Gatineau
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gatineau 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
30%
22565
14%
74782
8%
22524
38%
22524
16%
53367

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
15%
760
8%
2649
2%
757
23%
757
8%
2143
January11th to 20thNight
18%
744
9%
2602
5%
744
23%
744
8%
2056
January21st to endNight
25%
792
13%
2709
8%
792
33%
792
14%
1957
February1st to 10thNight
19%
720
10%
2340
3%
720
27%
720
10%
1816
February11th to 20thNight
19%
703
13%
2267
6%
700
29%
700
13%
1669
February21st to endNight
26%
592
15%
1776
8%
592
35%
592
14%
1314
March1st to 10thNight
21%
720
14%
2160
8%
720
29%
720
14%
1621
March11th to 20thNight
22%
720
16%
1985
6%
720
32%
720
17%
1455
March21st to endNight
27%
792
21%
2057
8%
792
36%
792
21%
1451
April1st to 10thNight
23%
720
15%
1800
4%
720
29%
720
20%
1337
April11th to 20thNight
27%
711
17%
1775
5%
711
33%
711
21%
1289
April21st to endNight
30%
605
16%
1685
7%
605
36%
605
19%
1218
May1st to 10thNight
35%
360
17%
1440
13%
360
44%
360
16%
924
May11th to 20thNight
35%
354
21%
1416
17%
354
49%
354
19%
889
May21st to endNight
35%
389
13%
1551
10%
388
47%
388
22%
922
June1st to 10thNight
41%
360
10%
1440
11%
360
49%
360
18%
949
June11th to 20thNight
44%
360
12%
1440
15%
360
52%
360
20%
876
June21st to endNight
40%
360
10%
1440
13%
360
46%
360
17%
937
July1st to 10thNight
52%
350
14%
1400
19%
350
60%
350
24%
812
July11th to 20thNight
54%
348
16%
1392
23%
348
58%
348
25%
803
July21st to endNight
53%
394
15%
1486
17%
372
58%
372
23%
872
August1st to 10thNight
52%
379
16%
1443
15%
377
57%
377
23%
869
August11th to 20thNight
57%
542
17%
1606
13%
542
60%
542
29%
1021
August21st to endNight
50%
792
17%
1980
8%
792
53%
792
31%
1316
September1st to 10thNight
48%
720
17%
1800
7%
720
52%
720
32%
1198
September11th to 20thNight
51%
720
22%
1802
12%
720
55%
720
33%
1179
September21st to endNight
42%
720
21%
2031
15%
720
48%
720
26%
1338
October1st to 10thNight
35%
720
17%
2160
11%
720
43%
720
20%
1494
October11th to 20thNight
27%
720
14%
2160
8%
720
36%
720
17%
1581
October21st to endNight
27%
792
13%
2527
7%
792
35%
792
14%
1879
November1st to 10thNight
31%
740
15%
2407
9%
740
39%
740
17%
1677
November11th to 20thNight
21%
760
15%
2649
9%
760
30%
760
13%
1911
November21st to endNight
20%
760
10%
2660
5%
760
27%
760
10%
2036
December1st to 10thNight
19%
760
8%
2660
4%
760
24%
760
8%
2165
December11th to 20thNight
18%
759
12%
3243
6%
759
26%
759
9%
2447
December21st to endNight
16%
827
6%
4844
2%
817
22%
817
4%
3946

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%9%37%6%35%5%5%7%33%
74758
Night
18%10%47%6%35%45%6%33%
75038
TransparencyDay
50%7%12%20%10%1
74463
Night
52%6%11%19%10%1
74867
SeeingDay
22%14%29%22%10%3
13363
Night
22%11%29%27%10%1
22575

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
18%17%6%10%7%345%4422%
1517
11th to 20thDay
19%14%6%9%7%45%445%24%
1480
21st to endDay
14%14%5%9%7%5%5%5%6%6%25%
