Lac Gagnon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac Gagnon clear sky chart from 2005-11-06 to 2024-03-06.

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
28%
22685
12%
80902
7%
22594
34%
22594
13%
59332

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
12%
755
6%
4405
1%
737
19%
737
4%
3344
January11th to 20thNight
17%
756
6%
4423
3%
740
23%
740
4%
3371
January21st to endNight
21%
831
7%
4869
6%
814
29%
814
6%
3917
February1st to 10thNight
17%
760
10%
2470
4%
760
25%
760
10%
1935
February11th to 20thNight
16%
743
12%
2382
5%
740
27%
740
11%
1820
February21st to endNight
22%
628
12%
1884
6%
628
30%
628
13%
1412
March1st to 10thNight
19%
743
13%
2227
7%
743
27%
743
12%
1726
March11th to 20thNight
21%
720
14%
2021
6%
720
30%
720
15%
1517
March21st to endNight
25%
792
19%
2034
7%
792
34%
792
19%
1471
April1st to 10thNight
24%
720
14%
1800
5%
720
28%
720
18%
1354
April11th to 20thNight
28%
711
17%
1775
6%
711
34%
711
22%
1267
April21st to endNight
27%
578
15%
1658
7%
578
33%
578
16%
1201
May1st to 10thNight
30%
360
17%
1440
13%
360
42%
360
16%
955
May11th to 20thNight
34%
354
20%
1416
19%
354
46%
354
17%
913
May21st to endNight
32%
389
12%
1551
9%
388
45%
388
18%
985
June1st to 10thNight
35%
360
8%
1440
8%
360
44%
360
17%
961
June11th to 20thNight
40%
360
11%
1440
12%
360
48%
360
18%
915
June21st to endNight
44%
360
9%
1440
13%
360
47%
360
17%
953
July1st to 10thNight
50%
350
12%
1400
15%
350
57%
350
24%
816
July11th to 20thNight
52%
348
13%
1392
19%
348
55%
348
22%
838
July21st to endNight
51%
394
12%
1486
13%
372
56%
372
21%
893
August1st to 10thNight
51%
358
12%
1422
13%
356
55%
356
20%
896
August11th to 20thNight
55%
523
17%
1587
13%
523
59%
523
29%
1021
August21st to endNight
44%
792
17%
1980
7%
792
48%
792
30%
1343
September1st to 10thNight
43%
720
15%
1800
6%
720
46%
720
31%
1204
September11th to 20thNight
47%
720
19%
1822
11%
720
50%
720
32%
1190
September21st to endNight
41%
720
19%
2002
13%
720
46%
720
27%
1333
October1st to 10thNight
32%
720
17%
2160
11%
720
40%
720
19%
1512
October11th to 20thNight
25%
720
11%
2160
6%
720
32%
720
14%
1631
October21st to endNight
23%
792
10%
2563
6%
792
30%
792
12%
1965
November1st to 10thNight
25%
740
13%
2407
8%
740
32%
740
14%
1768
November11th to 20thNight
20%
760
13%
2641
9%
760
26%
760
10%
2021
November21st to endNight
18%
760
7%
2660
4%
760
23%
760
7%
2165
December1st to 10thNight
16%
760
7%
2660
3%
760
20%
760
6%
2216
December11th to 20thNight
15%
760
10%
3242
4%
759
22%
759
7%
2548
December21st to endNight
14%
828
6%
4843
3%
817
20%
817
4%
3955

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%11%48%7%35%45%6%29%
78311
Night
17%12%5%8%6%3445%6%29%
81202
TransparencyDay
55%7%11%17%9%1
78016
Night
56%6%12%17%8%1
81031
SeeingDay
24%18%30%19%8%2
13492
Night
23%14%29%24%9%1
22707

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
15%18%9%14%9%4443416%
2517
11th to 20thDay
13%15%7%17%11%33345%19%
2520
