Miami
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Miami 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
65%
25331
16%
80307
15%
25247
67%
25247
25%
52901

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
59%
748
15%
4063
19%
737
66%
737
17%
2449
January11th to 20thNight
52%
749
12%
4101
16%
740
58%
740
12%
2973
January21st to endNight
51%
826
14%
4402
19%
814
59%
814
14%
2722
February1st to 10thNight
58%
760
25%
2280
23%
760
62%
760
30%
1385
February11th to 20thNight
60%
741
29%
2081
21%
739
68%
739
43%
1178
February21st to endNight
66%
628
30%
1727
25%
628
69%
628
43%
973
March1st to 10thNight
59%
760
25%
2090
18%
760
65%
760
39%
1215
March11th to 20thNight
65%
760
26%
2090
20%
760
70%
760
41%
1204
March21st to endNight
64%
821
27%
2256
22%
821
69%
821
40%
1300
April1st to 10thNight
73%
720
25%
1980
22%
720
75%
720
47%
1087
April11th to 20thNight
68%
711
19%
1862
15%
711
70%
711
38%
1149
April21st to endNight
70%
720
25%
1800
16%
720
72%
720
40%
1108
May1st to 10thNight
76%
720
23%
1800
16%
720
78%
720
49%
1038
May11th to 20thNight
65%
709
12%
1771
9%
709
65%
709
30%
1221
May21st to endNight
68%
612
15%
1774
14%
612
68%
612
25%
1211
June1st to 10thNight
61%
540
8%
1620
7%
540
61%
540
15%
1278
June11th to 20thNight
72%
540
11%
1620
10%
540
72%
540
21%
1148
June21st to endNight
77%
540
6%
1620
5%
540
77%
540
21%
1146
July1st to 10thNight
75%
525
7%
1575
7%
525
75%
525
21%
1106
July11th to 20thNight
77%
522
7%
1566
7%
522
77%
522
24%
1057
July21st to endNight
79%
591
10%
1672
9%
558
79%
558
27%
1104
August1st to 10thNight
75%
584
8%
1647
7%
581
75%
581
23%
1156
August11th to 20thNight
80%
710
7%
1774
6%
710
80%
710
28%
1239
August21st to endNight
67%
792
6%
2126
5%
792
67%
792
21%
1578
September1st to 10thNight
72%
720
6%
1980
6%
720
72%
720
20%
1445
September11th to 20thNight
67%
720
5%
1980
5%
720
67%
720
16%
1548
September21st to endNight
62%
720
8%
1980
9%
720
62%
720
15%
1579
October1st to 10thNight
60%
720
9%
2071
10%
720
62%
720
17%
1533
October11th to 20thNight
64%
720
13%
2160
13%
720
65%
720
23%
1486
October21st to endNight
57%
792
19%
2376
20%
792
60%
792
25%
1587
November1st to 10thNight
56%
740
19%
2221
17%
740
61%
740
26%
1424
November11th to 20thNight
57%
760
19%
2280
17%
760
60%
760
20%
1613
November21st to endNight
58%
760
21%
2280
18%
760
63%
760
26%
1476
December1st to 10thNight
61%
760
23%
2280
19%
760
66%
760
27%
1454
December11th to 20thNight
59%
759
21%
2924
21%
759
63%
759
23%
1758
December21st to endNight
59%
831
12%
4478
20%
817
64%
817
15%
2973

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
8%6%37%7%5%7%7%8%11%32%
79169
Night
7%5%36%6%46%6%7%10%39%
80826
TransparencyDay
38%14%19%17%10%2
78892
Night
38%11%18%19%11%2
80622
SeeingDay
7%313%30%32%16%
15171
Night
8%313%30%32%14%
25374

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
9%7%45%6%46%6%7%10%36%
2836
11th to 20thDay
15%7%48%8%5%6%6%7%8%26%
2840
21st to endDay
