Brenham
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brenham clear sky chart from 2005-11-06 to 2024-02-15.

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
49%
23869
24%
79389
17%
23763
56%
23763
29%
46606

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
33%
945
29%
3987
11%
926
43%
926
20%
2312
January11th to 20thNight
33%
949
30%
3925
9%
930
42%
930
22%
2087
January21st to endNight
33%
1035
18%
4452
10%
1023
43%
1023
18%
2817
February1st to 10thNight
26%
796
23%
2316
8%
796
37%
796
22%
1543
February11th to 20thNight
28%
722
20%
2152
9%
718
36%
718
24%
1380
February21st to endNight
20%
501
23%
1685
6%
501
34%
501
18%
1100
March1st to 10thNight
26%
540
23%
1980
10%
540
41%
540
20%
1240
March11th to 20thNight
33%
540
21%
1980
13%
540
43%
540
19%
1246
March21st to endNight
31%
594
25%
2178
15%
594
46%
594
25%
1251
April1st to 10thNight
31%
540
23%
1980
13%
540
46%
540
24%
1175
April11th to 20thNight
33%
533
22%
1875
15%
533
45%
533
24%
1125
April21st to endNight
33%
540
24%
1800
15%
540
48%
540
26%
1068
May1st to 10thNight
32%
540
22%
1634
15%
540
43%
540
26%
1040
May11th to 20thNight
48%
531
23%
1594
22%
531
54%
531
33%
955
May21st to endNight
53%
584
23%
1745
21%
582
62%
582
34%
1050
June1st to 10thNight
73%
540
22%
1620
24%
540
76%
540
42%
880
June11th to 20thNight
68%
540
22%
1620
23%
540
73%
540
46%
850
June21st to endNight
74%
540
19%
1620
22%
540
76%
540
35%
963
July1st to 10thNight
74%
525
17%
1575
20%
525
75%
525
34%
952
July11th to 20thNight
82%
522
23%
1566
27%
522
84%
522
46%
811
July21st to endNight
84%
591
20%
1673
23%
558
86%
558
46%
877
August1st to 10thNight
90%
537
27%
1601
29%
534
91%
534
60%
728
August11th to 20thNight
82%
534
25%
1610
28%
534
83%
534
41%
885
August21st to endNight
79%
594
18%
2135
21%
594
81%
594
31%
1196
September1st to 10thNight
78%
540
19%
1980
21%
540
80%
540
32%
1098
September11th to 20thNight
69%
540
22%
1980
25%
540
70%
540
26%
1196
September21st to endNight
71%
540
27%
1980
29%
540
72%
540
35%
1027
October1st to 10thNight
77%
571
34%
2011
34%
571
78%
571
44%
960
October11th to 20thNight
60%
720
32%
2160
22%
720
66%
720
39%
1191
October21st to endNight
50%
792
33%
2376
21%
792
59%
792
38%
1334
November1st to 10thNight
55%
740
28%
2220
21%
740
60%
740
35%
1294
November11th to 20thNight
47%
760
27%
2280
17%
760
55%
760
32%
1348
November21st to endNight
41%
915
26%
2435
14%
915
48%
915
30%
1593
December1st to 10thNight
40%
950
27%
2470
14%
950
47%
950
29%
1638
December11th to 20thNight
34%
949
24%
2885
11%
948
40%
948
22%
1908
December21st to endNight
35%
1039
16%
4309
11%
1026
43%
1026
19%
2488

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%35%5%35%5%5%8%43%
78769
Night
12%6%2442445%7%49%
80366
TransparencyDay
39%7%11%19%18%7%
78494
Night
34%6%11%20%18%10%
80161
SeeingDay
13%6%19%26%26%10%
13829
Night
14%6%24%35%19%2
23892

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
16%9%25%3335%5%5%45%
2847
11th to 20thDay
