Sam Rayburn
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sam Rayburn clear sky chart from 2005-11-06 to 2024-02-10.

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
48%
23903
23%
79282
16%
23799
55%
23799
27%
47433

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
29%
944
28%
3977
9%
926
39%
926
19%
2256
January11th to 20thNight
30%
948
26%
3947
9%
930
39%
930
19%
2279
January21st to endNight
28%
1037
16%
4461
8%
1023
38%
1023
16%
2927
February1st to 10thNight
28%
948
22%
2464
7%
948
37%
948
26%
1674
February11th to 20thNight
25%
686
19%
2081
7%
682
35%
682
21%
1370
February21st to endNight
20%
444
23%
1628
10%
444
34%
444
16%
1065
March1st to 10thNight
30%
540
23%
1980
11%
540
43%
540
20%
1239
March11th to 20thNight
28%
540
20%
1980
12%
540
39%
540
19%
1259
March21st to endNight
34%
594
23%
2178
15%
594
45%
594
25%
1273
April1st to 10thNight
32%
540
23%
1927
15%
540
45%
540
23%
1168
April11th to 20thNight
35%
533
23%
1775
15%
533
47%
533
25%
1082
April21st to endNight
38%
540
24%
1800
18%
540
49%
540
28%
1059
May1st to 10thNight
37%
540
19%
1800
16%
540
45%
540
25%
1112
May11th to 20thNight
48%
531
24%
1628
23%
531
55%
531
33%
956
May21st to endNight
58%
584
23%
1745
19%
582
65%
582
36%
1015
June1st to 10thNight
71%
540
18%
1620
20%
540
74%
540
36%
939
June11th to 20thNight
72%
540
22%
1620
21%
540
78%
540
45%
859
June21st to endNight
71%
540
19%
1620
21%
540
73%
540
34%
966
July1st to 10thNight
76%
525
14%
1575
17%
525
76%
525
31%
972
July11th to 20thNight
79%
522
19%
1566
21%
522
81%
522
42%
866
July21st to endNight
79%
591
16%
1673
19%
558
81%
558
36%
977
August1st to 10thNight
85%
537
23%
1601
26%
534
86%
534
50%
805
August11th to 20thNight
82%
534
21%
1746
26%
534
83%
534
37%
958
August21st to endNight
73%
594
18%
1980
21%
594
73%
594
28%
1221
September1st to 10thNight
75%
540
21%
1828
23%
540
76%
540
32%
1059
September11th to 20thNight
67%
540
21%
1980
24%
540
69%
540
25%
1193
September21st to endNight
70%
540
30%
1980
33%
540
73%
540
35%
1032
October1st to 10thNight
72%
708
30%
2148
24%
708
74%
708
43%
1139
October11th to 20thNight
57%
720
34%
2160
22%
720
65%
720
38%
1201
October21st to endNight
49%
792
33%
2376
22%
792
57%
792
36%
1338
November1st to 10thNight
54%
740
28%
2220
20%
740
59%
740
37%
1256
November11th to 20thNight
47%
760
28%
2280
20%
760
55%
760
32%
1335
November21st to endNight
38%
760
27%
2280
16%
760
47%
760
28%
1421
December1st to 10thNight
37%
945
25%
2465
12%
945
44%
945
26%
1687
December11th to 20thNight
31%
948
24%
2869
10%
948
38%
948
21%
1897
December21st to endNight
31%
1038
14%
4324
9%
1026
37%
1026
17%
2578

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
13%6%35%5%35%5%5%8%42%
78782
Night
13%6%2442445%7%48%
80239
TransparencyDay
40%7%11%18%18%6%
78507
Night
36%6%12%19%19%8%
80034
SeeingDay
13%7%20%25%24%11%
13938
Night
15%7%24%32%19%3
23928

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
20%8%36%434346%39%
2847
