Blue Ridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blue Ridge clear sky chart from 2005-11-06 to 2024-03-28.

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
64%
23827
28%
80694
24%
23744
71%
23744
39%
42678

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
49%
748
20%
4268
17%
736
54%
736
16%
2324
January11th to 20thNight
51%
750
16%
4091
16%
740
59%
740
14%
2733
January21st to endNight
53%
830
15%
4438
22%
814
61%
814
15%
2978
February1st to 10thNight
53%
760
26%
2470
23%
760
62%
760
29%
1457
February11th to 20thNight
50%
740
25%
2328
19%
740
60%
740
30%
1362
February21st to endNight
53%
628
27%
1884
21%
628
62%
628
36%
1060
March1st to 10thNight
47%
760
17%
2142
13%
760
52%
760
26%
1399
March11th to 20thNight
53%
760
25%
2090
20%
760
59%
760
33%
1293
March21st to endNight
49%
820
21%
2217
12%
820
56%
820
36%
1341
April1st to 10thNight
53%
720
25%
1800
12%
720
59%
720
38%
1122
April11th to 20thNight
54%
711
30%
1779
13%
711
61%
711
47%
1017
April21st to endNight
63%
720
31%
1800
15%
720
68%
720
57%
947
May1st to 10thNight
64%
626
30%
1706
18%
626
70%
626
56%
847
May11th to 20thNight
73%
438
31%
1500
27%
438
78%
438
56%
625
May21st to endNight
68%
388
28%
1552
26%
388
78%
388
53%
582
June1st to 10thNight
71%
360
28%
1440
30%
360
79%
360
48%
596
June11th to 20thNight
74%
360
37%
1440
41%
360
84%
360
69%
464
June21st to endNight
80%
360
36%
1440
44%
360
86%
360
69%
469
July1st to 10thNight
87%
350
37%
1400
45%
350
93%
350
79%
414
July11th to 20thNight
88%
449
38%
1493
38%
449
91%
449
78%
526
July21st to endNight
86%
591
40%
1674
33%
558
90%
558
79%
632
August1st to 10thNight
81%
537
37%
1602
29%
534
84%
534
71%
651
August11th to 20thNight
84%
632
41%
1700
26%
632
86%
632
81%
713
August21st to endNight
89%
792
43%
1980
27%
792
90%
792
84%
873
September1st to 10thNight
88%
720
46%
1800
31%
720
90%
720
85%
776
September11th to 20thNight
81%
720
43%
1800
31%
720
85%
720
71%
858
September21st to endNight
80%
720
42%
2046
38%
720
86%
720
72%
873
October1st to 10thNight
74%
720
34%
2160
32%
720
82%
720
61%
947
October11th to 20thNight
73%
720
37%
2160
36%
720
81%
720
57%
989
October21st to endNight
68%
792
38%
2376
35%
792
77%
792
53%
1130
November1st to 10thNight
65%
740
31%
2285
27%
740
73%
740
43%
1186
November11th to 20thNight
63%
760
29%
2470
27%
760
70%
760
39%
1302
November21st to endNight
60%
760
28%
2645
28%
760
67%
760
35%
1356
December1st to 10thNight
51%
760
23%
2660
18%
760
60%
760
26%
1568
December11th to 20thNight
49%
759
18%
3240
18%
759
56%
759
17%
2226
December21st to endNight
42%
826
14%
4818
16%
817
52%
817
12%
3042

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
8%423323346%61%
78904
Night
9%423323447%58%
81116
TransparencyDay
24%410%20%24%18%
78620
Night
27%5%11%19%21%17%
80921
SeeingDay
8%7%20%31%25%8%
14434
Night
9%418%37%28%4
23871

