Dolbeau-Mistassini
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dolbeau-Mistassini 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
31%
22612
11%
74918
7%
22564
36%
22564
14%
55666

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
22%
778
8%
2688
5%
775
27%
775
8%
2195
January11th to 20thNight
22%
744
10%
2602
6%
744
28%
744
10%
2034
January21st to endNight
35%
792
14%
2772
11%
792
41%
792
12%
2074
February1st to 10thNight
32%
720
13%
2520
10%
720
40%
720
14%
1838
February11th to 20thNight
24%
703
10%
2204
8%
700
29%
700
11%
1727
February21st to endNight
30%
592
16%
1776
10%
592
38%
592
16%
1324
March1st to 10thNight
30%
720
13%
2160
11%
720
36%
720
15%
1619
March11th to 20thNight
27%
720
13%
2110
8%
720
32%
720
13%
1617
March21st to endNight
29%
792
18%
1990
7%
792
35%
792
20%
1497
April1st to 10thNight
27%
720
12%
1800
5%
720
30%
720
16%
1442
April11th to 20thNight
32%
628
17%
1692
8%
628
38%
628
22%
1222
April21st to endNight
27%
540
17%
1620
7%
540
37%
540
20%
1126
May1st to 10thNight
27%
378
13%
1458
10%
378
38%
378
15%
1005
May11th to 20thNight
30%
354
16%
1416
14%
354
43%
354
16%
923
May21st to endNight
30%
389
11%
1432
7%
388
40%
388
18%
962
June1st to 10thNight
35%
360
6%
1260
3%
360
39%
360
15%
886
June11th to 20thNight
38%
360
7%
1260
4%
360
41%
360
20%
812
June21st to endNight
42%
360
6%
1260
3%
360
43%
360
18%
855
July1st to 10thNight
38%
350
6%
1246
4%
350
41%
350
17%
845
July11th to 20thNight
49%
348
8%
1392
11%
348
51%
348
19%
869
July21st to endNight
47%
394
8%
1486
12%
372
50%
372
14%
1017
August1st to 10thNight
51%
358
10%
1422
11%
356
56%
356
17%
952
August11th to 20thNight
46%
432
13%
1496
10%
432
50%
432
19%
995
August21st to endNight
46%
702
16%
1890
9%
702
49%
702
25%
1272
September1st to 10thNight
44%
720
14%
1800
7%
720
47%
720
28%
1249
September11th to 20thNight
39%
720
12%
1916
7%
720
41%
720
23%
1357
September21st to endNight
36%
720
16%
1980
10%
720
40%
720
22%
1402
October1st to 10thNight
37%
720
19%
2052
11%
720
45%
720
23%
1406
October11th to 20thNight
27%
720
10%
2299
7%
720
31%
720
12%
1789
October21st to endNight
24%
792
9%
2574
6%
792
29%
792
11%
2051
November1st to 10thNight
22%
740
11%
2407
6%
740
29%
740
11%
1866
November11th to 20thNight
24%
775
10%
2632
7%
775
28%
775
10%
2068
November21st to endNight
19%
850
7%
2850
4%
850
23%
850
8%
2345
December1st to 10thNight
23%
850
7%
2850
5%
850
26%
850
9%
2351
December11th to 20thNight
25%
850
11%
3457
6%
848
30%
848
9%
2665
December21st to endNight
22%
921
7%
5149
5%
906
27%
906
5%
4009

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%10%48%7%45%5%6%7%27%
74561
Night
18%12%5%8%7%45%5%5%6%26%
75246
TransparencyDay
57%311%20%8%1
74262
Night
60%310%19%8%1
75080
SeeingDay
24%7%26%26%13%4
14092
Night
24%6%26%31%11%1
22626

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
16%17%8%12%7%36%5%4417%
1474
11th to 20thDay
15%15%6%11%8%45%5%6%6%20%
1480
21st to endDay
