Québec
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Québec clear sky chart from 2005-11-05 to 2018-02-22.

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
25%
15291
12%
48966
6%
15260
32%
15260
13%
35963

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
13%
780
10%
2716
3%
776
21%
776
8%
2134
January16th to endNight
19%
832
11%
2912
4%
832
29%
832
9%
2187
February1st to 15thNight
19%
763
10%
2558
4%
761
27%
761
10%
1957
February16th to endNight
16%
659
12%
1976
4%
659
25%
659
10%
1543
March1st to 15thNight
20%
720
14%
2160
7%
720
28%
720
13%
1606
March16th to endNight
28%
768
17%
2022
8%
768
35%
768
18%
1467
April1st to 15thNight
23%
718
15%
1796
5%
718
28%
718
16%
1384
April16th to endNight
23%
540
16%
1620
4%
540
33%
540
16%
1124
May1st to 15thNight
25%
456
13%
1536
9%
456
33%
456
13%
1095
May16th to endNight
26%
375
10%
1476
9%
374
35%
374
12%
1037
June1st to 15thNight
28%
360
6%
1260
4%
360
32%
360
12%
922
June16th to endNight
35%
360
7%
1260
7%
360
38%
360
14%
883
July1st to 15thNight
37%
340
8%
1332
10%
340
41%
340
17%
884
July16th to endNight
40%
376
9%
1418
11%
354
46%
354
17%
932
August1st to 15thNight
46%
416
10%
1487
10%
414
49%
414
17%
1005
August16th to endNight
42%
642
15%
1788
8%
642
46%
642
23%
1188
September1st to 15thNight
36%
720
11%
1848
5%
720
38%
720
24%
1303
September16th to endNight
41%
717
18%
1980
12%
717
46%
717
28%
1314
October1st to 15thNight
31%
720
16%
2082
8%
720
38%
720
20%
1477
October16th to endNight
22%
768
10%
2496
5%
768
29%
768
13%
1860
November1st to 15thNight
27%
760
15%
2472
10%
760
34%
760
13%
1791
November16th to endNight
22%
805
13%
2765
6%
805
32%
805
11%
2067
December1st to 15thNight
13%
825
6%
2925
1%
825
18%
825
6%
2368
December16th to endNight
12%
871
11%
3081
4%
871
21%
871
7%
2435

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%8%36%5%3445%6%30%
49285
Night
20%10%36%5%34445%30%
49136
TransparencyDay
53%6%12%18%8%
48973
Night
55%5%11%17%8%
48966
SeeingDay
23%18%24%20%10%2
6486
Night
22%21%23%23%7%
15292

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
20%13%6%8%6%34345%23%
1552
16th to endDay
11%13%5%8%6%45%5%5%5%26%
1664
February1st to 15thDay
10%14%6%9%6%35%45%6%26%
1630
16th to endDay
15%12%6%8%7%35%5%46%25%
1644
March1st to 15thDay
18%11%46%5%23445%31%
1790
16th to endDay
15%10%36%5%345%5%6%34%
2199
April1st to 15thDay
23%9%35%5%34345%33%
2152
16th to endDay
23%7%24423435%37%
2340
May1st to 15thDay
24%6%26%425%347%31%
2424
16th to endDay
22%6%26%6%45%5%5%6%27%
2636
June1st to 15thDay
21%5%35%6%36%5%6%7%28%
2700
16th to endDay
22%7%36%6%35%46%7%26%
2700
July1st to 15thDay
15%5%26%5%36%5%7%9%30%
2545
16th to endDay
17%5%37%5%45%5%6%9%29%
2654
August1st to 15thDay
17%6%25%6%35%6%6%9%28%
2451
16th to endDay
14%416%5%4445%8%39%
2412
September1st to 15thDay
20%7%25%323446%39%
2112
16th to endDay
19%5%24323247%43%
1980
October1st to 15thDay
23%7%25%5%245%47%31%
1877
16th to endDay
27%9%36%5%335%5%5%24%
1728
November1st to 15thDay
21%9%37%6%34345%29%
1716
16th to endDay
26%14%35%42333426%
1521
December1st to 15thDay
25%17%45%5%33325%23%
1365
16th to endDay
22%16%6%7%5%23445%21%
1493
January1st to 15thNight
19%16%5%8%7%3433423%
2716
16th to endNight
12%15%5%8%7%45%5%45%24%
2912
February1st to 15thNight
10%12%6%9%10%45%5%45%25%
2557
16th to endNight
16%14%6%9%6%35%33425%
1976
March1st to 15thNight
19%11%36%6%35%445%31%
2147
16th to endNight
15%10%25%5%34446%36%
2022
April1st to 15thNight
23%10%5%5%5%23445%28%
1796
16th to endNight
22%8%25%423336%38%
1620
May1st to 15thNight
24%7%25%5%34435%32%
1536
16th to endNight
26%6%245%3435%6%31%
1474
June1st to 15thNight
24%7%25%6%3445%7%27%
1260
16th to endNight
21%6%35%5%25%5%5%7%31%
1260
July1st to 15thNight
18%6%25%425%448%35%
1412
16th to endNight
16%5%25%5%35%46%8%36%
1514
August1st to 15thNight
16%6%246%25%6%6%8%34%
1497
16th to endNight
15%325%5%4445%8%39%
1788
September1st to 15thNight
20%7%25%5%23336%39%
1848
16th to endNight
21%5%22324246%45%
1980
October1st to 15thNight
21%7%25%424446%36%
2082
16th to endNight
26%10%35%5%22445%28%
2496
November1st to 15thNight
20%8%26%5%3435%5%32%
2472
16th to endNight
24%11%45%42433429%
2765
December1st to 15thNight
23%15%5%8%6%3432420%
2925
16th to endNight
21%15%5%10%6%2333423%
3081

