Key West
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Key West clear sky chart from 2005-11-06 to 2024-01-12.

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
72%
24801
12%
74575
11%
24753
73%
24753
16%
56006

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
66%
758
15%
2459
16%
757
68%
757
17%
1781
January11th to 20thNight
60%
725
12%
2318
12%
725
62%
725
13%
1769
January21st to endNight
59%
792
17%
2376
15%
792
62%
792
16%
1772
February1st to 10thNight
65%
720
17%
2160
15%
720
67%
720
16%
1615
February11th to 20thNight
66%
700
16%
2084
14%
699
68%
699
19%
1510
February21st to endNight
77%
592
28%
1628
24%
592
78%
592
27%
1093
March1st to 10thNight
69%
720
16%
1980
12%
720
73%
720
22%
1427
March11th to 20thNight
75%
720
19%
1980
16%
720
77%
720
25%
1380
March21st to endNight
74%
792
21%
2178
17%
792
76%
792
24%
1527
April1st to 10thNight
82%
720
16%
1980
13%
720
83%
720
24%
1388
April11th to 20thNight
75%
711
15%
1953
12%
711
77%
711
24%
1380
April21st to endNight
77%
720
20%
1862
16%
720
78%
720
25%
1336
May1st to 10thNight
85%
720
19%
1800
15%
720
85%
720
31%
1221
May11th to 20thNight
73%
596
10%
1657
8%
596
73%
596
19%
1245
May21st to endNight
70%
582
8%
1745
8%
582
70%
582
14%
1358
June1st to 10thNight
60%
540
7%
1620
6%
540
60%
540
10%
1329
June11th to 20thNight
76%
540
7%
1620
8%
540
76%
540
14%
1256
June21st to endNight
77%
540
4%
1620
4%
540
77%
540
10%
1335
July1st to 10thNight
82%
525
6%
1575
6%
525
82%
525
14%
1226
July11th to 20thNight
83%
522
6%
1566
6%
522
83%
522
15%
1199
July21st to endNight
84%
591
6%
1672
6%
558
84%
558
17%
1228
August1st to 10thNight
81%
537
7%
1693
8%
534
81%
534
16%
1268
August11th to 20thNight
82%
649
5%
1891
4%
649
82%
649
15%
1475
August21st to endNight
73%
792
3%
2178
3%
792
73%
792
12%
1799
September1st to 10thNight
80%
720
3%
1980
3%
720
80%
720
13%
1588
September11th to 20thNight
72%
720
4%
1980
4%
720
72%
720
11%
1671
September21st to endNight
66%
720
5%
1980
5%
720
66%
720
11%
1654
October1st to 10thNight
67%
720
9%
1980
10%
720
67%
720
14%
1585
October11th to 20thNight
69%
720
10%
2124
11%
720
70%
720
14%
1669
October21st to endNight
64%
792
12%
2376
13%
792
65%
792
13%
1872
November1st to 10thNight
65%
740
15%
2221
14%
740
68%
740
15%
1693
November11th to 20thNight
67%
760
18%
2280
19%
760
69%
760
18%
1679
November21st to endNight
68%
760
15%
2280
15%
760
69%
760
18%
1675
December1st to 10thNight
68%
760
15%
2379
17%
760
70%
760
17%
1742
December11th to 20thNight
67%
759
16%
2907
13%
758
68%
758
13%
2024
December21st to endNight
67%
826
9%
4493
15%
817
69%
817
9%
3237

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
6%425%5%36%7%8%12%42%
74751
Night
6%425%5%45%6%7%11%44%
74957
TransparencyDay
22%41%14%15%8%1
74474
Night
23%40%13%15%9%1
74753
SeeingDay
7%19%23%35%25%
14674
Night
7%19%26%37%19%
24819

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
6%325%5%45%6%7%13%44%
1706
