Dreher Island State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dreher Island 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
45%
24264
22%
74378
14%
24210
54%
24210
26%
46665

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
26%
759
23%
2459
8%
757
44%
757
22%
1517
January11th to 20thNight
30%
732
24%
2378
11%
732
47%
732
22%
1479
January21st to endNight
24%
792
27%
2574
13%
792
43%
792
23%
1551
February1st to 10thNight
30%
720
21%
2300
11%
720
43%
720
23%
1443
February11th to 20thNight
23%
702
22%
2099
8%
700
38%
700
23%
1347
February21st to endNight
24%
592
25%
1740
9%
592
40%
592
24%
1128
March1st to 10thNight
31%
720
27%
1980
13%
720
42%
720
30%
1241
March11th to 20thNight
27%
720
21%
1980
9%
720
38%
720
26%
1290
March21st to endNight
29%
792
22%
2178
7%
792
41%
792
26%
1413
April1st to 10thNight
35%
720
24%
1980
12%
720
46%
720
31%
1190
April11th to 20thNight
41%
711
24%
1819
11%
711
49%
711
35%
1126
April21st to endNight
44%
593
30%
1673
16%
593
54%
593
37%
963
May1st to 10thNight
45%
540
21%
1620
10%
540
53%
540
34%
927
May11th to 20thNight
47%
531
15%
1593
9%
531
50%
531
25%
1049
May21st to endNight
63%
582
20%
1744
15%
582
66%
582
29%
1106
June1st to 10thNight
53%
540
14%
1620
11%
540
55%
540
23%
1111
June11th to 20thNight
63%
540
14%
1620
11%
540
65%
540
28%
1034
June21st to endNight
62%
540
14%
1620
11%
540
64%
540
24%
1089
July1st to 10thNight
67%
525
11%
1575
9%
525
67%
525
23%
1079
July11th to 20thNight
70%
522
10%
1566
9%
522
70%
522
23%
1059
July21st to endNight
64%
591
12%
1672
9%
558
67%
558
24%
1165
August1st to 10thNight
66%
537
11%
1600
11%
534
66%
534
21%
1135
August11th to 20thNight
63%
534
15%
1598
13%
534
63%
534
22%
1119
August21st to endNight
63%
728
14%
1956
10%
728
63%
728
22%
1404
September1st to 10thNight
66%
720
19%
1980
15%
720
68%
720
30%
1282
September11th to 20thNight
59%
720
20%
1980
17%
720
62%
720
27%
1328
September21st to endNight
56%
720
20%
1980
16%
720
60%
720
28%
1319
October1st to 10thNight
55%
720
26%
2059
22%
720
62%
720
34%
1242
October11th to 20thNight
51%
720
30%
2160
25%
720
61%
720
35%
1240
October21st to endNight
51%
792
33%
2376
24%
792
64%
792
36%
1341
November1st to 10thNight
50%
740
29%
2221
22%
740
60%
740
35%
1259
November11th to 20thNight
40%
760
27%
2409
19%
760
53%
760
30%
1393
November21st to endNight
43%
760
26%
2470
19%
760
53%
760
29%
1444
December1st to 10thNight
36%
760
24%
2470
15%
760
48%
760
21%
1589
December11th to 20thNight
39%
759
28%
2916
19%
758
51%
758
24%
1642
December21st to endNight
32%
830
15%
4413
13%
817
43%
817
13%
2621

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%5%25%5%35%5%6%8%43%
74921
Night
13%5%25%5%345%5%8%44%
74830
TransparencyDay
38%8%12%19%18%5%
74644
Night
37%7%11%19%19%7%
74626
SeeingDay
15%10%24%25%19%8%
14142
Night
15%9%24%31%18%2
24275

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
15%5%25%5%34446%47%
1706
11th to 20thDay
16%7%345%34345%44%
1638
21st to endDay
