Lac des Iles
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac des Iles clear sky chart from 2005-11-05 to 2017-12-02.

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
24%
14801
9%
47946
5%
14769
29%
14769
12%
37381

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
6%
2506
3%
716
19%
716
6%
2139
January16th to endNight
20%
768
7%
2688
4%
768
25%
768
7%
2190
February1st to 15thNight
21%
704
9%
2353
4%
701
28%
701
9%
1874
February16th to endNight
18%
631
10%
1931
5%
631
25%
631
11%
1558
March1st to 15thNight
24%
720
11%
2160
8%
720
28%
720
13%
1675
March16th to endNight
27%
768
16%
1995
7%
768
32%
768
18%
1511
April1st to 15thNight
23%
718
11%
1796
4%
718
27%
718
15%
1424
April16th to endNight
27%
567
15%
1647
7%
567
33%
567
20%
1169
May1st to 15thNight
30%
360
11%
1440
10%
360
36%
360
12%
1029
May16th to endNight
26%
375
9%
1497
8%
374
35%
374
14%
1047
June1st to 15thNight
26%
360
5%
1415
3%
360
31%
360
12%
1025
June16th to endNight
40%
360
4%
1407
3%
360
42%
360
16%
956
July1st to 15thNight
35%
340
6%
1360
7%
340
37%
340
16%
911
July16th to endNight
40%
376
8%
1418
10%
354
44%
354
16%
973
August1st to 15thNight
43%
359
10%
1430
10%
357
47%
357
13%
1016
August16th to endNight
38%
681
11%
1827
6%
681
41%
681
21%
1327
September1st to 15thNight
36%
720
9%
1800
4%
720
38%
720
23%
1310
September16th to endNight
30%
717
13%
1959
7%
717
34%
717
20%
1422
October1st to 15thNight
22%
720
10%
2142
5%
720
28%
720
15%
1623
October16th to endNight
15%
768
7%
2478
4%
768
19%
768
7%
2093
November1st to 15thNight
17%
760
9%
2534
5%
760
22%
760
7%
2106
November16th to endNight
15%
780
6%
2730
5%
780
18%
780
6%
2304
December1st to 15thNight
14%
754
3%
2700
1%
754
17%
754
5%
2329
December16th to endNight
15%
775
7%
2733
4%
775
18%
775
5%
2370

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%12%48%6%34445%23%
48452
Night
18%12%5%8%7%35%5%5%6%22%
48115
TransparencyDay
61%6%10%14%6%
48139
Night
61%6%10%14%6%
47946
SeeingDay
25%13%31%18%7%2
5696
Night
24%12%31%22%7%
14801

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%16%6%13%7%35%5%4411%
1432
16th to endDay
13%15%5%11%8%5%6%6%7%7%12%
1536
February1st to 15thDay
8%13%6%12%10%7%8%7%5%5%13%
1508
16th to endDay
12%18%6%10%9%47%44418%
1542
March1st to 15thDay
16%12%5%10%6%25%5%5%6%23%
1790
16th to endDay
13%14%48%6%245%35%29%
2227
April1st to 15thDay
21%15%5%8%5%2433423%
2152
16th to endDay
21%12%46%43335%5%28%
2325
May1st to 15thDay
22%10%35%5%335%46%28%
2511
16th to endDay
22%9%37%5%34435%28%
2618
June1st to 15thDay
23%9%37%5%2435%6%27%
2520
16th to endDay
22%8%35%6%45%6%5%7%24%
2520
July1st to 15thDay
22%8%37%6%35%45%8%24%
2520
16th to endDay
16%8%47%7%345%6%7%27%
2654
August1st to 15thDay
22%10%38%7%35%45%6%21%
2520
16th to endDay
18%8%38%6%35%5%5%7%24%
2362
September1st to 15thDay
22%7%46%6%23446%31%
2160
16th to endDay
22%10%35%5%34436%30%
2001
October1st to 15thDay
26%13%38%5%33335%23%
1815
16th to endDay
28%18%5%8%6%1333415%
1746
November1st to 15thDay
19%17%7%8%7%24335%19%
1652
16th to endDay
23%18%7%11%6%3343414%
1560
December1st to 15thDay
20%20%6%9%8%35%43311%
1293
16th to endDay
20%15%6%10%7%45%45%414%
1488
January1st to 15thNight
18%16%6%11%9%36%6%5%6%9%
2506
16th to endNight
11%14%6%11%9%5%9%6%7%6%11%
2688
February1st to 15thNight
9%12%7%11%10%7%7%7%7%6%14%
2351
16th to endNight
11%15%5%11%9%47%446%19%
1931
March1st to 15thNight
15%12%6%8%6%46%5%5%6%22%
2147
16th to endNight
13%11%49%6%345%45%30%
1995
April1st to 15thNight
21%13%47%5%4433426%
1796
16th to endNight
19%8%46%424436%34%
1647
May1st to 15thNight
20%9%36%6%36%335%30%
1440
16th to endNight
21%9%35%5%33447%31%
1495
June1st to 15thNight
20%8%36%6%35%5%5%6%27%
1415
16th to endNight
15%6%36%5%35%6%6%9%32%
1407
July1st to 15thNight
18%7%25%5%36%5%7%6%31%
1440
16th to endNight
14%6%26%5%35%47%7%35%
1514
August1st to 15thNight
17%6%36%5%436%6%8%30%
1440
16th to endNight
17%6%35%5%345%6%7%33%
1827
September1st to 15thNight
20%8%35%424437%36%
1800
16th to endNight
21%7%36%5%23346%35%
1959
October1st to 15thNight
20%11%47%6%34437%27%
2142
16th to endNight
26%17%47%7%34345%16%
2478
November1st to 15thNight
19%13%6%10%7%35%445%17%
2534
16th to endNight
23%16%6%9%7%34445%13%
2730
December1st to 15thNight
20%19%7%11%7%45%43411%
2700
16th to endNight
17%17%7%12%9%45%5%3411%
2733

