Dallas
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dallas clear sky chart from 2005-11-05 to 2018-02-22.

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%
16269
29%
48875
20%
16226
59%
16226
38%
26982

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 15thNight
39%
972
29%
2522
13%
970
49%
970
40%
1483
January16th to endNight
37%
1040
33%
2704
13%
1040
49%
1040
39%
1594
February1st to 15thNight
34%
826
26%
2354
11%
822
44%
822
33%
1388
February16th to endNight
24%
642
29%
1960
10%
642
39%
642
31%
1120
March1st to 15thNight
35%
540
27%
1980
16%
540
49%
540
26%
1138
March16th to endNight
34%
576
24%
2112
15%
576
48%
576
29%
1158
April1st to 15thNight
31%
539
25%
1973
14%
539
50%
539
31%
1025
April16th to endNight
36%
540
26%
1716
17%
540
51%
540
35%
963
May1st to 15thNight
36%
540
23%
1620
14%
540
49%
540
32%
975
May16th to endNight
49%
562
25%
1684
20%
561
60%
561
38%
957
June1st to 15thNight
70%
540
24%
1620
24%
540
77%
540
52%
791
June16th to endNight
70%
540
26%
1620
27%
540
74%
540
45%
849
July1st to 15thNight
75%
510
25%
1530
28%
510
79%
510
47%
787
July16th to endNight
86%
564
30%
1594
38%
531
88%
531
55%
765
August1st to 15thNight
88%
539
36%
1610
43%
536
88%
536
60%
737
August16th to endNight
79%
573
28%
1887
33%
573
81%
573
38%
1009
September1st to 15thNight
71%
540
23%
1980
28%
540
72%
540
34%
1049
September16th to endNight
73%
537
33%
1980
35%
537
77%
537
39%
972
October1st to 15thNight
61%
621
33%
2061
27%
621
68%
621
43%
1033
October16th to endNight
53%
768
38%
2304
23%
768
63%
768
47%
1153
November1st to 15thNight
50%
770
30%
2290
17%
770
59%
770
40%
1260
November16th to endNight
42%
975
34%
2535
16%
975
53%
975
41%
1473
December1st to 15thNight
39%
975
31%
2535
14%
975
48%
975
36%
1575
December16th to endNight
35%
1040
26%
2704
12%
1040
44%
1040
33%
1728

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
11%42442445%7%50%
49373
Night
9%413313347%56%
49071
TransparencyDay
32%5%10%22%21%7%
49073
Night
28%410%22%23%10%
48876
SeeingDay
10%5%19%30%25%7%
6051
Night
11%6%28%35%16%1
16273

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 15thDay
14%5%23212235%55%
1746
16th to endDay
15%413312235%56%
1872
February1st to 15thDay
15%5%25%322225%50%
1848
16th to endDay
18%5%14312235%51%
1660
March1st to 15thDay
19%5%13324336%45%
1980
16th to endDay
13%6%35%423335%49%
2110
April1st to 15thDay
11%425%32445%7%48%
1974
16th to endDay
13%5%14424447%46%
2241
May1st to 15thDay
13%5%35%5%25%446%42%
2331
16th to endDay
10%5%345%35%5%6%8%40%
2430
June1st to 15thDay
5%314425%5%5%9%51%
2340
16th to endDay
7%2245%25%46%8%50%
2340
July1st to 15thDay
6%3245%25%5%6%9%47%
2340
16th to endDay
32135%35%5%8%11%48%
2466
August1st to 15thDay
311333447%9%57%
2340
16th to endDay
6%315%5%36%7%8%9%41%
2311
September1st to 15thDay
11%31442346%8%48%
1980
16th to endDay
7%41442445%7%53%
1980
October1st to 15thDay
10%313224346%56%
1887
16th to endDay
8%3321223467%
1920
November1st to 15thDay
9%424423445%55%
1895
16th to endDay
12%423311225%59%
1755
December1st to 15thDay
17%5%2332233450%
1755
16th to endDay
18%6%24312346%46%
1872
January1st to 15thNight
12%413312236%58%
2522
16th to endNight
12%43221323459%
2704
February1st to 15thNight
13%5%2331223456%
2344
16th to endNight
15%413412235%54%
1960
March1st to 15thNight
16%42411335%6%49%
1980
16th to endNight
11%413323346%54%
2112
April1st to 15thNight
8%423423447%54%
1973
16th to endNight
11%413313346%54%
1716
May1st to 15thNight
9%4245%24349%49%
1619
16th to endNight
7%42342436%10%51%
1683
June1st to 15thNight
411121335%9%65%
1620
16th to endNight
32134145%5%10%56%
1620
July1st to 15thNight
421232445%11%56%
1620
16th to endNight
211221346%11%61%
1702
August1st to 15thNight
112312249%69%
1620
16th to endNight
5%313425%5%7%11%49%
1887
September1st to 15thNight
10%31432345%8%53%
1980
16th to endNight
7%313323448%58%
1980
October1st to 15thNight
8%312322347%60%
2061
16th to endNight
8%31221322368%
2304
November1st to 15thNight
6%424323335%60%
2290
16th to endNight
11%41322244458%
2535
December1st to 15thNight
13%5%23322336%52%
2535
16th to endNight
15%6%24312345%48%
2704

