Voyageurs National Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Voyageurs National Park clear sky chart from 2005-11-05 to 2017-10-06.

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
27%
16318
11%
46920
6%
16271
33%
16271
16%
34551

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
21%
900
8%
2685
5%
895
25%
895
10%
2153
January16th to endNight
14%
960
8%
2679
2%
960
20%
960
10%
2171
February1st to 15thNight
22%
880
12%
2288
4%
876
27%
876
15%
1703
February16th to endNight
27%
774
11%
2036
4%
774
32%
774
15%
1573
March1st to 15thNight
27%
618
14%
2058
9%
618
32%
618
13%
1487
March16th to endNight
28%
576
14%
2076
9%
576
37%
576
14%
1429
April1st to 15thNight
26%
539
15%
1797
9%
539
36%
539
16%
1217
April16th to endNight
28%
540
14%
1605
6%
540
37%
540
14%
1166
May1st to 15thNight
25%
540
11%
1440
3%
540
30%
540
18%
1073
May16th to endNight
33%
563
11%
1498
3%
561
37%
561
22%
1035
June1st to 15thNight
33%
540
6%
1263
3%
540
36%
540
26%
882
June16th to endNight
39%
540
6%
1260
3%
540
41%
540
25%
897
July1st to 15thNight
44%
510
9%
1190
6%
510
46%
510
36%
769
July16th to endNight
42%
564
16%
1355
5%
531
49%
531
34%
838
August1st to 15thNight
53%
539
19%
1517
12%
536
57%
536
35%
897
August16th to endNight
45%
573
20%
1764
15%
573
54%
573
31%
1034
September1st to 15thNight
45%
540
16%
1800
14%
540
52%
540
25%
1097
September16th to endNight
34%
594
15%
1974
12%
594
41%
594
20%
1319
October1st to 15thNight
28%
684
15%
2052
9%
684
33%
684
17%
1451
October16th to endNight
22%
709
10%
2188
5%
709
28%
709
13%
1661
November1st to 15thNight
20%
875
10%
2451
4%
875
25%
875
12%
1926
November16th to endNight
17%
900
9%
2520
4%
900
21%
900
8%
2103
December1st to 15thNight
16%
900
5%
2544
2%
900
19%
900
7%
2171
December16th to endNight
14%
960
7%
2880
2%
960
19%
960
6%
2499

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
15%9%47%5%35%5%5%6%32%
48291
Night
14%10%47%6%3445%6%31%
47076
Cloud CoverDay
15%9%46%5%35%45%6%32%
48302
Night
14%10%47%6%3445%6%31%
47080
Cloud CoverDay
15%9%46%5%35%5%5%6%32%
48300
Night
14%10%47%6%35%45%6%31%
47080
TransparencyDay
51%6%13%20%7%
47965
Night
52%6%12%19%7%
46920
SeeingDay
19%16%27%21%10%3
6302
Night
17%21%26%23%9%1
16318