11th to 20thDay
8%5%35%6%36%6%7%13%38%
1661
21st to endDay
8%435%446%6%7%10%43%
1980
February1st to 10thDay
8%4244245%7%10%50%
1800
11th to 20thDay
5%43343347%10%55%
1760
21st to endDay
421242445%10%61%
1628
March1st to 10thDay
33135%235%5%11%58%
1980
11th to 20thDay
43243246%7%11%55%
1980
21st to endDay
432332346%10%60%
2178
April1st to 10thDay
21123245%8%13%59%
1980
11th to 20thDay
421333446%12%58%
1956
21st to endDay
42233245%6%10%59%
2096
May1st to 10thDay
321222345%10%66%
2160
11th to 20thDay
8%6%25%5%35%6%7%11%42%
2248
21st to endDay
7%5%35%6%35%6%8%12%40%
2531
June1st to 10thDay
12%7%47%6%46%7%7%11%30%
2340
11th to 20thDay
6%6%26%6%47%8%8%13%33%
2340
21st to endDay
4326%6%47%9%10%14%34%
2340
July1st to 10thDay
44246%47%7%10%15%36%
2340
11th to 20thDay
3425%6%47%9%11%17%32%
2340
21st to endDay
3213447%8%12%18%36%
2547
August1st to 10thDay
4426%7%48%9%12%18%29%
2228
11th to 20thDay
2225%7%47%10%12%16%32%
1989
21st to endDay
5%5%36%8%5%8%9%9%14%27%
2178
September1st to 10thDay
5%425%7%5%8%10%11%14%28%
1980
11th to 20thDay
5%5%36%8%48%7%10%15%28%
1980
21st to endDay
8%7%37%8%5%8%7%9%12%28%
1980
October1st to 10thDay
5%6%36%7%48%9%11%12%29%
1980
11th to 20thDay
9%5%25%7%46%7%7%14%34%
1835
21st to endDay
8%6%35%6%46%6%7%11%38%
1980
November1st to 10thDay
7%425%5%35%6%7%10%45%
1857
11th to 20thDay
9%5%26%6%45%5%7%9%41%
1900
21st to endDay
6%4245%35%6%8%9%48%
1900
December1st to 10thDay
6%425%6%35%6%6%11%47%
1796
11th to 20thDay
8%425%5%36%6%7%10%45%
2153
21st to endDay
10%6%26%6%46%6%7%11%36%
3124
January1st to 10thNight
6%425%5%35%6%9%11%44%
2459
11th to 20thNight
7%5%37%6%35%5%6%10%42%
2318
21st to endNight
6%5%35%5%46%6%6%9%44%
2376
February1st to 10thNight
7%5%25%5%35%6%7%9%47%
2160
11th to 20thNight
6%325%5%2445%7%56%
2084
21st to endNight
43143235%6%10%60%
1628
March1st to 10thNight
3224435%5%6%10%56%
1980
11th to 20thNight
42234345%6%8%59%
1980
21st to endNight
43234345%6%9%58%
2178
April1st to 10thNight
32123345%6%11%59%
1980
11th to 20thNight
5%314435%6%7%10%52%
1953
21st to endNight
44244335%5%8%58%
1862
May1st to 10thNight
231232346%8%65%
1800
11th to 20thNight
7%5%25%5%36%6%8%11%41%
1657
21st to endNight
7%6%45%6%446%6%11%42%
1744
June1st to 10thNight
13%8%36%7%46%6%8%10%27%
1620
11th to 20thNight
5%435%6%47%8%9%13%37%
1620
21st to endNight
4425%6%5%8%7%8%14%36%
1620
July1st to 10thNight
4414435%6%10%15%42%
1620
11th to 20thNight
22245%47%8%9%17%40%
1620
21st to endNight
23245%45%7%8%16%44%
1771
August1st to 10thNight
2325%5%47%7%10%17%37%
1704
11th to 20thNight
3325%6%46%8%8%14%41%
1891
21st to endNight
45%36%7%5%7%8%9%16%30%
2178
September1st to 10thNight
43246%5%8%9%12%16%33%
1980
11th to 20thNight
5%5%37%7%6%7%9%10%13%28%
1980
21st to endNight
8%8%37%6%46%7%9%13%28%
1980
October1st to 10thNight
5%6%38%8%46%7%9%12%31%
1980
11th to 20thNight
8%6%25%6%46%7%8%12%36%
2124
21st to endNight
10%6%35%6%46%6%8%10%36%
2376
November1st to 10thNight
