Visalia
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Visalia clear sky chart from 2005-11-05 to 2018-01-12.

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
77%
15968
31%
48349
30%
15934
79%
15934
49%
24089

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
67%
761
19%
2637
23%
760
68%
760
30%
1513
January16th to endNight
66%
768
25%
2496
28%
768
67%
768
30%
1473
February1st to 15thNight
69%
700
26%
2139
28%
700
70%
700
34%
1260
February16th to endNight
67%
632
24%
1895
27%
632
68%
632
33%
1138
March1st to 15thNight
73%
720
21%
2140
24%
720
74%
720
40%
1176
March16th to endNight
70%
768
25%
2001
21%
768
72%
768
45%
1144
April1st to 15thNight
64%
719
28%
1799
17%
719
67%
719
44%
1059
April16th to endNight
68%
720
30%
1800
15%
720
72%
720
54%
968
May1st to 15thNight
75%
624
32%
1704
22%
624
77%
624
63%
801
May16th to endNight
66%
471
32%
1595
27%
471
72%
471
50%
702
June1st to 15thNight
75%
360
35%
1440
37%
360
83%
360
60%
501
June16th to endNight
88%
360
41%
1440
50%
360
92%
360
85%
404
July1st to 15thNight
94%
340
37%
1360
44%
340
96%
340
74%
420
July16th to endNight
91%
477
41%
1509
42%
447
92%
447
67%
581
August1st to 15thNight
92%
708
38%
1782
25%
705
93%
705
84%
779
August16th to endNight
95%
764
46%
1910
30%
764
95%
764
85%
833
September1st to 15thNight
92%
720
43%
1800
32%
720
93%
720
79%
819
September16th to endNight
90%
716
47%
1964
44%
716
92%
716
78%
827
October1st to 15thNight
83%
720
34%
2085
35%
720
85%
720
58%
989
October16th to endNight
84%
768
42%
2313
46%
768
86%
768
61%
1038
November1st to 15thNight
81%
760
30%
2470
35%
760
82%
760
48%
1190
November16th to endNight
76%
780
27%
2535
30%
780
77%
780
42%
1297
December1st to 15thNight
72%
780
24%
2623
27%
780
73%
780
34%
1455
December16th to endNight
65%
832
24%
2912
28%
832
67%
832
27%
1722

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
5%212212235%68%
48993
Night
6%212212235%67%
48530
TransparencyDay
19%48%19%26%21%
48673
Night
20%49%21%26%18%
48350
SeeingDay
6%316%32%30%9%
6232
Night
7%18%34%38%9%
15978

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
11%7%36%5%34447%41%
1541
16th to endDay
14%6%245%34345%44%
1728
February1st to 15thDay
12%6%24323436%47%
1723
16th to endDay
14%42442435%6%47%
1579
March1st to 15thDay
9%3134245%6%8%50%
1818
16th to endDay
9%313324337%56%
2223
April1st to 15thDay
9%413312245%59%
2149
16th to endDay
5%112212345%66%
2160
May1st to 15thDay
21121223477%
2244
16th to endDay
312212236%73%
2517
June1st to 15thDay
11111223479%
2520
16th to endDay
111289%
2520
July1st to 15thDay
111112384%
2520
16th to endDay
111121113480%
2553
August1st to 15thDay
1111288%
2168
16th to endDay
11112387%
2292
September1st to 15thDay
111111286%
2160
16th to endDay
11113384%
1995
October1st to 15thDay
42121233473%
1872
16th to endDay
312313235%72%
1909
November1st to 15thDay
6%312323346%61%
1719
16th to endDay
8%5%1432435%6%54%
1755
December1st to 15thDay
11%424324447%49%
1664
16th to endDay
13%6%25%414337%45%
1664
January1st to 15thNight
12%6%23312347%51%
2637
16th to endNight
14%5%14313346%49%
2496
February1st to 15thNight
11%413323436%54%
2128
16th to endNight
16%423212336%53%
1895
March1st to 15thNight
7%31322445%7%56%
2140
16th to endNight
9%212313348%58%
2001
April1st to 15thNight
9%222313446%59%
1799
16th to endNight
4212212335%69%
1800
May1st to 15thNight
3112112236%74%
1704
16th to endNight
4111212325%73%
1594
June1st to 15thNight
211211225%78%
1440
16th to endNight
1291%
1440
July1st to 15thNight
1122484%
1440
16th to endNight
1221112480%
1613
August1st to 15thNight
1111288%
1791
16th to endNight
1122387%
1910
September1st to 15thNight
111112384%
1800
16th to endNight
1112484%
1964
October1st to 15thNight
4111213226%71%
2085
16th to endNight
421111123475%
2313
November1st to 15thNight
6%213212336%66%
2470
16th to endNight
7%313323247%60%
2535
December1st to 15thNight
9%424323446%54%
2623
16th to endNight
13%424324346%50%
2912

