Les Coteaux
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Les Coteaux clear sky chart from 2005-11-05 to 2017-12-20.

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
27%
15031
13%
48049
8%
15001
34%
15001
15%
34517

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
15%
720
7%
2506
3%
716
20%
716
7%
2028
January16th to endNight
18%
768
10%
2688
5%
768
25%
768
9%
2027
February1st to 15thNight
16%
703
9%
2290
4%
701
22%
701
9%
1818
February16th to endNight
21%
631
12%
1901
6%
631
29%
631
12%
1440
March1st to 15thNight
18%
720
12%
2157
7%
720
25%
720
13%
1625
March16th to endNight
27%
768
19%
1994
8%
768
35%
768
20%
1415
April1st to 15thNight
25%
718
16%
1796
5%
718
30%
718
19%
1349
April16th to endNight
25%
642
16%
1722
3%
642
34%
642
19%
1229
May1st to 15thNight
28%
381
17%
1461
12%
381
41%
381
14%
981
May16th to endNight
30%
374
12%
1497
8%
374
42%
374
15%
986
June1st to 15thNight
29%
360
9%
1440
8%
360
38%
360
12%
1001
June16th to endNight
36%
360
9%
1440
9%
360
44%
360
17%
905
July1st to 15thNight
46%
340
15%
1360
19%
340
54%
340
24%
762
July16th to endNight
44%
376
13%
1418
12%
354
55%
354
23%
826
August1st to 15thNight
50%
380
15%
1451
14%
378
55%
378
21%
861
August16th to endNight
48%
757
20%
1903
9%
757
53%
757
34%
1221
September1st to 15thNight
47%
720
15%
1800
8%
720
48%
720
28%
1238
September16th to endNight
48%
717
23%
1959
16%
717
52%
717
30%
1248
October1st to 15thNight
32%
720
18%
2137
11%
720
41%
720
19%
1475
October16th to endNight
23%
768
11%
2445
7%
768
29%
768
13%
1844
November1st to 15thNight
25%
760
15%
2472
10%
760
33%
760
14%
1766
November16th to endNight
17%
780
11%
2727
5%
780
26%
780
10%
2054
December1st to 15thNight
14%
780
7%
2730
3%
780
20%
780
7%
2176
December16th to endNight
10%
788
8%
2755
3%
788
16%
788
6%
2242

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
17%8%36%5%3445%7%33%
48800
Night
18%9%46%5%34446%31%
48218
Cloud CoverDay
17%8%36%5%3445%6%33%
48809
Night
18%10%46%5%34446%30%
48224
TransparencyDay
50%412%20%9%1
48487
Night
53%411%19%9%1
48049
SeeingDay
19%15%24%23%12%4
5845
Night
20%20%24%24%9%
15033

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
22%14%47%8%35%43420%
1432
16th to endDay
14%14%5%7%7%35%46%7%23%
1536
February1st to 15thDay
14%13%5%10%6%26%5%5%6%23%
1569
16th to endDay
17%12%5%8%6%4435%5%27%
1572
March1st to 15thDay
17%11%49%6%3443428%
1791
16th to endDay
19%6%35%424445%38%
2229
April1st to 15thDay
21%8%35%6%25%445%32%
2152
16th to endDay
19%6%26%5%2345%5%37%
2238
May1st to 15thDay
19%6%35%5%345%5%6%34%
2500
16th to endDay
18%6%25%5%34448%36%
2618
June1st to 15thDay
23%5%35%5%2446%6%32%
2520
16th to endDay
16%6%25%5%36%5%7%8%32%
2520
July1st to 15thDay
12%426%5%3446%8%40%
2520
16th to endDay
12%425%5%36%6%7%9%37%
2654
August1st to 15thDay
12%5%26%6%46%5%6%8%35%
2491
16th to endDay
9%314425%5%6%9%45%
2292
September1st to 15thDay
16%4245%34347%43%
2160
16th to endDay
13%5%24323347%48%
2001
October1st to 15thDay
19%8%25%5%24446%35%
1821
16th to endDay
23%9%37%5%35%446%26%
1779
November1st to 15thDay
16%10%36%5%245%5%7%32%
1716
16th to endDay
21%9%47%6%345%46%25%
1561
December1st to 15thDay
23%13%5%8%5%45%45%6%16%
1560
16th to endDay
26%15%48%5%3434418%
1568
January1st to 15thNight
18%15%6%9%7%345%4419%
2506
16th to endNight
13%16%6%8%6%35%445%25%
2688
February1st to 15thNight
14%14%6%11%8%45%5%45%20%
2288
16th to endNight
16%12%5%9%6%45%35%5%26%
1901
March1st to 15thNight
20%11%47%6%35%345%28%
2144
16th to endNight
19%9%45%424245%38%
1994
April1st to 15thNight
26%8%25%5%23445%31%
1796
16th to endNight
20%7%45%423445%36%
1722
May1st to 15thNight
21%8%35%5%24345%35%
1461
16th to endNight
19%435%5%35%45%7%35%
1495
June1st to 15thNight
23%7%35%5%245%5%7%29%
1440
16th to endNight
16%5%26%4345%6%9%36%
1440
July1st to 15thNight
10%424426%5%7%8%42%
1440
16th to endNight
10%5%25%435%5%6%9%42%
1514
August1st to 15thNight
11%5%25%5%345%6%8%41%
1461
16th to endNight
12%424424448%47%
1903
September1st to 15thNight
15%6%25%5%24446%42%
1800
16th to endNight
16%324424346%47%
1959
October1st to 15thNight
19%7%25%5%25%445%37%
2137
16th to endNight
23%8%37%6%44345%27%
2445
November1st to 15thNight
21%8%46%5%34445%31%
2472
16th to endNight
21%10%5%8%5%2345%5%25%
2727
December1st to 15thNight
22%15%5%8%6%34445%19%
2730
16th to endNight
25%16%5%7%6%24335%19%
2755