17%7%23322247%51%
2850
21st to endDay
23%9%36%423348%36%
3135
February1st to 10thDay
22%8%35%42343440%
1880
11th to 20thDay
21%7%25%5%34336%41%
1789
21st to endDay
19%7%35%5%33445%42%
1570
March1st to 10thDay
19%8%37%6%25%447%35%
1980
11th to 20thDay
17%8%37%43445%5%41%
1980
21st to endDay
15%6%36%5%3435%5%44%
2178
April1st to 10thDay
15%8%36%6%346%47%38%
1980
11th to 20thDay
16%6%36%5%445%5%6%40%
2032
21st to endDay
13%6%35%434448%45%
2160
May1st to 10thDay
12%6%36%5%46%5%7%8%40%
2322
11th to 20thDay
11%7%26%6%35%5%6%7%42%
2302
21st to endDay
11%6%36%7%46%6%8%9%33%
2531
June1st to 10thDay
5%425%5%5%6%6%7%9%45%
2340
11th to 20thDay
6%3245%46%7%8%10%45%
2340
21st to endDay
6%5%26%7%6%8%7%8%11%33%
2340
July1st to 10thDay
9%5%37%7%46%7%8%9%35%
2340
11th to 20thDay
4325%6%48%8%8%11%42%
2340
21st to endDay
3325%5%47%7%8%14%41%
2546
August1st to 10thDay
32146%45%6%7%11%51%
2328
11th to 20thDay
5%425%6%46%7%7%11%45%
2288
21st to endDay
6%326%7%5%7%6%7%10%42%
2215
September1st to 10thDay
6%5%25%6%47%7%7%9%41%
1980
11th to 20thDay
10%7%36%6%5%6%6%6%7%37%
1980
21st to endDay
6%425%6%46%6%6%7%48%
1980
October1st to 10thDay
5%4245%35%5%48%56%
1930
11th to 20thDay
12%6%245%34446%51%
1800
21st to endDay
13%5%25%323345%55%
1980
November1st to 10thDay
11%6%245%35%5%5%7%47%
1858
11th to 20thDay
11%5%2442445%6%52%
1900
21st to endDay
17%6%36%5%44445%42%
1742
December1st to 10thDay
16%7%26%5%24437%43%
1710
11th to 20thDay
17%7%36%5%24445%43%
2161
21st to endDay
16%7%25%42434448%
3135
January1st to 10thNight
18%7%24423345%48%
4108
11th to 20thNight
17%6%2431223456%
4120
21st to endNight
22%8%25%423346%41%
4532
February1st to 10thNight
19%8%36%433336%41%
2316
11th to 20thNight
21%7%245%23335%46%
2152
21st to endNight
22%6%26%43345%5%41%
1685
March1st to 10thNight
17%6%36%5%2346%7%41%
1980
11th to 20thNight
15%7%35%43446%6%42%
1980
21st to endNight
13%6%25%423446%50%
2178
April1st to 10thNight
11%6%24435%45%8%46%
1980
11th to 20thNight
14%7%35%5%2446%6%45%
1875
21st to endNight
13%7%345%34346%48%
1800
May1st to 10thNight
11%6%36%5%35%5%5%9%43%
1634
11th to 20thNight
9%5%35%4345%6%7%49%
1593
21st to endNight
6%6%245%35%5%6%10%47%
1745
June1st to 10thNight
442443447%10%56%
1620
11th to 20thNight
4322325%5%5%12%57%
1620
21st to endNight
4325%5%45%7%7%12%47%
1620
July1st to 10thNight
7%3245%35%5%6%10%49%
1620
11th to 20thNight
22133245%7%11%59%
1620
21st to endNight
32134245%7%14%55%
1772
August1st to 10thNight
111232346%13%66%
1611
11th to 20thNight
3423435%6%7%13%53%
1610
21st to endNight
42246%36%5%8%12%48%
2135
September1st to 10thNight
5%325%435%6%6%10%51%
1980
11th to 20thNight
10%6%26%5%3446%7%46%
1980
21st to endNight
8%42343446%9%54%
1980
October1st to 10thNight
432442346%7%62%
2011
11th to 20thNight
11%414423346%58%
2160
21st to endNight
12%5%23323335%59%
2376
November1st to 10thNight
10%5%245%33346%54%
2220
11th to 20thNight
11%5%25%433447%51%
2280
21st to endNight
16%6%35%433347%46%
2435