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
39%8%13%17%17%3
1541
16th to endDay
40%8%13%15%15%7%
1728
February1st to 15thDay
36%5%15%22%16%3
1723
16th to endDay
36%8%11%30%11%1
1579
March1st to 15thDay
31%7%15%23%18%3
1818
16th to endDay
29%6%15%25%19%3
2223
April1st to 15thDay
28%410%30%20%6%
2149
16th to endDay
18%6%12%25%27%9%
2160
May1st to 15thDay
13%28%24%37%13%
2244
16th to endDay
14%37%28%34%10%
2520
June1st to 15thDay
10%27%18%31%28%
2520
16th to endDay
4127%33%50%
2520
July1st to 15thDay
6%137%25%55%
2371
16th to endDay
9%2310%24%49%
2394
August1st to 15thDay
5%38%31%50%
2153
16th to endDay
6%27%39%43%
2292
September1st to 15thDay
7%2312%32%41%
2160
16th to endDay
6%1318%45%24%
1995
October1st to 15thDay
15%35%24%27%23%
1872
16th to endDay
16%48%22%27%20%
1909
November1st to 15thDay
23%5%13%25%27%4
1719
16th to endDay
30%6%11%24%22%5%
1755
December1st to 15thDay
32%7%12%20%19%7%
1664
16th to endDay
38%7%14%20%16%2
1664
January1st to 15thNight
34%5%12%24%18%4
2637
16th to endNight
35%5%13%18%18%9%
2496
February1st to 15thNight
33%5%11%26%18%4
2139
16th to endNight
34%5%12%29%15%2
1895
March1st to 15thNight
26%5%16%25%21%4
2140
16th to endNight
25%5%15%29%19%4
2001
April1st to 15thNight
26%5%10%30%20%6%
1799
16th to endNight
17%5%13%26%29%7%
1800
May1st to 15thNight
13%36%25%36%15%
1705
16th to endNight
15%46%21%37%13%
1595
June1st to 15thNight
10%26%19%31%28%
1440
16th to endNight
2136%31%54%
1440
July1st to 15thNight
6%147%23%57%
1360
16th to endNight
10%229%22%52%
1509
August1st to 15thNight
6%29%29%51%
1782
16th to endNight
5%27%40%43%
1910
September1st to 15thNight
7%1311%30%44%
1800
16th to endNight
7%1218%43%26%
1964
October1st to 15thNight
16%35%22%30%22%
2085
16th to endNight
14%27%25%30%18%
2313
November1st to 15thNight
19%413%25%28%6%
2470
16th to endNight
24%412%23%27%7%
2535
December1st to 15thNight
30%5%12%22%20%7%
2623
16th to endNight
36%6%13%23%16%3
2912

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
27%113%33%16%7%
103
16th to endDay
17%111%37%20%11%
256
February1st to 15thDay
18%117%26%24%12%
261
16th to endDay
15%5%17%37%17%5%
238
March1st to 15thDay
8%6%22%28%25%8%
270
16th to endDay
11%9%23%29%22%3
288
April1st to 15thDay
12%12%23%26%19%5%
269
16th to endDay
412%31%31%15%4
270
May1st to 15thDay
45%27%31%24%5%
288
16th to endDay
36%25%28%28%6%
330
June1st to 15thDay
15%20%33%33%5%
315
16th to endDay
113%32%40%11%
315
July1st to 15thDay
27%33%42%13%
305
16th to endDay
1333%49%11%
327
August1st to 15thDay
212%44%32%8%
315
16th to endDay
6%37%40%13%
332
September1st to 15thDay
19%39%39%9%
315
16th to endDay
1318%33%34%8%
315
October1st to 15thDay
3223%34%29%6%
315
16th to endDay
3413%31%34%12%
325
November1st to 15thDay
5%112%25%32%22%
135
16th to endDay
10%214%28%34%10%
135
December1st to 15thDay
13%212%37%26%7%
114
16th to endDay
18%49%25%28%14%
96
January1st to 15thNight
15%7%32%29%14%
764
16th to endNight
16%27%32%31%10%
768
February1st to 15thNight
13%18%33%31%11%
704
16th to endNight
17%18%38%25%7%
632
March1st to 15thNight
8%29%41%30%7%
720
16th to endNight
10%211%39%31%4
768
April1st to 15thNight
9%317%39%26%2
719
16th to endNight
5%6%17%35%30%5%
720
May1st to 15thNight
4215%40%35%2
625
16th to endNight
45%19%34%34%1
473
June1st to 15thNight
3116%45%31%1
360
16th to endNight
9%46%40%2
360
July1st to 15thNight
335%56%5%
340
16th to endNight
221%63%11%
477
August1st to 15thNight
2228%59%6%
708
16th to endNight
121%65%11%
764
September1st to 15thNight
1225%58%12%
720
16th to endNight
16%31%46%13%
716
October1st to 15thNight
47%36%39%11%
720
16th to endNight
5%6%30%39%18%
768
November1st to 15thNight
7%5%34%36%15%
760
16th to endNight
9%25%34%34%13%
780
December1st to 15thNight
11%5%41%31%8%
780
16th to endNight
15%18%39%28%6%
832
Page generated at 2018-01-12 19:01:26. Version ac04

Copyright 2018 A. Danko


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