Kresge Environmental Education Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kresge Environmental Education Center clear sky chart from 2005-11-05 to 2017-12-02.

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%
15873
15%
47784
9%
15832
41%
15832
20%
33161

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
16%
899
10%
2506
3%
895
22%
895
13%
1981
January16th to endNight
20%
861
9%
2589
3%
861
25%
861
12%
2035
February1st to 15thNight
17%
701
10%
2276
2%
701
24%
701
10%
1763
February16th to endNight
24%
631
14%
1893
6%
631
33%
631
14%
1409
March1st to 15thNight
26%
720
15%
2071
8%
720
32%
720
17%
1502
March16th to endNight
34%
768
18%
2112
10%
768
41%
768
22%
1485
April1st to 15thNight
26%
596
14%
1806
7%
596
34%
596
19%
1262
April16th to endNight
34%
540
19%
1620
7%
540
44%
540
26%
1053
May1st to 15thNight
37%
540
15%
1620
7%
540
44%
540
23%
1099
May16th to endNight
47%
562
16%
1669
11%
561
53%
561
29%
1027
June1st to 15thNight
52%
360
16%
1260
16%
360
58%
360
27%
744
June16th to endNight
54%
377
17%
1277
17%
377
60%
377
30%
729
July1st to 15thNight
65%
510
16%
1360
14%
510
67%
510
41%
806
July16th to endNight
66%
564
16%
1497
14%
531
68%
531
37%
879
August1st to 15thNight
66%
539
18%
1609
15%
536
68%
536
35%
955
August16th to endNight
61%
573
23%
1719
17%
573
66%
573
36%
994
September1st to 15thNight
58%
672
22%
1931
17%
672
61%
672
32%
1182
September16th to endNight
59%
717
23%
1980
17%
717
62%
717
33%
1239
October1st to 15thNight
43%
720
18%
2081
14%
720
48%
720
25%
1389
October16th to endNight
24%
768
15%
2403
8%
768
33%
768
15%
1746
November1st to 15thNight
33%
760
19%
2471
15%
760
40%
760
20%
1647
November16th to endNight
23%
780
13%
2649
8%
780
30%
780
14%
1916
December1st to 15thNight
15%
755
7%
2573
3%
755
21%
755
10%
1996
December16th to endNight
13%
960
7%
2812
1%
960
19%
960
9%
2323

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%9%47%6%35%45%7%32%
48649
Night
15%9%46%5%3445%6%35%
47962
Cloud CoverDay
14%9%47%6%35%45%7%32%
48659
Night
15%8%46%5%3445%6%35%
47966
TransparencyDay
50%6%12%19%10%1
48345
Night
48%5%12%20%11%1
47784
SeeingDay
17%8%27%23%15%7%
6092
Night
18%9%29%29%11%1
15878

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
17%15%7%9%7%45%445%18%
1432
16th to endDay
15%17%8%11%11%4444415%
1633
February1st to 15thDay
13%15%6%12%9%46%44418%
1583
16th to endDay
13%14%410%8%45%45%6%22%
1580
March1st to 15thDay
15%11%6%9%7%3435%6%27%
1877
16th to endDay
17%10%5%8%6%3444429%
2112
April1st to 15thDay
19%12%35%424347%30%
2153
16th to endDay
16%7%26%5%24447%36%
2340
May1st to 15thDay
19%6%36%5%25%447%34%
2331
16th to endDay
14%5%26%435%45%7%39%
2443
June1st to 15thDay
10%6%35%5%35%5%6%8%39%
2697
16th to endDay
10%5%36%6%35%5%7%9%36%
2679
July1st to 15thDay
7%426%6%36%5%6%8%42%
2520
16th to endDay
9%5%245%36%6%7%10%38%
2567
August1st to 15thDay
9%5%35%6%46%5%7%9%35%
2340
16th to endDay
11%5%35%6%35%5%5%8%40%
2483
September1st to 15thDay
11%5%26%5%35%5%6%8%37%
2016
16th to endDay
13%5%245%25%5%5%9%39%
1980
October1st to 15thDay
16%8%37%5%245%46%36%
1878
16th to endDay
20%11%36%6%23345%30%
1820
November1st to 15thDay
16%10%46%5%3445%6%33%
1717
16th to endDay
16%14%5%8%6%35%347%24%
1638
December1st to 15thDay
15%15%7%11%6%35%44321%
1421
16th to endDay
19%15%9%11%5%23345%17%
1409
January1st to 15thNight
22%12%6%6%6%34345%23%
2506
16th to endNight
12%13%8%9%8%35%45%5%22%
2589
February1st to 15thNight
14%15%5%8%6%45%45%425%
2274
16th to endNight
16%11%49%6%35%5%45%27%
1893
March1st to 15thNight
16%10%47%434336%33%
2059
16th to endNight
16%8%35%5%2445%6%35%
2112
April1st to 15thNight
20%8%35%42335%7%33%
1806
16th to endNight
15%6%26%4235%5%6%40%
1620
May1st to 15thNight
15%6%25%6%35%448%36%
1620
16th to endNight
12%5%15%425%45%7%44%
1667
June1st to 15thNight
9%5%343346%7%8%44%
1260
16th to endNight
9%4244345%6%9%45%
1277
July1st to 15thNight
7%3245%1445%8%52%
1440
16th to endNight
6%324435%5%7%8%50%
1600
August1st to 15thNight
7%415%4345%7%8%46%
1620
16th to endNight
9%424323448%52%
1719
September1st to 15thNight
11%5%14424446%48%
1931
16th to endNight
10%6%25%424447%47%
1980
October1st to 15thNight
15%7%25%433446%40%
2081
16th to endNight
21%8%37%6%2445%5%30%
2403
November1st to 15thNight
15%8%35%434446%37%
2471
16th to endNight
19%11%46%6%25%45%7%26%
2649
December1st to 15thNight
19%13%6%8%6%34345%23%
2573
16th to endNight
19%15%7%11%7%2444418%
2812