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 15thDay
32%37%20%27%7%
1747
16th to endDay
32%35%19%30%10%
1872
February1st to 15thDay
37%27%20%22%8%
1849
16th to endDay
37%26%19%20%12%
1660
March1st to 15thDay
41%46%17%21%9%
1980
16th to endDay
38%49%18%21%7%
2112
April1st to 15thDay
35%5%10%21%16%11%
1974
16th to endDay
36%5%9%18%23%6%
2241
May1st to 15thDay
42%5%9%16%19%7%
2331
16th to endDay
39%7%12%19%16%2
2434
June1st to 15thDay
27%7%14%27%19%3
2340
16th to endDay
31%412%27%19%4
2340
July1st to 15thDay
29%7%15%30%15%1
2201
16th to endDay
24%8%19%30%15%1
2311
August1st to 15thDay
19%7%15%31%23%2
2326
16th to endDay
33%9%16%24%12%2
2311
September1st to 15thDay
33%5%11%23%19%7%
1980
16th to endDay
29%5%9%22%24%8%
1980
October1st to 15thDay
28%411%21%18%15%
1887
16th to endDay
22%36%18%30%19%
1920
November1st to 15thDay
31%49%23%21%9%
1895
16th to endDay
29%25%20%30%11%
1755
December1st to 15thDay
37%36%19%24%6%
1755
16th to endDay
40%36%21%20%7%
1872
January1st to 15thNight
30%27%18%29%12%
2522
16th to endNight
30%25%17%28%15%
2704
February1st to 15thNight
33%37%17%23%14%
2354
16th to endNight
33%39%19%21%13%
1960
March1st to 15thNight
35%5%7%16%21%12%
1980
16th to endNight
31%5%11%19%25%6%
2112
April1st to 15thNight
28%5%10%21%18%14%
1973
16th to endNight
30%5%9%21%23%10%
1716
May1st to 15thNight
33%6%11%18%20%9%
1620
16th to endNight
28%6%17%24%19%4
1685
June1st to 15thNight
17%5%13%33%23%6%
1620
16th to endNight
22%5%13%27%24%6%
1620
July1st to 15thNight
21%5%14%36%17%4
1530
16th to endNight
13%7%19%36%20%2
1594
August1st to 15thNight
13%414%31%30%6%
1610
16th to endNight
25%6%14%30%17%4
1887
September1st to 15thNight
29%5%12%22%21%9%
1980
16th to endNight
24%49%22%27%11%
1980
October1st to 15thNight
23%410%24%19%17%
2061
16th to endNight
22%2416%30%23%
2304
November1st to 15thNight
27%48%23%24%12%
2290
16th to endNight
28%36%15%32%13%
2535
December1st to 15thNight
34%48%19%22%10%
2535
16th to endNight
37%38%20%20%9%
2704

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 15thDay
14%9%38%28%8%
135
16th to endDay
10%11%45%19%11%2
144
February1st to 15thDay
9%15%42%25%6%
135
16th to endDay
21%20%38%17%4
100
March1st to 15thDay
27%17%27%18%6%1
90
16th to endDay
7%12%40%26%12%1
96
April1st to 15thDay
10%17%26%31%13%
93
16th to endDay
17%11%35%27%8%
351
May1st to 15thDay
14%13%35%26%7%2
468
16th to endDay
14%5%32%28%16%2
517
June1st to 15thDay
7%113%42%27%8%
495
16th to endDay
6%211%36%32%10%
495
July1st to 15thDay
7%10%38%34%9%
475
16th to endDay
3424%50%16%
515
August1st to 15thDay
4333%44%13%
493
16th to endDay
11%15%32%37%11%
351
September1st to 15thDay
2121%47%27%
135
16th to endDay
9%123%46%18%
135
October1st to 15thDay
117%31%38%11%
135
16th to endDay
11%5%18%36%22%6%
144
November1st to 15thDay
22%224%32%11%5%
135
16th to endDay
16%11%29%29%10%2
135
December1st to 15thDay
23%5%29%23%14%3
135
16th to endDay
24%12%36%21%5%
144
January1st to 15thNight
14%9%33%34%8%
975
16th to endNight
15%10%34%33%5%
1040
February1st to 15thNight
17%9%35%30%5%
826
16th to endNight
16%12%44%22%3
642
March1st to 15thNight
16%10%35%32%5%
540
16th to endNight
11%10%41%29%6%
576
April1st to 15thNight
8%11%47%27%6%
539
16th to endNight
14%6%40%30%7%
540
May1st to 15thNight
10%5%42%32%7%1
540
16th to endNight
7%433%36%17%1
563
June1st to 15thNight
4119%49%24%1
540
16th to endNight
317%46%28%2
540
July1st to 15thNight
413%45%33%2
510
16th to endNight
3447%40%4
564
August1st to 15thNight
2347%41%5%
539
16th to endNight
7%6%38%41%5%
573
September1st to 15thNight
12%18%36%38%3
540
16th to endNight
8%12%37%36%5%
537
October1st to 15thNight
10%123%33%27%3
621
16th to endNight
10%5%28%34%19%1
768
November1st to 15thNight
9%5%31%34%17%
770
16th to endNight
14%8%32%31%12%
975
December1st to 15thNight
17%6%33%34%7%
975
16th to endNight
19%8%33%31%6%
1040
Page generated at 2018-02-23 10:21:29. Version ac04

Copyright 2018 A. Danko


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