This page made possible by the sponsorship of: Harry Sarber.

Tampa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tampa clear sky chart from 2005-11-06 to 2024-05-13.

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
57%
24850
19%
84761
16%
24715
63%
24715
26%
52705

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
43%
755
20%
4042
16%
737
55%
737
16%
2486
January11th to 20thNight
47%
755
18%
4073
20%
740
59%
740
15%
2761
January21st to endNight
37%
831
16%
4178
15%
814
48%
814
16%
2472
February1st to 10thNight
43%
760
25%
2280
16%
760
52%
760
31%
1384
February11th to 20thNight
46%
740
24%
2219
14%
740
56%
740
35%
1279
February21st to endNight
49%
628
26%
1834
16%
628
57%
628
35%
1079
March1st to 10thNight
45%
756
19%
3418
17%
745
56%
745
20%
2345
March11th to 20thNight
48%
747
23%
3443
17%
740
58%
740
28%
1612
March21st to endNight
50%
829
21%
3690
19%
814
59%
814
26%
1936
April1st to 10thNight
51%
760
25%
2090
16%
760
57%
760
42%
1164
April11th to 20thNight
46%
751
21%
2063
13%
751
53%
751
37%
1216
April21st to endNight
54%
740
29%
1919
18%
740
59%
740
45%
1096
May1st to 10thNight
74%
570
32%
1710
27%
570
77%
570
52%
837
May11th to 20thNight
65%
540
17%
1619
12%
540
70%
540
32%
1021
May21st to endNight
73%
582
23%
1745
19%
582
75%
582
38%
1022
June1st to 10thNight
66%
540
14%
1620
12%
540
67%
540
25%
1105
June11th to 20thNight
76%
540
13%
1620
11%
540
77%
540
30%
1059
June21st to endNight
74%
540
10%
1620
9%
540
75%
540
24%
1121
July1st to 10thNight
75%
525
5%
1575
5%
525
75%
525
21%
1151
July11th to 20thNight
77%
522
4%
1566
4%
522
77%
522
20%
1168
July21st to endNight
73%
591
8%
1672
8%
558
75%
558
22%
1188
August1st to 10thNight
78%
537
5%
1609
5%
534
78%
534
25%
1129
August11th to 20thNight
75%
534
6%
1776
7%
534
75%
534
21%
1229
August21st to endNight
62%
774
9%
2160
9%
774
63%
774
18%
1613
September1st to 10thNight
67%
720
7%
1980
7%
720
67%
720
18%
1468
September11th to 20thNight
62%
720
9%
1980
10%
720
63%
720
20%
1454
September21st to endNight
60%
720
18%
1980
16%
720
62%
720
24%
1389
October1st to 10thNight
57%
720
21%
1980
18%
720
61%
720
29%
1302
October11th to 20thNight
64%
720
29%
2116
28%
720
69%
720
36%
1236
October21st to endNight
56%
792
27%
2376
24%
792
64%
792
35%
1378
November1st to 10thNight
53%
740
28%
2221
21%
740
63%
740
39%
1228
November11th to 20thNight
52%
760
30%
2280
23%
760
62%
760
33%
1347
November21st to endNight
49%
760
27%
2432
21%
760
59%
760
30%
1450
December1st to 10thNight
51%
760
28%
2470
21%
760
63%
760
32%
1420
December11th to 20thNight
50%
759
25%
2938
20%
758
57%
758
24%
1703
December21st to endNight
48%
832
16%
4467
23%
817
56%
817
15%
2857

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%27%5%5%6%5%7%9%39%
84006
Night
8%6%27%5%5%5%47%9%42%
85501
TransparencyDay
38%9%14%20%14%5%
83729
Night
37%8%15%20%15%5%
85297
SeeingDay
8%5%18%27%24%18%
14759
Night
9%420%33%26%9%
24899

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
