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 2018-02-22.

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%
16640
15%
48873
10%
16598
39%
16598
20%
34469

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%
975
9%
2716
3%
970
20%
970
12%
2176
January16th to endNight
15%
1040
9%
2912
2%
1040
21%
1040
12%
2341
February1st to 15thNight
18%
813
11%
2347
3%
813
25%
813
14%
1810
February16th to endNight
19%
659
16%
1977
6%
659
28%
659
12%
1513
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
29%
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
52%
562
16%
1528
10%
561
56%
561
30%
994
June1st to 15thNight
52%
540
16%
1440
10%
540
56%
540
36%
888
June16th to endNight
48%
540
15%
1440
9%
540
52%
540
31%
945
July1st to 15thNight
63%
510
17%
1360
13%
510
65%
510
39%
820
July16th to endNight
67%
564
21%
1417
16%
531
70%
531
40%
846
August1st to 15thNight
71%
539
21%
1575
19%
536
73%
536
39%
887
August16th to endNight
64%
573
20%
1910
20%
573
69%
573
32%
1093
September1st to 15thNight
59%
573
25%
1833
24%
573
63%
573
31%
1073
September16th to endNight
56%
717
27%
1980
20%
717
60%
717
34%
1210
October1st to 15thNight
45%
720
23%
2023
16%
720
50%
720
29%
1312
October16th to endNight
23%
768
17%
2475
10%
768
32%
768
17%
1704
November1st to 15thNight
26%
760
19%
2471
13%
760
34%
760
18%
1684
November16th to endNight
20%
780
15%
2535
9%
780
27%
780
13%
1874
December1st to 15thNight
13%
959
7%
2714
2%
959
18%
959
10%
2227
December16th to endNight
11%
1040
7%
2912
2%
1040
16%
1040
7%
2527

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%
49387
Night
15%9%46%5%34446%34%
49041
Cloud CoverDay
13%8%36%5%3445%7%35%
49396
Night
15%9%46%5%34446%34%
49046
TransparencyDay
47%5%12%20%11%1
49073
Night
49%6%10%19%12%1
48873
SeeingDay
16%9%29%25%14%4
6448
Night
19%11%28%26%12%1
16644

