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 2005-11-06 to 2024-01-22.

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
47%
23815
26%
74438
17%
23757
56%
23757
33%
42693

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
36%
949
31%
2458
12%
946
47%
946
38%
1472
January11th to 20thNight
33%
950
28%
2470
9%
950
45%
950
34%
1520
January21st to endNight
33%
854
32%
2454
12%
854
48%
854
30%
1485
February1st to 10thNight
28%
720
27%
2160
10%
720
42%
720
28%
1292
February11th to 20thNight
25%
704
23%
2098
9%
700
37%
700
29%
1247
February21st to endNight
17%
592
27%
1776
5%
592
35%
592
25%
1086
March1st to 10thNight
26%
599
25%
2039
10%
599
41%
599
24%
1231
March11th to 20thNight
32%
540
23%
1980
13%
540
44%
540
23%
1173
March21st to endNight
27%
594
26%
2178
14%
594
44%
594
27%
1212
April1st to 10thNight
28%
540
25%
1980
12%
540
46%
540
27%
1117
April11th to 20thNight
27%
533
23%
1894
13%
533
43%
533
24%
1125
April21st to endNight
25%
540
28%
1692
14%
540
44%
540
28%
1035
May1st to 10thNight
31%
540
26%
1620
15%
540
45%
540
30%
983
May11th to 20thNight
40%
531
21%
1594
17%
531
48%
531
31%
977
May21st to endNight
45%
583
21%
1745
16%
582
56%
582
30%
1074
June1st to 10thNight
65%
540
24%
1620
22%
540
72%
540
46%
847
June11th to 20thNight
58%
540
25%
1620
23%
540
66%
540
48%
823
June21st to endNight
67%
540
24%
1620
26%
540
71%
540
40%
902
July1st to 10thNight
71%
525
17%
1575
18%
525
74%
525
34%
944
July11th to 20thNight
78%
522
27%
1566
29%
522
83%
522
51%
784
July21st to endNight
80%
591
26%
1673
26%
558
85%
558
51%
828
August1st to 10thNight
87%
537
30%
1648
32%
534
89%
534
61%
730
August11th to 20thNight
80%
534
24%
1778
29%
534
81%
534
37%
951
August21st to endNight
78%
594
20%
2042
23%
594
79%
594
34%
1125
September1st to 10thNight
75%
540
21%
1980
23%
540
77%
540
33%
1091
September11th to 20thNight
68%
540
22%
1980
24%
540
71%
540
26%
1182
September21st to endNight
70%
540
26%
1980
27%
540
74%
540
32%
1076
October1st to 10thNight
72%
540
33%
1980
34%
540
74%
540
41%
956
October11th to 20thNight
56%
612
32%
2052
23%
612
63%
612
33%
1145
October21st to endNight
45%
792
33%
2376
18%
792
55%
792
38%
1319
November1st to 10thNight
53%
740
29%
2220
19%
740
58%
740
36%
1283
November11th to 20thNight
48%
931
28%
2451
14%
931
55%
931
41%
1437
November21st to endNight
36%
950
27%
2470
12%
950
45%
950
31%
1583
December1st to 10thNight
42%
950
31%
2470
15%
950
51%
950
36%
1504
December11th to 20thNight
33%
948
26%
2895
12%
948
41%
948
25%
1848
December21st to endNight
34%
1040
18%
4304
11%
1026
44%
1026
24%
2306

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
11%5%25%5%345%5%7%49%
74956
Night
10%5%2442445%7%53%
75014
TransparencyDay
35%6%10%20%20%10%
74681
Night
31%6%11%20%20%12%
74809
SeeingDay
12%8%24%31%20%5%
13741
Night
12%8%29%36%14%1
23824

