Morton Grove
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morton Grove 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
38%
15859
17%
46467
10%
15818
44%
15818
23%
31229

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
13%
2506
4%
895
28%
895
18%
1831
January16th to endNight
19%
960
11%
2673
4%
960
26%
960
15%
1995
February1st to 15thNight
22%
786
14%
2197
3%
786
29%
786
19%
1562
February16th to endNight
27%
631
18%
1893
8%
631
37%
631
18%
1332
March1st to 15thNight
28%
720
13%
2160
7%
720
32%
720
18%
1522
March16th to endNight
33%
639
14%
2019
10%
639
39%
639
20%
1394
April1st to 15thNight
32%
539
15%
1797
11%
539
40%
539
20%
1220
April16th to endNight
37%
540
19%
1722
12%
540
46%
540
23%
1147
May1st to 15thNight
41%
540
15%
1607
10%
540
46%
540
21%
1141
May16th to endNight
55%
561
17%
1498
11%
561
58%
561
32%
966
June1st to 15thNight
57%
540
15%
1440
11%
540
60%
540
34%
915
June16th to endNight
55%
540
15%
1440
10%
540
58%
540
31%
933
July1st to 15thNight
67%
510
16%
1360
12%
510
68%
510
40%
814
July16th to endNight
70%
564
21%
1417
15%
531
73%
531
41%
838
August1st to 15thNight
75%
527
22%
1523
21%
524
76%
524
41%
858
August16th to endNight
64%
525
19%
1750
19%
525
69%
525
34%
982
September1st to 15thNight
62%
506
28%
1661
28%
506
67%
506
34%
929
September16th to endNight
57%
657
25%
1815
19%
657
61%
657
34%
1118
October1st to 15thNight
47%
660
24%
1886
18%
660
53%
660
31%
1171
October16th to endNight
29%
704
17%
2249
9%
704
39%
704
20%
1491
November1st to 15thNight
32%
700
22%
2276
16%
700
43%
700
23%
1417
November16th to endNight
26%
750
16%
2370
9%
750
35%
750
18%
1604
December1st to 15thNight
19%
900
11%
2520
3%
900
25%
900
16%
1880
December16th to endNight
15%
960
10%
2688
2%
960
23%
960
11%
2169

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%35%45%7%36%
47511
Night
14%8%35%424446%39%
46635
Cloud CoverDay
13%8%35%5%35%45%7%36%
47520
Night
15%8%35%424446%39%
46640
TransparencyDay
46%6%13%21%11%1
47197
Night
44%5%13%22%12%1
46467
SeeingDay
16%6%27%30%14%4
5831
Night
19%8%27%29%13%1
15864

