Austin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Austin clear sky chart from 2005-11-06 to 2024-01-31.

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
50%
23842
25%
74506
18%
23786
57%
23786
32%
43210

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
39%
947
30%
2458
13%
946
49%
946
38%
1484
January11th to 20thNight
37%
950
28%
2470
12%
950
46%
950
35%
1533
January21st to endNight
36%
967
29%
2635
12%
967
47%
967
31%
1656
February1st to 10thNight
32%
720
26%
2160
10%
720
44%
720
26%
1340
February11th to 20thNight
28%
704
23%
2098
9%
700
39%
700
28%
1288
February21st to endNight
21%
592
26%
1776
6%
592
37%
592
24%
1123
March1st to 10thNight
29%
540
24%
1980
12%
540
42%
540
22%
1199
March11th to 20thNight
35%
540
21%
1980
16%
540
43%
540
21%
1214
March21st to endNight
32%
594
25%
2178
15%
594
46%
594
26%
1240
April1st to 10thNight
31%
540
24%
1980
14%
540
46%
540
26%
1152
April11th to 20thNight
29%
533
21%
1953
14%
533
43%
533
24%
1169
April21st to endNight
32%
540
28%
1668
15%
540
48%
540
30%
1005
May1st to 10thNight
36%
540
24%
1620
16%
540
46%
540
27%
1018
May11th to 20thNight
47%
531
22%
1594
20%
531
53%
531
31%
975
May21st to endNight
49%
583
22%
1745
17%
582
59%
582
33%
1038
June1st to 10thNight
73%
540
24%
1620
25%
540
78%
540
48%
832
June11th to 20thNight
63%
540
23%
1620
22%
540
70%
540
44%
849
June21st to endNight
69%
540
22%
1620
24%
540
73%
540
37%
933
July1st to 10thNight
71%
525
17%
1575
18%
525
74%
525
37%
913
July11th to 20thNight
81%
522
26%
1566
29%
522
84%
522
51%
772
July21st to endNight
82%
591
26%
1673
28%
558
86%
558
50%
832
August1st to 10thNight
89%
537
29%
1601
31%
534
91%
534
63%
711
August11th to 20thNight
78%
534
25%
1720
29%
534
79%
534
37%
949
August21st to endNight
80%
594
20%
2096
24%
594
81%
594
35%
1112
September1st to 10thNight
74%
540
22%
1980
26%
540
76%
540
33%
1073
September11th to 20thNight
72%
540
21%
1980
25%
540
72%
540
27%
1180
September21st to endNight
71%
540
26%
1980
27%
540
73%
540
34%
1036
October1st to 10thNight
75%
540
34%
1980
36%
540
77%
540
40%
964
October11th to 20thNight
60%
668
32%
2108
23%
668
66%
668
35%
1195
October21st to endNight
52%
792
32%
2376
20%
792
59%
792
39%
1320
November1st to 10thNight
58%
740
28%
2220
21%
740
61%
740
36%
1299
November11th to 20thNight
50%
850
27%
2370
16%
850
56%
850
37%
1411
November21st to endNight
39%
950
27%
2470
13%
950
46%
950
30%
1619
December1st to 10thNight
44%
950
30%
2470
16%
950
51%
950
34%
1565
December11th to 20thNight
37%
948
26%
2878
12%
948
43%
948
24%
1862
December21st to endNight
39%
1040
17%
4308
13%
1026
46%
1026
24%
2349

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%5%2443445%7%47%
75057
Night
14%5%2442445%7%51%
75095
TransparencyDay
37%5%10%21%19%9%
74782
Night
34%411%21%19%11%
74890
SeeingDay
13%5%19%27%26%10%
13782
Night
15%5%24%36%18%2
23853

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%5%24323346%52%
1707
