Fort Griffin State Historic Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Griffin State Historic Site clear sky chart from 2005-11-06 to 2024-03-28.

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%
24299
31%
79798
20%
24198
61%
24198
40%
40689

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
41%
943
37%
3955
13%
926
54%
926
34%
1812
January11th to 20thNight
42%
947
34%
3925
14%
930
54%
930
35%
1738
January21st to endNight
40%
940
24%
4291
15%
927
55%
927
26%
2232
February1st to 10thNight
34%
760
33%
2280
14%
760
50%
760
37%
1258
February11th to 20thNight
33%
744
26%
2218
11%
740
45%
740
35%
1246
February21st to endNight
23%
628
32%
1884
8%
628
43%
628
36%
1013
March1st to 10thNight
32%
694
28%
2214
12%
694
47%
694
32%
1267
March11th to 20thNight
33%
570
28%
2090
15%
570
48%
570
31%
1091
March21st to endNight
32%
615
29%
2255
16%
615
51%
615
36%
1085
April1st to 10thNight
25%
540
28%
1967
11%
540
48%
540
38%
950
April11th to 20thNight
28%
533
29%
1777
12%
533
50%
533
35%
940
April21st to endNight
32%
540
33%
1674
15%
540
54%
540
45%
824
May1st to 10thNight
32%
540
30%
1620
15%
540
52%
540
39%
883
May11th to 20thNight
45%
531
23%
1594
16%
531
57%
531
37%
913
May21st to endNight
46%
583
27%
1745
18%
582
62%
582
43%
941
June1st to 10thNight
63%
540
24%
1620
20%
540
72%
540
47%
829
June11th to 20thNight
60%
540
28%
1620
24%
540
69%
540
54%
780
June21st to endNight
69%
540
29%
1620
30%
540
74%
540
51%
805
July1st to 10thNight
77%
525
22%
1575
25%
525
78%
525
42%
869
July11th to 20thNight
85%
522
35%
1566
39%
522
88%
522
62%
701
July21st to endNight
86%
591
34%
1673
40%
558
89%
558
58%
786
August1st to 10thNight
85%
537
38%
1601
42%
534
89%
534
60%
728
August11th to 20thNight
76%
534
31%
1775
38%
534
78%
534
42%
919
August21st to endNight
84%
594
31%
1980
36%
594
86%
594
52%
909
September1st to 10thNight
74%
540
27%
1970
33%
540
76%
540
38%
982
September11th to 20thNight
68%
540
26%
1980
27%
540
71%
540
31%
1071
September21st to endNight
70%
540
36%
1980
34%
540
77%
540
42%
940
October1st to 10thNight
64%
540
38%
1980
33%
540
73%
540
48%
876
October11th to 20thNight
54%
609
41%
2049
24%
609
69%
609
48%
954
October21st to endNight
48%
792
37%
2376
20%
792
59%
792
45%
1217
November1st to 10thNight
52%
870
32%
2350
15%
870
61%
870
50%
1244
November11th to 20thNight
50%
950
33%
2470
15%
950
59%
950
52%
1310
November21st to endNight
38%
950
33%
2470
13%
950
50%
950
41%
1451
December1st to 10thNight
45%
950
36%
2470
17%
950
56%
950
46%
1375
December11th to 20thNight
39%
949
34%
2862
15%
948
51%
948
37%
1597
December21st to endNight
38%
1038
21%
4322
13%
1026
51%
1026
30%
2153

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
9%42442445%6%58%
79258
Night
8%423323446%61%
80817
TransparencyDay
27%49%22%26%11%
78983
Night
25%48%21%27%15%
80612
SeeingDay
10%6%23%30%24%8%
14213
Night
9%6%31%39%14%1
24327

