Savannah
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Savannah clear sky chart from 2005-11-06 to 2024-02-20.

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
51%
24547
14%
79591
10%
24450
56%
24450
14%
58274

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
31%
754
18%
3987
7%
737
43%
737
9%
2590
January11th to 20thNight
39%
753
20%
3954
9%
740
48%
740
9%
2522
January21st to endNight
28%
827
11%
4441
7%
814
38%
814
9%
2959
February1st to 10thNight
35%
760
15%
2390
9%
760
43%
760
14%
1807
February11th to 20thNight
33%
741
14%
2213
6%
738
42%
738
14%
1658
February21st to endNight
36%
592
18%
1696
9%
592
44%
592
17%
1258
March1st to 10thNight
42%
720
20%
1980
12%
720
49%
720
19%
1444
March11th to 20thNight
42%
720
15%
1980
8%
720
48%
720
19%
1454
March21st to endNight
42%
792
15%
2178
8%
792
48%
792
18%
1606
April1st to 10thNight
44%
720
16%
1980
9%
720
48%
720
18%
1471
April11th to 20thNight
46%
711
19%
1829
11%
711
50%
711
22%
1334
April21st to endNight
57%
691
20%
1771
10%
691
61%
691
24%
1260
May1st to 10thNight
59%
540
17%
1620
11%
540
63%
540
19%
1143
May11th to 20thNight
64%
531
13%
1593
8%
531
67%
531
18%
1152
May21st to endNight
67%
582
12%
1744
9%
582
68%
582
16%
1306
June1st to 10thNight
65%
540
10%
1620
8%
540
66%
540
15%
1238
June11th to 20thNight
72%
540
9%
1620
7%
540
72%
540
15%
1238
June21st to endNight
70%
540
9%
1620
6%
540
71%
540
14%
1269
July1st to 10thNight
72%
525
8%
1575
6%
525
73%
525
13%
1243
July11th to 20thNight
70%
522
6%
1566
5%
522
70%
522
13%
1239
July21st to endNight
75%
591
5%
1672
4%
558
77%
558
14%
1307
August1st to 10thNight
71%
537
11%
1600
10%
534
71%
534
16%
1207
August11th to 20thNight
70%
534
7%
1598
6%
534
70%
534
12%
1278
August21st to endNight
59%
782
6%
2028
6%
782
59%
782
10%
1734
September1st to 10thNight
65%
720
10%
1980
9%
720
65%
720
15%
1571
September11th to 20thNight
61%
720
10%
1980
9%
720
62%
720
14%
1573
September21st to endNight
59%
720
13%
1980
11%
720
61%
720
14%
1570
October1st to 10thNight
57%
720
18%
2060
15%
720
61%
720
18%
1525
October11th to 20thNight
62%
720
21%
2160
19%
720
67%
720
18%
1555
October21st to endNight
56%
792
19%
2376
16%
792
61%
792
18%
1721
November1st to 10thNight
53%
740
20%
2221
17%
740
58%
740
20%
1570
November11th to 20thNight
45%
760
18%
2303
14%
760
51%
760
15%
1724
November21st to endNight
44%
760
14%
2470
10%
760
50%
760
13%
1866
December1st to 10thNight
42%
760
16%
2470
11%
760
50%
760
14%
1821
December11th to 20thNight
40%
759
17%
2920
11%
758
46%
758
10%
2080
December21st to endNight
36%
831
12%
4416
10%
817
45%
817
9%
2981

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
11%5%25%5%35%5%6%8%43%
78784
Night
11%5%25%5%35%5%6%8%44%
80416
TransparencyDay
26%35%9%13%12%4
78507
Night
27%35%9%12%13%5%
80212
SeeingDay
13%6%23%28%21%10%
14409
Night
13%5%21%32%24%5%
24578

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%425%435%5%7%7%46%
2836
11th to 20thDay
12%5%35%5%3345%9%46%
