Space Center Houston
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Space Center Houston 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
57%
23630
22%
74246
18%
23577
61%
23577
29%
45228

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
41%
949
23%
2458
11%
946
47%
946
29%
1647
January11th to 20thNight
40%
908
22%
2360
10%
908
46%
908
30%
1568
January21st to endNight
38%
990
24%
2574
10%
990
45%
990
27%
1748
February1st to 10thNight
35%
846
19%
2286
8%
846
41%
846
24%
1598
February11th to 20thNight
37%
654
18%
2048
12%
650
42%
650
23%
1367
February21st to endNight
29%
444
21%
1628
14%
444
37%
444
16%
1088
March1st to 10thNight
41%
540
22%
1980
15%
540
49%
540
21%
1246
March11th to 20thNight
43%
540
18%
1980
15%
540
48%
540
20%
1260
March21st to endNight
50%
594
23%
2178
21%
594
56%
594
27%
1265
April1st to 10thNight
46%
540
21%
1980
19%
540
53%
540
21%
1253
April11th to 20thNight
44%
533
22%
1799
17%
533
52%
533
24%
1125
April21st to endNight
49%
540
23%
1800
22%
540
56%
540
25%
1108
May1st to 10thNight
55%
540
20%
1800
21%
540
59%
540
25%
1116
May11th to 20thNight
65%
531
23%
1602
25%
531
67%
531
33%
956
May21st to endNight
70%
582
20%
1746
24%
582
71%
582
32%
1047
June1st to 10thNight
82%
540
21%
1620
26%
540
82%
540
43%
861
June11th to 20thNight
85%
540
20%
1620
25%
540
85%
540
42%
885
June21st to endNight
77%
540
16%
1620
19%
540
77%
540
31%
1011
July1st to 10thNight
74%
525
14%
1575
18%
525
74%
525
30%
979
July11th to 20thNight
86%
522
19%
1566
24%
522
86%
522
40%
875
July21st to endNight
85%
591
17%
1673
21%
558
86%
558
39%
934
August1st to 10thNight
92%
537
23%
1601
26%
534
92%
534
53%
775
August11th to 20thNight
85%
534
21%
1718
24%
534
85%
534
38%
943
August21st to endNight
79%
594
17%
1984
20%
594
79%
594
29%
1172
September1st to 10thNight
80%
540
15%
1980
18%
540
81%
540
29%
1125
September11th to 20thNight
69%
540
20%
1980
24%
540
69%
540
22%
1240
September21st to endNight
73%
540
26%
1980
30%
540
73%
540
31%
1075
October1st to 10thNight
77%
646
31%
2086
29%
646
78%
646
40%
1088
October11th to 20thNight
68%
720
32%
2160
25%
720
72%
720
42%
1171
October21st to endNight
61%
792
33%
2376
25%
792
66%
792
39%
1321
November1st to 10thNight
67%
740
27%
2220
23%
740
69%
740
37%
1267
November11th to 20thNight
56%
760
28%
2280
21%
760
61%
760
32%
1375
November21st to endNight
47%
764
27%
2284
19%
764
54%
764
28%
1455
December1st to 10thNight
45%
950
24%
2470
14%
950
50%
950
27%
1683
December11th to 20thNight
40%
948
22%
2881
11%
948
45%
948
22%
1917
December21st to endNight
38%
1036
13%
4353
10%
1026
43%
1026
16%
2684

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%6%36%6%46%6%6%9%39%
74950
Night
12%6%25%43445%8%47%
74786
TransparencyDay
39%9%14%19%14%6%
74675
Night
35%8%14%20%16%8%
74581
SeeingDay
12%414%26%29%15%
13673
Night
14%417%30%28%6%
23644

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%6%36%4345%46%42%
1707
11th to 20thDay
17%8%35%424346%44%
1629