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
17%15%7%9%8%35%445%18%
1432
16th to endDay
14%17%7%12%10%5%5%34415%
1633
February1st to 15thDay
13%15%6%11%9%5%6%445%17%
1583
16th to endDay
12%14%5%10%8%45%347%23%
1580
March1st to 15thDay
15%11%6%8%7%35%346%27%
1888
16th to endDay
16%11%5%8%6%35%43429%
2111
April1st to 15thDay
18%11%5%5%42335%6%31%
2153
16th to endDay
16%8%35%5%24447%36%
2340
May1st to 15thDay
19%7%36%42445%6%35%
2331
16th to endDay
14%5%25%5%345%48%38%
2443
June1st to 15thDay
10%6%25%5%35%5%6%8%39%
2697
16th to endDay
10%5%36%5%45%5%7%9%36%
2679
July1st to 15thDay
7%5%25%6%35%5%6%7%43%
2520
16th to endDay
8%4245%46%5%7%9%39%
2567
August1st to 15thDay
9%6%25%6%45%6%7%9%36%
2340
16th to endDay
12%5%25%5%45%5%5%8%40%
2483
September1st to 15thDay
11%5%25%6%45%5%6%9%37%
2016
16th to endDay
12%6%25%5%345%5%8%39%
1980
October1st to 15thDay
16%8%36%5%24446%37%
1878
16th to endDay
20%10%36%5%33345%30%
1820
November1st to 15thDay
16%9%46%6%33446%33%
1717
16th to endDay
15%13%5%8%7%34446%25%
1638
December1st to 15thDay
14%15%7%11%6%3444421%
1421
16th to endDay
19%16%9%10%6%24346%17%
1409
January1st to 15thNight
22%11%6%7%6%3434424%
2506
16th to endNight
12%13%8%8%8%46%446%22%
2589
February1st to 15thNight
14%14%5%8%6%36%45%5%25%
2267
16th to endNight
16%11%38%6%35%446%27%
1893
March1st to 15thNight
16%10%47%5%24346%33%
2071
16th to endNight
16%8%35%5%345%46%36%
2112
April1st to 15thNight
20%8%35%43336%6%33%
1806
16th to endNight
14%7%26%42445%7%40%
1620
May1st to 15thNight
15%5%26%6%35%449%35%
1619
16th to endNight
12%5%15%425%447%45%
1667
June1st to 15thNight
9%435%3345%6%9%44%
1260
16th to endNight
8%5%144335%6%9%46%
1277
July1st to 15thNight
7%32442345%8%53%
1440
16th to endNight
6%324335%5%6%8%51%
1600
August1st to 15thNight
6%415%5%245%7%9%46%
1620
16th to endNight
9%42442345%8%51%
1719
September1st to 15thNight
11%4244345%46%49%
1931
16th to endNight
10%5%25%43435%6%48%
1980
October1st to 15thNight
16%6%25%5%2445%6%40%
2081
16th to endNight
21%8%37%5%3345%5%30%
2403
November1st to 15thNight
14%9%45%43445%6%37%
2471
16th to endNight
19%11%36%6%25%5%5%7%27%
2649
December1st to 15thNight
19%13%6%8%5%3435%5%23%
2573
16th to endNight
19%15%7%10%6%3434419%
2812

