Copper Harbor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Copper Harbor clear sky chart from 2005-11-06 to 2024-01-15.

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
30%
24610
10%
74956
6%
24552
34%
24552
14%
56919

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
12%
950
3%
2648
1%
946
14%
946
5%
2377
January11th to 20thNight
14%
925
2%
2589
1%
925
15%
925
5%
2334
January21st to endNight
13%
990
3%
2772
1%
990
15%
990
4%
2541
February1st to 10thNight
19%
900
5%
2470
2%
900
21%
900
8%
2128
February11th to 20thNight
21%
787
8%
2182
4%
783
25%
783
11%
1799
February21st to endNight
21%
592
10%
1776
3%
592
28%
592
12%
1403
March1st to 10thNight
32%
717
14%
2160
9%
717
37%
717
18%
1543
March11th to 20thNight
31%
716
17%
2126
11%
716
37%
716
18%
1498
March21st to endNight
37%
594
18%
1980
15%
594
42%
594
17%
1367
April1st to 10thNight
32%
540
10%
1800
8%
540
38%
540
14%
1331
April11th to 20thNight
35%
533
14%
1739
11%
533
39%
533
18%
1235
April21st to endNight
39%
540
14%
1620
9%
540
43%
540
20%
1135
May1st to 10thNight
36%
540
13%
1472
9%
540
39%
540
21%
1067
May11th to 20thNight
40%
531
16%
1416
11%
531
43%
531
25%
997
May21st to endNight
49%
583
12%
1552
8%
582
51%
582
28%
1052
June1st to 10thNight
51%
456
11%
1356
7%
456
54%
456
27%
875
June11th to 20thNight
50%
360
10%
1260
9%
360
51%
360
21%
803
June21st to endNight
49%
447
10%
1347
7%
447
52%
447
27%
855
July1st to 10thNight
60%
525
13%
1400
8%
525
61%
525
39%
840
July11th to 20thNight
50%
522
13%
1392
7%
522
52%
522
35%
869
July21st to endNight
58%
591
17%
1487
11%
558
60%
558
39%
898
August1st to 10thNight
59%
537
18%
1423
13%
534
61%
534
36%
868
August11th to 20thNight
57%
534
20%
1506
13%
534
62%
534
36%
894
August21st to endNight
51%
594
18%
1961
16%
594
54%
594
29%
1125
September1st to 10thNight
52%
540
19%
1800
17%
540
57%
540
29%
1036
September11th to 20thNight
45%
620
17%
1880
13%
620
49%
620
26%
1196
September21st to endNight
39%
720
12%
1980
9%
720
41%
720
24%
1380
October1st to 10thNight
34%
720
14%
2071
9%
720
38%
720
20%
1462
October11th to 20thNight
26%
720
9%
2258
6%
720
30%
720
13%
1730
October21st to endNight
23%
792
8%
2574
4%
792
28%
792
10%
2045
November1st to 10thNight
23%
740
12%
2406
8%
740
30%
740
11%
1879
November11th to 20thNight
16%
867
7%
2577
3%
867
20%
867
7%
2174
November21st to endNight
16%
950
6%
2703
3%
950
19%
950
7%
2349
December1st to 10thNight
11%
950
3%
2850
1%
950
13%
950
4%
2538
December11th to 20thNight
13%
950
4%
3493
1%
948
15%
948
4%
3006
December21st to endNight
8%
1037
2%
4930
0%
1026
10%
1026
2%
4290

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%11%5%9%7%45%45%6%31%
74577
Night
13%12%6%11%9%45%5%5%5%26%
75202
TransparencyDay
54%412%21%9%1
74282
Night
60%411%18%7%1
75031
SeeingDay
18%11%31%26%11%3
14720
Night
20%10%28%28%12%1
24622

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
10%17%12%18%12%8%7%5%326%
1517
11th to 20thDay