11th to 20thDay
20%6%24322235%50%
2850
21st to endDay
23%9%35%423346%39%
3135
February1st to 10thDay
20%8%45%5%35%445%38%
1701
11th to 20thDay
22%9%35%32333441%
1779
21st to endDay
19%8%36%5%34446%37%
1628
March1st to 10thDay
21%8%37%5%24337%37%
1980
11th to 20thDay
17%8%35%5%35%447%40%
1980
21st to endDay
14%7%36%5%3445%6%43%
2178
April1st to 10thDay
12%8%46%6%45%5%47%40%
2030
11th to 20thDay
15%6%26%5%35%5%6%7%39%
2134
21st to endDay
11%5%35%5%36%46%7%45%
2160
May1st to 10thDay
12%6%36%6%36%5%6%7%39%
2160
11th to 20thDay
11%5%25%5%45%5%6%8%44%
2263
21st to endDay
9%5%36%7%48%8%7%9%34%
2531
June1st to 10thDay
7%425%7%47%7%7%10%39%
2340
11th to 20thDay
5%425%6%5%7%6%9%11%41%
2340
21st to endDay
8%5%36%6%5%7%7%8%10%34%
2340
July1st to 10thDay
10%436%7%5%7%7%8%10%31%
2340
11th to 20thDay
7%436%6%47%8%9%10%38%
2340
21st to endDay
6%436%7%47%8%8%10%38%
2546
August1st to 10thDay
43246%46%6%8%13%44%
2328
11th to 20thDay
6%425%6%46%6%7%12%42%
2154
21st to endDay
10%435%7%46%8%6%10%38%
2376
September1st to 10thDay
8%5%36%6%45%6%7%8%44%
2126
11th to 20thDay
13%6%36%5%46%6%6%8%39%
1980
21st to endDay
10%424435%5%6%7%51%
1972
October1st to 10thDay
8%3243345%46%59%
1800
11th to 20thDay
11%5%2442445%7%52%
1800
21st to endDay
15%5%24423436%52%
1980
November1st to 10thDay
10%6%24435%448%50%
1858
11th to 20thDay
12%5%25%5%34346%51%
1900
21st to endDay
16%7%26%5%34335%45%
1900
December1st to 10thDay
17%7%35%5%34445%43%
1710
11th to 20thDay
16%9%46%5%34445%41%
2161
21st to endDay
16%8%36%6%23346%42%
3135
January1st to 10thNight
16%8%34323436%48%
4108
11th to 20thNight
19%8%2432223450%
4120
21st to endNight
24%10%35%322345%39%
4532
February1st to 10thNight
17%9%34434446%42%
2464
11th to 20thNight
21%9%3442344443%
2081
21st to endNight
22%7%25%5%3444440%
1628
March1st to 10thNight
19%9%2442335%7%41%
1980
11th to 20thNight
16%8%35%5%3446%6%40%
1980
21st to endNight
13%8%34423446%48%
2178
April1st to 10thNight
13%6%35%5%35%45%9%44%
1927
11th to 20thNight
14%6%35%5%3445%7%45%
1775
21st to endNight
11%5%36%435%446%50%
1800
May1st to 10thNight
12%6%36%5%25%5%5%8%44%
1800
11th to 20thNight
11%5%25%433348%49%
1627
21st to endNight
7%4245%345%6%10%49%
1745
June1st to 10thNight
5%3245%35%5%7%9%51%
1620
11th to 20thNight
3223335%46%10%59%
1620
21st to endNight
6%5%24436%5%8%11%46%
1620
July1st to 10thNight
6%335%5%45%6%8%13%43%
1620
11th to 20thNight
43245%25%5%8%12%51%
1620
21st to endNight
3315%5%36%6%8%13%46%
1772
August1st to 10thNight
331231447%12%60%
1611
11th to 20thNight
4414435%7%9%12%48%
1746
21st to endNight
9%425%5%45%6%7%9%45%
1980
September1st to 10thNight
6%4246%345%7%10%49%
1828
11th to 20thNight
11%5%26%5%345%5%8%45%
1980
21st to endNight
8%4244245%5%7%55%
1980
October1st to 10thNight
5%32442445%7%60%
2148
11th to 20thNight
11%424323446%56%
2160
21st to endNight
13%5%1442233458%
2376
November1st to 10thNight
12%5%23423346%55%
2220
11th to 20thNight
11%5%245%24345%53%
2280
21st to endNight
16%7%2443435%7%45%
