Las Vegas
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Las Vegas clear sky chart from 2005-11-06 to 2024-01-15.

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
71%
24447
38%
74410
31%
24404
80%
24404
60%
33004

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
64%
757
34%
2457
30%
756
74%
756
49%
1149
January11th to 20thNight
70%
738
38%
2398
34%
738
79%
738
53%
1059
January21st to endNight
63%
792
39%
2534
31%
792
76%
792
47%
1213
February1st to 10thNight
67%
720
39%
2160
31%
720
78%
720
55%
1007
February11th to 20thNight
61%
700
39%
2099
31%
700
75%
700
49%
1011
February21st to endNight
58%
592
39%
1776
33%
592
70%
592
52%
839
March1st to 10thNight
58%
720
35%
2160
28%
720
71%
720
53%
1002
March11th to 20thNight
62%
720
36%
1985
27%
720
72%
720
53%
1004
March21st to endNight
59%
792
38%
2178
23%
792
72%
792
60%
1022
April1st to 10thNight
60%
720
38%
1832
20%
720
70%
720
60%
901
April11th to 20thNight
55%
711
38%
1779
16%
711
66%
711
62%
880
April21st to endNight
65%
581
44%
1661
25%
581
77%
581
65%
719
May1st to 10thNight
61%
540
39%
1620
23%
540
70%
540
61%
691
May11th to 20thNight
70%
531
42%
1595
29%
531
78%
531
71%
641
May21st to endNight
66%
582
35%
1746
25%
582
73%
582
64%
725
June1st to 10thNight
75%
540
37%
1620
30%
540
80%
540
77%
610
June11th to 20thNight
72%
540
37%
1620
29%
540
78%
540
75%
626
June21st to endNight
81%
540
35%
1620
31%
540
85%
540
78%
621
July1st to 10thNight
89%
525
35%
1575
32%
525
90%
525
72%
644
July11th to 20thNight
88%
522
33%
1566
29%
522
88%
522
63%
695
July21st to endNight
87%
591
35%
1674
31%
558
87%
558
55%
789
August1st to 10thNight
84%
537
40%
1602
32%
534
85%
534
61%
713
August11th to 20thNight
88%
671
40%
1739
27%
671
89%
671
72%
802
August21st to endNight
89%
792
43%
1980
30%
792
90%
792
74%
936
September1st to 10thNight
86%
720
41%
1890
31%
720
88%
720
70%
874
September11th to 20thNight
86%
720
46%
1980
39%
720
90%
720
81%
820
September21st to endNight
83%
720
47%
1980
38%
720
90%
720
79%
819
October1st to 10thNight
73%
720
42%
1980
31%
720
83%
720
67%
898
October11th to 20thNight
77%
720
47%
2042
40%
720
84%
720
70%
878
October21st to endNight
73%
792
45%
2484
38%
792
85%
792
71%
942
November1st to 10thNight
76%
740
42%
2405
39%
740
86%
740
69%
933
November11th to 20thNight
78%
760
43%
2470
40%
760
87%
760
66%
972
November21st to endNight
71%
760
41%
2470
38%
760
81%
760
60%
1038
December1st to 10thNight
68%
760
37%
2470
33%
760
76%
760
51%
1133
December11th to 20thNight
68%
758
35%
2889
31%
758
78%
758
41%
1377
December21st to endNight
59%
823
23%
4374
31%
817
70%
817
28%
2021

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
2212223346%74%
74912
Night
2212223346%74%
74914
TransparencyDay
13%35%14%27%38%
74639
Night
13%3415%27%38%
74709
SeeingDay
48%21%35%24%8%
14154
Night
3418%39%31%5%
24471