2840
21st to endDay
13%7%25%4335%5%6%45%
3124
February1st to 10thDay
14%7%35%6%35%5%5%7%41%
1787
11th to 20thDay
18%5%2442335%5%48%
1838
21st to endDay
14%7%35%433447%47%
1560
March1st to 10thDay
11%42442345%7%55%
1980
11th to 20thDay
11%6%345%3445%7%47%
1980
21st to endDay
12%5%33425%5%5%7%48%
2178
April1st to 10thDay
9%5%144345%6%8%51%
1980
11th to 20thDay
12%5%244235%5%6%52%
2080
21st to endDay
5%3145%2446%8%57%
2203
May1st to 10thDay
7%324335%5%7%9%52%
2340
11th to 20thDay
9%5%25%5%35%5%6%9%44%
2301
21st to endDay
10%425%6%46%7%7%9%39%
2531
June1st to 10thDay
9%5%36%6%47%7%8%11%33%
2340
11th to 20thDay
6%435%6%5%7%8%7%11%38%
2340
21st to endDay
7%5%26%6%5%7%8%9%11%33%
2340
July1st to 10thDay
8%5%25%6%5%8%8%9%14%31%
2340
11th to 20thDay
9%5%36%8%5%8%8%9%11%28%
2340
21st to endDay
7%437%6%5%7%7%9%13%32%
2547
August1st to 10thDay
10%5%25%7%5%8%9%9%12%30%
2327
11th to 20thDay
8%6%37%7%5%6%8%9%13%28%
2293
21st to endDay
14%8%38%7%5%6%7%8%10%25%
2313
September1st to 10thDay
10%5%48%8%5%6%7%7%9%31%
1980
11th to 20thDay
14%7%36%7%45%6%6%9%33%
1980
21st to endDay
13%6%35%7%46%6%6%7%38%
1980
October1st to 10thDay
12%6%25%6%345%5%5%48%
1898
11th to 20thDay
10%413324447%58%
1800
21st to endDay
10%5%3442345%6%53%
1980
November1st to 10thDay
11%423434446%55%
1857
11th to 20thDay
12%5%245%34347%51%
1874
21st to endDay
13%5%34424446%50%
1710
December1st to 10thDay
11%6%35%5%345%48%46%
1710
11th to 20thDay
15%6%243335%45%50%
2153
21st to endDay
17%9%35%5%33446%42%
3124
January1st to 10thNight
15%5%245%35%5%5%6%43%
4109
11th to 20thNight
10%6%35%5%35%5%6%7%44%
4120
21st to endNight
14%8%36%5%34445%43%
4532
February1st to 10thNight
16%6%35%6%3445%6%42%
2390
11th to 20thNight
16%7%25%424446%47%
2213
21st to endNight
13%5%25%5%36%5%48%44%
1696
March1st to 10thNight
9%435%43436%7%53%
1980
11th to 20thNight
11%5%26%5%2445%8%48%
1980
21st to endNight
10%5%25%434448%50%
2178
April1st to 10thNight
11%424435%5%5%8%50%
1980
11th to 20thNight
12%425%4245%47%52%
1829
21st to endNight
7%42442346%9%56%
1771
May1st to 10thNight
7%424425%45%8%56%
1620
11th to 20thNight
6%415%4345%7%9%51%
1592
21st to endNight
11%4245%36%6%7%9%42%
1744
June1st to 10thNight
10%5%35%6%45%6%9%13%35%
1620
11th to 20thNight
6%5%25%5%46%7%9%12%38%
1620
21st to endNight
6%426%5%48%9%9%14%33%
1620
July1st to 10thNight
8%435%6%5%5%7%8%14%36%
1620
11th to 20thNight
7%436%7%47%9%8%13%32%
1620
21st to endNight
5%425%6%48%8%10%12%36%
1771
August1st to 10thNight
7%426%7%46%8%9%12%34%
1611
11th to 20thNight
7%437%7%5%7%9%10%12%30%
1598
21st to endNight
12%7%37%7%5%6%6%8%11%28%
2028
September1st to 10thNight
11%6%36%5%46%6%8%11%34%
1980
11th to 20thNight
11%6%26%8%46%6%7%8%37%
1980
21st to endNight
12%6%37%6%35%5%7%7%37%
1980
October1st to 10thNight
12%6%2443445%7%48%
2060
11th to 20thNight
9%424434346%57%
2160
21st to endNight
10%425%43345%5%55%
2376
November1st to 10thNight
10%435%424345%56%
2221
11th to 20thNight
13%5%24434447%50%