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
21%15%5%7%8%36%33420%
1432
16th to endDay
13%15%49%6%35%5%6%7%22%
1536
February1st to 15thDay
15%12%5%10%7%36%5%5%6%21%
1569
16th to endDay
16%12%6%8%7%35%346%26%
1572
March1st to 15thDay
17%10%6%9%7%345%4328%
1801
16th to endDay
18%8%35%434436%38%
2228
April1st to 15thDay
21%7%35%6%35%44432%
2152
16th to endDay
19%6%35%5%3345%5%37%
2238
May1st to 15thDay
19%6%25%5%3445%6%34%
2500
16th to endDay
17%7%35%5%2445%8%36%
2618
June1st to 15thDay
23%6%25%5%2445%7%32%
2520
16th to endDay
16%5%25%5%35%5%6%7%33%
2520
July1st to 15thDay
12%425%435%46%8%40%
2520
16th to endDay
11%425%5%35%6%7%10%36%
2654
August1st to 15thDay
13%5%26%5%45%5%6%8%35%
2491
16th to endDay
9%3244346%6%9%45%
2292
September1st to 15thDay
15%5%245%3435%7%43%
2160
16th to endDay
12%5%2432335%6%48%
2001
October1st to 15thDay
19%7%345%3445%7%33%
1821
16th to endDay
23%10%37%43345%5%27%
1779
November1st to 15thDay
16%10%46%43446%7%30%
1716
16th to endDay
20%11%5%8%6%335%5%5%24%
1561
December1st to 15thDay
22%14%6%9%6%46%445%15%
1560
16th to endDay
25%16%6%7%6%25%43417%
1568
January1st to 15thNight
17%16%6%9%7%45%445%18%
2506
16th to endNight
13%16%6%8%6%35%445%24%
2688
February1st to 15thNight
14%14%6%11%8%45%5%4419%
2281
16th to endNight
15%12%6%9%6%35%445%25%
1901
March1st to 15thNight
20%11%47%6%35%335%27%
2157
16th to endNight
19%9%35%42434437%
1994
April1st to 15thNight
25%8%25%5%33445%30%
1796
16th to endNight
21%8%25%334445%36%
1722
May1st to 15thNight
21%8%36%424346%34%
1461
16th to endNight
19%5%25%6%2435%7%35%
1495
June1st to 15thNight
24%7%35%425%45%7%28%
1440
16th to endNight
16%5%25%5%245%6%8%37%
1440
July1st to 15thNight
10%424435%6%6%9%41%
1440
16th to endNight
10%5%244345%7%8%41%
1514
August1st to 15thNight
10%5%25%5%345%6%8%41%
1461
16th to endNight
12%414424348%47%
1903
September1st to 15thNight
15%5%25%5%24346%42%
1800
16th to endNight
16%42442345%5%46%
1959
October1st to 15thNight
18%8%25%5%24446%36%
2137
16th to endNight
24%8%37%7%3435%426%
2445
November1st to 15thNight
21%9%36%5%34445%30%
2472
16th to endNight
21%10%5%9%5%2434425%
2727
December1st to 15thNight
22%15%6%7%6%34445%18%
2730
16th to endNight
25%16%5%8%6%3432419%
2755

