Greenville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greenville clear sky chart from 2005-11-05 to 2018-03-11.

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
35%
16748
15%
49066
9%
16707
41%
16707
20%
34483

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
18%
975
9%
2716
4%
970
23%
970
11%
2189
January16th to endNight
21%
1040
8%
2912
3%
1040
25%
1040
11%
2365
February1st to 15thNight
18%
767
10%
2404
3%
767
25%
767
10%
1887
February16th to endNight
22%
683
12%
2049
5%
683
29%
683
13%
1567
March1st to 15thNight
29%
764
16%
2259
9%
764
34%
764
20%
1564
March16th to endNight
31%
741
18%
2085
10%
741
38%
741
22%
1442
April1st to 15thNight
32%
539
13%
1797
9%
539
39%
539
18%
1256
April16th to endNight
34%
540
20%
1629
9%
540
44%
540
25%
1053
May1st to 15thNight
35%
540
15%
1620
8%
540
42%
540
22%
1126
May16th to endNight
44%
561
15%
1562
10%
561
49%
561
28%
1028
June1st to 15thNight
49%
540
14%
1440
10%
540
53%
540
32%
918
June16th to endNight
52%
540
15%
1440
9%
540
56%
540
34%
918
July1st to 15thNight
65%
510
16%
1360
13%
510
67%
510
44%
769
July16th to endNight
63%
564
20%
1417
16%
531
66%
531
40%
846
August1st to 15thNight
64%
539
21%
1604
16%
536
68%
536
37%
912
August16th to endNight
62%
573
22%
1806
19%
573
66%
573
34%
1047
September1st to 15thNight
59%
618
25%
1878
21%
618
65%
618
36%
1058
September16th to endNight
56%
717
24%
1980
19%
717
59%
717
34%
1219
October1st to 15thNight
45%
720
21%
2025
16%
720
49%
720
28%
1329
October16th to endNight
26%
768
15%
2481
8%
768
35%
768
17%
1745
November1st to 15thNight
34%
760
18%
2471
16%
760
39%
760
20%
1677
November16th to endNight
26%
780
13%
2535
7%
780
33%
780
13%
1885
December1st to 15thNight
17%
929
6%
2684
2%
929
21%
929
9%
2239
December16th to endNight
16%
1040
8%
2912
2%
1040
21%
1040
9%
2444

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
14%8%46%6%35%45%7%33%
49573
Night
14%9%46%5%3445%6%34%
49235
Cloud CoverDay
14%8%46%6%35%45%7%33%
49582
Night
14%9%46%5%3445%6%34%
49240
TransparencyDay
49%6%11%20%10%1
49260
Night
49%5%11%20%11%1
49066
SeeingDay
17%8%27%24%14%6%
6534
Night
18%8%29%30%12%1
16753

By Month

Percentage Cloud Cover NE (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
16%15%6%10%9%6%6%5%5%413%
1552
16th to endDay
13%17%10%11%9%46%345%12%
1664
February1st to 15thDay
13%14%6%11%10%5%5%34418%
1787
16th to endDay
14%12%6%9%9%4445%6%21%
1710
March1st to 15thDay
15%10%47%6%35%35%7%30%
1928
16th to endDay
16%10%47%5%24346%34%
2148
April1st to 15thDay
20%11%35%5%3345%5%31%
2151
16th to endDay
16%7%35%5%35%35%6%37%
2331
May1st to 15thDay
20%6%26%43435%8%34%
2331
16th to endDay
11%5%35%5%36%46%7%40%
2550
June1st to 15thDay
11%6%35%5%36%45%8%40%
2520
16th to endDay
10%5%25%6%35%5%6%8%40%
2520
July1st to 15thDay
6%415%435%5%5%10%46%
2520
16th to endDay
8%424435%5%6%9%43%
2655
August1st to 15thDay
9%5%25%5%37%6%5%9%38%
2346
16th to endDay
12%5%244345%6%8%42%
2394
September1st to 15thDay
11%5%25%5%3446%7%44%
2070
16th to endDay
10%425%5%35%45%9%41%
1980
October1st to 15thDay
17%7%37%6%24335%37%
1935
16th to endDay
21%9%28%7%44436%26%
1740
November1st to 15thDay
15%10%46%5%23446%36%
1717
16th to endDay
19%14%47%5%34347%24%
1755
December1st to 15thDay
15%14%9%12%7%34445%16%
1605
16th to endDay
19%17%9%10%7%3445%413%
1664
January1st to 15thNight
19%13%6%10%7%3345%6%19%
2716
16th to endNight
12%12%9%10%8%45%5%5%7%18%
2912
February1st to 15thNight
12%15%6%9%7%45%5%5%5%22%
2402
16th to endNight
15%12%49%7%35%5%5%6%23%
2049
March1st to 15thNight
15%10%46%5%23347%36%
2246
16th to endNight
16%7%36%5%24347%37%
2085
April1st to 15thNight
19%9%35%5%35%446%33%
1797
16th to endNight
17%7%2342335%6%41%
1629
May1st to 15thNight
17%436%5%445%5%5%36%
1620
16th to endNight
11%6%35%5%25%35%9%41%
1560
June1st to 15thNight
10%425%5%2446%7%46%
1440
16th to endNight
8%325%6%246%5%9%44%
1440
July1st to 15thNight
6%31332446%9%54%
1440
16th to endNight
6%214425%46%8%52%
1513
August1st to 15thNight
5%3244245%6%8%51%
1614
16th to endNight
10%414433447%52%
1806
September1st to 15thNight
10%31332336%6%53%
1878
16th to endNight
8%6%2441445%6%50%
1980
October1st to 15thNight
16%7%25%423446%43%
2025
16th to endNight
20%8%36%5%33446%33%
2481
November1st to 15thNight
15%9%26%5%3446%6%35%
2471
16th to endNight
18%12%36%6%35%45%7%25%
2535
December1st to 15thNight
19%14%5%9%7%45%445%16%
2684
16th to endNight
20%16%7%8%7%34445%15%
2912