17%6%25%423345%48%
1782
February1st to 10thDay
15%6%35%6%345%5%7%41%
1658
11th to 20thDay
19%5%25%32445%5%45%
1748
21st to endDay
18%7%25%4245%5%5%42%
1514
March1st to 10thDay
13%5%24424435%52%
1980
11th to 20thDay
16%5%35%4345%6%7%42%
1980
21st to endDay
15%6%35%5%35%46%7%42%
2178
April1st to 10thDay
10%424435%5%6%8%50%
1980
11th to 20thDay
10%6%25%435%5%6%8%47%
2088
21st to endDay
9%4244435%6%8%52%
2301
May1st to 10thDay
8%3345%35%5%6%8%50%
2340
11th to 20thDay
11%6%26%5%36%7%6%7%41%
2301
21st to endDay
10%6%25%5%46%6%6%10%40%
2531
June1st to 10thDay
10%6%36%7%46%6%7%11%37%
2340
11th to 20thDay
7%325%6%46%6%7%12%42%
2340
21st to endDay
5%425%6%46%7%8%13%40%
2340
July1st to 10thDay
8%5%26%7%5%7%8%9%10%33%
2340
11th to 20thDay
6%6%35%7%48%6%9%12%32%
2340
21st to endDay
6%436%7%5%7%8%8%12%33%
2547
August1st to 10thDay
9%6%26%7%5%6%7%8%11%32%
2327
11th to 20thDay
14%5%26%7%5%6%7%8%10%31%
2303
21st to endDay
13%6%27%6%5%6%6%9%11%30%
2378
September1st to 10thDay
7%5%26%7%35%6%8%9%41%
1980
11th to 20thDay
13%6%25%6%345%6%9%41%
1980
21st to endDay
16%8%25%43445%6%43%
1980
October1st to 10thDay
14%6%24423347%52%
1900
11th to 20thDay
12%424323346%58%
1800
21st to endDay
11%5%24433335%57%
1980
November1st to 10thDay
13%5%24424345%55%
1857
11th to 20thDay
14%5%24423346%54%
1767
21st to endDay
14%5%345%24446%49%
1710
December1st to 10thDay
18%8%35%5%2446%6%38%
1710
11th to 20thDay
17%423333446%51%
2153
21st to endDay
18%7%25%42345%7%43%
3124
January1st to 10thNight
16%6%35%424435%47%
2459
11th to 20thNight
14%6%35%5%34446%45%
2378
21st to endNight
17%7%25%424345%48%
2574
February1st to 10thNight
16%7%245%3445%6%44%
2300
11th to 20thNight
18%6%34424346%45%
2098
21st to endNight
16%5%25%5%2445%7%44%
1740
March1st to 10thNight
13%6%3443445%6%48%
1980
11th to 20thNight
15%5%25%5%3445%6%45%
1980
21st to endNight
12%6%35%5%35%5%5%7%44%
2178
April1st to 10thNight
11%42442445%7%52%
1980
11th to 20thNight
12%424434446%53%
1819
21st to endNight
8%325%42445%7%55%
1673
May1st to 10thNight
8%425%4335%8%10%48%
1620
11th to 20thNight
10%5%35%5%46%6%7%10%39%
1592
21st to endNight
8%5%25%6%447%7%10%42%
1744
June1st to 10thNight
11%5%46%7%46%6%7%10%34%
1620
11th to 20thNight
8%6%246%446%7%11%41%
1620
21st to endNight
6%5%37%5%37%8%8%12%35%
1620
July1st to 10thNight
7%5%46%7%47%8%8%13%33%
1620
11th to 20thNight
7%5%36%5%46%8%8%13%34%
1620
21st to endNight
6%6%26%8%37%7%7%12%34%
1771
August1st to 10thNight
9%5%36%6%47%8%9%12%31%
1611
11th to 20thNight
12%7%36%6%46%5%8%11%32%
1598
21st to endNight
10%6%27%7%5%6%7%7%11%31%
1956
September1st to 10thNight
8%5%35%5%36%6%8%9%42%
1980
11th to 20thNight
12%6%36%6%45%5%6%8%39%
1980
21st to endNight
16%6%25%4245%5%7%43%
1980
October1st to 10thNight
14%6%24423346%52%
2059
11th to 20thNight
14%424423446%54%
2160
21st to endNight
11%424433445%56%
2376
November1st to 10thNight
12%6%24333235%56%
2221
11th to 20thNight
13%6%24423346%53%
2409
21st to endNight
14%5%244245%6%6%48%
2470
December1st to 10thNight
