Gatineau
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gatineau clear sky chart from 2005-11-05 to 2017-12-01.

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
32%
14944
13%
47797
9%
14912
38%
14912
17%
34076

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 15thNight
17%
720
7%
2506
3%
716
23%
716
8%
2026
January16th to endNight
23%
768
10%
2646
6%
768
29%
768
12%
1983
February1st to 15thNight
21%
704
10%
2287
5%
701
28%
701
11%
1760
February16th to endNight
24%
631
13%
1947
7%
631
34%
631
13%
1468
March1st to 15thNight
21%
720
14%
2103
7%
720
29%
720
15%
1578
March16th to endNight
31%
768
21%
2031
10%
768
39%
768
22%
1406
April1st to 15thNight
25%
718
15%
1796
5%
718
31%
718
21%
1328
April16th to endNight
31%
642
17%
1722
7%
642
38%
642
22%
1210
May1st to 15thNight
35%
360
17%
1440
14%
360
44%
360
16%
951
May16th to endNight
36%
375
13%
1497
11%
374
46%
374
19%
950
June1st to 15thNight
40%
360
9%
1440
9%
360
48%
360
16%
977
June16th to endNight
43%
360
8%
1440
11%
360
47%
360
18%
921
July1st to 15thNight
56%
340
14%
1360
21%
340
60%
340
26%
765
July16th to endNight
57%
376
14%
1418
18%
354
61%
354
26%
805
August1st to 15thNight
52%
434
14%
1505
12%
432
56%
432
23%
943
August16th to endNight
56%
711
20%
1857
10%
711
60%
711
35%
1158
September1st to 15thNight
49%
720
15%
1800
7%
720
51%
720
28%
1250
September16th to endNight
48%
717
23%
1956
15%
717
53%
717
31%
1246
October1st to 15thNight
35%
720
17%
2160
11%
720
43%
720
21%
1482
October16th to endNight
27%
768
12%
2406
7%
768
34%
768
14%
1805
November1st to 15thNight
29%
760
16%
2530
11%
760
38%
760
16%
1784
November16th to endNight
21%
780
10%
2730
7%
780
27%
780
10%
2092
December1st to 15thNight
19%
724
7%
2532
3%
724
24%
724
9%
2027
December16th to endNight
16%
768
10%
2688
4%
768
23%
768
8%
2161

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%7%36%5%3445%6%32%
48636
Night
18%9%36%5%34445%33%
47966
Cloud CoverDay
19%7%36%5%3445%6%33%
48645
Night
18%9%36%5%34445%33%
47972
TransparencyDay
50%6%12%19%9%1
48323
Night
52%5%11%19%9%
47797
SeeingDay
21%10%27%23%12%4
5717
Night
22%9%28%27%10%
14944

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 15thDay
23%14%6%8%5%23435%21%
1432
16th to endDay
15%14%48%6%3445%5%25%
1575
February1st to 15thDay
13%12%412%7%45%44425%
1575
16th to endDay
17%12%5%7%6%44445%25%
1525
March1st to 15thDay
17%9%47%6%46%5%4427%
1844
16th to endDay
16%6%35%5%3445%5%39%
2193
April1st to 15thDay
23%9%35%414246%33%
2152
16th to endDay
20%7%26%5%2444436%
2248
May1st to 15thDay
20%6%46%5%34346%32%
2511
16th to endDay
18%6%25%6%35%45%6%34%
2618
June1st to 15thDay
21%5%26%6%35%45%7%30%
2520
16th to endDay
19%5%25%5%36%6%6%7%31%
2520
July1st to 15thDay
14%424435%6%7%9%37%
2520
16th to endDay
12%5%35%5%35%5%7%9%36%
2654
August1st to 15thDay
12%426%6%35%6%6%8%37%
2442
16th to endDay
11%4245%345%5%8%43%
2333
September1st to 15thDay
17%425%43435%6%42%
2160
16th to endDay
15%42342335%7%46%
2001
October1st to 15thDay
21%7%25%5%3445%5%34%
1800
16th to endDay
26%7%35%7%35%435%27%
1818
November1st to 15thDay
16%9%36%5%35%5%5%6%32%
1657
16th to endDay
24%11%36%5%34446%23%
1560
December1st to 15thDay
23%13%5%8%7%345%45%18%
1442
16th to endDay
23%16%48%6%25%33420%
1536
January1st to 15thNight
19%16%5%10%6%45%34419%
2506
16th to endNight
13%15%5%8%6%34436%27%
2646
February1st to 15thNight
13%11%7%11%7%36%445%24%
2285
16th to endNight
17%11%5%7%6%35%445%28%
1947
March1st to 15thNight
18%10%5%8%6%3433430%
2090
16th to endNight
15%7%35%6%2334441%
2031
April1st to 15thNight
24%7%34424345%35%
1796
16th to endNight
19%6%35%424346%37%
1722
May1st to 15thNight
23%6%3442435%6%35%
1440
16th to endNight
16%6%35%6%345%5%6%37%
1495
June1st to 15thNight
18%6%25%5%35%5%6%7%34%
1440
16th to endNight
16%5%15%425%6%6%6%37%
1440
July1st to 15thNight
11%314425%5%5%7%47%
1440
16th to endNight
10%4244345%6%8%45%
1514
August1st to 15thNight
11%5%25%4345%5%9%41%
1515
16th to endNight
10%32343445%6%50%
1857
September1st to 15thNight
15%5%25%5%33445%43%
1800
16th to endNight
17%314423235%49%
1956
October1st to 15thNight
20%6%24435%346%37%
2160
16th to endNight
24%8%26%6%35%436%28%
2406
November1st to 15thNight
21%7%36%5%34446%33%
2530
16th to endNight
22%10%48%6%34435%25%
2730
December1st to 15thNight
22%15%47%6%35%445%21%
2532
16th to endNight
24%14%5%8%6%2433420%
2688

