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 2017-09-22.

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
21%
15787
17%
46577
5%
15742
33%
15742
20%
27916

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
7%
900
15%
2506
1%
895
20%
895
13%
1561
January16th to endNight
9%
783
17%
2511
3%
783
26%
783
13%
1417
February1st to 15thNight
10%
699
12%
2288
2%
697
23%
697
12%
1398
February16th to endNight
8%
632
11%
2046
0%
632
22%
632
11%
1290
March1st to 15thNight
13%
720
14%
1980
2%
720
24%
720
16%
1217
March16th to endNight
14%
768
11%
2112
2%
768
21%
768
16%
1367
April1st to 15thNight
17%
556
9%
1815
2%
556
24%
556
15%
1163
April16th to endNight
21%
540
11%
1623
5%
540
27%
540
17%
1088
May1st to 15thNight
30%
539
13%
1539
7%
539
36%
539
22%
990
May16th to endNight
28%
563
8%
1498
3%
561
32%
561
19%
1073
June1st to 15thNight
31%
486
10%
1386
4%
486
37%
486
21%
905
June16th to endNight
46%
360
21%
1260
14%
360
56%
360
38%
595
July1st to 15thNight
55%
373
17%
1223
12%
373
63%
373
40%
612
July16th to endNight
49%
564
24%
1482
14%
531
58%
531
50%
739
August1st to 15thNight
48%
539
22%
1611
13%
536
57%
536
38%
881
August16th to endNight
48%
573
30%
1759
19%
573
58%
573
40%
908
September1st to 15thNight
41%
546
25%
1806
14%
546
56%
546
33%
955
September16th to endNight
37%
683
24%
1904
11%
683
48%
683
35%
1078
October1st to 15thNight
23%
660
20%
1980
8%
660
34%
660
21%
1234
October16th to endNight
17%
704
24%
2112
6%
704
34%
704
21%
1201
November1st to 15thNight
7%
839
18%
2408
2%
839
23%
839
17%
1444
November16th to endNight
6%
900
17%
2520
1%
900
21%
900
15%
1549
December1st to 15thNight
10%
900
12%
2520
2%
900
19%
900
11%
1594
December16th to endNight
11%
960
18%
2688
1%
960
26%
960
13%
1657

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%6%35%6%6%8%36%
48281
Night
35%35%5%35%6%7%9%43%
46746
Cloud CoverDay
7%8%46%6%36%5%7%8%35%
48282
Night
35%25%5%36%6%8%9%42%
46748
TransparencyDay
40%6%17%20%11%3
47954
Night
31%8%22%23%11%2
46577
SeeingDay
19%25%33%16%4
6023
Night
16%27%30%18%6%
15793

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%5%5%6%10%13%38%
1397
16th to endDay
437%8%47%6%8%9%40%
1722
February1st to 15thDay
7%5%10%9%5%7%6%7%9%30%
1575
16th to endDay
7%5%10%11%5%7%6%8%9%26%
1428
March1st to 15thDay
7%5%9%8%47%7%8%8%32%
1980
16th to endDay
312%6%11%9%5%6%6%6%7%23%
2111
April1st to 15thDay
415%6%10%9%35%6%5%9%23%
2132
16th to endDay
6%17%6%11%6%35%5%5%7%23%
2334
May1st to 15thDay
9%14%5%8%7%3446%7%28%
2411
16th to endDay
14%14%5%8%6%35%5%5%6%21%
2616
June1st to 15thDay
12%10%48%6%35%5%5%7%29%
2569
16th to endDay
4425%435%6%6%8%48%
2700
July1st to 15thDay
5%3245%46%7%6%9%44%
2661
16th to endDay
44245%35%45%7%52%
2582
August1st to 15thDay
7%425%6%46%6%6%7%42%
2340
16th to endDay
5%425%5%34447%51%
2442
September1st to 15thDay
10%6%1432344453%
2151
16th to endDay
7%6%2343446%6%48%
1868
October1st to 15thDay
8%12%46%42445%8%36%
1650
16th to endDay
47%46%5%345%7%9%41%
1760
November1st to 15thDay
27%45%6%46%7%6%8%38%
1439
16th to endDay
15%38%9%45%6%7%8%39%
1440
December1st to 15thDay
447%9%48%10%9%10%30%
1440
16th to endDay
13310%9%6%7%8%8%7%33%
1533
January1st to 15thNight
325%6%47%7%9%12%41%
2506
16th to endNight
335%5%35%6%9%13%44%
2511
February1st to 15thNight
5%36%8%47%7%9%10%37%
2277
16th to endNight
5%49%9%5%8%8%8%9%31%
2046
March1st to 15thNight
5%36%6%35%7%8%11%41%
1980
16th to endNight
26%47%5%47%7%9%10%35%
2109
April1st to 15thNight
37%47%6%36%6%7%8%37%
1815
16th to endNight
39%37%7%36%6%6%9%34%
1623
May1st to 15thNight
5%10%37%6%2345%7%43%
1538
16th to endNight
10%9%37%7%45%6%7%7%30%
1498
June1st to 15thNight
9%6%25%5%35%6%6%8%40%
1386
16th to endNight
3213325%35%8%59%
1260
July1st to 15thNight
3112325%5%9%9%55%
1296
16th to endNight
321231435%8%63%
1584
August1st to 15thNight
33134346%7%9%52%
1620
16th to endNight
3313323446%60%
1759
September1st to 15thNight
7%423323445%58%
1806
16th to endNight
5%6%2332346%7%54%
1904
October1st to 15thNight
7%7%45%4245%5%7%43%
1980
16th to endNight
24245%35%5%8%9%47%
2112
November1st to 15thNight
15%25%6%35%6%9%12%41%
2408
16th to endNight
5%35%5%36%6%9%11%42%
2520
December1st to 15thNight
336%7%47%8%11%11%34%
2520
16th to endNight
337%7%48%7%9%10%36%
2688