11%8%37%45%5%45%9%38%
2836
11th to 20thDay
21%10%37%33335%8%34%
2840
21st to endDay
10%6%26%445%46%8%44%
3388
February1st to 10thDay
12%5%26%43446%9%46%
1900
11th to 20thDay
7%5%1444445%7%55%
1848
21st to endDay
7%6%25%444348%53%
1617
March1st to 10thDay
5%5%38%6%6%6%5%7%9%39%
3435
11th to 20thDay
6%415%44447%10%51%
3480
21st to endDay
9%425%43336%8%53%
3815
April1st to 10thDay
7%424445%47%10%50%
2090
11th to 20thDay
7%5%36%5%5%45%6%9%45%
2066
21st to endDay
4325%35%5%5%7%9%53%
2270
May1st to 10thDay
42133345%7%8%59%
2470
11th to 20thDay
8%426%5%5%6%5%8%9%41%
2329
21st to endDay
5%5%27%6%7%7%6%8%10%38%
2531
June1st to 10thDay
11%8%48%6%7%8%6%9%10%25%
2340
11th to 20thDay
5%6%27%8%7%8%8%10%11%27%
2340
21st to endDay
7%5%28%7%7%8%6%9%12%26%
2340
July1st to 10thDay
8%6%28%9%8%9%8%10%11%23%
2340
11th to 20thDay
5%6%410%9%7%9%7%10%10%23%
2340
21st to endDay
6%6%39%9%8%8%7%9%11%24%
2547
August1st to 10thDay
7%5%310%7%8%8%8%11%10%23%
2312
11th to 20thDay
5%7%311%8%10%8%7%9%12%21%
2125
21st to endDay
10%7%39%7%8%9%6%9%9%23%
2178
September1st to 10thDay
6%6%39%8%7%9%7%10%12%23%
1980
11th to 20thDay
10%7%29%7%8%7%6%8%10%26%
1980
21st to endDay
7%7%29%6%6%7%6%8%9%33%
1980
October1st to 10thDay
7%6%38%6%6%7%6%7%8%35%
1980
11th to 20thDay
6%426%5%5%6%5%5%8%48%
1841
21st to endDay
6%5%25%345%47%10%48%
1980
November1st to 10thDay
7%5%26%5%4446%8%51%
1857
11th to 20thDay
8%6%26%5%5%5%45%8%46%
1900
21st to endDay
8%6%16%5%46%46%9%45%
1744
December1st to 10thDay
6%426%45%6%5%5%10%47%
1710
11th to 20thDay
10%6%26%5%4445%8%45%
2153
21st to endDay
12%9%38%6%5%5%45%7%35%
3124
January1st to 10thNight
11%8%39%5%5%5%45%8%36%
4109
11th to 20thNight
18%11%38%5%4435%7%31%
4120
21st to endNight
10%8%37%5%5%5%47%8%39%
4264
February1st to 10thNight
10%7%26%4345%5%7%47%
2280
11th to 20thNight
9%6%25%44445%8%51%
2218
21st to endNight
7%5%35%45%435%7%50%
1834
March1st to 10thNight
12%10%48%5%5%446%6%37%
3418
11th to 20thNight
4324345%410%13%47%
3480
21st to endNight
9%5%25%34435%8%51%
3817
April1st to 10thNight
5%325%44436%10%53%
2090
11th to 20thNight
6%426%5%4446%10%49%
2063
21st to endNight
6%415%344348%57%
1919
May1st to 10thNight
331422437%8%63%
1710
11th to 20thNight
6%5%25%45%5%5%7%10%45%
1619
21st to endNight
5%416%445%47%8%52%
1744
June1st to 10thNight
11%7%37%5%5%5%5%7%11%35%
1620
11th to 20thNight
5%5%26%6%45%5%9%14%37%
1620
21st to endNight
6%5%28%5%6%7%6%10%12%33%
1620
July1st to 10thNight
6%6%27%6%5%7%8%10%12%31%
1620
11th to 20thNight
5%6%36%6%8%8%7%11%14%27%
1620
21st to endNight
36%38%8%6%7%7%9%12%31%
1771
August1st to 10thNight
4426%6%6%7%6%12%13%34%
1620
11th to 20thNight
46%37%5%6%7%6%10%13%31%
1776
21st to endNight
8%8%310%6%6%6%5%8%11%29%
2160
September1st to 10thNight
5%5%29%7%7%7%7%9%13%28%
1980
11th to 20thNight
9%7%310%6%6%6%6%8%11%29%
1980
21st to endNight
8%8%310%5%6%5%5%8%9%34%
1980
October1st to 10thNight
7%6%37%5%5%5%5%7%9%41%
1980
11th to 20thNight
6%5%17%44446%8%51%
2116
21st to endNight
7%5%37%34435%8%50%