6%7%38%8%46%6%7%7%36%
3165
February1st to 10thDay
9%6%35%6%5%5%6%6%11%40%
1900
11th to 20thDay
6%425%425%5%7%10%49%
1983
21st to endDay
5%4245%46%6%7%10%47%
1727
March1st to 10thDay
5%5%26%6%46%6%6%12%43%
2090
11th to 20thDay
6%3245%45%7%9%12%44%
2090
21st to endDay
6%435%445%6%7%10%46%
2255
April1st to 10thDay
3425%435%6%10%12%46%
1980
11th to 20thDay
6%425%6%38%7%8%13%38%
2044
21st to endDay
6%3245%47%7%8%11%42%
2160
May1st to 10thDay
4314446%8%8%12%48%
2160
11th to 20thDay
10%6%37%7%5%7%8%8%13%26%
2124
21st to endDay
9%7%47%9%5%8%7%9%11%25%
2512
June1st to 10thDay
13%8%6%9%9%7%8%8%8%9%16%
2340
11th to 20thDay
6%7%39%9%7%10%10%10%11%18%
2340
21st to endDay
5%6%39%9%6%10%10%9%11%21%
2340
July1st to 10thDay
5%5%37%8%6%9%9%10%14%25%
2340
11th to 20thDay
6%5%38%8%5%9%9%10%14%24%
2340
21st to endDay
4427%8%5%9%10%11%14%26%
2547
August1st to 10thDay
6%6%28%8%5%9%10%10%12%24%
2261
11th to 20thDay
45%37%6%6%9%9%10%15%26%
2126
21st to endDay
8%5%27%9%5%9%9%10%14%21%
2224
September1st to 10thDay
7%5%37%9%6%10%10%10%13%20%
1980
11th to 20thDay
5%8%39%10%6%9%8%8%13%21%
1980
21st to endDay
11%8%49%8%5%9%7%9%10%20%
1980
October1st to 10thDay
8%7%39%8%5%9%8%10%12%21%
1886
11th to 20thDay
10%6%37%7%5%6%8%8%13%28%
1800
21st to endDay
11%7%38%6%46%6%7%9%34%
1980
November1st to 10thDay
8%6%36%6%46%7%8%9%37%
1857
11th to 20thDay
10%7%47%8%5%7%7%7%9%31%
1900
21st to endDay
8%6%25%7%47%6%7%10%37%
1900
December1st to 10thDay
8%6%26%5%46%6%6%10%40%
1900
11th to 20thDay
10%5%36%6%46%6%7%9%39%
2158
21st to endDay
13%7%26%7%5%6%6%8%10%30%
3124
January1st to 10thNight
9%6%26%6%46%7%7%10%37%
4109
11th to 20thNight
16%9%38%7%5%6%5%6%7%28%
4120
21st to endNight
8%7%48%7%46%5%6%8%38%
4486
February1st to 10thNight
8%5%25%5%345%6%11%45%
2280
11th to 20thNight
6%4244345%5%8%56%
2081
21st to endNight
5%3244345%6%10%54%
1727
March1st to 10thNight
3315%6%35%6%6%10%52%
2090
11th to 20thNight
6%3244345%6%9%54%
2090
21st to endNight
5%414435%6%6%9%53%
2256
April1st to 10thNight
43134245%6%10%57%
1980
11th to 20thNight
6%324435%6%7%9%50%
1862
21st to endNight
6%325%5%35%5%6%11%48%
1800
May1st to 10thNight
43135%245%6%10%59%
1800
11th to 20thNight
9%436%7%36%6%8%10%39%
1770
21st to endNight
8%7%36%6%37%6%8%12%35%
1774
June1st to 10thNight
12%8%38%7%5%8%10%8%10%22%
1620
11th to 20thNight
7%5%26%7%5%7%8%8%14%32%
1620
21st to endNight
5%5%35%7%5%7%9%10%15%29%
1620
July1st to 10thNight
4437%6%47%7%9%14%35%
1620
11th to 20thNight
4436%7%47%7%10%13%36%
1620
21st to endNight
2436%5%46%7%8%12%41%
1771
August1st to 10thNight
5%435%8%47%8%9%13%35%
1658
11th to 20thNight
2325%6%47%9%10%15%37%
1774
21st to endNight
6%6%37%8%5%7%8%8%13%29%
2126
September1st to 10thNight
6%436%6%5%7%9%9%13%32%
1980
11th to 20thNight
6%7%48%7%5%8%7%9%12%27%
1980
21st to endNight
8%7%38%9%5%8%9%8%11%23%
1980
October1st to 10thNight
8%7%37%9%5%8%9%8%10%26%
2071
11th to 20thNight
8%7%36%6%46%7%8%10%35%
2160
21st to endNight
11%6%37%7%445%6%9%38%