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%47%7%12%12%36%
1397
16th to endDay
5%46%7%46%6%9%10%38%
1722
February1st to 15thDay
6%5%8%8%5%8%7%11%8%29%
1575
16th to endDay
8%5%12%10%6%8%5%8%7%26%
1428
March1st to 15thDay
7%48%8%5%7%7%8%9%30%
1980
16th to endDay
315%7%10%8%46%6%6%7%22%
2112
April1st to 15thDay
6%16%7%9%6%45%5%5%8%23%
2132
16th to endDay
8%20%6%9%6%35%45%6%22%
2334
May1st to 15thDay
11%15%5%7%6%3445%7%27%
2411
16th to endDay
19%14%5%7%6%36%46%6%20%
2616
June1st to 15thDay
16%9%37%6%35%5%6%7%28%
2569
16th to endDay
5%424436%5%7%9%47%
2700
July1st to 15thDay
7%325%6%35%6%8%8%42%
2661
16th to endDay
6%315%5%35%5%5%7%50%
2582
August1st to 15thDay
10%4246%45%5%6%8%40%
2340
16th to endDay
8%5%25%5%34447%49%
2442
September1st to 15thDay
12%6%24323445%50%
2151
16th to endDay
8%7%234245%6%7%46%
1868
October1st to 15thDay
11%14%36%4245%47%35%
1650
16th to endDay
48%46%425%5%7%8%41%
1760
November1st to 15thDay
36%45%7%47%6%7%8%38%
1439
16th to endDay
15%46%6%5%7%6%8%10%39%
1440
December1st to 15thDay
1427%8%48%8%12%9%31%
1440
16th to endDay
1339%8%49%8%10%8%34%
1533
January1st to 15thNight
225%6%47%8%12%9%39%
2506
16th to endNight
1345%435%6%8%11%44%
2511
February1st to 15thNight
5%37%6%38%8%10%9%35%
2277
16th to endNight
5%49%7%47%7%12%8%31%
2046
March1st to 15thNight
16%25%5%27%8%8%11%40%
1980
16th to endNight
27%37%5%48%6%8%10%34%
2112
April1st to 15thNight
410%47%5%36%5%8%7%37%
1815
16th to endNight
412%38%7%35%5%5%9%33%
1623
May1st to 15thNight
6%12%35%5%235%5%6%42%
1538
16th to endNight
14%9%37%5%35%6%7%8%28%
1497
June1st to 15thNight
11%5%34436%5%6%8%38%
1386
16th to endNight
42134345%5%8%57%
1260
July1st to 15thNight
3113436%6%8%8%54%
1296
16th to endNight
421331435%7%62%
1584
August1st to 15thNight
5%3145%346%8%8%49%
1620
16th to endNight
5%413324347%58%
1759
September1st to 15thNight
9%5%13323336%55%
1806
16th to endNight
7%5%2332345%7%51%
1904
October1st to 15thNight
8%9%35%425%5%5%6%41%
1980
16th to endNight
35%145%45%5%8%8%47%
2112
November1st to 15thNight
16%36%5%36%5%9%10%42%
2408
16th to endNight
15%26%6%36%7%9%11%40%
2520
December1st to 15thNight
337%6%47%8%13%9%36%
2520
16th to endNight
427%6%5%7%6%9%10%39%
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
26%12%29%20%7%2
1397
16th to endDay
31%10%26%20%9%2
1722
February1st to 15thDay
39%10%24%19%5%
1575
16th to endDay
47%8%18%16%6%1
1428
March1st to 15thDay
37%8%27%19%5%
1980
16th to endDay
54%6%20%15%2
2112
April1st to 15thDay
53%7%17%17%3
2132
16th to endDay
58%417%15%3
2334
May1st to 15thDay
52%5%15%22%4
2411
16th to endDay
60%7%15%13%2
2620
June1st to 15thDay
50%7%14%19%8%
2569
16th to endDay
28%6%14%28%16%6%
2700
July1st to 15thDay
33%6%12%22%17%7%
2505
16th to endDay
29%48%18%24%14%
2421
August1st to 15thDay
37%5%10%20%17%9%
2325
16th to endDay
33%38%22%21%10%
2442
September1st to 15thDay
33%38%22%26%4
2151
16th to endDay
31%414%28%16%4
1868
October1st to 15thDay
44%417%23%8%
1650
16th to endDay
33%5%22%24%12%1
1760
November1st to 15thDay
36%8%18%21%11%2
1439