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
74%46%9%3
1433
16th to endDay
66%5%7%13%6%
1536
February1st to 15thDay
68%6%7%10%8%
1510
16th to endDay
68%47%10%8%
1542
March1st to 15thDay
61%37%15%10%1
1800
16th to endDay
56%47%17%11%2
2227
April1st to 15thDay
63%37%13%9%1
2152
16th to endDay
55%6%8%14%13%1
2325
May1st to 15thDay
55%6%9%17%10%1
2511
16th to endDay
58%6%7%17%8%1
2622
June1st to 15thDay
57%5%9%17%9%
2520
16th to endDay
57%8%12%13%7%
2520
July1st to 15thDay
55%7%14%17%4
2371
16th to endDay
57%7%12%17%5%
2487
August1st to 15thDay
61%9%13%12%2
2506
16th to endDay
55%9%13%16%5%
2362
September1st to 15thDay
53%6%14%17%6%
2160
16th to endDay
55%5%15%17%5%
2001
October1st to 15thDay
63%410%14%41
1815
16th to endDay
73%5%9%8%2
1746
November1st to 15thDay
68%7%10%9%3
1652
16th to endDay
73%5%9%7%3
1560
December1st to 15thDay
76%45%10%1
1293
16th to endDay
72%46%9%5%
1488
January1st to 15thNight
73%5%7%10%2
2506
16th to endNight
68%5%8%11%5%
2688
February1st to 15thNight
65%5%9%13%5%
2353
16th to endNight
66%46%14%7%
1931
March1st to 15thNight
61%5%8%14%10%
2160
16th to endNight
54%5%8%20%9%1
1995
April1st to 15thNight
61%37%15%9%1
1796
16th to endNight
50%49%20%12%2
1647
May1st to 15thNight
56%5%10%14%11%2
1440
16th to endNight
53%5%12%16%10%
1497
June1st to 15thNight
55%7%10%18%7%
1415
16th to endNight
48%7%15%17%10%
1407
July1st to 15thNight
47%7%16%20%7%
1360
16th to endNight
46%10%14%23%5%
1418
August1st to 15thNight
49%11%17%18%2
1430
16th to endNight
47%8%18%22%3
1827
September1st to 15thNight
48%6%17%19%8%
1800
16th to endNight
50%6%16%22%3
1959
October1st to 15thNight
57%6%13%15%6%
2142
16th to endNight
71%6%8%10%2
2478
November1st to 15thNight
67%8%9%9%4
2534
16th to endNight
73%49%9%2
2730
December1st to 15thNight
75%5%8%8%1
2700
16th to endNight
76%5%5%7%4
2733

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
30%11%40%15%3
60
16th to endDay
28%9%39%14%9%
64
February1st to 15thDay
15%16%36%30%1
79
16th to endDay
25%11%40%16%5%
201
March1st to 15thDay
24%18%31%17%7%
270
16th to endDay
19%18%30%20%8%2
288
April1st to 15thDay
27%18%30%15%6%1
270
16th to endDay
27%15%34%13%8%
270
May1st to 15thDay
29%13%29%18%9%
288
16th to endDay
23%16%30%17%9%1
331
June1st to 15thDay
31%10%30%18%8%
315
16th to endDay
21%13%31%25%6%1
315
July1st to 15thDay
23%8%36%24%6%1
305
16th to endDay
20%8%30%23%13%3
326
August1st to 15thDay
25%6%27%24%9%6%
313
16th to endDay
20%8%33%21%8%8%
332
September1st to 15thDay
25%7%30%20%9%6%
315
16th to endDay
21%11%30%21%10%3
314
October1st to 15thDay
27%16%30%15%8%1
315
16th to endDay
34%16%27%16%4
292
November1st to 15thDay
29%20%33%10%5%
216
16th to endDay
41%23%23%6%32
90
December1st to 15thDay
30%7%41%20%
63
16th to endDay
35%25%29%7%1
64
January1st to 15thNight
25%15%34%18%5%
720
16th to endNight
18%15%34%23%7%
768
February1st to 15thNight
15%12%39%23%8%
704
16th to endNight
21%12%38%19%6%1
631
March1st to 15thNight
24%16%31%22%5%
720
16th to endNight
17%16%34%22%8%1
768
April1st to 15thNight
28%13%28%23%5%
718
16th to endNight
23%13%31%22%8%
567
May1st to 15thNight
24%11%28%27%8%
360
16th to endNight
23%11%32%25%6%
375
June1st to 15thNight
23%8%31%27%8%
360
16th to endNight
16%6%31%32%12%
360
July1st to 15thNight
22%7%30%27%12%
340
16th to endNight
16%6%31%33%10%
376
August1st to 15thNight
18%425%33%15%1
359
16th to endNight
21%6%28%28%13%1
681
September1st to 15thNight
25%7%25%26%12%2
720
16th to endNight
24%8%31%24%8%1
717
October1st to 15thNight
27%10%35%21%5%
720
16th to endNight
36%11%30%16%5%
768
November1st to 15thNight
27%16%31%17%6%1
760
16th to endNight
34%15%26%18%5%
780
December1st to 15thNight
30%14%31%16%5%
754
16th to endNight
26%17%31%18%41
775
Page generated at 2017-12-03 11:16:47. Version ac04

Copyright 2017 A. Danko


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