Canadian Lakes
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canadian Lakes clear sky chart from 2005-11-05 to 2017-09-18.

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
35%
16015
14%
46826
9%
15973
40%
15973
20%
33019

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%
900
7%
2506
2%
895
20%
895
10%
2080
January16th to endNight
19%
960
7%
2688
3%
960
23%
960
10%
2203
February1st to 15thNight
19%
719
9%
2233
3%
719
25%
719
11%
1743
February16th to endNight
22%
631
12%
1893
5%
631
29%
631
13%
1454
March1st to 15thNight
29%
720
16%
2130
9%
720
35%
720
19%
1493
March16th to endNight
31%
738
18%
2082
10%
738
38%
738
22%
1429
April1st to 15thNight
29%
539
14%
1797
8%
539
37%
539
18%
1246
April16th to endNight
33%
540
20%
1626
9%
540
42%
540
24%
1060
May1st to 15thNight
36%
540
15%
1620
7%
540
44%
540
23%
1128
May16th to endNight
41%
562
16%
1548
9%
561
49%
561
30%
1005
June1st to 15thNight
45%
540
14%
1440
9%
540
50%
540
31%
928
June16th to endNight
53%
540
15%
1440
8%
540
57%
540
33%
921
July1st to 15thNight
64%
510
17%
1360
13%
510
66%
510
42%
790
July16th to endNight
62%
564
18%
1417
12%
531
65%
531
41%
846
August1st to 15thNight
62%
539
21%
1591
17%
536
66%
536
37%
915
August16th to endNight
61%
573
22%
1800
19%
573
65%
573
34%
1030
September1st to 15thNight
59%
614
24%
1874
20%
614
63%
614
37%
1062
September16th to endNight
56%
669
22%
1848
16%
669
59%
669
33%
1141
October1st to 15thNight
45%
660
21%
1856
15%
660
50%
660
28%
1217
October16th to endNight
23%
704
12%
2280
6%
704
31%
704
16%
1627
November1st to 15thNight
31%
700
18%
2276
14%
700
38%
700
20%
1541
November16th to endNight
24%
720
10%
2340
5%
720
29%
720
11%
1802
December1st to 15thNight
18%
873
5%
2493
2%
873
21%
873
9%
2101
December16th to endNight
14%
960
7%
2688
2%
960
19%
960
9%
2257

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%8%47%6%35%45%7%33%
47978
Night
14%9%46%5%3445%7%34%
46994
Cloud CoverDay
13%8%47%6%35%45%7%32%
47987
Night
14%9%46%5%3445%7%34%
46999
TransparencyDay
49%6%11%20%10%1
47664
Night
48%6%12%20%10%1
46826
SeeingDay
16%8%28%25%14%6%
6003
Night
18%8%30%29%11%1
16019

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
15%15%7%13%10%5%5%45%6%11%
1432
16th to endDay
12%18%10%13%10%5%5%43310%
1536
February1st to 15thDay
12%13%6%11%10%6%7%5%45%15%
1626
16th to endDay
12%13%6%11%10%35%5%5%6%18%
1580
March1st to 15thDay
15%10%36%7%45%45%7%29%
1820
16th to endDay
16%9%47%6%34445%33%
2154
April1st to 15thDay
20%11%35%5%34446%31%
2151
16th to endDay
15%8%36%5%35%5%46%35%
2334
May1st to 15thDay
19%7%25%5%2345%7%35%
2331
16th to endDay
11%5%26%5%335%5%8%41%
2567
June1st to 15thDay
12%6%35%5%25%5%5%8%39%
2520
16th to endDay
11%425%5%45%5%6%7%40%
2520
July1st to 15thDay
6%4245%45%5%6%8%47%
2520
16th to endDay
9%425%5%35%48%9%42%
2655
August1st to 15thDay
9%425%5%36%7%6%9%39%
2358
16th to endDay
11%6%25%5%2445%7%42%
2399
September1st to 15thDay
12%325%5%25%45%8%44%
2073
16th to endDay
11%5%26%6%25%5%6%7%40%
1837
October1st to 15thDay
18%7%36%5%24445%36%
1773
16th to endDay
22%9%37%7%35%446%25%
1590
November1st to 15thDay
14%9%37%6%23446%35%
1582
16th to endDay
20%16%5%7%6%34345%20%
1620
December1st to 15thDay
16%16%8%10%8%46%44416%
1464
16th to endDay
21%17%8%10%7%44345%12%
1536
January1st to 15thNight
19%15%7%10%7%4344418%
2506
16th to endNight
11%12%10%10%7%5%6%5%6%7%14%
2688
February1st to 15thNight
13%13%6%8%9%45%445%22%
2231
16th to endNight
15%12%49%7%45%5%5%6%23%
1893
March1st to 15thNight
15%9%45%5%235%47%34%
2117
16th to endNight
15%7%36%5%3445%7%37%
2082
April1st to 15thNight
19%9%45%5%34346%33%
1797
16th to endNight
17%7%244135%47%40%
1626
May1st to 15thNight
15%6%25%5%36%45%9%34%
1620
16th to endNight
10%6%35%5%24348%44%
1546
June1st to 15thNight
10%5%25%5%3445%9%43%
1440
16th to endNight
9%425%5%245%6%9%45%
1440
July1st to 15thNight
6%22332446%9%54%
1440
16th to endNight
6%2134245%6%9%52%
1513
August1st to 15thNight
6%315%42446%9%51%
1600
16th to endNight
9%5%14323347%52%
1800
September1st to 15thNight
11%32232445%7%53%
1874
16th to endNight
11%4144245%5%6%48%
1848
October1st to 15thNight
17%6%24423348%42%
1856
16th to endNight
20%8%37%6%24347%31%
2280
November1st to 15thNight
13%10%36%425%5%5%6%34%
2276
16th to endNight
19%14%5%8%6%25%5%5%6%21%
2340
December1st to 15thNight
20%14%6%9%7%35%5%45%16%
2493
16th to endNight
21%16%7%9%7%3445%5%15%
2688