12%17%8%15%15%9%9%3227%
1477
21st to endDay
11%14%8%17%14%9%7%5%438%
1584
February1st to 10thDay
8%13%6%14%17%9%10%5%4410%
1485
11th to 20thDay
7%12%8%13%12%9%8%5%45%18%
1664
21st to endDay
10%14%6%15%12%5%6%46%5%16%
1480
March1st to 10thDay
9%11%7%13%9%47%5%5%6%25%
1798
11th to 20thDay
11%9%6%10%8%43447%33%
1846
21st to endDay
15%10%6%10%7%46%5%46%27%
2376
April1st to 10thDay
13%12%5%8%7%45%5%6%6%29%
2160
11th to 20thDay
18%12%48%6%45%5%47%29%
2169
21st to endDay
16%10%45%6%4445%7%35%
2340
May1st to 10thDay
13%10%36%6%35%45%8%37%
2487
11th to 20thDay
13%8%37%5%35%45%7%40%
2479
21st to endDay
12%7%37%6%45%45%9%39%
2725
June1st to 10thDay
10%6%35%436%5%5%7%46%
2596
11th to 20thDay
12%5%25%6%35%5%6%8%43%
2700
21st to endDay
12%6%35%5%35%46%8%43%
2606
July1st to 10thDay
8%424435%45%9%52%
2520
11th to 20thDay
8%5%25%5%35%5%5%8%50%
2520
21st to endDay
8%42443445%9%53%
2743
August1st to 10thDay
8%425%4345%7%9%49%
2507
11th to 20thDay
11%7%245%345%5%7%48%
2395
21st to endDay
11%7%25%4345%5%8%46%
2394
September1st to 10thDay
13%7%35%5%3445%7%44%
2160
11th to 20thDay
14%7%35%6%36%5%6%8%38%
2062
21st to endDay
18%10%46%7%3445%7%32%
1980
October1st to 10thDay
16%12%38%6%445%5%6%30%
1886
11th to 20thDay
21%17%5%10%6%445%45%19%
1701
21st to endDay
20%19%7%11%7%4444416%
1782
November1st to 10thDay
16%21%6%10%6%35%5%45%19%
1672
11th to 20thDay
16%19%9%16%9%45%33312%
1601
21st to endDay
14%20%9%19%11%5%5%3338%
1473
December1st to 10thDay
10%18%12%23%13%45%4435%
1330
11th to 20thDay
15%16%9%18%16%5%5%4337%
1671
21st to endDay
20%20%10%17%9%35%3337%
2691
January1st to 10thNight
9%15%10%19%13%6%9%5%338%
2648
11th to 20thNight
12%14%8%16%17%8%8%4437%
2589
21st to endNight
11%14%9%17%16%9%8%5%435%
2772
February1st to 10thNight
9%13%6%13%15%9%10%5%3413%
2470
11th to 20thNight
11%10%6%12%12%8%9%6%45%16%
2181
21st to endNight
12%14%7%10%10%5%6%5%5%5%21%
1776
March1st to 10thNight
8%11%49%8%5%6%5%5%7%31%
2149
11th to 20thNight
10%11%48%8%45%446%34%
2126
21st to endNight
14%10%5%8%7%35%45%7%33%
1980
April1st to 10thNight
15%9%5%9%8%5%7%5%5%5%27%
1800
11th to 20thNight
19%11%35%7%36%45%6%32%
1739
21st to endNight
17%9%47%5%445%5%6%34%
1620
May1st to 10thNight
16%9%47%7%35%5%5%7%32%
1472
11th to 20thNight
15%8%37%7%246%6%6%36%
1416
21st to endNight
11%7%36%6%45%6%6%8%38%
1551
June1st to 10thNight
13%5%36%6%45%48%8%38%
1356
11th to 20thNight
12%7%36%6%37%6%7%9%35%
1260
21st to endNight
14%6%35%6%45%6%5%8%39%
1347
July1st to 10thNight
8%5%345%45%46%7%50%
1440
11th to 20thNight
10%5%36%5%346%7%8%43%
1440
21st to endNight
8%425%425%6%6%9%50%
1575
August1st to 10thNight
9%5%245%345%6%9%47%
1432
11th to 20thNight
9%5%35%5%345%5%7%49%
1506
21st to endNight
11%7%25%42345%7%48%
1961
September1st to 10thNight
11%6%25%5%3446%6%48%
1800
11th to 20thNight
11%7%35%7%35%5%6%7%41%
1880
21st to endNight
18%9%37%6%3345%7%35%
1980
October1st to 10thNight
17%9%37%5%4445%6%35%
2071
11th to 20thNight
17%14%49%7%35%5%6%6%24%
2258