11th to 20thDay
19%6%23323247%49%
1710
21st to endDay
17%5%34324335%51%
1963
February1st to 10thDay
21%6%35%422445%46%
1800
11th to 20thDay
21%6%24423346%44%
1749
21st to endDay
20%6%2442433449%
1480
March1st to 10thDay
21%7%36%424446%40%
1977
11th to 20thDay
19%6%345%34346%44%
1980
21st to endDay
16%6%24324446%48%
2178
April1st to 10thDay
16%8%35%5%2445%6%42%
1980
11th to 20thDay
19%5%25%5%33445%43%
1956
21st to endDay
15%6%35%43445%6%45%
2286
May1st to 10thDay
16%6%36%5%35%5%46%40%
2340
11th to 20thDay
15%6%36%5%45%5%6%6%38%
2302
21st to endDay
16%6%36%6%46%6%6%9%34%
2531
June1st to 10thDay
7%415%5%35%5%7%9%50%
2340
11th to 20thDay
8%4246%36%5%7%9%46%
2340
21st to endDay
7%5%35%8%47%6%8%10%38%
2340
July1st to 10thDay
10%5%35%6%47%5%7%9%38%
2340
11th to 20thDay
5%3235%35%6%8%11%50%
2340
21st to endDay
5%3235%35%6%7%11%51%
2546
August1st to 10thDay
221242446%10%63%
2328
11th to 20thDay
6%3235%35%5%5%10%53%
2175
21st to endDay
5%325%6%47%7%6%11%44%
2258
September1st to 10thDay
9%5%36%6%35%5%6%8%46%
1980
11th to 20thDay
12%5%37%5%35%7%5%7%41%
1980
21st to endDay
8%424445%6%7%7%49%
1980
October1st to 10thDay
7%42443445%8%55%
1980
11th to 20thDay
14%5%23434446%52%
1832
21st to endDay
13%413322345%59%
1980
November1st to 10thDay
15%6%25%433447%47%
1858
11th to 20thDay
13%6%25%5%24445%51%
1805
21st to endDay
19%7%34423345%46%
1710
December1st to 10thDay
15%7%24433346%48%
1710
11th to 20thDay
18%7%3442435%5%44%
2161
21st to endDay
18%5%24323245%53%
3135
January1st to 10thNight
17%6%23222336%54%
2458
11th to 20thNight
18%5%14323336%52%
2470
21st to endNight
18%6%24423345%49%
2635
February1st to 10thNight
19%7%25%323346%48%
2160
11th to 20thNight
21%5%24223245%49%
2098
21st to endNight
22%6%23424445%45%
1776
March1st to 10thNight
19%6%244345%47%43%
1980
11th to 20thNight
18%8%24334446%43%
1980
21st to endNight
16%6%24323446%49%
2178
April1st to 10thNight
15%6%3442445%7%46%
1980
11th to 20thNight
19%5%25%334446%45%
1953
21st to endNight
17%6%23424347%48%
1668
May1st to 10thNight
14%6%25%5%35%5%5%8%43%
1620
11th to 20thNight
14%6%2443345%8%48%
1593
21st to endNight
14%5%133245%7%10%45%
1745
June1st to 10thNight
5%31331446%9%60%
1620
11th to 20thNight
5%324325%45%9%59%
1620
21st to endNight
6%4245%245%7%9%52%
1620
July1st to 10thNight
8%424425%5%7%10%48%
1620
11th to 20thNight
321332436%13%59%
1620
21st to endNight
331333446%10%60%
1772
August1st to 10thNight
111221336%9%71%
1611
11th to 20thNight
5%3244345%6%10%53%
1720
21st to endNight
5%3145%35%6%7%11%50%
2096
September1st to 10thNight
8%425%43445%8%52%
1980
11th to 20thNight
10%5%35%5%35%45%7%46%
1980
21st to endNight
8%5%2342446%8%54%
1980
October1st to 10thNight
7%313424347%61%
1980
11th to 20thNight
14%414323447%54%
2108
21st to endNight
16%423213335%60%
2376
November1st to 10thNight
14%5%24423437%54%
2220
11th to 20thNight
11%5%24433346%55%
2370
21st to endNight
20%5%24433446%46%
2470
December1st to 10thNight
