Galveston Island State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Galveston Island State Park clear sky chart from 2005-11-06 to 2024-01-12.

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
58%
23586
22%
74248
18%
23532
61%
23532
29%
45248

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
40%
947
22%
2458
10%
946
46%
946
27%
1680
January11th to 20thNight
42%
908
21%
2360
9%
908
48%
908
29%
1579
January21st to endNight
38%
990
23%
2574
10%
990
44%
990
26%
1757
February1st to 10thNight
37%
846
19%
2286
9%
846
43%
846
24%
1601
February11th to 20thNight
40%
636
19%
2030
12%
632
45%
632
24%
1315
February21st to endNight
35%
444
20%
1628
13%
444
43%
444
18%
1073
March1st to 10thNight
42%
540
22%
1980
17%
540
50%
540
22%
1214
March11th to 20thNight
44%
540
19%
1980
16%
540
49%
540
20%
1253
March21st to endNight
53%
594
23%
2178
21%
594
59%
594
28%
1228
April1st to 10thNight
47%
540
22%
1980
20%
540
54%
540
22%
1209
April11th to 20thNight
46%
533
21%
1794
17%
533
54%
533
26%
1085
April21st to endNight
51%
540
22%
1800
22%
540
56%
540
26%
1099
May1st to 10thNight
55%
540
20%
1800
21%
540
59%
540
27%
1073
May11th to 20thNight
65%
531
23%
1635
26%
531
67%
531
36%
939
May21st to endNight
70%
583
23%
1745
25%
582
72%
582
36%
998
June1st to 10thNight
82%
540
23%
1620
27%
540
82%
540
44%
856
June11th to 20thNight
81%
540
20%
1620
23%
540
81%
540
41%
883
June21st to endNight
74%
540
15%
1620
19%
540
74%
540
29%
1021
July1st to 10thNight
73%
525
14%
1575
17%
525
74%
525
29%
981
July11th to 20thNight
84%
522
18%
1566
23%
522
84%
522
39%
877
July21st to endNight
83%
591
17%
1673
20%
558
84%
558
38%
948
August1st to 10thNight
90%
537
23%
1601
25%
534
91%
534
49%
809
August11th to 20thNight
83%
534
21%
1737
25%
534
83%
534
36%
954
August21st to endNight
79%
594
17%
1980
19%
594
79%
594
29%
1170
September1st to 10thNight
75%
540
14%
1974
17%
540
75%
540
26%
1172
September11th to 20thNight
65%
540
18%
1980
21%
540
65%
540
21%
1277
September21st to endNight
72%
540
26%
1980
30%
540
72%
540
30%
1106
October1st to 10thNight
78%
652
30%
2092
28%
652
79%
652
41%
1104
October11th to 20thNight
69%
720
32%
2160
26%
720
73%
720
42%
1176
October21st to endNight
62%
792
32%
2376
24%
792
67%
792
39%
1326
November1st to 10thNight
66%
740
26%
2220
21%
740
68%
740
36%
1275
November11th to 20thNight
55%
760
27%
2280
21%
760
60%
760
32%
1381
November21st to endNight
50%
760
26%
2280
18%
760
56%
760
27%
1485
December1st to 10thNight
48%
921
24%
2441
15%
921
52%
921
27%
1663
December11th to 20thNight
42%
948
21%
2882
11%
948
46%
948
22%
1945
December21st to endNight
38%
1038
13%
4363
10%
1026
43%
1026
16%
2736

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
12%5%25%5%35%5%6%9%43%
74957
Night
12%5%25%4345%5%8%46%
74778
TransparencyDay
36%9%16%20%14%5%
74682
Night
35%8%14%21%16%7%
74573
SeeingDay
12%315%27%29%14%
13633
Night
14%415%30%29%8%
23599

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
18%7%35%5%35%447%38%