21st to endDay
19%7%35%5%24446%40%
1782
February1st to 10thDay
20%10%46%5%345%45%34%
1689
11th to 20thDay
21%10%45%5%34446%35%
1798
21st to endDay
20%9%35%6%35%45%5%36%
1628
March1st to 10thDay
19%8%46%5%45%35%6%35%
1980
11th to 20thDay
16%7%46%5%3445%6%39%
1980
21st to endDay
16%6%35%4245%5%8%43%
2178
April1st to 10thDay
14%8%37%445%45%8%37%
1980
11th to 20thDay
16%8%45%5%35%448%38%
2107
21st to endDay
10%6%36%5%36%5%6%7%43%
2160
May1st to 10thDay
9%7%37%7%46%5%5%7%40%
2160
11th to 20thDay
9%6%26%6%36%6%7%8%40%
2289
21st to endDay
8%6%36%7%5%8%8%9%11%29%
2531
June1st to 10thDay
6%5%25%5%46%7%8%11%41%
2340
11th to 20thDay
5%425%6%49%8%8%12%37%
2340
21st to endDay
7%436%7%6%9%10%10%10%28%
2340
July1st to 10thDay
9%6%35%6%48%8%10%13%28%
2340
11th to 20thDay
5%436%7%5%8%8%9%13%34%
2340
21st to endDay
5%336%6%48%7%10%12%35%
2546
August1st to 10thDay
33245%47%8%10%14%40%
2328
11th to 20thDay
4325%7%5%7%10%9%13%35%
2181
21st to endDay
9%5%26%7%5%7%6%9%12%32%
2368
September1st to 10thDay
6%5%27%7%5%6%8%7%11%34%
1980
11th to 20thDay
15%6%36%6%47%7%7%7%33%
1980
21st to endDay
9%5%35%5%45%5%7%8%45%
1980
October1st to 10thDay
7%4344245%6%7%53%
1854
11th to 20thDay
11%5%24425%5%6%7%50%
1800
21st to endDay
12%425%423447%54%
1980
November1st to 10thDay
10%5%245%35%6%5%7%47%
1858
11th to 20thDay
13%5%25%6%35%46%6%46%
1900
21st to endDay
16%7%26%6%34446%41%
1891
December1st to 10thDay
15%7%25%5%35%46%7%41%
1710
11th to 20thDay
13%7%36%5%45%46%7%40%
2161
21st to endDay
16%7%244345%5%6%43%
3135
January1st to 10thNight
18%8%25%42345%6%43%
2458
11th to 20thNight
19%6%36%32334447%
2360
21st to endNight
18%7%35%5%23445%42%
2574
February1st to 10thNight
18%9%46%434346%38%
2286
11th to 20thNight
20%9%26%433345%42%
2048
21st to endNight
21%9%35%5%24445%38%
1628
March1st to 10thNight
19%8%25%42345%7%40%
1980
11th to 20thNight
15%8%36%5%2445%7%40%
1980
21st to endNight
14%6%24423446%49%
2178
April1st to 10thNight
14%7%36%5%345%5%8%39%
1980
11th to 20thNight
18%6%244245%5%7%43%
1799
21st to endNight
11%6%36%6%45%5%5%7%43%
1800
May1st to 10thNight
11%6%25%5%36%6%6%9%41%
1800
11th to 20thNight
10%5%15%345%6%6%8%48%
1601
21st to endNight
5%435%5%46%6%8%11%43%
1745
June1st to 10thNight
5%31343447%11%56%
1620
11th to 20thNight
4323325%6%7%11%53%
1620
21st to endNight
5%425%5%46%7%7%12%42%
1620
July1st to 10thNight
6%5%345%25%6%7%13%42%
1620
11th to 20thNight
2214435%5%8%12%55%
1620
21st to endNight
3324435%5%8%12%52%
1772
August1st to 10thNight
111222445%12%66%
1611
11th to 20thNight
431343449%14%51%
1718
21st to endNight
5%325%5%35%6%8%12%46%
1984
September1st to 10thNight
4426%5%446%8%12%46%
1980
11th to 20thNight
11%7%35%5%335%6%9%43%
1980
21st to endNight
8%425%43446%8%53%
1980
October1st to 10thNight
5%415%42435%7%60%
2086
11th to 20thNight
9%42332345%7%59%
2160
21st to endNight
10%424323335%60%
2376
November1st to 10thNight
9%5%25%324446%56%
2220
11th to 20thNight
12%5%25%425%5%5%6%50%
2280
21st to endNight
15%7%36%5%34346%45%
