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 2024-11-04.

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
53%
25316
18%
98234
15%
25079
60%
25079
22%
60837

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
34%
752
22%
4002
11%
737
49%
737
15%
2263
January11th to 20thNight
43%
755
23%
4032
17%
740
57%
740
16%
2467
January21st to endNight
30%
829
14%
4452
11%
814
44%
814
14%
2646
February1st to 10thNight
39%
760
21%
2280
14%
760
47%
760
26%
1464
February11th to 20thNight
36%
740
21%
2218
10%
739
48%
739
27%
1379
February21st to endNight
37%
628
24%
1809
14%
628
47%
628
30%
1131
March1st to 10thNight
42%
758
19%
3417
17%
745
53%
745
19%
2340
March11th to 20thNight
41%
751
25%
3423
14%
740
51%
740
25%
1670
March21st to endNight
44%
830
18%
3736
13%
814
53%
814
22%
2132
April1st to 10thNight
46%
760
25%
2090
14%
760
53%
760
34%
1269
April11th to 20thNight
46%
751
23%
1996
15%
751
52%
751
35%
1229
April21st to endNight
57%
736
27%
1876
16%
736
62%
736
44%
1118
May1st to 10thNight
66%
562
26%
2804
21%
559
71%
559
28%
1378
May11th to 20thNight
66%
555
17%
2761
16%
541
70%
541
21%
1564
May21st to endNight
71%
595
17%
3029
17%
593
72%
593
29%
1240
June1st to 10thNight
65%
570
14%
1710
10%
570
67%
570
26%
1121
June11th to 20thNight
73%
570
13%
1710
11%
570
73%
570
26%
1126
June21st to endNight
71%
570
10%
1710
9%
570
72%
570
25%
1182
July1st to 10thNight
71%
537
7%
2762
9%
535
71%
535
13%
1894
July11th to 20thNight
73%
534
6%
2783
11%
533
73%
533
13%
1833
July21st to endNight
75%
605
7%
2987
12%
569
77%
569
15%
2047
August1st to 10thNight
72%
557
7%
2796
9%
545
73%
545
13%
1906
August11th to 20thNight
75%
544
7%
2509
9%
543
75%
543
17%
1581
August21st to endNight
61%
809
11%
3590
9%
803
62%
803
14%
2222
September1st to 10thNight
61%
760
10%
2090
9%
760
61%
760
18%
1561
September11th to 20thNight
60%
760
8%
2090
8%
760
60%
760
18%
1592
September21st to endNight
63%
760
21%
2090
20%
760
65%
760
26%
1408
October1st to 10thNight
56%
760
14%
3238
20%
740
61%
740
15%
2465
October11th to 20thNight
62%
760
24%
2693
27%
740
69%
740
27%
1726
October21st to endNight
58%
836
25%
2697
25%
814
65%
814
29%
1637
November1st to 10thNight
52%
755
25%
2264
21%
755
59%
755
31%
1377
November11th to 20thNight
47%
760
25%
2280
18%
760
57%
760
29%
1426
November21st to endNight
46%
760
24%
2465
19%
760
55%
760
28%
1488
December1st to 10thNight
47%
760
24%
2470
18%
760
57%
760
28%
1460
December11th to 20thNight
44%
759
23%
2940
17%
758
51%
758
22%
1762
December21st to endNight
44%
828
15%
4435
17%
817
53%
817
14%
2733

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
9%6%27%5%5%6%5%7%9%38%
100969
Night
10%6%26%5%5%5%47%9%42%
97994
TransparencyDay
39%9%15%17%14%5%
104724
Night
37%9%15%18%15%6%
102378
SeeingDay
10%7%21%26%22%13%
15449
Night
11%6%21%32%25%5%
25502

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%8%25%34435%6%48%
2836
11th to 20thDay
16%8%38%5%5%3346%40%
2840
21st to endDay