1707
11th to 20thDay
18%6%35%5%2435%8%42%
1629
21st to endDay
19%7%35%5%24446%40%
1782
February1st to 10thDay
21%9%35%5%24445%36%
1688
11th to 20thDay
22%10%445%23435%37%
1817
21st to endDay
23%8%36%434345%37%
1628
March1st to 10thDay
19%7%36%5%24446%39%
1980
11th to 20thDay
17%7%36%5%2335%6%42%
1980
21st to endDay
14%6%25%42445%6%48%
2178
April1st to 10thDay
17%7%36%5%2445%8%39%
1980
11th to 20thDay
14%6%35%6%35%45%8%40%
2112
21st to endDay
10%6%25%5%3445%7%48%
2160
May1st to 10thDay
9%6%25%5%35%5%6%10%43%
2160
11th to 20thDay
9%5%25%5%45%5%7%10%43%
2256
21st to endDay
7%5%245%5%6%6%9%12%39%
2531
June1st to 10thDay
5%423435%6%8%11%48%
2340
11th to 20thDay
5%323435%7%9%14%44%
2340
21st to endDay
8%425%5%46%7%9%13%37%
2340
July1st to 10thDay
10%425%5%35%7%8%13%38%
2340
11th to 20thDay
5%4345%35%6%8%14%43%
2340
21st to endDay
44246%46%6%8%13%43%
2546
August1st to 10thDay
3213435%6%9%13%52%
2328
11th to 20thDay
5%324445%7%11%15%41%
2161
21st to endDay
10%425%5%46%6%7%12%39%
2376
September1st to 10thDay
9%425%6%46%7%7%11%39%
1980
11th to 20thDay
14%6%35%6%45%6%6%9%36%
1980
21st to endDay
9%6%26%5%3446%7%48%
1980
October1st to 10thDay
6%42442446%9%55%
1850
11th to 20thDay
10%5%2343445%7%53%
1800
21st to endDay
12%424424345%56%
1980
November1st to 10thDay
10%5%25%42446%7%50%
1858
11th to 20thDay
14%5%245%345%47%48%
1900
21st to endDay
16%6%35%5%3445%7%42%
1900
December1st to 10thDay
18%5%35%4335%47%43%
1734
11th to 20thDay
14%7%25%5%345%5%8%40%
2161
21st to endDay
17%6%25%5%3445%7%41%
3135
January1st to 10thNight
18%6%35%5%3445%6%41%
2458
11th to 20thNight
18%8%35%433445%45%
2360
21st to endNight
19%7%45%42445%5%41%
2574
February1st to 10thNight
19%10%35%434446%38%
2286
11th to 20thNight
21%9%34323337%43%
2030
21st to endNight
22%8%35%433445%38%
1628
March1st to 10thNight
17%8%2442445%7%43%
1980
11th to 20thNight
15%7%35%5%4446%6%41%
1980
21st to endNight
12%6%1442445%7%50%
2178
April1st to 10thNight
14%6%35%6%345%5%9%41%
1980
11th to 20thNight
14%6%25%42445%8%45%
1794
21st to endNight
11%6%36%5%35%45%8%45%
1800
May1st to 10thNight
10%6%25%4345%7%8%45%
1800
11th to 20thNight
8%424435%46%9%51%
1634
21st to endNight
6%425%4345%7%12%47%
1745
June1st to 10thNight
441443446%10%57%
1620
11th to 20thNight
5%3244346%8%12%50%
1620
21st to endNight
5%425%6%5%6%7%7%13%39%
1620
July1st to 10thNight
6%436%6%46%6%8%12%39%
1620
11th to 20thNight
22245%35%5%7%14%51%
1620
21st to endNight
4224425%6%8%14%50%
1772
August1st to 10thNight
111243346%11%63%
1611
11th to 20thNight
43244245%7%14%51%
1737
21st to endNight
7%4245%25%6%8%13%46%
1980
September1st to 10thNight
7%425%5%46%6%7%11%44%
1974
11th to 20thNight
13%6%35%6%35%5%6%8%40%
1980
21st to endNight
9%4245%345%6%8%51%
1980
October1st to 10thNight
6%32442445%8%57%
2092
11th to 20thNight
10%31432335%6%58%
2160
21st to endNight
10%5%2342345%5%58%
2376
November1st to 10thNight
9%5%245%3345%6%54%
2220
11th to 20thNight
14%5%245%3435%6%50%
2280
21st to endNight