Percentage Cloud Cover SE (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 15thDay
22%14%6%8%5%2444421%
1432
16th to endDay
14%15%47%7%45%45%5%25%
1575
February1st to 15thDay
14%13%411%6%45%5%45%24%
1575
16th to endDay
17%13%5%8%6%345%5%425%
1525
March1st to 15thDay
20%8%46%6%35%44330%
1854
16th to endDay
19%6%3443344441%
2192
April1st to 15thDay
22%9%36%423345%34%
2152
16th to endDay
20%7%35%5%2344437%
2248
May1st to 15thDay
24%6%35%5%24446%32%
2511
16th to endDay
22%6%25%5%3445%5%34%
2618
June1st to 15thDay
20%5%35%5%35%447%33%
2520
16th to endDay
17%5%25%5%36%5%6%7%35%
2520
July1st to 15thDay
13%424435%5%7%8%37%
2520
16th to endDay
12%5%26%5%35%5%7%9%37%
2654
August1st to 15thDay
18%4245%35%5%5%6%38%
2442
16th to endDay
16%41442445%7%43%
2333
September1st to 15thDay
16%5%15%5%245%47%42%
2160
16th to endDay
15%424323447%46%
2001
October1st to 15thDay
20%7%36%43445%5%34%
1800
16th to endDay
25%8%36%6%44435%27%
1818
November1st to 15thDay
16%8%45%4245%47%33%
1657
16th to endDay
23%11%36%6%34445%26%
1560
December1st to 15thDay
23%13%5%8%7%25%445%18%
1442
16th to endDay
24%15%5%8%6%35%33420%
1536
January1st to 15thNight
18%16%6%9%7%45%34419%
2506
16th to endNight
13%16%5%9%6%35%436%26%
2646
February1st to 15thNight
14%12%6%11%7%36%44424%
2278
16th to endNight
17%11%5%7%7%34436%27%
1947
March1st to 15thNight
23%9%47%5%2433432%
2103
16th to endNight
18%6%36%42323443%
2031
April1st to 15thNight
24%7%34333335%36%
1796
16th to endNight
19%6%35%423445%38%
1722
May1st to 15thNight
23%6%35%3235%45%36%
1440
16th to endNight
18%5%345%3445%6%37%
1495
June1st to 15thNight
18%5%35%5%35%46%6%35%
1440
16th to endNight
15%5%15%425%6%5%7%38%
1440
July1st to 15thNight
10%324335%5%6%7%46%
1440
16th to endNight
9%4244345%6%7%46%
1514
August1st to 15thNight
14%5%2443445%9%40%
1515
16th to endNight
13%31443345%6%50%
1857
September1st to 15thNight
15%5%26%5%3435%6%43%
1800
16th to endNight
16%415%323235%49%
1956
October1st to 15thNight
19%7%24434446%37%
2160
16th to endNight
24%8%26%5%44446%28%
2406
November1st to 15thNight
21%7%35%5%23345%36%
2530
16th to endNight
22%10%37%5%34335%28%
2730
December1st to 15thNight
23%16%47%5%24445%20%
2532
16th to endNight
26%14%5%8%6%2434320%
2688

