McKim Alpena County Observation Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the McKim Alpena County Observation Site clear sky chart from 2005-11-06 to 2024-01-16.

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
29%
23976
13%
75006
7%
23919
35%
23919
17%
54223

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 10thNight
15%
950
7%
2648
2%
946
19%
946
9%
2181
January11th to 20thNight
15%
930
7%
2603
2%
930
20%
930
8%
2186
January21st to endNight
18%
972
8%
2754
2%
972
23%
972
10%
2230
February1st to 10thNight
12%
720
9%
2340
4%
720
19%
720
10%
1839
February11th to 20thNight
19%
700
11%
2180
3%
699
27%
699
11%
1665
February21st to endNight
16%
592
11%
1776
2%
592
24%
592
10%
1385
March1st to 10thNight
22%
720
17%
2150
8%
720
30%
720
18%
1481
March11th to 20thNight
23%
720
18%
1979
7%
720
31%
720
19%
1400
March21st to endNight
25%
792
16%
2178
8%
792
32%
792
20%
1540
April1st to 10thNight
22%
572
14%
1832
5%
572
30%
572
16%
1296
April11th to 20thNight
31%
533
20%
1615
11%
533
40%
533
21%
1092
April21st to endNight
33%
540
15%
1620
7%
540
39%
540
19%
1147
May1st to 10thNight
31%
540
14%
1620
7%
540
38%
540
21%
1105
May11th to 20thNight
36%
531
17%
1592
11%
531
44%
531
23%
1050
May21st to endNight
46%
476
16%
1469
10%
475
55%
475
31%
870
June1st to 10thNight
41%
360
16%
1260
11%
360
50%
360
25%
767
June11th to 20thNight
42%
360
15%
1260
12%
360
49%
360
25%
746
June21st to endNight
47%
360
16%
1260
13%
360
53%
360
26%
752
July1st to 10thNight
57%
419
18%
1294
12%
419
64%
419
41%
682
July11th to 20thNight
55%
522
17%
1392
11%
522
60%
522
35%
858
July21st to endNight
56%
591
17%
1495
12%
558
59%
558
38%
906
August1st to 10thNight
56%
537
18%
1600
13%
534
61%
534
35%
919
August11th to 20thNight
61%
534
20%
1598
15%
534
66%
534
37%
913
August21st to endNight
52%
594
19%
1782
13%
594
57%
594
29%
1097
September1st to 10thNight
51%
609
18%
1869
13%
609
55%
609
30%
1126
September11th to 20thNight
47%
720
23%
1980
15%
720
53%
720
34%
1226
September21st to endNight
42%
720
17%
1980
12%
720
46%
720
25%
1353
October1st to 10thNight
37%
720
17%
2033
12%
720
43%
720
24%
1378
October11th to 20thNight
23%
720
13%
2177
6%
720
32%
720
16%
1595
October21st to endNight
20%
792
12%
2574
8%
792
27%
792
12%
1961
November1st to 10thNight
25%
740
16%
2406
10%
740
34%
740
17%
1666
November11th to 20thNight
20%
760
12%
2520
8%
760
27%
760
11%
1877
November21st to endNight
15%
760
8%
2660
3%
760
22%
760
10%
2062
December1st to 10thNight
16%
880
7%
2780
2%
880
21%
880
9%
2236
December11th to 20thNight
13%
950
5%
3511
1%
949
17%
949
5%
2910
December21st to endNight
10%
1040
3%
5219
1%
1026
14%
1026
3%
4726

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%10%48%7%45%5%5%7%31%
74598
Night
14%11%5%8%6%35%5%5%6%31%
75208
TransparencyDay
51%7%12%19%11%1
74304
Night
52%7%12%19%9%1
75037
SeeingDay
20%16%32%21%8%3
14341
Night
19%13%32%26%9%1
23985

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 10thDay
15%14%7%13%8%5%5%6%46%17%