11%6%36%44435%7%45%
3124
February1st to 10thDay
15%8%36%44335%6%43%
1895
11th to 20thDay
12%6%25%44335%6%50%
1848
21st to endDay
11%6%26%34445%6%48%
1642
March1st to 10thDay
12%9%38%5%45%46%8%36%
3435
11th to 20thDay
7%425%44446%8%53%
3480
21st to endDay
14%7%25%44435%9%42%
3815
April1st to 10thDay
8%6%25%5%4446%8%48%
2090
11th to 20thDay
8%6%38%45%5%46%8%43%
2130
21st to endDay
5%425%45%5%46%9%51%
2317
May1st to 10thDay
6%425%445%47%10%51%
4082
11th to 20thDay
10%5%28%5%5%6%5%7%10%37%
4081
21st to endDay
6%326%5%5%5%5%8%11%45%
4476
June1st to 10thDay
11%6%27%7%7%6%7%8%9%29%
2470
11th to 20thDay
5%427%7%7%8%7%9%12%31%
2470
21st to endDay
6%6%39%7%7%8%6%9%11%28%
2470
July1st to 10thDay
7%7%39%7%8%9%7%11%12%21%
4120
11th to 20thDay
4438%7%8%8%7%10%13%28%
4120
21st to endDay
4428%7%8%9%7%10%14%26%
4466
August1st to 10thDay
11%6%38%7%7%7%6%9%12%24%
4104
11th to 20thDay
6%427%6%6%7%6%8%12%36%
4022
21st to endDay
8%5%39%7%7%7%7%9%11%27%
3840
September1st to 10thDay
11%8%39%7%8%8%6%8%10%23%
2090
11th to 20thDay
14%8%39%7%7%7%6%8%9%23%
2090
21st to endDay
12%7%39%6%6%5%5%6%7%34%
2090
October1st to 10thDay
13%6%37%6%6%6%47%8%35%
2052
11th to 20thDay
7%5%25%45%5%35%8%50%
1900
21st to endDay
9%6%26%435%45%8%49%
2090
November1st to 10thDay
11%5%26%5%45%45%9%45%
1887
11th to 20thDay
12%6%27%5%6%435%8%42%
1900
21st to endDay
12%7%37%44446%6%44%
1710
December1st to 10thDay
9%6%27%445%47%9%44%
1710
11th to 20thDay
14%8%26%5%3445%7%43%
2153
21st to endDay
15%9%37%444346%41%
3124
January1st to 10thNight
13%9%36%44336%7%42%
4109
11th to 20thNight
11%10%38%5%45%46%8%37%
4120
21st to endNight
12%8%37%5%4435%7%41%
4532
February1st to 10thNight
14%7%26%45%345%6%44%
2280
11th to 20thNight
13%6%36%443346%47%
2218
21st to endNight
11%7%26%5%35%25%6%48%
1809
March1st to 10thNight
19%11%37%443345%36%
3418
11th to 20thNight
7%5%25%4445%7%9%50%
3480
21st to endNight
12%7%36%44445%5%48%
3817
April1st to 10thNight
8%5%15%5%4446%8%49%
2090
11th to 20thNight
9%6%26%434447%52%
1996
21st to endNight
6%3234445%7%8%53%
1876
May1st to 10thNight
43145%4446%10%53%
2813
11th to 20thNight
9%5%26%5%4447%9%43%
2812
21st to endNight
331434446%10%57%
3079
June1st to 10thNight
10%5%25%5%45%6%8%12%37%
1710
11th to 20thNight
5%5%16%5%7%7%6%9%13%36%
1710
21st to endNight
8%5%26%6%6%5%5%10%12%34%
1710
July1st to 10thNight
6%6%38%8%7%7%7%9%11%29%
2840
11th to 20thNight
4427%6%6%7%6%12%15%31%
2840
21st to endNight
6%5%38%7%6%8%7%11%13%26%
3087
August1st to 10thNight
9%7%38%6%6%6%6%9%12%27%
2825
11th to 20thNight
4426%5%6%7%6%8%11%41%
2785
21st to endNight
7%6%26%6%6%6%5%8%11%37%
3800
September1st to 10thNight
11%8%38%6%6%6%6%7%11%28%
2090
11th to 20thNight
11%8%39%7%7%6%6%7%10%27%
2090
21st to endNight
9%6%37%5%6%6%47%8%40%
2090
October1st to 10thNight
12%6%38%45%5%46%6%41%
2127
11th to 20thNight
7%5%26%44435%7%54%
2280
21st to endNight
8%5%26%43435%8%51%
2508
November1st to 10thNight
11%5%25%5%4435%8%48%
2264
11th to 20thNight
11%6%36%34445%6%47%