21st to endDay
11%16%8%12%10%5%6%5%45%18%
2781
February1st to 10thDay
12%16%8%11%11%45%446%20%
1710
11th to 20thDay
12%18%6%12%6%35%346%25%
1685
21st to endDay
16%16%5%9%8%46%335%25%
1570
March1st to 10thDay
14%14%6%10%8%34445%27%
1847
11th to 20thDay
15%14%5%9%6%46%45%5%27%
1935
21st to endDay
17%10%5%8%5%33446%35%
2322
April1st to 10thDay
22%14%47%5%33446%29%
2160
11th to 20thDay
22%10%37%6%3434434%
2134
21st to endDay
21%11%48%5%4445%5%30%
2316
May1st to 10thDay
22%10%36%6%24446%32%
2520
11th to 20thDay
19%8%37%6%345%5%6%35%
2478
21st to endDay
18%7%37%6%35%5%5%7%35%
2725
June1st to 10thDay
23%8%37%6%45%5%5%6%29%
2520
11th to 20thDay
16%5%36%6%45%5%6%9%35%
2520
21st to endDay
20%7%36%7%45%6%6%7%29%
2520
July1st to 10thDay
15%6%26%6%46%5%6%9%36%
2520
11th to 20thDay
15%5%36%7%46%5%6%9%34%
2520
21st to endDay
13%7%36%7%35%6%6%8%36%
2744
August1st to 10thDay
14%8%36%7%36%5%6%8%32%
2506
11th to 20thDay
14%7%36%5%45%6%6%8%36%
2293
21st to endDay
16%7%25%6%35%46%8%37%
2376
September1st to 10thDay
16%6%25%6%3445%7%40%
2160
11th to 20thDay
15%7%36%5%3446%7%40%
2138
21st to endDay
20%7%35%43446%7%37%
1957
October1st to 10thDay
22%9%35%7%34447%33%
1800
11th to 20thDay
26%13%47%6%3435%6%23%
1800
21st to endDay
26%14%37%6%35%45%6%22%
1792
November1st to 10thDay
17%12%46%6%35%446%33%
1671
11th to 20thDay
21%14%6%9%7%45%5%5%421%
1536
21st to endDay
21%16%7%9%8%4444419%
1520
December1st to 10thDay
23%19%7%10%7%4444415%
1520
11th to 20thDay
20%15%8%12%7%34435%19%
1906
21st to endDay
23%20%7%11%6%3333418%
2772
January1st to 10thNight
15%18%7%10%7%35%5%45%21%
4429
11th to 20thNight
12%13%7%12%12%4445%6%21%
4440
21st to endNight
11%18%8%13%7%5%6%445%18%
4870
February1st to 10thNight
13%13%6%12%8%46%5%5%5%23%
2470
11th to 20thNight
12%13%6%12%8%45%45%5%26%
2380
21st to endNight
13%15%6%8%6%36%45%6%27%
1884
March1st to 10thNight
15%14%5%9%7%46%445%26%
2217
11th to 20thNight
16%13%5%8%6%445%5%5%30%
2020
21st to endNight
15%10%38%6%35%435%38%
2034
April1st to 10thNight
21%11%5%6%43445%7%31%
1800
11th to 20thNight
19%7%36%5%346%5%6%37%
1775
21st to endNight
20%9%37%5%3445%434%
1658
May1st to 10thNight
20%9%26%5%345%47%35%
1440
11th to 20thNight
18%7%36%6%345%5%6%39%
1415
21st to endNight
15%7%35%6%3445%8%40%
1550
June1st to 10thNight
17%7%36%6%35%5%5%9%33%
1440
11th to 20thNight
16%5%35%5%25%6%7%9%37%
1440
21st to endNight
17%6%26%5%45%5%6%7%36%
1440
July1st to 10thNight
12%6%25%5%3445%9%44%
1440
11th to 20thNight
13%5%26%5%446%6%9%42%
1440
21st to endNight
10%5%35%6%45%6%7%8%42%
1574
August1st to 10thNight
10%5%37%6%45%5%6%9%40%
1432
11th to 20thNight
11%6%26%5%3446%8%45%
1587
21st to endNight
15%5%25%5%345%6%7%43%
1980
September1st to 10thNight
14%6%36%5%33446%46%
1800
11th to 20thNight
15%5%25%43445%7%47%
1822
21st to endNight
17%6%35%434447%41%
2002
October1st to 10thNight
20%9%35%5%345%5%5%37%
2160
11th to 20thNight
23%12%36%6%35%45%5%29%
2160
21st to endNight
23%10%47%6%445%46%26%
2563
