Big Bear City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Big Bear City 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
59%
24763
37%
74348
25%
24708
71%
24708
54%
33959

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
44%
756
31%
2457
19%
756
60%
756
36%
1225
January11th to 20thNight
51%
726
36%
2327
25%
726
67%
726
42%
1130
January21st to endNight
41%
792
38%
2376
20%
792
61%
792
36%
1242
February1st to 10thNight
46%
720
36%
2160
24%
720
63%
720
43%
1074
February11th to 20thNight
44%
700
36%
2098
24%
700
62%
700
42%
1035
February21st to endNight
38%
592
34%
1776
19%
592
58%
592
39%
882
March1st to 10thNight
39%
720
30%
2160
16%
720
59%
720
37%
1121
March11th to 20thNight
47%
720
32%
2065
20%
720
61%
720
44%
1032
March21st to endNight
42%
792
35%
2077
14%
792
59%
792
44%
1091
April1st to 10thNight
41%
720
37%
1800
14%
720
56%
720
47%
949
April11th to 20thNight
43%
711
39%
1779
13%
711
58%
711
53%
883
April21st to endNight
50%
720
41%
1800
14%
720
64%
720
62%
831
May1st to 10thNight
49%
554
41%
1634
20%
554
61%
554
60%
670
May11th to 20thNight
56%
531
41%
1595
23%
531
67%
531
62%
652
May21st to endNight
56%
582
39%
1746
20%
582
69%
582
69%
673
June1st to 10thNight
68%
540
37%
1620
25%
540
75%
540
71%
642
June11th to 20thNight
65%
540
39%
1620
28%
540
72%
540
76%
613
June21st to endNight
69%
491
38%
1571
28%
491
79%
491
77%
581
July1st to 10thNight
87%
501
35%
1551
29%
501
89%
501
75%
594
July11th to 20thNight
84%
522
33%
1566
28%
522
85%
522
62%
688
July21st to endNight
84%
609
35%
1691
27%
575
85%
575
58%
796
August1st to 10thNight
82%
716
36%
1780
22%
712
84%
712
73%
850
August11th to 20thNight
88%
712
40%
1780
25%
712
90%
712
78%
816
August21st to endNight
86%
792
44%
1980
29%
792
87%
792
75%
920
September1st to 10thNight
84%
720
43%
1819
31%
720
87%
720
71%
865
September11th to 20thNight
81%
720
48%
1980
37%
720
90%
720
86%
783
September21st to endNight
75%
720
47%
1980
35%
720
86%
720
80%
806
October1st to 10thNight
65%
720
42%
1980
29%
720
78%
720
65%
892
October11th to 20thNight
68%
720
49%
1980
35%
720
81%
720
72%
835
October21st to endNight
63%
792
43%
2505
33%
792
79%
792
65%
978
November1st to 10thNight
61%
740
38%
2405
30%
740
76%
740
57%
992
November11th to 20thNight
62%
760
39%
2470
32%
760
76%
760
56%
1053
November21st to endNight
53%
760
38%
2470
29%
760
68%
760
44%
1160
December1st to 10thNight
47%
760
34%
2470
23%
760
62%
760
42%
1186
December11th to 20thNight
43%
760
34%
2918
23%
758
59%
758
31%
1463
December21st to endNight
41%
832
23%
4362
23%
817
58%
817
24%
1956

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
221332445%7%67%
74842
Night
121332345%6%70%
74838
TransparencyDay
15%5%6%14%28%33%
74571
Night
13%5%6%14%28%34%
74631
SeeingDay
6%16%33%31%11%3
14463
Night
310%24%32%24%6%
24777

