Katy
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Katy clear sky chart from 2005-11-06 to 2024-01-13.

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
53%
23679
24%
74256
19%
23623
59%
23623
32%
43662

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
36%
949
27%
2458
12%
946
44%
946
32%
1577
January11th to 20thNight
37%
915
24%
2379
11%
915
43%
915
30%
1558
January21st to endNight
36%
990
26%
2574
10%
990
44%
990
29%
1697
February1st to 10thNight
30%
789
22%
2229
9%
789
38%
789
23%
1511
February11th to 20thNight
34%
704
20%
2098
10%
700
42%
700
27%
1339
February21st to endNight
24%
453
23%
1637
9%
453
38%
453
18%
1044
March1st to 10thNight
32%
540
24%
1980
13%
540
45%
540
23%
1217
March11th to 20thNight
36%
540
21%
1980
15%
540
45%
540
22%
1231
March21st to endNight
37%
594
24%
2178
18%
594
49%
594
27%
1247
April1st to 10thNight
37%
540
22%
1980
16%
540
48%
540
22%
1208
April11th to 20thNight
37%
533
23%
1843
16%
533
49%
533
26%
1108
April21st to endNight
37%
540
25%
1800
20%
540
48%
540
25%
1090
May1st to 10thNight
42%
540
22%
1714
18%
540
50%
540
28%
1057
May11th to 20thNight
52%
531
23%
1594
22%
531
57%
531
35%
946
May21st to endNight
61%
583
23%
1745
22%
582
66%
582
36%
1000
June1st to 10thNight
79%
540
24%
1620
28%
540
80%
540
49%
826
June11th to 20thNight
76%
540
22%
1620
26%
540
79%
540
48%
820
June21st to endNight
72%
540
18%
1620
22%
540
74%
540
36%
952
July1st to 10thNight
77%
525
16%
1575
20%
525
77%
525
36%
909
July11th to 20thNight
85%
522
22%
1566
27%
522
86%
522
49%
810
July21st to endNight
85%
591
20%
1673
24%
558
86%
558
44%
876
August1st to 10thNight
91%
537
26%
1601
30%
534
92%
534
62%
724
August11th to 20thNight
85%
534
23%
1658
26%
534
85%
534
44%
861
August21st to endNight
79%
594
18%
2074
21%
594
81%
594
33%
1170
September1st to 10thNight
78%
540
18%
1980
22%
540
78%
540
32%
1079
September11th to 20thNight
69%
540
22%
1980
26%
540
69%
540
27%
1146
September21st to endNight
75%
540
28%
1980
31%
540
77%
540
36%
1004
October1st to 10thNight
76%
602
34%
2042
33%
602
77%
602
47%
977
October11th to 20thNight
63%
720
34%
2160
25%
720
68%
720
42%
1184
October21st to endNight
55%
792
34%
2376
24%
792
61%
792
40%
1294
November1st to 10thNight
61%
740
29%
2220
23%
740
65%
740
38%
1258
November11th to 20thNight
53%
760
28%
2280
21%
760
58%
760
33%
1354
November21st to endNight
44%
845
27%
2365
16%
845
51%
845
31%
1498
December1st to 10thNight
42%
950
26%
2470
15%
950
48%
950
29%
1669
December11th to 20thNight
38%
948
23%
2882
11%
948
43%
948
23%
1915
December21st to endNight
35%
1038
15%
4325
11%
1026
42%
1026
19%
2506

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%8%41%
74937
Night
12%5%2442445%7%48%
74824
TransparencyDay
42%411%20%17%7%
74662
Night
36%313%22%18%9%
74619
SeeingDay
12%5%17%25%26%15%
13695
Night
15%5%21%34%23%3
23690

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
19%6%24335%446%44%
1707
11th to 20thDay