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
16%15%6%10%9%6%6%35%414%
1552
16th to endDay
13%17%10%11%9%45%445%13%
1664
February1st to 15thDay
13%15%6%12%11%45%34418%
1787
16th to endDay
15%12%6%9%8%445%5%6%21%
1710
March1st to 15thDay
15%10%47%5%35%45%7%30%
1938
16th to endDay
16%10%5%7%5%24246%34%
2147
April1st to 15thDay
20%11%36%42445%5%30%
2151
16th to endDay
16%7%35%5%35%35%7%37%
2331
May1st to 15thDay
20%7%26%434448%34%
2331
16th to endDay
11%5%35%5%35%45%8%40%
2550
June1st to 15thDay
11%6%25%436%45%8%40%
2520
16th to endDay
10%5%25%5%35%5%6%7%40%
2520
July1st to 15thDay
6%424435%5%5%10%45%
2520
16th to endDay
8%4245%26%5%6%9%43%
2655
August1st to 15thDay
9%5%25%5%46%6%6%9%39%
2346
16th to endDay
12%5%25%5%2446%8%42%
2394
September1st to 15thDay
11%5%245%2445%7%44%
2070
16th to endDay
10%425%5%35%45%8%42%
1980
October1st to 15thDay
17%7%36%6%25%345%37%
1935
16th to endDay
21%10%36%7%35%336%27%
1740
November1st to 15thDay
15%9%45%5%2435%6%36%
1717
16th to endDay
18%14%5%6%5%35%35%6%24%
1755
December1st to 15thDay
15%14%9%12%7%4444417%
1605
16th to endDay
19%16%10%9%7%3445%414%
1664
January1st to 15thNight
19%13%6%9%7%24446%20%
2716
16th to endNight
12%12%9%10%8%45%5%5%7%19%
2912
February1st to 15thNight
12%14%7%8%7%46%45%5%23%
2395
16th to endNight
15%12%410%7%35%5%46%23%
2049
March1st to 15thNight
15%10%36%5%23347%36%
2259
16th to endNight
16%7%36%5%24347%37%
2085
April1st to 15thNight
19%9%35%4345%46%33%
1797
16th to endNight
17%7%23424347%41%
1629
May1st to 15thNight
17%5%36%5%45%446%36%
1619
16th to endNight
11%6%25%6%2445%8%41%
1560
June1st to 15thNight
10%5%25%5%245%5%7%45%
1440
16th to endNight
8%4246%25%5%6%9%44%
1440
July1st to 15thNight
6%32331445%8%55%
1440
16th to endNight
6%31342446%8%52%
1513
August1st to 15thNight
6%3244245%6%8%51%
1614
16th to endNight
10%414323447%52%
1806
September1st to 15thNight
11%31332345%6%53%
1878
16th to endNight
8%6%2442345%6%50%
1980
October1st to 15thNight
16%6%24423437%43%
2025
16th to endNight
20%8%36%5%24436%33%
2481
November1st to 15thNight
14%9%25%5%3446%6%35%
2471
16th to endNight
18%12%36%6%35%45%6%26%
2535
December1st to 15thNight
19%15%5%9%8%45%446%17%
2684
16th to endNight
20%16%7%8%6%34445%16%
2912