By Month

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 10thDay
16%9%35%5%35%45%6%39%
2617
11th to 20thDay
18%9%48%6%34445%35%
2860
21st to endDay
21%8%36%5%346%5%7%33%
3146
February1st to 10thDay
15%5%25%435%46%5%45%
1710
11th to 20thDay
13%5%25%6%35%5%5%8%45%
1739
21st to endDay
13%5%25%5%3345%6%49%
1570
March1st to 10thDay
13%8%36%6%36%5%6%8%37%
2036
11th to 20thDay
14%5%36%5%35%5%6%7%42%
2090
21st to endDay
11%5%24425%5%7%7%48%
2292
April1st to 10thDay
12%7%345%345%6%8%44%
2160
11th to 20thDay
9%3233235%47%58%
2129
21st to endDay
332343345%8%63%
2160
May1st to 10thDay
431331235%7%67%
2251
11th to 20thDay
421322345%8%67%
2391
21st to endDay
321222346%8%66%
2723
June1st to 10thDay
431321345%8%66%
2520
11th to 20thDay
11112246%80%
2520
21st to endDay
111112235%82%
2520
July1st to 10thDay
11112235%86%
2520
11th to 20thDay
111111225%86%
2413
21st to endDay
111111236%83%
2546
August1st to 10thDay
1111212335%80%
2328
11th to 20thDay
11111223484%
2201
21st to endDay
11111126%85%
2376
September1st to 10thDay
1111222486%
2160
11th to 20thDay
2112212447%75%
2160
21st to endDay
2212211235%78%
1911
October1st to 10thDay
2213213345%74%
1800
11th to 20thDay
5%413323236%69%
1800
21st to endDay
7%323322345%66%
1980
November1st to 10thDay
8%423325%35%7%58%
1793
11th to 20thDay
9%6%35%42445%6%51%
1710
21st to endDay
10%31443445%6%57%
1530
December1st to 10thDay
14%6%3442346%6%47%
1520
11th to 20thDay
28%9%46%423345%32%
1928
21st to endDay
21%8%36%43435%7%37%
2794
January1st to 10thNight
13%7%25%42345%8%46%
4313
11th to 20thNight
20%7%36%435%5%5%6%35%
4110
21st to endNight
20%7%36%5%3445%7%35%
4521
February1st to 10thNight
15%424434445%51%
2470
11th to 20thNight
11%425%4345%5%8%49%
2326
21st to endNight
12%42432345%6%55%
1884
March1st to 10thNight
14%6%36%5%35%5%46%43%
2142
11th to 20thNight
13%6%14435%46%7%48%
2090
21st to endNight
11%5%25%423346%54%
2217
April1st to 10thNight
8%4246%44448%53%
1800
11th to 20thNight
8%31332345%7%61%
1779
21st to endNight
5%212223349%66%
1800
May1st to 10thNight
3212323348%69%
1706
11th to 20thNight
311222335%8%69%
1500
21st to endNight
321121235%9%71%
1552
June1st to 10thNight
3213323348%69%
1440
11th to 20thNight
111112246%81%
1440
21st to endNight
111113335%82%
1440
July1st to 10thNight
11111225%87%
1440
11th to 20thNight
112112126%84%
1542
21st to endNight
1111112349%77%
1773
August1st to 10thNight
211222349%74%
1611
11th to 20thNight
1111235%7%79%
1700
21st to endNight
11111248%80%
1980
September1st to 10thNight
11111237%85%
1800
11th to 20thNight
2212212337%76%
1800
21st to endNight
1111212246%79%
2046
October1st to 10thNight
4112312345%74%
2160
11th to 20thNight
321232335%7%69%
2160
21st to endNight
6%212323346%67%
2376
November1st to 10thNight
6%22442445%8%58%
2285
11th to 20thNight
8%5%2432345%7%57%
2470
21st to endNight
8%424424347%59%
2645
December1st to 10thNight
15%425%5%33347%48%
2660
11th to 20thNight
28%7%3442445%7%33%
3276
21st to endNight
17%7%36%6%345%5%6%37%
4862

