Long Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Long Lake clear sky chart from 2005-11-05 to 2019-06-19.

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
22%
18177
17%
53608
6%
18132
33%
18132
20%
32250

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
10%
1050
16%
2926
3%
1045
21%
1045
15%
1805
January16th to endNight
9%
913
17%
2929
3%
913
26%
913
13%
1649
February1st to 15thNight
10%
819
12%
2678
3%
817
23%
817
11%
1658
February16th to endNight
9%
736
10%
2384
1%
736
21%
736
10%
1548
March1st to 15thNight
14%
840
16%
2310
4%
840
25%
840
17%
1436
March16th to endNight
16%
896
11%
2464
2%
896
24%
896
17%
1595
April1st to 15thNight
17%
649
9%
2118
1%
649
24%
649
13%
1395
April16th to endNight
22%
624
11%
1876
5%
624
29%
624
17%
1253
May1st to 15thNight
32%
629
13%
1796
7%
629
38%
629
22%
1170
May16th to endNight
32%
659
8%
1754
4%
657
35%
657
19%
1273
June1st to 15thNight
33%
568
12%
1618
4%
568
41%
568
23%
1028
June16th to endNight
45%
398
19%
1393
13%
398
55%
398
36%
689
July1st to 15thNight
55%
406
18%
1331
14%
406
64%
406
41%
655
July16th to endNight
50%
612
24%
1616
14%
579
59%
579
49%
809
August1st to 15thNight
49%
575
23%
1719
14%
572
59%
572
38%
940
August16th to endNight
48%
621
29%
1906
18%
621
58%
621
39%
990
September1st to 15thNight
44%
591
27%
1956
16%
591
59%
591
34%
1020
September16th to endNight
37%
776
24%
2161
11%
776
47%
776
34%
1242
October1st to 15thNight
22%
780
20%
2340
8%
780
34%
780
21%
1474
October16th to endNight
19%
832
25%
2496
6%
832
36%
832
23%
1385
November1st to 15thNight
8%
983
19%
2821
3%
983
24%
983
16%
1695
November16th to endNight
7%
1050
16%
2940
1%
1050
22%
1050
15%
1797
December1st to 15thNight
10%
1050
15%
2940
2%
1050
21%
1050
13%
1818
December16th to endNight
11%
1120
16%
3136
1%
1120
25%
1120
12%
1926

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
5%8%47%7%35%6%6%8%36%
55079
Night
25%25%5%35%6%7%9%43%
53777
Cloud CoverDay
6%9%47%6%36%5%7%8%35%
55080
Night
35%26%5%36%6%8%8%42%
53779
TransparencyDay
41%6%17%20%11%3
54752
Night
31%8%21%23%12%2
53608
SeeingDay
20%26%32%15%4
8344
Night
15%27%30%19%6%
18183

By Month

Percentage Cloud Cover NW (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
335%7%45%6%9%13%40%
1631
16th to endDay
437%8%37%6%8%9%40%
2009
February1st to 15thDay
8%5%10%9%5%7%6%7%9%28%
1845
16th to endDay
8%6%10%11%5%7%6%8%9%25%
1662
March1st to 15thDay
7%5%9%8%47%6%8%8%33%
2310
16th to endDay
312%6%11%9%5%5%6%7%7%23%
2463
April1st to 15thDay
417%6%10%9%35%6%5%9%21%
2488
16th to endDay
7%17%6%11%6%35%5%46%25%
2685
May1st to 15thDay
9%14%48%7%345%6%7%27%
2814
16th to endDay
14%14%6%9%7%35%5%5%6%20%
3064
June1st to 15thDay
11%9%37%6%36%6%6%7%30%
2997
16th to endDay
5%425%435%6%6%8%46%
2975
July1st to 15thDay
5%3245%46%7%6%8%45%
2883
16th to endDay
44245%35%5%6%7%51%
2800
August1st to 15thDay
7%425%5%36%6%6%8%43%
2485
16th to endDay
5%425%5%34446%51%
2647
September1st to 15thDay
10%6%14323445%53%
2330
16th to endDay
7%6%2343446%7%47%
2129
October1st to 15thDay
8%12%46%4245%5%7%38%
1950
16th to endDay
46%46%5%335%6%9%44%
2080
November1st to 15thDay
27%45%6%46%7%6%9%38%
1683
16th to endDay
15%38%8%45%6%7%8%40%
1680
December1st to 15thDay
336%8%47%10%9%10%33%
1680
16th to endDay
13310%9%6%7%7%8%8%33%
1789
January1st to 15thNight
325%5%37%7%9%12%42%
2926
16th to endNight
326%6%35%6%8%12%44%
2929
February1st to 15thNight
5%27%8%47%7%9%10%34%
2667
16th to endNight
5%410%9%5%8%7%7%8%30%
2384
March1st to 15thNight
6%36%6%35%8%8%10%40%
2310
16th to endNight
16%46%5%47%6%9%11%35%
2461
April1st to 15thNight
48%47%6%36%6%7%8%35%
2118
16th to endNight
39%36%7%36%6%6%9%36%
1876
May1st to 15thNight
410%37%6%335%5%7%43%
1795
16th to endNight
10%9%37%7%45%6%7%7%30%
1754
June1st to 15thNight
8%5%24435%6%6%9%42%
1618
16th to endNight
4313335%46%8%56%
1393
July1st to 15thNight
2112325%5%8%9%56%
1404
16th to endNight
321232445%8%62%
1718
August1st to 15thNight
33134346%7%8%53%
1728
16th to endNight
4313423446%60%
1906
September1st to 15thNight
7%423223445%58%
1956
16th to endNight
5%5%2442345%6%54%
2161
October1st to 15thNight
7%7%36%5%25%5%5%7%43%
2340
16th to endNight
24244345%8%9%49%
2496
November1st to 15thNight
15%25%6%35%6%9%11%42%
2821
16th to endNight
15%25%5%36%6%8%11%42%
2940
December1st to 15thNight
336%7%46%7%10%11%37%
2940
16th to endNight
337%7%5%7%7%9%11%35%
3136