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
8%6%2442323460%
2847
11th to 20thDay
7%5%23222246%66%
2850
21st to endDay
15%8%24423335%51%
3327
February1st to 10thDay
11%5%2431335%6%58%
1900
11th to 20thDay
11%6%25%423345%56%
1849
21st to endDay
15%6%2321233458%
1570
March1st to 10thDay
13%42443346%7%49%
1966
11th to 20thDay
14%423423345%57%
2090
21st to endDay
8%4245%245%5%6%57%
2255
April1st to 10thDay
8%4133335%5%6%58%
1988
11th to 20thDay
11%424324345%58%
2134
21st to endDay
9%42443434460%
2285
May1st to 10thDay
9%3244345%47%56%
2340
11th to 20thDay
11%5%144245%5%7%54%
2302
21st to endDay
8%425%5%35%6%6%8%48%
2531
June1st to 10thDay
6%214435%5%5%8%57%
2340
11th to 20thDay
42134345%5%8%62%
2340
21st to endDay
6%21342445%7%62%
2340
July1st to 10thDay
7%3145%36%5%7%11%48%
2340
11th to 20thDay
42123235%5%8%64%
2340
21st to endDay
21134245%6%11%58%
2546
August1st to 10thDay
22134245%47%65%
2327
11th to 20thDay
6%3145%35%5%7%9%52%
2123
21st to endDay
5%3233246%5%9%58%
2376
September1st to 10thDay
10%42343345%5%56%
1990
11th to 20thDay
12%5%335%3445%7%50%
1980
21st to endDay
9%323332347%61%
1980
October1st to 10thDay
5%213424446%64%
1980
11th to 20thDay
9%31322334467%
1890
21st to endDay
11%41231223366%
1980
November1st to 10thDay
7%323323345%64%
1726
11th to 20thDay
6%31332335%6%65%
1710
21st to endDay
12%324423335%59%
1710
December1st to 10thDay
11%6%24323346%56%
1710
11th to 20thDay
9%4244245%46%56%
2161
21st to endDay
10%6%2442323460%
3135
January1st to 10thNight
11%412312335%63%
4108
11th to 20thNight
8%5%13222345%66%
4120
21st to endNight
12%8%24323335%54%
4371
February1st to 10thNight
10%424424346%58%
2280
11th to 20thNight
11%5%2442335%6%56%
2218
21st to endNight
11%5%2322324462%
1884
March1st to 10thNight
10%425%5%24446%54%
2214
11th to 20thNight
13%5%1432335%5%56%
2090
21st to endNight
6%42343445%6%61%
2255
April1st to 10thNight
6%424323348%61%
1967
11th to 20thNight
10%31332445%6%58%
1777
21st to endNight
7%31331335%6%64%
1674
May1st to 10thNight
7%423424447%59%
1620
11th to 20thNight
7%3244445%6%8%53%
1593
21st to endNight
6%3133245%7%10%56%
1745
June1st to 10thNight
42134246%7%9%58%
1620
11th to 20thNight
21123345%6%9%64%
1620
21st to endNight
4223333346%67%
1620
July1st to 10thNight
5%3234345%8%11%52%
1620
11th to 20thNight
311122335%8%71%
1620
21st to endNight
111233447%12%62%
1772
August1st to 10thNight
211232435%8%68%
1611
11th to 20thNight
43244345%5%9%55%
1775
21st to endNight
321332445%10%64%
1980
September1st to 10thNight
8%414424446%59%
1970
11th to 20thNight
10%425%4335%5%7%52%
1980
21st to endNight
7%31332345%5%63%
1980
October1st to 10thNight
6%312223447%66%
1980
11th to 20thNight
9%31221223470%
2049
21st to endNight
9%41332233467%
2376
November1st to 10thNight
8%313213335%67%
2350
11th to 20thNight
431332435%6%66%
2470
21st to endNight
13%413323446%57%
2470
December1st to 10thNight
9%413323346%61%
2470
11th to 20thNight