2280
21st to endNight
12%6%25%45%445%8%45%
2465
December1st to 10thNight
12%6%25%44446%8%45%
2470
11th to 20thNight
14%8%26%33335%6%46%
3042
21st to endNight
14%8%37%445%35%6%39%
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
38%47%18%22%11%
2837
11th to 20thDay
46%5%6%14%19%11%
2840
21st to endDay
38%6%9%18%17%12%
3124
February1st to 10thDay
42%6%9%14%20%10%
1895
11th to 20thDay
35%5%9%16%23%12%
1858
21st to endDay
36%6%11%16%19%12%
1642
March1st to 10thDay
44%7%11%18%14%6%
3435
11th to 20thDay
28%6%16%19%20%11%
3480
21st to endDay
38%5%10%22%16%8%
3815
April1st to 10thDay
33%7%12%19%18%11%
2090
11th to 20thDay
38%7%10%19%19%8%
2130
21st to endDay
27%6%13%22%23%8%
2317
May1st to 10thDay
26%9%16%28%17%5%
4120
11th to 20thDay
39%9%15%21%13%2
4085
21st to endDay
27%10%15%30%16%1
4489
June1st to 10thDay
46%12%17%16%9%1
2470
11th to 20thDay
37%15%21%22%5%
2470
21st to endDay
44%15%22%12%6%
2470
July1st to 10thDay
46%16%25%12%1
4055
11th to 20thDay
40%16%34%7%2
4051
21st to endDay
39%18%31%10%1
4324
August1st to 10thDay
48%13%27%11%1
4091
11th to 20thDay
36%13%23%19%9%
4061
21st to endDay
44%14%19%22%2
3840
September1st to 10thDay
52%14%16%10%7%1
2090
11th to 20thDay
53%14%14%13%6%
2090
21st to endDay
46%8%14%16%13%2
2090
October1st to 10thDay
51%8%9%10%15%7%
3416
11th to 20thDay
28%5%7%16%32%12%
3140
21st to endDay
25%47%21%34%8%
3428
November1st to 10thDay
35%6%12%19%17%10%
1887
11th to 20thDay
40%6%9%15%20%10%
1900
21st to endDay
40%5%10%18%21%6%
1710
December1st to 10thDay
35%6%17%21%15%6%
1710
11th to 20thDay
40%7%10%16%19%8%
2150
21st to endDay
45%47%17%18%8%
3124
January1st to 10thNight
41%5%7%14%20%13%
4109
11th to 20thNight
44%5%8%16%18%9%
4120
21st to endNight
41%8%10%14%15%12%
4532
February1st to 10thNight
40%6%9%16%18%11%
2280
11th to 20thNight
38%6%8%18%18%13%
2219
21st to endNight
37%5%10%19%17%12%
1809
March1st to 10thNight
50%5%12%16%12%6%
3418
11th to 20thNight
28%7%17%22%17%9%
3480
21st to endNight
37%5%11%17%19%10%
3817
April1st to 10thNight
31%7%14%20%17%11%
2090
11th to 20thNight
32%6%10%23%20%9%
1996
21st to endNight
24%8%14%28%20%6%
1876
May1st to 10thNight
23%11%19%28%15%4
2840
11th to 20thNight
33%10%19%25%11%2
2813
21st to endNight
20%8%18%33%19%1
3087
June1st to 10thNight
36%12%24%20%9%
1710
11th to 20thNight
35%13%24%23%5%
1710
21st to endNight
37%15%25%17%5%1
1710
July1st to 10thNight
44%15%27%13%1
2795
11th to 20thNight
36%21%31%9%2
2786
21st to endNight
42%16%28%13%1
2988
August1st to 10thNight
44%14%30%10%2
2814
11th to 20thNight
32%14%25%20%10%
2812
21st to endNight
37%13%25%21%3
3800
September1st to 10thNight
46%15%20%13%5%1
2090
11th to 20thNight
48%14%17%14%6%
2090
21st to endNight
38%11%14%21%14%3
2090
October1st to 10thNight
50%9%10%12%13%7%
3543
11th to 20thNight
28%5%6%17%35%9%
3779
21st to endNight
23%5%8%21%33%10%
4120
November1st to 10thNight
33%7%10%20%17%12%
2264
11th to 20thNight
37%6%9%17%20%10%
2280
21st to endNight
38%5%12%20%18%7%
2465