By Month

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 10thDay
12%5%1433335%5%55%
1707
11th to 20thDay
15%6%2442335%6%51%
1710
21st to endDay
13%5%24433346%54%
1953
February1st to 10thDay
14%7%24434347%48%
1800
11th to 20thDay
15%7%3442445%6%47%
1749
21st to endDay
16%5%2432335%5%51%
1480
March1st to 10thDay
16%7%37%43445%7%42%
1921
11th to 20thDay
12%6%25%5%345%5%5%48%
1980
21st to endDay
13%5%25%424446%50%
2178
April1st to 10thDay
12%6%36%5%34447%46%
1980
11th to 20thDay
17%6%25%43445%5%45%
2011
21st to endDay
13%5%25%5%34446%49%
2266
May1st to 10thDay
13%5%345%35%6%6%8%41%
2340
11th to 20thDay
14%8%37%6%45%45%6%40%
2302
21st to endDay
15%5%36%6%36%6%6%8%37%
2531
June1st to 10thDay
5%425%5%36%6%7%8%49%
2340
11th to 20thDay
7%4245%35%6%6%9%50%
2340
21st to endDay
7%426%6%45%6%8%9%42%
2340
July1st to 10thDay
10%5%35%7%46%7%7%9%37%
2340
11th to 20thDay
5%323435%5%7%11%53%
2340
21st to endDay
4213435%6%7%10%54%
2546
August1st to 10thDay
221242446%9%65%
2275
11th to 20thDay
6%3245%35%6%6%9%51%
2123
21st to endDay
5%316%7%36%6%7%10%44%
2314
September1st to 10thDay
10%5%36%6%345%5%6%47%
1980
11th to 20thDay
10%5%36%7%46%6%6%7%40%
1980
21st to endDay
9%4145%35%6%6%7%50%
1980
October1st to 10thDay
7%414435%5%5%7%55%
1980
11th to 20thDay
12%5%24334445%53%
1890
21st to endDay
11%423423435%58%
1980
November1st to 10thDay
13%5%26%5%3435%6%48%
1858
11th to 20thDay
9%5%25%5%34447%51%
1726
21st to endDay
15%6%35%423435%49%
1710
December1st to 10thDay
13%6%36%42335%6%50%
1710
11th to 20thDay
12%7%25%5%2345%6%46%
2161
21st to endDay
13%6%2342233457%
3135
January1st to 10thNight
14%423323346%55%
2458
11th to 20thNight
14%424323346%54%
2470
21st to endNight
14%6%24434346%51%
2454
February1st to 10thNight
14%5%36%423346%50%
2160
11th to 20thNight
16%5%24433345%52%
2098
21st to endNight
14%6%25%6%23445%49%
1776
March1st to 10thNight
12%6%37%5%24448%45%
2039
11th to 20thNight
13%6%34425%5%5%5%47%
1980
21st to endNight
10%6%244245%5%7%52%
2178
April1st to 10thNight
9%6%35%43446%8%49%
1980
11th to 20thNight
12%6%35%434446%48%
1894
21st to endNight
13%6%24424346%50%
1692
May1st to 10thNight
10%5%3443446%7%49%
1620
11th to 20thNight
10%5%25%5%3446%9%48%
1593
21st to endNight
11%425%435%5%6%11%45%
1745
June1st to 10thNight
332343345%9%62%
1620
11th to 20thNight
421332445%9%62%
1620
21st to endNight
6%3234335%6%10%54%
1620
July1st to 10thNight
8%5%24425%5%7%11%48%
1620
11th to 20thNight
411232345%10%65%
1620
21st to endNight
32133245%6%11%61%
1772
August1st to 10thNight
1112222349%72%
1658
11th to 20thNight
6%3144245%7%9%56%
1778
21st to endNight
6%4235%346%6%11%51%
2042
September1st to 10thNight
7%424425%5%6%8%53%
1980
11th to 20thNight
8%6%26%5%4446%8%46%
1980
21st to endNight
7%4145%345%6%8%53%
1980
October1st to 10thNight
5%32332445%8%62%
1980
11th to 20thNight
11%424425%45%6%54%
2052
21st to endNight
13%42432223461%
2376
November1st to 10thNight
11%5%245%22347%55%
2220
11th to 20thNight
8%6%2342335%6%57%
2451
21st to endNight
15%5%245%3335%6%48%
2470
December1st to 10thNight
13%5%24323446%54%
2470
11th to 20thNight
12%9%36%433345%48%
3036
21st to endNight
14%7%23322335%56%
4532

