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Copper Harbor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Copper Harbor clear sky chart from 2005-11-05 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
28%
16651
9%
48904
6%
16605
32%
16605
13%
37266

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
11%
975
1%
2716
0%
970
12%
970
2%
2507
January16th to endNight
15%
1040
3%
2912
1%
1040
17%
1040
5%
2622
February1st to 15thNight
19%
948
4%
2562
1%
944
21%
944
8%
2201
February16th to endNight
27%
631
8%
1893
5%
631
30%
631
11%
1518
March1st to 15thNight
30%
720
13%
2160
9%
720
34%
720
17%
1531
March16th to endNight
33%
633
16%
2016
11%
633
40%
633
16%
1380
April1st to 15thNight
29%
539
11%
1797
7%
539
37%
539
14%
1281
April16th to endNight
31%
540
15%
1655
8%
540
38%
540
17%
1138
May1st to 15thNight
33%
540
10%
1461
7%
540
36%
540
18%
1070
May16th to endNight
39%
562
12%
1498
6%
561
43%
561
21%
1046
June1st to 15thNight
44%
423
8%
1323
6%
423
46%
423
19%
881
June16th to endNight
42%
417
8%
1317
5%
417
45%
417
18%
874
July1st to 15thNight
52%
510
9%
1360
6%
510
53%
510
31%
853
July16th to endNight
51%
564
16%
1417
9%
531
58%
531
35%
849
August1st to 15thNight
58%
539
20%
1431
14%
536
62%
536
38%
843
August16th to endNight
47%
573
17%
1836
12%
573
53%
573
27%
1070
September1st to 15thNight
50%
540
17%
1800
13%
540
55%
540
24%
1070
September16th to endNight
41%
711
13%
1974
10%
711
43%
711
24%
1329
October1st to 15thNight
32%
720
14%
2108
9%
720
37%
720
19%
1483
October16th to endNight
25%
768
8%
2496
4%
768
29%
768
11%
1940
November1st to 15thNight
20%
768
10%
2479
6%
768
26%
768
10%
1938
November16th to endNight
16%
975
6%
2759
3%
975
19%
975
6%
2409
December1st to 15thNight
8%
975
1%
2925
0%
975
9%
975
3%
2686
December16th to endNight
9%
1040
3%
3009
1%
1040
12%
1040
3%
2747

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%10%48%7%35%446%30%
49165
Night
13%11%5%9%8%45%445%25%
49071
Cloud CoverDay
13%9%48%7%45%446%31%
49175
Night
14%11%5%9%8%45%5%5%5%25%
49076
Cloud CoverDay
13%9%48%7%35%446%30%
49174
Night
14%11%5%9%8%45%445%25%
49076
TransparencyDay
53%413%19%8%
48850
Night
59%411%16%6%
48904
SeeingDay
17%13%25%27%13%2
6578
Night
16%21%23%23%12%1
16652

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
12%16%9%16%13%8%8%4216%
1552
16th to endDay
10%14%8%16%15%7%7%4328%
1664
February1st to 15thDay
8%12%6%14%16%8%8%43312%
1597
16th to endDay
10%14%7%14%12%5%6%45%5%13%
1580
March1st to 15thDay
11%10%6%11%9%45%445%25%
1790
16th to endDay
16%10%6%8%5%35%446%27%
2216
April1st to 15thDay
14%10%46%6%34446%32%
2151
16th to endDay
18%9%25%5%3445%7%32%
2304
May1st to 15thDay
15%9%35%5%34446%36%
2490
16th to endDay
12%7%36%5%35%45%8%36%
2617
June1st to 15thDay
12%6%35%435%447%42%
2631
16th to endDay
13%5%35%6%2446%8%39%
2637
July1st to 15thDay
9%42442445%7%48%
2520
16th to endDay
8%315%5%24449%50%
2655
August1st to 15thDay
9%41432446%7%50%
2520
16th to endDay
11%6%1443445%8%44%
2366
September1st to 15thDay
13%7%2442445%7%43%
2154
16th to endDay
18%7%35%6%34447%34%
1980
October1st to 15thDay
17%12%37%6%33446%29%
1851
16th to endDay
23%17%6%11%6%3433315%
1728
November1st to 15thDay
17%21%5%9%435%43418%
1707
16th to endDay
15%19%7%16%11%443239%
1527
December1st to 15thDay
12%18%10%20%14%45%3323
1365
16th to endDay
17%19%12%15%10%47%4224
1563
January1st to 15thNight
13%13%8%16%14%7%10%5%325%
2716
16th to endNight
10%13%9%15%15%8%6%4437%
2912
February1st to 15thNight
9%12%6%12%14%8%10%5%3413%
2559
16th to endNight
11%13%7%10%10%5%6%45%5%17%
1893
March1st to 15thNight
10%11%37%8%45%446%32%
2147
16th to endNight
13%10%47%5%34447%33%
2016
April1st to 15thNight
16%9%35%7%46%5%45%30%
1797
16th to endNight
19%9%25%424446%34%
1655
May1st to 15thNight
19%7%37%8%345%5%6%29%
1461
16th to endNight
12%6%36%6%25%5%6%6%37%
1496
June1st to 15thNight
14%6%25%6%36%5%8%6%34%
1323
16th to endNight
14%6%25%6%35%5%6%8%35%
1317
July1st to 15thNight
10%5%245%3446%7%45%
1440
16th to endNight
7%324315%6%6%9%49%
1513
August1st to 15thNight
8%4134245%5%8%52%
1440
16th to endNight
11%5%25%433447%46%
1836
September1st to 15thNight
9%7%25%5%2445%6%46%
1800
16th to endNight
16%7%26%6%23446%39%
1974
October1st to 15thNight
18%10%36%42445%5%34%
2108
16th to endNight
20%13%48%8%34445%22%
2496
November1st to 15thNight
17%18%7%8%5%35%34421%
2479
16th to endNight
17%17%7%14%9%25%44412%
2759
December1st to 15thNight
13%17%9%21%13%5%43226%
2925
16th to endNight
14%20%11%16%10%45%3226%
3009

