Givhans Ferry State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Givhans Ferry State Park clear sky chart from 2005-11-06 to 2024-01-13.

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%
24482
21%
74365
14%
24424
54%
24424
26%
46761

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
29%
760
23%
2459
10%
757
44%
757
22%
1505
January11th to 20thNight
34%
732
25%
2378
14%
732
50%
732
23%
1458
January21st to endNight
24%
792
24%
2574
11%
792
41%
792
23%
1608
February1st to 10thNight
31%
720
20%
2340
10%
720
44%
720
22%
1469
February11th to 20thNight
26%
703
20%
2103
9%
699
40%
699
22%
1357
February21st to endNight
25%
592
24%
1664
10%
592
38%
592
25%
1078
March1st to 10thNight
32%
720
28%
1980
16%
720
43%
720
32%
1234
March11th to 20thNight
31%
720
22%
1980
11%
720
42%
720
27%
1267
March21st to endNight
33%
792
21%
2178
9%
792
43%
792
28%
1371
April1st to 10thNight
34%
720
24%
1979
13%
720
43%
720
32%
1202
April11th to 20thNight
38%
711
26%
1775
13%
711
45%
711
36%
1110
April21st to endNight
43%
720
28%
1800
14%
720
49%
720
40%
1080
May1st to 10thNight
49%
546
23%
1626
13%
546
55%
546
36%
911
May11th to 20thNight
53%
531
17%
1593
10%
531
57%
531
30%
976
May21st to endNight
61%
582
19%
1745
13%
582
65%
582
29%
1097
June1st to 10thNight
60%
540
14%
1620
11%
540
61%
540
25%
1071
June11th to 20thNight
67%
540
13%
1620
10%
540
69%
540
28%
1042
June21st to endNight
63%
540
12%
1620
8%
540
66%
540
24%
1077
July1st to 10thNight
68%
525
12%
1575
10%
525
69%
525
25%
1050
July11th to 20thNight
68%
522
10%
1566
8%
522
68%
522
23%
1064
July21st to endNight
70%
591
12%
1672
9%
558
73%
558
25%
1118
August1st to 10thNight
72%
537
12%
1600
11%
534
72%
534
22%
1102
August11th to 20thNight
66%
552
11%
1616
9%
552
67%
552
19%
1174
August21st to endNight
61%
792
14%
1980
11%
792
62%
792
22%
1486
September1st to 10thNight
66%
720
17%
1934
14%
720
67%
720
28%
1301
September11th to 20thNight
60%
720
17%
1980
16%
720
61%
720
26%
1344
September21st to endNight
55%
720
17%
1980
15%
720
58%
720
25%
1349
October1st to 10thNight
54%
720
26%
2107
24%
720
59%
720
32%
1297
October11th to 20thNight
53%
720
30%
2160
26%
720
63%
720
38%
1197
October21st to endNight
49%
792
31%
2376
24%
792
60%
792
35%
1352
November1st to 10thNight
50%
740
29%
2221
21%
740
61%
740
35%
1265
November11th to 20thNight
40%
760
28%
2284
18%
760
53%
760
30%
1377
November21st to endNight
41%
760
25%
2470
17%
760
52%
760
28%
1457
December1st to 10thNight
37%
760
23%
2470
15%
760
49%
760
22%
1587
December11th to 20thNight
38%
759
25%
2932
17%
758
48%
758
21%
1724
December21st to endNight
31%
831
16%
4408
14%
817
43%
817
13%
2604

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
12%6%36%6%45%5%6%8%40%
74945
Night
12%5%25%5%35%5%6%8%44%
74806
TransparencyDay
40%8%12%18%16%5%
74668
Night
37%8%13%19%17%6%
74602
SeeingDay
14%10%25%25%18%8%
14346
Night
13%8%25%31%19%3
24490

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
13%5%35%5%3446%6%45%
