Indiana Dunes State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Indiana Dunes State Park clear sky chart from 2005-11-05 to 2017-08-12.

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
34%
15827
15%
46460
10%
15785
39%
15785
20%
32768

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
14%
900
9%
2506
3%
895
19%
895
11%
2015
January16th to endNight
16%
960
9%
2688
3%
960
21%
960
12%
2176
February1st to 15thNight
19%
749
10%
2163
3%
749
26%
749
14%
1660
February16th to endNight
20%
631
16%
1893
6%
631
30%
631
13%
1441
March1st to 15thNight
24%
720
12%
2160
7%
720
28%
720
16%
1587
March16th to endNight
28%
669
15%
2028
9%
669
35%
669
19%
1449
April1st to 15thNight
30%
539
14%
1797
10%
539
37%
539
17%
1249
April16th to endNight
33%
540
19%
1703
11%
540
41%
540
21%
1135
May1st to 15thNight
37%
540
15%
1620
9%
540
42%
540
21%
1125
May16th to endNight
51%
562
16%
1528
10%
561
55%
561
30%
994
June1st to 15thNight
53%
540
16%
1440
10%
540
56%
540
36%
888
June16th to endNight
49%
540
15%
1440
9%
540
53%
540
31%
945
July1st to 15thNight
64%
510
17%
1360
13%
510
66%
510
39%
820
July16th to endNight
67%
564
21%
1417
16%
531
69%
531
40%
846
August1st to 15thNight
71%
527
22%
1540
19%
524
73%
524
39%
865
August16th to endNight
64%
525
19%
1750
18%
525
68%
525
31%
1001
September1st to 15thNight
60%
525
26%
1680
25%
525
64%
525
31%
988
September16th to endNight
56%
657
25%
1815
18%
657
60%
657
33%
1124
October1st to 15thNight
46%
660
25%
1854
17%
660
52%
660
29%
1187
October16th to endNight
22%
704
15%
2269
9%
704
30%
704
16%
1576
November1st to 15thNight
27%
700
19%
2276
14%
700
35%
700
19%
1531
November16th to endNight
20%
720
14%
2340
9%
720
26%
720
12%
1755
December1st to 15thNight
13%
885
7%
2505
2%
885
17%
885
9%
2082
December16th to endNight
12%
960
7%
2688
2%
960
16%
960
7%
2329

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
13%8%36%5%3445%7%36%
47520
Night
15%9%46%5%34446%34%
46628
Cloud CoverDay
13%8%36%5%3445%7%35%
47529
Night
15%9%46%5%34446%34%
46633
TransparencyDay
47%5%12%20%11%1
47206
Night
49%6%11%19%11%1
46460
SeeingDay
16%8%28%26%14%4
5804
Night
19%11%28%26%12%1
15831

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%16%7%11%8%4444416%
1432
16th to endDay
12%16%9%11%7%6%5%43417%
1536
February1st to 15thDay
14%15%6%10%7%3444422%
1698
16th to endDay
13%12%6%10%7%25%34427%
1580
March1st to 15thDay
16%9%49%6%235%5%6%28%
1790
16th to endDay
16%9%36%5%35%346%34%
2205
April1st to 15thDay
17%8%46%42445%6%35%
2151
16th to endDay
16%8%344345%5%6%37%
2256
May1st to 15thDay
17%7%26%5%24447%34%
2331
16th to endDay
11%6%25%5%35%45%7%41%
2584
June1st to 15thDay
10%5%25%5%345%47%46%
2520
16th to endDay
8%5%145%35%6%6%10%41%
2520
July1st to 15thDay
6%425%4345%6%8%47%
2520
16th to endDay
5%3235%35%6%6%10%46%
2655
August1st to 15thDay
6%424445%47%9%46%
2322
16th to endDay
9%425%425%46%9%45%
2100
September1st to 15thDay
13%4244245%47%45%
1938
16th to endDay
10%5%35%43445%9%41%
1815
October1st to 15thDay
15%6%35%5%24446%41%
1774
16th to endDay
20%9%36%5%3445%6%31%
1603
November1st to 15thDay
17%8%445%4335%6%37%
1582
16th to endDay
18%14%5%9%5%3434426%
1620
December1st to 15thDay
18%16%7%11%8%4433317%
1452
16th to endDay
21%19%6%8%6%25%35%417%
1536
January1st to 15thNight
19%14%6%9%5%3444421%
2506
16th to endNight
15%13%8%10%6%46%445%20%
2688
February1st to 15thNight
17%11%6%8%6%35%435%27%
2161
16th to endNight
17%12%6%8%6%3444427%
1893
March1st to 15thNight
17%11%5%6%5%34445%31%
2147
16th to endNight
16%9%47%5%34447%32%
2028
April1st to 15thNight
17%9%5%5%5%34446%34%
1797
16th to endNight
17%7%25%5%34335%39%
1703
May1st to 15thNight
19%7%25%5%345%47%35%
1620
16th to endNight
12%424425%5%5%8%43%
1526
June1st to 15thNight
9%5%25%5%2346%8%47%
1440
16th to endNight
7%5%35%5%35%6%5%9%41%
1440
July1st to 15thNight
6%2145%25%5%6%7%51%
1440
16th to endNight
6%3134445%6%10%48%
1513
August1st to 15thNight
5%32343446%10%50%
1549
16th to endNight
10%41442445%6%50%
1750
September1st to 15thNight
14%423423246%50%
1680
16th to endNight
10%5%24424448%46%
1815
October1st to 15thNight
14%4245%24346%46%
1854
16th to endNight
24%9%35%323345%34%
2269
November1st to 15thNight
16%11%45%42334437%
2276
16th to endNight
19%12%410%6%24345%26%
2340
December1st to 15thNight
21%15%8%10%7%3333418%
2505
16th to endNight
22%17%7%10%8%4423314%
2688