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
15%14%7%12%9%6%5%5%46%11%
1432
16th to endDay
12%17%11%12%11%5%5%34310%
1536
February1st to 15thDay
12%13%6%10%11%5%8%5%5%6%15%
1626
16th to endDay
12%13%7%10%9%45%45%6%19%
1580
March1st to 15thDay
15%9%36%6%46%5%47%29%
1830
16th to endDay
16%9%46%6%34445%33%
2153
April1st to 15thDay
20%11%35%5%34346%31%
2151
16th to endDay
15%8%35%5%35%45%7%34%
2334
May1st to 15thDay
19%7%25%42345%7%36%
2331
16th to endDay
10%6%35%5%3445%8%41%
2567
June1st to 15thDay
12%6%35%5%35%5%5%8%39%
2520
16th to endDay
10%5%26%5%46%5%6%8%39%
2520
July1st to 15thDay
6%3245%36%5%5%9%46%
2520
16th to endDay
8%425%5%25%5%7%10%42%
2655
August1st to 15thDay
8%425%6%36%7%6%9%38%
2358
16th to endDay
11%6%25%5%245%5%7%42%
2399
September1st to 15thDay
12%324435%46%8%44%
2073
16th to endDay
11%5%26%5%35%5%6%7%40%
1837
October1st to 15thDay
16%8%36%6%34446%36%
1773
16th to endDay
20%10%47%6%45%446%24%
1590
November1st to 15thDay
14%9%47%6%2335%6%35%
1582
16th to endDay
20%15%6%7%6%3435%5%20%
1620
December1st to 15thDay
15%15%8%11%7%46%43417%
1464
16th to endDay
21%17%8%10%7%34445%12%
1536
January1st to 15thNight
18%14%7%10%7%3444418%
2506
16th to endNight
11%12%10%10%7%5%6%6%6%7%15%
2688
February1st to 15thNight
12%13%6%9%9%45%5%5%5%23%
2224
16th to endNight
14%12%49%7%35%5%46%24%
1893
March1st to 15thNight
15%9%45%5%3445%6%35%
2130
16th to endNight
15%7%35%5%34447%37%
2082
April1st to 15thNight
19%9%46%5%24346%33%
1797
16th to endNight
17%7%34323447%40%
1626
May1st to 15thNight
14%7%26%6%35%46%8%35%
1619
16th to endNight
10%6%35%5%33348%44%
1546
June1st to 15thNight
10%5%25%43446%9%43%
1440
16th to endNight
8%5%25%5%245%6%10%44%
1440
July1st to 15thNight
5%3133245%5%9%54%
1440
16th to endNight
6%31342446%9%52%
1513
August1st to 15thNight
5%3145%2446%9%51%
1600
16th to endNight
10%42432335%6%52%
1800
September1st to 15thNight
10%313323447%53%
1874
16th to endNight
10%5%14425%5%47%48%
1848
October1st to 15thNight
17%6%24424348%41%
1856
16th to endNight
19%8%47%6%24337%31%
2280
November1st to 15thNight
13%10%36%5%2445%6%35%
2276
16th to endNight
18%13%5%7%6%35%45%5%22%
2340
December1st to 15thNight
19%14%6%9%7%45%5%5%5%16%
2493
16th to endNight
20%15%7%9%7%2445%5%16%
2688