10%12%6%12%9%46%5%5%7%26%
1584
February1st to 10thDay
8%11%6%9%11%5%9%7%6%5%23%
1440
11th to 20thDay
12%13%6%11%9%5%7%5%5%6%22%
1640
21st to endDay
11%13%5%11%7%46%6%7%6%25%
1480
March1st to 10thDay
13%13%6%10%7%445%6%6%26%
1797
11th to 20thDay
16%14%47%7%46%5%5%6%26%
1849
21st to endDay
16%11%5%8%6%45%45%7%30%
2362
April1st to 10thDay
18%13%5%10%8%44445%25%
2160
11th to 20thDay
18%8%37%6%45%5%6%6%34%
2217
21st to endDay
21%9%5%7%44445%6%32%
2340
May1st to 10thDay
21%8%46%5%35%45%6%34%
2518
11th to 20thDay
18%7%36%5%345%6%6%36%
2478
21st to endDay
18%7%46%6%45%5%6%7%33%
2844
June1st to 10thDay
20%8%37%6%46%5%6%7%30%
2700
11th to 20thDay
17%6%36%6%45%5%7%8%34%
2700
21st to endDay
22%7%26%7%45%5%6%8%29%
2700
July1st to 10thDay
17%8%36%6%46%7%7%9%28%
2674
11th to 20thDay
15%5%46%6%47%6%7%9%31%
2520
21st to endDay
14%8%36%7%5%6%6%7%9%29%
2744
August1st to 10thDay
18%7%38%8%46%7%6%9%25%
2506
11th to 20thDay
17%7%47%7%45%5%6%9%29%
2386
21st to endDay
16%8%37%7%46%6%6%7%31%
2463
September1st to 10thDay
18%7%28%6%45%5%5%7%32%
2160
11th to 20thDay
18%7%36%6%45%46%8%33%
2044
21st to endDay
23%7%37%6%45%5%5%6%31%
1980
October1st to 10thDay
19%9%37%6%45%5%5%6%31%
1905
11th to 20thDay
28%11%48%7%45%5%46%18%
1660
21st to endDay
27%13%45%6%44446%22%
1782
November1st to 10thDay
21%14%5%9%7%45%5%45%22%
1671
11th to 20thDay
22%12%7%9%8%46%446%19%
1544
21st to endDay
22%16%6%10%7%445%46%16%
1330
December1st to 10thDay
19%15%5%10%8%5%6%5%5%5%16%
1330
11th to 20thDay
21%14%6%8%6%35%446%23%
1668
21st to endDay
16%16%7%10%9%5%5%5%5%5%17%
2431
January1st to 10thNight
15%19%8%12%9%45%5%45%15%
2688
11th to 20thNight
15%15%6%13%7%36%5%5%6%20%
2602
21st to endNight
9%13%7%11%9%5%7%6%6%7%22%
2772
February1st to 10thNight
10%11%6%11%10%5%6%5%5%7%25%
2520
11th to 20thNight
11%16%6%12%9%5%6%46%5%20%
2202
21st to endNight
12%15%5%8%8%45%45%7%26%
1776
March1st to 10thNight
12%13%7%9%7%45%6%5%7%25%
2150
11th to 20thNight
16%14%5%9%7%46%5%5%5%24%
2109
21st to endNight
14%15%5%7%6%45%5%47%30%
1990
April1st to 10thNight
22%14%5%8%6%35%5%45%24%
1800
11th to 20thNight
19%9%45%5%45%5%5%6%33%
1692
21st to endNight
18%9%37%7%3345%6%34%
1620
May1st to 10thNight
21%10%36%5%25%445%34%
1458
11th to 20thNight
19%10%47%44345%6%35%
1415
21st to endNight
23%6%36%5%24446%35%
1431
June1st to 10thNight
19%7%38%6%45%6%6%7%27%
1260
11th to 20thNight
17%7%36%5%4445%7%38%
1260
21st to endNight
17%6%37%6%47%6%8%8%29%
1260
July1st to 10thNight
18%6%37%7%36%6%6%7%30%
1282
11th to 20thNight
13%6%38%6%45%5%6%8%35%
1440
21st to endNight
16%7%37%7%46%5%5%6%32%
1574
August1st to 10thNight
15%6%37%6%46%6%7%9%31%
1432
11th to 20thNight
15%8%47%6%345%5%8%34%
1496
21st to endNight
16%6%26%5%36%7%7%8%35%
1890
September1st to 10thNight
17%7%36%6%35%5%6%7%37%
1800
11th to 20thNight
21%6%37%5%45%446%34%
1916
21st to endNight
20%6%37%5%46%445%36%
1980
October1st to 10thNight
19%7%35%5%35%5%5%8%36%
2052
11th to 20thNight
29%12%46%5%45%45%6%21%