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%16%7%10%8%44445%16%
1432
16th to endDay
13%17%8%11%8%5%6%43417%
1536
February1st to 15thDay
13%16%7%10%7%345%45%22%
1698
16th to endDay
13%13%5%11%7%34345%26%
1580
March1st to 15thDay
17%11%49%6%2445%6%27%
1800
16th to endDay
16%9%36%6%34446%33%
2204
April1st to 15thDay
17%9%46%423447%34%
2151
16th to endDay
16%9%244345%47%36%
2256
May1st to 15thDay
17%8%35%5%2445%7%34%
2331
16th to endDay
11%6%35%5%35%5%5%7%40%
2584
June1st to 15thDay
9%5%25%6%3445%7%45%
2520
16th to endDay
8%5%146%36%5%7%9%40%
2520
July1st to 15thDay
6%425%4345%6%9%46%
2520
16th to endDay
5%3245%35%6%6%10%44%
2655
August1st to 15thDay
6%4245%35%46%9%46%
2322
16th to endDay
9%5%25%5%345%6%8%44%
2100
September1st to 15thDay
13%424435%45%7%44%
1938
16th to endDay
9%6%4443446%9%40%
1815
October1st to 15thDay
15%6%35%5%34446%41%
1774
16th to endDay
20%9%47%43445%5%30%
1603
November1st to 15thDay
16%9%3443435%5%37%
1582
16th to endDay
17%13%6%8%6%34345%26%
1620
December1st to 15thDay
17%16%6%13%8%3433417%
1452
16th to endDay
21%19%5%8%6%2444417%
1536
January1st to 15thNight
19%14%6%9%6%3444422%
2506
16th to endNight
14%14%7%9%7%45%446%20%
2688
February1st to 15thNight
17%11%6%7%6%35%5%35%27%
2154
16th to endNight
17%12%6%8%6%33445%27%
1893
March1st to 15thNight
17%11%6%6%5%34445%30%
2160
16th to endNight
16%8%46%5%35%447%33%
2028
April1st to 15thNight
17%8%46%6%34446%34%
1797
16th to endNight
17%7%345%33336%39%
1703
May1st to 15thNight
19%6%35%435%5%47%34%
1619
16th to endNight
12%425%4245%5%8%43%
1526
June1st to 15thNight
9%425%5%2336%9%46%
1440
16th to endNight
7%6%35%5%35%6%5%9%41%
1440
July1st to 15thNight
6%2136%26%5%5%8%51%
1440
16th to endNight
5%3134345%7%10%48%
1513
August1st to 15thNight
5%32442447%10%50%
1549
16th to endNight
9%4245%2445%6%50%
1750
September1st to 15thNight
13%424423247%50%
1680
16th to endNight
9%6%24425%45%7%47%
1815
October1st to 15thNight
14%5%14435%35%5%46%
1854
16th to endNight
23%9%36%423346%34%
2269
November1st to 15thNight
15%11%36%433345%37%
2276
16th to endNight
19%12%49%7%24435%26%
2340
December1st to 15thNight
20%15%6%10%8%2433419%
2505
16th to endNight
22%17%6%10%7%4433414%
2688