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
45%9%10%26%8%2
2617
11th to 20thDay
51%7%10%14%12%6%
2860
21st to endDay
51%7%11%16%11%4
3146
February1st to 10thDay
39%6%8%20%19%8%
1710
11th to 20thDay
37%6%10%19%20%8%
1748
21st to endDay
35%411%24%18%9%
1570
March1st to 10thDay
44%5%13%18%16%3
2036
11th to 20thDay
40%6%9%23%16%7%
2090
21st to endDay
33%9%14%19%20%5%
2292
April1st to 10thDay
37%7%13%19%19%7%
2160
11th to 20thDay
25%7%13%23%23%8%
2132
21st to endDay
20%5%15%27%26%7%
2160
May1st to 10thDay
17%412%25%30%11%
2251
11th to 20thDay
16%411%30%28%11%
2394
21st to endDay
16%6%18%29%23%8%
2724
June1st to 10thDay
17%5%12%27%28%10%
2520
11th to 20thDay
7%311%23%34%23%
2520
21st to endDay
7%27%16%35%34%
2520
July1st to 10thDay
5%25%14%25%49%
2451
11th to 20thDay
6%16%15%26%46%
2339
21st to endDay
6%15%11%25%52%
2405
August1st to 10thDay
8%27%18%30%36%
2312
11th to 20thDay
6%16%14%35%38%
2201
21st to endDay
6%16%16%33%39%
2376
September1st to 10thDay
5%15%9%31%49%
2160
11th to 20thDay
12%39%22%38%16%
2160
21st to endDay
11%36%18%33%29%
1911
October1st to 10thDay
14%47%17%31%27%
1800
11th to 20thDay
19%48%19%25%26%
1800
21st to endDay
21%48%20%27%20%
1980
November1st to 10thDay
26%5%9%27%21%13%
1793
11th to 20thDay
33%6%11%23%20%7%
1710
21st to endDay
30%410%21%24%11%
1530
December1st to 10thDay
37%5%10%21%18%8%
1520
11th to 20thDay
56%5%7%12%15%4
1928
21st to endDay
46%7%14%18%12%3
2794
January1st to 10thNight
35%9%19%23%10%4
4313
11th to 20thNight
48%8%13%12%11%7%
4110
21st to endNight
49%6%12%14%13%5%
4521
February1st to 10thNight
36%49%20%21%11%
2470
11th to 20thNight
34%5%11%20%20%11%
2328
21st to endNight
30%410%26%23%7%
1884
March1st to 10thNight
41%6%15%15%18%5%
2142
11th to 20thNight
36%49%23%19%9%
2090
21st to endNight
32%5%13%22%21%7%
2217
April1st to 10thNight
31%6%14%19%21%9%
1800
11th to 20thNight
23%6%12%27%19%13%
1779
21st to endNight
17%412%31%29%8%
1800
May1st to 10thNight
16%5%12%19%34%13%
1706
11th to 20thNight
14%314%26%29%13%
1500
21st to endNight
12%5%19%31%23%11%
1552
June1st to 10thNight
15%6%10%26%29%13%
1440
11th to 20thNight
8%28%22%35%25%
1440
21st to endNight
7%36%15%31%39%
1440
July1st to 10thNight
5%1316%25%50%
1400
11th to 20thNight
7%15%16%21%50%
1493
21st to endNight
6%15%17%20%50%
1674
August1st to 10thNight
10%17%19%26%37%
1602
11th to 20thNight
6%27%14%27%44%
1700
21st to endNight
6%15%18%26%43%
1980
September1st to 10thNight
5%1410%29%51%
1800
11th to 20thNight
11%38%20%35%24%
1800
21st to endNight
9%37%18%28%35%
2046
October1st to 10thNight
13%39%17%27%30%
2160
11th to 20thNight
15%410%17%26%28%
2160
21st to endNight
18%39%20%26%24%
2376
November1st to 10thNight
24%5%10%24%21%16%
2285
11th to 20thNight
27%411%27%21%9%
2470
21st to endNight
27%5%9%20%25%14%
2645
December1st to 10thNight
37%5%9%19%18%11%
2660
11th to 20thNight
51%5%11%13%17%4
3276
21st to endNight
45%8%12%17%13%4
4862