1706
11th to 20thDay
13%6%36%5%2445%7%46%
1638
21st to endDay
17%6%35%5%23436%45%
1782
February1st to 10thDay
17%6%34435%5%6%7%40%
1620
11th to 20thDay
18%6%24423347%46%
1739
21st to endDay
16%7%26%5%24445%45%
1592
March1st to 10thDay
14%6%23334446%52%
1980
11th to 20thDay
14%5%36%5%3445%8%45%
1980
21st to endDay
13%5%36%5%4445%7%44%
2178
April1st to 10thDay
9%425%435%5%5%7%51%
1980
11th to 20thDay
11%425%6%35%447%47%
2134
21st to endDay
8%423435%5%6%8%52%
2168
May1st to 10thDay
8%435%5%45%6%6%8%47%
2340
11th to 20thDay
10%5%37%7%36%6%7%8%39%
2301
21st to endDay
11%5%37%7%5%7%7%7%8%33%
2531
June1st to 10thDay
12%6%36%7%6%8%6%8%8%29%
2340
11th to 20thDay
9%436%6%48%7%9%10%34%
2340
21st to endDay
7%5%37%8%5%7%8%8%11%31%
2340
July1st to 10thDay
10%6%37%8%5%8%8%8%10%28%
2340
11th to 20thDay
9%6%38%7%6%8%9%8%11%27%
2340
21st to endDay
8%6%37%7%6%8%8%9%10%27%
2547
August1st to 10thDay
11%5%37%8%5%8%7%8%11%26%
2327
11th to 20thDay
10%6%47%10%6%8%8%7%10%24%
2267
21st to endDay
13%8%48%9%5%7%5%7%9%24%
2376
September1st to 10thDay
9%6%37%7%46%7%8%8%34%
2021
11th to 20thDay
14%6%36%6%46%7%6%7%34%
1980
21st to endDay
16%7%36%6%35%5%6%7%37%
1980
October1st to 10thDay
13%5%25%5%45%5%5%7%45%
1851
11th to 20thDay
10%4246%24446%54%
1800
21st to endDay
10%42443345%455%
1980
November1st to 10thDay
12%41442345%6%54%
1857
11th to 20thDay
14%8%25%423346%49%
1893
21st to endDay
14%6%24324447%50%
1710
December1st to 10thDay
15%5%36%6%345%5%6%43%
1710
11th to 20thDay
16%5%24313346%52%
2153
21st to endDay
19%8%24433345%44%
3124
January1st to 10thNight
12%7%35%5%35%45%6%47%
2459
11th to 20thNight
12%7%25%5%35%5%5%6%45%
2378
21st to endNight
16%6%36%5%2345%5%45%
2574
February1st to 10thNight
16%6%245%35%45%6%43%
2340
11th to 20thNight
17%6%24435%447%44%
2103
21st to endNight
13%7%35%43445%6%44%
1664
March1st to 10thNight
10%5%345%3446%7%48%
1980
11th to 20thNight
11%6%35%5%3446%8%45%
1980
21st to endNight
10%6%245%35%45%9%46%
2178
April1st to 10thNight
10%43443445%7%51%
1979
11th to 20thNight
12%42442446%8%50%
1775
21st to endNight
8%41443446%7%55%
1800
May1st to 10thNight
7%415%4345%6%8%53%
1626
11th to 20thNight
9%6%245%25%5%7%10%46%
1592
21st to endNight
9%5%25%6%35%5%7%8%45%
1744
June1st to 10thNight
10%6%37%5%35%6%9%11%35%
1620
11th to 20thNight
8%5%246%46%7%8%12%39%
1620
21st to endNight
6%435%7%46%8%10%13%35%
1620
July1st to 10thNight
8%5%36%7%35%7%9%12%36%
1620
11th to 20thNight
7%446%7%46%7%8%12%35%
1620
21st to endNight
6%436%6%47%8%9%12%35%
1771
August1st to 10thNight
6%6%26%6%47%7%10%14%32%
1611
11th to 20thNight
8%5%27%8%5%8%7%9%11%31%
1616
21st to endNight
11%6%37%7%5%6%6%6%10%33%
1980
September1st to 10thNight
8%426%7%36%6%7%11%40%
1934
11th to 20thNight
10%6%36%7%35%6%6%7%40%
1980
21st to endNight
16%6%26%5%345%7%8%38%
1980
October1st to 10thNight
14%5%25%333346%50%
2107
11th to 20thNight
12%41332345%6%56%
2160
21st to endNight
10%6%2442435%6%55%
2376
November1st to 10thNight
11%5%23424346%56%
2221
11th to 20thNight