16th to endDay
32%8%26%22%8%
1440
December1st to 15thDay
34%14%26%16%7%
1440
16th to endDay
35%8%25%23%6%1
1533
January1st to 15thNight
26%14%27%20%7%2
2506
16th to endNight
26%10%28%22%10%2
2511
February1st to 15thNight
32%10%25%22%8%
2288
16th to endNight
36%9%24%19%8%1
2046
March1st to 15thNight
27%11%28%23%8%1
1980
16th to endNight
37%7%28%21%4
2112
April1st to 15thNight
39%8%25%19%6%
1815
16th to endNight
43%6%26%18%4
1623
May1st to 15thNight
40%5%19%28%6%
1539
16th to endNight
47%7%23%16%5%
1498
June1st to 15thNight
37%8%21%22%8%
1386
16th to endNight
21%416%33%18%6%
1260
July1st to 15thNight
20%6%16%29%19%6%
1223
16th to endNight
18%410%20%31%14%
1482
August1st to 15thNight
26%6%14%25%17%10%
1611
16th to endNight
24%410%28%23%9%
1759
September1st to 15thNight
28%410%25%26%4
1806
16th to endNight
28%416%30%18%2
1904
October1st to 15thNight
38%419%25%9%1
1980
16th to endNight
28%6%20%29%13%1
2112
November1st to 15thNight
29%8%23%25%10%2
2408
16th to endNight
28%10%27%20%10%1
2520
December1st to 15thNight
29%13%29%20%6%
2520
16th to endNight
32%8%24%24%8%1
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
9%31%35%20%3
85
16th to endDay
6%50%29%7%6%1
96
February1st to 15thDay
31%38%25%31
90
16th to endDay
27%41%23%42
84
March1st to 15thDay
26%47%20%5%
270
16th to endDay
28%32%32%5%
288
April1st to 15thDay
24%39%31%4
269
16th to endDay
34%24%30%9%
270
May1st to 15thDay
23%18%34%16%41
368
16th to endDay
28%17%28%17%6%
517
June1st to 15thDay
20%22%30%21%5%
495
16th to endDay
10%21%38%21%7%1
495
July1st to 15thDay
10%14%35%26%11%1
475
16th to endDay
7%16%44%22%7%
441
August1st to 15thDay
15%19%41%20%3
315
16th to endDay
14%15%43%20%6%
332
September1st to 15thDay
17%26%38%16%1
315
16th to endDay
20%22%39%14%2
266
October1st to 15thDay
27%42%20%6%3
90
16th to endDay
22%30%31%13%2
96
November1st to 15thDay
15%36%23%16%7%
90
16th to endDay
13%44%38%3
90
December1st to 15thDay
34%31%20%13%1
90
16th to endDay
21%32%25%15%5%
96
January1st to 15thNight
20%40%28%8%2
900
16th to endNight
15%43%28%9%2
783
February1st to 15thNight
17%37%29%11%3
704
16th to endNight
20%34%30%10%3
632
March1st to 15thNight
20%35%27%13%3
720
16th to endNight
17%29%34%16%1
768
April1st to 15thNight
15%25%37%17%3
556
16th to endNight
15%24%32%19%7%
540
May1st to 15thNight
18%20%25%22%10%1
540
16th to endNight
21%12%31%24%9%
563
June1st to 15thNight
17%16%29%29%5%
486
16th to endNight
8%11%29%39%10%
360
July1st to 15thNight
6%7%25%43%16%
373
16th to endNight
7%7%31%40%12%
564
August1st to 15thNight
7%5%33%42%11%
539
16th to endNight
8%8%29%36%16%
573
September1st to 15thNight
13%11%29%31%11%2
546
16th to endNight
15%11%32%25%12%2
683
October1st to 15thNight
17%22%32%18%7%
660
16th to endNight
14%31%34%12%6%
704
November1st to 15thNight
19%38%32%7%1
839
16th to endNight
18%38%34%7%
900
December1st to 15thNight
19%39%27%10%2
900
16th to endNight
17%39%28%11%3
960
Page generated at 2017-09-23 04:43:34. Version ac04

Copyright 2017 A. Danko


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