15%6%35%5%345%46%43%
2280
December1st to 10thNight
19%6%35%5%23447%42%
2441
11th to 20thNight
16%7%25%435%5%5%7%41%
3036
21st to endNight
16%7%36%5%34446%42%
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
46%6%8%16%17%7%
1708
11th to 20thDay
40%6%8%17%18%10%
1629
21st to endDay
46%47%17%15%11%
1782
February1st to 10thDay
49%6%8%15%13%10%
1688
11th to 20thDay
50%5%10%13%16%7%
1827
21st to endDay
49%7%10%13%13%8%
1628
March1st to 10thDay
46%8%11%15%16%4
1980
11th to 20thDay
44%6%12%13%18%8%
1980
21st to endDay
36%8%15%16%20%6%
2178
April1st to 10thDay
42%8%12%17%14%7%
1980
11th to 20thDay
41%8%13%17%14%8%
2112
21st to endDay
34%8%14%21%19%5%
2160
May1st to 10thDay
34%10%15%20%15%6%
2160
11th to 20thDay
33%10%15%23%16%3
2260
21st to endDay
32%13%18%25%11%1
2531
June1st to 10thDay
25%11%21%29%14%
2340
11th to 20thDay
26%12%20%29%12%1
2340
21st to endDay
34%14%21%24%5%
2340
July1st to 10thDay
33%13%26%24%4
2276
11th to 20thDay
28%14%30%23%5%
2271
21st to endDay
29%14%28%25%4
2405
August1st to 10thDay
20%12%30%30%7%
2314
11th to 20thDay
27%16%28%25%4
2161
21st to endDay
36%14%22%21%6%2
2376
September1st to 10thDay
34%16%18%17%11%3
1980
11th to 20thDay
42%12%13%18%13%2
1980
21st to endDay
34%8%16%20%15%7%
1980
October1st to 10thDay
26%7%13%27%19%9%
1850
11th to 20thDay
29%6%11%22%20%11%
1800
21st to endDay
30%5%8%20%23%14%
1980
November1st to 10thDay
31%8%12%21%22%6%
1858
11th to 20thDay
36%7%13%16%19%10%
1900
21st to endDay
42%6%9%18%16%8%
1900
December1st to 10thDay
40%8%12%20%14%5%
1734
11th to 20thDay
41%8%11%14%18%9%
2159
21st to endDay
41%8%9%15%17%10%
3135
January1st to 10thNight
43%6%8%14%19%10%
2458
11th to 20thNight
42%48%15%19%12%
2360
21st to endNight
45%47%15%17%11%
2574
February1st to 10thNight
47%6%9%10%18%11%
2286
11th to 20thNight
43%5%9%15%17%11%
2030
21st to endNight
47%6%10%12%15%9%
1628
March1st to 10thNight
40%6%11%20%15%7%
1980
11th to 20thNight
42%8%13%13%16%8%
1980
21st to endNight
34%6%13%19%20%8%
2178
April1st to 10thNight
40%7%11%19%15%8%
1980
11th to 20thNight
36%8%13%19%14%11%
1794
21st to endNight
37%7%12%21%16%7%
1800
May1st to 10thNight
34%9%14%20%15%8%
1800
11th to 20thNight
29%7%14%27%19%3
1635
21st to endNight
28%8%22%27%14%1
1746
June1st to 10thNight
23%7%20%33%18%
1620
11th to 20thNight
24%8%19%32%15%2
1620
21st to endNight
33%11%23%24%9%
1620
July1st to 10thNight
33%11%26%25%5%
1575
11th to 20thNight
22%12%32%28%7%
1566
21st to endNight
23%12%29%32%4
1673
August1st to 10thNight
15%10%28%39%7%
1601
11th to 20thNight
23%12%29%30%6%
1737
21st to endNight
28%14%25%26%7%1
1980
September1st to 10thNight
31%12%22%19%12%3
1974
11th to 20thNight
41%10%14%19%13%2
1980
21st to endNight
31%8%15%22%19%6%
1980
October1st to 10thNight
25%6%12%28%18%11%
2092
11th to 20thNight
25%6%11%25%21%11%
2160
21st to endNight
28%5%10%16%24%17%
2376
November1st to 10thNight
30%6%13%23%20%8%
2220
11th to 20thNight
35%6%11%21%18%9%
2280
21st to endNight
40%7%10%20%17%7%
2280
December1st to 10thNight
