Charleston
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Charleston clear sky chart from 2005-11-05 to 2017-04-08.

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
46%
15438
21%
45378
14%
15399
54%
15399
24%
28527

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 15thNight
29%
716
22%
2327
9%
716
44%
716
19%
1445
January16th to endNight
29%
768
23%
2496
13%
768
42%
768
23%
1501
February1st to 15thNight
32%
704
22%
2255
12%
701
46%
701
21%
1364
February16th to endNight
32%
631
26%
1795
12%
631
45%
631
24%
1138
March1st to 15thNight
36%
720
26%
1980
15%
720
47%
720
29%
1208
March16th to endNight
39%
768
21%
2112
12%
768
47%
768
27%
1319
April1st to 15thNight
43%
690
26%
1828
15%
690
51%
690
31%
1114
April16th to endNight
43%
660
25%
1650
11%
660
51%
660
31%
1019
May1st to 15thNight
51%
530
22%
1521
13%
530
55%
530
28%
922
May16th to endNight
53%
513
17%
1540
10%
513
58%
513
24%
945
June1st to 15thNight
61%
495
15%
1485
12%
495
62%
495
25%
937
June16th to endNight
60%
495
13%
1485
9%
495
62%
495
25%
938
July1st to 15thNight
62%
465
13%
1395
12%
465
63%
465
23%
907
July16th to endNight
63%
522
10%
1469
9%
489
67%
489
22%
974
August1st to 15thNight
64%
494
14%
1474
11%
491
65%
491
20%
1013
August16th to endNight
57%
678
13%
1728
9%
678
59%
678
20%
1300
September1st to 15thNight
62%
660
18%
1760
15%
660
63%
660
24%
1238
September16th to endNight
50%
657
12%
1815
6%
657
55%
657
17%
1319
October1st to 15thNight
51%
660
27%
1963
25%
660
57%
660
30%
1174
October16th to endNight
54%
704
32%
2112
25%
704
65%
704
34%
1191
November1st to 15thNight
47%
700
30%
2101
21%
700
59%
700
34%
1166
November16th to endNight
43%
720
26%
2251
17%
720
55%
720
27%
1318
December1st to 15thNight
37%
720
21%
2340
14%
720
46%
720
20%
1474
December16th to endNight
32%
768
22%
2496
13%
768
44%
768
18%
1603

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
10%5%25%5%35%5%6%8%42%
45873
Night
10%5%25%5%3446%8%44%
45575
TransparencyDay
36%7%15%21%14%4
45574
Night
37%6%13%20%15%6%
45378
SeeingDay
10%11%15%25%25%11%
5166
Night
11%18%15%26%22%5%
15445

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 15thDay
14%6%25%5%3335%7%43%
1611
16th to endDay
15%5%25%5%22346%45%
1728
February1st to 15thDay
14%6%15%433446%44%
1604
16th to endDay
12%5%35%423335%48%
1676
March1st to 15thDay
12%424424347%50%
1980
16th to endDay
10%5%2442446%6%47%
2111
April1st to 15thDay
10%31432445%6%54%
1958
16th to endDay
6%32432445%9%53%
1980
May1st to 15thDay
8%4246%35%5%5%7%45%
2108
16th to endDay
8%425%435%6%7%9%41%
2223
June1st to 15thDay
6%3245%37%7%9%12%37%
2145
16th to endDay
5%325%5%47%6%9%12%37%
2145
July1st to 15thDay
9%5%345%47%7%7%11%32%
2145
16th to endDay
7%5%26%6%46%8%8%11%31%
2283
August1st to 15thDay
7%436%7%47%8%9%12%27%
2145
16th to endDay
11%6%27%7%5%7%8%8%10%23%
2110
September1st to 15thDay
12%4247%36%6%7%10%35%
1867
16th to endDay
15%9%37%5%25%5%6%8%30%
1815
October1st to 15thDay
13%424423345%51%
1667
16th to endDay
9%413423345%57%
1760
November1st to 15thDay
9%5%23323345%56%
1757
16th to endDay
10%42432435%5%53%
1707
December1st to 15thDay
14%6%25%434436%44%
1620
16th to endDay
13%6%2432445%7%44%
1728
January1st to 15thNight
11%6%15%5%34447%44%
2327
16th to endNight
14%6%34423345%47%
2496
February1st to 15thNight
14%5%25%42344448%
2246
16th to endNight
10%7%25%5%24346%46%
1795
March1st to 15thNight
8%5%25%424447%48%
1980
16th to endNight
10%5%245%2335%8%47%
2112
April1st to 15thNight
12%314424347%50%
1828
16th to endNight
8%42432346%8%51%
1650
May1st to 15thNight
7%5%15%435%46%8%48%
1520
16th to endNight
8%314435%5%7%10%44%
1538
June1st to 15thNight
6%423445%7%7%12%39%
1485
16th to endNight
34245%35%7%9%13%39%
1485
July1st to 15thNight
7%425%5%46%7%9%12%35%
1485
16th to endNight
7%325%7%36%6%9%12%34%
1577
August1st to 15thNight
8%3246%36%8%11%14%29%
1485
16th to endNight
10%6%36%8%46%5%7%11%28%
1728
September1st to 15thNight
9%425%6%445%7%9%38%
1760
16th to endNight
15%6%26%5%446%7%10%30%
1815
October1st to 15thNight
13%5%23423347%49%
1963
16th to endNight
8%41432345%457%
2112
November1st to 15thNight
9%5%13313346%57%
2101
16th to endNight
11%5%25%424346%50%
2251
December1st to 15thNight
14%5%25%42435%6%44%
2340
16th to endNight
14%6%35%5%34446%40%
2496

