Jacksonville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jacksonville clear sky chart from 2005-11-06 to 2024-01-16.

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
42%
24510
20%
74741
12%
24457
51%
24457
25%
46976

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
25%
758
23%
2459
10%
757
41%
757
21%
1484
January11th to 20thNight
33%
744
24%
2417
11%
744
49%
744
20%
1521
January21st to endNight
25%
792
25%
2574
11%
792
44%
792
22%
1574
February1st to 10thNight
27%
720
18%
2340
9%
720
39%
720
22%
1465
February11th to 20thNight
20%
702
20%
2149
7%
700
35%
700
20%
1406
February21st to endNight
25%
592
23%
1731
11%
592
39%
592
20%
1134
March1st to 10thNight
27%
720
26%
1980
12%
720
41%
720
31%
1205
March11th to 20thNight
26%
720
18%
1980
9%
720
36%
720
22%
1351
March21st to endNight
29%
792
22%
2178
10%
792
40%
792
28%
1387
April1st to 10thNight
29%
720
23%
1800
7%
720
39%
720
30%
1161
April11th to 20thNight
37%
711
23%
1775
10%
711
44%
711
34%
1137
April21st to endNight
38%
720
25%
1800
11%
720
44%
720
38%
1096
May1st to 10thNight
36%
720
17%
1800
7%
720
41%
720
32%
1169
May11th to 20thNight
46%
565
16%
1626
9%
565
51%
565
27%
1059
May21st to endNight
63%
582
15%
1744
11%
582
65%
582
29%
1091
June1st to 10thNight
56%
406
16%
1486
16%
406
58%
406
22%
924
June11th to 20thNight
61%
360
16%
1440
17%
360
65%
360
24%
845
June21st to endNight
58%
517
14%
1597
11%
517
61%
517
25%
1047
July1st to 10thNight
66%
525
11%
1575
10%
525
66%
525
23%
1073
July11th to 20thNight
69%
522
11%
1566
9%
522
71%
522
27%
1018
July21st to endNight
64%
591
13%
1672
9%
558
66%
558
26%
1104
August1st to 10thNight
64%
537
10%
1600
8%
534
64%
534
23%
1097
August11th to 20thNight
61%
701
13%
1765
9%
701
61%
701
24%
1284
August21st to endNight
61%
792
14%
1980
8%
792
62%
792
26%
1393
September1st to 10thNight
63%
720
19%
1800
13%
720
65%
720
30%
1219
September11th to 20thNight
54%
720
22%
1800
17%
720
57%
720
28%
1251
September21st to endNight
48%
720
16%
2070
12%
720
53%
720
22%
1439
October1st to 10thNight
52%
720
23%
2160
21%
720
57%
720
29%
1345
October11th to 20thNight
47%
720
27%
2160
21%
720
58%
720
33%
1258
October21st to endNight
48%
792
30%
2376
21%
792
60%
792
34%
1355
November1st to 10thNight
46%
740
25%
2221
18%
740
55%
740
30%
1329
November11th to 20thNight
35%
760
26%
2339
14%
760
50%
760
27%
1422
November21st to endNight
40%
760
26%
2498
17%
760
54%
760
28%
1437
December1st to 10thNight
33%
760
20%
2660
10%
760
47%
760
19%
1695
December11th to 20thNight
35%
760
23%
3178
16%
758
48%
758
21%
1811
December21st to endNight
32%
829
16%
4445
12%
817
45%
817
14%
2390

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
13%6%35%5%35%5%6%8%41%
74586
Night
13%6%25%5%345%5%8%45%
75202
TransparencyDay
39%8%13%19%16%4
74307
Night
38%7%13%20%18%5%
75000
SeeingDay
16%12%27%25%14%5%
14361
Night
15%10%26%30%16%2
24522

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
14%6%2442345%5%51%
1706
11th to 20thDay