42%6%10%20%14%7%
2441
11th to 20thNight
42%7%9%14%15%13%
3037
21st to endNight
43%7%8%14%21%8%
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
24%7%32%26%10%1
270
11th to 20thDay
19%7%26%36%12%1
243
21st to endDay
19%8%38%28%8%
264
February1st to 10thDay
27%8%28%27%10%1
240
11th to 20thDay
25%7%33%27%8%1
240
21st to endDay
23%7%43%24%21
198
March1st to 10thDay
20%338%33%7%1
240
11th to 20thDay
19%7%42%22%8%2
240
21st to endDay
15%5%39%32%8%
264
April1st to 10thDay
15%10%36%28%9%1
240
11th to 20thDay
20%8%29%25%16%2
390
21st to endDay
13%428%36%17%1
420
May1st to 10thDay
14%5%25%36%19%2
423
11th to 20thDay
11%217%42%23%4
579
21st to endDay
7%214%43%29%5%
679
June1st to 10thDay
6%15%36%38%14%
630
11th to 20thDay
8%16%32%39%13%
630
21st to endDay
9%35%23%39%20%
630
July1st to 10thDay
8%3120%45%24%
621
11th to 20thDay
5%1216%44%33%
618
21st to endDay
5%2115%49%28%
684
August1st to 10thDay
21113%50%33%
626
11th to 20thDay
5%117%46%41%
475
21st to endDay
12%3111%35%38%
495
September1st to 10thDay
11%1213%38%34%
270
11th to 20thDay
11%217%41%28%
270
21st to endDay
11%2316%45%23%
270
October1st to 10thDay
7%1334%39%15%
270
11th to 20thDay
11%29%32%31%15%
270
21st to endDay
15%5%22%28%24%6%
297
November1st to 10thDay
14%113%36%28%7%
270
11th to 20thDay
17%218%39%19%5%
270
21st to endDay
20%6%28%31%13%2
270
December1st to 10thDay
20%5%20%30%17%8%
270
11th to 20thDay
22%8%26%33%10%1
270
21st to endDay
21%430%28%14%3
297
January1st to 10thNight
22%6%24%33%14%1
950
11th to 20thNight
20%6%24%38%12%
908
21st to endNight
22%7%26%34%11%
990
February1st to 10thNight
25%6%25%34%10%
846
11th to 20thNight
24%7%23%34%12%
636
21st to endNight
26%9%24%33%8%
444
March1st to 10thNight
20%6%25%34%13%1
540
11th to 20thNight
17%8%22%37%16%1
540
21st to endNight
14%423%39%17%2
594
April1st to 10thNight
16%7%23%39%14%
540
11th to 20thNight
17%5%23%36%18%
533
21st to endNight
13%423%41%18%1
540
May1st to 10thNight
12%322%44%19%
540
11th to 20thNight
11%215%44%25%3
531
21st to endNight
7%29%40%38%5%
584
June1st to 10thNight
5%2331%51%8%
540
11th to 20thNight
5%1230%51%11%
540
21st to endNight
6%1319%51%19%
540
July1st to 10thNight
7%2213%50%26%
525
11th to 20thNight
219%52%36%
522
21st to endNight
32110%57%28%
591
August1st to 10thNight
217%60%30%
537
11th to 20thNight
5%115%56%32%
534
21st to endNight
8%2112%49%28%
594
September1st to 10thNight
7%1313%49%27%
540
11th to 20thNight
16%1317%43%20%
540
21st to endNight
10%15%20%49%15%
540
October1st to 10thNight
6%15%26%50%12%
652
11th to 20thNight
10%310%32%37%8%
720
21st to endNight
11%5%16%33%29%6%
792
November1st to 10thNight
11%211%34%34%7%
740
11th to 20thNight
16%317%36%27%1
760
21st to endNight
15%5%23%36%18%3
760
December1st to 10thNight
21%6%17%33%20%3
921
11th to 20thNight
20%6%21%37%15%1
950
21st to endNight
23%6%23%33%14%1
1045
Page generated at 2024-01-09 06:14:40. Version ac07

Copyright 2024 Attilla Danko


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