Island Lake State Recreation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Island Lake State Recreation Area clear sky chart from 2005-11-05 to 2018-02-14.

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
38%
16530
15%
48967
10%
16488
43%
16488
21%
34158

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
19%
975
10%
2716
4%
970
24%
970
13%
2134
January16th to endNight
21%
936
8%
2808
3%
936
25%
936
11%
2235
February1st to 15thNight
19%
757
9%
2432
3%
757
25%
757
11%
1872
February16th to endNight
25%
631
13%
1893
6%
631
32%
631
16%
1383
March1st to 15thNight
27%
720
15%
2082
8%
720
32%
720
17%
1513
March16th to endNight
34%
768
18%
2112
10%
768
40%
768
21%
1482
April1st to 15thNight
30%
581
14%
1809
7%
581
37%
581
18%
1261
April16th to endNight
36%
540
19%
1620
8%
540
46%
540
25%
1087
May1st to 15thNight
39%
540
14%
1620
8%
540
44%
540
21%
1127
May16th to endNight
50%
562
15%
1671
12%
561
55%
561
28%
1070
June1st to 15thNight
56%
540
14%
1440
11%
540
60%
540
33%
915
June16th to endNight
58%
540
16%
1440
12%
540
62%
540
34%
911
July1st to 15thNight
66%
510
16%
1360
14%
510
68%
510
40%
804
July16th to endNight
69%
564
19%
1495
16%
531
72%
531
39%
875
August1st to 15thNight
67%
539
20%
1609
17%
536
69%
536
34%
956
August16th to endNight
65%
573
23%
1748
18%
573
69%
573
33%
1037
September1st to 15thNight
58%
663
25%
1923
19%
663
63%
663
35%
1138
September16th to endNight
60%
717
25%
1980
19%
717
64%
717
34%
1217
October1st to 15thNight
46%
720
18%
2064
15%
720
50%
720
27%
1364
October16th to endNight
28%
768
16%
2412
10%
768
37%
768
18%
1702
November1st to 15thNight
36%
760
18%
2471
15%
760
42%
760
22%
1626
November16th to endNight
25%
780
14%
2558
9%
780
32%
780
15%
1839
December1st to 15thNight
19%
806
8%
2756
4%
806
25%
806
10%
2131
December16th to endNight
15%
1040
7%
2948
1%
1040
20%
1040
8%
2479

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%32%
49095
Night
15%8%46%5%3445%6%35%
49145
Cloud CoverDay
14%8%47%6%35%45%7%32%
49105
Night
15%8%36%5%3445%6%35%
49149
TransparencyDay
49%6%12%19%10%1
48791
Night
48%5%12%20%11%1
48967
SeeingDay
17%7%27%23%16%7%
6309
Night
19%7%28%30%12%1
16534

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%5%9%7%46%445%16%
1552
16th to endDay
17%16%8%9%8%44446%16%
1765
February1st to 15thDay
15%14%6%10%8%36%45%5%18%
1728
16th to endDay
14%14%5%11%7%35%45%6%21%
1580
March1st to 15thDay
16%11%48%5%35%35%6%28%
1867
16th to endDay
17%9%5%8%6%35%335%30%
2112
April1st to 15thDay
19%10%35%5%34446%30%
2150
16th to endDay
16%8%36%5%24446%38%
2340
May1st to 15thDay
19%7%27%6%35%346%32%
2331
16th to endDay
13%6%25%5%35%45%9%38%
2441
June1st to 15thDay
10%5%36%5%35%46%8%40%
2520
16th to endDay
10%5%35%6%46%6%7%11%34%
2520
July1st to 15thDay
7%435%5%345%5%8%45%
2520
16th to endDay
8%5%25%6%346%7%10%38%
2568
August1st to 15thDay
8%5%25%7%46%6%7%7%38%
2340
16th to endDay
11%425%5%35%5%7%9%38%
2453
September1st to 15thDay
11%5%25%5%45%45%9%40%
2025
16th to endDay
12%5%25%5%25%5%6%9%41%
1980
October1st to 15thDay
15%6%25%6%35%346%38%
1896
16th to endDay
20%9%45%6%235%46%32%
1809
November1st to 15thDay
15%8%46%5%3445%6%36%
1717
16th to endDay
16%12%5%8%6%34346%28%
1728
December1st to 15thDay
15%13%6%11%6%34446%22%
1531
16th to endDay
22%14%9%11%6%3434415%
1622
January1st to 15thNight
21%12%5%7%6%34345%24%
2716
16th to endNight
13%12%7%11%7%45%45%5%21%
2808
February1st to 15thNight
16%14%6%7%6%44445%26%
2430
16th to endNight
16%9%5%7%7%35%45%6%28%
1893
March1st to 15thNight
17%9%46%5%2445%5%33%
2070
16th to endNight
15%7%36%5%35%5%5%6%36%
2112
April1st to 15thNight
19%7%35%43445%6%33%
1809
16th to endNight
16%6%25%5%245%5%6%39%
1620
May1st to 15thNight
17%6%36%5%35%45%7%34%
1620
16th to endNight
12%425%5%25%448%44%
1669
June1st to 15thNight
10%4145%25%46%8%46%
1440
16th to endNight
9%325%4245%7%9%43%
1440
July1st to 15thNight
7%3144245%5%8%51%
1440
16th to endNight
5%3245%35%4410%52%
1598
August1st to 15thNight
5%3245%35%5%6%8%48%
1620
16th to endNight
9%5%24424447%51%
1748
September1st to 15thNight
11%414324346%52%
1923
16th to endNight
10%5%245%2445%7%48%
1980
October1st to 15thNight
15%6%25%434347%41%
2064
16th to endNight
20%7%35%5%34445%34%
2412
November1st to 15thNight
15%7%35%435%35%6%39%
2471
16th to endNight
20%10%5%6%424446%29%
2558
December1st to 15thNight
20%12%5%9%6%35%445%22%
2756
16th to endNight
21%15%7%9%7%35%44416%
2948