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
69%37%13%5%
1433
16th to endDay
61%312%14%6%
1536
February1st to 15thDay
62%412%17%3
1571
16th to endDay
60%311%14%8%1
1572
March1st to 15thDay
59%313%14%7%
1801
16th to endDay
47%49%18%15%4
2229
April1st to 15thDay
53%37%20%11%2
2152
16th to endDay
47%39%19%14%3
2238
May1st to 15thDay
49%310%19%14%1
2500
16th to endDay
46%413%21%12%1
2622
June1st to 15thDay
51%5%11%20%11%
2520
16th to endDay
46%6%13%21%10%
2520
July1st to 15thDay
38%6%13%28%11%
2371
16th to endDay
39%7%19%24%8%
2487
August1st to 15thDay
44%6%17%23%8%
2477
16th to endDay
33%418%29%12%
2292
September1st to 15thDay
40%413%28%13%
2160
16th to endDay
36%5%12%33%11%
2001
October1st to 15thDay
49%5%12%24%9%
1821
16th to endDay
59%413%16%6%
1779
November1st to 15thDay
50%5%15%18%8%
1716
16th to endDay
59%6%11%16%6%
1561
December1st to 15thDay
68%5%11%11%2
1560
16th to endDay
69%5%10%9%4
1568
January1st to 15thNight
68%410%11%4
2506
16th to endNight
61%410%15%7%
2688
February1st to 15thNight
66%410%15%3
2290
16th to endNight
59%410%15%9%
1901
March1st to 15thNight
59%310%17%8%1
2157
16th to endNight
49%39%19%14%4
1994
April1st to 15thNight
55%27%19%13%
1796
16th to endNight
49%48%18%16%3
1722
May1st to 15thNight
51%37%16%16%4
1461
16th to endNight
47%6%10%20%12%2
1497
June1st to 15thNight
52%7%11%19%9%
1440
16th to endNight
44%5%14%21%13%
1440
July1st to 15thNight
34%6%14%28%15%
1360
16th to endNight
36%7%17%23%14%
1418
August1st to 15thNight
38%6%20%23%11%
1451
16th to endNight
35%416%30%12%
1903
September1st to 15thNight
43%411%26%13%
1800
16th to endNight
38%410%33%12%
1959
October1st to 15thNight
47%5%10%26%9%
2137
16th to endNight
59%412%17%5%
2445
November1st to 15thNight
54%412%17%8%2
2472
16th to endNight
60%412%16%5%
2727
December1st to 15thNight
66%412%12%3
2730
16th to endNight
69%410%11%4
2755

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
25%16%21%23%11%1
60
16th to endDay
35%10%28%18%33
64
February1st to 15thDay
32%13%39%13%1
89
16th to endDay
26%18%27%24%3
231
March1st to 15thDay
20%22%31%19%5%
270
16th to endDay
23%19%23%21%9%2
288
April1st to 15thDay
25%21%27%16%8%1
270
16th to endDay
17%21%25%20%12%2
270
May1st to 15thDay
23%19%24%18%10%3
288
16th to endDay
20%17%28%16%12%3
331
June1st to 15thDay
23%15%23%26%9%1
315
16th to endDay
17%14%23%29%13%1
315
July1st to 15thDay
13%9%26%28%15%5%
305
16th to endDay
13%12%18%33%19%3
326
August1st to 15thDay
10%10%19%35%17%6%
313
16th to endDay
9%9%21%26%20%12%
332
September1st to 15thDay
14%11%20%21%17%13%
315
16th to endDay
13%11%20%20%22%11%
314
October1st to 15thDay
20%12%23%20%18%4
315
16th to endDay
24%16%28%21%8%
301
November1st to 15thDay
21%20%23%19%13%1
280
16th to endDay
29%15%25%21%7%
91
December1st to 15thDay
28%8%30%25%6%
90
16th to endDay
40%11%33%15%
72
January1st to 15thNight
19%28%25%21%4
720
16th to endNight
20%25%27%20%5%
768
February1st to 15thNight
17%24%29%23%4
704
16th to endNight
20%23%27%22%5%
631
March1st to 15thNight
23%24%27%20%4
720
16th to endNight
20%22%23%25%7%
768
April1st to 15thNight
23%22%24%25%4
718
16th to endNight
20%24%24%20%9%
642
May1st to 15thNight
20%22%20%24%8%1
381
16th to endNight
15%19%29%25%9%
375
June1st to 15thNight
21%20%21%28%7%
360
16th to endNight
16%19%21%27%13%1
360
July1st to 15thNight
11%14%21%32%19%1
340
16th to endNight
12%18%19%34%13%1
376
August1st to 15thNight
12%11%15%37%21%1
380
16th to endNight
12%10%21%30%23%1
757
September1st to 15thNight
16%11%18%35%15%2
720
16th to endNight
17%13%17%26%23%2
717
October1st to 15thNight
20%14%25%24%13%
720
16th to endNight
24%17%28%22%6%
768
November1st to 15thNight
20%21%25%21%9%
760
16th to endNight
21%26%26%15%10%
780
December1st to 15thNight
28%25%25%18%3
780
16th to endNight
29%25%25%14%31
788
Page generated at 2017-12-21 07:04:52. Version ac04

Copyright 2017 A. Danko


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