Percentage Cloud Cover SW (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
335%5%46%7%12%12%37%
1631
16th to endDay
5%36%7%46%6%9%10%38%
2009
February1st to 15thDay
6%5%9%8%5%8%8%10%8%28%
1845
16th to endDay
8%5%12%10%6%9%6%8%7%24%
1662
March1st to 15thDay
8%49%8%5%7%7%8%8%30%
2310
16th to endDay
315%7%10%8%47%6%7%7%22%
2464
April1st to 15thDay
5%19%7%10%6%45%5%5%7%21%
2488
16th to endDay
9%18%6%9%6%35%446%23%
2685
May1st to 15thDay
11%16%5%7%6%3445%7%26%
2814
16th to endDay
19%15%48%6%36%46%6%19%
3064
June1st to 15thDay
14%9%37%6%35%6%7%7%28%
2997
16th to endDay
7%4245%35%5%6%8%45%
2975
July1st to 15thDay
6%325%5%35%6%8%8%43%
2883
16th to endDay
6%315%5%36%5%5%7%49%
2800
August1st to 15thDay
9%4246%45%5%6%8%41%
2485
16th to endDay
8%5%35%5%34446%48%
2647
September1st to 15thDay
11%6%23323446%50%
2330
16th to endDay
8%8%244345%6%7%44%
2129
October1st to 15thDay
10%15%36%424447%36%
1950
16th to endDay
48%35%425%5%7%8%43%
2080
November1st to 15thDay
37%46%6%46%6%7%8%37%
1683
16th to endDay
15%36%6%46%5%8%10%39%
1680
December1st to 15thDay
426%8%48%8%11%9%34%
1680
16th to endDay
1338%8%410%8%10%9%32%
1789
January1st to 15thNight
216%6%37%8%11%10%40%
2926
16th to endNight
336%5%35%6%8%11%44%
2929
February1st to 15thNight
5%37%7%48%9%9%9%33%
2667
16th to endNight
5%411%8%5%8%6%11%7%29%
2384
March1st to 15thNight
17%36%5%27%8%7%10%39%
2310
16th to endNight
27%37%6%48%7%9%9%33%
2464
April1st to 15thNight
5%10%48%6%36%5%8%7%34%
2118
16th to endNight
412%37%7%35%5%5%8%34%
1876
May1st to 15thNight
7%12%36%5%235%5%6%40%
1795
16th to endNight
14%10%37%5%35%6%7%8%27%
1753
June1st to 15thNight
10%5%34436%5%6%9%40%
1618
16th to endNight
5%3144345%5%7%54%
1393
July1st to 15thNight
313335%6%7%8%55%
1404
16th to endNight
421231435%7%61%
1718
August1st to 15thNight
5%3145%346%8%8%49%
1728
16th to endNight
5%413324346%58%
1906
September1st to 15thNight
8%5%13323336%56%
1956
16th to endNight
8%5%2442345%7%51%
2161
October1st to 15thNight
7%9%36%5%25%5%5%6%40%
2340
16th to endNight
34145%45%5%8%7%49%
2496
November1st to 15thNight
16%26%5%35%6%9%10%41%
2821
16th to endNight
15%26%5%37%7%8%11%39%
2940
December1st to 15thNight
327%6%47%8%12%9%38%
2940
16th to endNight
427%6%5%7%6%9%10%37%
3136