20%6%35%43344444%
1638
21st to endDay
18%7%35%43435%6%42%
1782
February1st to 10thDay
23%8%35%5%34335%38%
1746
11th to 20thDay
20%9%36%5%33446%38%
1749
21st to endDay
20%7%35%443345%40%
1616
March1st to 10thDay
21%7%36%6%35%447%34%
1980
11th to 20thDay
18%8%36%6%24445%40%
1980
21st to endDay
16%6%45%4245%5%6%43%
2178
April1st to 10thDay
15%8%38%5%45%5%5%6%38%
1980
11th to 20thDay
18%7%26%6%35%446%40%
2065
21st to endDay
11%5%36%6%35%5%6%6%44%
2160
May1st to 10thDay
9%6%38%6%35%5%6%7%41%
2240
11th to 20thDay
9%6%26%7%45%6%5%8%41%
2302
21st to endDay
9%7%47%7%38%7%7%10%31%
2531
June1st to 10thDay
5%325%7%36%6%6%10%45%
2340
11th to 20thDay
5%3247%47%7%8%10%43%
2340
21st to endDay
6%6%36%9%6%9%8%8%10%29%
2340
July1st to 10thDay
11%425%6%47%8%10%11%31%
2340
11th to 20thDay
5%326%7%5%8%8%9%11%35%
2340
21st to endDay
5%425%6%47%8%10%13%36%
2546
August1st to 10thDay
42146%46%7%9%12%45%
2328
11th to 20thDay
5%425%7%47%7%7%12%41%
2239
21st to endDay
7%427%8%36%9%7%10%37%
2278
September1st to 10thDay
6%5%37%7%47%6%8%9%39%
1980
11th to 20thDay
11%7%36%8%5%7%5%6%8%35%
1980
21st to endDay
7%5%25%7%35%6%7%8%44%
1980
October1st to 10thDay
6%415%5%345%5%7%55%
1898
11th to 20thDay
11%435%435%447%51%
1800
21st to endDay
12%4345%33346%53%
1980
November1st to 10thDay
11%5%35%435%35%8%47%
1858
11th to 20thDay
12%6%25%5%245%5%6%47%
1900
21st to endDay
16%7%36%6%3445%6%41%
1810
December1st to 10thDay
16%8%35%6%34347%40%
1710
11th to 20thDay
15%7%36%6%45%45%5%42%
2161
21st to endDay
16%6%35%434446%46%
3135
January1st to 10thNight
19%6%2442335%7%46%
2458
11th to 20thNight
20%7%24422245%47%
2379
21st to endNight
18%6%34424446%45%
2574
February1st to 10thNight
20%8%46%5%23346%39%
2229
11th to 20thNight
21%7%345%23336%45%
2098
21st to endNight
21%8%25%5%24445%40%
1637
March1st to 10thNight
19%7%25%42346%6%42%
1980
11th to 20thNight
17%8%25%5%3445%6%40%
1980
21st to endNight
14%5%35%5%23447%49%
2178
April1st to 10thNight
13%7%345%35%5%7%7%41%
1980
11th to 20thNight
16%6%35%5%235%46%44%
1843
21st to endNight
13%7%25%5%34447%45%
1800
May1st to 10thNight
13%5%25%5%345%6%9%42%
1714
11th to 20thNight
11%425%5%3346%10%46%
1593
21st to endNight
6%5%245%45%6%6%11%48%
1745
June1st to 10thNight
431332445%10%59%
1620
11th to 20thNight
5%3134345%5%11%56%
1620
21st to endNight
5%4346%26%6%7%11%45%
1620
July1st to 10thNight
6%325%5%346%8%11%47%
1620
11th to 20thNight
3313425%5%7%12%56%
1620
21st to endNight
3124425%6%7%11%55%
1772
August1st to 10thNight
111332246%11%67%
1611
11th to 20thNight
3214426%47%12%54%
1658
21st to endNight
4225%6%45%5%6%11%49%
2074
September1st to 10thNight
5%4246%346%7%9%49%
1980
11th to 20thNight
11%436%5%35%46%8%45%
1980
21st to endNight
8%42432447%9%53%
1980
October1st to 10thNight
4313433448%62%
2042
11th to 20thNight
11%413324446%59%
2160
21st to endNight
11%5%2432324460%
2376
November1st to 10thNight
10%5%24424447%54%
2220
11th to 20thNight
13%5%25%43445%6%50%
2280
21st to endNight