8%325%6%35%5%7%12%44%
2221
11th to 20thNight
9%426%5%35%5%7%9%44%
2280
21st to endNight
6%4345%35%6%7%10%47%
2280
December1st to 10thNight
6%325%6%35%6%6%9%47%
2379
11th to 20thNight
8%4245%35%6%7%11%45%
3042
21st to endNight
9%6%36%7%45%6%7%9%37%
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
19%42%11%16%10%2
1707
11th to 20thDay
22%44%10%13%7%3
1661
21st to endDay
23%39%9%15%10%3
1980
February1st to 10thDay
21%37%7%19%14%2
1800
11th to 20thDay
17%39%10%19%11%3
1770
21st to endDay
13%36%5%22%20%4
1628
March1st to 10thDay
16%37%8%22%15%1
1980
11th to 20thDay
15%38%9%22%14%2
1980
21st to endDay
13%38%9%23%16%2
2178
April1st to 10thDay
12%38%13%28%8%1
1980
11th to 20thDay
13%38%14%24%10%1
1956
21st to endDay
14%37%11%22%14%2
2096
May1st to 10thDay
9%37%12%26%15%1
2160
11th to 20thDay
22%42%13%17%5%1
2252
21st to endDay
25%41%13%16%5%
2531
June1st to 10thDay
31%41%13%12%3
2340
11th to 20thDay
25%44%20%10%
2340
21st to endDay
29%46%17%7%1
2340
July1st to 10thDay
26%47%19%8%
2275
11th to 20thDay
22%47%22%8%
2271
21st to endDay
18%45%25%11%1
2405
August1st to 10thDay
22%47%20%11%
2215
11th to 20thDay
24%44%25%7%1
1989
21st to endDay
29%44%20%7%
2178
September1st to 10thDay
24%47%21%8%1
1980
11th to 20thDay
28%46%18%6%1
1980
21st to endDay
30%43%15%11%1
1980
October1st to 10thDay
27%42%14%11%42
1980
11th to 20thDay
26%41%13%13%5%1
1835
21st to endDay
27%41%6%14%11%1
1980
November1st to 10thDay
23%42%5%13%15%3
1857
11th to 20thDay
23%41%7%16%13%1
1900
21st to endDay
20%43%9%14%13%2
1900
December1st to 10thDay
18%42%10%19%10%1
1796
11th to 20thDay
24%35%9%16%12%4
2150
21st to endDay
33%30%13%9%13%1
3124
January1st to 10thNight
18%41%10%21%7%3
2459
11th to 20thNight
23%43%9%15%9%2
2318
21st to endNight
22%40%7%17%11%3
2376
February1st to 10thNight
23%39%7%15%14%2
2160
11th to 20thNight
21%38%9%17%13%3
2085
21st to endNight
12%36%7%18%22%6%
1628
March1st to 10thNight
18%38%9%18%14%2
1980
11th to 20thNight
15%37%10%19%16%2
1980
21st to endNight
16%37%8%21%15%3
2178
April1st to 10thNight
15%38%13%22%10%1
1980
11th to 20thNight
17%37%11%22%12%2
1953
21st to endNight
17%37%9%22%14%2
1862
May1st to 10thNight
9%37%11%24%18%1
1800
11th to 20thNight
20%40%14%17%7%
1658
21st to endNight
28%38%12%14%7%
1745
June1st to 10thNight
34%40%13%10%3
1620
11th to 20thNight
25%41%21%10%3
1620
21st to endNight
30%43%19%6%1
1620
July1st to 10thNight
22%44%21%12%
1575
11th to 20thNight
22%43%22%12%
1566
21st to endNight
17%43%25%13%2
1672
August1st to 10thNight
21%42%23%13%1
1693
11th to 20thNight
25%41%23%10%1
1891
21st to endNight
27%45%19%8%1
2178
September1st to 10thNight
22%47%23%7%1
1980
11th to 20thNight
30%45%16%7%1
1980
21st to endNight
32%42%15%10%1
1980
October1st to 10thNight
27%42%13%11%6%2
1980
11th to 20thNight
26%41%13%14%5%1
2124
21st to endNight
27%41%7%14%11%1
2376
November1st to 10thNight
22%42%6%13%13%3
2221
11th to 20thNight
19%41%8%18%14%1
2280
21st to endNight