21st to endNight
19%16%5%9%9%45%44421%
2574
November1st to 10thNight
15%18%7%9%6%46%445%21%
2406
11th to 20thNight
16%18%8%14%10%35%44415%
2577
21st to endNight
14%17%9%17%10%35%44412%
2703
December1st to 10thNight
10%18%11%23%13%433239%
2850
11th to 20thNight
11%16%9%17%14%5%5%5%4311%
3526
21st to endNight
18%21%10%16%10%45%3239%
4971

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
82%36%8%1
1518
11th to 20thDay
83%36%7%1
1477
21st to endDay
80%46%8%2
1584
February1st to 10thDay
74%411%10%1
1485
11th to 20thDay
69%39%14%4
1673
21st to endDay
67%5%7%12%8%1
1480
March1st to 10thDay
57%5%12%15%9%1
1800
11th to 20thDay
54%313%18%11%1
1846
21st to endDay
58%5%10%18%8%1
2376
April1st to 10thDay
53%6%10%22%9%1
2160
11th to 20thDay
57%48%21%9%2
2169
21st to endDay
50%49%22%13%2
2340
May1st to 10thDay
46%413%23%13%1
2487
11th to 20thDay
45%310%28%13%1
2483
21st to endDay
42%5%15%24%13%1
2725
June1st to 10thDay
38%317%28%13%1
2596
11th to 20thDay
39%415%26%14%1
2700
21st to endDay
39%416%29%12%1
2606
July1st to 10thDay
28%315%37%16%1
2451
11th to 20thDay
33%415%32%15%2
2445
21st to endDay
30%416%34%16%1
2591
August1st to 10thDay
31%5%19%33%11%1
2492
11th to 20thDay
37%5%18%29%11%
2395
21st to endDay
37%417%28%13%1
2394
September1st to 10thDay
40%414%33%9%
2160
11th to 20thDay
43%422%24%5%
2062
21st to endDay
51%316%24%6%
1980
October1st to 10thDay
56%312%23%6%
1886
11th to 20thDay
67%311%15%4
1701
21st to endDay
73%48%11%4
1782
November1st to 10thDay
68%310%14%5%
1672
11th to 20thDay
78%38%8%3
1601
21st to endDay
81%39%5%2
1473
December1st to 10thDay
82%39%6%1
1330
11th to 20thDay
85%26%5%2
1671
21st to endDay
83%25%9%1
2691
January1st to 10thNight
82%27%8%1
2648
11th to 20thNight
82%39%6%
2589
21st to endNight
83%45%6%1
2772
February1st to 10thNight
74%49%11%2
2470
11th to 20thNight
69%410%14%4
2182
21st to endNight
65%310%15%6%
1776
March1st to 10thNight
52%5%11%22%10%1
2160
11th to 20thNight
53%311%20%12%1
2127
21st to endNight
52%410%22%11%2
1980
April1st to 10thNight
58%5%8%19%10%
1800
11th to 20thNight
54%49%21%11%2
1739
21st to endNight
52%47%22%14%2
1620
May1st to 10thNight
52%411%19%12%2
1472
11th to 20thNight
48%47%26%13%1
1417
21st to endNight
43%5%12%25%14%1
1552
June1st to 10thNight
42%411%27%13%2
1356
11th to 20thNight
44%5%13%22%15%2
1260
21st to endNight
41%416%23%14%2
1347
July1st to 10thNight
32%412%34%16%2
1400
11th to 20thNight
36%415%28%16%1
1392
21st to endNight
31%416%31%15%2
1487
August1st to 10thNight
35%417%32%9%3
1423
11th to 20thNight
33%5%16%33%13%1
1506
21st to endNight
36%415%28%15%2
1961
September1st to 10thNight
37%414%33%12%1
1800
11th to 20thNight
42%418%30%6%
1880
21st to endNight
49%317%26%5%
1980
October1st to 10thNight
51%414%24%8%1
2071
11th to 20thNight
61%412%17%5%1
2258
21st to endNight
67%312%14%4
2574
November1st to 10thNight
65%410%16%6%
2406
11th to 20thNight
74%39%9%5%
2577
21st to endNight
75%410%8%2
2703
December1st to 10thNight
