Barrington Hills
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Barrington Hills clear sky chart from 2005-11-05 to 2017-09-19.

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
35%
15990
18%
46860
10%
15949
43%
15949
23%
31142

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%
900
15%
2506
4%
895
29%
895
17%
1801
January16th to endNight
19%
960
13%
2661
4%
960
27%
960
16%
1977
February1st to 15thNight
19%
803
15%
2214
4%
803
27%
803
18%
1562
February16th to endNight
23%
631
19%
1893
8%
631
33%
631
17%
1314
March1st to 15thNight
25%
720
13%
2160
7%
720
31%
720
17%
1514
March16th to endNight
29%
622
15%
2011
11%
622
35%
622
19%
1376
April1st to 15thNight
29%
539
15%
1797
9%
539
38%
539
19%
1227
April16th to endNight
33%
540
19%
1731
11%
540
43%
540
23%
1141
May1st to 15thNight
35%
540
15%
1587
8%
540
41%
540
22%
1107
May16th to endNight
46%
561
17%
1498
9%
561
51%
561
32%
968
June1st to 15thNight
50%
540
16%
1440
10%
540
53%
540
34%
902
June16th to endNight
48%
540
16%
1440
9%
540
53%
540
31%
936
July1st to 15thNight
60%
510
16%
1360
10%
510
64%
510
40%
817
July16th to endNight
65%
564
22%
1417
15%
531
70%
531
42%
837
August1st to 15thNight
72%
539
21%
1560
20%
536
74%
536
41%
877
August16th to endNight
63%
573
21%
1910
21%
573
68%
573
34%
1051
September1st to 15thNight
59%
543
29%
1803
27%
543
66%
543
36%
974
September16th to endNight
56%
673
26%
1858
18%
673
61%
673
35%
1110
October1st to 15thNight
46%
660
25%
1901
18%
660
53%
660
31%
1155
October16th to endNight
27%
704
18%
2241
9%
704
38%
704
21%
1460
November1st to 15thNight
31%
700
24%
2276
15%
700
43%
700
24%
1409
November16th to endNight
25%
768
17%
2388
8%
768
35%
768
18%
1616
December1st to 15thNight
19%
900
14%
2520
4%
900
27%
900
16%
1857
December16th to endNight
13%
960
12%
2688
3%
960
22%
960
11%
2154

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%
47964
Night
14%7%35%424446%40%
47028
Cloud CoverDay
13%8%36%5%3445%7%36%
47973
Night
14%7%35%424446%40%
47033
TransparencyDay
46%5%12%22%12%1
47650
Night
44%411%22%14%1
46860
SeeingDay
15%10%29%24%13%5%
5996
Night
18%10%29%27%12%1
15995