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
13%11%7%9%7%45%7%6%6%21%
1253
16th to endDay
11%14%7%11%8%47%6%7%5%15%
1539
February1st to 15thDay
7%13%49%6%48%5%6%7%25%
1575
16th to endDay
11%11%6%9%7%5%5%45%5%28%
1437
March1st to 15thDay
11%11%5%7%6%3345%5%34%
1903
16th to endDay
15%11%47%5%23447%32%
2148
April1st to 15thDay
13%9%46%5%25%45%8%34%
2151
16th to endDay
20%11%36%423445%32%
2352
May1st to 15thDay
21%10%36%5%345%45%29%
2511
16th to endDay
19%6%25%5%3446%7%34%
2617
June1st to 15thDay
17%6%25%5%35%5%5%7%33%
2694
16th to endDay
17%6%36%6%345%5%8%33%
2700
July1st to 15thDay
12%5%24435%5%5%8%41%
2700
16th to endDay
11%5%25%435%5%6%9%42%
2718
August1st to 15thDay
9%5%146%36%6%6%9%40%
2433
16th to endDay
13%424435%5%5%8%41%
2438
September1st to 15thDay
12%7%25%4345%5%7%42%
2160
16th to endDay
21%7%25%423347%37%
1971
October1st to 15thDay
19%12%36%5%23446%30%
1706
16th to endDay
23%14%46%5%2432426%
1681
November1st to 15thDay
15%17%7%7%43435%425%
1407
16th to endDay
16%15%7%13%8%45%33317%
1440
December1st to 15thDay
14%14%7%12%9%5%6%6%6%413%
1413
16th to endDay
14%20%8%12%8%45%42412%
1344
January1st to 15thNight
10%13%7%11%8%36%6%6%5%18%
2685
16th to endNight
11%13%6%11%8%45%6%6%6%18%
2679
February1st to 15thNight
8%10%49%7%46%5%6%6%30%
2285
16th to endNight
9%10%5%10%7%46%5%5%5%27%
2036
March1st to 15thNight
12%10%6%7%6%45%5%45%32%
2046
16th to endNight
16%9%36%5%34435%35%
2076
April1st to 15thNight
14%10%46%42445%6%36%
1797
16th to endNight
19%10%36%5%3444434%
1605
May1st to 15thNight
21%10%34425%45%6%32%
1440
16th to endNight
17%5%25%4345%5%8%38%
1496
June1st to 15thNight
17%5%15%4245%47%41%
1263
16th to endNight
14%5%36%334447%41%
1260
July1st to 15thNight
8%3245%24349%51%
1260
16th to endNight
7%31442445%8%53%
1449
August1st to 15thNight
8%5%1332335%7%54%
1526
16th to endNight
11%5%1432335%8%50%
1764
September1st to 15thNight
12%5%2442445%6%48%
1800
16th to endNight
17%7%35%5%23445%40%
1974
October1st to 15thNight
16%10%36%43445%6%34%
2052
16th to endNight
21%13%36%5%24346%27%
2188
November1st to 15thNight
16%15%5%8%7%24445%25%
2451
16th to endNight
16%13%7%12%8%35%445%18%
2520
December1st to 15thNight
11%15%6%12%11%46%7%6%6%13%
2544
16th to endNight
16%17%10%12%8%345%45%12%
2880

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%12%7%8%7%36%6%6%6%21%
1253
16th to endDay
11%14%8%9%9%47%6%6%6%15%
1539
February1st to 15thDay
8%12%5%9%6%48%6%5%8%25%
1575
16th to endDay
10%11%6%8%6%5%5%5%5%6%28%
1437
March1st to 15thDay
11%11%5%7%6%33445%34%
1914
16th to endDay
15%11%36%4335%47%33%
2148
April1st to 15thDay
12%9%36%5%3445%7%35%
2151
16th to endDay
19%10%36%434346%33%
2352
May1st to 15thDay
20%9%35%6%345%45%29%
2511
16th to endDay
19%5%25%5%35%45%7%35%
2617
June1st to 15thDay
16%7%35%5%35%46%7%34%
2694
16th to endDay
16%6%36%6%345%5%8%33%
2700
July1st to 15thDay
11%425%435%5%6%8%42%
2700
16th to endDay
10%5%25%425%5%6%8%42%
2718
August1st to 15thDay
9%5%25%5%26%6%6%8%40%
2433
16th to endDay
12%5%24435%5%5%7%42%
2438
September1st to 15thDay
11%6%25%434447%43%
2160
16th to endDay
21%6%25%42335%6%37%
1971
October1st to 15thDay
19%12%37%423446%30%
1706
16th to endDay
23%14%46%6%3422427%
1681
November1st to 15thDay
16%14%8%8%43445%5%24%
1407
16th to endDay
16%15%7%13%9%4434416%
1440
December1st to 15thDay
14%14%6%12%10%5%7%6%4313%
1413
16th to endDay
14%19%9%11%8%35%43412%
1344
January1st to 15thNight
10%13%7%11%8%46%6%6%5%18%
2685
16th to endNight
12%13%6%11%8%5%6%6%6%6%18%
2679
February1st to 15thNight
8%10%5%9%7%36%5%5%7%30%
2278
16th to endNight
9%11%5%10%8%36%6%46%27%
2036
March1st to 15thNight
11%11%5%7%6%45%445%32%
2058
16th to endNight
17%9%36%5%23436%35%
2076
April1st to 15thNight
14%10%46%5%2345%6%36%
1797
16th to endNight
18%9%45%5%3344434%
1605
May1st to 15thNight
21%9%35%43345%6%32%
1439
16th to endNight
18%6%244245%48%39%
1496
June1st to 15thNight
18%425%424447%41%
1263
16th to endNight
14%5%36%4245%47%41%
1260
July1st to 15thNight
9%31442435%8%50%
1260
16th to endNight
8%22442445%8%52%
1449
August1st to 15thNight
8%41432445%7%53%
1526
16th to endNight
11%41432435%7%50%
1764
September1st to 15thNight
12%5%14423446%49%
1800
16th to endNight
18%6%24433445%40%
1974
October1st to 15thNight
16%10%36%43436%6%34%
2052
16th to endNight
20%13%36%6%33346%27%
2188
November1st to 15thNight
17%14%5%8%6%34445%25%
2451
16th to endNight
16%13%7%12%9%35%44418%
2520
December1st to 15thNight
12%15%6%11%10%47%6%6%5%12%
2544
16th to endNight
16%18%9%12%8%345%4412%
2880