14%6%36%4335%6%5%45%
1671
21st to endDay
16%8%345%33446%45%
1782
February1st to 10thDay
16%6%35%5%4445%7%42%
1620
11th to 20thDay
19%5%35%5%23336%46%
1696
21st to endDay
16%6%36%5%25%5%5%7%41%
1522
March1st to 10thDay
13%5%34423446%53%
1980
11th to 20thDay
15%6%26%5%3445%9%41%
1980
21st to endDay
15%7%26%5%345%5%7%41%
2178
April1st to 10thDay
12%5%2442345%6%53%
2160
11th to 20thDay
10%425%5%245%6%8%50%
2134
21st to endDay
10%425%43445%7%50%
2160
May1st to 10thDay
9%5%245%46%6%6%9%44%
2160
11th to 20thDay
15%5%26%6%46%6%6%7%37%
2281
21st to endDay
10%6%26%6%46%5%8%10%36%
2531
June1st to 10thDay
12%5%37%7%46%6%7%9%34%
2465
11th to 20thDay
10%425%5%36%7%9%12%37%
2520
21st to endDay
9%435%6%5%8%7%8%13%31%
2350
July1st to 10thDay
10%6%36%6%46%7%9%12%31%
2340
11th to 20thDay
9%5%26%6%5%7%8%9%12%32%
2340
21st to endDay
8%5%36%7%48%7%9%12%31%
2547
August1st to 10thDay
12%6%37%6%5%6%8%8%10%29%
2319
11th to 20thDay
12%5%37%7%46%7%7%11%31%
2126
21st to endDay
12%7%36%7%5%7%7%8%9%30%
2376
September1st to 10thDay
11%6%36%6%35%6%8%10%36%
2160
11th to 20thDay
14%8%36%6%45%7%6%8%35%
2160
21st to endDay
17%8%37%6%25%5%6%7%36%
1884
October1st to 10thDay
16%6%35%5%23446%44%
1800
11th to 20thDay
12%5%34434346%54%
1800
21st to endDay
11%5%24424445%54%
1980
November1st to 10thDay
13%5%24434446%53%
1857
11th to 20thDay
13%6%34434446%51%
1838
21st to endDay
12%425%5%2435%7%50%
1677
December1st to 10thDay
15%7%45%5%35%5%5%8%39%
1520
11th to 20thDay
16%5%24323335%53%
1910
21st to endDay
14%7%36%434446%45%
3056
January1st to 10thNight
13%7%35%5%33446%47%
2459
11th to 20thNight
12%6%26%4445%5%6%44%
2417
21st to endNight
16%6%25%5%2445%5%46%
2574
February1st to 10thNight
19%6%24434446%43%
2340
11th to 20thNight
19%7%25%42445%7%41%
2147
21st to endNight
16%6%36%5%25%5%5%7%41%
1731
March1st to 10thNight
13%434433437%53%
1980
11th to 20thNight
14%7%35%6%35%5%8%7%37%
1980
21st to endNight
13%6%25%5%3445%7%46%
2178
April1st to 10thNight
11%5%35%43446%5%50%
1800
11th to 20thNight
11%5%25%4345%47%50%
1775
21st to endNight
8%414435%46%8%55%
1800
May1st to 10thNight
10%435%6%35%5%6%9%46%
1800
11th to 20thNight
13%6%345%35%5%6%9%41%
1626
21st to endNight
10%425%4446%6%11%45%
1744
June1st to 10thNight
10%5%37%6%36%47%9%40%
1486
11th to 20thNight
9%5%25%5%445%7%12%43%
1440
21st to endNight
10%6%25%6%36%5%7%13%37%
1597
July1st to 10thNight
7%5%26%6%46%8%8%12%35%
1620
11th to 20thNight
6%425%6%46%7%8%12%38%
1620
21st to endNight
6%5%36%6%46%6%8%12%37%
1771
August1st to 10thNight
8%6%36%6%37%7%8%11%36%
1611
11th to 20thNight
10%5%37%7%46%7%7%9%36%
1765
21st to endNight
11%6%246%46%6%8%11%35%
1980
September1st to 10thNight
11%415%5%35%5%7%10%44%
1800
11th to 20thNight
12%6%36%6%35%5%6%8%42%
1800
21st to endNight
17%8%36%5%345%5%7%38%
2070
October1st to 10thNight
14%5%25%5%34446%48%
2160
11th to 20thNight
11%5%25%434446%53%
2160
21st to endNight
11%5%24334446%55%
2376
November1st to 10thNight
13%5%24424446%52%
2221
11th to 20thNight