2376
November1st to 10thNight
7%42444446%8%53%
2221
11th to 20thNight
8%6%26%5%4445%6%50%
2280
21st to endNight
7%6%27%5%5%5%5%6%7%46%
2432
December1st to 10thNight
7%5%26%5%4446%8%48%
2470
11th to 20thNight
12%6%26%44335%8%47%
3042
21st to endNight
14%8%38%5%5%5%46%9%34%
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
41%5%8%21%17%8%
2837
11th to 20thDay
49%45%17%16%8%
2840
21st to endDay
36%6%7%22%23%6%
3388
February1st to 10thDay
34%5%9%20%20%11%
1900
11th to 20thDay
28%49%21%26%12%
1858
21st to endDay
30%6%11%19%24%11%
1617
March1st to 10thDay
37%10%13%20%14%6%
3435
11th to 20thDay
26%6%12%29%21%6%
3480
21st to endDay
28%5%8%32%19%8%
3815
April1st to 10thDay
28%6%15%24%19%8%
2090
11th to 20thDay
33%8%11%19%22%7%
2066
21st to endDay
24%7%11%24%27%7%
2270
May1st to 10thDay
18%8%12%27%25%10%
2470
11th to 20thDay
35%10%14%21%17%3
2333
21st to endDay
37%10%12%21%18%2
2531
June1st to 10thDay
48%12%17%18%5%
2340
11th to 20thDay
41%13%21%20%4
2340
21st to endDay
44%14%25%14%31
2340
July1st to 10thDay
49%14%27%8%1
2275
11th to 20thDay
50%14%26%10%
2271
21st to endDay
47%14%26%13%1
2405
August1st to 10thDay
47%13%29%10%
2299
11th to 20thDay
51%15%23%12%1
2125
21st to endDay
52%13%22%12%1
2178
September1st to 10thDay
46%16%22%14%2
1980
11th to 20thDay
48%12%22%13%5%
1980
21st to endDay
42%9%15%20%10%3
1980
October1st to 10thDay
41%10%11%17%12%9%
1980
11th to 20thDay
32%7%7%23%24%6%
1841
21st to endDay
29%6%12%20%21%12%
1980
November1st to 10thDay
30%6%8%25%19%12%
1857
11th to 20thDay
35%7%7%21%21%9%
1900
21st to endDay
35%6%10%21%21%7%
1744
December1st to 10thDay
33%5%12%28%17%6%
1710
11th to 20thDay
35%6%9%19%18%12%
2150
21st to endDay
47%6%9%19%15%5%
3124
January1st to 10thNight
44%6%8%17%19%6%
4109
11th to 20thNight
52%47%19%13%5%
4120
21st to endNight
41%6%10%16%19%7%
4264
February1st to 10thNight
36%5%10%19%20%10%
2280
11th to 20thNight
31%5%10%20%24%10%
2219
21st to endNight
33%5%11%19%24%8%
1834
March1st to 10thNight
45%9%11%17%13%5%
3418
11th to 20thNight
24%8%23%26%15%5%
3480
21st to endNight
31%5%9%27%21%7%
3817
April1st to 10thNight
25%6%19%26%17%7%
2090
11th to 20thNight
30%6%13%24%21%6%
2063
21st to endNight
25%5%12%26%25%7%
1919
May1st to 10thNight
17%6%13%32%23%9%
1710
11th to 20thNight
32%11%19%21%17%1
1620
21st to endNight
28%8%19%23%20%2
1745
June1st to 10thNight
42%9%22%20%7%
1620
11th to 20thNight
34%12%28%22%4
1620
21st to endNight
39%13%27%15%6%
1620
July1st to 10thNight
40%17%31%10%2
1575
11th to 20thNight
43%16%32%8%1
1566
21st to endNight
40%15%32%12%1
1672
August1st to 10thNight
34%18%36%10%1
1609
11th to 20thNight
39%15%33%13%
1776
21st to endNight
47%14%23%13%3
2160
September1st to 10thNight
42%18%25%13%2
1980
11th to 20thNight
46%12%23%16%2
1980
21st to endNight
45%8%16%19%10%2
1980
October1st to 10thNight
36%10%14%19%14%7%
1980
11th to 20thNight
31%6%10%25%23%5%
2116
21st to endNight
32%5%11%20%22%10%
2376
November1st to 10thNight
29%5%13%22%21%11%
2221
11th to 20thNight