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%17%5%9%8%45%5%45%17%
1552
16th to endDay
17%16%8%9%8%44445%16%
1765
February1st to 15thDay
15%14%6%11%8%36%446%18%
1728
16th to endDay
14%14%5%11%8%3445%6%21%
1580
March1st to 15thDay
17%11%48%6%3445%6%28%
1878
16th to endDay
17%9%48%6%24446%30%
2111
April1st to 15thDay
19%10%45%5%35%446%30%
2150
16th to endDay
16%7%36%433445%38%
2340
May1st to 15thDay
19%7%36%6%35%446%32%
2331
16th to endDay
13%5%35%5%3445%9%38%
2441
June1st to 15thDay
10%5%36%5%35%5%6%8%40%
2520
16th to endDay
10%425%6%46%6%7%11%34%
2520
July1st to 15thDay
7%425%5%35%46%8%45%
2520
16th to endDay
8%426%6%445%7%10%38%
2568
August1st to 15thDay
8%5%25%7%46%6%6%8%38%
2340
16th to endDay
11%425%5%35%5%7%9%38%
2453
September1st to 15thDay
11%5%25%5%45%46%8%40%
2025
16th to endDay
11%425%435%5%6%8%41%
1980
October1st to 15thDay
15%6%25%6%34446%38%
1896
16th to endDay
20%9%46%5%34446%32%
1809
November1st to 15thDay
15%8%35%6%3445%6%36%
1717
16th to endDay
17%11%48%6%35%346%28%
1728
December1st to 15thDay
16%12%6%10%7%34446%22%
1531
16th to endDay
22%15%9%10%7%34345%15%
1622
January1st to 15thNight
21%12%5%7%7%24445%24%
2716
16th to endNight
14%12%7%10%7%45%45%5%20%
2808
February1st to 15thNight
16%13%6%8%6%3444426%
2423
16th to endNight
16%10%5%7%7%35%446%28%
1893
March1st to 15thNight
18%9%46%6%2445%6%32%
2082
16th to endNight
15%7%36%5%345%5%6%36%
2112
April1st to 15thNight
18%8%26%5%3445%6%33%
1809
16th to endNight
15%6%25%4245%5%7%38%
1620
May1st to 15thNight
17%6%26%5%35%45%8%34%
1619
16th to endNight
12%5%245%25%447%44%
1669
June1st to 15thNight
10%4245%25%46%8%45%
1440
16th to endNight
8%4244246%7%9%43%
1440
July1st to 15thNight
7%214425%46%7%52%
1440
16th to endNight
43245%344411%51%
1598
August1st to 15thNight
5%3345%36%5%5%8%49%
1620
16th to endNight
9%424423447%51%
1748
September1st to 15thNight
11%414323446%52%
1923
16th to endNight
10%5%245%2345%7%48%
1980
October1st to 15thNight
15%5%34434447%41%
2064
16th to endNight
20%8%26%5%3445%5%34%
2412
November1st to 15thNight
15%7%35%43445%6%39%
2471
16th to endNight
20%10%46%5%34346%29%
2558
December1st to 15thNight
20%12%5%8%6%35%45%5%22%
2756
16th to endNight
21%15%6%9%6%44445%16%
2948