2284
December1st to 10thNight
17%7%35%434347%42%
2470
11th to 20thNight
14%9%26%5%4445%6%42%
3036
21st to endNight
16%7%26%5%34445%44%
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
44%6%6%16%20%8%
1708
11th to 20thDay
42%5%6%17%18%11%
1629
21st to endDay
46%46%16%15%13%
1782
February1st to 10thDay
52%5%7%12%14%10%
1689
11th to 20thDay
50%7%7%12%16%8%
1808
21st to endDay
50%7%9%11%14%9%
1628
March1st to 10thDay
49%7%10%14%16%5%
1980
11th to 20thDay
45%7%9%12%19%8%
1980
21st to endDay
39%8%11%15%21%6%
2178
April1st to 10thDay
46%7%10%16%14%7%
1980
11th to 20thDay
44%6%11%16%15%8%
2107
21st to endDay
37%8%11%19%20%6%
2160
May1st to 10thDay
40%8%13%16%16%7%
2160
11th to 20thDay
37%10%12%22%16%3
2293
21st to endDay
41%11%16%21%11%1
2531
June1st to 10thDay
32%9%19%25%14%1
2340
11th to 20thDay
34%9%18%25%12%1
2340
21st to endDay
41%13%19%19%7%
2340
July1st to 10thDay
37%12%24%21%5%
2276
11th to 20thDay
34%14%27%21%5%
2271
21st to endDay
32%15%23%25%41
2405
August1st to 10thDay
26%13%25%28%8%
2314
11th to 20thDay
31%16%22%24%6%1
2181
21st to endDay
39%14%21%19%7%2
2368
September1st to 10thDay
38%14%16%17%12%3
1980
11th to 20thDay
44%10%14%17%12%3
1980
21st to endDay
35%8%13%20%15%8%
1980
October1st to 10thDay
28%6%11%24%18%11%
1854
11th to 20thDay
31%6%9%21%21%13%
1800
21st to endDay
31%5%7%19%22%16%
1980
November1st to 10thDay
33%7%11%21%20%8%
1858
11th to 20thDay
37%7%11%14%20%11%
1900
21st to endDay
44%5%9%16%17%9%
1891
December1st to 10thDay
41%8%10%20%15%7%
1710
11th to 20thDay
40%7%11%13%19%9%
2159
21st to endDay
41%7%8%15%19%11%
3135
January1st to 10thNight
42%5%8%14%20%11%
2458
11th to 20thNight
41%47%15%20%12%
2360
21st to endNight
44%5%7%15%17%13%
2574
February1st to 10thNight
47%5%9%10%17%11%
2286
11th to 20thNight
45%5%8%12%17%12%
2048
21st to endNight
49%6%7%12%16%10%
1628
March1st to 10thNight
43%6%10%17%16%8%
1980
11th to 20thNight
43%7%12%12%18%8%
1980
21st to endNight
35%7%12%17%20%9%
2178
April1st to 10thNight
42%8%11%17%15%9%
1980
11th to 20thNight
39%7%10%16%15%12%
1799
21st to endNight
39%6%11%20%17%7%
1800
May1st to 10thNight
37%10%12%18%15%8%
1800
11th to 20thNight
32%8%13%24%20%4
1602
21st to endNight
30%10%21%26%11%1
1746
June1st to 10thNight
22%8%22%30%18%
1620
11th to 20thNight
24%8%19%31%17%1
1620
21st to endNight
32%10%23%25%9%
1620
July1st to 10thNight
33%11%26%26%5%
1575
11th to 20thNight
21%12%31%29%6%
1566
21st to endNight
22%12%30%31%5%
1673
August1st to 10thNight
12%10%31%39%7%
1601
11th to 20thNight
21%13%29%30%6%1
1718
21st to endNight
29%13%23%27%7%2
1984
September1st to 10thNight
28%12%24%20%13%3
1980
11th to 20thNight
37%11%13%20%15%3
1980
21st to endNight
29%8%15%21%20%7%
1980
October1st to 10thNight
24%7%10%28%19%12%
2086
11th to 20thNight
25%6%11%24%22%13%
2160
21st to endNight
29%48%16%24%18%
2376
November1st to 10thNight
30%6%12%22%21%9%
2220
11th to 20thNight
34%6%10%20%19%10%
2280
21st to endNight
41%49%20%18%8%
2284
December1st to 10thNight