Percentage Cloud Cover SW (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
12%16%8%15%12%6%10%4326%
1552
16th to endDay
10%14%7%17%17%7%6%4338%
1664
February1st to 15thDay
8%13%5%16%14%9%8%5%3311%
1597
16th to endDay
10%12%7%13%12%5%7%5%46%13%
1580
March1st to 15thDay
12%10%6%11%10%45%445%25%
1800
16th to endDay
15%8%5%10%6%34446%28%
2216
April1st to 15thDay
14%10%46%5%45%447%32%
2151
16th to endDay
16%9%36%435%45%7%33%
2304
May1st to 15thDay
15%8%35%5%3445%6%37%
2490
16th to endDay
11%7%26%5%345%5%9%37%
2617
June1st to 15thDay
12%5%25%5%3345%8%42%
2631
16th to endDay
12%5%25%5%345%5%8%39%
2637
July1st to 15thDay
9%4244345%5%6%48%
2520
16th to endDay
7%31442345%8%52%
2655
August1st to 15thDay
8%4133345%6%9%50%
2520
16th to endDay
11%5%234345%5%8%45%
2366
September1st to 15thDay
13%7%25%5%2335%7%43%
2154
16th to endDay
17%7%26%5%2445%7%35%
1980
October1st to 15thDay
17%10%26%7%345%5%6%29%
1851
16th to endDay
22%18%6%10%6%45%33415%
1728
November1st to 15thDay
18%16%6%9%6%35%445%18%
1707
16th to endDay
16%19%7%14%10%45%4339%
1527
December1st to 15thDay
13%18%9%19%13%45%3424
1365
16th to endDay
18%17%11%15%11%46%4224
1563
January1st to 15thNight
13%12%8%16%13%6%10%5%325%
2716
16th to endNight
10%13%7%14%14%8%8%6%437%
2912
February1st to 15thNight
8%12%6%12%11%8%9%8%45%12%
2552
16th to endNight
11%12%5%10%10%5%6%5%5%6%18%
1893
March1st to 15thNight
11%11%47%6%45%5%5%6%31%
2160
16th to endNight
12%10%47%6%35%447%32%
2016
April1st to 15thNight
17%8%36%7%45%5%5%6%30%
1797
16th to endNight
19%9%25%42345%7%34%
1655
May1st to 15thNight
18%7%37%7%345%46%30%
1460
16th to endNight
11%6%35%6%45%46%6%37%
1496
June1st to 15thNight
14%5%36%6%345%7%8%34%
1323
16th to endNight
16%5%25%436%46%8%36%
1317
July1st to 15thNight
11%4245%345%5%8%43%
1440
16th to endNight
6%5%243245%6%8%49%
1513
August1st to 15thNight
7%4243345%5%7%51%
1440
16th to endNight
10%425%43435%7%46%
1836
September1st to 15thNight
11%6%25%434446%46%
1800
16th to endNight
15%7%345%2345%6%39%
1974
October1st to 15thNight
17%8%36%5%34445%35%
2108
16th to endNight
19%14%38%7%45%45%5%21%
2496
November1st to 15thNight
18%16%5%7%6%445%45%21%
2479
16th to endNight
16%18%8%11%9%45%5%4412%
2759
December1st to 15thNight
14%18%9%19%11%45%3326%
2925
16th to endNight
16%19%9%15%9%5%6%4426%
3009

