Fort Clinch State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Clinch State Park 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
58%
24704
20%
80147
16%
24617
63%
24617
26%
50406

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
39%
752
22%
4002
13%
737
52%
737
17%
2255
January11th to 20thNight
49%
753
23%
4023
19%
740
59%
740
17%
2364
January21st to endNight
36%
825
14%
4455
12%
814
49%
814
14%
2691
February1st to 10thNight
44%
760
20%
2314
14%
760
51%
760
25%
1486
February11th to 20thNight
42%
740
21%
2218
11%
739
53%
739
27%
1391
February21st to endNight
51%
628
23%
1801
17%
628
56%
628
31%
1126
March1st to 10thNight
54%
760
28%
2090
20%
760
61%
760
38%
1234
March11th to 20thNight
53%
760
25%
2090
16%
760
61%
760
35%
1268
March21st to endNight
53%
821
24%
2256
14%
821
61%
821
37%
1352
April1st to 10thNight
59%
720
24%
1980
17%
720
64%
720
36%
1201
April11th to 20thNight
57%
711
25%
1870
17%
711
61%
711
38%
1147
April21st to endNight
70%
707
28%
1787
19%
707
74%
707
46%
1034
May1st to 10thNight
70%
540
28%
1620
21%
540
74%
540
44%
857
May11th to 20thNight
70%
531
18%
1592
15%
531
71%
531
33%
962
May21st to endNight
73%
582
20%
1744
17%
582
74%
582
31%
1085
June1st to 10thNight
71%
540
14%
1620
12%
540
71%
540
26%
1068
June11th to 20thNight
74%
540
13%
1620
11%
540
74%
540
27%
1061
June21st to endNight
74%
540
11%
1620
9%
540
74%
540
25%
1103
July1st to 10thNight
71%
525
10%
1575
8%
525
71%
525
22%
1100
July11th to 20thNight
75%
522
10%
1566
11%
522
75%
522
23%
1077
July21st to endNight
79%
591
14%
1672
13%
558
81%
558
29%
1060
August1st to 10thNight
72%
537
10%
1600
10%
534
72%
534
23%
1100
August11th to 20thNight
75%
534
9%
1598
9%
534
75%
534
24%
1100
August21st to endNight
63%
787
11%
2119
10%
787
64%
787
19%
1596
September1st to 10thNight
63%
720
11%
1980
10%
720
63%
720
19%
1471
September11th to 20thNight
61%
720
9%
1980
8%
720
61%
720
19%
1482
September21st to endNight
62%
720
19%
1980
19%
720
63%
720
24%
1380
October1st to 10thNight
58%
720
22%
2029
20%
720
61%
720
27%
1343
October11th to 20thNight
67%
720
29%
2160
30%
720
71%
720
36%
1239
October21st to endNight
61%
792
28%
2376
26%
792
67%
792
33%
1400
November1st to 10thNight
56%
740
23%
2221
20%
740
61%
740
31%
1366
November11th to 20thNight
51%
760
25%
2280
19%
760
58%
760
28%
1439
November21st to endNight
50%
760
23%
2463
20%
760
57%
760
27%
1531
December1st to 10thNight
51%
760
23%
2470
17%
760
60%
760
29%
1464
December11th to 20thNight
47%
759
22%
2938
18%
758
54%
758
21%
1786
December21st to endNight
49%
827
14%
4438
18%
817
56%
817
14%
2787

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
10%5%25%6%35%5%7%9%42%
79168
Night
10%6%35%5%35%5%6%9%43%
80835
TransparencyDay
35%10%16%19%14%5%
78891
Night
37%9%15%18%15%6%
80631
SeeingDay
10%313%27%30%16%
14577
Night
11%416%29%31%9%
24745

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
12%7%25%5%3445%7%46%
2836
11th to 20thDay
14%6%36%6%34447%42%