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
32%3420%23%17%
1708
11th to 20thDay
36%46%15%23%17%
1710
21st to endDay
33%46%13%27%17%
1953
February1st to 10thDay
39%46%12%22%17%
1800
11th to 20thDay
39%47%18%18%14%
1759
21st to endDay
36%36%17%20%17%
1480
March1st to 10thDay
43%5%8%13%18%12%
1921
11th to 20thDay
38%7%6%13%19%17%
1980
21st to endDay
35%6%9%18%20%13%
2178
April1st to 10thDay
39%5%8%18%18%12%
1980
11th to 20thDay
42%46%17%20%11%
2011
21st to endDay
38%5%6%21%20%11%
2266
May1st to 10thDay
41%8%8%16%21%7%
2340
11th to 20thDay
45%7%8%17%18%4
2306
21st to endDay
44%8%10%21%15%2
2531
June1st to 10thDay
29%8%13%26%20%4
2340
11th to 20thDay
30%8%11%28%18%5%
2340
21st to endDay
37%9%11%22%17%4
2340
July1st to 10thDay
39%9%15%24%11%1
2276
11th to 20thDay
24%8%17%28%20%3
2271
21st to endDay
20%10%20%34%15%1
2405
August1st to 10thDay
18%5%15%40%21%1
2261
11th to 20thDay
29%8%16%30%12%4
2123
21st to endDay
32%10%17%25%13%4
2314
September1st to 10thDay
37%8%10%20%17%8%
1980
11th to 20thDay
40%9%11%18%17%5%
1980
21st to endDay
32%7%9%22%19%11%
1980
October1st to 10thDay
27%7%12%20%24%10%
1980
11th to 20thDay
34%5%8%16%22%17%
1890
21st to endDay
30%45%16%25%21%
1980
November1st to 10thDay
37%5%8%19%20%11%
1858
11th to 20thDay
34%47%17%21%15%
1726
21st to endDay
39%45%16%22%14%
1710
December1st to 10thDay
37%48%18%23%10%
1710
11th to 20thDay
39%5%8%10%21%17%
2159
21st to endDay
32%35%15%28%17%
3135
January1st to 10thNight
31%35%16%24%20%
2458
11th to 20thNight
34%46%16%23%17%
2470
21st to endNight
36%35%14%21%20%
2454
February1st to 10thNight
37%46%13%22%18%
2160
11th to 20thNight
36%47%17%19%17%
2098
21st to endNight
39%47%13%19%18%
1776
March1st to 10thNight
39%5%9%15%21%11%
2039
11th to 20thNight
39%5%9%13%18%17%
1980
21st to endNight
33%6%11%17%18%15%
2178
April1st to 10thNight
34%6%10%19%17%14%
1980
11th to 20thNight
38%5%8%14%18%16%
1894
21st to endNight
37%5%8%20%20%10%
1692
May1st to 10thNight
34%7%11%20%18%10%
1620
11th to 20thNight
34%7%13%24%17%5%
1594
21st to endNight
34%8%15%27%14%2
1746
June1st to 10thNight
20%8%15%32%21%3
1620
11th to 20thNight
20%6%15%31%23%5%
1620
21st to endNight
25%8%17%29%17%4
1620
July1st to 10thNight
28%11%21%28%10%1
1575
11th to 20thNight
16%8%20%32%21%2
1566
21st to endNight
16%8%27%36%12%1
1673
August1st to 10thNight
12%6%21%41%20%1
1648
11th to 20thNight
23%10%21%29%13%3
1778
21st to endNight
27%9%21%27%12%3
2042
September1st to 10thNight
29%8%16%22%18%7%
1980
11th to 20thNight
35%9%14%22%15%5%
1980
21st to endNight
29%7%13%20%19%12%
1980
October1st to 10thNight
22%6%14%25%22%11%
1980
11th to 20thNight
31%6%9%15%21%19%
2052
21st to endNight
30%35%17%23%22%
2376
November1st to 10thNight
31%5%8%19%23%13%
2220
11th to 20thNight
29%49%21%20%17%
2451
21st to endNight
38%48%15%20%15%
2470
December1st to 10thNight
32%5%8%20%22%13%
2470
11th to 20thNight
40%45%12%21%19%
3037
21st to endNight
34%35%14%29%15%
4532