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
14234246%6%9%58%
1708
11th to 20thDay
241343446%8%62%
1659
21st to endDay
35%25%43436%7%59%
1980
February1st to 10thDay
141333446%6%65%
1800
11th to 20thDay
13134345%6%8%61%
1750
21st to endDay
132443446%8%62%
1480
March1st to 10thDay
23234245%7%10%58%
1800
11th to 20thDay
2224425%46%9%60%
1894
21st to endDay
12132245%7%8%64%
2275
April1st to 10thDay
3414424446%64%
2160
11th to 20thDay
111232335%5%74%
2129
21st to endDay
2212223348%72%
2160
May1st to 10thDay
2212313346%72%
2322
11th to 20thDay
221222335%6%74%
2301
21st to endDay
2213323346%73%
2530
June1st to 10thDay
111222335%7%73%
2340
11th to 20thDay
11111233484%
2340
21st to endDay
121221223380%
2340
July1st to 10thDay
2223324435%71%
2340
11th to 20thDay
32134345%6%8%61%
2340
21st to endDay
4424425%6%7%9%53%
2522
August1st to 10thDay
2213434445%67%
2149
11th to 20thDay
11123335%6%7%67%
2122
21st to endDay
221342445%7%67%
2376
September1st to 10thDay
32123345%47%66%
2139
11th to 20thDay
111121222483%
1980
21st to endDay
1212212335%78%
1980
October1st to 10thDay
2213323245%74%
1980
11th to 20thDay
1112212235%81%
1978
21st to endDay
111212235%81%
1849
November1st to 10thDay
111232345%7%73%
1674
11th to 20thDay
12123235%5%6%69%
1710
21st to endDay
221343447%8%64%
1710
December1st to 10thDay
24235%35%5%7%9%56%
1710
11th to 20thDay
2325%446%7%7%10%50%
2169
21st to endDay
2425%6%5%7%7%7%8%48%
3146
January1st to 10thNight
1324425%6%7%8%57%
2457
11th to 20thNight
13244245%6%8%61%
2327
21st to endNight
34245%3446%6%59%
2376
February1st to 10thNight
241342446%7%63%
2160
11th to 20thNight
1323435%46%8%62%
2098
21st to endNight
1213435%7%7%9%58%
1776
March1st to 10thNight
1423435%5%8%10%56%
2160
11th to 20thNight
12233245%7%9%60%
2065
21st to endNight
1213425%6%6%7%64%
2077
April1st to 10thNight
122432347%6%65%
1800
11th to 20thNight
121221345%5%74%
1779
21st to endNight
111111345%7%75%
1800
May1st to 10thNight
111223346%77%
1634
11th to 20thNight
11121224480%
1594
21st to endNight
11112236%82%
1746
June1st to 10thNight
1112235%83%
1620
11th to 20thNight
1111212388%
1620
21st to endNight
111111122485%
1571
July1st to 10thNight
111112332383%
1596
11th to 20thNight
2113213335%74%
1620
21st to endNight
221332335%8%69%
1791
August1st to 10thNight
211121233479%
1790
11th to 20thNight
1111212235%82%
1780
21st to endNight
121211222482%
1980
September1st to 10thNight
112213345%79%
1819
11th to 20thNight
111111112390%
1980
21st to endNight
111111123388%
1980
October1st to 10thNight
11331234478%
1980
11th to 20thNight
111111123383%
1980
21st to endNight
12313235%80%
2505
November1st to 10thNight
1222335%8%74%
2405
11th to 20thNight
111332445%6%72%
2470
21st to endNight
23134246%5%8%64%
2470
December1st to 10thNight
2323435%46%9%59%
2470
11th to 20thNight
2323435%6%7%10%55%
3041
21st to endNight
13246%46%7%7%7%53%
4521