November1st to 10thNight
18%12%47%5%45%5%5%6%29%
2407
11th to 20thNight
18%13%5%9%7%35%45%5%25%
2641
21st to endNight
21%16%5%11%6%3445%5%18%
2660
December1st to 10thNight
20%18%7%11%7%45%445%16%
2660
11th to 20thNight
21%14%7%10%7%3433423%
3288
21st to endNight
24%21%6%9%7%3333418%
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
72%6%8%9%3
2518
11th to 20thDay
69%5%6%13%6%1
2520
21st to endDay
67%8%8%10%5%1
2781
February1st to 10thDay
66%5%7%15%6%1
1710
11th to 20thDay
61%6%10%12%9%1
1694
21st to endDay
64%5%7%14%9%1
1570
March1st to 10thDay
59%6%9%16%9%2
1850
11th to 20thDay
59%5%9%14%10%3
1935
21st to endDay
51%5%9%19%12%4
2322
April1st to 10thDay
57%49%17%10%3
2160
11th to 20thDay
54%48%20%12%2
2134
21st to endDay
57%5%8%14%12%4
2316
May1st to 10thDay
53%5%8%18%13%3
2520
11th to 20thDay
50%5%8%18%16%2
2482
21st to endDay
49%7%11%18%13%2
2725
June1st to 10thDay
56%5%11%17%10%1
2520
11th to 20thDay
45%8%13%22%10%2
2520
21st to endDay
52%9%13%17%9%
2520
July1st to 10thDay
41%8%15%25%10%
2450
11th to 20thDay
44%9%14%23%9%
2445
21st to endDay
45%9%15%23%8%
2591
August1st to 10thDay
49%10%15%21%5%
2492
11th to 20thDay
44%9%17%23%7%1
2293
21st to endDay
44%7%14%23%11%1
2376
September1st to 10thDay
42%7%14%24%13%
2160
11th to 20thDay
41%7%14%28%10%1
2138
21st to endDay
46%7%14%25%9%
1957
October1st to 10thDay
52%7%12%20%9%1
1800
11th to 20thDay
62%6%12%15%41
1800
21st to endDay
63%6%12%13%6%1
1792
November1st to 10thDay
52%6%14%20%6%1
1671
11th to 20thDay
65%7%10%10%8%
1536
21st to endDay
69%6%10%10%41
1520
December1st to 10thDay
73%6%9%9%3
1520
11th to 20thDay
68%6%9%12%5%
1906
21st to endDay
72%5%5%13%5%
2772
January1st to 10thNight
65%7%15%11%3
4429
11th to 20thNight
64%8%13%11%41
4440
21st to endNight
69%5%10%8%7%
4870
February1st to 10thNight
62%6%9%15%6%1
2470
11th to 20thNight
61%5%10%17%7%1
2382
21st to endNight
57%6%11%16%10%1
1884
March1st to 10thNight
60%6%8%15%8%2
2227
11th to 20thNight
56%5%11%16%10%2
2021
21st to endNight
50%5%8%20%14%4
2034
April1st to 10thNight
53%6%10%16%13%2
1800
11th to 20thNight
47%6%9%22%14%2
1775
21st to endNight
52%6%9%17%13%3
1658
May1st to 10thNight
49%6%8%19%15%3
1440
11th to 20thNight
46%7%9%19%17%4
1416
21st to endNight
44%7%11%22%14%2
1551
June1st to 10thNight
47%7%14%21%10%
1440
11th to 20thNight
41%10%13%22%12%2
1440
21st to endNight
47%8%14%20%12%
1440
July1st to 10thNight
37%7%17%25%14%1
1400
11th to 20thNight
38%8%15%27%11%1
1392
21st to endNight
37%10%19%24%10%
1486
August1st to 10thNight
40%10%18%25%8%
1422
11th to 20thNight
36%8%19%27%9%
1587
21st to endNight
39%7%17%27%9%
1980
September1st to 10thNight
39%6%15%27%13%1
1800
11th to 20thNight
37%6%15%32%9%1
1822
21st to endNight
42%5%15%29%9%
2002
October1st to 10thNight
48%7%10%23%11%
2160
11th to 20thNight
56%7%13%17%6%1
2160
21st to endNight
59%7%12%15%6%1
2563
November1st to 10thNight
54%7%15%17%6%
2407
11th to 20thNight
61%6%11%14%6%2
2641
21st to endNight
67%6%11%12%3