2840
21st to endDay
12%6%35%6%3445%8%44%
3124
February1st to 10thDay
16%7%35%5%35%35%6%42%
1864
11th to 20thDay
13%5%25%4235%5%6%49%
1848
21st to endDay
12%5%35%32446%7%48%
1651
March1st to 10thDay
9%5%2442345%8%53%
2090
11th to 20thDay
8%4344345%6%8%51%
2090
21st to endDay
10%5%25%4345%5%7%50%
2255
April1st to 10thDay
8%5%245%445%5%9%50%
1980
11th to 20thDay
9%6%26%5%35%6%6%7%45%
2036
21st to endDay
6%31442446%9%58%
2186
May1st to 10thDay
6%313425%46%8%58%
2340
11th to 20thDay
7%425%5%36%6%7%11%44%
2301
21st to endDay
9%4246%5%6%6%8%11%40%
2531
June1st to 10thDay
11%5%35%7%46%6%9%11%33%
2340
11th to 20thDay
5%436%7%5%7%6%8%12%37%
2340
21st to endDay
7%436%7%5%7%8%9%12%30%
2340
July1st to 10thDay
8%426%7%47%6%9%13%33%
2340
11th to 20thDay
6%436%7%47%8%11%13%30%
2340
21st to endDay
6%336%6%47%8%8%13%35%
2547
August1st to 10thDay
7%5%26%8%48%8%9%12%30%
2327
11th to 20thDay
7%5%26%6%5%7%9%10%13%30%
2288
21st to endDay
11%7%36%8%5%7%8%8%10%28%
2228
September1st to 10thDay
9%7%27%7%5%8%7%8%10%29%
1980
11th to 20thDay
14%6%36%7%5%7%6%7%9%29%
1980
21st to endDay
15%6%26%6%45%5%6%10%34%
1980
October1st to 10thDay
13%5%25%5%35%5%7%9%40%
1929
11th to 20thDay
7%4246%3445%8%52%
1800
21st to endDay
10%424435%5%5%9%49%
1980
November1st to 10thDay
12%6%25%42445%7%48%
1857
11th to 20thDay
12%6%36%5%26%446%46%
1900
21st to endDay
12%6%36%6%35%45%6%44%
1713
December1st to 10thDay
11%435%5%35%5%6%8%45%
1710
11th to 20thDay
15%6%35%5%3445%7%43%
2153
21st to endDay
15%7%36%6%3445%5%42%
3124
January1st to 10thNight
14%7%35%5%2445%7%43%
4109
11th to 20thNight
10%8%46%6%35%6%7%8%38%
4120
21st to endNight
12%8%36%6%445%5%7%41%
4532
February1st to 10thNight
14%7%35%5%45%447%43%
2314
11th to 20thNight
14%6%346%44445%47%
2218
21st to endNight
12%425%6%35%45%7%47%
1801
March1st to 10thNight
9%435%5%2345%6%54%
2090
11th to 20thNight
9%4245%3446%9%50%
2090
21st to endNight
10%5%25%42445%7%53%
2256
April1st to 10thNight
9%5%24435%5%5%8%50%
1980
11th to 20thNight
9%5%25%43346%7%52%
1870
21st to endNight
6%3244335%7%9%55%
1787
May1st to 10thNight
6%21342445%8%61%
1620
11th to 20thNight
6%4235%45%6%7%10%47%
1592
21st to endNight
7%4246%45%6%7%10%43%
1744
June1st to 10thNight
8%5%25%6%46%6%9%12%37%
1620
11th to 20thNight
6%5%25%5%5%6%5%9%13%38%
1620
21st to endNight
7%5%26%5%46%7%9%14%35%
1620
July1st to 10thNight
7%426%8%47%7%9%12%35%
1620
11th to 20thNight
5%5%27%8%46%7%9%14%32%
1620
21st to endNight
45%25%5%46%6%9%13%40%
1771
August1st to 10thNight
5%5%27%7%5%6%7%9%12%35%
1611
11th to 20thNight
5%436%6%46%8%10%12%35%
1598
21st to endNight
10%7%37%8%5%6%7%9%11%27%
2119
September1st to 10thNight
10%7%37%8%6%7%7%7%10%28%
1980
11th to 20thNight
13%5%37%7%5%7%8%7%11%26%
1980
21st to endNight
11%6%37%6%45%5%7%10%36%
1980
October1st to 10thNight
13%6%26%5%45%5%6%9%40%
2029
11th to 20thNight
7%4245%35%5%5%8%53%
2160
21st to endNight
9%425%5%345%5%7%51%
2376
November1st to 10thNight
11%5%35%5%245%5%7%47%
2221
11th to 20thNight