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
13%13%5%7%5%345%5%7%28%
1432
16th to endDay
13%14%6%9%7%3444426%
1563
February1st to 15thDay
13%13%6%7%5%35%5%45%29%
1648
16th to endDay
14%10%48%7%34346%32%
1580
March1st to 15thDay
14%12%48%5%25%45%7%29%
1790
16th to endDay
18%9%47%6%35%446%31%
2222
April1st to 15thDay
18%11%47%5%33345%31%
2151
16th to endDay
19%8%345%2345%6%35%
2226
May1st to 15thDay
18%8%47%5%35%45%7%29%
2362
16th to endDay
12%6%36%5%36%5%5%7%37%
2617
June1st to 15thDay
11%425%5%35%46%7%42%
2520
16th to endDay
9%5%26%6%45%5%7%10%37%
2520
July1st to 15thDay
8%325%5%25%6%7%9%43%
2520
16th to endDay
7%435%6%35%5%7%9%41%
2655
August1st to 15thDay
7%5%36%5%35%5%6%8%40%
2388
16th to endDay
10%425%5%35%5%6%8%41%
2292
September1st to 15thDay
12%314325%447%50%
2145
16th to endDay
10%6%24435%5%5%8%43%
1848
October1st to 15thDay
13%6%35%5%2345%6%43%
1727
16th to endDay
18%8%35%434436%36%
1631
November1st to 15thDay
14%7%35%42345%7%39%
1582
16th to endDay
17%9%5%6%5%23345%36%
1569
December1st to 15thDay
16%13%48%6%34345%29%
1440
16th to endDay
21%15%6%8%5%23435%23%
1536
January1st to 15thNight
16%11%47%433335%35%
2506
16th to endNight
13%12%7%8%5%2445%6%29%
2661
February1st to 15thNight
14%13%46%5%24336%35%
2212
16th to endNight
16%10%48%433446%34%
1893
March1st to 15thNight
15%8%46%5%34446%36%
2147
16th to endNight
16%8%26%5%3445%6%34%
2011
April1st to 15thNight
18%6%35%5%35%5%46%35%
1797
16th to endNight
20%7%35%323445%41%
1731
May1st to 15thNight
17%6%26%5%35%5%6%6%34%
1587
16th to endNight
11%435%42445%9%43%
1496
June1st to 15thNight
11%42442436%7%48%
1440
16th to endNight
8%425%5%36%5%8%9%40%
1440
July1st to 15thNight
5%2143246%6%9%51%
1440
16th to endNight
6%313335%5%7%10%50%
1513
August1st to 15thNight
4213425%5%6%9%53%
1569
16th to endNight
10%32332335%8%53%
1910
September1st to 15thNight
9%314323337%56%
1803
16th to endNight
9%41433345%8%50%
1858
October1st to 15thNight
12%424324346%49%
1901
16th to endNight
19%8%24413346%41%
2241
November1st to 15thNight
12%8%25%423346%46%
2276
16th to endNight
15%10%46%424345%37%
2388
December1st to 15thNight
20%9%47%5%24435%31%
2520
16th to endNight
23%13%5%7%5%24445%22%
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
13%12%5%7%5%345%47%28%
1432
16th to endDay
13%14%6%9%7%34435%26%
1563
February1st to 15thDay
13%13%6%7%5%35%5%45%28%
1648
16th to endDay
14%11%5%8%7%33445%32%
1580
March1st to 15thDay
15%12%48%5%25%447%29%
1800
16th to endDay
18%9%46%5%34446%31%
2221
April1st to 15thDay
18%11%47%434345%31%
2151
16th to endDay
19%9%245%2435%6%35%
2226
May1st to 15thDay
17%9%36%6%35%5%5%6%29%
2362
16th to endDay
12%6%36%5%36%5%5%7%37%
2617
June1st to 15thDay
11%426%5%3446%7%43%
2520
16th to endDay
9%5%26%6%35%5%7%9%38%
2520
July1st to 15thDay
8%3245%36%5%7%9%43%
2520
16th to endDay
7%425%5%35%5%6%9%42%
2655
August1st to 15thDay
7%5%26%5%35%5%6%8%41%
2388
16th to endDay
10%5%25%5%35%5%6%8%41%
2292
September1st to 15thDay
12%313424447%50%
2145
16th to endDay
10%6%24425%5%6%8%43%
1848
October1st to 15thDay
13%6%35%5%2346%5%43%
1727
16th to endDay
19%8%345%24445%37%
1631
November1st to 15thDay
14%8%35%42345%7%39%
1582
16th to endDay
17%9%46%5%23335%36%
1569
December1st to 15thDay
16%13%48%5%3434429%
1440
16th to endDay
21%15%6%7%5%24436%23%
1536
January1st to 15thNight
17%10%5%6%5%23345%34%
2506
16th to endNight
13%12%7%9%424447%28%
2661
February1st to 15thNight
14%13%5%5%5%24336%35%
2205
16th to endNight
16%11%38%5%24346%34%
1893
March1st to 15thNight
16%8%46%5%34345%35%
2160
16th to endNight
16%8%35%5%35%45%7%34%
2011
April1st to 15thNight
18%6%35%435%445%35%
1797
16th to endNight
20%6%25%324345%41%
1731
May1st to 15thNight
17%6%26%5%25%5%5%7%34%
1586
16th to endNight
11%435%42445%9%43%
1496
June1st to 15thNight
11%42442435%6%48%
1440
16th to endNight
8%435%5%36%6%7%9%40%
1440
July1st to 15thNight
6%2144246%7%9%51%
1440
16th to endNight
6%213335%48%9%51%
1513
August1st to 15thNight
42135%25%5%6%9%54%
1569
16th to endNight
10%314423448%52%
1910
September1st to 15thNight
9%314323337%56%
1803
16th to endNight
9%42432445%7%51%
1858
October1st to 15thNight
12%5%14423446%49%
1901