1642
February1st to 10thDay
13%14%5%12%8%5%445%6%24%
1620
11th to 20thDay
14%14%6%9%6%45%45%5%29%
1580
21st to endDay
19%12%49%8%45%5%5%5%24%
1480
March1st to 10thDay
15%10%5%8%8%45%5%5%6%29%
1797
11th to 20thDay
15%11%47%6%5%5%5%5%5%31%
1970
21st to endDay
19%7%46%6%3445%5%36%
2299
April1st to 10thDay
22%9%46%6%35%346%32%
2160
11th to 20thDay
21%8%36%6%3445%5%37%
2134
21st to endDay
23%9%37%6%35%445%31%
2289
May1st to 10thDay
20%7%36%5%35%45%6%34%
2520
11th to 20thDay
16%7%36%5%35%45%6%39%
2478
21st to endDay
16%6%35%6%46%5%6%7%37%
2725
June1st to 10thDay
21%7%36%7%35%6%6%6%30%
2520
11th to 20thDay
14%6%25%6%36%5%6%8%38%
2520
21st to endDay
20%5%36%5%46%7%6%7%31%
2520
July1st to 10thDay
12%5%35%436%6%6%9%40%
2520
11th to 20thDay
12%5%35%5%45%6%6%10%38%
2520
21st to endDay
12%5%35%6%45%5%7%10%39%
2744
August1st to 10thDay
11%5%36%6%45%6%6%8%40%
2481
11th to 20thDay
12%5%26%6%35%6%7%8%40%
2276
21st to endDay
13%6%245%45%5%6%9%41%
2376
September1st to 10thDay
14%435%5%35%5%6%8%42%
2160
11th to 20thDay
13%5%245%345%6%7%46%
2157
21st to endDay
19%5%35%4345%5%9%39%
1926
October1st to 10thDay
21%8%36%5%335%6%6%35%
1800
11th to 20thDay
24%8%36%6%36%6%5%6%28%
1800
21st to endDay
26%9%36%6%45%445%27%
1828
November1st to 10thDay
15%9%36%6%45%6%6%7%34%
1671
11th to 20thDay
20%11%48%5%35%6%6%6%26%
1530
21st to endDay
22%14%38%7%45%5%5%6%21%
1520
December1st to 10thDay
23%15%7%9%7%35%5%5%6%17%
1520
11th to 20thDay
21%13%48%7%45%44425%
1906
21st to endDay
29%18%5%8%6%2433419%
2772
January1st to 10thNight
18%16%6%12%7%5%5%345%20%
2649
11th to 20thNight
18%16%5%10%7%45%43423%
2602
21st to endNight
12%14%6%9%7%44446%30%
2709
February1st to 10thNight
14%13%6%11%7%46%5%5%5%23%
2340
11th to 20thNight
14%12%5%10%7%45%446%29%
2265
21st to endNight
17%11%5%8%6%35%45%6%30%
1776
March1st to 10thNight
16%12%5%8%6%45%45%5%29%
2150
11th to 20thNight
16%11%5%8%6%3444433%
1984
21st to endNight
18%7%46%6%3435%5%40%
2057
April1st to 10thNight
21%9%46%5%25%35%6%34%
1800
11th to 20thNight
20%6%46%6%345%5%5%36%
1775
21st to endNight
22%8%36%6%35%45%6%33%
1685
May1st to 10thNight
21%6%36%5%35%46%7%37%
1440
11th to 20thNight
19%7%35%5%3445%7%40%
1415
21st to endNight
13%5%35%5%346%5%7%44%
1550
June1st to 10thNight
17%6%35%6%45%6%7%8%34%
1440
11th to 20thNight
14%6%25%5%345%6%7%42%
1440
21st to endNight
17%7%35%5%35%5%7%8%36%
1440
July1st to 10thNight
11%425%5%36%5%6%7%46%
1440
11th to 20thNight
12%7%34425%5%6%7%44%
1440
21st to endNight
10%425%6%45%6%6%9%42%
1574
August1st to 10thNight
10%5%35%5%446%5%9%43%
1453
11th to 20thNight
11%5%25%5%35%46%7%46%
1606
21st to endNight
12%435%5%45%5%6%7%44%
1980
September1st to 10thNight
13%425%5%35%5%5%6%46%
1800
11th to 20thNight
15%43442345%6%49%
1802
21st to endNight
18%5%16%5%34446%44%
2031
October1st to 10thNight
19%7%25%5%35%45%6%38%
2160
11th to 20thNight
22%7%36%8%45%45%7%31%
2160
21st to endNight
24%9%37%6%45%447%28%
2527
November1st to 10thNight