2299
21st to endNight
29%11%37%6%45%5%5%5%19%
2574
November1st to 10thNight
23%14%5%8%6%35%5%46%22%
2407
11th to 20thNight
21%15%5%10%6%45%45%6%20%
2632
21st to endNight
22%16%5%10%8%35%5%45%16%
2850
December1st to 10thNight
19%18%6%11%9%4434417%
2850
11th to 20thNight
22%14%5%9%6%345%5%6%21%
3531
21st to endNight
15%20%9%11%7%3433420%
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
72%39%12%4
1475
11th to 20thDay
65%38%18%6%
1480
21st to endDay
59%35%21%11%1
1584
February1st to 10thDay
60%38%19%9%1
1440
11th to 20thDay
63%38%16%9%
1649
21st to endDay
58%48%21%9%1
1480
March1st to 10thDay
58%38%17%12%1
1800
11th to 20thDay
60%39%17%11%1
1849
21st to endDay
54%310%19%12%1
2362
April1st to 10thDay
63%210%14%9%2
2160
11th to 20thDay
50%29%25%12%1
2217
21st to endDay
55%28%21%13%1
2340
May1st to 10thDay
51%310%20%15%2
2518
11th to 20thDay
48%210%23%14%2
2482
21st to endDay
51%38%21%15%2
2844
June1st to 10thDay
53%38%21%13%1
2700
11th to 20thDay
47%411%23%13%2
2700
21st to endDay
55%311%20%10%1
2700
July1st to 10thDay
52%415%22%6%
2600
11th to 20thDay
48%417%25%6%
2445
21st to endDay
52%417%23%5%
2591
August1st to 10thDay
55%419%19%2
2492
11th to 20thDay
51%418%20%6%
2386
21st to endDay
52%415%23%6%
2463
September1st to 10thDay
51%315%22%8%
2160
11th to 20thDay
50%418%22%6%
2044
21st to endDay
55%413%22%7%
1980
October1st to 10thDay
54%215%21%6%2
1905
11th to 20thDay
69%312%13%3
1660
21st to endDay
65%312%15%5%1
1782
November1st to 10thDay
65%211%16%5%1
1671
11th to 20thDay
68%311%15%3
1544
21st to endDay
71%311%13%3
1330
December1st to 10thDay
71%38%15%3
1330
11th to 20thDay
65%36%21%6%
1668
21st to endDay
71%18%11%8%
2431
January1st to 10thNight
73%28%13%4
2688
11th to 20thNight
67%38%15%7%
2602
21st to endNight
61%37%20%8%
2772
February1st to 10thNight
59%38%20%10%
2520
11th to 20thNight
66%38%16%8%
2204
21st to endNight
59%38%21%9%
1776
March1st to 10thNight
60%38%20%8%1
2160
11th to 20thNight
63%27%16%11%1
2110
21st to endNight
56%37%22%12%1
1990
April1st to 10thNight
64%37%16%7%3
1800
11th to 20thNight
52%27%25%13%
1692
21st to endNight
51%38%22%14%2
1620
May1st to 10thNight
55%38%15%16%3
1458
11th to 20thNight
52%28%21%15%3
1416
21st to endNight
51%37%22%16%1
1432
June1st to 10thNight
55%49%22%10%1
1260
11th to 20thNight
47%48%22%14%4
1260
21st to endNight
51%413%21%11%
1260
July1st to 10thNight
52%414%23%7%
1246
11th to 20thNight
46%414%26%8%1
1392
21st to endNight
54%412%23%7%
1486
August1st to 10thNight
50%6%21%21%2
1422
11th to 20thNight
49%419%21%7%
1496
21st to endNight
46%417%29%4
1890
September1st to 10thNight
46%415%26%9%1
1800
11th to 20thNight
52%217%22%6%
1916
21st to endNight
52%313%25%7%
1980
October1st to 10thNight
48%414%24%10%1
2052
11th to 20thNight
65%311%17%5%
2299
21st to endNight
67%310%14%6%1
2574
November1st to 10thNight
65%312%15%5%
2407
11th to 20thNight
67%312%14%4
2632
21st to endNight
72%29%13%3
2850
December1st to 10thNight
