Canadian Lakes
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canadian Lakes clear sky chart from 2005-11-06 to 2024-01-12.

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
33%
24655
14%
74684
9%
24599
39%
24599
19%
53037

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 10thNight
18%
950
8%
2648
3%
946
22%
946
11%
2160
January11th to 20thNight
16%
908
6%
2541
2%
908
20%
908
9%
2132
January21st to endNight
20%
990
7%
2772
3%
990
23%
990
11%
2254
February1st to 10thNight
17%
747
8%
2341
3%
747
21%
747
10%
1882
February11th to 20thNight
19%
700
13%
2098
5%
699
26%
699
13%
1619
February21st to endNight
16%
592
12%
1776
3%
592
24%
592
12%
1364
March1st to 10thNight
27%
720
16%
2160
9%
720
33%
720
19%
1505
March11th to 20thNight
29%
720
22%
2026
10%
720
39%
720
24%
1357
March21st to endNight
26%
748
15%
2134
8%
748
33%
748
19%
1529
April1st to 10thNight
29%
540
14%
1800
8%
540
37%
540
18%
1219
April11th to 20thNight
30%
533
20%
1697
11%
533
40%
533
21%
1124
April21st to endNight
30%
540
17%
1620
7%
540
39%
540
22%
1082
May1st to 10thNight
34%
540
15%
1620
7%
540
41%
540
22%
1130
May11th to 20thNight
36%
531
19%
1584
10%
531
46%
531
25%
1050
May21st to endNight
44%
583
16%
1552
9%
582
50%
582
31%
1012
June1st to 10thNight
44%
540
15%
1440
9%
540
49%
540
33%
909
June11th to 20thNight
47%
540
17%
1440
12%
540
51%
540
33%
917
June21st to endNight
52%
540
18%
1440
11%
540
58%
540
35%
909
July1st to 10thNight
65%
525
18%
1400
13%
525
67%
525
42%
818
July11th to 20thNight
60%
522
20%
1392
15%
522
64%
522
42%
809
July21st to endNight
60%
591
20%
1487
13%
558
64%
558
40%
894
August1st to 10thNight
62%
537
19%
1571
15%
534
65%
534
37%
924
August11th to 20thNight
62%
534
24%
1598
18%
534
67%
534
36%
910
August21st to endNight
57%
594
23%
1904
19%
594
62%
594
33%
1093
September1st to 10thNight
56%
560
22%
1820
18%
560
62%
560
31%
1067
September11th to 20thNight
56%
720
27%
1980
21%
720
61%
720
38%
1170
September21st to endNight
47%
720
20%
1980
15%
720
50%
720
28%
1292
October1st to 10thNight
45%
720
22%
1980
16%
720
50%
720
30%
1270
October11th to 20thNight
29%
720
14%
2213
8%
720
37%
720
18%
1556
October21st to endNight
23%
792
13%
2574
8%
792
31%
792
16%
1871
November1st to 10thNight
30%
740
20%
2406
13%
740
39%
740
21%
1578
November11th to 20thNight
21%
760
12%
2470
7%
760
28%
760
14%
1816
November21st to endNight
23%
760
10%
2470
6%
760
30%
760
13%
1855
December1st to 10thNight
19%
909
6%
2619
2%
909
22%
909
9%
2181
December11th to 20thNight
15%
950
6%
3269
2%
949
20%
949
9%
2660
December21st to endNight
11%
1039
4%
4862
1%
1026
16%
1026
4%
4119

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
14%9%47%7%45%5%5%7%33%
74832
Night
15%10%47%6%35%5%5%7%33%
74899
TransparencyDay
49%7%12%20%11%1
74533
Night
50%6%12%20%11%1
74719
SeeingDay
18%13%29%23%12%4
14673
Night
19%10%30%29%11%1
24665