16%6%25%6%345%45%43%
2470
11th to 20thNight
16%6%25%322346%51%
3042
21st to endNight
19%6%25%435%5%46%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
38%6%10%19%22%6%
1707
11th to 20thDay
42%5%8%17%21%7%
1638
21st to endDay
39%46%19%25%7%
1782
February1st to 10thDay
43%410%20%17%6%
1658
11th to 20thDay
41%5%6%19%24%5%
1758
21st to endDay
43%5%9%15%19%8%
1514
March1st to 10thDay
36%47%22%22%10%
1980
11th to 20thDay
41%6%11%18%17%7%
1980
21st to endDay
41%7%10%18%19%4
2178
April1st to 10thDay
32%6%11%19%26%6%
1980
11th to 20thDay
34%7%11%19%20%10%
2088
21st to endDay
29%7%12%26%22%5%
2301
May1st to 10thDay
31%7%16%22%21%4
2340
11th to 20thDay
40%9%16%17%17%1
2305
21st to endDay
38%10%13%23%15%1
2531
June1st to 10thDay
40%11%16%21%10%2
2340
11th to 20thDay
33%11%18%25%12%1
2340
21st to endDay
33%13%18%21%13%2
2340
July1st to 10thDay
39%14%19%16%9%3
2275
11th to 20thDay
39%14%22%17%7%1
2271
21st to endDay
37%14%21%20%7%1
2405
August1st to 10thDay
41%13%18%19%7%1
2314
11th to 20thDay
45%13%16%16%9%1
2303
21st to endDay
44%12%18%16%8%2
2378
September1st to 10thDay
36%11%15%16%18%4
1980
11th to 20thDay
40%8%11%18%20%4
1980
21st to endDay
41%6%9%21%17%7%
1980
October1st to 10thDay
34%5%8%21%24%8%
1900
11th to 20thDay
30%48%25%25%8%
1800
21st to endDay
31%5%6%17%30%12%
1980
November1st to 10thDay
33%46%18%27%12%
1857
11th to 20thDay
33%5%7%20%25%11%
1767
21st to endDay
37%5%8%19%22%9%
1710
December1st to 10thDay
45%6%8%18%16%7%
1710
11th to 20thDay
35%5%7%21%22%11%
2150
21st to endDay
41%48%21%23%3
3124
January1st to 10thNight
40%48%18%24%6%
2459
11th to 20thNight
41%5%8%18%21%8%
2378
21st to endNight
39%35%20%24%9%
2574
February1st to 10thNight
41%48%19%20%8%
2300
11th to 20thNight
41%47%19%21%8%
2099
21st to endNight
40%6%9%17%18%10%
1740
March1st to 10thNight
37%5%8%16%23%12%
1980
11th to 20thNight
39%6%12%16%21%7%
1980
21st to endNight
38%7%11%20%19%6%
2178
April1st to 10thNight
32%5%11%19%24%8%
1980
11th to 20thNight
33%5%9%20%22%11%
1819
21st to endNight
28%6%10%26%24%5%
1673
May1st to 10thNight
30%7%16%24%19%5%
1620
11th to 20thNight
38%10%16%18%16%1
1593
21st to endNight
33%11%12%25%15%3
1745
June1st to 10thNight
42%10%16%19%11%1
1620
11th to 20thNight
35%10%18%23%11%2
1620
21st to endNight
36%15%18%19%11%2
1620
July1st to 10thNight
38%15%22%14%10%3
1575
11th to 20thNight
37%14%24%16%7%2
1566
21st to endNight
39%14%22%17%8%1
1672
August1st to 10thNight
41%15%21%17%6%1
1600
11th to 20thNight
43%12%20%17%8%1
1598
21st to endNight
44%12%17%17%9%2
1956
September1st to 10thNight
35%10%16%19%15%5%
1980
11th to 20thNight
40%8%13%18%17%4
1980
21st to endNight
40%8%12%18%18%5%
1980
October1st to 10thNight
34%5%10%17%28%6%
2059
11th to 20thNight
31%49%23%22%10%
2160
21st to endNight
30%5%6%20%27%13%
2376
November1st to 10thNight
32%48%16%27%14%
2221
11th to 20thNight
34%47%17%24%14%
2409
21st to endNight
35%5%8%18%24%9%
2470
December1st to 10thNight
43%6%8%18%19%7%
2470
11th to 20thNight