9%424423446%57%
3036
21st to endNight
9%5%24323445%59%
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
30%25%18%30%15%
2848
11th to 20thDay
22%27%19%36%13%
2850
21st to endDay
38%25%19%28%9%
3327
February1st to 10thDay
29%46%20%27%15%
1900
11th to 20thDay
33%35%19%25%14%
1859
21st to endDay
32%2414%27%22%
1570
March1st to 10thDay
34%48%14%27%13%
1966
11th to 20thDay
32%39%18%26%11%
2090
21st to endDay
29%49%21%24%13%
2255
April1st to 10thDay
26%49%22%23%15%
1988
11th to 20thDay
30%48%16%24%18%
2134
21st to endDay
28%47%19%31%10%
2285
May1st to 10thDay
30%5%9%21%24%11%
2340
11th to 20thDay
31%5%11%24%22%6%
2306
21st to endDay
33%6%13%25%19%4
2531
June1st to 10thDay
24%6%14%29%22%5%
2340
11th to 20thDay
19%6%10%30%26%9%
2340
21st to endDay
22%5%11%25%26%10%
2340
July1st to 10thDay
28%8%17%28%17%3
2276
11th to 20thDay
18%5%11%29%30%7%
2271
21st to endDay
17%7%14%34%25%2
2405
August1st to 10thDay
17%5%13%29%29%6%
2313
11th to 20thDay
28%7%13%26%22%5%
2123
21st to endDay
22%6%12%27%26%6%
2376
September1st to 10thDay
29%5%9%21%26%10%
1990
11th to 20thDay
35%6%8%18%24%9%
1980
21st to endDay
25%48%20%28%15%
1980
October1st to 10thDay
21%49%23%26%15%
1980
11th to 20thDay
23%36%16%30%21%
1890
21st to endDay
26%2421%29%19%
1980
November1st to 10thDay
23%37%25%27%15%
1726
11th to 20thDay
21%36%23%31%15%
1710
21st to endDay
31%25%21%27%15%
1710
December1st to 10thDay
31%46%21%28%10%
1710
11th to 20thDay
31%39%17%28%13%
2159
21st to endDay
32%2422%26%14%
3135
January1st to 10thNight
26%25%20%34%13%
4108
11th to 20thNight
23%37%20%30%18%
4120
21st to endNight
34%27%16%28%13%
4371
February1st to 10thNight
30%36%18%26%17%
2280
11th to 20thNight
30%47%17%24%17%
2218
21st to endNight
28%35%16%25%24%
1884
March1st to 10thNight
33%46%14%23%19%
2214
11th to 20thNight
31%38%21%24%14%
2090
21st to endNight
24%49%22%28%13%
2255
April1st to 10thNight
24%5%9%21%22%19%
1967
11th to 20thNight
27%5%11%17%21%19%
1777
21st to endNight
22%411%24%30%10%
1674
May1st to 10thNight
27%5%8%21%24%15%
1620
11th to 20thNight
29%6%14%22%20%9%
1594
21st to endNight
23%7%17%27%22%4
1746
June1st to 10thNight
19%7%16%30%23%5%
1620
11th to 20thNight
16%6%13%29%27%9%
1620
21st to endNight
19%5%10%26%27%13%
1620
July1st to 10thNight
24%8%13%29%22%5%
1575
11th to 20thNight
13%48%31%33%12%
1566
21st to endNight
14%6%14%32%31%4
1673
August1st to 10thNight
14%47%29%35%10%
1601
11th to 20thNight
25%5%11%26%26%7%
1775
21st to endNight
17%5%13%28%29%8%
1980
September1st to 10thNight
26%5%9%23%26%12%
1970
11th to 20thNight
31%6%12%20%22%10%
1980
21st to endNight
23%46%20%29%18%
1980
October1st to 10thNight
19%412%22%26%17%
1980
11th to 20thNight
21%25%18%27%27%
2049
21st to endNight
23%35%19%29%20%
2376
November1st to 10thNight
22%37%21%26%20%
2350
11th to 20thNight
20%46%23%29%18%
2470
21st to endNight
30%35%16%30%16%
2470
December1st to 10thNight
26%37%22%29%14%
2470
11th to 20thNight