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
26%11%29%20%9%2
1631
16th to endDay
31%10%25%19%9%2
2009
February1st to 15thDay
40%10%23%18%6%
1845
16th to endDay
48%7%17%15%7%2
1662
March1st to 15thDay
39%8%24%19%6%1
2310
16th to endDay
54%6%20%14%3
2464
April1st to 15thDay
56%6%16%16%3
2488
16th to endDay
57%417%15%4
2685
May1st to 15thDay
54%5%14%21%4
2814
16th to endDay
62%7%14%12%2
3068
June1st to 15thDay
48%7%14%19%8%
2997
16th to endDay
30%6%13%27%15%6%
2975
July1st to 15thDay
32%6%11%22%19%7%
2727
16th to endDay
29%49%19%24%13%
2639
August1st to 15thDay
36%5%10%21%17%8%
2470
16th to endDay
33%49%22%20%9%
2647
September1st to 15thDay
32%39%23%27%4
2330
16th to endDay
33%414%27%15%4
2129
October1st to 15thDay
44%416%23%10%1
1950
16th to endDay
31%6%22%25%13%1
2080
November1st to 15thDay
37%8%19%20%10%2
1683
16th to endDay
32%8%26%23%9%
1680
December1st to 15thDay
32%13%25%17%10%1
1680
16th to endDay
34%8%24%22%8%1
1789
January1st to 15thNight
26%13%26%21%9%3
2926
16th to endNight
26%10%28%21%11%2
2929
February1st to 15thNight
34%10%25%21%8%
2678
16th to endNight
40%8%21%19%9%1
2384
March1st to 15thNight
30%9%25%23%9%1
2310
16th to endNight
37%7%27%21%5%
2464
April1st to 15thNight
42%8%24%18%5%
2118
16th to endNight
42%7%24%20%4
1876
May1st to 15thNight
41%5%20%26%5%
1796
16th to endNight
49%7%22%16%4
1754
June1st to 15thNight
34%9%22%23%9%1
1618
16th to endNight
24%415%32%17%5%
1393
July1st to 15thNight
20%6%15%28%22%6%
1331
16th to endNight
18%411%21%30%13%
1616
August1st to 15thNight
26%6%13%26%17%9%
1719
16th to endNight
24%410%27%23%9%
1906
September1st to 15thNight
27%39%26%27%4
1956
16th to endNight
28%415%30%17%3
2161
October1st to 15thNight
39%418%25%10%1
2340
16th to endNight
26%6%20%30%14%1
2496
November1st to 15thNight
29%9%22%25%11%2
2821
16th to endNight
28%10%26%21%10%1
2940
December1st to 15thNight
28%12%27%20%10%
2940
16th to endNight
32%7%24%24%9%1
3136

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
10%36%30%18%4
169
16th to endDay
15%52%23%5%3
192
February1st to 15thDay
29%42%22%41
180
16th to endDay
25%38%23%9%3
162
March1st to 15thDay
22%43%27%5%1
390
16th to endDay
27%32%30%8%1
416
April1st to 15thDay
30%39%26%3
389
16th to endDay
33%25%28%10%1
378
May1st to 15thDay
23%18%34%17%41
501
16th to endDay
30%15%27%18%6%1
677
June1st to 15thDay
18%22%30%21%6%
645
16th to endDay
12%19%38%20%7%
587
July1st to 15thDay
9%15%35%27%10%1
550
16th to endDay
7%16%45%22%6%
515
August1st to 15thDay
14%18%42%21%3
359
16th to endDay
14%17%43%18%5%
396
September1st to 15thDay
15%25%40%16%1
375
16th to endDay
20%24%38%13%2
359
October1st to 15thDay
27%35%28%7%2
180
16th to endDay
19%34%26%15%31
192
November1st to 15thDay
19%37%27%12%3
180
16th to endDay
17%43%32%41
180
December1st to 15thDay
22%41%23%10%1
180
16th to endDay
19%40%25%13%2
192
January1st to 15thNight
18%39%28%10%2
1050
16th to endNight
16%43%29%8%2
913
February1st to 15thNight
19%37%27%12%3
824
16th to endNight
19%34%30%11%4
736
March1st to 15thNight
18%33%30%13%3
840
16th to endNight
15%28%34%17%3
896
April1st to 15thNight
17%26%35%17%3
649
16th to endNight
14%25%32%20%7%
624
May1st to 15thNight
18%18%26%24%10%1
630
16th to endNight
21%11%29%26%10%
659
June1st to 15thNight
16%16%29%29%7%1
568
16th to endNight
10%10%29%38%10%
398
July1st to 15thNight
6%7%25%43%16%
406
16th to endNight
7%7%31%41%11%
612
August1st to 15thNight
7%433%42%11%
575
16th to endNight
9%8%29%35%15%
621
September1st to 15thNight
12%11%29%31%12%2
591
16th to endNight
14%12%32%26%11%2
776
October1st to 15thNight
16%22%33%19%6%
780
16th to endNight
14%30%34%12%7%
832
November1st to 15thNight
18%39%32%8%1
983
16th to endNight
19%39%33%7%1
1050
December1st to 15thNight
17%39%29%10%2
1050
16th to endNight
17%40%27%11%3
1120
Page generated at 2019-06-20 06:02:30. Version ac04

Copyright 2019 A. Danko


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