Lyndon B. Johnson State Park & Historic Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lyndon B. Johnson State Park & Historic Site clear sky chart from 2005-11-05 to 2018-10-08.

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
50%
16787
26%
51127
18%
16740
58%
16740
35%
29125

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
37%
974
28%
2522
11%
970
47%
970
36%
1545
January16th to endNight
36%
935
31%
2599
12%
935
49%
935
35%
1550
February1st to 15thNight
33%
764
28%
2287
12%
758
45%
758
31%
1317
February16th to endNight
22%
684
27%
2050
7%
684
38%
684
29%
1207
March1st to 15thNight
33%
627
27%
2187
14%
627
48%
627
28%
1251
March16th to endNight
32%
624
24%
2288
15%
624
45%
624
27%
1285
April1st to 15thNight
29%
584
23%
2142
12%
584
46%
584
27%
1198
April16th to endNight
30%
579
26%
1871
14%
579
46%
579
29%
1120
May1st to 15thNight
32%
584
24%
1754
15%
584
45%
584
30%
1060
May16th to endNight
50%
610
24%
1828
19%
609
60%
609
35%
1071
June1st to 15thNight
67%
585
24%
1755
22%
585
75%
585
52%
863
June16th to endNight
67%
585
23%
1755
24%
585
71%
585
40%
971
July1st to 15thNight
75%
555
20%
1665
21%
555
79%
555
42%
914
July16th to endNight
83%
612
27%
1738
29%
579
86%
579
49%
887
August1st to 15thNight
88%
575
29%
1815
34%
572
89%
572
54%
842
August16th to endNight
78%
621
20%
2115
24%
621
79%
621
33%
1184
September1st to 15thNight
76%
585
19%
2145
23%
585
77%
585
28%
1252
September16th to endNight
68%
582
23%
2145
24%
582
72%
582
26%
1271
October1st to 15thNight
70%
564
32%
2068
31%
564
73%
564
38%
1031
October16th to endNight
58%
756
37%
2292
24%
756
66%
756
48%
1139
November1st to 15thNight
50%
812
27%
2332
16%
812
56%
812
37%
1346
November16th to endNight
47%
975
33%
2535
15%
975
56%
975
42%
1460
December1st to 15thNight
40%
975
29%
2535
14%
975
47%
975
33%
1598
December16th to endNight
36%
1040
25%
2704
10%
1040
44%
1040
30%
1763

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
10%42443445%7%47%
52006
Night
9%413323447%53%
51329
Cloud CoverDay
11%42443445%7%47%
52004
Night
9%423323447%53%
51329
TransparencyDay
36%5%9%19%19%9%
51704
Night
30%5%11%21%19%11%
51134
SeeingDay
11%6%21%32%22%5%
6755
Night
11%6%28%36%15%1
16790

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
13%423433345%51%
1746
16th to endDay
12%314322346%54%
1989
February1st to 15thDay
12%6%24323336%51%
1900
16th to endDay
14%6%2431335%5%49%
1710
March1st to 15thDay
15%5%25%323446%46%
2103
16th to endDay
12%424423436%50%
2288
April1st to 15thDay
11%5%25%433346%47%
2136
16th to endDay
12%5%25%5%24345%47%
2360
May1st to 15thDay
14%6%345%345%5%7%39%
2526
16th to endDay
13%5%35%5%35%5%5%6%39%
2638
June1st to 15thDay
33245%46%6%6%9%48%
2535
16th to endDay
10%425%5%35%6%6%9%40%
2535
July1st to 15thDay
8%3346%45%6%6%9%42%
2535
16th to endDay
7%2135%25%5%6%10%48%
2674
August1st to 15thDay
221243446%9%58%
2385
16th to endDay
7%415%7%35%6%6%9%41%
2439
September1st to 15thDay
12%5%36%7%345%5%6%38%
2145
16th to endDay
10%5%25%5%35%6%6%6%42%
2145
October1st to 15thDay
9%414424446%52%
2061
16th to endDay
7%222223435%64%
1920
November1st to 15thDay
11%5%25%5%3435%6%45%
1854
16th to endDay
10%414222325%58%
1755
December1st to 15thDay
15%7%25%322246%47%
1755
16th to endDay
14%6%245%23446%45%
1872
January1st to 15thNight
14%413323336%53%
2522
16th to endNight
13%413323346%52%
2599
February1st to 15thNight
11%425%323235%54%
2282
16th to endNight
11%5%24433346%51%
2050
March1st to 15thNight
11%5%25%323346%49%
2187
16th to endNight
9%5%14325%45%6%51%
2288
April1st to 15thNight
8%425%434447%51%
2142
16th to endNight
11%434424346%49%
1871
May1st to 15thNight
10%425%424447%48%
1754
16th to endNight
8%3143245%5%10%49%
1827
June1st to 15thNight
211232335%9%64%
1755
16th to endNight
5%2133235%5%10%54%
1755
July1st to 15thNight
5%31232445%11%55%
1755
16th to endNight
42221346%10%59%
1846
August1st to 15thNight
21121336%9%66%
1825
16th to endNight
7%3134335%5%11%50%
2115
September1st to 15thNight
9%4144345%6%7%48%
2145
16th to endNight
8%425%5%345%6%8%45%
2145
October1st to 15thNight
7%312323347%59%
2068
16th to endNight
6%212223335%66%
2292
November1st to 15thNight
8%314423347%54%
2332
16th to endNight
8%413322246%59%
2535
December1st to 15thNight
13%5%23423346%50%
2535
16th to endNight
12%7%25%423336%47%
2704