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%12%47%5%35%45%7%27%
1432
16th to endDay
13%16%7%8%6%35%446%23%
1551
February1st to 15thDay
14%14%6%7%6%35%445%27%
1663
16th to endDay
14%10%47%6%35%5%47%30%
1580
March1st to 15thDay
15%12%48%435%446%29%
1790
16th to endDay
17%8%47%6%25%446%30%
2216
April1st to 15thDay
19%9%45%6%2435%5%32%
2151
16th to endDay
19%7%344345%5%7%35%
2238
May1st to 15thDay
18%9%37%5%34448%30%
2342
16th to endDay
13%5%35%6%35%46%7%38%
2617
June1st to 15thDay
11%5%25%43446%7%43%
2520
16th to endDay
10%435%6%35%5%7%9%37%
2520
July1st to 15thDay
7%4244346%6%8%46%
2520
16th to endDay
7%425%445%6%7%9%41%
2655
August1st to 15thDay
7%5%25%5%35%5%6%10%42%
2336
16th to endDay
9%5%246%35%5%7%8%40%
2100
September1st to 15thDay
13%5%133345%5%6%47%
1957
16th to endDay
10%5%25%435%5%7%8%41%
1815
October1st to 15thDay
14%6%25%444445%42%
1742
16th to endDay
17%8%36%5%34446%35%
1621
November1st to 15thDay
13%8%35%5%2435%7%40%
1582
16th to endDay
16%10%36%5%34426%35%
1587
December1st to 15thDay
17%13%48%5%34436%27%
1440
16th to endDay
22%15%5%8%5%34336%22%
1536
January1st to 15thNight
17%10%47%5%24345%34%
2506
16th to endNight
14%12%7%9%5%24347%29%
2673
February1st to 15thNight
15%12%35%43435%5%34%
2195
16th to endNight
16%10%46%5%24345%34%
1893
March1st to 15thNight
17%10%36%5%34335%36%
2147
16th to endNight
16%8%26%435%5%5%7%33%
2019
April1st to 15thNight
18%7%36%435%447%35%
1797
16th to endNight
20%7%3432335%6%39%
1722
May1st to 15thNight
17%7%36%425%45%6%34%
1607
16th to endNight
10%4245%345%6%9%43%
1496
June1st to 15thNight
11%5%14425%45%6%48%
1440
16th to endNight
8%5%25%436%6%7%9%40%
1440
July1st to 15thNight
7%235%25%5%7%8%51%
1440
16th to endNight
6%3234345%7%9%49%
1513
August1st to 15thNight
33135%25%5%6%9%53%
1532
16th to endNight
9%323424348%52%
1750
September1st to 15thNight
10%413423446%54%
1661
16th to endNight
9%5%24424447%49%
1815
October1st to 15thNight
13%6%24423346%48%
1886
16th to endNight
20%7%24423345%40%
2249
November1st to 15thNight
13%8%25%423436%45%
2276
16th to endNight
17%8%36%5%24345%37%
2370
December1st to 15thNight
21%10%36%5%24446%30%
2520
16th to endNight
23%15%47%5%35%33421%
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
15%11%5%8%435%46%7%26%
1432
16th to endDay
12%16%7%10%6%25%447%23%
1551
February1st to 15thDay
14%13%6%8%5%35%5%5%5%27%
1663
16th to endDay
13%11%48%6%35%5%5%7%30%
1580
March1st to 15thDay
16%11%47%5%35%346%30%
1800
16th to endDay
17%8%46%5%25%447%30%
2215
April1st to 15thDay
19%9%45%6%34446%32%
2151
16th to endDay
18%8%25%4345%46%36%
2238
May1st to 15thDay
18%8%46%6%3345%7%31%
2342
16th to endDay
13%5%35%5%35%46%8%38%
2617
June1st to 15thDay
12%4245%35%5%5%8%43%
2520
16th to endDay
10%5%35%5%35%5%6%10%38%
2520
July1st to 15thDay
7%5%24425%5%6%8%47%
2520
16th to endDay
7%424436%6%6%9%44%
2655
August1st to 15thDay
7%5%25%435%5%6%8%44%
2336
16th to endDay
10%434436%47%8%41%
2100
September1st to 15thDay
13%41333445%7%47%
1957
16th to endDay
10%5%25%4345%7%9%40%
1815
October1st to 15thDay
15%6%2443435%6%42%
1742
16th to endDay
17%8%36%5%34446%35%
1621
November1st to 15thDay
13%8%36%5%2435%7%40%
1582
16th to endDay
17%9%46%434426%36%
1587
December1st to 15thDay
17%13%5%7%435%446%26%
1440
16th to endDay
22%15%5%7%5%33445%22%
1536
January1st to 15thNight
17%10%47%424345%33%
2506
16th to endNight
14%12%7%9%5%33347%28%
2673
February1st to 15thNight
15%12%45%424445%35%
2188
16th to endNight
16%10%47%434345%34%
1893
March1st to 15thNight
17%9%36%5%3334436%
2160
16th to endNight
16%8%26%436%447%33%
2019
April1st to 15thNight
18%6%35%5%35%35%6%35%
1797
16th to endNight
20%7%24324346%40%
1722
May1st to 15thNight
18%8%36%5%345%46%34%
1606
16th to endNight
10%425%5%345%6%9%43%
1496
June1st to 15thNight
12%414425%45%7%47%
1440
16th to endNight
8%5%24425%6%7%9%40%
1440
July1st to 15thNight
7%235%345%6%8%51%
1440
16th to endNight
6%3134246%6%9%50%
1513
August1st to 15thNight
5%313425%5%6%8%54%
1532
16th to endNight
9%41342435%8%52%
1750
September1st to 15thNight
12%313422447%53%
1661
16th to endNight
10%5%14425%347%49%
1815
October1st to 15thNight
14%5%23423346%47%