15%6%24323336%51%
2284
21st to endNight
12%5%25%435%45%7%47%
2470
December1st to 10thNight
15%6%25%4345%5%7%42%
2470
11th to 20thNight
18%5%3442334449%
3042
21st to endNight
19%6%35%5%2445%7%40%
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
39%6%9%19%21%6%
1707
11th to 20thDay
39%5%9%18%23%7%
1638
21st to endDay
42%36%19%23%8%
1782
February1st to 10thDay
41%7%8%19%19%6%
1620
11th to 20thDay
40%5%7%17%23%8%
1749
21st to endDay
41%5%9%18%17%10%
1592
March1st to 10thDay
34%5%8%20%19%14%
1980
11th to 20thDay
39%6%13%18%16%8%
1980
21st to endDay
40%6%10%18%20%6%
2178
April1st to 10thDay
32%6%12%20%22%9%
1980
11th to 20thDay
36%5%9%21%18%11%
2134
21st to endDay
28%6%11%28%22%5%
2168
May1st to 10thDay
34%7%11%22%20%6%
2340
11th to 20thDay
41%9%15%17%17%2
2305
21st to endDay
44%10%14%19%12%1
2531
June1st to 10thDay
48%11%15%15%10%
2340
11th to 20thDay
39%12%20%21%7%1
2340
21st to endDay
41%13%20%16%8%1
2340
July1st to 10thDay
45%13%17%16%7%2
2275
11th to 20thDay
46%14%22%13%5%
2271
21st to endDay
44%15%20%17%31
2405
August1st to 10thDay
47%12%20%17%4
2314
11th to 20thDay
51%15%17%15%3
2267
21st to endDay
53%12%14%13%6%1
2376
September1st to 10thDay
44%11%15%13%14%4
2021
11th to 20thDay
46%10%10%17%13%4
1980
21st to endDay
46%7%12%17%15%4
1980
October1st to 10thDay
38%6%10%16%23%7%
1851
11th to 20thDay
31%5%10%20%25%10%
1800
21st to endDay
31%5%7%16%28%13%
1980
November1st to 10thDay
31%5%9%17%25%13%
1857
11th to 20thDay
38%47%16%23%12%
1893
21st to endDay
35%48%23%21%9%
1710
December1st to 10thDay
41%7%11%18%16%7%
1710
11th to 20thDay
34%5%7%20%26%8%
2150
21st to endDay
43%47%18%24%4
3124
January1st to 10thNight
39%5%8%19%21%8%
2459
11th to 20thNight
39%5%8%18%23%8%
2378
21st to endNight
41%5%6%16%23%9%
2574
February1st to 10thNight
42%5%9%17%19%9%
2340
11th to 20thNight
41%6%9%15%20%10%
2104
21st to endNight
40%6%11%18%14%11%
1664
March1st to 10thNight
34%7%9%18%20%12%
1980
11th to 20thNight
37%7%14%18%16%8%
1980
21st to endNight
36%6%14%20%17%7%
2178
April1st to 10thNight
33%6%12%19%21%9%
1979
11th to 20thNight
32%6%10%22%20%11%
1775
21st to endNight
28%6%12%27%22%5%
1800
May1st to 10thNight
28%6%16%23%21%6%
1626
11th to 20thNight
33%10%19%21%17%1
1593
21st to endNight
34%10%15%26%13%1
1745
June1st to 10thNight
37%12%21%20%9%
1620
11th to 20thNight
34%12%22%24%7%1
1620
21st to endNight
35%15%24%20%5%1
1620
July1st to 10thNight
35%14%24%19%6%2
1575
11th to 20thNight
38%14%25%15%7%1
1566
21st to endNight
34%16%25%21%41
1672
August1st to 10thNight
36%17%25%19%4
1600
11th to 20thNight
43%16%20%18%4
1616
21st to endNight
44%14%17%19%5%1
1980
September1st to 10thNight
36%12%19%18%11%4
1934
11th to 20thNight
38%11%15%19%14%3
1980
21st to endNight
42%9%14%18%15%3
1980
October1st to 10thNight
36%5%10%21%23%6%
2107
11th to 20thNight
28%6%10%22%24%10%
2160
21st to endNight
30%5%8%19%25%13%
2376
November1st to 10thNight
31%48%17%25%14%
2221
11th to 20thNight
36%5%7%17%23%13%
2284
21st to endNight
