Rochester Hills
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rochester Hills clear sky chart from 2005-11-05 to 2017-09-15.

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
36%
15579
15%
46832
10%
15541
42%
15541
20%
32400

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
17%
896
10%
2506
4%
895
22%
895
12%
1999
January16th to endNight
21%
835
10%
2563
4%
835
26%
835
11%
1992
February1st to 15thNight
18%
701
9%
2273
2%
701
25%
701
10%
1752
February16th to endNight
23%
631
15%
1893
6%
631
33%
631
15%
1393
March1st to 15thNight
26%
720
15%
2067
9%
720
31%
720
17%
1511
March16th to endNight
33%
768
18%
2112
10%
768
40%
768
21%
1482
April1st to 15thNight
29%
603
14%
1813
7%
603
35%
603
19%
1269
April16th to endNight
35%
540
20%
1620
8%
540
45%
540
25%
1058
May1st to 15thNight
40%
540
15%
1620
10%
540
46%
540
22%
1114
May16th to endNight
48%
562
16%
1684
11%
561
55%
561
29%
1060
June1st to 15thNight
54%
390
17%
1303
16%
390
60%
390
28%
789
June16th to endNight
59%
411
19%
1311
18%
411
65%
411
31%
780
July1st to 15thNight
62%
510
16%
1360
14%
510
65%
510
40%
808
July16th to endNight
65%
564
19%
1517
15%
531
69%
531
39%
880
August1st to 15thNight
63%
539
19%
1609
14%
536
67%
536
35%
945
August16th to endNight
63%
573
23%
1719
17%
573
68%
573
36%
1002
September1st to 15thNight
57%
678
23%
1938
18%
678
61%
678
33%
1178
September16th to endNight
59%
657
23%
1815
18%
657
63%
657
34%
1119
October1st to 15thNight
45%
660
20%
1907
15%
660
52%
660
28%
1239
October16th to endNight
24%
704
14%
2192
8%
704
34%
704
16%
1567
November1st to 15thNight
36%
700
21%
2276
16%
700
45%
700
22%
1472
November16th to endNight
25%
720
14%
2427
9%
720
31%
720
14%
1738
December1st to 15thNight
17%
720
8%
2520
3%
720
24%
720
10%
1933
December16th to endNight
14%
957
7%
2787
2%
957
19%
957
9%
2320

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%47%6%35%5%5%7%32%
47873
Night
14%8%36%5%3445%6%36%
47012
Cloud CoverDay
13%8%47%6%35%5%5%7%32%
47883
Night
14%8%36%5%3445%6%36%
47016
TransparencyDay
49%6%11%19%11%1
47571
Night
47%6%11%21%11%1
46832
SeeingDay
16%9%27%24%15%7%
5800
Night
18%8%28%29%12%1
15587

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%13%5%11%8%5%45%5%5%17%
1432
16th to endDay
14%15%9%11%8%47%5%46%14%
1659
February1st to 15thDay
14%14%6%11%8%45%5%5%5%17%
1587
16th to endDay
12%15%410%9%35%436%22%
1580
March1st to 15thDay
16%10%5%7%7%35%446%26%
1882
16th to endDay
17%10%5%9%6%35%346%27%
2112
April1st to 15thDay
18%10%46%43445%6%31%
2145
16th to endDay
16%8%36%5%24346%37%
2340
May1st to 15thDay
18%7%37%6%4445%5%32%
2331
16th to endDay
12%6%25%5%35%45%8%39%
2431
June1st to 15thDay
9%5%35%6%45%5%5%8%40%
2648
16th to endDay
8%5%26%6%47%6%6%9%34%
2644
July1st to 15thDay
6%5%25%5%36%5%6%9%43%
2520
16th to endDay
7%5%25%5%46%7%7%10%36%
2545
August1st to 15thDay
8%5%26%6%46%6%6%9%37%
2340
16th to endDay
10%5%35%5%35%5%6%8%39%
2480
September1st to 15thDay
12%5%25%5%36%5%5%9%38%
1999
16th to endDay
12%5%25%5%25%5%5%9%38%
1815
October1st to 15thDay
13%7%345%34446%39%
1722
16th to endDay
20%11%26%434435%31%
1678
November1st to 15thDay
13%8%36%6%3435%6%37%
1582
16th to endDay
16%10%5%7%6%35%5%45%28%
1530
December1st to 15thDay
16%12%7%11%7%25%45%5%21%
1440
16th to endDay
20%15%8%9%7%4334417%
1431
January1st to 15thNight
21%11%47%7%45%44423%
2506
16th to endNight
12%13%7%9%8%36%5%46%23%
2563
February1st to 15thNight
14%13%5%7%7%35%445%26%
2271
16th to endNight
15%10%48%6%3445%6%28%
1893
March1st to 15thNight
16%9%36%7%24445%33%
2055
16th to endNight
15%6%36%5%35%5%46%36%
2112
April1st to 15thNight
18%8%35%5%245%5%6%34%
1813
16th to endNight
14%6%25%5%3345%8%40%
1620
May1st to 15thNight
16%6%36%5%25%5%5%8%35%
1620
16th to endNight
11%434435%447%45%
1682
June1st to 15thNight
8%425%5%26%46%8%45%
1303
16th to endNight
9%5%2432447%8%45%
1311
July1st to 15thNight
6%42342435%8%53%
1440
16th to endNight
5%3244245%6%10%52%
1622
August1st to 15thNight
5%3245%345%7%9%48%
1620
16th to endNight
9%5%14423347%52%
1719
September1st to 15thNight
10%5%2432435%6%50%
1938
16th to endNight
11%425%42435%8%48%
1815
October1st to 15thNight
15%6%245%23446%43%
1907
16th to endNight
19%8%36%6%345%5%5%31%
2192
November1st to 15thNight
13%6%35%4345%5%6%40%
2276
16th to endNight
19%10%46%5%345%46%28%
2427
December1st to 15thNight
20%12%5%7%5%245%5%5%24%
2520
16th to endNight
21%14%6%9%6%25%445%18%
2787