17%6%35%324446%46%
2365
December1st to 10thNight
19%7%35%42435%6%42%
2470
11th to 20thNight
16%8%35%5%25%45%5%41%
3036
21st to endNight
16%7%25%423445%46%
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
44%26%16%22%9%
1708
11th to 20thDay
45%25%16%20%12%
1638
21st to endDay
45%25%16%19%13%
1782
February1st to 10thDay
51%2414%16%12%
1746
11th to 20thDay
50%27%13%18%9%
1759
21st to endDay
49%27%16%16%10%
1616
March1st to 10thDay
53%27%13%18%6%
1980
11th to 20thDay
47%37%12%21%10%
1980
21st to endDay
43%28%17%22%8%
2178
April1st to 10thDay
49%26%18%16%8%
1980
11th to 20thDay
46%28%17%18%9%
2065
21st to endDay
41%37%21%21%7%
2160
May1st to 10thDay
43%39%20%16%8%
2240
11th to 20thDay
42%310%23%18%3
2306
21st to endDay
46%412%22%14%1
2531
June1st to 10thDay
35%5%16%26%17%2
2340
11th to 20thDay
34%5%15%28%16%2
2340
21st to endDay
47%7%15%21%9%1
2340
July1st to 10thDay
42%7%21%23%6%1
2276
11th to 20thDay
40%5%21%23%10%
2271
21st to endDay
35%7%24%28%5%1
2405
August1st to 10thDay
30%7%21%31%10%
2314
11th to 20thDay
37%8%20%25%10%2
2239
21st to endDay
41%6%18%24%10%2
2278
September1st to 10thDay
39%7%16%19%14%5%
1980
11th to 20thDay
47%412%18%15%4
1980
21st to endDay
36%412%19%18%10%
1980
October1st to 10thDay
29%37%26%22%13%
1898
11th to 20thDay
35%35%20%22%16%
1800
21st to endDay
35%25%17%24%17%
1980
November1st to 10thDay
37%49%19%23%9%
1858
11th to 20thDay
39%38%16%22%12%
1900
21st to endDay
46%36%17%17%12%
1810
December1st to 10thDay
46%27%20%18%7%
1710
11th to 20thDay
46%16%15%23%10%
2159
21st to endDay
42%25%18%22%12%
3135
January1st to 10thNight
41%16%18%22%13%
2458
11th to 20thNight
42%15%17%20%14%
2379
21st to endNight
43%25%17%19%15%
2574
February1st to 10thNight
49%26%13%17%13%
2229
11th to 20thNight
44%27%17%18%13%
2098
21st to endNight
48%26%15%15%13%
1637
March1st to 10thNight
44%29%18%17%9%
1980
11th to 20thNight
45%210%14%20%9%
1980
21st to endNight
38%312%17%21%10%
2178
April1st to 10thNight
43%39%20%15%9%
1980
11th to 20thNight
41%210%16%16%13%
1843
21st to endNight
42%38%21%18%8%
1800
May1st to 10thNight
40%411%20%16%9%
1714
11th to 20thNight
34%414%24%19%4
1594
21st to endNight
31%5%19%31%13%1
1746
June1st to 10thNight
23%320%34%20%1
1620
11th to 20thNight
23%319%34%17%4
1620
21st to endNight
32%5%23%27%12%1
1620
July1st to 10thNight
31%6%28%28%7%
1575
11th to 20thNight
20%6%32%32%10%
1566
21st to endNight
22%8%30%35%6%
1673
August1st to 10thNight
13%431%39%12%
1601
11th to 20thNight
22%7%31%31%8%1
1658
21st to endNight
30%8%24%28%8%2
2074
September1st to 10thNight
30%6%23%21%15%4
1980
11th to 20thNight
37%5%15%24%15%4
1980
21st to endNight
28%415%23%20%10%
1980
October1st to 10thNight
23%212%30%20%13%
2042
11th to 20thNight
29%37%23%23%15%
2160
21st to endNight
30%26%18%24%21%
2376
November1st to 10thNight
32%310%23%22%10%
2220
11th to 20thNight
36%39%20%20%12%
2280
21st to endNight
41%28%20%18%11%
2365
December1st to 10thNight
45%27%21%15%10%