15%6%3433434451%
2470
11th to 20thNight
18%8%34423345%46%
3036
21st to endNight
20%6%13222235%53%
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
36%35%20%23%13%
1708
11th to 20thDay
38%35%18%22%14%
1710
21st to endDay
38%35%14%26%15%
1963
February1st to 10thDay
43%36%13%21%14%
1800
11th to 20thDay
43%37%17%18%12%
1759
21st to endDay
42%25%17%18%15%
1480
March1st to 10thDay
46%48%13%20%9%
1977
11th to 20thDay
43%47%12%20%14%
1980
21st to endDay
38%49%17%21%11%
2178
April1st to 10thDay
44%47%18%15%11%
1980
11th to 20thDay
44%37%16%19%11%
1956
21st to endDay
40%45%21%21%9%
2286
May1st to 10thDay
44%48%17%18%8%
2340
11th to 20thDay
45%5%9%20%17%4
2306
21st to endDay
47%6%11%20%15%2
2531
June1st to 10thDay
30%5%14%27%20%4
2340
11th to 20thDay
31%7%12%27%18%5%
2340
21st to endDay
40%8%10%23%16%3
2340
July1st to 10thDay
40%8%15%25%11%2
2276
11th to 20thDay
26%6%18%27%20%2
2271
21st to endDay
24%6%23%33%13%1
2405
August1st to 10thDay
18%5%16%39%20%1
2314
11th to 20thDay
26%6%17%32%14%5%
2175
21st to endDay
31%8%16%27%15%3
2258
September1st to 10thDay
37%6%11%22%16%9%
1980
11th to 20thDay
41%6%11%19%18%5%
1980
21st to endDay
32%7%9%22%18%13%
1980
October1st to 10thDay
28%5%10%22%24%12%
1980
11th to 20thDay
33%48%16%22%17%
1832
21st to endDay
30%35%17%25%20%
1980
November1st to 10thDay
39%48%19%21%10%
1858
11th to 20thDay
37%38%18%21%14%
1805
21st to endDay
43%35%16%20%13%
1710
December1st to 10thDay
39%38%20%22%8%
1710
11th to 20thDay
43%37%12%22%13%
2159
21st to endDay
36%35%15%27%13%
3135
January1st to 10thNight
33%25%18%23%18%
2458
11th to 20thNight
36%26%18%23%15%
2470
21st to endNight
39%3415%22%18%
2635
February1st to 10thNight
41%35%13%20%18%
2160
11th to 20thNight
40%36%17%19%15%
2098
21st to endNight
43%36%15%16%17%
1776
March1st to 10thNight
42%410%15%19%10%
1980
11th to 20thNight
43%49%11%20%13%
1980
21st to endNight
37%410%16%19%13%
2178
April1st to 10thNight
39%39%19%17%13%
1980
11th to 20thNight
41%310%14%17%15%
1953
21st to endNight
38%39%21%18%9%
1668
May1st to 10thNight
40%411%19%17%9%
1620
11th to 20thNight
36%5%11%26%17%4
1594
21st to endNight
34%5%16%29%14%1
1746
June1st to 10thNight
20%6%18%30%23%4
1620
11th to 20thNight
24%5%15%31%20%5%
1620
21st to endNight
28%8%17%28%16%3
1620
July1st to 10thNight
29%8%22%29%11%1
1575
11th to 20thNight
18%6%25%31%19%1
1566
21st to endNight
19%6%25%39%10%1
1673
August1st to 10thNight
11%5%24%38%20%1
1601
11th to 20thNight
27%7%21%29%13%3
1720
21st to endNight
26%8%22%29%12%4
2096
September1st to 10thNight
30%6%16%26%16%7%
1980
11th to 20thNight
36%7%14%22%14%6%
1980
21st to endNight
28%6%14%22%18%12%
1980
October1st to 10thNight
24%5%10%25%22%13%
1980
11th to 20thNight
32%5%7%18%19%19%
2108
21st to endNight
30%26%16%23%22%
2376
November1st to 10thNight
33%49%18%22%13%
2220
11th to 20thNight
33%48%20%21%15%
2370
21st to endNight
41%37%16%18%15%
2470
December1st to 10thNight
38%27%22%19%11%
2470
11th to 20thNight
