Houston
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Houston 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
55%
16046
23%
48847
18%
16000
59%
16000
31%
29483

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%
974
23%
2522
11%
970
44%
970
29%
1670
January16th to endNight
38%
1040
24%
2704
11%
1040
44%
1040
29%
1798
February1st to 15thNight
35%
842
21%
2367
10%
837
42%
837
25%
1594
February16th to endNight
32%
540
25%
1858
12%
540
44%
540
23%
1154
March1st to 15thNight
37%
540
25%
1980
17%
540
48%
540
22%
1226
March16th to endNight
44%
576
22%
2112
18%
576
53%
576
27%
1191
April1st to 15thNight
41%
539
21%
1941
16%
539
50%
539
24%
1172
April16th to endNight
40%
540
22%
1800
18%
540
47%
540
24%
1128
May1st to 15thNight
44%
539
19%
1718
17%
539
50%
539
26%
1050
May16th to endNight
62%
562
23%
1685
25%
561
66%
561
34%
979
June1st to 15thNight
79%
540
20%
1620
22%
540
81%
540
47%
826
June16th to endNight
75%
540
16%
1620
20%
540
76%
540
33%
988
July1st to 15thNight
79%
510
18%
1530
22%
510
79%
510
37%
883
July16th to endNight
84%
564
19%
1594
23%
531
85%
531
36%
919
August1st to 15thNight
91%
539
26%
1613
30%
536
91%
536
55%
773
August16th to endNight
76%
573
16%
1932
18%
573
76%
573
27%
1199
September1st to 15thNight
72%
540
17%
1980
20%
540
73%
540
28%
1149
September16th to endNight
74%
537
28%
1980
32%
537
75%
537
30%
1104
October1st to 15thNight
76%
661
31%
2101
28%
661
77%
661
44%
1083
October16th to endNight
64%
768
36%
2304
27%
768
69%
768
44%
1218
November1st to 15thNight
62%
760
27%
2280
22%
760
64%
760
34%
1328
November16th to endNight
51%
807
33%
2367
22%
807
59%
807
35%
1371
December1st to 15thNight
41%
975
23%
2535
13%
975
46%
975
25%
1749
December16th to endNight
36%
1040
19%
2704
9%
1040
40%
1040
23%
1931

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%36%6%35%5%6%7%36%
49389
Night
11%5%2442345%7%48%
49045
TransparencyDay
44%7%11%16%14%6%
49089
Night
34%6%13%20%16%8%
48850
SeeingDay
12%316%26%26%14%
5847
Night
13%420%32%25%3
16049