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
72%6%10%9%1
1433
16th to endDay
77%47%7%2
1536
February1st to 15thDay
67%6%10%12%3
1628
16th to endDay
63%7%9%13%6%
1580
March1st to 15thDay
53%6%12%18%8%
1830
16th to endDay
51%6%12%20%7%1
2154
April1st to 15thDay
54%49%19%11%
2151
16th to endDay
48%6%11%17%12%3
2334
May1st to 15thDay
47%5%12%22%10%1
2331
16th to endDay
40%6%13%26%13%
2571
June1st to 15thDay
41%6%12%25%14%
2520
16th to endDay
40%9%12%22%15%1
2520
July1st to 15thDay
31%8%12%25%18%2
2371
16th to endDay
35%8%12%24%16%2
2488
August1st to 15thDay
38%9%11%26%12%2
2343
16th to endDay
37%7%12%23%15%2
2399
September1st to 15thDay
36%6%13%29%12%1
2073
16th to endDay
39%7%14%25%12%
1837
October1st to 15thDay
49%5%10%22%11%
1773
16th to endDay
58%6%14%14%4
1590
November1st to 15thDay
48%5%12%21%9%
1582
16th to endDay
64%6%11%11%5%
1620
December1st to 15thDay
70%411%11%2
1464
16th to endDay
73%5%10%8%2
1536
January1st to 15thNight
67%5%11%10%4
2506
16th to endNight
64%7%13%10%3
2688
February1st to 15thNight
61%6%10%15%6%
2233
16th to endNight
59%6%12%13%8%
1893
March1st to 15thNight
47%6%12%19%10%1
2130
16th to endNight
47%412%22%11%1
2082
April1st to 15thNight
51%49%18%14%
1797
16th to endNight
43%411%21%15%3
1626
May1st to 15thNight
45%7%12%20%12%2
1620
16th to endNight
39%5%11%25%16%1
1548
June1st to 15thNight
37%6%12%26%16%1
1440
16th to endNight
34%7%15%24%17%
1440
July1st to 15thNight
25%8%11%31%21%2
1360
16th to endNight
28%6%18%26%17%2
1417
August1st to 15thNight
29%6%13%33%15%1
1591
16th to endNight
31%6%11%28%20%2
1800
September1st to 15thNight
29%6%12%33%18%
1874
16th to endNight
34%6%14%31%12%
1848
October1st to 15thNight
41%410%27%14%1
1856
16th to endNight
53%5%14%18%7%
2280
November1st to 15thNight
46%6%14%19%11%
2276
16th to endNight
61%5%14%14%3
2340
December1st to 15thNight
68%7%11%9%3
2493
16th to endNight
68%6%11%10%3
2688

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%12%38%23%2
90
16th to endDay
30%439%18%6%1
96
February1st to 15thDay
16%15%57%6%3
90
16th to endDay
24%14%30%25%3
81
March1st to 15thDay
30%17%23%21%7%
120
16th to endDay
26%7%27%24%10%3
288
April1st to 15thDay
27%9%31%20%10%1
270
16th to endDay
21%7%32%22%9%5%
270
May1st to 15thDay
22%14%26%23%7%5%
288
16th to endDay
14%12%27%27%12%4
467
June1st to 15thDay
14%7%33%27%12%4
495
16th to endDay
12%8%33%26%13%5%
495
July1st to 15thDay
8%426%30%19%10%
475
16th to endDay
10%5%27%28%19%8%
515
August1st to 15thDay
7%319%26%25%16%
331
16th to endDay
18%416%25%20%15%
332
September1st to 15thDay
9%419%28%26%12%
315
16th to endDay
15%5%16%29%24%8%
262
October1st to 15thDay
19%6%25%32%13%3
255
16th to endDay
28%9%36%24%
102
November1st to 15thDay
12%13%38%20%10%5%
90
16th to endDay
34%12%30%16%6%
90
December1st to 15thDay
18%24%40%12%22
90
16th to endDay
23%27%38%10%
96
January1st to 15thNight
25%15%33%18%6%1
900
16th to endNight
17%11%37%28%5%
960
February1st to 15thNight
18%12%39%25%3
722
16th to endNight
20%12%33%27%5%
631
March1st to 15thNight
19%10%34%26%8%
720
16th to endNight
18%10%34%27%8%1
738
April1st to 15thNight
22%10%33%27%5%
539
16th to endNight
20%8%34%26%8%1
540
May1st to 15thNight
18%6%32%32%9%
540
16th to endNight
13%6%30%31%16%1
563
June1st to 15thNight
12%6%28%36%15%
540
16th to endNight
10%326%40%17%1
540
July1st to 15thNight
7%120%43%25%1
510
16th to endNight
8%123%40%25%1
564
August1st to 15thNight
7%119%42%25%3
539
16th to endNight
10%217%38%26%3
573
September1st to 15thNight
11%422%34%21%6%
614
16th to endNight
11%5%20%35%22%4
669
October1st to 15thNight
19%5%24%35%13%1
660
16th to endNight
24%10%34%21%7%
704
November1st to 15thNight
18%9%34%27%9%
700
16th to endNight
24%14%28%25%6%
720
December1st to 15thNight
25%12%35%23%3
873
16th to endNight
27%11%35%21%3
960
Page generated at 2017-09-19 07:32:33. Version ac04

Copyright 2017 A. Danko


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