2470
11th to 20thNight
46%26%12%19%14%
3037
21st to endNight
42%26%15%27%8%
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
21%11%34%26%6%3
270
11th to 20thDay
21%9%28%29%11%1
246
21st to endDay
19%13%35%24%8%
264
February1st to 10thDay
28%11%28%23%9%1
240
11th to 20thDay
25%14%32%23%5%1
240
21st to endDay
24%14%38%20%4
198
March1st to 10thDay
22%14%35%19%10%
240
11th to 20thDay
16%11%45%21%5%3
240
21st to endDay
19%13%33%23%12%1
264
April1st to 10thDay
19%9%36%26%9%
240
11th to 20thDay
25%11%24%25%13%1
343
21st to endDay
15%9%30%31%14%2
420
May1st to 10thDay
13%9%31%28%18%1
503
11th to 20thDay
12%325%34%23%3
625
21st to endDay
8%419%39%24%5%
679
June1st to 10thDay
6%27%32%37%16%
630
11th to 20thDay
7%18%34%37%13%
630
21st to endDay
10%28%21%35%24%
630
July1st to 10thDay
6%25%22%37%27%
621
11th to 20thDay
41314%41%37%
618
21st to endDay
41317%42%33%
684
August1st to 10thDay
4317%42%34%
626
11th to 20thDay
6%1214%41%36%
553
21st to endDay
8%26%12%30%43%
397
September1st to 10thDay
9%1214%41%33%
270
11th to 20thDay
10%16%19%35%29%
270
21st to endDay
10%2421%41%22%
270
October1st to 10thDay
7%27%29%43%12%
270
11th to 20thDay
10%314%31%26%16%
270
21st to endDay
20%6%24%21%24%6%
297
November1st to 10thDay
11%5%16%34%24%10%
270
11th to 20thDay
14%6%22%35%18%4
270
21st to endDay
19%13%29%26%10%4
270
December1st to 10thDay
16%9%29%25%15%6%
270
11th to 20thDay
21%15%27%28%7%2
270
21st to endDay
19%8%35%26%9%2
297
January1st to 10thNight
22%8%29%32%9%
950
11th to 20thNight
23%9%26%33%8%
915
21st to endNight
21%9%31%33%7%
990
February1st to 10thNight
25%9%30%30%6%
789
11th to 20thNight
25%8%30%31%7%
704
21st to endNight
24%12%35%26%3
453
March1st to 10thNight
21%8%36%30%6%
540
11th to 20thNight
21%8%31%33%7%
540
21st to endNight
17%8%34%33%8%1
594
April1st to 10thNight
16%7%36%36%5%
540
11th to 20thNight
20%8%30%31%11%
533
21st to endNight
17%7%34%31%10%
540
May1st to 10thNight
14%6%33%39%8%
540
11th to 20thNight
12%327%41%15%3
531
21st to endNight
7%322%43%23%2
584
June1st to 10thNight
5%19%46%35%3
540
11th to 20thNight
419%49%34%2
540
21st to endNight
6%18%32%46%7%
540
July1st to 10thNight
6%431%50%9%
525
11th to 20thNight
41224%60%9%
522
21st to endNight
21330%57%8%
591
August1st to 10thNight
11131%59%7%
537
11th to 20thNight
3228%58%8%
534
21st to endNight
5%15%22%58%10%
594
September1st to 10thNight
6%1325%55%9%
540
11th to 20thNight
13%1426%50%6%
540
21st to endNight
9%8%31%45%7%
540
October1st to 10thNight
5%28%35%43%6%
602
11th to 20thNight
11%118%43%24%2
720
21st to endNight
12%6%22%37%21%3
792
November1st to 10thNight
12%318%40%25%2
740
11th to 20thNight
15%7%19%38%20%1
760
21st to endNight
20%5%27%33%13%2
845
December1st to 10thNight
21%6%25%32%15%1
950
11th to 20thNight
22%8%26%35%9%1
950
21st to endNight
22%7%29%32%9%1
1045
Page generated at 2024-01-10 09:16:11. Version ac07

Copyright 2024 Attilla Danko


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