20%8%35%5%4445%6%35%
2407
11th to 20thNight
19%10%48%5%45%5%5%6%29%
2649
21st to endNight
22%11%48%6%445%46%25%
2660
December1st to 10thNight
21%17%5%8%7%45%5%46%18%
2660
11th to 20thNight
23%14%47%7%3434427%
3288
21st to endNight
30%17%48%5%3434419%
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
66%6%9%14%5%
1518
11th to 20thDay
64%5%9%11%10%1
1480
21st to endDay
59%7%12%13%8%1
1642
February1st to 10thDay
62%411%17%5%2
1620
11th to 20thDay
57%5%12%15%9%1
1589
21st to endDay
60%6%10%13%9%1
1480
March1st to 10thDay
56%6%10%17%10%1
1800
11th to 20thDay
54%5%12%14%12%3
1970
21st to endDay
49%6%8%18%13%5%
2299
April1st to 10thDay
54%48%19%12%3
2160
11th to 20thDay
49%48%22%15%2
2134
21st to endDay
56%5%8%14%13%4
2289
May1st to 10thDay
50%6%8%19%14%4
2520
11th to 20thDay
46%5%9%21%16%3
2482
21st to endDay
45%8%12%20%13%2
2725
June1st to 10thDay
53%7%11%18%11%1
2520
11th to 20thDay
42%9%11%24%12%3
2520
21st to endDay
48%9%13%20%10%1
2520
July1st to 10thDay
38%9%13%25%14%1
2450
11th to 20thDay
40%7%15%27%11%
2445
21st to endDay
39%10%15%25%11%
2591
August1st to 10thDay
40%9%16%25%10%
2467
11th to 20thDay
40%9%16%26%9%1
2276
21st to endDay
39%7%15%28%12%1
2376
September1st to 10thDay
39%8%15%27%12%
2160
11th to 20thDay
36%7%14%30%12%1
2157
21st to endDay
43%7%15%26%8%
1926
October1st to 10thDay
48%6%12%22%10%1
1800
11th to 20thDay
56%8%15%15%6%1
1800
21st to endDay
59%5%13%15%8%1
1828
November1st to 10thDay
48%7%15%22%6%1
1671
11th to 20thDay
56%7%13%15%8%1
1530
21st to endDay
64%7%12%10%6%1
1520
December1st to 10thDay
67%7%13%10%3
1520
11th to 20thDay
63%6%13%13%5%
1906
21st to endDay
71%5%7%14%3
2772
January1st to 10thNight
69%5%10%12%5%
2649
11th to 20thNight
66%5%10%11%8%1
2602
21st to endNight
56%5%10%17%11%1
2709
February1st to 10thNight
62%6%10%15%6%1
2340
11th to 20thNight
58%5%10%19%7%1
2267
21st to endNight
55%6%9%18%11%1
1776
March1st to 10thNight
57%6%10%17%9%2
2160
11th to 20thNight
55%410%18%12%2
1985
21st to endNight
49%47%20%15%5%
2057
April1st to 10thNight
52%5%10%17%14%2
1800
11th to 20thNight
49%6%8%20%16%1
1775
21st to endNight
52%5%8%16%15%4
1685
May1st to 10thNight
47%6%8%20%15%5%
1440
11th to 20thNight
45%5%8%21%19%3
1416
21st to endNight
38%7%15%19%17%3
1551
June1st to 10thNight
46%8%13%24%9%1
1440
11th to 20thNight
40%8%11%23%17%2
1440
21st to endNight
45%9%12%20%13%1
1440
July1st to 10thNight
34%9%11%27%16%2
1400
11th to 20thNight
37%6%13%32%12%
1392
21st to endNight
37%8%16%25%14%
1486
August1st to 10thNight
37%9%19%22%13%1
1443
11th to 20thNight
36%8%16%28%11%
1606
21st to endNight
37%8%17%27%11%
1980
September1st to 10thNight
37%7%11%29%14%1
1800
11th to 20thNight
34%9%13%33%10%1
1802
21st to endNight
42%5%12%31%10%
2031
October1st to 10thNight
47%7%11%23%13%
2160
11th to 20thNight
53%7%11%21%8%
2160
21st to endNight
56%6%13%16%8%
2527
November1st to 10thNight
50%6%15%20%8%
2407
11th to 20thNight
56%5%12%17%9%1
2649
21st to endNight
60%7%13%15%5%
2660