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
19%6%2442444441%
1746
16th to endDay
18%6%35%423235%43%
1872
February1st to 15thDay
20%8%36%42324339%
1832
16th to endDay
21%8%24423335%38%
1759
March1st to 15thDay
22%8%24424336%36%
1980
16th to endDay
16%6%35%5%2435%6%39%
2110
April1st to 15thDay
14%6%45%5%3445%7%38%
2004
16th to endDay
13%6%36%5%35%45%6%36%
2160
May1st to 15thDay
11%7%37%7%35%6%6%7%33%
2229
16th to endDay
8%6%36%9%37%6%8%9%30%
2430
June1st to 15thDay
5%426%7%5%7%7%8%9%34%
2340
16th to endDay
6%5%38%9%5%11%9%7%8%24%
2340
July1st to 15thDay
9%437%7%5%8%7%9%10%26%
2340
16th to endDay
6%438%9%5%8%8%8%11%25%
2466
August1st to 15thDay
32147%5%7%8%9%13%35%
2335
16th to endDay
8%427%7%5%7%7%8%8%29%
2265
September1st to 15thDay
9%5%26%7%47%7%7%8%32%
1980
16th to endDay
9%6%27%6%45%6%6%8%36%
1980
October1st to 15thDay
7%425%5%335%5%5%49%
1845
16th to endDay
9%414423345%56%
1920
November1st to 15thDay
10%5%25%6%35%46%7%41%
1908
16th to endDay
14%5%25%41433449%
1921
December1st to 15thDay
18%7%36%6%34446%34%
1755
16th to endDay
18%9%36%6%23446%33%
1872
January1st to 15thNight
19%6%24323345%44%
2522
16th to endNight
19%6%24423336%44%
2704
February1st to 15thNight
18%7%36%423335%42%
2360
16th to endNight
15%7%35%5%23335%44%
1858
March1st to 15thNight
19%7%2332235%6%41%
1980
16th to endNight
10%5%34424445%50%
2112
April1st to 15thNight
13%4344335%5%8%43%
1941
16th to endNight
15%5%245%24447%42%
1800
May1st to 15thNight
9%6%25%5%25%5%6%9%42%
1717
16th to endNight
5%423435%47%11%47%
1683
June1st to 15thNight
321332246%10%58%
1620
16th to endNight
4325%435%5%8%12%44%
1620
July1st to 15thNight
5%3235%25%36%11%50%
1620
16th to endNight
3213425%6%7%11%49%
1702
August1st to 15thNight
11222337%12%62%
1623
16th to endNight
5%415%5%35%6%7%13%42%
1932
September1st to 15thNight
6%5%25%42347%9%46%
1980
16th to endNight
7%5%1443446%9%49%
1980
October1st to 15thNight
5%31332245%6%62%
2101
16th to endNight
7%31332323463%
2304
November1st to 15thNight
9%5%2432345%7%51%
2280
16th to endNight
12%5%13323345%55%
2367
December1st to 15thNight
16%7%35%5%23345%40%
2535
16th to endNight
19%8%35%5%3334437%
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
46%46%14%19%9%
1747
16th to endDay
44%35%15%18%12%
1872
February1st to 15thDay
50%36%13%15%10%
1833
16th to endDay
49%46%13%16%9%
1759
March1st to 15thDay
49%5%7%11%18%6%
1980
16th to endDay
44%48%14%21%6%
2112
April1st to 15thDay
45%5%7%16%16%8%
2004
16th to endDay
46%5%8%16%14%7%
2160
May1st to 15thDay
48%7%10%13%13%7%
2229
16th to endDay
44%8%13%18%12%2
2434
June1st to 15thDay
40%9%15%17%14%1
2340
16th to endDay
49%12%14%16%6%
2340
July1st to 15thDay
45%11%19%18%5%
2201
16th to endDay
45%13%19%18%2
2311
August1st to 15thDay
36%11%19%26%6%
2321
16th to endDay
45%14%16%15%6%1
2265
September1st to 15thDay
43%11%15%15%9%3
1980
16th to endDay
42%8%12%15%15%5%
1980
October1st to 15thDay
34%6%10%19%14%14%
1845
16th to endDay
31%36%12%28%18%
1920
November1st to 15thDay
39%6%11%16%17%7%
1908
16th to endDay
38%4413%21%15%
1921
December1st to 15thDay
50%48%15%14%7%
1755
16th to endDay
51%5%6%14%14%6%
1872
January1st to 15thNight
41%36%14%21%11%
2522
16th to endNight
41%36%15%18%13%
2704
February1st to 15thNight
45%47%12%17%13%
2370
16th to endNight
43%36%15%18%12%
1858
March1st to 15thNight
42%48%16%18%9%
1980
16th to endNight
35%414%15%20%9%
2112
April1st to 15thNight
38%6%9%18%16%10%
1941
16th to endNight
41%5%11%17%14%9%
1800
May1st to 15thNight
35%8%13%19%13%9%
1718
16th to endNight
29%7%19%25%13%3
1685
June1st to 15thNight
20%6%21%28%22%1
1620
16th to endNight
30%10%22%26%10%
1620
July1st to 15thNight
29%7%27%29%6%
1530
16th to endNight
23%12%28%31%3
1594
August1st to 15thNight
14%6%29%39%9%
1613
16th to endNight
32%12%24%24%5%1
1932
September1st to 15thNight
31%9%21%20%12%3
1980
16th to endNight
29%9%14%21%18%6%
1980
October1st to 15thNight
21%6%11%27%19%13%
2101
16th to endNight
25%36%16%26%21%
2304
November1st to 15thNight
31%6%13%22%18%7%
2280
16th to endNight
32%47%17%22%15%
2367
December1st to 15thNight
45%5%8%17%14%8%
2535
16th to endNight
49%47%14%14%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
25%5%27%31%6%3
135
16th to endDay
17%8%36%27%10%
144
February1st to 15thDay
27%8%31%26%41
135
16th to endDay
19%11%41%23%6%
100
March1st to 15thDay
35%7%36%13%6%
90
16th to endDay
19%6%33%23%12%4
96
April1st to 15thDay
16%13%18%34%15%1
123
16th to endDay
21%5%27%24%19%1
270
May1st to 15thDay
13%8%32%28%15%1
366
16th to endDay
11%227%35%18%3
517
June1st to 15thDay
7%10%34%35%11%
495
16th to endDay
10%18%29%32%18%
495
July1st to 15thDay
7%18%26%35%21%
475
16th to endDay
5%1323%37%28%
515
August1st to 15thDay
4318%43%30%
488
16th to endDay
17%311%36%30%
305
September1st to 15thDay
8%326%31%29%
135
16th to endDay
6%318%37%34%
135
October1st to 15thDay
48%30%38%17%
135
16th to endDay
15%219%26%27%9%
144
November1st to 15thDay
17%120%33%20%5%
135
16th to endDay
14%325%33%14%8%
135
December1st to 15thDay
22%421%30%12%8%
135
16th to endDay
31%10%28%25%4
144
January1st to 15thNight
22%7%28%30%10%
975
16th to endNight
20%9%27%34%8%
1040
February1st to 15thNight
21%8%28%32%8%
842
16th to endNight
19%7%35%30%6%
540
March1st to 15thNight
22%7%30%32%7%
540
16th to endNight
11%6%33%36%11%
576
April1st to 15thNight
14%5%33%36%9%
539
16th to endNight
18%6%30%32%12%
540
May1st to 15thNight
12%6%32%39%9%
540
16th to endNight
6%123%43%22%1
563
June1st to 15thNight
48%48%35%2
540
16th to endNight
5%16%35%45%5%
540
July1st to 15thNight
5%433%47%8%
510
16th to endNight
3227%55%10%
564
August1st to 15thNight
225%59%11%
539
16th to endNight
8%322%54%10%
573
September1st to 15thNight
8%16%20%53%9%
540
16th to endNight
9%7%25%50%7%
537
October1st to 15thNight
7%10%34%41%5%
661
16th to endNight
9%319%34%29%3
768
November1st to 15thNight
11%317%38%25%2
760
16th to endNight
14%5%24%33%21%1
807
December1st to 15thNight
19%6%24%31%16%
975
16th to endNight
24%7%25%30%10%
1040
Page generated at 2018-02-23 10:21:34. Version ac04

Copyright 2018 A. Danko


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