2303
21st to endNight
12%6%35%5%35%45%6%47%
2470
December1st to 10thNight
13%5%25%5%345%6%8%44%
2470
11th to 20thNight
15%6%25%5%24345%49%
3042
21st to endNight
17%8%35%5%35%45%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
26%25%6%16%17%10%
2837
11th to 20thDay
28%25%5%15%19%7%
2840
21st to endDay
33%22%9%11%16%9%
3124
February1st to 10thDay
30%34%5%12%14%6%
1787
11th to 20thDay
28%34%411%16%7%
1848
21st to endDay
24%35%7%14%14%7%
1560
March1st to 10thDay
21%35%6%14%17%7%
1980
11th to 20thDay
23%37%10%13%10%7%
1980
21st to endDay
24%37%10%15%13%3
2178
April1st to 10thDay
20%37%8%15%14%5%
1980
11th to 20thDay
20%35%7%14%17%7%
2080
21st to endDay
18%36%9%18%15%4
2203
May1st to 10thDay
19%37%10%20%10%4
2340
11th to 20thDay
25%37%14%14%9%1
2305
21st to endDay
27%38%11%14%10%
2531
June1st to 10thDay
27%38%14%13%7%
2340
11th to 20thDay
26%38%12%17%6%
2340
21st to endDay
27%41%13%12%6%1
2340
July1st to 10thDay
29%40%14%11%41
2275
11th to 20thDay
31%40%15%10%4
2271
21st to endDay
28%41%17%13%1
2405
August1st to 10thDay
27%39%16%14%4
2314
11th to 20thDay
32%40%16%10%3
2293
21st to endDay
39%39%11%9%3
2313
September1st to 10thDay
30%39%13%10%7%1
1980
11th to 20thDay
32%38%10%10%7%2
1980
21st to endDay
30%36%9%10%12%3
1980
October1st to 10thDay
25%36%5%11%15%8%
1898
11th to 20thDay
21%37%5%11%20%7%
1800
21st to endDay
22%36%5%11%17%8%
1980
November1st to 10thDay
16%39%412%17%11%
1857
11th to 20thDay
22%39%5%13%15%7%
1874
21st to endDay
25%38%5%15%12%6%
1710
December1st to 10thDay
22%39%9%14%10%6%
1710
11th to 20thDay
27%31%5%15%20%2
2150
21st to endDay
32%24%5%14%21%4
3124
January1st to 10thNight
31%25%5%10%19%10%
4109
11th to 20thNight
30%24%5%14%21%6%
4120
21st to endNight
37%22%6%9%17%9%
4532
February1st to 10thNight
30%33%5%12%13%7%
2390
11th to 20thNight
28%34%6%9%13%10%
2214
21st to endNight
25%36%6%16%10%8%
1696
March1st to 10thNight
22%36%7%11%16%9%
1980
11th to 20thNight
21%37%12%14%9%7%
1980
21st to endNight
23%36%10%15%12%4
2178
April1st to 10thNight
23%37%8%13%14%6%
1980
11th to 20thNight
21%35%5%15%16%8%
1829
21st to endNight
17%36%10%17%16%4
1771
May1st to 10thNight
20%36%11%17%12%4
1620
11th to 20thNight
20%39%16%15%9%1
1593
21st to endNight
23%39%12%15%10%1
1745
June1st to 10thNight
27%37%15%13%7%
1620
11th to 20thNight
26%39%15%16%4
1620
21st to endNight
26%41%16%13%41
1620
July1st to 10thNight
28%40%13%14%32
1575
11th to 20thNight
28%41%18%11%3
1566
21st to endNight
25%42%20%12%1
1672
August1st to 10thNight
23%40%18%15%3
1600
11th to 20thNight
31%39%17%12%2
1598
21st to endNight
37%39%13%8%2
2028
September1st to 10thNight
28%39%13%11%7%2
1980
11th to 20thNight
28%39%12%11%8%1
1980
21st to endNight
30%37%7%10%12%2
1980
October1st to 10thNight
24%36%6%12%15%7%
2060
11th to 20thNight
21%37%412%18%8%
2160
21st to endNight
22%37%5%11%15%10%
2376
November1st to 10thNight
16%40%5%10%19%11%
2221
11th to 20thNight
24%38%412%14%7%
2303
21st to endNight
27%38%6%12%11%6%
2470