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%13%5%9%9%45%5%5%6%17%
1432
16th to endDay
14%15%9%11%8%46%5%46%13%
1659
February1st to 15thDay
14%14%5%11%7%5%5%5%5%6%18%
1587
16th to endDay
12%14%5%9%9%35%446%22%
1580
March1st to 15thDay
17%11%5%8%7%35%447%26%
1893
16th to endDay
18%10%48%7%25%446%27%
2111
April1st to 15thDay
18%10%46%43445%6%31%
2145
16th to endDay
16%8%36%5%3335%7%37%
2340
May1st to 15thDay
18%6%37%6%35%45%5%32%
2331
16th to endDay
13%5%25%5%35%449%38%
2431
June1st to 15thDay
9%5%35%6%35%5%5%8%40%
2648
16th to endDay
9%5%26%6%47%7%7%8%35%
2644
July1st to 15thDay
6%425%5%36%5%6%8%43%
2520
16th to endDay
7%5%25%5%37%7%7%10%37%
2545
August1st to 15thDay
8%5%26%7%46%6%7%10%36%
2340
16th to endDay
10%5%25%5%35%5%6%8%39%
2480
September1st to 15thDay
12%5%25%5%35%5%6%8%38%
1999
16th to endDay
12%5%25%5%345%7%9%38%
1815
October1st to 15thDay
13%6%35%5%345%47%39%
1722
16th to endDay
20%11%25%5%34435%31%
1678
November1st to 15thDay
13%8%35%5%3445%6%38%
1582
16th to endDay
16%10%5%8%6%35%445%28%
1530
December1st to 15thDay
15%12%7%10%7%2445%5%21%
1440
16th to endDay
20%15%8%9%7%34445%17%
1431
January1st to 15thNight
21%11%47%7%45%43424%
2506
16th to endNight
13%13%7%9%8%46%445%23%
2563
February1st to 15thNight
13%14%5%8%6%45%445%26%
2264
16th to endNight
15%10%47%7%34446%29%
1893
March1st to 15thNight
17%9%36%6%24445%33%
2067
16th to endNight
15%6%36%5%35%5%46%36%
2112
April1st to 15thNight
18%8%35%5%345%5%6%34%
1813
16th to endNight
15%6%245%3345%8%40%
1620
May1st to 15thNight
17%6%26%5%25%45%8%35%
1619
16th to endNight
11%5%34435%45%7%44%
1682
June1st to 15thNight
8%425%5%35%46%7%45%
1303
16th to endNight
9%5%244245%7%7%46%
1311
July1st to 15thNight
6%4135%2435%9%53%
1440
16th to endNight
5%3243245%6%10%51%
1622
August1st to 15thNight
5%4245%35%5%6%9%48%
1620
16th to endNight
9%414422446%53%
1719
September1st to 15thNight
10%5%33324447%50%
1938
16th to endNight
11%425%434348%48%
1815
October1st to 15thNight
15%6%24423446%44%
1907
16th to endNight
20%7%36%5%34445%31%
2192
November1st to 15thNight
13%7%25%4345%5%7%40%
2276
16th to endNight
20%10%36%5%345%5%5%29%
2427
December1st to 15thNight
20%12%6%7%5%35%446%24%
2520
16th to endNight
21%14%6%10%6%3444418%
2787