Percentage Cloud Cover SE (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
13%5%14433245%51%
1746
16th to endDay
13%314323346%53%
1989
February1st to 15thDay
12%6%23323246%51%
1900
16th to endDay
14%6%2431335%5%49%
1710
March1st to 15thDay
15%5%25%323445%46%
2103
16th to endDay
13%424423446%49%
2286
April1st to 15thDay
11%5%25%433346%48%
2136
16th to endDay
13%5%25%424446%47%
2360
May1st to 15thDay
14%6%35%5%35%5%5%6%39%
2526
16th to endDay
14%5%25%5%35%45%6%39%
2638
June1st to 15thDay
33145%35%6%7%9%48%
2535
16th to endDay
10%425%6%35%5%6%8%40%
2535
July1st to 15thDay
8%3346%35%6%6%9%42%
2535
16th to endDay
6%3135%25%5%6%10%48%
2674
August1st to 15thDay
221243446%9%57%
2385
16th to endDay
7%415%6%36%6%7%9%42%
2439
September1st to 15thDay
12%6%36%7%345%5%6%39%
2145
16th to endDay
10%5%25%6%35%6%5%6%42%
2145
October1st to 15thDay
9%414334446%52%
2061
16th to endDay
7%212213435%64%
1920
November1st to 15thDay
12%436%5%3335%6%45%
1854
16th to endDay
11%423313325%58%
1755
December1st to 15thDay
15%6%25%313246%46%
1755
16th to endDay
13%7%235%23346%46%
1872
January1st to 15thNight
14%413323336%53%
2522
16th to endNight
13%313323346%52%
2599
February1st to 15thNight
12%425%313335%54%
2282
16th to endNight
11%5%23423446%51%
2050
March1st to 15thNight
11%425%313347%50%
2187
16th to endNight
9%5%2342445%6%51%
2288
April1st to 15thNight
8%5%24424447%51%
2142
16th to endNight
11%5%34424346%49%
1871
May1st to 15thNight
10%42443435%7%49%
1754
16th to endNight
8%31442445%10%49%
1827
June1st to 15thNight
111232335%9%64%
1755
16th to endNight
5%2133335%6%9%54%
1755
July1st to 15thNight
5%31232445%11%55%
1755
16th to endNight
421221346%10%59%
1846
August1st to 15thNight
211121345%9%66%
1825
16th to endNight
7%3134245%5%11%50%
2115
September1st to 15thNight
9%4244245%6%7%48%
2145
16th to endNight
8%425%5%3446%9%45%
2145
October1st to 15thNight
7%212323347%60%
2068
16th to endNight
6%212313345%66%
2292
November1st to 15thNight
8%414413447%54%
2332
16th to endNight
9%413322245%59%
2535
December1st to 15thNight
13%5%24413335%50%
2535
16th to endNight
13%6%24323345%47%
2704