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 15thDay
66%5%8%13%5%
1433
16th to endDay
61%6%12%12%7%
1575
February1st to 15thDay
61%412%16%4
1577
16th to endDay
59%5%10%14%8%1
1525
March1st to 15thDay
59%5%11%15%7%1
1854
16th to endDay
45%5%9%19%15%5%
2193
April1st to 15thDay
53%38%19%12%2
2152
16th to endDay
50%47%19%15%3
2248
May1st to 15thDay
51%5%8%19%13%2
2511
16th to endDay
48%7%11%18%11%1
2622
June1st to 15thDay
53%6%11%20%8%
2520
16th to endDay
47%8%13%19%9%
2520
July1st to 15thDay
38%8%14%25%11%
2371
16th to endDay
42%8%16%22%9%
2487
August1st to 15thDay
43%8%16%22%9%
2428
16th to endDay
36%6%17%28%9%
2333
September1st to 15thDay
41%6%13%26%11%
2160
16th to endDay
37%6%14%31%9%
2001
October1st to 15thDay
50%5%13%20%9%
1800
16th to endDay
59%6%13%14%6%
1818
November1st to 15thDay
50%6%15%19%7%
1657
16th to endDay
61%6%12%13%5%1
1560
December1st to 15thDay
67%6%12%10%2
1442
16th to endDay
68%5%10%10%5%
1536
January1st to 15thNight
68%410%11%5%
2506
16th to endNight
59%5%10%16%7%
2646
February1st to 15thNight
62%5%10%16%5%
2287
16th to endNight
57%5%9%17%9%
1947
March1st to 15thNight
58%310%18%8%1
2103
16th to endNight
47%39%20%15%4
2031
April1st to 15thNight
52%38%18%15%1
1796
16th to endNight
47%48%18%17%3
1722
May1st to 15thNight
50%47%18%15%4
1440
16th to endNight
44%5%13%20%13%2
1497
June1st to 15thNight
49%7%11%21%9%1
1440
16th to endNight
43%8%12%19%15%
1440
July1st to 15thNight
33%8%12%30%14%1
1360
16th to endNight
34%6%15%27%14%
1418
August1st to 15thNight
38%9%17%22%11%
1505
16th to endNight
32%6%16%31%11%
1857
September1st to 15thNight
42%7%11%26%11%1
1800
16th to endNight
37%410%35%10%
1956
October1st to 15thNight
47%5%10%24%11%
2160
16th to endNight
57%5%13%17%5%
2406
November1st to 15thNight
52%5%13%17%9%
2530
16th to endNight
62%5%11%15%4
2730
December1st to 15thNight
65%5%12%12%3
2532
16th to endNight
67%49%12%5%
2688

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 15thDay
26%13%28%25%5%1
60
16th to endDay
35%7%35%16%5%
71
February1st to 15thDay
33%15%36%13%1
90
16th to endDay
32%17%22%20%6%
184
March1st to 15thDay
25%12%33%21%6%
270
16th to endDay
21%13%29%21%10%3
288
April1st to 15thDay
26%19%28%17%7%
270
16th to endDay
23%14%28%16%14%3
270
May1st to 15thDay
27%9%30%18%10%3
288
16th to endDay
18%14%31%19%14%1
331
June1st to 15thDay
25%8%29%25%9%2
315
16th to endDay
21%8%25%27%14%1
315
July1st to 15thDay
14%329%31%15%5%
305
16th to endDay
12%324%33%18%6%
326
August1st to 15thDay
12%5%22%32%20%6%
313
16th to endDay
10%6%23%29%18%11%
332
September1st to 15thDay
18%5%21%20%19%13%
315
16th to endDay
15%8%20%23%20%12%
314
October1st to 15thDay
22%9%26%25%13%3
315
16th to endDay
27%15%25%22%8%
310
November1st to 15thDay
22%11%26%26%11%1
221
16th to endDay
28%21%26%21%2
90
December1st to 15thDay
18%15%38%26%1
60
16th to endDay
39%17%35%7%
64
January1st to 15thNight
26%14%31%21%5%
720
16th to endNight
22%8%35%27%5%
768
February1st to 15thNight
20%12%35%26%5%
704
16th to endNight
24%12%30%27%5%
631
March1st to 15thNight
24%13%33%25%2
720
16th to endNight
20%13%27%27%10%
768
April1st to 15thNight
26%11%32%24%4
718
16th to endNight
23%13%28%26%8%
642
May1st to 15thNight
24%8%25%30%9%1
360
16th to endNight
19%5%31%31%11%
375
June1st to 15thNight
20%329%35%10%
360
16th to endNight
18%5%25%35%13%1
360
July1st to 15thNight
10%224%44%17%
340
16th to endNight
9%224%42%19%1
376
August1st to 15thNight
15%318%36%23%2
434
16th to endNight
11%420%37%24%1
711
September1st to 15thNight
17%422%33%20%2
720
16th to endNight
18%6%22%25%24%2
717
October1st to 15thNight
23%7%27%26%13%1
720
16th to endNight
28%12%24%26%7%
768
November1st to 15thNight
25%10%29%23%11%
760
16th to endNight
29%15%26%19%8%
780
December1st to 15thNight
30%13%30%22%3
724
16th to endNight
32%10%32%18%41
768
Page generated at 2017-12-02 09:14:24. Version ac04

Copyright 2017 A. Danko


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