By Month

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 10thDay
14%15%7%12%10%6%6%6%46%15%
1517
11th to 20thDay
15%16%8%14%9%7%6%46%6%10%
1448
21st to endDay
14%18%11%12%10%45%45%313%
1584
February1st to 10thDay
12%14%7%11%11%5%8%5%5%6%16%
1614
11th to 20thDay
12%14%6%12%12%46%45%6%20%
1748
21st to endDay
13%15%8%11%7%5%5%45%7%21%
1480
March1st to 10thDay
14%10%49%7%5%5%5%5%7%29%
1800
11th to 20thDay
12%10%47%7%46%5%46%34%
1934
21st to endDay
17%11%47%6%45%5%5%6%31%
2239
April1st to 10thDay
19%12%46%6%445%5%7%29%
2160
11th to 20thDay
18%10%36%6%35%45%6%35%
2212
21st to endDay
15%9%47%6%45%45%7%33%
2340
May1st to 10thDay
16%8%36%6%345%5%7%37%
2340
11th to 20thDay
17%7%36%6%3446%6%39%
2307
21st to endDay
11%6%35%5%36%5%6%8%42%
2725
June1st to 10thDay
12%6%35%5%346%5%9%43%
2520
11th to 20thDay
12%6%26%5%35%5%5%8%43%
2520
21st to endDay
11%6%25%5%46%6%6%8%41%
2520
July1st to 10thDay
6%4245%35%6%6%9%50%
2520
11th to 20thDay
7%5%25%6%35%6%6%9%46%
2520
21st to endDay
8%425%6%45%5%7%9%45%
2743
August1st to 10thDay
10%5%25%6%36%7%6%9%40%
2355
11th to 20thDay
10%5%35%6%35%6%6%8%44%
2303
21st to endDay
10%6%25%5%345%6%8%44%
2448
September1st to 10thDay
11%5%36%6%36%5%6%7%41%
2121
11th to 20thDay
12%425%435%46%8%45%
1980
21st to endDay
13%6%36%6%35%5%6%7%40%
1980
October1st to 10thDay
18%8%36%6%3345%5%40%
1980
11th to 20thDay
20%10%5%8%6%5%5%5%47%25%
1741
21st to endDay
21%11%48%8%5%6%45%7%23%
1782
November1st to 10thDay
13%10%47%6%35%46%7%36%
1672
11th to 20thDay
13%16%7%10%7%4445%6%23%
1710
21st to endDay
21%15%6%9%6%3445%6%22%
1710
December1st to 10thDay
14%16%10%12%7%46%445%17%
1558
11th to 20thDay
14%16%7%11%9%45%5%5%6%17%
1918
21st to endDay
23%21%7%10%8%45%44410%
2783
January1st to 10thNight
16%14%7%11%8%445%5%5%19%
2648
11th to 20thNight
15%17%9%11%8%5%5%5%5%5%16%
2541
21st to endNight
12%14%10%13%8%45%6%6%7%16%
2772
February1st to 10thNight
13%14%7%11%11%5%6%5%5%5%19%
2341
11th to 20thNight
13%12%5%11%9%46%5%5%6%25%
2098
21st to endNight
16%14%6%10%7%345%46%25%
1776
March1st to 10thNight
14%9%5%7%6%35%5%6%7%34%
2160
11th to 20thNight
13%8%46%6%35%35%6%41%
2026
21st to endNight
19%9%37%6%44446%34%
2134
April1st to 10thNight
16%10%46%6%35%446%36%
1800
11th to 20thNight
19%8%35%5%2445%7%37%
1697
21st to endNight
17%8%36%5%345%5%7%38%
1620
May1st to 10thNight
12%8%37%6%46%5%6%8%35%
1620
11th to 20thNight
16%7%26%5%3445%9%39%
1583
21st to endNight
12%6%35%5%44447%46%
1551
June1st to 10thNight
11%5%35%5%3446%10%44%
1440
11th to 20thNight
11%5%35%6%3346%10%45%
1440
21st to endNight
8%5%25%5%35%5%6%8%48%
1440
July1st to 10thNight
6%3243345%6%9%56%
1440
11th to 20thNight
7%423435%5%6%9%53%
1440
21st to endNight
7%424425%5%6%9%52%
1575
August1st to 10thNight
8%425%5%235%6%10%50%
1580
11th to 20thNight
8%424435%46%9%52%
1598
21st to endNight
11%5%25%43445%7%52%
1904
September1st to 10thNight
9%4245%35%5%5%8%50%
1820
11th to 20thNight
11%5%2442345%7%53%
1980
21st to endNight
14%5%35%5%35%45%9%42%
1980
October1st to 10thNight
18%7%23424347%45%
1980
11th to 20thNight
19%9%46%5%345%48%33%
2213
21st to endNight
22%10%47%6%34346%30%
2574
November1st to 10thNight
13%10%36%5%35%46%7%38%
2406
11th to 20thNight
15%13%5%9%6%45%5%7%6%25%
2470
21st to endNight
17%13%6%8%6%36%5%5%6%25%
2470
December1st to 10thNight
15%15%7%11%8%5%6%6%45%18%
2619
11th to 20thNight
15%18%6%11%8%45%5%5%5%17%
3279
21st to endNight
25%21%7%10%6%3444413%
4884

