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 2017-04-01.

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
25%
14177
12%
45434
6%
14146
32%
14146
13%
33436

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
12%
720
10%
2506
3%
716
21%
716
8%
1979
January16th to endNight
19%
768
11%
2688
4%
768
29%
768
8%
2025
February1st to 15thNight
19%
703
10%
2358
5%
701
27%
701
10%
1790
February16th to endNight
16%
631
11%
1893
4%
631
25%
631
10%
1479
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%
662
15%
1656
6%
662
28%
662
16%
1270
April16th to endNight
24%
495
16%
1485
4%
495
34%
495
17%
1021
May1st to 15thNight
26%
418
14%
1408
9%
418
35%
418
14%
985
May16th to endNight
25%
343
10%
1350
8%
342
35%
342
12%
948
June1st to 15thNight
26%
330
7%
1155
4%
330
30%
330
11%
857
June16th to endNight
35%
330
7%
1155
6%
330
38%
330
14%
804
July1st to 15thNight
37%
310
8%
1214
10%
310
41%
310
17%
796
July16th to endNight
37%
348
7%
1306
9%
326
44%
326
15%
876
August1st to 15thNight
46%
381
11%
1362
11%
379
49%
379
17%
921
August16th to endNight
41%
588
14%
1638
7%
588
45%
588
23%
1091
September1st to 15thNight
35%
660
11%
1694
5%
660
37%
660
23%
1208
September16th to endNight
39%
657
18%
1815
11%
657
44%
657
27%
1218
October1st to 15thNight
29%
660
17%
1908
9%
660
36%
660
19%
1378
October16th to endNight
22%
704
9%
2288
4%
704
28%
704
13%
1713
November1st to 15thNight
27%
700
15%
2277
10%
700
35%
700
14%
1646
November16th to endNight
22%
737
12%
2552
6%
737
32%
737
11%
1906
December1st to 15thNight
13%
750
6%
2700
1%
750
19%
750
6%
2179
December16th to endNight
12%
794
10%
2844
3%
794
20%
794
6%
2273

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
19%8%36%5%3445%6%30%
45669
Night
20%10%46%5%34445%30%
45604
TransparencyDay
53%6%12%18%8%
45357
Night
55%5%11%17%8%
45434
SeeingDay
23%19%23%20%10%2
5357
Night
21%22%23%23%7%
14178

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
19%12%6%8%6%34345%24%
1432
16th to endDay
11%14%5%8%6%45%45%6%26%
1536
February1st to 15thDay
10%14%7%9%7%35%446%26%
1501
16th to endDay
15%12%6%8%7%45%5%46%25%
1580
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
21%9%35%5%34345%33%
1978
16th to endDay
22%7%24423435%38%
2145
May1st to 15thDay
22%6%25%5%25%347%33%
2221
16th to endDay
22%6%36%6%45%5%5%6%27%
2410
June1st to 15thDay
23%5%35%5%36%5%6%7%27%
2475
16th to endDay
21%7%36%6%36%46%7%26%
2475
July1st to 15thDay
14%6%26%5%36%6%7%9%30%
2333
16th to endDay
17%5%37%5%45%5%6%9%28%
2458
August1st to 15thDay
18%6%35%6%35%6%6%9%27%
2247
16th to endDay
14%5%16%5%3445%8%39%
2210
September1st to 15thDay
20%6%24333447%38%
1936
16th to endDay
20%6%24323237%42%
1815
October1st to 15thDay
24%7%25%5%345%47%30%
1721
16th to endDay
27%10%36%5%345%5%422%
1584
November1st to 15thDay
21%9%37%6%34345%30%
1581
16th to endDay
26%14%35%42333427%
1404
December1st to 15thDay
26%17%45%423325%23%
1260
16th to endDay
23%17%6%7%5%2334421%
1378
January1st to 15thNight
19%15%6%8%7%3433422%
2506
16th to endNight
12%15%5%8%7%45%5%45%24%
2688
February1st to 15thNight
10%12%5%9%10%45%5%45%26%
2357
16th to endNight
16%14%6%9%6%35%34425%
1893
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%45%5%23445%29%
1656
16th to endNight
21%7%25%422336%39%
1485
May1st to 15thNight
21%7%346%34445%34%
1408
16th to endNight
27%5%245%3435%6%31%
1348
June1st to 15thNight
25%7%25%6%345%5%7%26%
1155
16th to endNight
21%6%35%5%25%5%5%6%32%
1155
July1st to 15thNight
18%6%25%425%5%5%8%36%
1294
16th to endNight
17%5%25%5%35%46%8%34%
1402
August1st to 15thNight
16%6%245%25%6%6%9%34%
1372
16th to endNight
16%325%5%4445%8%38%
1638
September1st to 15thNight
20%7%25%5%23336%38%
1694
16th to endNight
22%5%23224245%44%
1815
October1st to 15thNight
21%7%35%5%24445%35%
1908
16th to endNight
25%11%35%5%22445%28%
2288
November1st to 15thNight
20%8%26%5%3435%6%32%
2277
16th to endNight
24%11%46%42433429%
2552
December1st to 15thNight
24%15%5%8%6%3432421%
2700
16th to endNight
22%15%5%9%6%2332422%
2844