72%29%14%2
2850
11th to 20thNight
66%28%18%6%
3532
21st to endNight
71%19%11%7%1
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
22%7%29%32%9%1
180
11th to 20thDay
19%7%28%28%17%2
170
21st to endDay
17%6%23%30%17%7%
176
February1st to 10thDay
15%11%36%26%9%3
160
11th to 20thDay
21%12%31%25%10%
319
21st to endDay
20%10%34%24%11%1
346
March1st to 10thDay
22%9%26%26%14%1
420
11th to 20thDay
25%8%30%24%11%3
420
21st to endDay
26%9%27%26%10%3
462
April1st to 10thDay
25%11%24%29%10%2
420
11th to 20thDay
21%9%26%29%13%2
412
21st to endDay
25%8%32%20%13%2
420
May1st to 10thDay
29%11%24%24%10%3
423
11th to 20thDay
20%10%28%25%13%4
447
21st to endDay
23%10%29%27%9%1
604
June1st to 10thDay
26%6%27%26%13%3
630
11th to 20thDay
21%5%26%31%14%3
630
21st to endDay
24%422%29%17%4
630
July1st to 10thDay
19%6%24%33%15%3
595
11th to 20thDay
21%5%23%29%17%7%
444
21st to endDay
19%222%26%23%6%
488
August1st to 10thDay
19%422%29%17%9%
446
11th to 20thDay
19%416%31%20%9%
439
21st to endDay
23%6%24%21%15%9%
495
September1st to 10thDay
22%6%26%22%17%8%
450
11th to 20thDay
21%8%25%27%14%4
450
21st to endDay
24%7%23%23%17%6%
450
October1st to 10thDay
24%8%27%22%14%5%
450
11th to 20thDay
34%7%24%20%11%3
380
21st to endDay
36%7%26%21%10%1
396
November1st to 10thDay
32%13%28%21%5%1
365
11th to 20thDay
30%11%28%20%9%1
237
21st to endDay
30%8%32%20%6%4
180
December1st to 10thDay
22%9%21%27%16%5%
180
11th to 20thDay
23%8%36%23%6%4
180
21st to endDay
29%9%25%22%12%3
198
January1st to 10thNight
23%6%29%33%8%
778
11th to 20thNight
24%8%28%29%11%1
744
21st to endNight
15%5%25%39%14%1
792
February1st to 10thNight
14%6%30%36%12%2
720
11th to 20thNight
21%6%31%31%10%1
703
21st to endNight
18%9%29%32%11%2
592
March1st to 10thNight
21%7%29%33%9%
720
11th to 20thNight
23%10%29%26%11%
720
21st to endNight
22%8%29%31%9%1
792
April1st to 10thNight
31%7%23%30%8%1
720
11th to 20thNight
24%7%29%31%8%
628
21st to endNight
22%10%34%25%9%
540
May1st to 10thNight
25%8%30%28%8%1
378
11th to 20thNight
25%7%30%29%8%1
354
21st to endNight
26%6%31%29%7%1
389
June1st to 10thNight
23%428%36%8%1
360
11th to 20thNight
21%326%36%14%1
360
21st to endNight
21%5%21%36%15%1
360
July1st to 10thNight
22%226%36%13%1
350
11th to 20thNight
17%122%41%20%
348
21st to endNight
22%217%40%18%1
394
August1st to 10thNight
18%315%44%17%1
358
11th to 20thNight
21%218%35%23%1
432
21st to endNight
21%421%33%19%3
702
September1st to 10thNight
21%421%38%16%1
720
11th to 20thNight
26%5%22%31%14%2
720
21st to endNight
24%426%31%12%3
720
October1st to 10thNight
24%5%26%32%12%1
720
11th to 20thNight
35%5%24%27%9%1
720
21st to endNight
36%5%26%24%8%1
792
November1st to 10thNight
32%10%25%25%7%2
740
11th to 20thNight
30%8%28%25%9%1
775
21st to endNight
31%8%29%24%7%1
850
December1st to 10thNight
28%7%25%29%10%1
850
11th to 20thNight
25%9%26%28%11%1
850
21st to endNight
28%8%25%27%10%2
935
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