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 10thDay
69%6%11%10%4
1518
11th to 20thDay
75%7%8%7%2
1448
21st to endDay
76%48%9%4
1584
February1st to 10thDay
67%7%10%13%4
1614
11th to 20thDay
64%6%9%12%8%1
1758
21st to endDay
64%6%10%13%6%
1480
March1st to 10thDay
55%6%12%19%8%1
1800
11th to 20thDay
51%6%12%16%13%2
1934
21st to endDay
54%6%11%19%9%1
2239
April1st to 10thDay
55%5%11%18%10%
2160
11th to 20thDay
50%6%11%18%13%2
2212
21st to endDay
50%6%11%17%13%2
2340
May1st to 10thDay
45%6%11%23%12%1
2340
11th to 20thDay
44%6%13%20%14%2
2311
21st to endDay
40%7%14%25%14%1
2725
June1st to 10thDay
37%7%11%28%15%2
2520
11th to 20thDay
38%7%13%23%19%1
2520
21st to endDay
39%9%12%22%16%2
2520
July1st to 10thDay
29%8%13%28%18%4
2451
11th to 20thDay
33%8%12%27%18%2
2445
21st to endDay
33%9%12%25%18%3
2591
August1st to 10thDay
37%10%12%27%13%2
2340
11th to 20thDay
36%8%14%25%15%2
2303
21st to endDay
35%8%13%25%17%2
2448
September1st to 10thDay
39%8%14%25%12%2
2121
11th to 20thDay
35%7%15%30%12%1
1980
21st to endDay
42%6%14%25%13%
1980
October1st to 10thDay
46%6%9%23%14%1
1980
11th to 20thDay
58%6%12%17%6%
1741
21st to endDay
60%7%14%13%6%1
1782
November1st to 10thDay
48%6%13%21%11%
1672
11th to 20thDay
60%6%13%14%5%
1710
21st to endDay
63%7%12%13%5%
1710
December1st to 10thDay
70%6%9%12%3
1558
11th to 20thDay
66%7%14%11%2
1915
21st to endDay
77%6%8%6%3
2783
January1st to 10thNight
65%6%13%11%5%
2648
11th to 20thNight
68%7%10%8%5%1
2541
21st to endNight
66%6%13%10%5%
2772
February1st to 10thNight
65%6%11%13%5%
2341
11th to 20thNight
60%6%9%16%9%1
2099
21st to endNight
60%6%11%15%8%1
1776
March1st to 10thNight
48%6%13%21%10%1
2160
11th to 20thNight
43%5%12%22%15%3
2026
21st to endNight
52%5%10%21%11%2
2134
April1st to 10thNight
49%410%21%15%1
1800
11th to 20thNight
46%5%10%20%17%3
1697
21st to endNight
44%6%12%21%14%3
1620
May1st to 10thNight
46%7%13%20%12%2
1620
11th to 20thNight
43%5%10%20%19%3
1584
21st to endNight
40%5%11%27%15%2
1552
June1st to 10thNight
36%6%12%27%18%2
1440
11th to 20thNight
35%6%13%23%22%1
1440
21st to endNight
33%7%14%28%16%2
1440
July1st to 10thNight
24%9%12%31%20%4
1400
11th to 20thNight
26%7%15%31%18%2
1392
21st to endNight
28%7%16%26%19%3
1487
August1st to 10thNight
29%8%16%32%14%1
1571
11th to 20thNight
29%7%13%34%17%1
1598
21st to endNight
32%7%12%27%21%2
1904
September1st to 10thNight
32%8%12%30%18%1
1820
11th to 20thNight
30%6%13%36%15%1
1980
21st to endNight
39%7%14%27%12%1
1980
October1st to 10thNight
39%5%10%28%16%2
1980
11th to 20thNight
50%6%14%21%8%1
2213
21st to endNight
56%5%13%18%9%
2574
November1st to 10thNight
44%6%13%23%13%1
2406
11th to 20thNight
55%7%16%17%6%1
2470
21st to endNight
59%5%16%16%4
2470
December1st to 10thNight
67%7%10%11%4
2619
11th to 20thNight
66%6%14%10%3
3281
21st to endNight
74%6%10%7%3
4884