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
67%6%10%9%5%
1433
16th to endDay
67%6%9%11%3
1536
February1st to 15thDay
63%5%10%13%6%1
1700
16th to endDay
58%5%12%17%41
1580
March1st to 15thDay
55%6%13%16%7%
1800
16th to endDay
51%414%22%6%
2205
April1st to 15thDay
49%49%22%13%
2151
16th to endDay
47%5%14%17%11%4
2256
May1st to 15thDay
49%6%12%22%8%
2331
16th to endDay
41%6%12%23%14%1
2588
June1st to 15thDay
38%411%24%19%1
2520
16th to endDay
37%6%16%20%17%1
2520
July1st to 15thDay
34%6%13%25%17%2
2371
16th to endDay
32%6%18%24%14%2
2488
August1st to 15thDay
32%6%15%26%16%2
2307
16th to endDay
36%5%13%23%16%3
2100
September1st to 15thDay
36%5%12%24%17%3
1938
16th to endDay
36%6%11%26%17%1
1815
October1st to 15thDay
42%5%11%24%14%1
1774
16th to endDay
52%5%13%19%8%1
1603
November1st to 15thDay
46%5%11%20%14%2
1582
16th to endDay
59%6%10%18%5%
1620
December1st to 15thDay
69%6%8%11%3
1452
16th to endDay
68%7%10%9%4
1536
January1st to 15thNight
61%7%10%13%6%
2506
16th to endNight
61%8%12%12%4
2688
February1st to 15thNight
58%5%11%16%7%1
2163
16th to endNight
56%7%9%18%7%
1893
March1st to 15thNight
55%5%11%17%8%1
2160
16th to endNight
50%5%13%19%8%1
2028
April1st to 15thNight
51%49%19%14%
1797
16th to endNight
47%49%19%15%4
1703
May1st to 15thNight
48%5%10%23%11%
1620
16th to endNight
37%7%14%20%16%2
1528
June1st to 15thNight
33%5%13%26%18%2
1440
16th to endNight
36%8%14%22%16%2
1440
July1st to 15thNight
28%7%13%26%20%2
1360
16th to endNight
27%7%16%26%17%4
1417
August1st to 15thNight
27%6%15%27%20%2
1540
16th to endNight
32%6%11%25%18%5%
1750
September1st to 15thNight
34%5%9%24%20%5%
1680
16th to endNight
34%5%7%27%20%3
1815
October1st to 15thNight
37%6%8%26%20%1
1854
16th to endNight
50%5%11%22%8%1
2269
November1st to 15thNight
47%6%7%20%14%3
2276
16th to endNight
58%5%11%19%5%
2340
December1st to 15thNight
67%6%8%12%4
2505
16th to endNight
73%5%7%9%3
2688

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
25%21%34%14%4
90
16th to endDay
18%14%41%21%21
96
February1st to 15thDay
18%28%37%14%
90
16th to endDay
19%14%37%19%8%
81
March1st to 15thDay
34%20%24%18%2
90
16th to endDay
27%12%31%18%9%
273
April1st to 15thDay
26%12%32%18%7%1
270
16th to endDay
20%12%33%16%12%4
270
May1st to 15thDay
22%12%30%21%10%2
288
16th to endDay
15%9%31%28%10%3
484
June1st to 15thDay
10%6%32%30%15%4
495
16th to endDay
11%5%36%30%11%4
495
July1st to 15thDay
10%230%28%19%7%
475
16th to endDay
8%324%35%19%8%
515
August1st to 15thDay
10%115%34%24%13%
339
16th to endDay
16%216%30%22%10%
268
September1st to 15thDay
13%315%34%25%7%
255
16th to endDay
14%7%13%32%23%8%
254
October1st to 15thDay
15%5%28%28%18%2
214
16th to endDay
23%11%46%15%2
96
November1st to 15thDay
7%13%26%33%16%2
90
16th to endDay
30%17%40%11%1
90
December1st to 15thDay
26%23%30%16%3
90
16th to endDay
30%30%36%12
96
January1st to 15thNight
24%20%35%15%3
900
16th to endNight
21%18%35%22%2
960
February1st to 15thNight
22%14%37%21%3
752
16th to endNight
23%14%35%20%5%
631
March1st to 15thNight
23%12%34%21%6%
720
16th to endNight
20%10%33%26%7%
669
April1st to 15thNight
21%13%30%26%6%
539
16th to endNight
21%8%31%26%9%2
540
May1st to 15thNight
22%5%28%28%13%
540
16th to endNight
13%324%38%18%1
563
June1st to 15thNight
11%223%42%19%
540
16th to endNight
9%427%35%21%1
540
July1st to 15thNight
8%18%42%26%2
510
16th to endNight
7%215%40%29%4
564
August1st to 15thNight
6%111%44%29%5%
527
16th to endNight
10%214%38%27%6%
525
September1st to 15thNight
14%5%13%34%26%4
525
16th to endNight
11%5%20%30%27%4
657
October1st to 15thNight
16%7%25%29%19%1
660
16th to endNight
25%18%29%19%6%
704
November1st to 15thNight
22%13%33%18%11%
700
16th to endNight
24%21%28%19%5%
720
December1st to 15thNight
29%18%33%16%2
885
16th to endNight
30%16%33%18%2
960
Page generated at 2017-08-13 13:16:37. Version ac04

Copyright 2017 A. Danko


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