1886
16th to endNight
20%7%25%423345%39%
2249
November1st to 15thNight
13%7%25%423345%45%
2276
16th to endNight
17%8%46%5%23446%37%
2370
December1st to 15thNight
21%10%36%5%2445%5%29%
2520
16th to endNight
24%15%46%5%3434422%
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
55%6%15%15%7%
1433
16th to endDay
60%5%12%14%6%
1551
February1st to 15thDay
57%5%11%16%7%1
1665
16th to endDay
53%6%11%20%6%
1580
March1st to 15thDay
54%5%14%17%7%1
1800
16th to endDay
53%5%14%20%4
2216
April1st to 15thDay
52%5%9%20%11%
2151
16th to endDay
47%6%12%17%12%3
2238
May1st to 15thDay
52%6%12%21%6%
2342
16th to endDay
43%6%13%21%14%1
2621
June1st to 15thDay
38%6%11%22%18%1
2520
16th to endDay
39%7%14%20%15%2
2520
July1st to 15thDay
33%7%13%27%14%2
2371
16th to endDay
34%9%15%22%14%3
2488
August1st to 15thDay
34%7%14%27%13%1
2321
16th to endDay
36%7%14%23%15%2
2100
September1st to 15thDay
35%5%12%24%18%2
1957
16th to endDay
37%6%13%26%14%1
1815
October1st to 15thDay
42%5%11%24%14%1
1742
16th to endDay
50%412%22%8%1
1621
November1st to 15thDay
43%412%23%13%2
1582
16th to endDay
51%5%15%21%6%
1587
December1st to 15thDay
57%418%15%4
1440
16th to endDay
63%6%11%11%5%
1536
January1st to 15thNight
53%413%19%8%
2506
16th to endNight
56%415%16%6%
2673
February1st to 15thNight
51%413%19%10%1
2197
16th to endNight
52%311%21%8%1
1893
March1st to 15thNight
51%412%17%10%2
2160
16th to endNight
48%5%15%20%7%1
2019
April1st to 15thNight
48%410%20%14%1
1797
16th to endNight
45%410%20%13%4
1722
May1st to 15thNight
49%6%10%22%11%
1607
16th to endNight
36%6%14%21%17%2
1498
June1st to 15thNight
35%5%11%25%18%2
1440
16th to endNight
35%8%15%21%18%1
1440
July1st to 15thNight
28%7%15%26%19%3
1360
16th to endNight
26%8%17%25%19%3
1417
August1st to 15thNight
25%7%15%28%20%2
1523
16th to endNight
30%5%13%27%17%4
1750
September1st to 15thNight
30%5%9%26%24%2
1661
16th to endNight
33%6%9%30%17%2
1815
October1st to 15thNight
37%411%26%19%1
1886
16th to endNight
46%412%24%10%1
2249
November1st to 15thNight
40%410%24%16%3
2276
16th to endNight
48%415%22%8%
2370
December1st to 15thNight
54%5%14%17%6%
2520
16th to endNight
65%410%13%4
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
23%11%37%25%2
90
16th to endDay
17%9%36%30%6%
96
February1st to 15thDay
20%16%50%13%
90
16th to endDay
14%12%37%25%7%2
81
March1st to 15thDay
30%14%32%21%2
90
16th to endDay
30%7%28%21%10%1
252
April1st to 15thDay
21%12%31%25%9%
270
16th to endDay
21%9%30%22%11%4
270
May1st to 15thDay
23%8%29%26%9%3
299
16th to endDay
16%5%29%32%13%3
517
June1st to 15thDay
13%326%35%16%3
495
16th to endDay
12%334%33%10%5%
495
July1st to 15thDay
9%225%37%17%7%
475
16th to endDay
8%122%39%20%6%
515
August1st to 15thDay
10%114%39%21%12%
375
16th to endDay
11%415%34%21%12%
268
September1st to 15thDay
13%315%34%23%9%
255
16th to endDay
12%418%31%25%7%
254
October1st to 15thDay
20%5%21%29%19%3
182
16th to endDay
26%12%34%26%1
96
November1st to 15thDay
6%14%24%32%18%3
90
16th to endDay
25%13%42%13%5%
90
December1st to 15thDay
17%22%33%21%41
90
16th to endDay
32%17%45%22
96
January1st to 15thNight
22%14%37%19%4
900
16th to endNight
19%13%36%26%2
960
February1st to 15thNight
21%10%38%24%5%
789
16th to endNight
21%9%33%28%5%
631
March1st to 15thNight
21%10%33%24%9%
720
16th to endNight
20%7%32%28%10%1
639
April1st to 15thNight
22%9%30%28%7%
539
16th to endNight
24%5%27%27%12%1
540
May1st to 15thNight
21%425%34%12%1
540
16th to endNight
11%421%38%23%1
563
June1st to 15thNight
14%19%43%20%1
540
16th to endNight
11%224%37%22%1
540
July1st to 15thNight
10%114%42%28%3
510
16th to endNight
7%114%42%30%3
564
August1st to 15thNight
6%9%43%33%6%
527
16th to endNight
11%214%33%32%5%
525
September1st to 15thNight
13%415%31%27%7%
506
16th to endNight
13%5%18%30%28%4
657
October1st to 15thNight
17%8%21%30%20%2
660
16th to endNight
24%12%30%23%8%
704
November1st to 15thNight
18%11%34%22%12%1
700
16th to endNight
20%16%31%23%7%
750
December1st to 15thNight
27%13%34%20%4
900
16th to endNight
31%13%31%21%1
960
Page generated at 2017-08-13 13:16:53. Version ac04

Copyright 2017 A. Danko


Morton Grove Clear Sky Chart | Charts Home