16th to endNight
19%8%24323345%41%
2241
November1st to 15thNight
13%8%25%423245%46%
2276
16th to endNight
16%9%46%5%24345%37%
2388
December1st to 15thNight
20%9%47%5%23445%31%
2520
16th to endNight
23%14%5%7%5%33445%22%
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
54%5%14%15%9%
1433
16th to endDay
60%311%16%7%
1563
February1st to 15thDay
56%411%17%9%1
1650
16th to endDay
53%5%12%19%8%1
1580
March1st to 15thDay
55%5%12%18%8%1
1800
16th to endDay
54%5%13%20%5%
2222
April1st to 15thDay
55%39%20%10%
2151
16th to endDay
48%6%12%17%12%3
2226
May1st to 15thDay
53%7%10%21%6%
2362
16th to endDay
44%5%12%20%14%1
2621
June1st to 15thDay
38%6%11%24%17%1
2520
16th to endDay
40%8%13%20%15%2
2520
July1st to 15thDay
33%7%12%28%14%2
2371
16th to endDay
34%8%15%22%14%3
2488
August1st to 15thDay
38%7%11%28%12%1
2373
16th to endDay
37%6%12%24%16%2
2292
September1st to 15thDay
33%5%10%26%20%3
2145
16th to endDay
37%410%29%15%
1848
October1st to 15thDay
40%5%10%26%14%1
1727
16th to endDay
48%412%23%9%1
1631
November1st to 15thDay
43%412%23%14%2
1582
16th to endDay
50%412%23%7%
1569
December1st to 15thDay
57%412%18%7%
1440
16th to endDay
63%5%10%12%7%
1536
January1st to 15thNight
52%311%20%11%1
2506
16th to endNight
55%313%15%10%
2661
February1st to 15thNight
51%312%20%11%
2214
16th to endNight
51%311%23%8%2
1893
March1st to 15thNight
50%5%12%17%11%2
2160
16th to endNight
49%414%21%8%1
2011
April1st to 15thNight
49%49%20%14%1
1797
16th to endNight
45%410%22%12%4
1731
May1st to 15thNight
47%5%11%22%11%
1587
16th to endNight
36%7%13%22%17%2
1498
June1st to 15thNight
34%5%10%26%19%2
1440
16th to endNight
37%6%14%21%18%1
1440
July1st to 15thNight
28%7%14%28%18%3
1360
16th to endNight
26%7%16%26%18%4
1417
August1st to 15thNight
24%8%15%30%19%1
1560
16th to endNight
30%5%12%28%18%4
1910
September1st to 15thNight
29%48%27%27%2
1803
16th to endNight
32%410%33%16%1
1858
October1st to 15thNight
35%410%27%20%1
1901
16th to endNight
45%312%24%12%1
2241
November1st to 15thNight
40%38%25%17%3
2276
16th to endNight
48%313%22%11%
2388
December1st to 15thNight
55%310%20%9%
2520
16th to endNight
65%310%13%6%
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
20%17%40%20%2
90
16th to endDay
23%19%23%22%7%2
96
February1st to 15thDay
22%22%45%10%
90
16th to endDay
27%13%32%13%9%3
81
March1st to 15thDay
35%20%30%11%3
90
16th to endDay
27%11%29%19%9%2
242
April1st to 15thDay
25%13%26%24%9%
270
16th to endDay
23%14%26%20%11%3
270
May1st to 15thDay
22%15%30%18%8%4
319
16th to endDay
17%13%31%22%11%4
517
June1st to 15thDay
11%10%34%25%14%4
495
16th to endDay
12%10%35%25%10%5%
495
July1st to 15thDay
6%5%33%29%15%8%
475
16th to endDay
8%428%34%15%8%
515
August1st to 15thDay
9%322%30%20%12%
409
16th to endDay
11%418%31%21%13%
332
September1st to 15thDay
9%421%29%24%10%
315
16th to endDay
10%6%20%26%25%9%
266
October1st to 15thDay
10%12%29%26%16%4
167
16th to endDay
31%14%36%16%1
96
November1st to 15thDay
8%13%25%33%15%3
90
16th to endDay
28%16%38%8%5%1
90
December1st to 15thDay
18%25%33%18%3
90
16th to endDay
27%33%35%22
96
January1st to 15thNight
21%17%36%19%5%
900
16th to endNight
20%14%36%24%3
960
February1st to 15thNight
21%14%35%23%4
806
16th to endNight
21%15%31%24%5%
631
March1st to 15thNight
20%15%33%22%8%
720
16th to endNight
19%10%33%26%9%1
622
April1st to 15thNight
23%10%33%25%6%
539
16th to endNight
23%8%31%26%7%1
540
May1st to 15thNight
20%7%31%30%8%1
540
16th to endNight
12%6%28%33%17%1
563
June1st to 15thNight
14%325%40%15%
540
16th to endNight
10%431%34%18%
540
July1st to 15thNight
7%124%38%24%2
510
16th to endNight
5%121%41%26%2
564
August1st to 15thNight
4114%46%30%3
539
16th to endNight
9%217%34%31%4
573
September1st to 15thNight
10%320%31%28%5%
543
16th to endNight
10%6%20%31%27%3
673
October1st to 15thNight
16%7%24%30%17%2
660
16th to endNight
24%13%31%21%8%
704
November1st to 15thNight
18%12%34%23%9%1
700
16th to endNight
21%16%31%22%7%
768
December1st to 15thNight
26%14%33%20%4
900
16th to endNight
31%14%32%19%2
960
Page generated at 2017-09-20 03:49:44. Version ac04

Copyright 2017 A. Danko


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