9%26%5%45%5%5%6%28%
1918
11th to 20thDay
23%10%36%5%35%5%6%6%28%
1724
21st to endDay
29%15%36%5%3343424%
1782
November1st to 10thDay
21%14%45%5%345%5%429%
1671
11th to 20thDay
20%16%6%9%7%3434424%
1703
21st to endDay
21%18%6%10%6%3346%5%19%
1520
December1st to 10thDay
24%21%8%10%7%3433415%
1520
11th to 20thDay
21%19%7%10%5%3444420%
1906
21st to endDay
25%18%6%11%6%35%43415%
2772
January1st to 10thNight
20%20%8%11%8%4444414%
2649
11th to 20thNight
17%18%8%13%8%45%43317%
2660
21st to endNight
16%15%7%11%8%5%5%445%22%
2868
February1st to 10thNight
16%17%6%15%8%44445%16%
2416
11th to 20thNight
15%16%7%12%8%34446%20%
2130
21st to endNight
16%16%7%10%7%3433426%
1776
March1st to 10thNight
18%16%6%9%7%35%34426%
2150
11th to 20thNight
20%15%47%6%34445%28%
2110
21st to endNight
20%14%5%7%5%3334333%
1980
April1st to 10thNight
25%12%5%7%5%3445%427%
1800
11th to 20thNight
25%10%35%6%33345%34%
1775
21st to endNight
24%11%46%433446%32%
1620
May1st to 10thNight
24%9%37%5%345%46%31%
1562
11th to 20thNight
22%7%45%5%3435%6%36%
1415
21st to endNight
19%7%25%5%45%5%5%6%37%
1550
June1st to 10thNight
28%6%35%425%46%8%30%
1440
11th to 20thNight
21%6%25%5%3445%9%37%
1440
21st to endNight
19%8%26%6%26%47%8%32%
1440
July1st to 10thNight
14%6%35%6%36%5%6%8%38%
1440
11th to 20thNight
12%5%35%5%46%6%7%9%38%
1440
21st to endNight
15%6%25%5%46%5%6%8%37%
1574
August1st to 10thNight
17%5%246%345%6%9%38%
1432
11th to 20thNight
15%6%36%6%45%46%7%38%
1600
21st to endNight
16%7%35%435%5%5%7%41%
1980
September1st to 10thNight
18%6%26%5%3445%7%41%
1800
11th to 20thNight
16%5%25%4345%47%45%
1912
21st to endNight
21%6%2443335%6%42%
1980
October1st to 10thNight
22%7%36%6%245%46%35%
2040
11th to 20thNight
24%10%37%6%35%345%29%
2235
21st to endNight
29%12%36%5%35%445%25%
2574
November1st to 10thNight
22%12%47%5%36%346%28%
2407
11th to 20thNight
22%14%48%6%34445%27%
2474
21st to endNight
22%18%6%9%5%3433423%
2660
December1st to 10thNight
24%22%7%10%6%3334414%
2660
11th to 20thNight
24%19%7%10%6%3433317%
3288
21st to endNight
26%19%6%10%6%3333417%
4884

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
78%37%10%2
1518
11th to 20thDay
73%5%7%9%6%
1520
21st to endDay
68%49%12%5%1
1632
February1st to 10thDay
75%36%12%41
1544
11th to 20thDay
71%210%11%5%1
1725
21st to endDay
68%38%12%7%1
1480
March1st to 10thDay
66%39%14%6%2
1800
11th to 20thDay
61%411%13%10%1
1844
21st to endDay
61%37%18%10%2
2376
April1st to 10thDay
64%38%16%8%1
2160
11th to 20thDay
55%47%19%13%1
2134
21st to endDay
60%48%16%9%3
2340
May1st to 10thDay
54%48%19%13%2
2414
11th to 20thDay
52%410%20%13%2
2482
21st to endDay
50%6%12%18%12%1
2725
June1st to 10thDay
55%412%19%9%1
2520
11th to 20thDay
46%6%11%24%11%2
2520
21st to endDay
56%5%11%19%8%1
2520
July1st to 10thDay
44%6%14%26%10%
2450
11th to 20thDay
46%6%14%28%6%
2445
21st to endDay
48%6%15%23%7%
2591
August1st to 10thDay
49%6%16%23%5%
2492
11th to 20thDay
45%5%18%22%10%
2281
21st to endDay
45%6%13%25%12%
2376
September1st to 10thDay
44%5%13%25%11%1
2160
11th to 20thDay
41%311%32%13%
2048
21st to endDay
45%6%14%25%9%1
1980
October1st to 10thDay
57%5%11%18%8%
1918
11th to 20thDay
56%5%15%16%7%
1724
21st to endDay
67%39%14%5%1
1782
November1st to 10thDay
59%5%11%17%8%1
1671
11th to 20thDay
66%311%11%7%1
1703
21st to endDay
68%5%13%10%4
1520
December1st to 10thDay
75%410%8%2
1520
11th to 20thDay
70%38%14%5%
1906
21st to endDay
76%48%9%3
2772
January1st to 10thNight
77%5%6%9%3
2649
11th to 20thNight
74%47%11%4
2660
21st to endNight
69%48%12%7%1
2868
February1st to 10thNight
74%46%11%5%
2416
11th to 20thNight
69%38%14%6%
2132
21st to endNight
66%37%13%10%1
1776
March1st to 10thNight
64%48%16%7%1
2160
11th to 20thNight
62%39%16%10%2
2111
21st to endNight
58%36%19%11%3
1980
April1st to 10thNight
62%37%15%11%1
1800
11th to 20thNight
56%47%19%14%
1775
21st to endNight
55%5%8%18%12%3
1620
May1st to 10thNight
55%5%5%17%14%3
1562
11th to 20thNight
51%39%19%16%2
1416
21st to endNight
48%5%11%21%13%2
1551
June1st to 10thNight
54%410%22%9%1
1440
11th to 20thNight
47%6%10%22%12%3
1440
21st to endNight
49%8%13%20%10%
1440
July1st to 10thNight
43%7%13%23%14%1
1400
11th to 20thNight
40%8%14%29%9%
1392
21st to endNight
45%6%14%26%9%
1486
August1st to 10thNight
41%7%19%25%9%
1422
11th to 20thNight
43%6%16%23%11%
1600
21st to endNight
44%5%14%25%11%1
1980
September1st to 10thNight
44%5%12%27%12%1
1800
11th to 20thNight
40%415%31%11%
1912
21st to endNight
45%5%11%26%13%1
1980
October1st to 10thNight
51%5%10%22%11%
2040
11th to 20thNight
59%5%10%19%7%
2235
21st to endNight
63%49%14%8%1
2574
November1st to 10thNight
60%410%18%8%1
2407
11th to 20thNight
62%49%15%8%2
2474
21st to endNight
68%410%14%4
2660
December1st to 10thNight
77%47%9%3
2660
11th to 20thNight
75%46%10%4
3288
21st to endNight
75%47%12%2
4884