42%35%12%21%17%
3037
21st to endNight
36%25%14%29%13%
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
17%11%36%24%10%1
270
11th to 20thDay
24%10%27%28%9%2
270
21st to endDay
20%9%37%24%8%1
294
February1st to 10thDay
27%10%32%21%10%1
240
11th to 20thDay
25%15%31%22%6%1
240
21st to endDay
26%14%38%19%3
198
March1st to 10thDay
25%11%34%23%7%1
240
11th to 20thDay
20%13%34%26%6%2
240
21st to endDay
17%14%35%26%8%1
264
April1st to 10thDay
20%12%37%23%7%1
240
11th to 20thDay
21%9%34%23%12%1
234
21st to endDay
17%10%35%26%10%1
546
May1st to 10thDay
16%8%33%30%13%
603
11th to 20thDay
17%6%24%32%18%3
625
21st to endDay
16%420%33%23%4
679
June1st to 10thDay
8%210%37%33%10%
630
11th to 20thDay
8%111%44%29%7%
630
21st to endDay
6%310%30%36%15%
630
July1st to 10thDay
8%19%30%38%15%
621
11th to 20thDay
41326%51%15%
618
21st to endDay
41224%51%17%
684
August1st to 10thDay
3421%53%19%
626
11th to 20thDay
6%324%48%19%
489
21st to endDay
6%15%18%32%38%
377
September1st to 10thDay
8%317%38%34%
270
11th to 20thDay
8%420%36%31%
270
21st to endDay
11%19%16%36%27%
270
October1st to 10thDay
6%110%28%39%17%
270
11th to 20thDay
13%217%32%26%10%
270
21st to endDay
20%9%23%22%20%6%
297
November1st to 10thDay
20%320%31%19%7%
270
11th to 20thDay
19%6%24%28%19%4
270
21st to endDay
20%11%32%23%11%3
270
December1st to 10thDay
17%6%31%27%14%6%
270
11th to 20thDay
22%11%30%23%13%1
270
21st to endDay
20%9%31%26%12%2
297
January1st to 10thNight
20%8%30%33%9%1
950
11th to 20thNight
21%9%28%33%9%
950
21st to endNight
21%8%31%34%7%
967
February1st to 10thNight
23%10%30%30%7%
720
11th to 20thNight
25%9%36%27%3
704
21st to endNight
28%11%38%22%2
592
March1st to 10thNight
21%10%35%30%4
540
11th to 20thNight
20%9%31%34%5%
540
21st to endNight
16%10%40%31%31
594
April1st to 10thNight
17%7%40%32%4
540
11th to 20thNight
20%9%39%27%5%
533
21st to endNight
16%9%39%28%7%
540
May1st to 10thNight
16%9%36%32%7%
540
11th to 20thNight
15%5%28%39%13%1
531
21st to endNight
15%328%36%18%
584
June1st to 10thNight
6%215%48%28%1
540
11th to 20thNight
5%125%51%16%1
540
21st to endNight
6%114%45%29%4
540
July1st to 10thNight
8%29%43%34%5%
525
11th to 20thNight
5%8%49%35%3
522
21st to endNight
416%47%40%3
591
August1st to 10thNight
1453%37%4
537
11th to 20thNight
7%5%45%38%5%
534
21st to endNight
5%5%36%47%6%
594
September1st to 10thNight
9%16%38%42%5%
540
11th to 20thNight
11%25%33%44%5%
540
21st to endNight
9%111%35%40%4
540
October1st to 10thNight
6%29%44%33%5%
540
11th to 20thNight
15%317%38%25%2
668
21st to endNight
16%6%23%30%22%2
792
November1st to 10thNight
14%319%41%22%1
740
11th to 20thNight
14%6%25%35%18%2
850
21st to endNight
22%6%27%31%13%1
950
December1st to 10thNight
18%7%26%36%12%1
950
11th to 20thNight
24%8%26%35%7%1
950
21st to endNight
22%6%29%35%8%
1045
Page generated at 2024-01-28 04:26:37. Version ac07

Copyright 2024 Attilla Danko


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