1517
11th to 20thDay
15%16%7%13%11%5%6%5%5%413%
1480
21st to endDay
13%15%9%14%10%5%6%36%414%
1602
February1st to 10thDay
12%15%7%10%13%6%5%5%45%17%
1620
11th to 20thDay
12%14%6%13%9%36%446%23%
1665
21st to endDay
11%17%7%11%9%46%445%21%
1480
March1st to 10thDay
13%12%5%10%9%45%45%6%27%
1807
11th to 20thDay
12%12%5%7%7%45%45%7%32%
1980
21st to endDay
17%12%47%6%35%5%5%6%31%
2178
April1st to 10thDay
18%15%5%7%6%3445%6%28%
2142
11th to 20thDay
19%12%36%5%3445%6%33%
2294
21st to endDay
16%12%38%6%345%47%33%
2340
May1st to 10thDay
16%8%47%6%36%5%5%7%34%
2340
11th to 20thDay
17%7%36%5%35%5%5%7%36%
2301
21st to endDay
11%5%35%5%45%5%6%8%43%
2801
June1st to 10thDay
13%5%37%5%45%5%5%8%40%
2700
11th to 20thDay
12%6%26%6%35%6%6%9%40%
2700
21st to endDay
13%7%36%7%36%5%5%8%39%
2700
July1st to 10thDay
9%426%5%45%5%6%10%46%
2623
11th to 20thDay
12%5%36%5%36%5%7%8%39%
2520
21st to endDay
9%5%36%6%46%5%7%9%39%
2735
August1st to 10thDay
11%6%26%7%45%5%8%9%37%
2327
11th to 20thDay
10%5%27%6%35%6%6%9%41%
2303
21st to endDay
13%6%36%5%35%46%7%40%
2572
September1st to 10thDay
12%7%36%5%35%6%6%8%39%
2072
11th to 20thDay
13%6%25%5%35%5%6%7%45%
1980
21st to endDay
18%7%36%5%35%5%6%8%34%
1980
October1st to 10thDay
17%9%37%6%35%45%7%35%
1926
11th to 20thDay
23%11%5%7%8%45%5%5%5%24%
1782
21st to endDay
22%14%49%7%445%5%7%18%
1782
November1st to 10thDay
12%15%5%7%7%45%6%5%7%29%
1672
11th to 20thDay
13%15%5%10%7%46%5%6%6%23%
1658
21st to endDay
18%16%7%9%7%4445%6%20%
1520
December1st to 10thDay
13%18%8%13%8%46%45%6%17%
1397
11th to 20thDay
13%17%8%12%8%45%6%46%17%
1671
21st to endDay
24%25%9%13%7%343337%
2431
January1st to 10thNight
14%13%6%13%10%46%6%5%6%16%
2648
11th to 20thNight
16%15%7%13%9%46%45%5%17%
2603
21st to endNight
11%15%7%12%9%5%7%5%5%6%17%
2754
February1st to 10thNight
10%16%6%10%11%5%7%5%5%6%19%
2340
11th to 20thNight
12%13%5%10%9%46%5%5%7%23%
2180
21st to endNight
15%16%7%12%7%3445%5%23%
1776
March1st to 10thNight
10%12%5%9%6%35%45%6%36%
2139
11th to 20thNight
13%11%5%6%6%445%46%36%
1979
21st to endNight
17%11%46%5%25%45%7%36%
2178
April1st to 10thNight
17%12%46%5%235%6%6%32%
1832
11th to 20thNight
18%9%35%5%35%46%6%36%
1615
21st to endNight
14%11%46%5%4445%6%35%
1620
May1st to 10thNight
12%8%36%8%35%6%6%8%35%
1620
11th to 20thNight
16%9%25%5%25%6%6%7%38%
1592
21st to endNight
11%5%14435%5%5%9%48%
1468
June1st to 10thNight
12%6%25%5%35%6%6%7%44%
1260
11th to 20thNight
9%5%25%5%45%6%8%9%43%
1260
21st to endNight
10%6%25%5%3445%8%47%
1260
July1st to 10thNight
6%3244345%7%9%54%
1333
11th to 20thNight
6%425%5%45%5%6%9%48%
1440
21st to endNight
9%4245%245%6%8%51%
1583
August1st to 10thNight
7%5%34435%5%6%9%51%
1611
11th to 20thNight
9%41433446%8%53%
1598
21st to endNight
11%7%25%435%36%8%47%
1782
September1st to 10thNight
9%6%25%5%35%5%5%7%48%
1869
11th to 20thNight
12%5%25%5%3445%7%48%
1980
21st to endNight
17%6%26%6%3446%6%40%
1980
October1st to 10thNight
17%7%36%5%3445%5%41%
2033
11th to 20thNight
19%11%47%6%35%446%31%
2177