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
62%6%10%13%6%
1433
16th to endDay
58%5%10%17%7%
1536
February1st to 15thDay
58%414%13%7%
1504
16th to endDay
58%6%9%15%7%2
1580
March1st to 15thDay
54%411%15%12%1
1800
16th to endDay
49%6%9%18%12%2
2199
April1st to 15thDay
54%38%17%10%4
1978
16th to endDay
48%410%19%14%2
2145
May1st to 15thDay
50%5%11%19%12%1
2221
16th to endDay
56%7%9%17%7%
2414
June1st to 15thDay
53%8%13%15%7%1
2475
16th to endDay
55%7%11%16%8%
2475
July1st to 15thDay
44%10%17%20%6%
2184
16th to endDay
52%7%17%15%5%
2291
August1st to 15thDay
50%10%18%15%4
2233
16th to endDay
40%8%17%26%7%
2210
September1st to 15thDay
44%6%16%22%9%
1936
16th to endDay
43%414%29%8%
1815
October1st to 15thDay
52%6%13%19%7%
1721
16th to endDay
62%6%10%17%3
1584
November1st to 15thDay
56%6%10%19%7%
1581
16th to endDay
62%411%17%5%
1404
December1st to 15thDay
65%411%14%4
1260
16th to endDay
66%5%7%13%6%
1378
January1st to 15thNight
66%48%15%4
2506
16th to endNight
61%49%17%6%
2688
February1st to 15thNight
59%5%11%15%6%
2358
16th to endNight
62%5%8%13%9%
1893
March1st to 15thNight
56%5%9%15%11%2
2160
16th to endNight
49%5%9%18%12%3
2022
April1st to 15thNight
55%5%7%17%11%3
1656
16th to endNight
47%5%9%17%16%3
1485
May1st to 15thNight
52%5%9%17%14%2
1408
16th to endNight
53%5%11%16%11%
1350
June1st to 15thNight
58%413%15%6%1
1155
16th to endNight
50%6%10%18%12%
1155
July1st to 15thNight
44%8%16%21%7%
1214
16th to endNight
47%7%17%18%8%
1306
August1st to 15thNight
44%9%19%22%3
1362
16th to endNight
43%5%18%25%6%
1638
September1st to 15thNight
47%5%14%22%9%1
1694
16th to endNight
42%5%13%27%10%
1815
October1st to 15thNight
51%5%11%22%8%
1908
16th to endNight
58%5%13%17%5%
2288
November1st to 15thNight
52%7%14%16%8%
2277
16th to endNight
59%411%17%6%
2552
December1st to 15thNight
68%410%11%4
2700
16th to endNight
67%48%11%7%
2844

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
23%18%35%21%1
60
16th to endDay
25%21%28%18%6%
64
February1st to 15thDay
20%25%32%13%8%
125
16th to endDay
23%19%26%23%6%
239
March1st to 15thDay
21%26%25%20%4
270
16th to endDay
20%20%22%21%11%3
288
April1st to 15thDay
21%25%24%17%10%
212
16th to endDay
20%24%22%19%10%1
210
May1st to 15thDay
25%20%25%18%7%3
228
16th to endDay
21%21%25%20%8%1
283
June1st to 15thDay
25%21%19%23%9%
420
16th to endDay
23%20%22%22%10%1
420
July1st to 15thDay
17%18%23%24%13%2
268
16th to endDay
16%16%24%28%12%2
270
August1st to 15thDay
19%12%20%23%18%5%
253
16th to endDay
19%10%23%23%17%5%
268
September1st to 15thDay
20%14%22%19%17%5%
255
16th to endDay
19%17%21%20%16%5%
254
October1st to 15thDay
26%14%25%18%12%4
248
16th to endDay
34%17%19%20%7%
240
November1st to 15thDay
24%23%20%19%10%
235
16th to endDay
33%16%21%19%8%
123
December1st to 15thDay
40%13%28%13%5%
60
16th to endDay
39%20%31%6%3
64
January1st to 15thNight
21%28%26%19%3
720
16th to endNight
17%27%26%21%6%
768
February1st to 15thNight
13%25%30%23%6%
704
16th to endNight
24%23%27%20%4
631
March1st to 15thNight
22%25%27%20%4
720
16th to endNight
17%23%24%25%7%1
768
April1st to 15thNight
22%26%22%22%5%
662
16th to endNight
20%25%25%20%7%
495
May1st to 15thNight
20%24%23%24%6%
418
16th to endNight
27%22%20%23%5%
343
June1st to 15thNight
24%22%22%24%6%
330
16th to endNight
19%20%17%31%11%
330
July1st to 15thNight
17%16%23%26%14%1
310
16th to endNight
16%20%18%34%9%
348
August1st to 15thNight
18%12%13%34%19%1
381
16th to endNight
16%12%23%32%13%1
588
September1st to 15thNight
21%13%23%27%13%
660
16th to endNight
21%13%20%28%15%
657
October1st to 15thNight
23%16%24%26%7%1
660
16th to endNight
28%19%25%21%5%
704
November1st to 15thNight
19%24%23%23%8%
700
16th to endNight
25%26%20%19%7%
737
December1st to 15thNight
28%26%23%17%5%
750
16th to endNight
28%26%22%16%5%1
794
Page generated at 2017-04-02 07:39:07. Version ac04

Copyright 2017 A. Danko


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