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 2017-05-01.

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%
15164
29%
45635
20%
15121
58%
15121
38%
25171

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
38%
897
29%
2327
13%
895
48%
895
40%
1374
January16th to endNight
37%
960
33%
2496
13%
960
49%
960
38%
1476
February1st to 15thNight
34%
761
27%
2169
11%
757
45%
757
33%
1281
February16th to endNight
25%
614
30%
1876
10%
614
41%
614
33%
1042
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
34%
498
24%
1494
14%
498
48%
498
30%
920
May16th to endNight
50%
514
24%
1540
20%
513
60%
513
37%
880
June1st to 15thNight
71%
495
26%
1485
26%
495
77%
495
53%
719
June16th to endNight
69%
495
24%
1485
25%
495
73%
495
45%
782
July1st to 15thNight
75%
465
26%
1395
29%
465
78%
465
47%
724
July16th to endNight
86%
522
28%
1468
35%
489
87%
489
53%
716
August1st to 15thNight
89%
494
39%
1475
46%
491
90%
491
63%
657
August16th to endNight
80%
525
28%
1728
33%
525
82%
525
41%
895
September1st to 15thNight
69%
495
23%
1815
28%
495
71%
495
32%
994
September16th to endNight
73%
492
33%
1815
34%
492
77%
492
40%
884
October1st to 15thNight
60%
569
35%
1889
28%
569
67%
569
43%
949
October16th to endNight
53%
704
37%
2112
22%
704
63%
704
47%
1060
November1st to 15thNight
51%
709
32%
2109
18%
709
61%
709
42%
1136
November16th to endNight
42%
900
32%
2340
16%
900
51%
900
39%
1382
December1st to 15thNight
38%
900
30%
2340
14%
900
48%
900
35%
1453
December16th to endNight
36%
960
27%
2496
12%
960
45%
960
34%
1563

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%42442435%7%50%
46120
Night
9%413313347%56%
45831
TransparencyDay
32%5%10%22%21%7%
45820
Night
28%410%22%23%11%
45636
SeeingDay
10%5%19%30%25%7%
4940
Night
11%6%28%35%16%1
15168

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%6%23212235%55%
1611
16th to endDay
15%413312245%54%
1728
February1st to 15thDay
15%5%24312225%52%
1702
16th to endDay
17%414312235%53%
1598
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
14%6%35%5%25%45%7%40%
2138
16th to endDay
10%5%345%36%46%8%39%
2222
June1st to 15thDay
5%213425%5%6%9%52%
2145
16th to endDay
7%2245%25%45%8%50%
2145
July1st to 15thDay
7%3245%25%5%6%9%47%
2145
16th to endDay
42135%35%6%7%10%47%
2284
August1st to 15thDay
211232336%9%61%
2145
16th to endDay
6%315%5%36%7%8%10%42%
2118
September1st to 15thDay
12%31442446%9%46%
1815
16th to endDay
7%41442335%7%54%
1815
October1st to 15thDay
10%313223346%56%
1730
16th to endDay
9%31321223466%
1760
November1st to 15thDay
9%423413335%56%
1746
16th to endDay
13%423322225%58%
1620
December1st to 15thDay
18%5%2332233449%
1620
16th to endDay
17%5%24312346%48%
1728
January1st to 15thNight
13%413312225%58%
2327
16th to endNight
12%43222323458%
2496
February1st to 15thNight
14%5%2331223456%
2159
16th to endNight
13%413312235%56%
1876
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
10%4245%24449%47%
1493
16th to endNight
6%42342435%10%52%
1539
June1st to 15thNight
311131335%9%65%
1485
16th to endNight
321341445%10%56%
1485
July1st to 15thNight
421232435%11%56%
1485
16th to endNight
211221346%11%60%
1576
August1st to 15thNight
111212249%71%
1485
16th to endNight
5%3133245%7%11%51%
1728
September1st to 15thNight
11%41432345%8%50%
1815
16th to endNight
7%313313448%58%
1815
October1st to 15thNight
8%312312346%61%
1889
16th to endNight
9%31211323367%
2112
November1st to 15thNight
6%42332323462%
2109
16th to endNight
12%42322243457%
2340
December1st to 15thNight
14%423322336%52%
2340
16th to endNight
14%5%24313345%50%
2496