19%41%11%14%14%1
2280
December1st to 10thNight
19%42%10%19%9%1
2379
11th to 20thNight
24%34%8%20%11%3
3044
21st to endNight
35%30%12%10%13%1
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
5%420%38%29%4
270
11th to 20thDay
11%7%16%38%26%2
243
21st to endDay
13%423%39%18%3
264
February1st to 10thDay
7%5%12%42%31%3
240
11th to 20thDay
5%114%35%36%9%
252
21st to endDay
6%15%29%45%5%
346
March1st to 10thDay
5%118%43%29%4
420
11th to 20thDay
6%116%39%34%4
420
21st to endDay
4112%39%39%5%
462
April1st to 10thDay
229%44%39%4
420
11th to 20thDay
3113%46%33%4
412
21st to endDay
416%44%41%3
420
May1st to 10thDay
45%33%48%10%
423
11th to 20thDay
11%17%27%43%12%
447
21st to endDay
11%1416%49%20%
485
June1st to 10thDay
14%17%17%34%28%
450
11th to 20thDay
9%410%36%40%
450
21st to endDay
325%30%59%
450
July1st to 10thDay
42331%60%
445
11th to 20thDay
32332%59%
444
21st to endDay
7%15%32%55%
488
August1st to 10thDay
5%2336%54%
446
11th to 20thDay
3126%33%55%
439
21st to endDay
6%15%11%33%44%
495
September1st to 10thDay
5%18%29%57%
450
11th to 20thDay
8%37%24%58%
450
21st to endDay
10%16%8%28%47%
450
October1st to 10thDay
6%7%22%45%20%
450
11th to 20thDay
11%27%18%39%23%
450
21st to endDay
7%113%25%38%15%
495
November1st to 10thDay
9%213%27%38%11%
455
11th to 20thDay
13%312%31%30%10%
460
21st to endDay
7%215%33%35%8%
460
December1st to 10thDay
10%112%30%38%10%
356
11th to 20thDay
8%413%28%40%8%
270
21st to endDay
9%5%17%28%33%8%
297
January1st to 10thNight
8%215%35%36%4
760
11th to 20thNight
11%217%38%29%3
725
21st to endNight
9%419%39%27%2
792
February1st to 10thNight
9%216%38%33%3
720
11th to 20thNight
6%217%36%34%4
703
21st to endNight
5%211%36%41%5%
592
March1st to 10thNight
5%217%41%31%3
720
11th to 20thNight
5%113%39%38%4
720
21st to endNight
4114%41%36%3
792
April1st to 10thNight
418%43%42%3
720
11th to 20thNight
5%111%44%36%3
711
21st to endNight
6%17%45%38%3
720
May1st to 10thNight
37%34%47%9%
720
11th to 20thNight
10%16%31%44%8%
596
21st to endNight
9%16%24%44%16%
584
June1st to 10thNight
16%17%16%40%20%
540
11th to 20thNight
7%49%41%39%
540
21st to endNight
5%26%39%48%
540
July1st to 10thNight
5%2434%56%
525
11th to 20thNight
315%34%57%
522
21st to endNight
325%31%59%
591
August1st to 10thNight
325%40%49%
537
11th to 20thNight
417%35%53%
649
21st to endNight
8%149%33%46%
792
September1st to 10thNight
5%36%34%52%
720
11th to 20thNight
8%38%27%54%
720
21st to endNight
11%6%9%30%43%
720
October1st to 10thNight
8%8%19%45%20%
720
11th to 20thNight
11%17%18%41%23%
720
21st to endNight
13%111%25%37%12%
792
November1st to 10thNight
8%116%30%36%8%
740
11th to 20thNight
11%110%30%39%10%
760
21st to endNight
8%113%34%38%5%
760
December1st to 10thNight
9%111%33%40%6%
760
11th to 20thNight
9%311%32%38%6%
760
21st to endNight
8%314%32%36%7%
836
Page generated at 2024-01-08 22:31:24. Version ac07

Copyright 2024 Attilla Danko


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