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
32%17%32%12%7%
180
11th to 20thDay
33%24%27%12%31
180
21st to endDay
26%21%32%16%4
188
February1st to 10thDay
43%28%23%5%1
206
11th to 20thDay
36%24%28%9%2
384
21st to endDay
36%17%27%18%1
346
March1st to 10thDay
34%19%27%17%3
420
11th to 20thDay
35%19%28%13%5%1
420
21st to endDay
37%18%22%15%7%2
462
April1st to 10thDay
37%16%26%14%6%1
420
11th to 20thDay
38%17%22%15%6%2
412
21st to endDay
34%17%28%13%6%2
420
May1st to 10thDay
33%18%27%13%7%2
423
11th to 20thDay
26%16%31%17%8%2
447
21st to endDay
22%15%34%21%7%1
485
June1st to 10thDay
32%13%32%15%7%1
450
11th to 20thDay
23%10%32%24%9%2
450
21st to endDay
26%12%35%17%7%3
450
July1st to 10thDay
18%9%31%29%11%2
445
11th to 20thDay
18%10%35%25%10%3
444
21st to endDay
22%8%32%28%8%2
488
August1st to 10thDay
20%9%28%27%15%1
446
11th to 20thDay
19%7%29%25%14%5%
439
21st to endDay
22%13%23%24%13%6%
495
September1st to 10thDay
20%10%29%22%14%6%
450
11th to 20thDay
22%12%22%21%16%8%
450
21st to endDay
21%12%25%26%12%5%
450
October1st to 10thDay
29%16%22%18%12%4
450
11th to 20thDay
34%16%23%18%8%1
412
21st to endDay
42%13%23%17%4
396
November1st to 10thDay
35%16%28%15%5%1
365
11th to 20thDay
36%20%23%15%6%1
363
21st to endDay
35%20%29%14%2
180
December1st to 10thDay
38%17%28%12%41
180
11th to 20thDay
35%23%31%8%21
180
21st to endDay
42%20%24%10%4
198
January1st to 10thNight
34%19%27%16%3
760
11th to 20thNight
30%21%27%17%5%
760
21st to endNight
25%17%30%22%6%
820
February1st to 10thNight
29%18%31%18%4
720
11th to 20thNight
26%21%31%19%3
703
21st to endNight
30%16%30%21%3
592
March1st to 10thNight
32%14%28%23%4
720
11th to 20thNight
32%17%24%21%6%
720
21st to endNight
30%17%24%20%8%1
792
April1st to 10thNight
33%14%28%21%4
720
11th to 20thNight
33%14%23%21%8%1
711
21st to endNight
33%14%28%19%6%
540
May1st to 10thNight
27%12%28%24%9%1
482
11th to 20thNight
27%8%28%28%8%1
354
21st to endNight
23%7%30%32%7%1
389
June1st to 10thNight
31%7%24%29%8%1
360
11th to 20thNight
22%6%26%31%14%1
360
21st to endNight
22%6%23%38%10%1
360
July1st to 10thNight
16%431%35%13%1
350
11th to 20thNight
13%423%40%19%1
348
21st to endNight
17%5%23%40%14%
394
August1st to 10thNight
19%417%37%22%1
358
11th to 20thNight
18%5%18%37%20%2
536
21st to endNight
19%6%22%32%20%1
792
September1st to 10thNight
21%7%23%31%16%2
720
11th to 20thNight
22%7%19%30%21%2
720
21st to endNight
25%10%24%24%16%2
720
October1st to 10thNight
27%11%24%26%11%2
720
11th to 20thNight
31%13%24%22%9%1
720
21st to endNight
39%13%25%19%5%
792
November1st to 10thNight
33%14%27%18%7%1
740
11th to 20thNight
32%17%24%16%9%1
760
21st to endNight
34%21%22%16%6%1
760
December1st to 10thNight
39%17%24%15%4
760
11th to 20thNight
34%18%26%17%5%1
760
21st to endNight
39%17%24%17%3
836
Page generated at 2024-01-24 09:37:31. Version ac07

Copyright 2024 Attilla Danko


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