This page made possible by the sponsorship of: Texas Astronomical Society.

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 2020-06-03.

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%
19201
28%
57825
19%
19158
58%
19158
37%
32250

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%
1122
29%
2912
12%
1120
48%
1120
39%
1744
January16th to endNight
36%
1200
32%
3120
13%
1200
48%
1200
37%
1887
February1st to 15thNight
32%
956
25%
2724
10%
952
42%
952
31%
1654
February16th to endNight
23%
769
28%
2351
9%
769
38%
769
28%
1393
March1st to 15thNight
31%
675
26%
2475
15%
675
45%
675
25%
1446
March16th to endNight
34%
720
24%
2640
14%
720
48%
720
27%
1464
April1st to 15thNight
30%
674
26%
2467
14%
674
49%
674
29%
1307
April16th to endNight
36%
669
28%
2123
17%
669
52%
669
36%
1177
May1st to 15thNight
38%
675
23%
2025
16%
675
50%
675
33%
1201
May16th to endNight
49%
706
25%
2116
20%
705
60%
705
40%
1171
June1st to 15thNight
70%
637
25%
1912
25%
637
76%
637
51%
946
June16th to endNight
68%
630
25%
1890
27%
630
72%
630
46%
981
July1st to 15thNight
77%
600
24%
1800
27%
600
81%
600
47%
931
July16th to endNight
86%
660
31%
1882
38%
627
88%
627
56%
890
August1st to 15thNight
87%
620
36%
1852
42%
617
87%
617
60%
850
August16th to endNight
81%
669
28%
2202
32%
669
82%
669
42%
1124
September1st to 15thNight
71%
630
23%
2310
28%
630
73%
630
34%
1230
September16th to endNight
71%
627
32%
2310
32%
627
75%
627
38%
1165
October1st to 15thNight
59%
724
33%
2404
26%
724
66%
724
40%
1243
October16th to endNight
51%
896
35%
2688
21%
896
60%
896
43%
1417
November1st to 15thNight
48%
892
30%
2652
17%
892
58%
892
38%
1495
November16th to endNight
41%
1125
33%
2925
14%
1125
52%
1125
40%
1715
December1st to 15thNight
37%
1125
31%
2925
13%
1125
47%
1125
35%
1817
December16th to endNight
34%
1200
27%
3120
11%
1200
43%
1200
32%
2002

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%
58583
Night
10%413313347%55%
58021
TransparencyDay
33%5%10%22%20%6%
58283
Night
28%410%22%23%10%
57826
SeeingDay
12%6%21%28%23%7%
9113
Night
12%6%28%35%16%1
19205

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
15%6%23212235%52%
2016
16th to endDay
15%414212236%53%
2160
February1st to 15thDay
17%6%25%322225%48%
2140
16th to endDay
20%5%24312235%48%
2002
March1st to 15thDay
20%6%13324346%43%
2475
16th to endDay
14%6%25%424336%46%
2638
April1st to 15thDay
12%5%2442445%7%46%
2470
16th to endDay
12%5%14424447%47%
2768
May1st to 15thDay
13%5%35%5%24447%43%
2916
16th to endDay
10%5%345%35%46%8%42%
3054
June1st to 15thDay
5%314425%5%6%9%51%
2757
16th to endDay
6%2245%35%45%9%50%
2730
July1st to 15thDay
6%3145%25%5%7%9%47%
2730
16th to endDay
3213435%5%7%10%51%
2882
August1st to 15thDay
311233447%9%57%
2681
16th to endDay
5%315%435%6%8%9%46%
2699
September1st to 15thDay
11%31342346%8%49%
2310
16th to endDay
8%4145%2445%7%50%
2310
October1st to 15thDay
10%314324346%55%
2202
16th to endDay
12%31321223463%
2240
November1st to 15thDay
11%424423345%54%
2193
16th to endDay
12%413312235%59%
2025
December1st to 15thDay
17%5%2332234450%
2025
16th to endDay
19%6%24312345%47%
2160
January1st to 15thNight
13%413312235%57%
2912
16th to endNight
13%43321323457%
3120
February1st to 15thNight
15%5%24313235%52%
2714
16th to endNight
16%5%23312235%51%
2351
March1st to 15thNight
16%5%2421435%6%48%
2475
16th to endNight
11%5%14323347%52%
2640
April1st to 15thNight
9%423423447%53%
2467
16th to endNight
10%5%13313346%55%
2123
May1st to 15thNight
9%424424348%50%
2024
16th to endNight
6%42332335%11%53%
2115
June1st to 15thNight
41232336%9%62%
1912
16th to endNight
321341445%11%57%
1890
July1st to 15thNight
321241446%11%56%
1890
16th to endNight
111221346%10%63%
1990
August1st to 15thNight
112312249%68%
1862
16th to endNight
5%21232447%11%53%
2202
September1st to 15thNight
10%41432335%7%53%
2310
16th to endNight
8%313323447%57%
2310
October1st to 15thNight
9%313322346%58%
2404
16th to endNight
11%41221222364%
2688
November1st to 15thNight
8%5%2432333458%
2652
16th to endNight
12%41321244457%
2925
December1st to 15thNight
14%5%23322336%52%
2925
16th to endNight
15%6%14323345%48%
3120