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
72%5%10%9%2
1553
16th to endDay
74%48%8%3
1664
February1st to 15thDay
68%6%7%13%4
1789
16th to endDay
62%6%9%14%6%
1710
March1st to 15thDay
53%5%11%20%8%
1938
16th to endDay
51%412%22%7%1
2148
April1st to 15thDay
54%48%19%11%
2151
16th to endDay
46%5%12%19%12%3
2331
May1st to 15thDay
48%5%12%21%10%1
2331
16th to endDay
40%7%11%27%12%
2554
June1st to 15thDay
40%6%13%23%15%
2520
16th to endDay
39%8%13%21%17%1
2520
July1st to 15thDay
32%6%13%26%18%2
2371
16th to endDay
35%7%12%26%16%2
2488
August1st to 15thDay
39%8%10%26%12%2
2332
16th to endDay
37%6%11%26%15%2
2394
September1st to 15thDay
37%6%11%28%14%1
2070
16th to endDay
37%6%13%26%15%
1980
October1st to 15thDay
49%5%9%21%12%1
1935
16th to endDay
58%5%14%16%5%
1740
November1st to 15thDay
47%5%12%23%10%
1717
16th to endDay
60%5%13%14%5%
1755
December1st to 15thDay
69%5%10%12%2
1605
16th to endDay
71%6%9%10%2
1664
January1st to 15thNight
64%410%13%5%
2716
16th to endNight
63%7%13%10%4
2912
February1st to 15thNight
62%6%9%15%5%
2404
16th to endNight
59%5%10%16%7%
2049
March1st to 15thNight
48%5%11%21%11%1
2259
16th to endNight
47%412%22%10%2
2085
April1st to 15thNight
50%5%9%18%15%
1797
16th to endNight
43%312%21%15%3
1629
May1st to 15thNight
47%5%10%20%12%2
1620
16th to endNight
41%5%11%23%16%1
1562
June1st to 15thNight
36%5%11%27%15%1
1440
16th to endNight
34%6%15%25%16%
1440
July1st to 15thNight
25%5%13%30%21%3
1360
16th to endNight
28%6%15%26%19%2
1417
August1st to 15thNight
29%6%12%32%18%1
1604
16th to endNight
31%6%10%28%20%2
1806
September1st to 15thNight
29%5%12%31%18%1
1878
16th to endNight
33%6%12%31%15%
1980
October1st to 15thNight
41%410%25%15%1
2025
16th to endNight
52%413%21%7%
2481
November1st to 15thNight
47%5%11%22%11%1
2471
16th to endNight
57%6%13%18%4
2535
December1st to 15thNight
68%6%10%9%4
2684
16th to endNight
70%5%10%11%2
2912

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
20%13%39%20%5%
135
16th to endDay
29%13%36%12%7%
144
February1st to 15thDay
22%23%43%8%1
135
16th to endDay
21%19%35%20%1
120
March1st to 15thDay
33%12%29%15%9%
154
16th to endDay
26%5%28%27%9%3
288
April1st to 15thDay
27%8%32%21%8%2
270
16th to endDay
20%11%28%21%11%5%
270
May1st to 15thDay
25%10%25%24%8%6%
288
16th to endDay
13%10%30%25%15%5%
450
June1st to 15thDay
12%6%33%29%12%5%
495
16th to endDay
12%8%34%26%13%5%
495
July1st to 15thDay
7%6%22%31%20%11%
475
16th to endDay
9%426%29%20%9%
515
August1st to 15thDay
8%317%27%25%18%
319
16th to endDay
15%417%24%23%15%
332
September1st to 15thDay
10%315%31%23%15%
315
16th to endDay
13%415%27%28%11%
314
October1st to 15thDay
22%6%22%27%16%3
315
16th to endDay
26%7%38%23%3
156
November1st to 15thDay
22%12%33%20%9%1
135
16th to endDay
27%18%35%14%3
135
December1st to 15thDay
22%23%35%14%4
135
16th to endDay
26%28%31%11%2
144
January1st to 15thNight
25%13%32%21%7%
975
16th to endNight
18%10%33%30%5%
1040
February1st to 15thNight
19%13%37%25%4
770
16th to endNight
22%12%32%27%5%
683
March1st to 15thNight
19%10%34%28%7%
764
16th to endNight
19%8%33%28%7%1
741
April1st to 15thNight
20%10%32%28%5%
539
16th to endNight
21%8%33%27%7%1
540
May1st to 15thNight
20%5%33%30%9%1
540
16th to endNight
13%6%28%32%17%1
563
June1st to 15thNight
10%5%28%36%17%
540
16th to endNight
10%326%38%19%1
540
July1st to 15thNight
9%117%45%23%3
510
16th to endNight
6%121%40%26%2
564
August1st to 15thNight
7%118%44%25%2
539
16th to endNight
10%216%36%28%4
573
September1st to 15thNight
12%319%34%24%5%
618
16th to endNight
11%6%19%33%24%5%
717
October1st to 15thNight
19%5%23%35%14%1
720
16th to endNight
26%10%31%22%8%
768
November1st to 15thNight
21%9%30%28%10%
760
16th to endNight
24%12%31%25%6%
780
December1st to 15thNight
25%11%34%23%4
929
16th to endNight
26%11%35%22%4
1040
Page generated at 2018-03-12 13:28:08. Version ac04

Copyright 2018 A. Danko


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