December1st to 10thNight
17%7%24423446%45%
2470
11th to 20thNight
17%8%35%42345%6%43%
3036
21st to endNight
16%7%24423345%49%
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
40%5%6%16%22%11%
2848
11th to 20thDay
36%45%20%27%8%
2850
21st to endDay
49%3413%19%12%
3135
February1st to 10thDay
50%35%12%19%12%
1880
11th to 20thDay
46%5%7%15%17%10%
1799
21st to endDay
45%48%14%17%12%
1570
March1st to 10thDay
50%5%8%11%19%7%
1980
11th to 20thDay
46%5%6%12%20%11%
1980
21st to endDay
43%5%6%16%21%8%
2178
April1st to 10thDay
46%5%7%18%15%9%
1980
11th to 20thDay
43%6%8%14%18%10%
2032
21st to endDay
39%5%7%20%21%7%
2160
May1st to 10thDay
41%7%10%18%16%8%
2322
11th to 20thDay
39%8%11%21%19%3
2306
21st to endDay
43%9%13%22%12%1
2531
June1st to 10thDay
32%8%14%27%16%2
2340
11th to 20thDay
30%9%15%26%18%3
2340
21st to endDay
42%10%13%24%10%1
2340
July1st to 10thDay
40%9%19%24%8%1
2276
11th to 20thDay
31%12%21%22%14%1
2271
21st to endDay
27%12%24%28%8%1
2405
August1st to 10thDay
25%10%18%32%14%1
2314
11th to 20thDay
32%10%20%26%10%2
2288
21st to endDay
35%11%18%24%11%2
2215
September1st to 10thDay
34%12%13%20%15%6%
1980
11th to 20thDay
42%9%12%16%17%4
1980
21st to endDay
35%7%10%20%17%12%
1980
October1st to 10thDay
28%5%11%23%22%13%
1930
11th to 20thDay
35%47%17%20%17%
1800
21st to endDay
32%5%5%16%24%18%
1980
November1st to 10thDay
36%6%9%19%21%10%
1858
11th to 20thDay
33%6%10%17%21%13%
1900
21st to endDay
44%47%15%18%11%
1742
December1st to 10thDay
43%5%9%17%19%7%
1710
11th to 20thDay
43%5%8%11%23%10%
2159
21st to endDay
41%46%14%25%11%
3135
January1st to 10thNight
39%5%7%17%18%15%
4108
11th to 20thNight
34%4418%27%12%
4120
21st to endNight
46%4414%22%10%
4532
February1st to 10thNight
46%46%12%18%15%
2316
11th to 20thNight
43%46%16%17%13%
2152
21st to endNight
47%5%7%13%14%14%
1685
March1st to 10thNight
43%6%9%15%18%9%
1980
11th to 20thNight
43%7%8%14%19%10%
1980
21st to endNight
37%5%11%16%21%11%
2178
April1st to 10thNight
37%7%10%20%17%10%
1980
11th to 20thNight
39%5%10%16%16%14%
1875
21st to endNight
37%5%9%21%19%8%
1800
May1st to 10thNight
39%7%10%18%17%9%
1634
11th to 20thNight
33%6%13%26%18%4
1594
21st to endNight
33%7%16%31%13%1
1746
June1st to 10thNight
23%8%16%32%20%2
1620
11th to 20thNight
20%8%19%31%18%4
1620
21st to endNight
29%9%20%27%13%1
1620
July1st to 10thNight
29%11%22%30%9%
1575
11th to 20thNight
18%10%28%32%12%
1566
21st to endNight
18%11%31%32%9%
1673
August1st to 10thNight
11%7%27%38%16%1
1601
11th to 20thNight
22%10%25%33%9%2
1610
21st to endNight
27%11%23%28%9%2
2135
September1st to 10thNight
27%10%20%23%14%6%
1980
11th to 20thNight
36%8%14%22%14%6%
1980
21st to endNight
27%6%16%20%18%12%
1980
October1st to 10thNight
21%5%12%27%21%14%
2011
11th to 20thNight
28%5%7%20%22%17%
2160
21st to endNight
30%46%17%22%22%
2376
November1st to 10thNight
32%6%10%21%21%11%
2220
11th to 20thNight
34%49%19%20%13%
2280
21st to endNight
40%48%16%19%12%
2435
December1st to 10thNight