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
12%16%8%15%13%7%9%5%216%
1552
16th to endDay
10%14%8%17%17%7%6%4237%
1664
February1st to 15thDay
8%12%6%16%14%11%7%5%3310%
1597
16th to endDay
10%13%7%13%13%6%7%45%5%13%
1580
March1st to 15thDay
12%10%6%11%10%45%445%25%
1800
16th to endDay
15%9%5%9%7%34447%27%
2215
April1st to 15thDay
14%9%37%5%35%45%5%33%
2151
16th to endDay
16%9%36%5%25%447%34%
2304
May1st to 15thDay
15%8%35%5%35%45%6%37%
2490
16th to endDay
11%7%36%5%35%5%5%9%36%
2617
June1st to 15thDay
11%6%35%5%2445%8%42%
2631
16th to endDay
12%5%35%5%35%46%9%39%
2637
July1st to 15thDay
9%4244245%5%7%48%
2520
16th to endDay
7%314324448%53%
2655
August1st to 15thDay
8%3143245%5%8%50%
2520
16th to endDay
11%5%2433445%8%46%
2366
September1st to 15thDay
13%7%2442335%7%43%
2154
16th to endDay
17%7%36%5%25%45%6%35%
1980
October1st to 15thDay
16%10%37%7%245%5%6%28%
1851
16th to endDay
23%17%6%10%7%3333414%
1728
November1st to 15thDay
18%18%5%10%6%245%35%18%
1707
16th to endDay
17%19%8%14%11%444239%
1527
December1st to 15thDay
13%17%10%21%12%5%6%3323
1365
16th to endDay
18%19%11%16%10%37%4224
1563
January1st to 15thNight
13%12%8%16%14%7%10%5%225%
2716
16th to endNight
11%13%7%15%15%8%8%5%327%
2912
February1st to 15thNight
8%12%7%12%14%8%10%7%4312%
2552
16th to endNight
12%13%6%10%11%5%7%45%5%18%
1893
March1st to 15thNight
11%11%48%7%35%5%5%5%30%
2160
16th to endNight
12%10%48%6%35%5%47%32%
2016
April1st to 15thNight
16%8%46%7%45%45%6%30%
1797
16th to endNight
19%9%35%33345%7%34%
1655
May1st to 15thNight
18%7%37%7%35%45%6%30%
1460
16th to endNight
11%7%36%6%36%5%6%6%37%
1496
June1st to 15thNight
14%6%26%6%345%7%8%34%
1323
16th to endNight
15%6%25%5%345%6%8%35%
1317
July1st to 15thNight
11%425%5%245%6%7%43%
1440
16th to endNight
6%5%24325%5%6%9%49%
1513
August1st to 15thNight
7%3243245%5%7%51%
1440
16th to endNight
9%5%3444446%7%46%
1836
September1st to 15thNight
11%7%25%44435%6%45%
1800
16th to endNight
14%8%246%24446%39%
1974
October1st to 15thNight
18%9%36%5%24345%35%
2108
16th to endNight
19%15%48%7%44445%20%
2496
November1st to 15thNight
18%17%5%8%6%45%335%21%
2479
16th to endNight
16%18%8%13%9%5%443311%
2759
December1st to 15thNight
14%19%9%20%11%5%5%4225%
2925
16th to endNight
16%19%9%14%10%5%7%4226%
3009