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
19%7%6%19%28%20%
1709
11th to 20thDay
20%5%9%14%31%22%
1659
21st to endDay
24%6%6%19%26%20%
1980
February1st to 10thDay
19%5%6%15%27%29%
1800
11th to 20thDay
18%6%5%17%27%26%
1760
21st to endDay
19%7%7%15%31%21%
1480
March1st to 10thDay
19%7%8%17%29%20%
1800
11th to 20thDay
19%6%6%19%29%21%
1894
21st to endDay
15%8%8%22%29%18%
2275
April1st to 10thDay
19%5%7%20%31%18%
2160
11th to 20thDay
13%4416%34%30%
2132
21st to endDay
12%46%17%41%20%
2160
May1st to 10thDay
13%46%16%33%28%
2322
11th to 20thDay
11%35%13%41%28%
2304
21st to endDay
13%35%16%36%26%
2530
June1st to 10thDay
10%3412%30%40%
2340
11th to 20thDay
5%237%22%61%
2340
21st to endDay
10%235%15%65%
2340
July1st to 10thDay
13%247%17%56%
2276
11th to 20thDay
17%5%8%16%21%33%
2271
21st to endDay
21%6%10%17%22%24%
2382
August1st to 10thDay
15%46%9%18%48%
2135
11th to 20thDay
11%6%7%14%20%43%
2122
21st to endDay
14%3311%29%39%
2376
September1st to 10thDay
16%5%6%8%22%44%
2139
11th to 20thDay
7%225%31%53%
1980
21st to endDay
10%2311%29%44%
1980
October1st to 10thDay
13%4412%28%40%
1980
11th to 20thDay
8%2311%33%43%
1978
21st to endDay
8%348%31%46%
1849
November1st to 10thDay
12%4415%33%32%
1674
11th to 20thDay
13%5%6%14%26%36%
1710
21st to endDay
18%5%7%15%29%27%
1710
December1st to 10thDay
22%7%8%16%23%24%
1710
11th to 20thDay
23%12%9%18%22%16%
2168
21st to endDay
25%12%6%18%24%14%
3146
January1st to 10thNight
20%8%8%16%27%21%
2457
11th to 20thNight
19%6%7%15%27%25%
2327
21st to endNight
24%5%6%14%25%25%
2376
February1st to 10thNight
20%5%7%13%24%31%
2160
11th to 20thNight
18%6%6%14%27%29%
2099
21st to endNight
16%9%8%14%27%26%
1776
March1st to 10thNight
20%8%7%17%26%23%
2160
11th to 20thNight
16%7%8%16%29%24%
2065
21st to endNight
16%7%7%19%34%18%
2077
April1st to 10thNight
18%47%21%31%20%
1800
11th to 20thNight
11%5%5%14%34%32%
1779
21st to endNight
8%36%15%44%24%
1800
May1st to 10thNight
7%45%16%35%32%
1634
11th to 20thNight
8%35%12%41%30%
1595
21st to endNight
6%25%17%40%30%
1746
June1st to 10thNight
7%2313%28%47%
1620
11th to 20thNight
6%128%23%60%
1620
21st to endNight
7%125%16%69%
1571
July1st to 10thNight
8%237%19%62%
1551
11th to 20thNight
13%36%18%21%38%
1566
21st to endNight
15%49%21%25%26%
1691
August1st to 10thNight
10%36%10%22%50%
1780
11th to 20thNight
7%3415%26%45%
1780
21st to endNight
10%129%31%46%
1980
September1st to 10thNight
10%348%23%52%
1819
11th to 20thNight
4137%27%58%
1980
21st to endNight
5%2310%32%49%
1980
October1st to 10thNight
10%3312%30%42%
1980
11th to 20thNight
7%239%32%46%
1980
21st to endNight
9%247%31%47%
2505
November1st to 10thNight
10%5%411%35%35%
2405
11th to 20thNight
12%5%5%12%30%36%
2470
21st to endNight
17%7%6%14%27%29%
2470
December1st to 10thNight
18%6%7%14%27%27%
2470
11th to 20thNight
20%10%9%20%22%19%
3041
21st to endNight
22%8%8%17%26%19%
4521