33%5%10%21%22%8%
2280
21st to endNight
35%6%8%25%18%8%
2432
December1st to 10thNight
33%5%11%29%17%5%
2470
11th to 20thNight
36%6%8%20%19%11%
3044
21st to endNight
45%8%11%17%15%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
11%11%43%26%7%1
270
11th to 20thDay
10%11%36%31%10%2
270
21st to endDay
15%14%45%19%6%
297
February1st to 10thDay
10%11%39%26%12%1
270
11th to 20thDay
10%9%34%32%11%3
270
21st to endDay
8%10%34%31%16%1
272
March1st to 10thDay
6%11%39%33%10%1
460
11th to 20thDay
11%8%29%33%18%2
460
21st to endDay
7%10%29%34%18%2
506
April1st to 10thDay
9%8%34%28%18%3
460
11th to 20thDay
10%9%28%32%17%4
452
21st to endDay
5%6%23%33%26%6%
460
May1st to 10thDay
5%420%38%24%10%
463
11th to 20thDay
9%218%30%26%16%
456
21st to endDay
7%28%23%35%25%
485
June1st to 10thDay
14%29%22%30%23%
450
11th to 20thDay
8%16%22%30%32%
450
21st to endDay
6%1416%28%45%
450
July1st to 10thDay
6%1111%29%52%
445
11th to 20thDay
5%1114%34%46%
444
21st to endDay
9%1216%32%40%
488
August1st to 10thDay
7%2213%32%44%
446
11th to 20thDay
7%214%31%45%
439
21st to endDay
11%2318%28%37%
495
September1st to 10thDay
8%25%15%29%41%
450
11th to 20thDay
10%3425%30%27%
450
21st to endDay
9%2423%37%25%
450
October1st to 10thDay
8%416%37%27%9%
450
11th to 20thDay
7%216%35%31%8%
450
21st to endDay
8%418%38%27%4
495
November1st to 10thDay
10%6%21%32%26%5%
455
11th to 20thDay
12%5%23%38%17%5%
460
21st to endDay
9%5%32%36%16%3
304
December1st to 10thDay
6%11%34%28%14%6%
270
11th to 20thDay
9%10%37%28%14%2
270
21st to endDay
9%10%28%37%13%3
297
January1st to 10thNight
13%8%29%36%14%1
760
11th to 20thNight
12%9%24%40%13%1
760
21st to endNight
15%8%34%34%9%
836
February1st to 10thNight
15%6%30%34%14%
760
11th to 20thNight
11%7%30%37%14%1
743
21st to endNight
7%5%30%45%12%
628
March1st to 10thNight
7%6%36%40%10%1
760
11th to 20thNight
8%6%30%40%15%1
760
21st to endNight
8%6%30%41%16%1
836
April1st to 10thNight
8%5%29%41%16%1
760
11th to 20thNight
8%5%34%39%14%1
751
21st to endNight
8%427%42%18%1
740
May1st to 10thNight
5%115%47%29%3
570
11th to 20thNight
9%215%40%29%4
540
21st to endNight
6%111%37%39%6%
584
June1st to 10thNight
12%18%27%42%10%
540
11th to 20thNight
7%320%46%24%
540
21st to endNight
7%317%42%30%
540
July1st to 10thNight
8%119%47%35%
525
11th to 20thNight
6%18%46%38%
522
21st to endNight
42210%50%33%
591
August1st to 10thNight
5%110%49%34%
537
11th to 20thNight
6%118%41%43%
534
21st to endNight
11%2420%37%26%
774
September1st to 10thNight
9%25%19%45%20%
720
11th to 20thNight
12%1428%40%14%
720
21st to endNight
12%36%32%35%12%
720
October1st to 10thNight
11%218%40%24%5%
720
11th to 20thNight
8%216%38%33%3
720
21st to endNight
9%321%41%23%2
792
November1st to 10thNight
8%229%37%20%3
740
11th to 20thNight
11%224%41%20%2
760
21st to endNight
9%428%43%15%1
760
December1st to 10thNight
8%428%37%22%1
760
11th to 20thNight
12%6%24%39%19%1
760
21st to endNight
10%6%27%39%18%1
836
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