December1st to 10thNight
68%6%10%12%4
2660
11th to 20thNight
61%5%9%16%7%1
3288
21st to endNight
71%5%7%13%4
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
24%17%29%25%31
180
11th to 20thDay
28%15%35%15%5%1
170
21st to endDay
23%13%38%19%7%
202
February1st to 10thDay
34%21%34%10%1
240
11th to 20thDay
28%24%33%14%1
247
21st to endDay
30%20%30%18%3
346
March1st to 10thDay
25%15%35%18%6%
420
11th to 20thDay
26%18%30%21%41
420
21st to endDay
29%19%26%16%9%1
462
April1st to 10thDay
27%20%30%16%6%
420
11th to 20thDay
31%17%23%17%11%1
412
21st to endDay
29%18%30%14%6%2
420
May1st to 10thDay
24%13%32%20%7%3
423
11th to 20thDay
19%18%29%20%11%3
447
21st to endDay
18%15%31%23%11%2
485
June1st to 10thDay
25%11%29%24%9%2
450
11th to 20thDay
17%14%27%27%12%3
450
21st to endDay
21%12%26%25%13%3
450
July1st to 10thDay
12%7%25%36%14%5%
445
11th to 20thDay
13%7%32%29%16%4
444
21st to endDay
12%7%30%31%15%5%
488
August1st to 10thDay
13%7%26%32%17%4
446
11th to 20thDay
13%7%23%29%19%8%
439
21st to endDay
13%11%28%24%16%8%
495
September1st to 10thDay
16%8%28%22%15%10%
450
11th to 20thDay
13%10%24%24%19%11%
450
21st to endDay
18%13%27%23%14%6%
450
October1st to 10thDay
24%12%25%22%12%5%
450
11th to 20thDay
25%17%30%18%8%1
450
21st to endDay
32%13%26%22%6%
419
November1st to 10thDay
24%18%27%20%9%1
365
11th to 20thDay
27%17%35%14%5%2
190
21st to endDay
28%19%29%17%42
180
December1st to 10thDay
28%14%35%20%3
180
11th to 20thDay
26%23%32%17%11
180
21st to endDay
32%21%32%13%21
198
January1st to 10thNight
27%13%34%22%4
760
11th to 20thNight
27%15%30%22%6%1
744
21st to endNight
19%9%37%28%6%1
792
February1st to 10thNight
24%13%34%25%4
720
11th to 20thNight
20%16%37%23%4
703
21st to endNight
25%14%29%28%3
592
March1st to 10thNight
23%15%34%24%4
720
11th to 20thNight
23%18%32%23%5%
720
21st to endNight
24%13%29%25%8%
792
April1st to 10thNight
26%14%30%25%5%
720
11th to 20thNight
23%15%31%23%8%
711
21st to endNight
26%12%27%26%8%1
605
May1st to 10thNight
23%8%27%30%9%2
360
11th to 20thNight
21%11%26%32%10%1
354
21st to endNight
14%7%38%29%11%1
389
June1st to 10thNight
20%330%38%9%
360
11th to 20thNight
16%6%27%34%14%2
360
21st to endNight
19%6%27%32%15%1
360
July1st to 10thNight
9%428%41%17%
350
11th to 20thNight
12%422%43%18%1
348
21st to endNight
8%328%42%17%2
394
August1st to 10thNight
12%421%38%24%1
379
11th to 20thNight
13%317%38%25%3
542
21st to endNight
13%8%22%36%20%2
792
September1st to 10thNight
14%6%27%33%19%1
720
11th to 20thNight
17%5%21%32%21%3
720
21st to endNight
20%8%25%25%20%2
720
October1st to 10thNight
23%9%27%24%16%2
720
11th to 20thNight
25%11%29%25%9%1
720
21st to endNight
28%13%26%28%6%
792
November1st to 10thNight
25%13%25%27%9%1
740
11th to 20thNight
24%15%35%16%9%1
760
21st to endNight
29%16%27%22%7%
760
December1st to 10thNight
30%15%29%23%3
760
11th to 20thNight
27%16%30%21%5%1
760
21st to endNight
33%13%31%19%4
836
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