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
36%3418%22%13%
1747
16th to endDay
32%36%13%27%16%
1989
February1st to 15thDay
35%46%14%21%17%
1901
16th to endDay
38%36%17%20%13%
1710
March1st to 15thDay
39%5%7%14%20%13%
2103
16th to endDay
36%5%8%17%20%11%
2288
April1st to 15thDay
37%48%16%19%13%
2136
16th to endDay
39%46%20%18%10%
2360
May1st to 15thDay
44%7%8%13%19%6%
2526
16th to endDay
44%7%8%19%17%3
2642
June1st to 15thDay
30%7%12%22%21%5%
2535
16th to endDay
40%7%11%21%16%3
2535
July1st to 15thDay
36%7%15%24%13%2
2396
16th to endDay
26%9%16%30%14%1
2519
August1st to 15thDay
22%6%15%36%17%1
2371
16th to endDay
36%8%17%23%10%3
2439
September1st to 15thDay
44%6%10%18%15%4
2145
16th to endDay
40%7%10%17%16%8%
2145
October1st to 15thDay
32%411%19%18%11%
2061
16th to endDay
23%45%16%28%21%
1920
November1st to 15thDay
40%48%18%17%10%
1854
16th to endDay
30%35%16%22%21%
1755
December1st to 15thDay
40%36%16%21%10%
1755
16th to endDay
40%48%14%21%11%
1872
January1st to 15thNight
33%36%17%21%18%
2522
16th to endNight
33%35%14%24%18%
2599
February1st to 15thNight
33%36%14%21%20%
2292
16th to endNight
35%46%15%22%16%
2050
March1st to 15thNight
35%39%13%21%14%
2187
16th to endNight
33%5%10%17%20%11%
2288
April1st to 15thNight
33%5%9%17%17%16%
2142
16th to endNight
36%49%18%18%12%
1871
May1st to 15thNight
34%6%11%20%17%9%
1755
16th to endNight
30%7%14%28%15%4
1829
June1st to 15thNight
16%6%15%30%25%4
1755
16th to endNight
25%7%16%31%16%3
1755
July1st to 15thNight
23%8%22%30%14%1
1665
16th to endNight
17%8%24%33%14%1
1738
August1st to 15thNight
14%6%20%39%17%1
1815
16th to endNight
28%8%22%26%10%2
2115
September1st to 15thNight
33%8%15%21%16%4
2145
16th to endNight
34%8%13%18%16%7%
2145
October1st to 15thNight
24%5%14%25%18%11%
2068
16th to endNight
21%36%17%28%23%
2292
November1st to 15thNight
30%49%23%19%12%
2332
16th to endNight
27%37%16%22%21%
2535
December1st to 15thNight
36%37%18%21%12%
2535
16th to endNight
39%46%13%22%13%
2704

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
12%11%44%24%5%
135
16th to endDay
11%14%45%21%6%
144
February1st to 15thDay
14%17%36%28%2
135
16th to endDay
25%16%40%15%
120
March1st to 15thDay
17%16%37%20%7%
135
16th to endDay
8%9%47%29%4
144
April1st to 15thDay
13%17%41%25%2
135
16th to endDay
13%13%37%27%7%
372
May1st to 15thDay
14%13%38%25%7%
543
16th to endDay
17%7%26%33%14%1
597
June1st to 15thDay
4117%50%22%2
570
16th to endDay
10%212%42%26%5%
570
July1st to 15thDay
6%111%37%35%8%
550
16th to endDay
46%35%43%10%
595
August1st to 15thDay
4340%39%11%
449
16th to endDay
9%7%30%34%17%
351
September1st to 15thDay
13%6%16%42%20%
180
16th to endDay
13%5%26%41%13%
180
October1st to 15thDay
6%8%27%40%15%
157
16th to endDay
10%8%18%34%25%2
144
November1st to 15thDay
26%428%27%11%2
135
16th to endDay
17%11%29%25%11%5%
135
December1st to 15thDay
21%6%27%29%10%4
135
16th to endDay
21%17%33%22%4
144
January1st to 15thNight
16%10%32%32%7%
975
16th to endNight
14%8%37%30%8%
935
February1st to 15thNight
15%12%36%30%5%
764
16th to endNight
15%13%46%21%2
684
March1st to 15thNight
14%10%37%33%4
627
16th to endNight
12%12%41%29%4
624
April1st to 15thNight
8%13%47%28%2
584
16th to endNight
12%9%43%26%6%
579
May1st to 15thNight
10%11%42%28%6%
585
16th to endNight
9%433%38%12%
611
June1st to 15thNight
225%49%20%
585
16th to endNight
5%120%51%18%2
585
July1st to 15thNight
5%11%49%29%2
555
16th to endNight
47%51%31%3
612
August1st to 15thNight
2449%38%5%
575
16th to endNight
8%5%43%36%5%
621
September1st to 15thNight
11%440%36%6%
585
16th to endNight
9%112%38%34%3
582
October1st to 15thNight
8%215%41%27%3
564
16th to endNight
7%5%26%34%24%2
756
November1st to 15thNight
10%5%28%35%18%1
812
16th to endNight
10%8%30%34%14%1
975
December1st to 15thNight
17%9%29%33%9%
975
16th to endNight
16%10%32%31%7%
1040
Page generated at 2018-10-09 09:39:11. Version ac04

Copyright 2018 A. Danko


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