2376
November1st to 10thNight
8%6%25%5%45%5%7%11%41%
2221
11th to 20thNight
10%7%47%7%47%6%7%8%36%
2280
21st to endNight
9%5%25%6%36%6%7%10%41%
2280
December1st to 10thNight
8%435%6%45%6%7%10%43%
2280
11th to 20thNight
10%6%25%5%345%5%9%44%
3032
21st to endNight
10%8%38%7%47%6%7%9%31%
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
40%8%12%23%13%3
2837
11th to 20thDay
50%12%15%14%7%2
2840
21st to endDay
40%10%12%18%15%6%
3165
February1st to 10thDay
35%9%14%25%14%3
1900
11th to 20thDay
27%7%14%27%20%4
1993
21st to endDay
24%10%15%21%23%7%
1727
March1st to 10thDay
28%10%17%25%17%4
2090
11th to 20thDay
26%10%18%28%15%4
2090
21st to endDay
28%10%15%25%18%4
2255
April1st to 10thDay
22%10%23%30%12%2
1980
11th to 20thDay
29%12%21%21%15%2
2044
21st to endDay
28%10%17%24%18%3
2160
May1st to 10thDay
22%10%18%27%18%6%
2160
11th to 20thDay
41%14%20%20%5%
2128
21st to endDay
44%14%17%16%9%
2512
June1st to 10thDay
55%17%18%8%2
2340
11th to 20thDay
45%21%22%11%1
2340
21st to endDay
43%21%26%10%
2340
July1st to 10thDay
36%24%29%10%
2275
11th to 20thDay
37%22%29%11%
2271
21st to endDay
34%22%31%12%
2405
August1st to 10thDay
39%22%26%11%2
2248
11th to 20thDay
34%24%29%12%
2126
21st to endDay
42%21%26%10%1
2224
September1st to 10thDay
42%24%23%11%1
1980
11th to 20thDay
44%21%23%9%2
1980
21st to endDay
49%19%16%11%5%
1980
October1st to 10thDay
44%16%20%14%5%1
1886
11th to 20thDay
40%14%18%17%11%1
1800
21st to endDay
41%8%14%18%14%5%
1980
November1st to 10thDay
38%10%14%16%16%5%
1857
11th to 20thDay
43%11%14%16%13%3
1900
21st to endDay
37%9%17%16%19%2
1900
December1st to 10thDay
34%11%15%23%16%2
1900
11th to 20thDay
38%9%12%19%18%4
2155
21st to endDay
45%10%15%15%14%2
3124
January1st to 10thNight
39%10%15%19%14%2
4109
11th to 20thNight
53%10%13%15%7%2
4120
21st to endNight
42%9%12%18%14%5%
4486
February1st to 10thNight
34%8%13%25%17%3
2280
11th to 20thNight
25%7%14%26%21%7%
2082
21st to endNight
25%7%14%23%26%6%
1727
March1st to 10thNight
27%7%15%26%20%5%
2090
11th to 20thNight
25%8%17%31%15%3
2090
21st to endNight
27%8%14%27%22%4
2256
April1st to 10thNight
22%7%19%35%15%2
1980
11th to 20thNight
28%10%20%23%17%2
1862
21st to endNight
29%8%16%26%17%4
1800
May1st to 10thNight
21%8%18%32%17%5%
1800
11th to 20thNight
37%11%19%25%8%
1771
21st to endNight
40%10%19%20%11%
1775
June1st to 10thNight
52%15%20%11%2
1620
11th to 20thNight
41%15%25%18%2
1620
21st to endNight
37%19%33%11%
1620
July1st to 10thNight
36%19%31%14%
1575
11th to 20thNight
34%17%35%14%
1566
21st to endNight
31%17%34%16%2
1672
August1st to 10thNight
34%19%29%14%3
1647
11th to 20thNight
29%21%33%16%
1774
21st to endNight
43%16%28%12%1
2126
September1st to 10thNight
38%20%26%14%2
1980
11th to 20thNight
45%20%23%10%2
1980
21st to endNight
51%17%16%10%6%
1980
October1st to 10thNight
45%16%19%14%5%1
2071
11th to 20thNight
41%11%20%15%11%1
2160
21st to endNight
43%7%13%20%13%4
2376
November1st to 10thNight
39%8%15%19%16%4
2221
