Great East Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Great East Lake 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
27%
22788
19%
74550
8%
22744
40%
22744
20%
48145

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
16%
760
21%
2649
7%
757
35%
757
18%
1646
January11th to 20thNight
18%
728
16%
2546
5%
728
31%
728
12%
1730
January21st to endNight
17%
792
21%
2772
7%
792
36%
792
17%
1724
February1st to 10thNight
13%
720
17%
2350
4%
720
29%
720
14%
1588
February11th to 20thNight
16%
703
21%
2100
4%
700
36%
700
18%
1387
February21st to endNight
20%
592
24%
1776
6%
592
41%
592
19%
1157
March1st to 10thNight
17%
720
22%
2160
6%
720
36%
720
18%
1437
March11th to 20thNight
22%
720
20%
2051
6%
720
36%
720
19%
1365
March21st to endNight
20%
792
22%
2077
6%
792
33%
792
21%
1412
April1st to 10thNight
18%
720
18%
1800
4%
720
27%
720
21%
1288
April11th to 20thNight
22%
661
19%
1725
5%
661
31%
661
22%
1172
April21st to endNight
20%
540
19%
1620
6%
540
30%
540
19%
1098
May1st to 10thNight
24%
540
14%
1620
7%
540
31%
540
17%
1145
May11th to 20thNight
22%
479
17%
1541
8%
479
32%
479
16%
1035
May21st to endNight
34%
389
13%
1551
13%
388
42%
388
17%
983
June1st to 10thNight
29%
360
13%
1440
9%
360
42%
360
16%
937
June11th to 20thNight
34%
360
12%
1440
12%
360
43%
360
19%
906
June21st to endNight
38%
360
11%
1440
11%
360
47%
360
20%
901
July1st to 10thNight
44%
350
13%
1400
15%
350
52%
350
22%
838
July11th to 20thNight
50%
348
14%
1392
16%
348
56%
348
23%
815
July21st to endNight
50%
394
19%
1486
18%
372
59%
372
27%
840
August1st to 10thNight
48%
470
17%
1534
12%
468
53%
468
27%
934
August11th to 20thNight
43%
532
20%
1596
14%
532
47%
532
27%
1011
August21st to endNight
46%
757
21%
1945
10%
757
50%
757
34%
1258
September1st to 10thNight
43%
720
21%
1811
8%
720
50%
720
37%
1146
September11th to 20thNight
44%
720
25%
1980
14%
720
52%
720
35%
1178
September21st to endNight
38%
720
26%
1980
14%
720
49%
720
33%
1215
October1st to 10thNight
35%
720
19%
1980
11%
720
43%
720
24%
1343
October11th to 20thNight
29%
720
22%
2223
8%
720
45%
720
24%
1412
October21st to endNight
23%
792
17%
2574
8%
792
36%
792
16%
1748
November1st to 10thNight
27%
740
24%
2407
10%
740
44%
740
23%
1472
November11th to 20thNight
24%
760
26%
2470
10%
760
44%
760
20%
1533
November21st to endNight
21%
760
21%
2474
7%
760
39%
760
19%
1557
December1st to 10thNight
18%
760
18%
2660
5%
760
34%
760
15%
1777
December11th to 20thNight
21%
760
19%
3188
6%
759
36%
759
13%
2013
December21st to endNight
17%
829
14%
4792
4%
817
34%
817
9%
3144

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
17%7%35%5%345%5%7%39%
74807
Night
17%7%35%5%3445%7%40%
74914
TransparencyDay
46%310%23%15%3
74512
Night
45%310%24%15%2
74743
SeeingDay
23%16%32%19%8%2
13835
Night
22%13%32%25%8%1
22795

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 10thDay
15%9%35%5%3345%7%42%
1517
11th to 20thDay
17%9%36%4345%5%6%38%
1454
21st to endDay