14%7%35%423346%48%
2339
21st to endNight
12%5%24424448%51%
2498
December1st to 10thNight
16%7%35%5%3445%7%41%
2660
11th to 20thNight
17%6%24423446%48%
3285
21st to endNight
15%6%25%433346%47%
4592

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
36%6%11%18%22%7%
1707
11th to 20thDay
41%5%9%17%22%6%
1671
21st to endDay
42%36%19%23%7%
1782
February1st to 10thDay
42%411%20%17%5%
1620
11th to 20thDay
42%5%8%16%23%7%
1705
21st to endDay
42%6%10%18%16%8%
1522
March1st to 10thDay
34%5%11%19%24%8%
1980
11th to 20thDay
40%7%12%19%16%6%
1980
21st to endDay
43%7%10%16%19%5%
2178
April1st to 10thDay
32%6%10%23%23%7%
2160
11th to 20thDay
31%6%13%23%18%9%
2134
21st to endDay
32%7%13%22%21%4
2160
May1st to 10thDay
34%9%16%22%16%3
2160
11th to 20thDay
42%9%14%22%11%1
2285
21st to endDay
40%10%16%23%10%1
2531
June1st to 10thDay
44%10%15%20%11%1
2465
11th to 20thDay
36%13%19%21%10%1
2520
21st to endDay
41%13%18%19%8%1
2350
July1st to 10thDay
40%14%19%18%7%1
2275
11th to 20thDay
39%15%20%18%7%1
2271
21st to endDay
39%13%22%22%4
2405
August1st to 10thDay
46%13%21%15%5%
2306
11th to 20thDay
44%13%18%16%8%
2126
21st to endDay
45%13%17%18%6%1
2376
September1st to 10thDay
40%14%16%14%13%3
2160
11th to 20thDay
44%9%11%16%16%4
2160
21st to endDay
46%7%12%17%15%3
1884
October1st to 10thDay
41%5%9%19%24%2
1800
11th to 20thDay
33%49%25%22%8%
1800
21st to endDay
32%48%19%29%8%
1980
November1st to 10thDay
33%5%8%18%27%8%
1857
11th to 20thDay
36%48%18%24%9%
1838
21st to endDay
35%5%8%22%23%7%
1677
December1st to 10thDay
44%7%10%20%14%5%
1520
11th to 20thDay
36%46%20%24%10%
1906
21st to endDay
41%410%21%22%2
3056
January1st to 10thNight
39%48%20%22%6%
2459
11th to 20thNight
41%6%10%19%18%6%
2417
21st to endNight
40%47%20%22%8%
2574
February1st to 10thNight
42%410%16%20%7%
2340
11th to 20thNight
44%49%16%20%6%
2149
21st to endNight
43%6%10%16%18%8%
1731
March1st to 10thNight
33%5%9%22%22%8%
1980
11th to 20thNight
43%7%12%16%17%6%
1980
21st to endNight
38%5%13%21%18%5%
2178
April1st to 10thNight
35%5%13%17%24%7%
1800
11th to 20thNight
34%6%13%21%18%8%
1775
21st to endNight
28%7%14%28%19%4
1800
May1st to 10thNight
34%7%17%22%17%3
1800
11th to 20thNight
38%8%16%23%13%1
1627
21st to endNight
33%11%19%24%11%1
1745
June1st to 10thNight
41%7%17%25%10%1
1486
11th to 20thNight
34%10%20%26%9%1
1440
21st to endNight
38%11%19%23%8%1
1597
July1st to 10thNight
38%14%20%19%8%1
1575
11th to 20thNight
34%13%25%21%7%
1566
21st to endNight
35%13%22%24%5%1
1672
August1st to 10thNight
38%14%25%19%4
1600
11th to 20thNight
40%14%19%18%8%1
1765
21st to endNight
39%13%20%21%6%2
1980
September1st to 10thNight
35%12%20%16%14%3
1800
11th to 20thNight
40%10%12%20%15%3
1800
21st to endNight
46%8%12%18%15%2
2070
October1st to 10thNight
37%6%9%21%22%5%
2160
11th to 20thNight
33%5%9%23%23%7%
2160
21st to endNight
32%49%22%26%9%
2376
November1st to 10thNight
34%6%9%16%26%8%
2221
11th to 20thNight
38%48%15%25%9%
2339
21st to endNight
34%5%7%23%24%7%
2498