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
68%5%9%12%4
1433
16th to endDay
73%47%9%4
1633
February1st to 15thDay
67%5%8%12%5%
1585
16th to endDay
63%49%14%7%
1580
March1st to 15thDay
57%6%10%17%7%
1888
16th to endDay
57%410%18%7%1
2112
April1st to 15thDay
53%5%10%20%9%
2153
16th to endDay
46%5%15%16%13%1
2340
May1st to 15thDay
49%5%11%20%10%2
2331
16th to endDay
43%5%12%23%13%1
2447
June1st to 15thDay
40%7%13%23%14%1
2697
16th to endDay
41%9%12%20%15%
2679
July1st to 15thDay
36%6%10%26%17%2
2371
16th to endDay
38%8%14%20%15%2
2407
August1st to 15thDay
42%7%13%21%13%1
2327
16th to endDay
39%7%11%25%13%1
2483
September1st to 15thDay
40%6%15%24%11%1
2016
16th to endDay
40%5%13%27%12%
1980
October1st to 15thDay
47%5%11%21%12%1
1878
16th to endDay
55%414%18%6%
1820
November1st to 15thDay
51%5%11%22%9%
1717
16th to endDay
59%413%15%5%
1638
December1st to 15thDay
64%5%14%11%3
1421
16th to endDay
68%5%12%10%3
1409
January1st to 15thNight
63%311%14%7%
2506
16th to endNight
63%5%13%14%3
2589
February1st to 15thNight
60%6%9%15%7%
2276
16th to endNight
57%411%18%7%
1893
March1st to 15thNight
53%410%20%9%1
2071
16th to endNight
48%411%22%10%1
2112
April1st to 15thNight
50%412%18%13%
1806
16th to endNight
42%5%12%19%17%3
1620
May1st to 15thNight
46%5%11%21%12%3
1620
16th to endNight
38%412%24%15%4
1669
June1st to 15thNight
35%6%13%27%16%1
1260
16th to endNight
33%5%16%24%18%1
1277
July1st to 15thNight
29%410%31%21%2
1360
16th to endNight
28%7%17%23%20%1
1497
August1st to 15thNight
31%6%14%29%14%2
1609
16th to endNight
30%6%13%31%16%2
1719
September1st to 15thNight
34%6%11%29%17%1
1931
16th to endNight
36%5%11%30%15%
1980
October1st to 15thNight
43%5%11%22%16%
2081
16th to endNight
54%5%12%20%6%
2403
November1st to 15thNight
46%413%22%11%1
2471
16th to endNight
55%5%15%17%6%
2649
December1st to 15thNight
63%5%13%12%5%
2573
16th to endNight
69%410%11%4
2812

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%23%36%14%41
90
16th to endDay
35%7%39%15%2
96
February1st to 15thDay
24%20%42%12%1
90
16th to endDay
18%18%38%19%4
81
March1st to 15thDay
26%16%31%21%3
178
16th to endDay
24%6%32%22%11%2
288
April1st to 15thDay
25%12%27%22%9%1
270
16th to endDay
21%9%31%18%12%6%
270
May1st to 15thDay
22%9%25%26%11%3
288
16th to endDay
18%6%29%23%13%8%
343
June1st to 15thDay
12%7%31%29%14%4
495
16th to endDay
11%8%31%25%17%5%
495
July1st to 15thDay
9%424%32%18%10%
475
16th to endDay
9%326%28%22%10%
427
August1st to 15thDay
9%415%29%23%17%
313
16th to endDay
14%6%16%21%23%17%
332
September1st to 15thDay
10%220%24%21%20%
315
16th to endDay
14%5%14%22%28%14%
314
October1st to 15thDay
20%6%25%24%16%6%
315
16th to endDay
24%13%32%22%5%1
236
November1st to 15thDay
21%14%29%20%11%2
135
16th to endDay
26%24%30%12%5%
108
December1st to 15thDay
19%20%42%12%4
63
16th to endDay
28%28%40%4
75
January1st to 15thNight
27%13%34%19%41
900
16th to endNight
18%13%36%26%5%
861
February1st to 15thNight
21%15%36%21%3
704
16th to endNight
22%13%30%27%5%
631
March1st to 15thNight
22%12%32%25%6%
720
16th to endNight
18%10%28%31%9%1
768
April1st to 15thNight
23%10%34%25%5%
596
16th to endNight
17%8%36%27%8%2
540
May1st to 15thNight
19%5%30%34%9%1
540
16th to endNight
13%326%37%15%2
563
June1st to 15thNight
10%328%45%11%
360
16th to endNight
11%225%42%16%
377
July1st to 15thNight
8%217%43%24%3
510
16th to endNight
7%118%46%22%2
564
August1st to 15thNight
9%113%44%27%3
539
16th to endNight
9%219%34%30%3
573
September1st to 15thNight
12%419%32%23%6%
672
16th to endNight
13%417%34%26%4
717
October1st to 15thNight
19%6%24%31%16%1
720
16th to endNight
25%11%33%22%6%
768
November1st to 15thNight
20%10%30%25%12%
760
16th to endNight
23%15%31%21%6%
780
December1st to 15thNight
24%13%37%21%3
755
16th to endNight
26%13%36%21%2
960
Page generated at 2017-12-03 11:16:35. Version ac04

Copyright 2017 A. Danko


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