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
10%22%37%23%7%
270
11th to 20thDay
12%15%36%27%8%2
273
21st to endDay
9%25%34%23%7%2
462
February1st to 10thDay
6%25%34%25%7%3
420
11th to 20thDay
12%26%35%21%6%
415
21st to endDay
11%30%36%19%3
346
March1st to 10thDay
15%27%35%18%5%
420
11th to 20thDay
13%21%38%21%6%1
420
21st to endDay
11%32%35%17%4
462
April1st to 10thDay
10%23%36%23%6%1
420
11th to 20thDay
8%32%34%20%5%
412
21st to endDay
7%25%33%24%7%4
420
May1st to 10thDay
9%21%36%26%5%4
423
11th to 20thDay
5%19%38%26%8%3
448
21st to endDay
7%18%35%28%8%4
485
June1st to 10thDay
316%33%33%11%5%
450
11th to 20thDay
110%37%37%9%6%
450
21st to endDay
39%36%33%14%5%
450
July1st to 10thDay
4228%43%16%7%
446
11th to 20thDay
222%46%20%9%
444
21st to endDay
5%117%47%18%11%
487
August1st to 10thDay
3429%40%16%8%
447
11th to 20thDay
3222%45%21%8%
437
21st to endDay
3125%44%19%8%
495
September1st to 10thDay
4433%40%18%2
450
11th to 20thDay
19%35%40%13%
450
21st to endDay
213%28%37%18%2
450
October1st to 10thDay
314%38%34%11%1
450
11th to 20thDay
212%38%34%14%1
450
21st to endDay
412%33%36%13%3
364
November1st to 10thDay
6%13%35%33%11%1
270
11th to 20thDay
410%40%31%11%4
270
21st to endDay
5%19%31%32%11%1
270
December1st to 10thDay
6%17%36%31%7%2
270
11th to 20thDay
5%17%36%30%10%1
270
21st to endDay
9%28%33%21%8%2
297
January1st to 10thNight
8%15%27%26%16%8%
760
11th to 20thNight
6%11%28%30%19%6%
726
21st to endNight
6%18%30%26%17%3
792
February1st to 10thNight
7%13%30%30%16%5%
720
11th to 20thNight
417%33%26%16%4
704
21st to endNight
7%19%33%24%14%3
592
March1st to 10thNight
8%17%33%25%15%3
720
11th to 20thNight
6%16%28%26%18%6%
720
21st to endNight
421%30%27%15%3
792
April1st to 10thNight
418%32%27%14%4
720
11th to 20thNight
319%32%24%18%4
711
21st to endNight
318%28%26%19%6%
720
May1st to 10thNight
315%32%31%16%3
554
11th to 20thNight
212%26%35%22%3
531
21st to endNight
211%28%33%22%3
584
June1st to 10thNight
6%24%43%23%4
540
11th to 20thNight
16%27%42%22%2
540
21st to endNight
1126%41%26%3
491
July1st to 10thNight
19%42%39%8%
501
11th to 20thNight
37%48%37%5%
522
21st to endNight
215%40%46%7%
609
August1st to 10thNight
2112%35%38%12%
716
11th to 20thNight
117%36%43%12%
712
21st to endNight
28%32%45%13%
792
September1st to 10thNight
129%32%44%12%
720
11th to 20thNight
1115%37%36%10%
720
21st to endNight
1419%32%36%9%
720
October1st to 10thNight
27%23%41%23%4
720
11th to 20thNight
36%22%32%28%10%
720
21st to endNight
27%25%31%25%10%
792
November1st to 10thNight
310%24%32%22%9%
740
11th to 20thNight
16%26%35%23%8%
760
21st to endNight
311%29%29%22%6%
760
December1st to 10thNight
413%31%28%18%5%
760
11th to 20thNight
8%13%31%28%16%4
760
21st to endNight
5%18%31%26%15%5%
836
Page generated at 2024-01-09 04:14:44. Version ac07

Copyright 2024 Attilla Danko


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