13%6%35%435%45%6%47%
2280
21st to endNight
13%5%35%5%345%6%8%42%
2463
December1st to 10thNight
12%6%25%4345%5%10%45%
2470
11th to 20thNight
14%6%35%5%34446%45%
3042
21st to endNight
14%8%36%6%345%5%7%38%
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
37%7%8%16%24%9%
2837
11th to 20thDay
41%6%8%16%20%10%
2840
21st to endDay
39%9%7%18%16%11%
3124
February1st to 10thDay
42%5%10%15%19%9%
1864
11th to 20thDay
36%6%9%17%22%11%
1858
21st to endDay
35%5%12%19%19%11%
1651
March1st to 10thDay
29%6%12%23%22%8%
2090
11th to 20thDay
29%8%17%20%17%9%
2090
21st to endDay
33%7%13%21%19%6%
2255
April1st to 10thDay
30%8%13%20%18%10%
1980
11th to 20thDay
34%8%11%21%18%8%
2036
21st to endDay
23%6%16%27%23%6%
2186
May1st to 10thDay
24%7%12%28%24%6%
2340
11th to 20thDay
31%10%20%23%13%2
2305
21st to endDay
31%12%17%22%16%2
2531
June1st to 10thDay
37%13%21%20%8%
2340
11th to 20thDay
33%14%22%25%6%
2340
21st to endDay
38%16%25%15%5%
2340
July1st to 10thDay
35%15%30%17%2
2275
11th to 20thDay
34%18%30%13%5%
2271
21st to endDay
33%14%28%22%3
2405
August1st to 10thDay
36%18%27%17%1
2314
11th to 20thDay
35%17%34%13%2
2288
21st to endDay
44%17%22%15%1
2228
September1st to 10thDay
41%16%20%13%8%1
1980
11th to 20thDay
46%14%17%15%7%1
1980
21st to endDay
41%11%17%15%13%2
1980
October1st to 10thDay
38%10%12%17%16%8%
1929
11th to 20thDay
30%5%11%23%25%5%
1800
21st to endDay
29%8%10%20%20%12%
1980
November1st to 10thDay
36%6%11%20%18%10%
1857
11th to 20thDay
38%6%9%17%21%8%
1900
21st to endDay
38%5%12%20%19%6%
1713
December1st to 10thDay
36%7%14%22%15%5%
1710
11th to 20thDay
39%8%11%14%21%6%
2150
21st to endDay
44%6%9%17%18%8%
3124
January1st to 10thNight
40%5%8%14%21%13%
4109
11th to 20thNight
41%6%9%15%20%9%
4120
21st to endNight
43%7%9%15%15%11%
4532
February1st to 10thNight
42%5%9%15%19%10%
2314
11th to 20thNight
39%5%9%17%18%12%
2219
21st to endNight
36%6%12%19%16%10%
1801
March1st to 10thNight
30%5%13%21%20%10%
2090
11th to 20thNight
31%7%16%20%17%9%
2090
21st to endNight
31%5%14%22%18%9%
2256
April1st to 10thNight
31%7%14%19%18%11%
1980
11th to 20thNight
31%6%10%24%21%7%
1870
21st to endNight
24%7%16%26%21%6%
1787
May1st to 10thNight
22%7%13%28%24%6%
1620
11th to 20thNight
28%12%21%22%14%3
1593
21st to endNight
32%11%16%23%16%2
1745
June1st to 10thNight
36%13%22%21%8%
1620
11th to 20thNight
35%12%23%22%7%
1620
21st to endNight
34%17%24%18%6%1
1620
July1st to 10thNight
39%15%25%18%21
1575
11th to 20thNight
37%16%28%15%5%
1566
21st to endNight
29%15%28%25%2
1672
August1st to 10thNight
37%16%29%16%2
1600
11th to 20thNight
34%19%30%15%2
1598
21st to endNight
45%15%21%14%4
2119
September1st to 10thNight
47%13%18%15%6%2
1980
11th to 20thNight
47%13%18%14%7%
1980
21st to endNight
42%10%15%15%15%2
1980
October1st to 10thNight
40%8%14%18%13%8%
2029
11th to 20thNight
30%7%9%24%25%5%
2160
21st to endNight
31%8%10%18%22%11%
2376
November1st to 10thNight
34%7%12%17%18%11%
2221
11th to 20thNight
39%6%9%17%21%9%
2280