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
63%6%9%13%6%
1553
16th to endDay
58%5%10%18%7%
1664
February1st to 15thDay
58%414%14%6%1
1633
16th to endDay
58%6%9%16%7%2
1644
March1st to 15thDay
54%411%15%12%1
1800
16th to endDay
49%6%9%18%12%2
2199
April1st to 15thDay
54%39%17%9%4
2152
16th to endDay
49%411%18%13%2
2340
May1st to 15thDay
52%5%12%17%11%1
2424
16th to endDay
56%7%10%17%7%
2640
June1st to 15thDay
52%8%13%16%8%1
2700
16th to endDay
55%8%11%16%8%
2700
July1st to 15thDay
45%10%17%20%6%
2396
16th to endDay
51%8%17%17%5%
2487
August1st to 15thDay
49%10%18%16%3
2437
16th to endDay
40%8%16%26%7%
2412
September1st to 15thDay
44%6%16%22%9%
2112
16th to endDay
41%5%15%29%8%
1980
October1st to 15thDay
51%6%13%20%6%
1877
16th to endDay
61%6%11%18%3
1728
November1st to 15thDay
56%6%11%19%6%
1716
16th to endDay
62%410%16%5%
1521
December1st to 15thDay
65%410%13%5%
1365
16th to endDay
65%47%13%7%
1493
January1st to 15thNight
65%48%15%4
2716
16th to endNight
60%49%16%7%
2912
February1st to 15thNight
60%5%11%15%6%
2558
16th to endNight
62%5%8%13%9%1
1976
March1st to 15thNight
56%5%9%15%11%2
2160
16th to endNight
49%5%9%18%12%3
2022
April1st to 15thNight
56%46%17%11%2
1796
16th to endNight
48%5%9%17%15%3
1620
May1st to 15thNight
54%5%9%16%13%1
1536
16th to endNight
53%6%11%16%11%
1476
June1st to 15thNight
57%5%13%16%6%1
1260
16th to endNight
51%6%11%18%11%
1260
July1st to 15thNight
45%8%16%20%7%
1332
16th to endNight
45%7%18%19%8%
1418
August1st to 15thNight
44%10%19%21%4
1487
16th to endNight
42%6%17%26%6%
1788
September1st to 15thNight
46%5%13%23%9%
1848
16th to endNight
41%5%15%26%10%
1980
October1st to 15thNight
49%5%11%23%8%
2082
16th to endNight
57%5%13%17%5%
2496
November1st to 15thNight
52%7%13%17%8%
2472
16th to endNight
59%411%17%6%
2765
December1st to 15thNight
68%5%10%11%4
2925
16th to endNight
65%48%12%7%
3081

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
27%18%32%20%1
90
16th to endDay
19%27%33%15%4
96
February1st to 15thDay
23%25%34%11%6%
164
16th to endDay
24%18%28%22%5%
265
March1st to 15thDay
21%26%25%20%4
270
16th to endDay
20%20%22%21%11%3
288
April1st to 15thDay
27%20%23%18%10%
270
16th to endDay
23%21%25%18%8%1
270
May1st to 15thDay
31%17%24%17%6%3
288
16th to endDay
22%22%26%18%7%1
349
June1st to 15thDay
22%19%22%25%9%
495
16th to endDay
23%20%23%22%9%1
495
July1st to 15thDay
19%16%24%24%12%2
330
16th to endDay
15%15%26%27%13%2
326
August1st to 15thDay
17%11%23%26%17%4
313
16th to endDay
18%11%25%20%16%7%
332
September1st to 15thDay
20%15%23%19%16%4
315
16th to endDay
15%15%22%21%18%5%
314
October1st to 15thDay
25%14%25%20%11%3
304
16th to endDay
31%19%20%18%9%
288
November1st to 15thDay
25%22%22%18%10%
280
16th to endDay
35%15%24%17%6%
158
December1st to 15thDay
36%15%27%14%32
90
16th to endDay
32%20%31%10%41
96
January1st to 15thNight
22%26%27%20%3
780
16th to endNight
18%27%26%21%5%
832
February1st to 15thNight
14%25%30%23%6%
764
16th to endNight
25%23%27%19%3
659
March1st to 15thNight
22%25%27%20%4
720
16th to endNight
17%23%24%25%7%1
768
April1st to 15thNight
24%24%22%22%5%
718
16th to endNight
22%24%25%20%6%
540
May1st to 15thNight
23%23%23%23%5%
456
16th to endNight
28%20%21%23%6%
375
June1st to 15thNight
23%20%22%27%5%
360
16th to endNight
19%18%19%30%11%
360
July1st to 15thNight
19%15%22%26%15%1
340
16th to endNight
16%18%17%36%10%
376
August1st to 15thNight
18%11%13%36%18%
416
16th to endNight
16%11%23%32%14%1
642
September1st to 15thNight
21%11%23%28%13%
720
16th to endNight
20%12%20%28%16%
717
October1st to 15thNight
22%15%24%27%8%1
720
16th to endNight
28%19%24%21%5%
768
November1st to 15thNight
20%23%22%23%9%
760
16th to endNight
25%25%21%19%7%
805
December1st to 15thNight
28%24%24%16%5%
825
16th to endNight
26%26%23%17%41
871
Page generated at 2018-02-23 11:21:32. Version ac04

Copyright 2018 A. Danko


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