December1st to 10thNight
43%7%12%16%17%5%
2660
11th to 20thNight
38%48%19%24%7%
3288
21st to endNight
39%48%22%23%4
4592

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
21%28%37%11%3
270
11th to 20thDay
18%25%40%14%3
257
21st to endDay
23%29%31%15%2
264
February1st to 10thDay
27%20%37%14%3
240
11th to 20thDay
30%23%31%14%2
364
21st to endDay
21%25%34%15%41
346
March1st to 10thDay
20%20%37%18%6%
420
11th to 20thDay
24%24%35%11%6%1
420
21st to endDay
21%21%35%15%8%1
462
April1st to 10thDay
23%20%30%19%8%1
420
11th to 20thDay
15%19%32%20%8%5%
412
21st to endDay
15%16%32%24%11%3
420
May1st to 10thDay
13%19%35%20%10%4
423
11th to 20thDay
17%9%28%30%13%4
447
21st to endDay
16%5%21%30%19%8%
485
June1st to 10thDay
11%6%28%34%17%4
450
11th to 20thDay
14%5%20%32%18%11%
450
21st to endDay
10%424%34%21%7%
450
July1st to 10thDay
12%214%37%26%9%
445
11th to 20thDay
10%314%34%28%9%
444
21st to endDay
9%220%38%23%7%
488
August1st to 10thDay
15%419%31%21%11%
446
11th to 20thDay
13%315%29%25%14%
439
21st to endDay
12%415%30%25%15%
495
September1st to 10thDay
12%318%32%21%14%
450
11th to 20thDay
18%6%21%29%16%9%
450
21st to endDay
20%6%23%26%17%8%
450
October1st to 10thDay
18%6%25%26%17%8%
450
11th to 20thDay
12%10%26%32%14%5%
450
21st to endDay
13%12%28%28%16%4
495
November1st to 10thDay
19%10%30%25%12%3
455
11th to 20thDay
15%19%33%23%9%1
430
21st to endDay
14%16%31%21%16%2
337
December1st to 10thDay
19%21%37%18%6%
180
11th to 20thDay
21%18%34%17%9%1
180
21st to endDay
20%18%35%16%9%1
277
January1st to 10thNight
18%20%32%23%7%
760
11th to 20thNight
17%16%29%31%7%
744
21st to endNight
19%16%35%26%3
792
February1st to 10thNight
23%14%33%24%5%
720
11th to 20thNight
23%18%35%21%2
703
21st to endNight
19%18%31%24%6%
592
March1st to 10thNight
16%16%38%24%5%
720
11th to 20thNight
19%15%37%22%7%1
720
21st to endNight
17%14%36%25%7%
792
April1st to 10thNight
15%17%35%26%7%
720
11th to 20thNight
13%13%34%27%12%1
711
21st to endNight
11%10%38%32%9%1
720
May1st to 10thNight
11%12%37%30%9%1
720
11th to 20thNight
17%7%25%37%14%1
565
21st to endNight
11%316%35%29%5%
584
June1st to 10thNight
12%221%44%19%3
406
11th to 20thNight
11%319%38%24%5%
360
21st to endNight
13%316%42%23%3
517
July1st to 10thNight
8%213%41%32%5%
525
11th to 20thNight
7%211%35%37%8%
522
21st to endNight
9%114%41%32%4
591
August1st to 10thNight
9%115%32%36%7%
537
11th to 20thNight
11%212%39%30%7%
701
21st to endNight
14%213%30%33%9%
792
September1st to 10thNight
13%312%32%32%8%
720
11th to 20thNight
15%118%38%23%6%
720
21st to endNight
22%418%28%24%4
720
October1st to 10thNight
17%5%21%29%22%6%
720
11th to 20thNight
14%7%27%31%19%3
720
21st to endNight
14%8%25%32%18%3
792
November1st to 10thNight
14%9%27%32%15%2
740
11th to 20thNight
18%12%31%26%12%2
760
21st to endNight
14%12%29%29%15%1
760
December1st to 10thNight
20%14%28%29%8%1
760
11th to 20thNight
18%13%29%30%10%1
760
21st to endNight
19%14%30%29%8%1
836
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