21st to endNight
24%12%47%6%35%446%26%
2574
November1st to 10thNight
12%11%48%6%35%5%6%8%32%
2406
11th to 20thNight
13%13%5%9%7%46%6%5%7%24%
2520
21st to endNight
17%16%6%8%7%35%5%47%22%
2660
December1st to 10thNight
14%15%7%12%7%46%5%5%6%19%
2780
11th to 20thNight
13%17%6%13%10%46%6%5%5%15%
3526
21st to endNight
23%25%9%11%6%443339%
5232

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 10thDay
66%7%12%12%4
1518
11th to 20thDay
73%7%8%10%2
1480
21st to endDay
73%49%9%4
1602
February1st to 10thDay
69%6%9%14%3
1620
11th to 20thDay
61%6%10%12%9%1
1674
21st to endDay
64%6%9%13%7%1
1480
March1st to 10thDay
57%5%12%16%8%2
1809
11th to 20thDay
51%6%11%20%8%3
1980
21st to endDay
53%6%10%19%10%1
2178
April1st to 10thDay
58%6%10%15%10%1
2142
11th to 20thDay
51%5%10%17%15%1
2294
21st to endDay
51%6%12%15%14%3
2340
May1st to 10thDay
48%6%10%21%12%3
2340
11th to 20thDay
46%7%9%20%15%3
2305
21st to endDay
38%7%14%23%15%2
2801
June1st to 10thDay
40%7%12%24%15%3
2700
11th to 20thDay
40%7%11%22%18%2
2700
21st to endDay
42%7%13%22%14%2
2700
July1st to 10thDay
34%7%13%25%20%2
2553
11th to 20thDay
38%9%12%23%16%2
2445
21st to endDay
39%8%14%21%16%2
2583
August1st to 10thDay
41%9%15%23%12%1
2314
11th to 20thDay
38%8%15%23%14%2
2303
21st to endDay
41%7%13%24%13%1
2572
September1st to 10thDay
41%7%12%24%15%1
2072
11th to 20thDay
37%7%13%30%12%1
1980
21st to endDay
47%8%14%23%9%
1980
October1st to 10thDay
49%6%11%22%11%1
1926
11th to 20thDay
60%7%11%17%5%
1782
21st to endDay
64%7%11%12%5%
1782
November1st to 10thDay
54%7%12%19%8%
1672
11th to 20thDay
59%7%15%14%5%
1658
21st to endDay
65%7%14%10%31
1520
December1st to 10thDay
67%7%12%11%2
1397
11th to 20thDay
67%7%12%12%2
1671
21st to endDay
84%5%5%42
2431
January1st to 10thNight
65%7%12%11%4
2648
11th to 20thNight
69%6%10%10%5%
2603
21st to endNight
65%6%13%12%4
2754
February1st to 10thNight
64%5%11%14%5%1
2340
11th to 20thNight
59%6%11%17%5%1
2182
21st to endNight
63%5%11%15%7%
1776
March1st to 10thNight
49%5%12%22%11%1
2150
11th to 20thNight
49%6%11%21%10%2
1980
21st to endNight
48%6%11%20%13%2
2178
April1st to 10thNight
52%6%9%19%13%1
1832
11th to 20thNight
46%5%9%24%14%2
1615
21st to endNight
49%7%10%17%15%3
1620
May1st to 10thNight
45%8%13%19%13%3
1620
11th to 20thNight
43%6%9%22%16%3
1593
21st to endNight
33%7%16%25%15%4
1469
June1st to 10thNight
37%7%13%26%15%1
1260
11th to 20thNight
33%9%14%25%17%2
1260
21st to endNight
35%8%12%26%16%3
1260
July1st to 10thNight
24%7%17%29%21%2
1294
11th to 20thNight
30%9%13%30%17%1
1392
21st to endNight
30%7%19%26%17%1
1495
August1st to 10thNight
29%8%19%30%13%1
1600
11th to 20thNight
28%7%18%32%15%1
1598
21st to endNight
35%7%16%26%14%2
1782
September1st to 10thNight
33%9%13%27%17%2
1869
11th to 20thNight
35%5%15%33%11%
1980
21st to endNight
43%7%16%26%8%
1980
October1st to 10thNight
44%6%13%24%12%1
2033
11th to 20thNight
54%6%13%20%6%1
2177
21st to endNight
59%6%11%18%6%
2574
November1st to 10thNight
48%8%15%22%7%1
2406
11th to 20thNight
57%7%14%16%5%