36%47%18%26%9%
3044
21st to endNight
44%5%7%20%20%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
19%23%42%12%3
270
11th to 20thDay
20%26%33%19%3
246
21st to endDay
22%27%37%13%2
264
February1st to 10thDay
18%27%37%15%4
240
11th to 20thDay
33%19%37%11%1
240
21st to endDay
25%21%34%17%3
232
March1st to 10thDay
17%20%35%20%8%
420
11th to 20thDay
20%18%40%16%5%
420
21st to endDay
19%19%35%18%8%
462
April1st to 10thDay
17%16%33%21%12%
420
11th to 20thDay
14%14%32%23%14%3
412
21st to endDay
12%11%32%24%17%5%
420
May1st to 10thDay
9%11%38%25%13%4
423
11th to 20thDay
15%422%31%19%9%
447
21st to endDay
12%5%17%28%26%13%
485
June1st to 10thDay
11%416%32%27%10%
450
11th to 20thDay
9%420%24%28%15%
450
21st to endDay
7%217%34%27%13%
450
July1st to 10thDay
10%38%26%31%22%
445
11th to 20thDay
8%411%26%32%18%
444
21st to endDay
6%111%34%36%12%
488
August1st to 10thDay
12%412%27%30%15%
446
11th to 20thDay
14%410%26%29%17%
439
21st to endDay
14%311%28%28%16%
495
September1st to 10thDay
8%411%29%36%13%
450
11th to 20thDay
16%413%27%30%11%
450
21st to endDay
19%318%27%25%8%
450
October1st to 10thDay
16%5%22%29%19%9%
450
11th to 20thDay
13%8%24%28%22%6%
450
21st to endDay
13%9%27%28%18%5%
495
November1st to 10thDay
17%9%27%27%15%6%
455
11th to 20thDay
19%13%35%26%5%2
327
21st to endDay
11%15%37%24%11%1
270
December1st to 10thDay
26%17%34%18%5%
270
11th to 20thDay
22%15%39%17%6%1
270
21st to endDay
27%18%33%15%43
297
January1st to 10thNight
21%18%31%24%6%
760
11th to 20thNight
19%15%33%27%7%
732
21st to endNight
20%17%36%23%4
792
February1st to 10thNight
21%15%31%28%4
720
11th to 20thNight
22%15%37%24%2
703
21st to endNight
18%16%38%25%4
592
March1st to 10thNight
17%12%37%30%5%
720
11th to 20thNight
18%13%39%24%7%
720
21st to endNight
16%14%37%26%7%
792
April1st to 10thNight
14%16%32%29%9%
720
11th to 20thNight
13%12%30%32%13%
711
21st to endNight
10%10%32%36%12%
593
May1st to 10thNight
10%9%31%35%14%
540
11th to 20thNight
11%329%34%19%3
531
21st to endNight
10%216%38%30%4
584
June1st to 10thNight
12%220%37%25%4
540
11th to 20thNight
10%315%34%30%9%
540
21st to endNight
8%315%40%28%6%
540
July1st to 10thNight
8%28%37%37%7%
525
11th to 20thNight
11%26%35%38%8%
522
21st to endNight
7%211%36%39%6%
591
August1st to 10thNight
10%111%33%38%7%
537
11th to 20thNight
14%37%34%37%5%
534
21st to endNight
12%210%30%39%6%
728
September1st to 10thNight
9%211%34%38%5%
720
11th to 20thNight
14%214%28%37%5%
720
21st to endNight
18%214%35%26%4
720
October1st to 10thNight
16%5%18%31%25%4
720
11th to 20thNight
16%7%22%31%22%3
720
21st to endNight
12%8%24%32%21%2
792
November1st to 10thNight
15%7%24%33%19%3
740
11th to 20thNight
15%12%29%30%12%1
760
21st to endNight
14%10%28%32%14%1
760
December1st to 10thNight
18%14%26%32%9%1
760
11th to 20thNight
20%10%26%33%10%1
760
21st to endNight
26%13%25%29%7%
836
Page generated at 2024-01-10 10:16:11. Version ac07

Copyright 2024 Attilla Danko


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