43%6%10%19%14%8%
2470
11th to 20thNight
42%6%8%12%18%14%
3037
21st to endNight
42%7%8%13%23%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
23%6%27%32%11%1
270
11th to 20thDay
17%8%29%34%10%1
243
21st to endDay
20%10%31%32%6%
264
February1st to 10thDay
25%9%28%25%12%
240
11th to 20thDay
28%10%24%30%8%1
240
21st to endDay
25%9%37%27%2
198
March1st to 10thDay
24%8%30%29%10%
240
11th to 20thDay
17%9%38%28%5%3
240
21st to endDay
16%11%29%33%10%2
264
April1st to 10thDay
18%8%31%30%13%
240
11th to 20thDay
21%11%24%25%16%2
385
21st to endDay
14%5%25%34%19%2
420
May1st to 10thDay
13%424%37%20%2
423
11th to 20thDay
11%217%39%26%4
612
21st to endDay
8%315%41%28%5%
679
June1st to 10thDay
8%16%33%39%14%
630
11th to 20thDay
5%16%34%37%17%
630
21st to endDay
10%7%19%44%20%
630
July1st to 10thDay
7%2417%45%26%
621
11th to 20thDay
5%311%46%35%
618
21st to endDay
41215%47%32%
684
August1st to 10thDay
3212%47%36%
626
11th to 20thDay
339%42%43%
495
21st to endDay
11%25%10%34%38%
487
September1st to 10thDay
10%1414%40%31%
270
11th to 20thDay
12%1216%45%24%
270
21st to endDay
11%16%16%42%24%
270
October1st to 10thDay
8%431%44%13%
270
11th to 20thDay
12%210%26%37%13%
270
21st to endDay
18%8%17%28%26%3
297
November1st to 10thDay
13%413%33%31%5%
270
11th to 20thDay
17%5%18%32%21%6%
270
21st to endDay
16%10%29%29%13%3
270
December1st to 10thDay
21%6%17%35%14%7%
270
11th to 20thDay
19%11%28%30%10%2
270
21st to endDay
19%7%24%32%15%3
297
January1st to 10thNight
22%6%27%34%11%
950
11th to 20thNight
22%6%25%36%11%
908
21st to endNight
20%8%28%35%9%
990
February1st to 10thNight
23%7%28%33%8%
846
11th to 20thNight
24%8%26%31%10%
654
21st to endNight
24%11%30%29%6%
444
March1st to 10thNight
22%7%26%33%12%
540
11th to 20thNight
18%8%24%38%11%1
540
21st to endNight
16%6%25%37%15%2
594
April1st to 10thNight
16%7%25%41%11%
540
11th to 20thNight
19%6%23%35%17%
533
21st to endNight
14%5%26%38%17%1
540
May1st to 10thNight
13%421%49%14%
540
11th to 20thNight
11%315%44%24%2
531
21st to endNight
5%312%39%37%4
584
June1st to 10thNight
7%5%31%50%6%
540
11th to 20thNight
6%1333%52%7%
540
21st to endNight
6%1421%54%14%
540
July1st to 10thNight
7%2415%54%18%
525
11th to 20thNight
3111%61%24%
522
21st to endNight
41213%61%21%
591
August1st to 10thNight
1119%65%23%
537
11th to 20thNight
5%110%62%22%
534
21st to endNight
6%1314%52%24%
594
September1st to 10thNight
5%1314%54%23%
540
11th to 20thNight
16%1418%48%15%
540
21st to endNight
11%18%21%49%11%
540
October1st to 10thNight
7%26%28%47%10%
646
11th to 20thNight
10%214%33%36%5%
720
21st to endNight
12%5%15%36%28%4
792
November1st to 10thNight
11%312%36%32%5%
740
11th to 20thNight
14%5%20%37%24%2
760
21st to endNight
17%5%25%34%16%2
764
December1st to 10thNight
19%7%22%31%19%2
950
11th to 20thNight
21%8%24%35%12%
950
21st to endNight
21%7%24%35%12%1
1045
Page generated at 2024-01-09 06:14:40. Version ac07

Copyright 2024 Attilla Danko


Space Center Houston Clear Sky Chart |Charts Home