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 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%
16645
17%
48791
11%
16604
44%
16604
23%
32710

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
21%
975
13%
2716
4%
970
29%
970
18%
1967
January16th to endNight
20%
1040
12%
2895
4%
1040
27%
1040
16%
2148
February1st to 15thNight
22%
849
14%
2372
4%
849
30%
849
19%
1693
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
38%
639
20%
1394
April1st to 15thNight
32%
539
15%
1797
11%
539
40%
539
20%
1220
April16th to endNight
38%
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
59%
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
69%
510
40%
814
July16th to endNight
70%
564
21%
1417
15%
531
73%
531
41%
838
August1st to 15thNight
75%
539
22%
1560
21%
536
76%
536
42%
878
August16th to endNight
65%
573
21%
1910
20%
573
69%
573
34%
1071
September1st to 15thNight
62%
552
27%
1812
27%
552
67%
552
34%
1004
September16th to endNight
58%
717
27%
1980
20%
717
62%
717
35%
1199
October1st to 15thNight
46%
720
23%
2058
17%
720
51%
720
30%
1287
October16th to endNight
30%
768
19%
2454
10%
768
40%
768
20%
1618
November1st to 15thNight
32%
760
21%
2471
15%
760
42%
760
22%
1559
November16th to endNight
25%
813
17%
2568
9%
813
36%
813
19%
1714
December1st to 15thNight
20%
975
11%
2730
3%
975
26%
975
16%
2013
December16th to endNight
15%
1040
11%
2912
2%
1040
23%
1040
11%
2337

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%
49290
Night
14%8%35%424446%39%
48959
Cloud CoverDay
13%8%35%5%3445%7%37%
49299
Night
15%8%35%424446%39%
48964
TransparencyDay
45%6%13%21%11%1
48976
Night
44%5%12%22%13%1
48791
SeeingDay
16%6%27%30%14%4
6448
Night
18%8%27%29%13%1
16650