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
331222235%7%69%
1708
11th to 20thDay
4311213446%72%
1656
21st to endDay
331332345%5%69%
1821
February1st to 10thDay
2212214346%72%
1800
11th to 20thDay
311222345%7%70%
1750
21st to endDay
3223323345%70%
1480
March1st to 10thDay
3322223347%69%
1800
11th to 20thDay
3422313348%67%
1975
21st to endDay
221232345%7%70%
2178
April1st to 10thDay
1212223446%72%
2124
11th to 20thDay
2212212345%78%
2129
21st to endDay
2111112336%78%
2297
May1st to 10thDay
1111213345%79%
2340
11th to 20thDay
111212346%79%
2301
21st to endDay
1112212235%79%
2530
June1st to 10thDay
111111123484%
2340
11th to 20thDay
11111123386%
2340
21st to endDay
11111222485%
2340
July1st to 10thDay
111232444475%
2340
11th to 20thDay
2212323448%69%
2340
21st to endDay
31235%35%5%7%9%57%
2545
August1st to 10thDay
2212223445%73%
2328
11th to 20thDay
2112223346%76%
2159
21st to endDay
211212446%76%
2376
September1st to 10thDay
3112223235%76%
2070
11th to 20thDay
11111223486%
1980
21st to endDay
11121223483%
1980
October1st to 10thDay
2212212235%77%
1980
11th to 20thDay
111211222483%
1918
21st to endDay
1111223485%
1868
November1st to 10thDay
1211211335%80%
1674
11th to 20thDay
1212312345%77%
1710
21st to endDay
3112212336%75%
1710
December1st to 10thDay
332322235%6%69%
1710
11th to 20thDay
43143245%6%9%56%
2169
21st to endDay
43233235%6%8%60%
3146
January1st to 10thNight
3413323447%66%
2457
11th to 20thNight
331232345%6%69%
2398
21st to endNight
5%31232445%7%66%
2534
February1st to 10thNight
2312323346%71%
2160
11th to 20thNight
4312323345%70%
2098
21st to endNight
331232345%6%69%
1776
March1st to 10thNight
321232345%9%67%
2160
11th to 20thNight
432322335%7%67%
1985
21st to endNight
2212213336%74%
2178
April1st to 10thNight
2113213347%74%
1832
11th to 20thNight
2112223336%75%
1779
21st to endNight
1112213335%79%
1661
May1st to 10thNight
211122225%6%76%
1620
11th to 20thNight
211112235%82%
1594
21st to endNight
1111213245%79%
1746
June1st to 10thNight
21223485%
1620
11th to 20thNight
111111235%84%
1620
21st to endNight
1111223484%
1620
July1st to 10thNight
1111212345%79%
1620
11th to 20thNight
2212322446%73%
1620
21st to endNight
22134245%7%10%61%
1773
August1st to 10thNight
221322344474%
1611
11th to 20thNight
1112212346%78%
1739
21st to endNight
1111211245%79%
1980
September1st to 10thNight
1112211345%78%
1890
11th to 20thNight
111111122387%
1980
21st to endNight
11111122386%
1980
October1st to 10thNight
3112212335%78%
1980
11th to 20thNight
211121122383%
2042
21st to endNight
11121113484%
2484
November1st to 10thNight
111121223481%
2405
11th to 20thNight
122212235%80%
2470
21st to endNight
2212213335%77%
2470
December1st to 10thNight
431331335%8%67%
2470
11th to 20thNight
431332346%8%61%
3041
21st to endNight
5%4234345%6%7%56%
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
15%5%10%30%34%7%
1709
11th to 20thDay
16%48%29%32%12%
1656
21st to endDay
18%46%26%35%10%
1821
February1st to 10thDay
16%37%21%31%21%
1800
11th to 20thDay
15%35%18%34%24%
1760
21st to endDay
18%36%18%35%20%
1480
March1st to 10thDay
16%35%19%35%22%
1800
11th to 20thDay
18%45%16%35%22%
1975
21st to endDay
14%46%22%35%19%
2178
April1st to 10thDay
14%4415%32%31%
2124
11th to 20thDay
11%2314%28%41%
2132
21st to endDay
10%3311%35%38%
2297
May1st to 10thDay
10%2414%29%42%
2340
11th to 20thDay
8%2311%31%45%
2304
21st to endDay
10%2310%30%46%
2530
June1st to 10thDay
7%129%20%62%
2340
11th to 20thDay
5%215%16%70%
2340
21st to endDay
6%21312%75%
2340
July1st to 10thDay
13%346%13%62%
2276
11th to 20thDay
13%45%10%20%47%
2271
21st to endDay
21%5%7%14%20%34%
2404
August1st to 10thDay
13%439%17%53%
2313
11th to 20thDay
11%339%21%53%
2159
21st to endDay
11%339%21%54%
2376
September1st to 10thDay
13%337%16%58%
2070
11th to 20thDay
6%227%21%61%
1980
21st to endDay
8%226%26%56%
1980
October1st to 10thDay
13%2312%23%47%
1980
11th to 20thDay
8%239%30%47%
1918
21st to endDay
7%2311%36%43%
1868
November1st to 10thDay
9%3316%40%30%
1674
11th to 20thDay
12%35%16%41%24%
1710
21st to endDay
13%35%21%36%23%
1710
December1st to 10thDay
16%410%23%30%17%
1710
11th to 20thDay
24%7%10%25%27%7%
2168
21st to endDay
21%6%13%28%23%9%
3146
January1st to 10thNight