2280
December1st to 10thNight
19%9%34424445%42%
2465
11th to 20thNight
16%9%36%43434445%
3036
21st to endNight
17%9%34423446%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%5%5%18%22%6%
2848
11th to 20thDay
39%4418%30%6%
2850
21st to endDay
47%3417%19%10%
3135
February1st to 10thDay
50%5%6%13%18%9%
1701
11th to 20thDay
48%47%15%17%9%
1789
21st to endDay
49%6%7%12%16%11%
1628
March1st to 10thDay
50%48%12%17%8%
1980
11th to 20thDay
45%6%8%13%21%7%
1980
21st to endDay
42%5%8%16%23%6%
2178
April1st to 10thDay
44%7%7%17%17%7%
2030
11th to 20thDay
43%7%9%15%16%10%
2134
21st to endDay
38%7%9%18%23%5%
2160
May1st to 10thDay
43%6%10%19%15%6%
2160
11th to 20thDay
38%8%12%22%17%2
2267
21st to endDay
43%9%13%21%12%1
2531
June1st to 10thDay
38%10%16%21%14%1
2340
11th to 20thDay
34%11%15%24%14%2
2340
21st to endDay
41%11%17%19%11%2
2340
July1st to 10thDay
42%13%17%21%6%
2276
11th to 20thDay
37%11%19%24%9%
2271
21st to endDay
36%12%21%23%9%1
2405
August1st to 10thDay
29%10%21%29%11%1
2314
11th to 20thDay
33%12%21%23%9%1
2154
21st to endDay
40%11%18%20%9%2
2376
September1st to 10thDay
36%9%14%19%15%6%
2126
11th to 20thDay
43%7%12%16%15%6%
1980
21st to endDay
32%6%12%21%19%10%
1972
October1st to 10thDay
28%5%11%20%24%12%
1800
11th to 20thDay
31%6%7%17%25%13%
1800
21st to endDay
35%45%14%26%15%
1980
November1st to 10thDay
33%6%9%18%22%11%
1858
11th to 20thDay
36%47%16%25%11%
1900
21st to endDay
44%47%16%21%8%
1900
December1st to 10thDay
44%5%10%16%17%8%
1710
11th to 20thDay
46%5%7%14%21%8%
2159
21st to endDay
45%36%14%25%7%
3135
January1st to 10thNight
38%46%19%24%8%
4108
11th to 20thNight
39%45%18%26%8%
4120
21st to endNight
49%4417%17%10%
4532
February1st to 10thNight
45%36%16%18%12%
2464
11th to 20thNight
46%47%14%20%10%
2081
21st to endNight
48%5%7%12%14%14%
1628
March1st to 10thNight
44%5%9%14%18%11%
1980
11th to 20thNight
43%6%10%12%19%8%
1980
21st to endNight
38%5%11%16%24%7%
2178
April1st to 10thNight
39%6%10%19%17%9%
1927
11th to 20thNight
38%7%10%18%16%12%
1775
21st to endNight
36%5%10%18%25%6%
1800
May1st to 10thNight
39%7%13%16%18%7%
1800
11th to 20thNight
34%5%11%25%21%4
1628
21st to endNight
29%8%19%27%16%1
1746
June1st to 10thNight
28%9%18%27%17%1
1620
11th to 20thNight
21%8%18%33%17%3
1620
21st to endNight
29%10%20%27%13%1
1620
July1st to 10thNight
29%13%27%23%7%
1575
11th to 20thNight
22%11%33%24%10%
1566
21st to endNight
25%12%30%23%10%1
1673
August1st to 10thNight
16%9%30%32%12%1
1601
11th to 20thNight
24%10%27%25%12%1
1746
21st to endNight
33%11%21%22%10%3
1980
September1st to 10thNight
29%10%18%21%15%7%
1828
11th to 20thNight
36%9%14%19%16%7%
1980
21st to endNight
28%6%12%22%20%12%
1980
October1st to 10thNight
23%6%11%25%20%15%
2148
11th to 20thNight
29%48%19%25%16%
2160
21st to endNight
30%47%15%26%18%
2376
November1st to 10thNight
30%412%19%24%12%
2220
11th to 20thNight
33%5%9%17%25%11%
2280
21st to endNight
39%5%8%17%21%10%
2280
December1st to 10thNight
45%48%18%17%8%
2465
