California City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the California City clear sky chart from 2005-11-05 to 2017-10-06.

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
67%
15774
39%
47019
29%
15731
76%
15731
64%
20254

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
63%
716
30%
2506
27%
716
73%
716
50%
1108
January16th to endNight
61%
768
39%
2389
32%
768
72%
768
51%
1136
February1st to 15thNight
61%
699
36%
2104
31%
696
71%
696
54%
988
February16th to endNight
56%
632
35%
1895
29%
632
68%
632
49%
944
March1st to 15thNight
59%
720
33%
2160
26%
720
71%
720
55%
983
March16th to endNight
55%
768
38%
2009
22%
768
69%
768
66%
945
April1st to 15thNight
47%
719
36%
1799
14%
719
61%
719
61%
902
April16th to endNight
51%
720
40%
1800
14%
720
64%
720
73%
821
May1st to 15thNight
55%
587
38%
1667
21%
587
64%
587
72%
684
May16th to endNight
51%
561
37%
1685
21%
561
63%
561
70%
662
June1st to 15thNight
63%
422
38%
1502
31%
422
74%
422
80%
478
June16th to endNight
76%
360
43%
1440
44%
360
85%
360
89%
390
July1st to 15thNight
90%
340
36%
1360
42%
340
94%
340
66%
457
July16th to endNight
87%
549
39%
1575
34%
513
88%
513
68%
661
August1st to 15thNight
83%
717
38%
1790
23%
713
85%
713
84%
777
August16th to endNight
89%
764
46%
1910
30%
764
90%
764
83%
848
September1st to 15thNight
85%
720
44%
1830
31%
720
90%
720
80%
813
September16th to endNight
81%
716
50%
1980
40%
716
90%
716
85%
780
October1st to 15thNight
71%
684
41%
1897
32%
684
81%
684
68%
843
October16th to endNight
74%
704
45%
2156
40%
704
85%
704
71%
867
November1st to 15thNight
74%
700
39%
2275
37%
700
84%
700
66%
898
November16th to endNight
72%
720
39%
2340
39%
720
80%
720
62%
971
December1st to 15thNight
65%
720
37%
2340
31%
720
76%
720
51%
1060
December16th to endNight
59%
768
34%
2610
29%
768
69%
768
44%
1238

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
111112235%76%
48158
Night
211112235%76%
47215
TransparencyDay
11%25%16%27%36%
47845
Night
11%25%18%30%31%
47028
SeeingDay
310%25%29%21%9%
5937
Night
2322%39%27%3
15786

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 15thDay
5%22223348%63%
1432
16th to endDay
6%313313346%62%
1829
February1st to 15thDay
21222335%7%67%
1751
16th to endDay
5%22323346%62%
1579
March1st to 15thDay
211111336%10%65%
1800
16th to endDay
111111335%9%68%
2211
April1st to 15thDay
2112212236%73%
2149
16th to endDay
1111236%79%
2160
May1st to 15thDay
111112484%
2280
16th to endDay
11111125%81%
2429
June1st to 15thDay
11225%84%
2454
16th to endDay
11290%
2520
July1st to 15thDay
1121122380%
2520
16th to endDay
112112225%76%
2478
August1st to 15thDay
111111385%
2160
16th to endDay
1222385%
2292
September1st to 15thDay
1222483%
2130
16th to endDay
11111288%
1980
October1st to 15thDay
2111223478%
1857
16th to endDay
1111224478%
1715
November1st to 15thDay
111112336%76%
1584
16th to endDay
22213238%70%
1620
December1st to 15thDay
22222346%10%61%
1620
16th to endDay
431422336%7%60%
1608
January1st to 15thNight
3213212347%66%
2506
16th to endNight
4313212237%66%
2389
February1st to 15thNight
2112213346%68%
2101
16th to endNight
5%212224436%64%
1895
March1st to 15thNight
21221335%8%68%
2160
16th to endNight
11211348%73%
2009
April1st to 15thNight
2111112236%74%
1799
16th to endNight
111226%81%
1800
May1st to 15thNight
111235%83%
1667
16th to endNight
11122484%
1684
June1st to 15thNight
1125%87%
1502
16th to endNight
1392%
1440
July1st to 15thNight
2111123382%
1440
16th to endNight
11111222478%
1685
August1st to 15thNight
11112288%
1800
16th to endNight
112387%
1910
September1st to 15thNight
11112385%
1830
16th to endNight
112388%
1980
October1st to 15thNight
1121233478%
1897
16th to endNight
121123480%
2156
November1st to 15thNight
111111246%77%
2275
16th to endNight
22112347%73%
2340
December1st to 15thNight
322213237%69%
2340
16th to endNight
4213212348%64%
2610