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 10thDay
23%16%33%21%5%1
270
11th to 20thDay
25%18%35%15%6%
243
21st to endDay
24%16%36%18%5%
264
February1st to 10thDay
20%24%36%18%3
240
11th to 20thDay
22%29%34%13%3
240
21st to endDay
30%27%32%11%1
198
March1st to 10thDay
22%27%35%13%3
240
11th to 20thDay
24%12%32%23%8%2
374
21st to endDay
26%15%30%21%7%2
462
April1st to 10thDay
24%15%33%21%6%1
420
11th to 20thDay
25%18%31%15%7%3
412
21st to endDay
22%15%30%22%10%2
420
May1st to 10thDay
22%17%32%19%8%3
423
11th to 20thDay
18%13%30%23%12%4
453
21st to endDay
14%11%29%27%14%5%
679
June1st to 10thDay
12%10%35%28%11%4
630
11th to 20thDay
16%10%28%29%12%5%
630
21st to endDay
13%8%33%28%14%4
630
July1st to 10thDay
8%6%26%31%20%8%
621
11th to 20thDay
8%10%27%30%19%7%
618
21st to endDay
9%7%30%29%17%8%
684
August1st to 10thDay
11%6%23%26%23%11%
474
11th to 20thDay
11%6%20%27%23%13%
439
21st to endDay
14%7%21%29%20%9%
495
September1st to 10thDay
14%8%23%28%18%9%
450
11th to 20thDay
10%8%18%30%22%11%
450
21st to endDay
19%11%22%25%17%6%
450
October1st to 10thDay
23%11%26%22%16%3
450
11th to 20thDay
28%16%27%24%5%
370
21st to endDay
29%18%32%15%42
297
November1st to 10thDay
22%19%34%19%6%1
270
11th to 20thDay
20%23%37%15%31
270
21st to endDay
31%19%31%14%5%
270
December1st to 10thDay
25%24%29%15%5%1
270
11th to 20thDay
23%20%40%14%4
270
21st to endDay
27%23%33%14%31
297
January1st to 10thNight
22%16%33%21%6%1
950
11th to 20thNight
23%15%33%23%5%1
908
21st to endNight
19%11%33%30%7%
990
February1st to 10thNight
19%15%37%26%3
747
11th to 20thNight
21%14%38%23%4
703
21st to endNight
24%18%35%20%3
592
March1st to 10thNight
19%12%34%25%9%
720
11th to 20thNight
18%13%36%26%7%1
720
21st to endNight
22%11%34%26%7%1
748
April1st to 10thNight
20%13%32%28%6%1
540
11th to 20thNight
24%10%34%26%6%1
533
21st to endNight
20%13%31%28%7%1
540
May1st to 10thNight
17%10%32%32%8%1
540
11th to 20thNight
19%8%32%29%11%1
531
21st to endNight
13%6%29%32%19%1
584
June1st to 10thNight
13%9%28%34%15%1
540
11th to 20thNight
13%6%26%38%16%1
540
21st to endNight
9%426%42%16%1
540
July1st to 10thNight
8%219%42%26%3
525
11th to 20thNight
7%421%43%23%2
522
21st to endNight
8%324%40%22%1
591
August1st to 10thNight
9%219%45%23%2
537
11th to 20thNight
9%319%39%25%5%
534
21st to endNight
12%421%39%22%2
594
September1st to 10thNight
9%423%38%21%5%
560
11th to 20thNight
13%5%21%35%22%4
720
21st to endNight
15%7%24%32%18%4
720
October1st to 10thNight
22%7%22%33%15%1
720
11th to 20thNight
22%13%29%27%8%1
720
21st to endNight
28%11%32%22%6%
792
November1st to 10thNight
18%11%34%28%9%1
740
11th to 20thNight
23%15%35%22%5%1
760
21st to endNight
23%14%32%27%41
760
December1st to 10thNight
22%15%34%25%5%
909
11th to 20thNight
24%14%37%20%41
950
21st to endNight
31%13%34%21%2
1045
Page generated at 2024-01-09 07:14:45. Version ac07

Copyright 2024 Attilla Danko


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