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
31%10%22%19%15%3
232
11th to 20thDay
16%10%19%32%17%5%
370
21st to endDay
16%8%19%27%25%5%
407
February1st to 10thDay
18%14%16%26%22%5%
370
11th to 20thDay
19%13%22%25%15%5%
401
21st to endDay
15%10%25%30%16%3
382
March1st to 10thDay
20%13%26%28%10%4
460
11th to 20thDay
20%10%23%24%17%6%
460
21st to endDay
13%14%27%27%16%2
491
April1st to 10thDay
15%11%27%25%18%5%
420
11th to 20thDay
10%13%30%24%18%6%
412
21st to endDay
412%25%26%24%8%
420
May1st to 10thDay
5%11%30%27%22%5%
423
11th to 20thDay
5%8%28%31%20%9%
448
21st to endDay
37%24%32%25%9%
485
June1st to 10thDay
5%8%24%34%23%7%
450
11th to 20thDay
17%22%39%28%3
450
21st to endDay
1320%38%31%6%
450
July1st to 10thDay
1113%46%31%7%
446
11th to 20thDay
1112%39%39%9%
444
21st to endDay
112%41%34%11%
487
August1st to 10thDay
2314%40%31%11%
447
11th to 20thDay
1116%33%33%15%
437
21st to endDay
1111%37%37%14%
495
September1st to 10thDay
129%37%37%14%
450
11th to 20thDay
27%16%34%31%11%
450
21st to endDay
2418%33%30%12%
450
October1st to 10thDay
38%20%26%27%15%
450
11th to 20thDay
6%5%18%28%30%13%
450
21st to endDay
9%7%17%29%26%12%
495
November1st to 10thDay
9%8%20%24%29%10%
389
11th to 20thDay
10%7%17%27%30%8%
270
21st to endDay
13%5%21%33%25%3
185
December1st to 10thDay
18%9%22%25%18%8%
180
11th to 20thDay
19%7%24%27%17%6%
180
21st to endDay
20%10%21%26%19%5%
198
January1st to 10thNight
19%5%19%33%21%5%
760
11th to 20thNight
16%6%18%37%19%5%
760
21st to endNight
17%5%18%33%25%3
836
February1st to 10thNight
17%6%18%35%22%3
760
11th to 20thNight
13%7%22%31%22%5%
744
21st to endNight
14%7%20%37%19%2
628
March1st to 10thNight
16%7%23%30%22%2
760
11th to 20thNight
17%6%19%31%25%2
760
21st to endNight
13%6%25%37%18%1
820
April1st to 10thNight
9%426%38%20%2
720
11th to 20thNight
9%7%26%33%21%4
711
21st to endNight
6%5%24%38%24%3
720
May1st to 10thNight
4425%37%27%3
626
11th to 20thNight
4218%42%32%3
438
21st to endNight
4323%43%26%1
389
June1st to 10thNight
3220%47%26%2
360
11th to 20thNight
2121%49%26%1
360
21st to endNight
117%52%29%1
360
July1st to 10thNight
111%56%32%
350
11th to 20thNight
18%49%37%4
449
21st to endNight
118%48%38%4
591
August1st to 10thNight
1112%42%39%5%
537
11th to 20thNight
13%42%39%5%
632
21st to endNight
18%43%43%4
792
September1st to 10thNight
119%42%43%5%
720
11th to 20thNight
2213%42%36%5%
720
21st to endNight
2213%39%38%7%
720
October1st to 10thNight
4314%38%33%7%
720
11th to 20thNight
4316%36%35%6%
720
21st to endNight
7%416%32%31%9%
792
November1st to 10thNight
7%417%31%34%6%
740
11th to 20thNight
10%317%35%30%5%
760
21st to endNight
9%7%17%37%25%6%
760
December1st to 10thNight
16%6%19%31%22%5%
760
11th to 20thNight
22%5%17%31%22%3
760
21st to endNight
19%8%22%32%19%
836
Page generated at 2024-03-24 20:36:58. Version ac07

Copyright © 2024 Attilla Danko.


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