2520
21st to endNight
61%7%15%13%3
2660
December1st to 10thNight
63%8%13%13%3
2780
11th to 20thNight
67%9%12%9%3
3525
21st to endNight
79%7%6%5%2
5232

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 10thDay
24%19%39%15%4
270
11th to 20thDay
20%25%36%17%2
255
21st to endDay
29%16%36%11%6%1
264
February1st to 10thDay
29%28%31%10%2
240
11th to 20thDay
28%33%31%7%1
240
21st to endDay
35%25%33%6%1
198
March1st to 10thDay
28%24%34%10%2
249
11th to 20thDay
23%17%38%14%7%1
420
21st to endDay
31%15%29%20%5%
462
April1st to 10thDay
25%19%32%19%5%1
420
11th to 20thDay
31%18%27%12%9%2
412
21st to endDay
24%17%34%15%7%2
420
May1st to 10thDay
24%20%30%15%7%4
423
11th to 20thDay
19%17%31%21%9%4
447
21st to endDay
14%13%36%26%8%4
653
June1st to 10thDay
14%18%36%23%8%2
630
11th to 20thDay
15%15%35%25%7%2
630
21st to endDay
16%13%37%26%7%2
630
July1st to 10thDay
10%10%34%30%13%3
621
11th to 20thDay
11%14%33%27%10%5%
618
21st to endDay
12%8%38%26%11%5%
676
August1st to 10thDay
12%8%26%28%16%9%
446
11th to 20thDay
12%6%23%30%16%12%
439
21st to endDay
18%7%29%28%14%4
495
September1st to 10thDay
16%12%29%24%12%8%
450
11th to 20thDay
13%10%22%32%14%7%
450
21st to endDay
21%13%23%23%13%6%
450
October1st to 10thDay
23%16%27%18%14%2
450
11th to 20thDay
28%20%31%16%5%1
432
21st to endDay
32%22%32%11%2
297
November1st to 10thDay
24%20%36%15%5%
270
11th to 20thDay
24%26%34%12%31
246
21st to endDay
28%20%36%14%2
180
December1st to 10thDay
29%16%39%11%5%1
180
11th to 20thDay
26%24%38%9%2
180
21st to endDay
30%27%27%13%21
198
January1st to 10thNight
20%19%36%20%4
950
11th to 20thNight
22%18%34%20%6%
930
21st to endNight
18%14%36%25%6%1
972
February1st to 10thNight
19%20%38%20%3
720
11th to 20thNight
21%20%31%23%4
703
21st to endNight
26%18%33%20%3
592
March1st to 10thNight
19%16%36%23%6%
720
11th to 20thNight
20%18%35%22%6%
720
21st to endNight
22%13%33%24%6%1
792
April1st to 10thNight
25%14%36%20%5%1
572
11th to 20thNight
24%13%29%27%6%2
533
21st to endNight
18%13%32%30%7%1
540
May1st to 10thNight
14%10%38%29%8%1
540
11th to 20thNight
19%10%28%33%9%1
531
21st to endNight
13%8%30%35%14%
477
June1st to 10thNight
14%8%31%38%9%
360
11th to 20thNight
9%10%33%34%13%1
360
21st to endNight
11%9%27%39%14%1
360
July1st to 10thNight
6%429%45%15%1
419
11th to 20thNight
9%426%38%21%3
522
21st to endNight
10%5%23%42%18%1
591
August1st to 10thNight
8%226%40%23%1
537
11th to 20thNight
11%321%33%28%4
534
21st to endNight
16%5%21%36%20%2
594
September1st to 10thNight
12%5%26%34%19%4
609
11th to 20thNight
14%6%28%32%17%4
720
21st to endNight
20%9%23%28%17%3
720
October1st to 10thNight
20%10%28%29%12%1
720
11th to 20thNight
25%13%34%21%7%
720
21st to endNight
30%13%31%20%41
792
November1st to 10thNight
19%15%37%21%7%1
740
11th to 20thNight
22%19%33%21%5%
760
21st to endNight
25%15%40%17%4
760
December1st to 10thNight
22%19%35%20%4
880
11th to 20thNight
23%19%36%17%41
950
21st to endNight
28%16%37%17%3
1045
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