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
35%37%19%25%8%
2017
16th to endDay
33%35%20%28%8%
2160
February1st to 15thDay
39%37%19%21%8%
2141
16th to endDay
41%26%18%19%11%
2002
March1st to 15thDay
42%47%17%20%8%
2475
16th to endDay
39%410%19%19%5%
2640
April1st to 15thDay
36%5%10%21%16%9%
2470
16th to endDay
35%5%8%18%25%5%
2768
May1st to 15thDay
40%5%10%18%17%6%
2916
16th to endDay
37%7%12%22%17%2
3058
June1st to 15thDay
27%7%15%28%17%3
2757
16th to endDay
30%5%13%26%20%4
2730
July1st to 15thDay
29%8%16%29%14%1
2591
16th to endDay
22%8%17%32%16%1
2727
August1st to 15thDay
20%6%15%31%22%3
2667
16th to endDay
29%8%16%27%14%2
2699
September1st to 15thDay
33%5%11%23%18%7%
2310
16th to endDay
31%5%9%22%22%7%
2310
October1st to 15thDay
29%410%21%19%14%
2202
16th to endDay
25%36%17%28%18%
2240
November1st to 15thDay
32%39%23%22%8%
2193
16th to endDay
29%26%20%30%10%
2025
December1st to 15thDay
36%47%20%24%6%
2025
16th to endDay
40%36%20%21%7%
2160
January1st to 15thNight
31%37%18%27%12%
2912
16th to endNight
32%35%18%27%13%
3120
February1st to 15thNight
36%37%16%22%13%
2724
16th to endNight
36%38%18%20%13%
2351
March1st to 15thNight
37%5%8%15%21%12%
2475
16th to endNight
32%5%11%20%23%6%
2640
April1st to 15thNight
30%5%10%22%18%12%
2467
16th to endNight
29%49%21%25%9%
2123
May1st to 15thNight
32%6%12%21%19%7%
2025
16th to endNight
26%6%16%27%20%3
2117
June1st to 15thNight
17%6%13%34%22%5%
1912
16th to endNight
21%5%12%29%24%5%
1890
July1st to 15thNight
20%6%16%36%16%3
1800
16th to endNight
13%7%18%36%21%2
1882
August1st to 15thNight
14%414%32%27%6%
1852
16th to endNight
22%6%14%31%20%4
2202
September1st to 15thNight
29%5%12%21%22%8%
2310
16th to endNight
25%5%10%22%25%9%
2310
October1st to 15thNight
25%410%23%19%15%
2404
16th to endNight
26%2416%27%22%
2688
November1st to 15thNight
30%37%21%24%12%
2652
16th to endNight
28%46%15%31%13%
2925
December1st to 15thNight
34%48%19%23%9%
2925
16th to endNight
38%37%19%20%10%
3120

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
21%10%34%26%7%
225
16th to endDay
15%11%42%18%10%1
240
February1st to 15thDay
17%18%39%20%4
225
16th to endDay
26%19%36%13%2
201
March1st to 15thDay
29%16%33%16%3
225
16th to endDay
13%14%42%22%7%
240
April1st to 15thDay
17%16%32%25%6%
229
16th to endDay
16%12%34%26%9%1
540
May1st to 15thDay
13%10%32%31%8%2
693
16th to endDay
13%430%30%17%3
757
June1st to 15thDay
6%114%42%27%7%
656
16th to endDay
6%213%35%32%9%
645
July1st to 15thDay
6%9%34%36%13%
625
16th to endDay
2427%49%15%
675
August1st to 15thDay
4332%45%12%
624
16th to endDay
8%5%30%40%14%
483
September1st to 15thDay
6%17%45%29%
225
16th to endDay
13%5%25%39%15%
225
October1st to 15thDay
8%119%28%34%7%
225
16th to endDay
20%422%29%19%4
240
November1st to 15thDay
24%5%33%22%10%4
225
16th to endDay
16%12%31%28%8%2
225
December1st to 15thDay
21%7%35%21%11%2
225
16th to endDay
25%12%34%21%7%
240
January1st to 15thNight
15%8%33%33%8%
1125
16th to endNight
17%10%33%33%5%
1200
February1st to 15thNight
19%9%35%29%5%
956
16th to endNight
18%12%43%22%3
769
March1st to 15thNight
18%10%36%29%5%
675
16th to endNight
12%10%40%29%5%
720
April1st to 15thNight
10%11%45%27%5%
674
16th to endNight
14%6%40%30%6%
669
May1st to 15thNight
10%5%41%34%7%1
675
16th to endNight
7%334%36%16%1
707
June1st to 15thNight
418%51%22%1
637
16th to endNight
420%46%25%2
630
July1st to 15thNight
411%45%34%4
600
16th to endNight
3449%38%4
660
August1st to 15thNight
2350%39%4
620
16th to endNight
6%6%40%40%5%
669
September1st to 15thNight
12%17%35%39%4
630
16th to endNight
9%13%37%34%5%
627
October1st to 15thNight
11%123%34%25%3
724
16th to endNight
14%5%27%33%18%1
896
November1st to 15thNight
11%5%31%35%15%
892
16th to endNight
14%8%32%31%12%
1125
December1st to 15thNight
17%7%34%32%6%
1125
16th to endNight
18%8%34%31%6%
1200
Page generated at 2020-06-04 02:18:56. Version ac04

Copyright 2020 A. Danko


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