12%8%37%5%45%5%46%42%
1584
February1st to 10thDay
16%10%36%45%5%46%6%36%
1607
11th to 20thDay
13%8%36%5%445%6%6%40%
1748
21st to endDay
16%11%47%6%45%445%35%
1480
March1st to 10thDay
15%9%35%6%35%45%7%38%
1797
11th to 20thDay
16%8%37%424347%42%
1908
21st to endDay
17%9%46%443445%41%
2276
April1st to 10thDay
19%10%35%5%2345%6%38%
2160
11th to 20thDay
16%6%36%6%35%5%6%7%38%
2182
21st to endDay
23%7%46%6%44445%32%
2340
May1st to 10thDay
25%7%36%5%3445%6%32%
2340
11th to 20thDay
18%6%36%5%3445%7%39%
2368
21st to endDay
17%6%36%5%35%5%6%7%39%
2725
June1st to 10thDay
22%7%35%5%345%5%7%31%
2520
11th to 20thDay
17%6%35%5%445%6%7%39%
2520
21st to endDay
20%7%36%5%35%5%5%8%32%
2520
July1st to 10thDay
16%5%35%5%36%5%6%9%37%
2520
11th to 20thDay
14%6%25%5%36%6%6%9%37%
2520
21st to endDay
15%5%25%6%36%6%7%8%37%
2744
August1st to 10thDay
12%5%36%6%46%6%7%8%38%
2377
11th to 20thDay
13%6%36%6%35%5%7%9%38%
2304
21st to endDay
12%415%435%5%7%8%44%
2408
September1st to 10thDay
13%5%24435%5%5%8%47%
2147
11th to 20thDay
14%5%24423346%54%
1980
21st to endDay
15%5%2443445%7%47%
1980
October1st to 10thDay
22%7%26%43345%5%39%
1980
11th to 20thDay
16%7%245%35%45%7%43%
1734
21st to endDay
25%6%25%43445%438%
1782
November1st to 10thDay
16%5%35%334447%48%
1671
11th to 20thDay
20%5%234245%6%7%44%
1710
21st to endDay
21%7%25%42445%5%42%
1706
December1st to 10thDay
20%9%35%5%3446%7%34%
1520
11th to 20thDay
22%7%35%433346%42%
1906
21st to endDay
24%11%35%4245%6%5%32%
2772
January1st to 10thNight
15%8%35%43445%7%41%
2649
11th to 20thNight
15%11%36%6%45%5%5%7%33%
2546
21st to endNight
12%7%36%6%45%6%5%6%41%
2772
February1st to 10thNight
15%10%37%6%35%45%6%36%
2350
11th to 20thNight
12%9%35%5%45%5%5%6%41%
2098
21st to endNight
14%8%35%6%3445%7%40%
1776
March1st to 10thNight
14%10%35%445%5%45%41%
2150
11th to 20thNight
17%5%36%5%45%5%6%6%38%
2051
21st to endNight
18%8%45%434446%42%
2077
April1st to 10thNight
19%8%35%6%34446%37%
1800
11th to 20thNight
18%7%35%424446%40%
1725
21st to endNight
23%7%345%3446%7%35%
1620
May1st to 10thNight
22%7%35%6%35%5%6%7%31%
1620
11th to 20thNight
18%7%36%6%46%5%6%6%34%
1540
21st to endNight
18%6%36%5%35%5%48%37%
1550
June1st to 10thNight
21%7%26%5%345%6%7%34%
1440
11th to 20thNight
19%7%35%5%3445%7%39%
1440
21st to endNight
18%6%25%5%34448%39%
1440
July1st to 10thNight
15%425%5%36%5%6%9%40%
1440
11th to 20thNight
14%5%25%5%345%8%9%39%
1440
21st to endNight
13%415%5%35%46%9%46%
1574
August1st to 10thNight
12%6%25%5%35%5%6%8%44%
1544
11th to 20thNight
14%6%246%35%46%10%39%
1596
21st to endNight
15%425%4335%5%7%46%
1945
September1st to 10thNight
14%4144245%5%7%51%
1811
11th to 20thNight
15%5%2342345%6%52%
1980
21st to endNight
15%5%26%32345%7%49%
1980
October1st to 10thNight
20%6%26%5%335%46%39%
1980
11th to 20thNight
16%6%25%5%445%5%7%41%
2223
21st to endNight
24%8%34434346%36%
2574
November1st to 10thNight
16%6%25%43435%7%44%
2407
11th to 20thNight
18%6%25%423446%44%