37%49%17%23%10%
2470
December1st to 10thNight
41%7%13%16%17%7%
2470
11th to 20thNight
38%5%7%16%27%7%
3044
21st to endNight
44%5%7%18%22%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
17%24%45%11%21
270
11th to 20thDay
14%19%41%18%8%1
246
21st to endDay
27%25%37%9%2
264
February1st to 10thDay
23%23%37%15%3
240
11th to 20thDay
26%27%37%9%2
240
21st to endDay
18%19%44%15%3
310
March1st to 10thDay
19%17%34%23%7%
420
11th to 20thDay
14%25%35%17%7%1
420
21st to endDay
16%18%38%18%9%1
462
April1st to 10thDay
17%19%32%20%10%1
420
11th to 20thDay
12%17%31%19%16%5%
412
21st to endDay
9%12%32%24%15%8%
420
May1st to 10thDay
8%18%34%21%13%6%
423
11th to 20thDay
12%6%26%27%21%8%
447
21st to endDay
11%321%32%20%14%
485
June1st to 10thDay
12%5%20%30%22%10%
450
11th to 20thDay
12%5%16%26%26%15%
450
21st to endDay
8%416%32%27%12%
450
July1st to 10thDay
8%29%29%33%18%
445
11th to 20thDay
7%38%30%34%18%
444
21st to endDay
5%313%35%31%12%
488
August1st to 10thDay
12%312%26%28%18%
446
11th to 20thDay
10%28%28%35%17%
439
21st to endDay
13%411%27%28%16%
495
September1st to 10thDay
10%412%30%30%15%
450
11th to 20thDay
16%315%35%22%8%
450
21st to endDay
17%120%28%24%10%
450
October1st to 10thDay
15%428%28%17%8%
450
11th to 20thDay
10%7%24%31%20%8%
450
21st to endDay
14%8%26%29%18%4
495
November1st to 10thDay
17%10%30%24%17%3
455
11th to 20thDay
19%13%35%21%10%2
453
21st to endDay
13%16%36%27%7%
270
December1st to 10thDay
17%17%37%23%5%
270
11th to 20thDay
19%18%39%16%6%1
270
21st to endDay
27%18%29%18%8%1
297
January1st to 10thNight
15%15%35%27%7%
760
11th to 20thNight
17%14%31%29%9%
732
21st to endNight
19%14%39%24%3
792
February1st to 10thNight
18%15%32%29%6%
720
11th to 20thNight
19%17%35%26%4
703
21st to endNight
18%13%39%24%5%
592
March1st to 10thNight
13%13%37%31%6%
720
11th to 20thNight
15%13%38%28%8%
720
21st to endNight
13%15%34%30%8%
792
April1st to 10thNight
13%15%35%29%8%1
720
11th to 20thNight
14%10%34%28%14%2
711
21st to endNight
11%11%31%34%13%
720
May1st to 10thNight
6%9%31%38%17%
546
11th to 20thNight
10%425%37%21%2
531
21st to endNight
10%215%38%32%4
584
June1st to 10thNight
12%315%43%24%4
540
11th to 20thNight
9%411%37%30%9%
540
21st to endNight
6%217%35%34%6%
540
July1st to 10thNight
8%210%40%35%6%
525
11th to 20thNight
9%17%33%43%8%
522
21st to endNight
5%37%39%40%7%
591
August1st to 10thNight
7%36%32%42%9%
537
11th to 20thNight
9%37%31%41%10%
552
21st to endNight
12%310%30%34%11%
792
September1st to 10thNight
7%212%31%41%7%
720
11th to 20thNight
12%313%35%32%5%
720
21st to endNight
19%314%31%29%5%
720
October1st to 10thNight
16%320%33%22%6%
720
11th to 20thNight
13%5%23%32%24%3
720
21st to endNight
12%7%25%31%23%2
792
November1st to 10thNight
13%9%24%34%17%2
740
11th to 20thNight
17%10%29%30%13%2
760
21st to endNight
13%9%30%29%16%1
760
December1st to 10thNight
18%9%30%31%11%
760
11th to 20thNight
19%10%28%30%11%1
760
21st to endNight
21%13%31%27%9%
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