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
66%6%11%10%4
1433
16th to endDay
71%6%9%8%4
1659
February1st to 15thDay
65%6%7%13%5%
1589
16th to endDay
62%5%9%15%6%
1580
March1st to 15thDay
58%7%10%16%6%
1893
16th to endDay
56%5%9%19%6%1
2112
April1st to 15thDay
53%410%19%11%
2145
16th to endDay
47%413%17%15%2
2340
May1st to 15thDay
51%6%9%19%10%2
2331
16th to endDay
42%6%12%23%13%2
2435
June1st to 15thDay
40%7%12%24%14%1
2648
16th to endDay
42%8%12%19%15%1
2644
July1st to 15thDay
36%6%10%24%19%2
2371
16th to endDay
38%9%14%20%14%2
2387
August1st to 15thDay
39%9%12%24%12%1
2327
16th to endDay
39%7%11%23%15%1
2480
September1st to 15thDay
40%6%13%25%13%
1999
16th to endDay
39%6%12%28%12%
1815
October1st to 15thDay
42%5%13%22%13%1
1722
16th to endDay
54%5%14%17%7%
1678
November1st to 15thDay
45%6%11%23%11%1
1582
16th to endDay
56%5%12%18%6%
1530
December1st to 15thDay
64%5%12%13%4
1440
16th to endDay
70%410%10%3
1431
January1st to 15thNight
63%5%10%14%6%
2506
16th to endNight
62%5%12%14%4
2563
February1st to 15thNight
59%7%10%14%6%
2273
16th to endNight
55%5%11%19%7%
1893
March1st to 15thNight
52%6%9%19%10%1
2067
16th to endNight
47%5%11%23%10%1
2112
April1st to 15thNight
49%5%11%19%14%
1813
16th to endNight
41%5%10%20%17%3
1620
May1st to 15thNight
45%6%10%20%14%2
1620
16th to endNight
37%6%12%23%16%3
1684
June1st to 15thNight
35%7%12%27%16%1
1303
16th to endNight
33%7%13%24%19%1
1311
July1st to 15thNight
29%5%10%29%21%2
1360
16th to endNight
26%8%16%25%19%3
1517
August1st to 15thNight
29%7%13%31%14%2
1609
16th to endNight
31%5%13%29%18%2
1719
September1st to 15thNight
33%6%10%29%18%1
1938
16th to endNight
35%411%32%15%
1815
October1st to 15thNight
39%6%11%22%18%
1907
16th to endNight
52%5%13%20%7%
2192
November1st to 15thNight
42%7%11%25%12%1
2276
16th to endNight
54%413%19%6%
2427
December1st to 15thNight
61%6%12%14%5%
2520
16th to endNight
68%5%10%10%4
2787

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%18%40%15%31
90
16th to endDay
29%15%38%12%4
96
February1st to 15thDay
20%17%48%12%1
90
16th to endDay
16%20%43%16%3
81
March1st to 15thDay
28%15%29%19%7%
183
16th to endDay
25%11%29%23%7%2
288
April1st to 15thDay
20%15%30%21%10%2
270
16th to endDay
22%10%31%15%11%8%
270
May1st to 15thDay
22%9%28%21%13%4
288
16th to endDay
15%9%27%25%15%7%
331
June1st to 15thDay
13%8%30%29%13%3
479
16th to endDay
12%8%32%27%14%5%
495
July1st to 15thDay
9%425%32%18%9%
475
16th to endDay
7%425%30%21%11%
405
August1st to 15thDay
8%219%29%21%18%
313
16th to endDay
13%417%24%21%18%
332
September1st to 15thDay
11%321%23%25%15%
311
16th to endDay
17%215%25%27%11%
254
October1st to 15thDay
14%7%26%24%20%7%
255
16th to endDay
27%12%34%20%42
190
November1st to 15thDay
11%14%32%28%11%2
90
16th to endDay
20%25%32%17%5%
75
December1st to 15thDay
21%26%33%15%3
60
16th to endDay
25%30%35%7%1
79
January1st to 15thNight
26%14%33%20%41
900
16th to endNight
19%11%35%27%5%
835
February1st to 15thNight
21%15%35%23%3
704
16th to endNight
21%12%33%27%5%
631
March1st to 15thNight
21%11%34%26%6%
720
16th to endNight
17%12%30%28%9%1
768
April1st to 15thNight
22%11%30%29%4
603
16th to endNight
18%6%33%29%10%1
540
May1st to 15thNight
19%5%27%34%11%1
540
16th to endNight
14%225%37%17%2
563
June1st to 15thNight
9%327%45%13%
390
16th to endNight
12%120%48%16%
411
July1st to 15thNight
8%120%41%25%3
510
16th to endNight
5%219%46%23%2
564
August1st to 15thNight
7%118%36%31%4
539
16th to endNight
11%116%34%32%3
573
September1st to 15thNight
12%418%31%25%6%
678
16th to endNight
13%416%33%26%5%
657
October1st to 15thNight
18%5%24%30%18%2
660
16th to endNight
25%12%32%24%4
704
November1st to 15thNight
18%10%29%24%14%1
700
16th to endNight
25%14%28%22%8%
720
December1st to 15thNight
27%12%35%19%5%
720
16th to endNight
29%11%36%20%3
957
Page generated at 2017-09-16 00:58:33. Version ac04

Copyright 2017 A. Danko


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