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%28%
1552
16th to endDay
12%16%7%8%6%25%447%24%
1680
February1st to 15thDay
14%14%6%7%6%35%445%27%
1789
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%435%5%6%10%42%
2385
16th to endDay
9%5%146%35%5%7%9%41%
2292
September1st to 15thDay
12%5%134345%5%6%48%
2135
16th to endDay
10%425%435%5%6%8%43%
1980
October1st to 15thDay
17%6%25%443445%41%
1900
16th to endDay
17%8%36%5%44446%35%
1768
November1st to 15thDay
15%8%36%5%2435%6%39%
1717
16th to endDay
16%9%36%5%34326%38%
1719
December1st to 15thDay
16%13%47%5%34447%28%
1560
16th to endDay
21%15%5%8%6%33336%22%
1664
January1st to 15thNight
17%10%46%5%24335%35%
2716
16th to endNight
13%12%7%9%5%24337%30%
2895
February1st to 15thNight
15%13%35%5%3435%5%34%
2370
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%5%9%53%
1569
16th to endNight
9%32442435%8%52%
1910
September1st to 15thNight
10%413424446%55%
1812
16th to endNight
9%5%2442445%7%50%
1980
October1st to 15thNight
14%5%24423346%47%
2058
16th to endNight
20%7%24423345%40%
2454
November1st to 15thNight
13%8%25%424436%43%
2471
16th to endNight
16%8%36%5%24345%38%
2568
December1st to 15thNight
20%10%36%5%24446%31%
2730
16th to endNight
22%15%47%5%35%445%22%
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
15%11%5%8%435%45%7%28%
1552
16th to endDay
12%16%7%10%6%25%347%24%
1680
February1st to 15thDay
14%14%6%8%5%35%445%27%
1789
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%45%
2385
16th to endDay
9%424435%47%8%42%
2292
September1st to 15thDay
13%41333445%7%48%
2135
16th to endDay
9%5%244345%7%9%43%
1980
October1st to 15thDay
17%6%2443435%5%41%
1900
16th to endDay
17%8%36%5%34446%36%
1768
November1st to 15thDay
15%8%36%5%2435%7%38%
1717
16th to endDay
16%9%35%434426%38%
1719
December1st to 15thDay
16%12%5%6%5%35%45%6%27%
1560
16th to endDay
21%15%6%7%6%33345%23%
1664
January1st to 15thNight
17%10%47%424345%34%
2716
16th to endNight
13%12%7%8%5%33347%29%
2895
February1st to 15thNight
15%12%45%5%24345%35%
2363
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%3134246%5%8%54%
1569
16th to endNight
9%41342435%8%52%
1910
September1st to 15thNight
11%3135%23447%54%
1812
16th to endNight
9%5%14425%35%7%50%
1980
October1st to 15thNight
15%5%235%23346%46%
2058
16th to endNight
20%7%25%423345%40%
2454
November1st to 15thNight
14%8%25%424445%43%
2471
16th to endNight
16%8%35%5%23446%38%
2568
December1st to 15thNight
20%10%36%5%2445%5%30%
2730
16th to endNight
23%15%46%5%35%34422%
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
54%6%15%15%7%
1553
16th to endDay
59%5%13%15%6%
1680
February1st to 15thDay
58%5%10%16%8%1
1791
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
2370
16th to endDay
35%7%14%23%16%2
2292
September1st to 15thDay
34%5%12%24%19%3
2135
16th to endDay
35%6%13%27%16%1
1980
October1st to 15thDay
43%5%11%23%13%2
1900
16th to endDay
49%412%22%9%1
1768
November1st to 15thDay
46%412%22%13%2
1717
16th to endDay
48%5%15%23%7%
1719
December1st to 15thDay
55%417%16%5%
1560
16th to endDay
63%6%12%12%5%
1664
January1st to 15thNight
52%413%18%10%
2716
16th to endNight
55%415%16%7%
2895
February1st to 15thNight
51%412%19%11%
2372
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%29%19%2
1560
16th to endNight
30%5%13%28%17%4
1910
September1st to 15thNight
30%49%26%24%2
1812
16th to endNight
32%5%10%30%18%1
1980
October1st to 15thNight
37%410%26%18%1
2058
16th to endNight
45%412%24%11%1
2454
November1st to 15thNight
42%410%23%15%3
2471
16th to endNight
47%415%23%8%
2568
December1st to 15thNight
53%5%14%17%7%
2730
16th to endNight
64%411%13%5%
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
21%9%34%30%2
135
16th to endDay
17%8%40%27%6%
144
February1st to 15thDay
26%14%45%13%
130
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%
391
16th to endDay
10%417%34%21%11%
332
September1st to 15thDay
12%316%33%24%9%
315
16th to endDay
10%418%31%27%7%
314
October1st to 15thDay
24%5%20%31%15%2
235
16th to endDay
24%13%31%26%4
144
November1st to 15thDay
16%11%28%25%15%2
135
16th to endDay
21%14%42%17%4
135
December1st to 15thDay
14%26%34%18%5%
135
16th to endDay
27%20%45%42
144
January1st to 15thNight
22%14%37%20%4
975
16th to endNight
19%13%37%26%2
1040
February1st to 15thNight
21%9%38%24%5%
852
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
5%9%43%33%6%
539
16th to endNight
10%215%33%32%5%
573
September1st to 15thNight
12%415%31%28%6%
552
16th to endNight
12%418%30%29%4
717
October1st to 15thNight
18%7%22%30%18%1
720
16th to endNight
23%12%30%23%8%
768
November1st to 15thNight
19%10%34%22%11%
760
16th to endNight
20%16%33%23%6%
813
December1st to 15thNight
26%14%33%21%4
975
16th to endNight
30%13%32%21%1
1040
Page generated at 2018-02-15 09:58:45. Version ac04

Copyright 2018 A. Danko


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