19%47%27%32%10%
2457
11th to 20thNight
16%45%26%32%17%
2398
21st to endNight
20%46%24%31%15%
2534
February1st to 10thNight
17%36%18%33%22%
2160
11th to 20thNight
20%3318%27%29%
2099
21st to endNight
16%4416%36%23%
1776
March1st to 10thNight
15%45%18%35%23%
2160
11th to 20thNight
18%4314%32%29%
1985
21st to endNight
14%35%19%36%23%
2178
April1st to 10thNight
13%35%15%30%34%
1832
11th to 20thNight
14%2312%31%38%
1779
21st to endNight
9%3211%30%45%
1661
May1st to 10thNight
12%2311%28%45%
1620
11th to 20thNight
8%2212%26%50%
1595
21st to endNight
10%229%26%50%
1746
June1st to 10thNight
5%227%19%65%
1620
11th to 20thNight
7%115%14%70%
1620
21st to endNight
7%1139%79%
1620
July1st to 10thNight
9%326%13%68%
1575
11th to 20thNight
13%349%18%52%
1566
21st to endNight
17%45%17%21%36%
1674
August1st to 10thNight
13%328%15%58%
1602
11th to 20thNight
9%438%20%56%
1739
21st to endNight
9%328%21%57%
1980
September1st to 10thNight
10%338%16%60%
1890
11th to 20thNight
6%237%19%63%
1980
21st to endNight
7%117%22%62%
1980
October1st to 10thNight
12%239%24%51%
1980
11th to 20thNight
10%227%25%55%
2042
21st to endNight
7%2312%27%49%
2484
November1st to 10thNight
9%2215%38%34%
2405
11th to 20thNight
10%2316%34%35%
2470
21st to endNight
14%2315%34%32%
2470
December1st to 10thNight
17%47%21%29%22%
2470
11th to 20thNight
22%5%9%20%33%11%
3041
21st to endNight
23%8%8%26%28%7%
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
9%7%21%44%15%3
270
11th to 20thDay
12%320%40%20%5%
252
21st to endDay
411%19%33%26%7%
303
February1st to 10thDay
6%9%21%36%23%5%
420
11th to 20thDay
7%12%27%33%17%4
415
21st to endDay
6%15%28%34%16%1
346
March1st to 10thDay
7%18%26%31%15%2
420
11th to 20thDay
6%13%28%33%15%4
420
21st to endDay
6%16%36%31%10%2
462
April1st to 10thDay
5%13%31%29%16%6%
420
11th to 20thDay
6%18%30%31%13%3
412
21st to endDay
5%16%27%28%19%5%
420
May1st to 10thDay
411%31%34%16%5%
423
11th to 20thDay
310%23%38%18%8%
448
21st to endDay
210%25%33%21%8%
485
June1st to 10thDay
17%24%37%23%9%
450
11th to 20thDay
28%23%33%25%10%
450
21st to endDay
15%22%37%26%11%
450
July1st to 10thDay
1215%39%29%13%
446
11th to 20thDay
1210%37%35%14%
444
21st to endDay
219%38%36%15%
487
August1st to 10thDay
4117%37%27%14%
447
11th to 20thDay
3112%37%32%16%
437
21st to endDay
3112%35%36%14%
495
September1st to 10thDay
2315%34%32%14%
450
11th to 20thDay
15%21%36%28%9%
450
21st to endDay
2419%32%35%8%
450
October1st to 10thDay
25%21%37%27%8%
450
11th to 20thDay
26%19%29%35%9%
388
21st to endDay
25%22%29%31%11%
297
November1st to 10thDay
29%19%30%31%9%
270
11th to 20thDay
35%12%42%27%11%
270
21st to endDay
36%20%34%28%10%
270
December1st to 10thDay
3419%40%28%6%
270
11th to 20thDay
3420%37%28%9%
270
21st to endDay
7%8%27%35%17%5%
297
January1st to 10thNight
4422%36%27%6%
760
11th to 20thNight
4419%44%24%5%
738
21st to endNight
6%323%40%22%5%
792
February1st to 10thNight
3422%44%24%4
720
11th to 20thNight
46%25%40%21%4
704
21st to endNight
5%7%27%41%18%2
592
March1st to 10thNight
37%28%40%19%3
720
11th to 20thNight
46%23%37%24%6%
720
21st to endNight
28%29%40%19%3
792
April1st to 10thNight
29%26%39%20%4
720
11th to 20thNight
29%32%32%20%4
711
21st to endNight
18%23%40%23%5%
581
May1st to 10thNight
36%27%42%20%2
540
11th to 20thNight
25%20%39%29%4
531
21st to endNight
18%21%36%31%3
584
June1st to 10thNight
1417%45%29%3
540
11th to 20thNight
1422%41%29%3
540
21st to endNight
215%44%35%4
540
July1st to 10thNight
16%42%46%5%
525
11th to 20thNight
2439%50%4
522
21st to endNight
21333%57%4
591
August1st to 10thNight
217%44%43%3
537
11th to 20thNight
15%33%53%7%
671
21st to endNight
215%29%51%13%
792
September1st to 10thNight
226%32%50%9%
720
11th to 20thNight
1110%39%42%8%
720
21st to endNight
1212%38%38%9%
720
October1st to 10thNight
3417%42%31%3
720
11th to 20thNight
2215%39%33%8%
720
21st to endNight
25%17%33%35%8%
792
November1st to 10thNight
1218%38%34%7%
740
11th to 20thNight
2314%42%34%5%
760
21st to endNight
3320%42%27%5%
760
December1st to 10thNight
5%320%40%28%4
760
11th to 20thNight
6%319%40%29%3
760
21st to endNight
5%7%24%39%22%4
836
Page generated at 2024-01-12 04:31:47. Version ac07

Copyright 2024 Attilla Danko


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