11th to 20thNight
47%10%9%20%12%3
2280
21st to endNight
39%9%15%20%15%3
2280
December1st to 10thNight
35%11%14%23%16%2
2280
11th to 20thNight
37%7%11%20%17%7%
3034
21st to endNight
44%11%15%14%14%2
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
7%8%24%44%16%
270
11th to 20thDay
11%7%27%40%13%1
270
21st to endDay
7%9%32%44%8%1
297
February1st to 10thDay
7%8%23%43%19%1
270
11th to 20thDay
7%5%19%42%25%2
406
21st to endDay
5%320%42%30%1
382
March1st to 10thDay
5%5%28%45%16%2
460
11th to 20thDay
5%326%43%22%2
460
21st to endDay
5%419%45%24%2
490
April1st to 10thDay
4122%49%20%3
420
11th to 20thDay
5%221%47%22%3
412
21st to endDay
4216%46%30%2
420
May1st to 10thDay
3111%46%31%8%
423
11th to 20thDay
9%212%32%36%7%
447
21st to endDay
9%28%24%42%15%
485
June1st to 10thDay
11%39%21%41%15%
450
11th to 20thDay
7%15%17%41%29%
450
21st to endDay
32311%39%42%
450
July1st to 10thDay
3127%42%46%
445
11th to 20thDay
4119%42%42%
444
21st to endDay
31310%41%43%
488
August1st to 10thDay
6%139%43%38%
446
11th to 20thDay
21212%44%40%
439
21st to endDay
8%1418%39%30%
495
September1st to 10thDay
8%1410%38%38%
450
11th to 20thDay
6%412%40%37%
450
21st to endDay
7%26%14%42%29%
450
October1st to 10thDay
9%36%31%40%11%
450
11th to 20thDay
9%210%33%35%11%
450
21st to endDay
12%314%33%32%6%
495
November1st to 10thDay
7%417%35%31%6%
455
11th to 20thDay
13%417%35%27%4
460
21st to endDay
10%318%40%26%3
460
December1st to 10thDay
9%119%41%27%2
460
11th to 20thDay
9%5%16%39%29%2
275
21st to endDay
9%7%20%38%24%1
297
January1st to 10thNight
7%6%21%37%26%3
760
11th to 20thNight
11%5%24%40%19%1
760
21st to endNight
8%8%24%42%17%1
836
February1st to 10thNight
10%5%19%42%23%1
760
11th to 20thNight
7%424%38%24%2
743
21st to endNight
6%319%45%26%1
628
March1st to 10thNight
5%5%26%44%19%2
760
11th to 20thNight
7%219%46%23%3
760
21st to endNight
5%421%43%25%1
821
April1st to 10thNight
4215%49%30%1
720
11th to 20thNight
5%317%46%28%2
711
21st to endNight
6%215%46%30%2
720
May1st to 10thNight
5%111%41%38%4
720
11th to 20thNight
9%210%40%37%3
709
21st to endNight
10%27%22%46%12%
614
June1st to 10thNight
14%25%22%39%17%
540
11th to 20thNight
7%1310%44%34%
540
21st to endNight
4139%37%46%
540
July1st to 10thNight
4146%39%47%
525
11th to 20thNight
5%118%37%47%
522
21st to endNight
3129%34%52%
591
August1st to 10thNight
7%210%41%40%
584
11th to 20thNight
429%43%42%
710
21st to endNight
9%15%15%38%33%
792
September1st to 10thNight
9%1410%38%39%
720
11th to 20thNight
9%25%13%34%38%
720
21st to endNight
12%15%16%37%29%
720
October1st to 10thNight
11%28%28%39%13%
720
11th to 20thNight
12%111%27%37%13%
720
21st to endNight
16%214%31%33%6%
792
November1st to 10thNight
11%5%19%32%29%5%
740
11th to 20thNight
12%417%32%30%5%
760
21st to endNight
11%419%35%28%3
760
December1st to 10thNight
9%417%36%33%2
760
11th to 20thNight
12%5%17%34%29%4
760
21st to endNight
9%420%36%27%4
836
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