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
21%48%25%26%13%
1432
16th to endDay
24%29%22%24%17%
1829
February1st to 15thDay
17%37%23%29%17%
1751
16th to endDay
22%37%23%30%11%
1579
March1st to 15thDay
13%210%27%24%21%
1800
16th to endDay
13%39%25%29%17%
2211
April1st to 15thDay
14%16%24%32%20%
2149
16th to endDay
8%17%23%33%25%
2160
May1st to 15thDay
6%1420%33%34%
2280
16th to endDay
9%417%39%28%
2432
June1st to 15thDay
6%1311%26%50%
2454
16th to endDay
41414%74%
2520
July1st to 15thDay
9%12416%65%
2371
16th to endDay
12%229%22%50%
2325
August1st to 15thDay
6%116%17%66%
2146
16th to endDay
6%11425%60%
2292
September1st to 15thDay
7%227%23%56%
2130
16th to endDay
5%7%33%51%
1980
October1st to 15thDay
11%1314%33%34%
1857
16th to endDay
9%2314%28%40%
1715
November1st to 15thDay
11%26%19%38%22%
1584
16th to endDay
15%37%23%28%22%
1620
December1st to 15thDay
18%6%10%23%27%14%
1620
16th to endDay
23%5%10%25%23%10%
1608
January1st to 15thNight
18%38%22%30%17%
2506
16th to endNight
20%27%22%26%21%
2389
February1st to 15thNight
17%29%20%28%20%
2112
16th to endNight
21%26%24%31%13%
1895
March1st to 15thNight
14%39%24%26%20%
2160
16th to endNight
11%211%31%28%15%
2009
April1st to 15thNight
14%26%30%32%15%
1799
16th to endNight
7%26%29%36%17%
1800
May1st to 15thNight
5%2423%37%25%
1668
16th to endNight
7%15%18%44%21%
1685
June1st to 15thNight
31415%31%43%
1502
16th to endNight
226%20%67%
1440
July1st to 15thNight
8%216%16%64%
1360
16th to endNight
11%1312%24%46%
1575
August1st to 15thNight
5%17%24%59%
1790
16th to endNight
5%16%31%54%
1910
September1st to 15thNight
7%128%28%51%
1830
16th to endNight
4118%38%47%
1980
October1st to 15thNight
10%2312%35%35%
1897
16th to endNight
8%1313%29%41%
2156
November1st to 15thNight
11%15%18%37%26%
2275
16th to endNight
12%27%21%27%27%
2340
December1st to 15thNight
17%39%22%29%17%
2340
16th to endNight
20%5%11%25%24%13%
2610

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%11%30%31%10%6%
60
16th to endDay
10%12%22%25%20%9%
268
February1st to 15thDay
417%23%21%23%8%
266
16th to endDay
8%20%23%24%16%6%
238
March1st to 15thDay
416%27%22%19%9%
270
16th to endDay
5%18%29%23%18%4
288
April1st to 15thDay
7%20%31%21%12%5%
269
16th to endDay
422%37%22%9%3
270
May1st to 15thDay
214%33%28%15%5%
288
16th to endDay
216%29%26%17%7%
330
June1st to 15thDay
112%33%26%16%9%
315
16th to endDay
433%29%20%12%
315
July1st to 15thDay
223%36%22%14%
305
16th to endDay
3115%43%22%13%
327
August1st to 15thDay
1226%34%21%13%
315
16th to endDay
117%40%24%15%
332
September1st to 15thDay
1422%32%29%10%
315
16th to endDay
15%18%31%31%11%
315
October1st to 15thDay
212%27%25%26%5%
278
16th to endDay
27%25%25%30%8%
227
November1st to 15thDay
26%11%18%34%26%
90
16th to endDay
13%17%40%25%3
90
December1st to 15thDay
26%20%37%28%4
90
16th to endDay
9%11%17%36%21%3
76
January1st to 15thNight
5%223%37%26%4
720
16th to endNight
6%224%39%24%2
768
February1st to 15thNight
2426%38%23%4
704
16th to endNight
6%5%28%37%17%3
632
March1st to 15thNight
26%28%39%19%3
720
16th to endNight
26%34%35%19%1
768
April1st to 15thNight
48%36%32%16%1
719
16th to endNight
28%36%32%17%2
720
May1st to 15thNight
7%35%39%15%1
588
16th to endNight
9%35%37%15%
563
June1st to 15thNight
331%50%13%
422
16th to endNight
22%56%20%
360
July1st to 15thNight
25%55%36%
340
16th to endNight
26%47%41%2
549
August1st to 15thNight
112%44%37%3
717
16th to endNight
8%37%46%6%
764
September1st to 15thNight
10%38%44%5%
720
16th to endNight
115%36%40%5%
716
October1st to 15thNight
1321%39%30%4
684
16th to endNight
219%32%38%5%
704
November1st to 15thNight
3118%38%33%5%
700
16th to endNight
3119%38%30%5%
720
December1st to 15thNight
5%320%41%26%2
720
16th to endNight
6%5%25%37%22%2
768
Page generated at 2017-10-07 11:07:48. Version ac04

Copyright 2017 A. Danko


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