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
15%16%7%11%8%5%444416%
1552
16th to endDay
12%16%9%11%7%5%443419%
1664
February1st to 15thDay
15%15%6%10%7%34445%22%
1844
16th to endDay
15%12%6%10%7%25%34427%
1643
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%
2373
16th to endDay
8%424425%46%9%46%
2292
September1st to 15thDay
13%4244345%47%45%
2114
16th to endDay
10%5%35%4345%5%9%42%
1980
October1st to 15thDay
16%6%35%5%24446%40%
1935
16th to endDay
20%9%36%5%3435%6%32%
1749
November1st to 15thDay
18%8%445%4335%5%36%
1717
16th to endDay
17%13%5%8%5%2434428%
1755
December1st to 15thDay
17%16%7%12%8%4433418%
1573
16th to endDay
20%19%6%9%6%3435%316%
1664
January1st to 15thNight
19%14%6%9%5%345%45%21%
2716
16th to endNight
14%13%8%10%7%46%445%21%
2912
February1st to 15thNight
17%12%5%8%6%35%435%26%
2345
16th to endNight
18%12%6%8%6%3344427%
1977
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%3234345%6%10%50%
1584
16th to endNight
9%31443445%6%50%
1910
September1st to 15thNight
13%423423346%50%
1833
16th to endNight
9%5%24424447%48%
1980
October1st to 15thNight
15%5%245%24446%44%
2023
16th to endNight
23%9%35%322346%34%
2475
November1st to 15thNight
16%11%46%423345%36%
2471
16th to endNight
18%13%49%5%24346%27%
2535
December1st to 15thNight
20%15%8%10%7%3333419%
2714
16th to endNight
22%17%7%10%9%4433414%
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%16%7%10%9%44445%16%
1552
16th to endDay
13%17%7%11%7%45%44418%
1664
February1st to 15thDay
14%15%7%10%7%345%45%22%
1844
16th to endDay
14%13%5%10%7%34345%26%
1643
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%
2373
16th to endDay
8%5%245%345%6%8%45%
2292
September1st to 15thDay
12%424435%45%7%45%
2114
16th to endDay
8%6%44435%46%9%42%
1980
October1st to 15thDay
16%6%35%5%33346%40%
1935
16th to endDay
19%8%47%43445%6%31%
1749
November1st to 15thDay
17%8%345%3435%5%36%
1717
16th to endDay
17%13%6%8%5%24345%28%
1755
December1st to 15thDay
16%16%6%13%8%4333418%
1573
16th to endDay
20%19%5%8%7%3445%416%
1664
January1st to 15thNight
18%14%6%9%6%3445%421%
2716
16th to endNight
14%14%7%10%7%45%5%45%20%
2912
February1st to 15thNight
17%12%6%7%6%25%445%26%
2338
16th to endNight
18%12%6%8%6%33445%27%
1977
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%3244245%7%10%49%
1584
16th to endNight
9%3245%2445%6%50%
1910
September1st to 15thNight
12%425%423347%50%
1833
16th to endNight
8%5%24425%447%48%
1980
October1st to 15thNight
15%5%14434445%45%
2023
16th to endNight
23%8%36%423346%35%
2475
November1st to 15thNight
16%11%36%434346%35%
2471
16th to endNight
18%13%48%6%23436%27%
2535
December1st to 15thNight
19%15%7%10%8%3433420%
2714
16th to endNight
21%17%6%10%8%4433414%
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
67%7%10%9%5%
1553
16th to endDay
66%6%11%11%3
1664
February1st to 15thDay
63%5%10%13%5%1
1846
16th to endDay
59%5%11%16%41
1643
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
2358
16th to endDay
35%5%14%25%16%3
2292
September1st to 15thDay
36%5%12%24%18%2
2114
16th to endDay
36%6%11%26%18%1
1980
October1st to 15thDay
44%5%11%23%13%2
1935
16th to endDay
51%5%13%20%9%
1749
November1st to 15thDay
47%5%11%19%13%2
1717
16th to endDay
56%5%10%19%5%
1755
December1st to 15thDay
68%6%8%12%4
1573
16th to endDay
69%6%10%8%3
1664
January1st to 15thNight
61%7%10%13%7%
2716
16th to endNight
61%7%12%13%4
2912
February1st to 15thNight
59%5%10%16%7%1
2347
16th to endNight
57%7%9%18%7%
1977
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
1575
16th to endNight
32%6%11%25%19%5%
1910
September1st to 15thNight
33%5%10%24%20%5%
1833
16th to endNight
33%5%7%28%21%2
1980
October1st to 15thNight
39%5%8%25%19%1
2023
16th to endNight
49%5%11%23%9%1
2475
November1st to 15thNight
48%5%8%20%13%3
2471
16th to endNight
56%5%11%20%5%
2535
December1st to 15thNight
65%6%8%13%5%
2714
16th to endNight
73%5%7%9%3
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
24%19%35%16%3
135
16th to endDay
18%14%47%17%1
144
February1st to 15thDay
24%25%40%10%
135
16th to endDay
27%15%35%16%7%
100
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%116%34%24%13%
355
16th to endDay
14%218%29%25%9%
332
September1st to 15thDay
13%417%32%24%8%
315
16th to endDay
12%7%12%31%25%9%
314
October1st to 15thDay
20%427%29%16%2
270
16th to endDay
23%12%40%19%4
144
November1st to 15thDay
16%9%31%27%13%2
135
16th to endDay
24%17%44%10%2
135
December1st to 15thDay
24%22%34%12%5%
135
16th to endDay
24%29%42%21
144
January1st to 15thNight
24%19%35%16%3
975
16th to endNight
20%17%37%21%2
1040
February1st to 15thNight
23%13%37%21%3
816
16th to endNight
23%14%35%20%5%
659
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
7%110%45%29%5%
539
16th to endNight
10%215%37%28%6%
573
September1st to 15thNight
13%5%14%34%27%5%
573
16th to endNight
11%5%20%30%28%4
717
October1st to 15thNight
18%7%25%29%18%1
720
16th to endNight
25%18%29%19%7%
768
November1st to 15thNight
22%13%33%18%11%
760
16th to endNight
23%21%29%19%5%
780
December1st to 15thNight
27%18%34%16%2
959
16th to endNight
29%16%34%17%2
1040
Page generated at 2018-02-23 10:21:30. Version ac04

Copyright 2018 A. Danko


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