2470
21st to endNight
17%7%345%245%5%7%43%
2474
December1st to 10thNight
19%9%45%5%3345%6%36%
2660
11th to 20thNight
21%7%245%2445%5%40%
3288
21st to endNight
23%9%36%5%34345%34%
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
43%38%27%17%2
1518
11th to 20thDay
49%413%19%12%3
1454
21st to endDay
45%38%24%18%2
1584
February1st to 10thDay
50%312%21%12%2
1607
11th to 20thDay
45%410%22%15%4
1757
21st to endDay
53%28%19%15%3
1480
March1st to 10thDay
47%312%19%14%5%
1800
11th to 20thDay
45%29%20%19%6%
1908
21st to endDay
47%36%19%19%6%
2276
April1st to 10thDay
49%27%20%17%4
2160
11th to 20thDay
46%49%22%17%3
2182
21st to endDay
55%36%17%16%4
2340
May1st to 10thDay
53%37%20%16%2
2340
11th to 20thDay
46%48%21%18%4
2372
21st to endDay
45%413%23%13%3
2725
June1st to 10thDay
52%410%22%11%
2520
11th to 20thDay
45%310%22%17%3
2520
21st to endDay
52%411%21%12%1
2520
July1st to 10thDay
43%5%12%23%16%1
2450
11th to 20thDay
42%5%12%28%12%1
2445
21st to endDay
43%413%24%14%2
2591
August1st to 10thDay
42%5%15%24%13%1
2363
11th to 20thDay
42%5%14%27%12%1
2304
21st to endDay
37%5%12%25%19%2
2408
September1st to 10thDay
36%412%29%17%1
2147
11th to 20thDay
35%38%27%25%3
1980
21st to endDay
38%29%28%20%2
1980
October1st to 10thDay
48%37%23%16%2
1980
11th to 20thDay
42%211%32%13%1
1734
21st to endDay
50%29%22%15%2
1782
November1st to 10thDay
38%313%27%17%3
1671
11th to 20thDay
40%410%23%21%4
1710
21st to endDay
44%415%22%14%1
1706
December1st to 10thDay
50%312%21%13%1
1520
11th to 20thDay
46%29%20%19%4
1906
21st to endDay
55%211%20%10%2
2772
January1st to 10thNight
44%310%25%14%3
2649
11th to 20thNight
51%5%12%20%10%2
2546
21st to endNight
44%48%22%19%3
2772
February1st to 10thNight
50%310%19%15%3
2350
11th to 20thNight
45%49%23%16%4
2100
21st to endNight
45%39%23%15%5%
1776
March1st to 10thNight
47%37%22%18%3
2160
11th to 20thNight
46%310%21%16%5%
2052
21st to endNight
45%38%17%21%5%
2077
April1st to 10thNight
50%28%20%16%4
1800
11th to 20thNight
47%27%24%19%1
1725
21st to endNight
49%39%21%14%4
1620
May1st to 10thNight
52%47%21%13%3
1620
11th to 20thNight
49%49%20%13%4
1541
21st to endNight
46%5%14%22%11%2
1551
June1st to 10thNight
49%5%11%22%12%1
1440
11th to 20thNight
46%413%20%15%2
1440
21st to endNight
45%5%14%25%11%1
1440
July1st to 10thNight
40%6%15%23%15%1
1400
11th to 20thNight
40%5%15%28%12%
1392
21st to endNight
36%5%14%32%12%1
1486
August1st to 10thNight
37%7%14%28%14%1
1534
11th to 20thNight
40%5%15%23%16%
1596
21st to endNight
38%411%28%19%1
1945
September1st to 10thNight
34%5%12%30%18%1
1811
11th to 20thNight
33%39%29%22%2
1980
21st to endNight
37%310%31%18%2
1980
October1st to 10thNight
45%310%24%15%2
1980
11th to 20thNight
43%311%29%13%1
2223
21st to endNight
51%39%23%13%2
2574
November1st to 10thNight
42%311%25%18%2
2407
11th to 20thNight
42%49%25%18%3
2470
21st to endNight
43%314%25%14%1
2474
December1st to 10thNight
50%310%23%12%1
2660
11th to 20thNight
47%311%18%20%1