11th to 20thNight
44%45%13%22%13%
3037
21st to endNight
41%5%7%15%25%7%
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%11%39%19%6%1
270
11th to 20thDay
22%13%37%22%6%1
270
21st to endDay
23%18%37%19%3
297
February1st to 10thDay
23%20%32%20%4
267
11th to 20thDay
31%15%34%18%2
240
21st to endDay
28%19%42%10%1
198
March1st to 10thDay
28%16%30%20%7%
240
11th to 20thDay
17%19%38%20%5%1
240
21st to endDay
18%17%37%22%6%
264
April1st to 10thDay
12%17%37%27%7%
290
11th to 20thDay
23%14%25%27%10%1
412
21st to endDay
15%11%31%30%10%2
420
May1st to 10thDay
18%7%30%29%16%
423
11th to 20thDay
10%5%25%36%19%4
586
21st to endDay
8%5%24%35%22%6%
679
June1st to 10thDay
8%212%33%31%13%
630
11th to 20thDay
5%213%36%33%10%
630
21st to endDay
9%312%25%34%17%
630
July1st to 10thDay
7%28%24%39%20%
621
11th to 20thDay
45%25%40%26%
618
21st to endDay
6%15%22%43%23%
684
August1st to 10thDay
5%421%42%27%
626
11th to 20thDay
6%1313%47%30%
468
21st to endDay
11%15%18%33%31%
495
September1st to 10thDay
6%1418%42%28%
416
11th to 20thDay
11%17%26%38%18%
270
21st to endDay
14%27%28%32%17%
270
October1st to 10thDay
7%116%35%33%7%
270
11th to 20thDay
10%5%23%31%22%9%
270
21st to endDay
23%11%22%23%16%5%
297
November1st to 10thDay
14%428%28%21%5%
270
11th to 20thDay
15%10%33%30%12%1
270
21st to endDay
20%14%33%22%9%2
270
December1st to 10thDay
20%8%34%27%8%4
270
11th to 20thDay
21%11%36%25%5%
270
21st to endDay
20%14%38%22%5%1
297
January1st to 10thNight
22%13%33%27%5%
950
11th to 20thNight
24%12%31%25%8%
950
21st to endNight
24%12%32%29%3
1045
February1st to 10thNight
21%14%34%26%4
948
11th to 20thNight
25%14%34%23%4
686
21st to endNight
24%17%37%21%1
444
March1st to 10thNight
24%12%31%26%6%
540
11th to 20thNight
18%11%38%27%5%1
540
21st to endNight
18%9%37%28%8%
594
April1st to 10thNight
13%9%42%28%7%
540
11th to 20thNight
17%11%32%29%11%
533
21st to endNight
13%9%37%29%11%1
540
May1st to 10thNight
13%10%35%32%10%1
540
11th to 20thNight
13%428%38%15%1
531
21st to endNight
7%323%38%24%4
584
June1st to 10thNight
5%112%40%37%4
540
11th to 20thNight
3117%46%29%4
540
21st to endNight
6%111%37%37%7%
540
July1st to 10thNight
5%25%40%41%8%
525
11th to 20thNight
38%39%42%8%
522
21st to endNight
416%38%45%7%
591
August1st to 10thNight
31441%44%8%
537
11th to 20thNight
6%1337%46%6%
534
21st to endNight
8%15%30%44%11%
594
September1st to 10thNight
6%16%31%46%10%
540
11th to 20thNight
13%19%27%41%9%
540
21st to endNight
10%211%31%36%9%
540
October1st to 10thNight
6%212%37%38%5%
708
11th to 20thNight
12%5%22%38%19%3
720
21st to endNight
15%7%25%32%19%2
792
November1st to 10thNight
12%425%36%21%2
740
11th to 20thNight
13%11%24%38%13%
760
21st to endNight
18%10%32%28%11%1
760
December1st to 10thNight
23%10%26%30%10%
945
11th to 20thNight
26%9%30%29%6%
950
21st to endNight
23%11%30%29%6%
1045
Page generated at 2024-02-07 05:11:54. Version ac07

Copyright 2024 Attilla Danko


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