81%37%7%1
2850
11th to 20thNight
77%410%8%2
3525
21st to endNight
82%37%8%1
4971

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
17%15%40%21%6%1
270
11th to 20thDay
17%13%37%24%7%1
254
21st to endDay
23%11%45%18%3
264
February1st to 10thDay
20%23%39%16%2
240
11th to 20thDay
15%28%33%17%8%
240
21st to endDay
21%25%38%15%1
198
March1st to 10thDay
14%18%43%19%42
240
11th to 20thDay
16%18%33%25%7%1
268
21st to endDay
22%13%31%23%8%3
462
April1st to 10thDay
22%11%34%26%6%1
420
11th to 20thDay
30%11%24%24%8%2
412
21st to endDay
26%10%30%21%10%4
420
May1st to 10thDay
17%12%35%25%8%3
570
11th to 20thDay
17%8%37%25%10%4
625
21st to endDay
18%8%30%30%13%2
679
June1st to 10thDay
13%8%32%32%13%2
630
11th to 20thDay
17%8%30%30%13%3
630
21st to endDay
16%8%25%32%16%4
630
July1st to 10thDay
8%5%31%36%16%5%
621
11th to 20thDay
10%8%30%29%17%6%
618
21st to endDay
10%6%28%35%16%6%
684
August1st to 10thDay
12%8%26%32%18%4
626
11th to 20thDay
15%7%19%30%22%7%
531
21st to endDay
18%9%22%27%19%4
495
September1st to 10thDay
18%7%26%27%17%6%
450
11th to 20thDay
16%9%28%28%17%2
450
21st to endDay
25%10%25%24%13%3
450
October1st to 10thDay
24%10%28%24%11%3
356
11th to 20thDay
30%20%31%15%3
270
21st to endDay
36%18%31%12%2
297
November1st to 10thDay
27%17%29%21%5%1
270
11th to 20thDay
24%21%39%11%4
270
21st to endDay
25%18%37%15%5%1
248
December1st to 10thDay
25%14%36%17%7%1
180
11th to 20thDay
29%18%33%16%31
180
21st to endDay
27%16%36%17%3
272
January1st to 10thNight
17%16%39%22%5%1
950
11th to 20thNight
19%12%38%22%7%2
925
21st to endNight
19%13%35%25%7%1
990
February1st to 10thNight
17%16%34%25%6%1
900
11th to 20thNight
19%15%34%22%9%1
787
21st to endNight
19%11%36%28%6%
592
March1st to 10thNight
15%11%30%33%10%2
720
11th to 20thNight
19%13%29%29%9%1
716
21st to endNight
22%9%23%29%15%2
594
April1st to 10thNight
24%5%29%32%8%2
540
11th to 20thNight
23%9%26%31%11%1
533
21st to endNight
22%6%24%32%14%2
540
May1st to 10thNight
19%8%27%31%14%1
540
11th to 20thNight
19%427%35%12%3
531
21st to endNight
15%7%21%37%19%2
584
June1st to 10thNight
17%5%17%44%14%2
456
11th to 20thNight
14%423%43%14%1
360
21st to endNight
17%419%38%20%2
447
July1st to 10thNight
9%418%44%23%2
525
11th to 20thNight
11%6%26%30%24%3
522
21st to endNight
10%321%39%23%3
591
August1st to 10thNight
10%221%39%26%2
537
11th to 20thNight
12%319%31%30%6%
534
21st to endNight
15%6%21%33%22%2
594
September1st to 10thNight
17%6%19%31%23%4
540
11th to 20thNight
17%5%25%33%18%3
620
21st to endNight
24%7%23%30%16%1
720
October1st to 10thNight
25%10%24%26%14%1
720
11th to 20thNight
30%11%26%24%9%1
720
21st to endNight
33%10%23%26%7%1
792
November1st to 10thNight
27%11%27%28%7%1
740
11th to 20thNight
26%16%30%19%8%1
867
21st to endNight
26%16%30%23%4
950
December1st to 10thNight
22%18%34%18%6%1
950
11th to 20thNight
20%17%34%20%8%1
950
21st to endNight
29%14%33%19%5%1
1045
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