29%36%20%27%16%
3037
21st to endNight
29%35%17%29%17%
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
10%13%38%30%9%
270
11th to 20thDay
15%11%30%31%11%1
270
21st to endDay
13%10%40%26%10%1
297
February1st to 10thDay
15%12%37%26%9%
270
11th to 20thDay
17%11%40%23%8%
270
21st to endDay
22%13%39%21%4
225
March1st to 10thDay
17%11%35%30%7%
270
11th to 20thDay
19%11%37%26%6%1
270
21st to endDay
13%14%41%22%9%1
285
April1st to 10thDay
10%12%43%24%10%1
248
11th to 20thDay
13%15%45%20%7%
412
21st to endDay
13%12%39%26%10%1
545
May1st to 10thDay
9%9%36%35%10%1
603
11th to 20thDay
14%5%28%34%15%4
625
21st to endDay
10%5%30%33%17%5%
679
June1st to 10thDay
7%114%43%28%6%
630
11th to 20thDay
3117%48%25%6%
630
21st to endDay
4111%38%34%11%
630
July1st to 10thDay
6%15%32%38%17%
621
11th to 20thDay
315%29%45%17%
618
21st to endDay
2424%48%21%
684
August1st to 10thDay
25%30%46%17%
625
11th to 20thDay
6%16%26%44%17%
437
21st to endDay
415%28%41%21%
495
September1st to 10thDay
10%320%41%26%
280
11th to 20thDay
6%16%23%42%22%
270
21st to endDay
13%27%26%35%17%
270
October1st to 10thDay
3310%39%35%10%
270
11th to 20thDay
10%5%30%34%17%4
270
21st to endDay
17%7%26%31%17%2
297
November1st to 10thDay
14%6%26%33%18%3
270
11th to 20thDay
12%9%29%27%18%4
270
21st to endDay
17%12%31%28%10%3
270
December1st to 10thDay
14%8%34%31%10%2
270
11th to 20thDay
9%9%40%31%11%
270
21st to endDay
17%10%40%24%9%
297
January1st to 10thNight
10%8%37%36%9%
950
11th to 20thNight
11%10%33%38%7%
950
21st to endNight
11%10%35%37%6%
949
February1st to 10thNight
13%9%41%33%4
760
11th to 20thNight
13%10%42%32%4
744
21st to endNight
14%14%48%21%3
628
March1st to 10thNight
12%12%40%32%4
694
11th to 20thNight
14%11%40%31%5%
570
21st to endNight
7%13%46%30%4
615
April1st to 10thNight
7%10%55%26%3
540
11th to 20thNight
11%11%48%29%2
533
21st to endNight
7%11%48%29%5%
540
May1st to 10thNight
8%8%49%30%5%
540
11th to 20thNight
8%5%37%39%10%1
531
21st to endNight
7%440%35%13%1
584
June1st to 10thNight
4226%47%20%1
540
11th to 20thNight
2231%56%9%
540
21st to endNight
5%219%53%19%2
540
July1st to 10thNight
5%18%46%37%2
525
11th to 20thNight
37%52%36%2
522
21st to endNight
25%53%38%2
591
August1st to 10thNight
26%55%37%1
537
11th to 20thNight
6%18%42%41%2
534
21st to endNight
416%42%43%4
594
September1st to 10thNight
10%110%43%34%3
540
11th to 20thNight
12%110%47%29%2
540
21st to endNight
9%214%48%25%2
540
October1st to 10thNight
8%224%44%22%1
540
11th to 20thNight
10%429%42%14%1
609
21st to endNight
12%7%30%36%14%1
792
November1st to 10thNight
10%430%41%14%1
870
11th to 20thNight
49%34%42%11%1
950
21st to endNight
15%7%36%30%12%1
950
December1st to 10thNight
12%6%34%40%7%
950
11th to 20thNight
14%7%35%36%7%
950
21st to endNight
11%7%39%35%7%
1045
Page generated at 2024-03-24 22:37:03. Version ac07

Copyright © 2024 Attilla Danko.


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