December1st to 10thNight
35%6%17%22%14%6%
2470
11th to 20thNight
39%5%10%16%20%9%
3044
21st to endNight
45%6%11%16%18%5%
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%12%47%23%41
270
11th to 20thDay
6%13%41%27%11%2
270
21st to endDay
16%19%44%18%3
297
February1st to 10thDay
13%16%36%25%8%1
270
11th to 20thDay
15%13%40%23%9%
270
21st to endDay
10%14%36%31%9%
297
March1st to 10thDay
11%14%33%29%12%1
460
11th to 20thDay
13%10%32%27%14%3
460
21st to endDay
11%13%32%25%16%1
506
April1st to 10thDay
11%13%31%26%16%3
460
11th to 20thDay
9%12%30%27%14%7%
452
21st to endDay
5%8%28%31%18%10%
460
May1st to 10thDay
47%26%33%21%10%
463
11th to 20thDay
9%321%31%25%12%
487
21st to endDay
8%312%27%32%18%
529
June1st to 10thDay
13%310%29%27%18%
490
11th to 20thDay
6%215%24%28%25%
490
21st to endDay
5%29%23%35%27%
490
July1st to 10thDay
5%26%17%33%36%
485
11th to 20thDay
41417%36%38%
484
21st to endDay
6%25%20%37%29%
532
August1st to 10thDay
10%18%21%31%28%
486
11th to 20thDay
6%2418%34%36%
479
21st to endDay
10%27%24%29%27%
539
September1st to 10thDay
13%38%19%28%28%
490
11th to 20thDay
14%412%26%27%17%
490
21st to endDay
14%310%25%32%16%
490
October1st to 10thDay
16%6%23%29%21%6%
490
11th to 20thDay
7%8%21%31%27%6%
490
21st to endDay
10%5%24%35%21%5%
539
November1st to 10thDay
15%6%24%30%19%5%
467
11th to 20thDay
15%10%28%30%14%3
460
21st to endDay
10%10%37%31%11%1
270
December1st to 10thDay
10%13%31%28%17%2
270
11th to 20thDay
16%13%34%31%5%1
270
21st to endDay
15%11%31%31%11%2
297
January1st to 10thNight
15%12%33%30%10%1
760
11th to 20thNight
12%12%28%36%11%1
760
21st to endNight
17%11%36%30%6%
836
February1st to 10thNight
16%9%31%34%10%
760
11th to 20thNight
15%11%32%34%7%
743
21st to endNight
14%10%35%35%6%
628
March1st to 10thNight
10%10%31%39%9%
760
11th to 20thNight
11%10%34%34%11%1
760
21st to endNight
11%8%32%36%13%1
836
April1st to 10thNight
9%8%33%38%11%1
760
11th to 20thNight
10%9%29%34%17%1
751
21st to endNight
7%5%27%44%17%1
736
May1st to 10thNight
5%320%46%24%2
570
11th to 20thNight
7%217%38%31%4
561
21st to endNight
7%110%35%41%7%
617
June1st to 10thNight
13%29%34%36%6%
570
11th to 20thNight
6%29%28%41%14%
570
21st to endNight
8%28%26%43%14%
570
July1st to 10thNight
6%26%23%45%18%
555
11th to 20thNight
6%1318%51%21%
552
21st to endNight
5%1421%55%13%
624
August1st to 10thNight
7%15%21%50%16%
567
11th to 20thNight
5%1420%51%20%
564
21st to endNight
12%18%22%40%16%
825
September1st to 10thNight
13%27%22%43%13%
760
11th to 20thNight
13%38%29%36%10%
760
21st to endNight
12%211%29%37%9%
760
October1st to 10thNight
14%317%33%30%3
760
11th to 20thNight
9%5%16%37%29%4
760
21st to endNight
9%420%37%27%2
836
November1st to 10thNight
13%5%24%33%23%2
755
11th to 20thNight
13%7%25%33%20%1
760
21st to endNight
13%7%29%34%18%1
760
December1st to 10thNight
14%8%25%31%20%2
760
11th to 20thNight
14%9%25%33%16%2
760
21st to endNight
15%10%25%36%14%
836
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