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 15thDay
41%410%18%19%6%
1612
16th to endDay
40%47%20%20%6%
1728
February1st to 15thDay
41%37%18%21%7%
1606
16th to endDay
38%47%21%20%6%
1676
March1st to 15thDay
35%310%22%18%8%
1980
16th to endDay
35%5%13%22%16%5%
2112
April1st to 15thDay
29%414%24%19%7%
1958
16th to endDay
27%6%13%23%21%8%
1980
May1st to 15thDay
35%6%15%26%13%1
2108
16th to endDay
34%8%19%25%11%
2227
June1st to 15thDay
32%11%24%22%8%
2145
16th to endDay
33%12%19%25%7%
2145
July1st to 15thDay
37%10%25%20%5%
2006
16th to endDay
37%11%26%19%4
2128
August1st to 15thDay
41%12%21%19%5%
2132
16th to endDay
46%13%18%17%3
2110
September1st to 15thDay
40%10%17%17%10%3
1867
16th to endDay
47%7%15%16%10%2
1815
October1st to 15thDay
33%411%20%21%7%
1667
16th to endDay
28%48%20%27%10%
1760
November1st to 15thDay
31%38%21%23%10%
1757
16th to endDay
32%410%21%21%10%
1707
December1st to 15thDay
41%411%21%14%6%
1620
16th to endDay
40%414%19%15%6%
1728
January1st to 15thNight
40%5%8%18%19%7%
2327
16th to endNight
39%38%16%22%9%
2496
February1st to 15thNight
38%37%20%18%10%
2255
16th to endNight
40%39%17%19%9%
1795
March1st to 15thNight
33%5%11%21%18%8%
1980
16th to endNight
35%5%14%19%16%8%
2112
April1st to 15thNight
32%412%21%21%8%
1828
16th to endNight
30%6%11%22%21%7%
1650
May1st to 15thNight
33%6%15%24%17%2
1521
16th to endNight
32%9%18%26%11%
1540
June1st to 15thNight
34%10%23%24%7%
1485
16th to endNight
31%13%23%24%6%
1485
July1st to 15thNight
36%11%24%20%6%
1395
16th to endNight
36%13%21%23%4
1469
August1st to 15thNight
39%14%20%20%4
1474
16th to endNight
46%12%18%18%3
1728
September1st to 15thNight
41%11%16%18%10%2
1760
16th to endNight
48%9%15%14%9%1
1815
October1st to 15thNight
35%411%20%21%7%
1963
16th to endNight
29%48%18%25%13%
2112
November1st to 15thNight
29%39%20%24%12%
2101
16th to endNight
34%410%16%22%11%
2251
December1st to 15thNight
41%412%17%15%6%
2340
16th to endNight
44%49%20%13%7%
2496

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 15thDay
12%12%26%28%14%5%
90
16th to endDay
14%9%41%25%8%1
96
February1st to 15thDay
14%14%34%27%8%
90
16th to endDay
8%15%37%32%6%
177
March1st to 15thDay
11%15%32%24%14%1
270
16th to endDay
11%15%25%30%13%3
288
April1st to 15thDay
13%21%23%23%13%4
240
16th to endDay
416%22%25%19%12%
210
May1st to 15thDay
6%14%23%31%17%7%
228
16th to endDay
10%13%9%20%27%18%
267
June1st to 15thDay
7%12%5%26%29%19%
255
16th to endDay
5%11%6%26%30%19%
255
July1st to 15thDay
7%9%324%37%17%
245
16th to endDay
6%12%22%40%17%
270
August1st to 15thDay
7%8%322%40%16%
253
16th to endDay
10%7%322%35%20%
268
September1st to 15thDay
12%5%223%36%18%
255
16th to endDay
20%6%6%21%31%14%
254
October1st to 15thDay
20%7%14%27%20%9%
255
16th to endDay
11%7%15%25%29%11%
272
November1st to 15thDay
13%13%19%23%25%4
265
16th to endDay
9%10%23%28%21%6%
177
December1st to 15thDay
16%224%38%13%4
90
16th to endDay
15%425%29%22%3
96
January1st to 15thNight
11%26%24%27%9%
720
16th to endNight
12%22%31%27%5%
768
February1st to 15thNight
15%24%22%29%8%
704
16th to endNight
12%22%26%30%8%
631
March1st to 15thNight
10%21%26%29%11%
720
16th to endNight
11%21%21%27%16%1
768
April1st to 15thNight
11%22%19%26%18%1
690
16th to endNight
8%21%20%24%21%2
660
May1st to 15thNight
7%19%14%32%21%4
531
16th to endNight
7%19%8%20%28%15%
515
June1st to 15thNight
7%18%323%34%12%
495
16th to endNight
418%5%23%35%11%
495
July1st to 15thNight
8%13%323%39%12%
465
16th to endNight
6%17%118%45%10%
522
August1st to 15thNight
11%11%118%43%13%
494
16th to endNight
11%9%221%37%17%
678
September1st to 15thNight
9%9%421%41%13%
660
16th to endNight
17%9%6%24%32%9%
657
October1st to 15thNight
15%9%15%26%26%6%
660
16th to endNight
9%13%17%27%26%6%
704
November1st to 15thNight
9%18%19%31%19%2
700
16th to endNight
11%21%18%29%16%3
720
December1st to 15thNight
14%22%19%25%16%2
720
16th to endNight
14%23%21%29%10%
768
Page generated at 2017-04-09 06:54:12. Version ac04

Copyright 2017 A. Danko


Charleston Clear Sky Chart | Charts Home