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 2017-03-31.

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%
14054
9%
45534
5%
14022
28%
14022
11%
35612

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%
658
12%
1646
4%
658
27%
658
15%
1302
April16th to endNight
28%
520
15%
1510
7%
520
34%
520
21%
1056
May1st to 15thNight
30%
330
12%
1320
11%
330
37%
330
13%
929
May16th to endNight
26%
343
9%
1369
8%
342
35%
342
14%
952
June1st to 15thNight
26%
330
5%
1297
3%
330
30%
330
11%
956
June16th to endNight
41%
330
4%
1289
3%
330
43%
330
17%
874
July1st to 15thNight
33%
310
7%
1240
7%
310
36%
310
16%
838
July16th to endNight
39%
348
6%
1306
8%
326
42%
326
15%
912
August1st to 15thNight
43%
329
11%
1310
10%
327
47%
327
13%
927
August16th to endNight
38%
623
10%
1673
5%
623
41%
623
21%
1217
September1st to 15thNight
36%
660
9%
1650
4%
660
37%
660
22%
1212
September16th to endNight
29%
657
13%
1796
7%
657
33%
657
20%
1304
October1st to 15thNight
20%
660
10%
1963
5%
660
26%
660
14%
1519
October16th to endNight
14%
704
6%
2271
4%
704
18%
704
6%
1940
November1st to 15thNight
18%
700
9%
2334
6%
700
23%
700
7%
1928
November16th to endNight
16%
720
6%
2520
5%
720
19%
720
6%
2123
December1st to 15thNight
14%
746
3%
2674
1%
746
17%
746
5%
2306
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%35%445%22%
45502
Night
18%12%5%8%7%45%5%5%6%22%
45703
TransparencyDay
61%6%10%14%7%
45189
Night
62%6%10%14%5%
45534
SeeingDay
25%13%32%19%8%2
4788
Night
24%12%31%22%7%
14054