41%5%7%21%16%10%
2470
11th to 20thNight
43%5%6%12%20%15%
3037
21st to endNight
38%5%415%28%10%
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%7%40%23%6%1
270
11th to 20thDay
25%10%30%26%7%1
270
21st to endDay
22%16%32%21%8%
297
February1st to 10thDay
32%14%27%20%6%
270
11th to 20thDay
29%17%29%17%8%
252
21st to endDay
28%20%28%20%31
198
March1st to 10thDay
23%14%34%22%7%
240
11th to 20thDay
19%15%38%20%6%1
240
21st to endDay
19%14%35%22%8%1
264
April1st to 10thDay
15%16%38%24%6%1
240
11th to 20thDay
23%12%29%23%11%1
310
21st to endDay
18%8%33%26%14%1
420
May1st to 10thDay
13%9%37%29%11%1
585
11th to 20thDay
14%6%26%31%20%3
625
21st to endDay
13%424%34%22%3
679
June1st to 10thDay
6%112%37%34%11%
630
11th to 20thDay
7%111%40%32%9%
630
21st to endDay
8%110%28%39%14%
630
July1st to 10thDay
7%27%28%39%17%
621
11th to 20thDay
2330%46%18%
618
21st to endDay
315%24%50%18%
684
August1st to 10thDay
4222%50%22%
626
11th to 20thDay
5%1420%47%23%
602
21st to endDay
8%1414%30%43%
334
September1st to 10thDay
6%1420%37%33%
270
11th to 20thDay
8%6%17%40%28%
270
21st to endDay
7%36%20%40%24%
270
October1st to 10thDay
439%29%39%15%
270
11th to 20thDay
11%5%17%33%22%13%
270
21st to endDay
22%10%20%23%20%5%
297
November1st to 10thDay
15%416%35%21%8%
270
11th to 20thDay
16%8%22%33%17%4
270
21st to endDay
23%14%32%19%10%3
270
December1st to 10thDay
17%7%30%25%15%6%
270
11th to 20thDay
23%17%27%21%10%2
270
21st to endDay
21%9%35%25%6%3
297
January1st to 10thNight
21%10%32%29%8%
950
11th to 20thNight
23%10%29%30%8%
950
21st to endNight
22%10%30%31%6%
1045
February1st to 10thNight
23%13%33%26%4
796
11th to 20thNight
26%10%33%27%5%
722
21st to endNight
26%13%39%19%3
501
March1st to 10thNight
21%10%38%27%4
540
11th to 20thNight
17%10%35%31%7%
540
21st to endNight
16%10%40%28%6%
594
April1st to 10thNight
12%9%44%31%4
540
11th to 20thNight
16%11%35%31%7%
533
21st to endNight
15%9%39%27%9%1
540
May1st to 10thNight
14%10%40%30%5%
540
11th to 20thNight
11%432%38%14%1
531
21st to endNight
7%428%42%18%1
584
June1st to 10thNight
4213%51%27%2
540
11th to 20thNight
4120%52%21%1
540
21st to endNight
4111%45%34%4
540
July1st to 10thNight
7%17%44%36%5%
525
11th to 20thNight
317%45%41%4
522
21st to endNight
316%47%40%4
591
August1st to 10thNight
1450%42%3
537
11th to 20thNight
45%45%40%6%
534
21st to endNight
5%6%33%50%7%
594
September1st to 10thNight
6%7%32%49%7%
540
11th to 20thNight
10%17%33%44%5%
540
21st to endNight
9%112%30%41%6%
540
October1st to 10thNight
6%110%43%33%6%
571
11th to 20thNight
12%321%40%21%3
720
21st to endNight
13%7%26%31%20%3
792
November1st to 10thNight
11%423%39%21%2
740
11th to 20thNight
13%8%26%37%16%1
760
21st to endNight
18%8%28%31%14%1
915
December1st to 10thNight
20%9%27%31%13%1
950
11th to 20thNight
25%9%28%30%7%
950
21st to endNight
20%10%30%31%9%1
1045
Page generated at 2024-02-12 05:35:36. Version ac07

Copyright 2024 Attilla Danko


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