21st to endNight
39%6%11%20%18%7%
2463
December1st to 10thNight
34%6%18%22%15%5%
2470
11th to 20thNight
39%6%9%17%22%7%
3044
21st to endNight
44%8%12%15%17%4
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
13%431%39%14%
270
11th to 20thDay
48%23%43%19%3
270
21st to endDay
16%6%32%37%9%
297
February1st to 10thDay
18%6%21%33%20%1
270
11th to 20thDay
16%325%39%16%1
270
21st to endDay
12%324%44%15%2
306
March1st to 10thDay
9%6%26%37%21%1
460
11th to 20thDay
10%5%23%36%21%4
460
21st to endDay
10%6%24%38%20%2
490
April1st to 10thDay
10%6%22%36%23%3
420
11th to 20thDay
8%5%23%33%24%7%
412
21st to endDay
5%317%35%30%11%
420
May1st to 10thDay
6%216%37%31%9%
423
11th to 20thDay
7%19%30%38%15%
447
21st to endDay
9%15%20%39%26%
485
June1st to 10thDay
12%28%21%36%21%
450
11th to 20thDay
6%16%18%38%32%
450
21st to endDay
6%1315%42%32%
450
July1st to 10thDay
6%138%39%42%
445
11th to 20thDay
5%26%40%47%
444
21st to endDay
6%1412%43%34%
488
August1st to 10thDay
7%314%37%39%
446
11th to 20thDay
4128%42%44%
439
21st to endDay
12%1313%39%33%
495
September1st to 10thDay
9%35%13%37%33%
450
11th to 20thDay
14%35%18%43%17%
450
21st to endDay
12%26%21%38%20%
450
October1st to 10thDay
14%49%34%30%10%
450
11th to 20thDay
8%215%31%35%9%
450
21st to endDay
8%315%33%36%6%
495
November1st to 10thDay
15%6%16%32%24%7%
455
11th to 20thDay
15%8%20%34%20%3
460
21st to endDay
14%5%17%40%21%2
273
December1st to 10thDay
10%420%39%23%3
270
11th to 20thDay
17%6%21%35%18%2
270
21st to endDay
14%6%17%35%27%2
297
January1st to 10thNight
13%8%32%33%13%1
760
11th to 20thNight
12%6%24%37%18%2
760
21st to endNight
17%7%31%36%9%1
836
February1st to 10thNight
16%6%26%36%14%1
760
11th to 20thNight
16%6%27%38%13%
743
21st to endNight
14%424%44%14%
628
March1st to 10thNight
11%5%23%41%19%1
760
11th to 20thNight
10%7%22%39%19%2
760
21st to endNight
11%424%37%21%2
821
April1st to 10thNight
9%422%38%24%2
720
11th to 20thNight
10%5%21%32%27%4
711
21st to endNight
7%314%39%33%4
707
May1st to 10thNight
6%216%39%32%6%
540
11th to 20thNight
7%211%29%41%11%
531
21st to endNight
9%16%21%49%15%
584
June1st to 10thNight
11%15%28%42%13%
540
11th to 20thNight
6%25%21%42%23%
540
21st to endNight
8%1419%46%22%
540
July1st to 10thNight
7%2414%46%27%
525
11th to 20thNight
7%1211%48%32%
522
21st to endNight
41316%57%20%
591
August1st to 10thNight
7%412%53%23%
537
11th to 20thNight
7%1210%49%31%
534
21st to endNight
12%15%15%40%27%
787
September1st to 10thNight
12%25%15%48%18%
720
11th to 20thNight
15%17%19%45%13%
720
21st to endNight
15%25%22%43%13%
720
October1st to 10thNight
17%111%27%35%9%
720
11th to 20thNight
9%313%32%35%8%
720
21st to endNight
10%316%29%35%7%
792
November1st to 10thNight
12%420%33%27%4
740
11th to 20thNight
14%6%22%33%23%3
760
21st to endNight
14%5%23%33%21%4
760
December1st to 10thNight
13%7%22%31%25%2
760
11th to 20thNight
14%6%24%31%21%4
760
21st to endNight
14%8%18%37%22%1
836
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