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%5%11%10%4
1553
16th to endDay
69%6%9%9%4
1765
February1st to 15thDay
65%6%8%12%5%
1730
16th to endDay
63%6%10%13%5%
1580
March1st to 15thDay
56%6%11%16%7%1
1878
16th to endDay
55%411%19%7%1
2112
April1st to 15thDay
54%5%10%19%10%
2150
16th to endDay
46%5%13%16%14%2
2340
May1st to 15thDay
52%5%11%18%9%2
2331
16th to endDay
42%6%12%24%12%1
2445
June1st to 15thDay
39%7%12%24%14%1
2520
16th to endDay
40%9%13%19%15%
2520
July1st to 15thDay
34%7%11%25%18%2
2371
16th to endDay
37%9%14%20%15%2
2408
August1st to 15thDay
40%7%13%23%12%1
2327
16th to endDay
39%8%11%22%15%1
2453
September1st to 15thDay
39%6%13%25%13%
2025
16th to endDay
38%6%10%30%13%
1980
October1st to 15thDay
44%6%11%22%12%2
1896
16th to endDay
53%5%14%17%8%
1809
November1st to 15thDay
47%5%11%21%11%1
1717
16th to endDay
57%413%18%6%
1728
December1st to 15thDay
63%5%11%14%4
1531
16th to endDay
72%411%8%2
1622
January1st to 15thNight
62%412%12%7%
2716
16th to endNight
63%6%13%11%4
2808
February1st to 15thNight
60%6%10%14%7%
2432
16th to endNight
55%414%17%6%
1893
March1st to 15thNight
52%5%10%18%10%1
2082
16th to endNight
48%5%12%22%9%1
2112
April1st to 15thNight
49%5%10%19%14%
1809
16th to endNight
43%5%12%18%17%3
1620
May1st to 15thNight
48%6%11%20%11%2
1620
16th to endNight
38%6%12%23%15%3
1671
June1st to 15thNight
35%7%13%27%15%1
1440
16th to endNight
33%7%15%24%17%1
1440
July1st to 15thNight
30%5%11%29%21%2
1360
16th to endNight
28%6%16%24%20%3
1495
August1st to 15thNight
30%7%12%31%15%2
1609
16th to endNight
32%6%10%28%18%2
1748
September1st to 15thNight
32%5%10%30%20%1
1923
16th to endNight
34%5%11%30%17%
1980
October1st to 15thNight
42%412%21%16%1
2064
16th to endNight
50%5%12%21%8%
2412
November1st to 15thNight
45%5%13%22%12%1
2471
16th to endNight
54%413%19%6%
2558
December1st to 15thNight
61%6%12%12%6%
2756
16th to endNight
69%6%10%9%3
2948

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
19%11%43%18%5%1
135
16th to endDay
29%9%43%15%2
144
February1st to 15thDay
25%18%41%14%
130
16th to endDay
22%12%40%23%1
81
March1st to 15thDay
30%12%29%20%7%
168
16th to endDay
23%8%29%27%9%1
288
April1st to 15thDay
21%10%32%24%9%2
270
16th to endDay
21%10%30%17%13%7%
270
May1st to 15thDay
27%6%26%20%13%5%
288
16th to endDay
17%8%24%23%17%9%
341
June1st to 15thDay
12%431%29%16%5%
495
16th to endDay
12%5%32%26%16%6%
495
July1st to 15thDay
9%6%23%28%21%10%
475
16th to endDay
9%322%27%24%12%
428
August1st to 15thDay
10%214%28%24%19%
313
16th to endDay
14%315%19%27%19%
332
September1st to 15thDay
11%320%20%26%17%
315
16th to endDay
15%215%22%28%15%
314
October1st to 15thDay
18%6%22%26%18%7%
315
16th to endDay
25%8%30%29%5%
225
November1st to 15thDay
20%10%28%23%15%2
135
16th to endDay
22%17%37%17%4
128
December1st to 15thDay
20%25%32%13%8%
90
16th to endDay
27%23%36%11%
134
January1st to 15thNight
26%12%33%21%5%
975
16th to endNight
19%11%36%27%5%
936
February1st to 15thNight
23%12%37%22%3
760
16th to endNight
22%10%33%29%3
631
March1st to 15thNight
22%11%32%27%5%
720
16th to endNight
18%9%30%30%9%1
768
April1st to 15thNight
22%12%29%29%5%
581
16th to endNight
19%6%34%28%9%1
540
May1st to 15thNight
20%5%27%36%8%1
540
16th to endNight
14%323%36%18%2
563
June1st to 15thNight
11%123%48%14%
540
16th to endNight
10%222%42%20%1
540
July1st to 15thNight
10%116%40%27%3
510
16th to endNight
5%115%48%25%3
564
August1st to 15thNight
6%116%44%27%3
539
16th to endNight
11%114%33%34%4
573
September1st to 15thNight
13%318%30%27%5%
663
16th to endNight
12%415%31%29%6%
717
October1st to 15thNight
18%5%24%31%17%3
720
16th to endNight
24%10%33%24%6%
768
November1st to 15thNight
18%8%30%28%11%1
760
16th to endNight
25%12%31%21%8%
780
December1st to 15thNight
25%12%35%21%4
806
16th to endNight
29%10%36%19%3
1040
Page generated at 2018-02-15 10:58:40. Version ac04

Copyright 2018 A. Danko


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