December1st to 10thNight
23%38%10%12%12%4
2470
11th to 20thNight
28%32%6%12%20%2
3044
21st to endNight
34%25%6%15%17%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
13%15%46%21%4
270
11th to 20thDay
10%13%41%25%9%3
270
21st to endDay
23%19%39%15%3
297
February1st to 10thDay
17%14%41%22%6%
270
11th to 20thDay
24%11%43%20%2
267
21st to endDay
15%13%42%23%6%1
278
March1st to 10thDay
14%11%36%26%12%1
420
11th to 20thDay
16%10%39%22%11%2
420
21st to endDay
15%9%40%25%10%1
462
April1st to 10thDay
15%10%36%24%12%2
420
11th to 20thDay
12%11%33%24%12%8%
412
21st to endDay
6%7%29%31%19%8%
420
May1st to 10thDay
6%10%33%27%15%9%
423
11th to 20thDay
10%219%37%20%13%
447
21st to endDay
12%215%26%29%16%
485
June1st to 10thDay
12%116%29%26%17%
450
11th to 20thDay
11%214%28%20%25%
450
21st to endDay
7%211%31%29%20%
450
July1st to 10thDay
6%2427%37%25%
445
11th to 20thDay
7%1327%37%25%
444
21st to endDay
7%25%34%36%17%
488
August1st to 10thDay
11%15%27%37%18%
446
11th to 20thDay
8%1326%38%24%
439
21st to endDay
16%35%22%34%20%
495
September1st to 10thDay
12%26%28%36%16%
450
11th to 20thDay
17%110%33%27%12%
450
21st to endDay
14%210%30%30%14%
450
October1st to 10thDay
15%223%32%19%9%
450
11th to 20thDay
10%5%23%30%23%8%
450
21st to endDay
12%5%25%34%19%6%
495
November1st to 10thDay
16%5%25%31%18%5%
455
11th to 20thDay
19%5%35%29%10%1
434
21st to endDay
16%8%33%32%10%2
270
December1st to 10thDay
16%9%39%24%10%2
270
11th to 20thDay
19%11%33%27%9%1
270
21st to endDay
24%7%32%28%8%1
297
January1st to 10thNight
14%11%39%28%8%
760
11th to 20thNight
14%10%30%34%12%1
760
21st to endNight
19%9%37%30%5%
836
February1st to 10thNight
20%7%34%30%9%
760
11th to 20thNight
21%10%30%33%5%
742
21st to endNight
17%8%33%35%7%
592
March1st to 10thNight
12%7%33%37%11%
720
11th to 20thNight
13%8%30%35%13%1
720
21st to endNight
11%9%30%34%14%1
792
April1st to 10thNight
13%7%31%34%14%1
720
11th to 20thNight
14%7%28%30%20%2
711
21st to endNight
9%5%24%40%19%2
691
May1st to 10thNight
8%321%40%25%3
540
11th to 20thNight
8%217%39%27%7%
531
21st to endNight
12%28%32%35%12%
584
June1st to 10thNight
13%18%38%33%7%
540
11th to 20thNight
8%26%33%34%18%
540
21st to endNight
7%29%32%38%12%
540
July1st to 10thNight
9%2425%46%14%
525
11th to 20thNight
9%1222%51%15%
522
21st to endNight
6%1234%47%8%
591
August1st to 10thNight
10%1426%45%15%
537
11th to 20thNight
8%1323%49%16%
534
21st to endNight
16%3423%40%14%
782
September1st to 10thNight
13%35%24%46%10%
720
11th to 20thNight
12%28%31%41%7%
720
21st to endNight
17%28%29%36%8%
720
October1st to 10thNight
14%217%32%28%6%
720
11th to 20thNight
11%416%35%29%6%
720
21st to endNight
12%420%35%26%4
792
November1st to 10thNight
13%6%21%36%22%3
740
11th to 20thNight
17%6%26%34%16%2
760
21st to endNight
15%6%29%32%17%1
760
December1st to 10thNight
16%7%28%33%15%1
760
11th to 20thNight
18%7%26%33%14%2
760
21st to endNight
21%7%29%30%12%
836
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