2660
December1st to 10thNight
71%6%10%10%4
2660
11th to 20thNight
65%5%8%14%6%1
3288
21st to endNight
72%5%6%13%5%
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
19%21%39%18%3
180
11th to 20thDay
28%18%33%16%5%1
180
21st to endDay
22%19%33%21%4
202
February1st to 10thDay
30%28%31%8%4
270
11th to 20thDay
26%29%36%9%
292
21st to endDay
32%23%30%13%2
382
March1st to 10thDay
27%23%30%15%5%
440
11th to 20thDay
25%24%31%15%31
420
21st to endDay
31%22%25%16%6%1
462
April1st to 10thDay
31%17%28%15%7%1
420
11th to 20thDay
33%18%23%14%10%2
412
21st to endDay
28%21%31%13%5%1
420
May1st to 10thDay
29%19%30%16%6%1
423
11th to 20thDay
22%20%29%20%7%2
447
21st to endDay
21%20%32%19%7%1
485
June1st to 10thDay
25%17%32%19%6%
450
11th to 20thDay
18%18%32%18%11%2
450
21st to endDay
22%16%28%23%9%2
450
July1st to 10thDay
13%10%36%30%9%2
445
11th to 20thDay
15%14%32%28%10%1
444
21st to endDay
13%11%35%27%11%2
488
August1st to 10thDay
16%11%28%33%11%2
446
11th to 20thDay
15%11%26%28%14%7%
439
21st to endDay
19%16%28%18%13%6%
495
September1st to 10thDay
18%11%30%22%12%7%
450
11th to 20thDay
16%13%30%19%16%7%
450
21st to endDay
21%15%26%19%12%7%
450
October1st to 10thDay
29%14%22%19%12%3
450
11th to 20thDay
32%21%27%12%6%2
450
21st to endDay
35%15%26%19%4
401
November1st to 10thDay
30%16%29%20%41
365
11th to 20thDay
28%21%36%8%6%2
196
21st to endDay
33%21%28%15%21
180
December1st to 10thDay
33%18%30%14%4
180
11th to 20thDay
31%23%33%9%21
180
21st to endDay
31%21%31%13%31
198
January1st to 10thNight
28%15%36%17%4
760
11th to 20thNight
29%17%28%21%6%
760
21st to endNight
19%15%35%24%7%1
836
February1st to 10thNight
19%19%34%22%5%
760
11th to 20thNight
21%21%36%18%4
743
21st to endNight
23%20%30%24%4
628
March1st to 10thNight
24%17%32%22%5%
743
11th to 20thNight
24%19%31%20%5%1
720
21st to endNight
24%14%31%23%7%1
792
April1st to 10thNight
29%15%27%23%7%
720
11th to 20thNight
23%17%29%23%7%
711
21st to endNight
26%17%25%23%9%1
578
May1st to 10thNight
23%13%27%26%10%1
360
11th to 20thNight
22%10%29%31%8%
354
21st to endNight
17%11%35%28%9%
389
June1st to 10thNight
19%8%34%31%8%1
360
11th to 20thNight
17%8%29%32%13%1
360
21st to endNight
19%7%24%33%17%
360
July1st to 10thNight
11%329%42%15%
350
11th to 20thNight
14%424%38%20%
348
21st to endNight
12%5%26%38%17%2
394
August1st to 10thNight
11%6%22%39%22%1
358
11th to 20thNight
12%421%35%24%3
523
21st to endNight
17%7%26%32%16%2
792
September1st to 10thNight
19%5%28%29%18%1
720
11th to 20thNight
19%8%23%30%19%2
720
21st to endNight
21%10%24%27%17%2
720
October1st to 10thNight
23%13%28%23%13%1
720
11th to 20thNight
30%14%27%22%7%1
720
21st to endNight
28%15%28%24%4
792
November1st to 10thNight
27%14%29%22%8%1
740
11th to 20thNight
26%19%30%15%10%1
760
21st to endNight
32%19%24%20%5%1
760
December1st to 10thNight
30%18%28%18%5%
760
11th to 20thNight
28%18%30%18%41
760
21st to endNight
33%17%27%17%4
836
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