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
19%15%41%20%41
270
11th to 20thDay
20%14%36%22%6%1
270
21st to endDay
15%18%42%19%41
267
February1st to 10thDay
23%15%34%25%3
240
11th to 20thDay
25%22%37%15%2
240
21st to endDay
27%24%33%16%1
198
March1st to 10thDay
18%20%39%20%2
240
11th to 20thDay
18%19%35%23%5%
240
21st to endDay
17%17%45%16%4
264
April1st to 10thDay
18%21%41%16%4
240
11th to 20thDay
19%21%35%21%4
289
21st to endDay
17%15%40%22%6%
526
May1st to 10thDay
12%15%41%25%6%
603
11th to 20thDay
18%10%29%32%10%2
625
21st to endDay
16%5%28%35%15%1
679
June1st to 10thDay
6%319%43%25%4
630
11th to 20thDay
7%219%49%19%4
630
21st to endDay
7%215%41%28%7%
630
July1st to 10thDay
8%213%36%32%9%
621
11th to 20thDay
47%41%41%7%
618
21st to endDay
217%38%41%11%
684
August1st to 10thDay
2443%40%11%
573
11th to 20thDay
6%7%37%37%12%
437
21st to endDay
416%29%43%17%
433
September1st to 10thDay
10%9%23%38%20%
270
11th to 20thDay
6%15%30%45%13%
270
21st to endDay
11%17%31%37%13%
270
October1st to 10thDay
7%14%39%30%9%
270
11th to 20thDay
11%5%26%35%19%4
270
21st to endDay
18%16%26%26%13%1
297
November1st to 10thDay
19%5%29%34%9%4
270
11th to 20thDay
19%10%31%27%11%3
270
21st to endDay
22%19%32%18%7%2
270
December1st to 10thDay
16%11%32%30%8%3
270
11th to 20thDay
17%20%34%23%6%
270
21st to endDay
15%14%39%26%41
297
January1st to 10thNight
16%11%35%31%7%
950
11th to 20thNight
17%12%35%31%5%
950
21st to endNight
17%12%34%30%7%
854
February1st to 10thNight
18%13%38%27%5%
720
11th to 20thNight
19%13%41%24%2
704
21st to endNight
20%16%45%18%1
592
March1st to 10thNight
17%14%38%28%2
599
11th to 20thNight
18%10%37%32%4
540
21st to endNight
13%14%44%24%4
594
April1st to 10thNight
9%14%47%27%3
540
11th to 20thNight
14%14%42%27%2
533
21st to endNight
15%12%45%22%6%
540
May1st to 10thNight
10%14%43%29%4
540
11th to 20thNight
11%8%38%33%11%1
531
21st to endNight
12%6%34%37%11%1
584
June1st to 10thNight
3225%48%21%1
540
11th to 20thNight
4233%46%14%1
540
21st to endNight
5%219%50%21%3
540
July1st to 10thNight
8%311%50%25%2
525
11th to 20thNight
412%52%29%2
522
21st to endNight
2111%54%28%3
591
August1st to 10thNight
118%57%30%3
537
11th to 20thNight
6%16%51%32%4
534
21st to endNight
5%17%44%37%5%
594
September1st to 10thNight
8%9%44%32%6%
540
11th to 20thNight
10%110%39%35%4
540
21st to endNight
9%115%42%31%2
540
October1st to 10thNight
6%116%47%26%3
540
11th to 20thNight
12%5%23%42%16%2
612
21st to endNight
14%9%29%27%19%2
792
November1st to 10thNight
11%6%25%40%17%1
740
11th to 20thNight
11%9%28%36%15%1
931
21st to endNight
17%10%34%29%10%1
950
December1st to 10thNight
16%9%30%36%8%1
950
11th to 20thNight
19%11%33%32%6%
950
21st to endNight
16%11%35%30%7%
1045
Page generated at 2024-01-19 08:28:36. Version ac07

Copyright 2024 Attilla Danko


Lyndon B. Johnson State Park & Historic Site Clear Sky Chart |Charts Home