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
33%36%20%27%8%
1612
16th to endDay
32%35%19%29%9%
1728
February1st to 15thDay
36%26%20%24%9%
1703
16th to endDay
35%27%20%21%12%
1598
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
44%5%10%16%16%7%
2138
16th to endDay
40%8%12%19%16%2
2226
June1st to 15thDay
26%7%15%27%19%3
2145
16th to endDay
31%412%26%20%4
2145
July1st to 15thDay
29%7%14%29%16%2
2006
16th to endDay
25%9%18%29%15%1
2129
August1st to 15thDay
16%6%15%33%25%3
2131
16th to endDay
32%9%17%25%13%2
2118
September1st to 15thDay
34%5%12%22%16%7%
1815
16th to endDay
28%5%8%22%25%9%
1815
October1st to 15thDay
28%410%21%19%15%
1730
16th to endDay
23%26%19%30%17%
1760
November1st to 15thDay
30%39%24%22%9%
1746
16th to endDay
30%25%18%30%12%
1620
December1st to 15thDay
38%36%20%25%5%
1620
16th to endDay
38%37%21%21%7%
1728
January1st to 15thNight
30%26%17%29%12%
2327
16th to endNight
30%35%18%27%14%
2496
February1st to 15thNight
33%36%16%24%15%
2169
16th to endNight
31%38%20%21%14%
1876
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
35%6%12%19%17%9%
1494
16th to endNight
28%6%16%24%19%4
1541
June1st to 15thNight
16%5%13%33%23%6%
1485
16th to endNight
23%5%13%27%23%6%
1485
July1st to 15thNight
22%5%14%35%18%4
1395
16th to endNight
14%7%19%35%20%2
1468
August1st to 15thNight
12%313%32%31%6%
1475
16th to endNight
23%6%14%31%18%4
1728
September1st to 15thNight
31%5%12%21%19%9%
1815
16th to endNight
24%49%21%27%12%
1815
October1st to 15thNight
23%49%23%20%17%
1889
16th to endNight
23%2417%29%23%
2112
November1st to 15thNight
26%37%23%25%13%
2109
16th to endNight
29%46%13%31%14%
2340
December1st to 15thNight
34%48%20%23%9%
2340
16th to endNight
35%38%21%21%9%
2496

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
13%13%36%27%8%
90
16th to endDay
11%9%50%17%11%
96
February1st to 15thDay
6%16%42%28%5%
90
16th to endDay
14%17%43%19%4
81
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
16%12%35%26%6%2
395
16th to endDay
16%5%29%28%17%2
437
June1st to 15thDay
6%115%40%27%9%
420
16th to endDay
6%311%36%30%10%
420
July1st to 15thDay
8%11%42%31%6%
400
16th to endDay
35%23%50%15%
445
August1st to 15thDay
3235%46%12%
418
16th to endDay
12%1433%38%9%
286
September1st to 15thDay
2117%46%32%
90
16th to endDay
6%120%44%27%
90
October1st to 15thDay
1114%36%38%7%
90
16th to endDay
15%313%38%25%4
96
November1st to 15thDay
26%320%34%12%3
90
16th to endDay
23%13%32%23%43
90
December1st to 15thDay
30%6%23%21%13%5%
90
16th to endDay
17%12%39%21%8%
96
January1st to 15thNight
15%8%33%34%7%
900
16th to endNight
15%10%34%33%5%
960
February1st to 15thNight
17%9%35%31%5%
761
16th to endNight
14%12%44%23%3
614
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%6%43%31%6%1
498
16th to endNight
7%332%36%17%1
515
June1st to 15thNight
4118%49%24%1
495
16th to endNight
417%44%29%3
495
July1st to 15thNight
5%13%46%32%2
465
16th to endNight
3447%40%4
522
August1st to 15thNight
1348%41%4
494
16th to endNight
7%6%38%41%5%
525
September1st to 15thNight
13%18%35%38%3
495
16th to endNight
8%11%34%38%5%
492
October1st to 15thNight
10%124%33%26%3
569
16th to endNight
10%6%27%34%19%
704
November1st to 15thNight
9%5%31%35%18%
709
16th to endNight
15%8%31%32%11%
900
December1st to 15thNight
17%7%34%33%6%
900
16th to endNight
17%8%33%32%7%
960
Page generated at 2017-05-02 07:43:28. Version ac04

Copyright 2017 A. Danko


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