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%24435%30%
2222
April1st to 15thDay
20%15%5%8%5%2443424%
1972
16th to endDay
21%11%5%6%42335%5%30%
2131
May1st to 15thDay
21%9%35%5%335%46%30%
2301
16th to endDay
23%9%37%5%34445%29%
2394
June1st to 15thDay
24%9%47%5%2435%6%25%
2310
16th to endDay
21%8%36%6%45%6%5%7%24%
2310
July1st to 15thDay
22%8%38%6%35%45%8%23%
2310
16th to endDay
17%9%47%8%345%6%7%25%
2458
August1st to 15thDay
23%10%38%6%35%45%6%20%
2310
16th to endDay
18%8%49%6%35%6%5%7%24%
2165
September1st to 15thDay
22%7%46%6%23446%30%
1980
16th to endDay
23%9%35%5%34436%30%
1834
October1st to 15thDay
26%13%38%5%33335%22%
1664
16th to endDay
29%18%5%8%7%1333314%
1601
November1st to 15thDay
20%17%8%8%6%2333420%
1522
16th to endDay
23%18%7%10%5%3343415%
1440
December1st to 15thDay
20%20%6%9%8%35%43311%
1282
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%4433427%
1646
16th to endNight
18%8%36%424446%35%
1510
May1st to 15thNight
20%8%36%5%36%345%31%
1320
16th to endNight
21%9%36%5%33447%32%
1367
June1st to 15thNight
21%9%36%7%35%45%6%25%
1297
16th to endNight
16%7%36%5%35%5%5%9%32%
1289
July1st to 15thNight
19%6%35%5%36%5%7%6%30%
1320
16th to endNight
15%6%26%5%35%47%8%33%
1402
August1st to 15thNight
18%5%36%5%446%6%8%30%
1320
16th to endNight
17%6%35%5%345%6%7%32%
1673
September1st to 15thNight
20%8%35%423337%35%
1650
16th to endNight
22%7%36%5%23335%36%
1796
October1st to 15thNight
21%11%47%6%34436%25%
1963
16th to endNight
26%17%5%7%7%3434415%
2271
November1st to 15thNight
19%13%6%10%7%35%445%18%
2334
16th to endNight
23%17%6%9%7%34445%13%
2520
December1st to 15thNight
20%19%6%11%7%45%43411%
2674
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
2222
April1st to 15thDay
62%37%13%10%1
1972
16th to endDay
54%5%8%14%14%1
2131
May1st to 15thDay
53%6%10%18%10%1
2301
16th to endDay
57%5%7%18%8%1
2398
June1st to 15thDay
58%5%9%16%9%
2310
16th to endDay
57%8%12%13%7%
2310
July1st to 15thDay
56%7%14%16%4
2161
16th to endDay
59%8%12%15%4
2291
August1st to 15thDay
62%8%13%12%2
2296
16th to endDay
55%10%13%15%5%
2165
September1st to 15thDay
54%6%14%17%6%
1980
16th to endDay
55%5%15%17%5%
1834
October1st to 15thDay
65%410%13%41
1664
16th to endDay
74%5%8%8%3
1601
November1st to 15thDay
67%6%11%9%4
1522
16th to endDay
71%5%10%7%3
1440
December1st to 15thDay
76%45%10%1
1282
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
1646
16th to endNight
49%49%20%13%2
1510
May1st to 15thNight
55%410%15%11%2
1320
16th to endNight
53%5%11%17%10%
1369
June1st to 15thNight
57%7%10%16%7%
1297
16th to endNight
49%6%15%17%10%
1289
July1st to 15thNight
48%7%15%21%6%
1240
16th to endNight
48%10%14%21%5%
1306
August1st to 15thNight
49%11%17%19%2
1310
16th to endNight
48%8%18%22%3
1673
September1st to 15thNight
49%6%16%19%7%
1650
16th to endNight
51%5%15%22%3
1796
October1st to 15thNight
59%5%12%14%6%1
1963
16th to endNight
72%6%8%10%2
2271
November1st to 15thNight
66%8%9%9%5%
2334
16th to endNight
73%410%9%2
2520
December1st to 15thNight
75%5%8%8%1
2674
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%29%20%8%2
286
April1st to 15thDay
22%19%31%17%6%1
210
16th to endDay
21%15%35%15%10%
210
May1st to 15thDay
23%13%32%19%10%
228
16th to endDay
22%14%31%18%10%1
267
June1st to 15thDay
32%10%31%15%9%
255
16th to endDay
18%11%35%25%7%1
255
July1st to 15thDay
24%8%36%23%5%1
245
16th to endDay
22%7%30%24%13%2
270
August1st to 15thDay
27%5%27%22%9%7%
253
16th to endDay
19%8%36%21%7%7%
268
September1st to 15thDay
25%7%29%20%9%7%
255
16th to endDay
22%13%31%17%11%4
254
October1st to 15thDay
28%16%28%16%8%1
255
16th to endDay
34%14%27%17%5%
243
November1st to 15thDay
30%19%31%11%5%1
176
16th to endDay
36%18%26%10%5%3
60
December1st to 15thDay
31%8%40%20%
60
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
27%14%28%24%5%
658
16th to endNight
22%12%32%22%9%
520
May1st to 15thNight
22%11%29%27%8%
330
16th to endNight
23%12%32%24%6%
343
June1st to 15thNight
25%8%30%27%7%
330
16th to endNight
16%6%30%34%12%
330
July1st to 15thNight
22%7%30%26%11%
310
16th to endNight
16%7%32%33%9%
348
August1st to 15thNight
18%425%33%15%2
329
16th to endNight
21%6%28%29%12%1
623
September1st to 15thNight
25%8%25%26%11%2
660
16th to endNight
25%8%31%23%8%1
657
October1st to 15thNight
28%10%35%20%5%
660
16th to endNight
37%11%29%15%5%
704
November1st to 15thNight
27%16%31%17%6%1
700
16th to endNight
34%15%26%18%5%
720
December1st to 15thNight
30%14%32%16%5%
746
16th to endNight
26%17%31%18%41
775
Page generated at 2017-04-01 08:23:16. Version ac04

Copyright 2017 A. Danko


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