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
83%446%
1553
16th to endDay
78%5%8%6%1
1664
February1st to 15thDay
76%311%7%
1598
16th to endDay
71%48%11%3
1580
March1st to 15thDay
59%411%14%8%
1800
16th to endDay
56%413%18%6%1
2216
April1st to 15thDay
51%411%20%11%1
2151
16th to endDay
51%49%23%9%1
2304
May1st to 15thDay
48%312%22%11%1
2490
16th to endDay
45%5%12%24%12%
2621
June1st to 15thDay
41%417%24%11%
2631
16th to endDay
40%5%17%27%8%
2637
July1st to 15thDay
33%5%13%31%15%1
2371
16th to endDay
30%416%30%15%
2488
August1st to 15thDay
30%5%18%32%12%
2505
16th to endDay
36%5%18%26%12%
2366
September1st to 15thDay
40%417%29%7%
2154
16th to endDay
48%417%22%5%
1980
October1st to 15thDay
54%413%21%5%
1851
16th to endDay
73%49%9%3
1728
November1st to 15thDay
66%411%13%4
1707
16th to endDay
80%47%5%2
1527
December1st to 15thDay
85%27%3
1365
16th to endDay
85%36%4
1563
January1st to 15thNight
83%46%4
2716
16th to endNight
79%48%6%
2912
February1st to 15thNight
72%412%9%
2562
16th to endNight
66%312%14%2
1893
March1st to 15thNight
51%413%19%9%
2160
16th to endNight
50%412%21%9%1
2016
April1st to 15thNight
53%49%20%9%1
1797
16th to endNight
49%39%22%13%
1655
May1st to 15thNight
52%410%18%11%
1461
16th to endNight
44%6%11%23%13%
1498
June1st to 15thNight
45%5%11%22%13%1
1323
16th to endNight
43%7%15%21%11%
1317
July1st to 15thNight
35%415%29%15%
1360
16th to endNight
29%6%15%31%14%2
1417
August1st to 15thNight
28%5%17%32%12%2
1431
16th to endNight
35%417%26%14%1
1836
September1st to 15thNight
38%414%32%10%
1800
16th to endNight
44%417%28%4
1974
October1st to 15thNight
50%315%21%7%
2108
16th to endNight
62%414%12%5%
2496
November1st to 15thNight
64%411%14%5%
2479
16th to endNight
75%49%7%2
2759
December1st to 15thNight
83%37%4
2925
16th to endNight
82%47%4
3009

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%12%26%33%7%
135
16th to endDay
15%9%34%30%9%
144
February1st to 15thDay
18%12%40%23%5%
130
16th to endDay
23%14%34%22%4
81
March1st to 15thDay
15%20%22%30%12%
90
16th to endDay
20%17%25%22%10%2
248
April1st to 15thDay
22%16%22%28%8%1
270
16th to endDay
23%14%27%22%9%3
270
May1st to 15thDay
17%19%27%24%10%2
447
16th to endDay
19%17%23%26%10%2
517
June1st to 15thDay
14%14%26%33%8%2
495
16th to endDay
16%15%22%25%16%3
495
July1st to 15thDay
12%11%22%32%17%3
475
16th to endDay
8%15%22%31%16%4
515
August1st to 15thDay
13%8%20%32%21%3
493
16th to endDay
16%8%18%33%19%3
335
September1st to 15thDay
14%10%20%25%24%5%
315
16th to endDay
18%10%25%25%16%3
314
October1st to 15thDay
20%8%30%22%14%2
192
16th to endDay
29%12%35%17%4
144
November1st to 15thDay
22%20%25%20%11%1
135
16th to endDay
28%17%30%15%6%1
127
December1st to 15thDay
27%8%37%21%4
90
16th to endDay
20%19%38%19%1
121
January1st to 15thNight
14%28%33%18%5%
975
16th to endNight
13%26%30%21%6%
1040
February1st to 15thNight
13%27%28%23%6%1
948
16th to endNight
16%20%25%28%8%1
631
March1st to 15thNight
13%25%24%23%10%2
720
16th to endNight
12%24%23%24%13%2
633
April1st to 15thNight
16%20%26%25%8%1
539
16th to endNight
22%19%20%23%10%3
540
May1st to 15thNight
17%20%20%25%14%2
540
16th to endNight
13%20%19%25%17%3
563
June1st to 15thNight
13%20%12%37%13%3
423
16th to endNight
17%19%13%28%18%3
417
July1st to 15thNight
11%14%14%30%23%4
510
16th to endNight
9%17%16%29%23%3
564
August1st to 15thNight
8%11%15%26%34%3
539
16th to endNight
14%12%19%27%23%3
573
September1st to 15thNight
12%12%19%25%23%5%
540
16th to endNight
16%13%20%30%17%2
711
October1st to 15thNight
21%15%24%22%14%1
720
16th to endNight
25%17%25%24%6%
768
November1st to 15thNight
21%24%25%20%7%
768
16th to endNight
21%27%25%18%6%
975
December1st to 15thNight
20%30%28%16%4
975
16th to endNight
20%28%27%17%5%1
1040
Page generated at 2018-02-15 10:58:47. Version ac04

Copyright 2018 A. Danko


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