3288
21st to endNight
55%28%24%11%1
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
28%19%33%17%31
180
11th to 20thDay
27%21%34%12%32
164
21st to endDay
19%20%43%14%4
176
February1st to 10thDay
30%23%32%13%2
297
11th to 20thDay
25%23%34%15%4
416
21st to endDay
30%18%30%17%4
346
March1st to 10thDay
27%20%35%15%4
420
11th to 20thDay
24%27%32%12%41
420
21st to endDay
27%20%30%13%7%2
462
April1st to 10thDay
32%20%29%11%6%2
420
11th to 20thDay
26%27%27%12%6%2
412
21st to endDay
33%19%29%12%6%2
420
May1st to 10thDay
34%16%30%14%32
423
11th to 20thDay
23%18%35%16%5%2
447
21st to endDay
22%16%31%23%7%1
485
June1st to 10thDay
22%15%36%18%7%1
450
11th to 20thDay
18%17%36%21%6%2
450
21st to endDay
22%14%34%18%10%2
450
July1st to 10thDay
20%7%33%28%9%4
445
11th to 20thDay
17%7%32%28%13%3
444
21st to endDay
15%7%38%29%9%2
488
August1st to 10thDay
13%10%27%30%17%3
446
11th to 20thDay
16%8%32%25%15%5%
439
21st to endDay
14%11%29%28%15%4
495
September1st to 10thDay
17%9%27%26%13%7%
450
11th to 20thDay
20%12%29%17%12%9%
450
21st to endDay
16%12%35%24%9%5%
450
October1st to 10thDay
27%12%24%22%12%3
450
11th to 20thDay
19%14%32%21%11%2
385
21st to endDay
33%12%30%20%6%
396
November1st to 10thDay
21%16%33%22%6%1
365
11th to 20thDay
31%16%28%20%41
370
21st to endDay
29%20%28%17%5%1
366
December1st to 10thDay
25%25%28%15%7%
180
11th to 20thDay
29%22%37%9%3
180
21st to endDay
32%18%33%12%6%
198
January1st to 10thNight
21%18%38%21%2
760
11th to 20thNight
26%17%33%20%3
728
21st to endNight
18%21%37%21%41
792
February1st to 10thNight
24%18%37%19%2
720
11th to 20thNight
21%18%38%19%3
703
21st to endNight
23%16%35%22%4
592
March1st to 10thNight
25%15%38%19%2
720
11th to 20thNight
23%17%34%21%41
720
21st to endNight
26%15%32%19%6%
792
April1st to 10thNight
25%16%35%20%4
720
11th to 20thNight
23%15%35%20%6%
661
21st to endNight
26%16%32%21%5%
540
May1st to 10thNight
26%11%32%25%5%1
540
11th to 20thNight
22%15%35%22%6%
479
21st to endNight
22%8%27%33%9%1
389
June1st to 10thNight
24%7%33%26%10%
360
11th to 20thNight
21%8%31%28%13%
360
21st to endNight
22%330%36%9%
360
July1st to 10thNight
17%228%37%15%
350
11th to 20thNight
14%423%39%19%1
348
21st to endNight
14%426%42%13%1
394
August1st to 10thNight
16%5%22%41%16%
470
11th to 20thNight
17%6%25%34%17%1
532
21st to endNight
16%5%25%35%17%2
757
September1st to 10thNight
17%331%32%16%1
720
11th to 20thNight
18%7%26%26%19%3
720
21st to endNight
18%8%30%27%16%2
720
October1st to 10thNight
23%11%24%27%13%2
720
11th to 20thNight
19%11%33%24%11%1
720
21st to endNight
30%13%28%24%4
792
November1st to 10thNight
20%13%33%25%8%1
740
11th to 20thNight
24%17%30%22%6%1
760
21st to endNight
22%20%31%23%5%
760
December1st to 10thNight
26%13%37%19%5%
760
11th to 20thNight
24%18%31%22%4
760
21st to endNight
27%16%33%22%2
836
Page generated at 2024-01-09 16:24:24. Version ac07

Copyright 2024 Attilla Danko


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