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%13%7%8%7%36%6%6%6%21%
1253
16th to endDay
11%14%8%10%9%47%6%6%6%15%
1539
February1st to 15thDay
8%12%5%9%6%47%7%5%8%25%
1575
16th to endDay
10%12%6%8%6%5%5%5%5%6%28%
1437
March1st to 15thDay
11%10%6%7%6%33445%34%
1914
16th to endDay
15%11%36%4335%5%7%33%
2146
April1st to 15thDay
12%9%36%5%4445%7%35%
2151
16th to endDay
19%10%36%434346%33%
2352
May1st to 15thDay
20%9%36%6%34445%29%
2511
16th to endDay
19%6%245%35%46%6%35%
2617
June1st to 15thDay
16%7%25%5%35%46%7%34%
2694
16th to endDay
17%6%35%6%35%45%8%33%
2700
July1st to 15thDay
12%425%435%5%6%8%42%
2700
16th to endDay
10%5%25%425%5%6%8%42%
2718
August1st to 15thDay
10%5%245%35%6%6%9%40%
2433
16th to endDay
12%5%235%35%5%5%7%42%
2438
September1st to 15thDay
12%6%25%42445%7%43%
2160
16th to endDay
21%6%35%423446%37%
1971
October1st to 15thDay
20%12%27%424445%30%
1706
16th to endDay
23%13%5%5%6%3322426%
1681
November1st to 15thDay
16%14%8%8%43445%5%24%
1407
16th to endDay
16%15%7%13%9%44335%16%
1440
December1st to 15thDay
14%14%6%12%10%5%6%6%4313%
1413
16th to endDay
14%19%9%12%8%35%5%3413%
1344
January1st to 15thNight
10%13%7%10%8%46%7%6%5%18%
2685
16th to endNight
12%12%6%11%8%46%6%6%6%18%
2679
February1st to 15thNight
8%10%5%10%7%36%5%6%6%30%
2278
16th to endNight
9%11%5%10%8%36%6%5%6%27%
2036
March1st to 15thNight
11%12%47%5%45%45%5%32%
2058
16th to endNight
17%9%46%424436%35%
2076
April1st to 15thNight
14%10%46%43345%6%36%
1797
16th to endNight
18%9%46%5%3435%434%
1605
May1st to 15thNight
22%9%3443345%5%33%
1439
16th to endNight
17%6%24424448%39%
1496
June1st to 15thNight
18%425%424347%41%
1263
16th to endNight
14%5%345%24447%41%
1260
July1st to 15thNight
9%3145%2435%8%51%
1260
16th to endNight
8%214334448%53%
1449
August1st to 15thNight
8%42432435%7%53%
1526
16th to endNight
11%41432435%8%50%
1764
September1st to 15thNight
12%5%25%424345%49%
1800
16th to endNight
18%6%24433445%40%
1974
October1st to 15thNight
16%11%35%43435%6%34%
2052
16th to endNight
20%13%46%5%34345%28%
2188
November1st to 15thNight
17%14%5%8%6%34445%25%
2451
16th to endNight
16%14%7%12%9%35%335%18%
2520
December1st to 15thNight
12%15%6%12%10%47%6%6%5%13%
2544
16th to endNight
16%18%9%12%7%34435%12%
2880

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
60%6%9%17%4
1254
16th to endDay
67%6%10%11%3
1539
February1st to 15thDay
55%7%11%17%8%
1576
16th to endDay
58%411%20%4
1437
March1st to 15thDay
51%5%15%17%9%
1914
16th to endDay
52%6%13%18%6%1
2148
April1st to 15thDay
48%5%11%18%15%1
2151
16th to endDay
54%49%19%11%1
2352
May1st to 15thDay
56%6%10%19%5%
2511
16th to endDay
47%7%12%20%11%
2621
June1st to 15thDay
48%7%14%21%6%
2694
16th to endDay
49%7%15%20%6%
2700
July1st to 15thDay
38%7%13%30%10%
2541
16th to endDay
38%8%15%26%10%
2549
August1st to 15thDay
39%9%17%25%6%1
2418
16th to endDay
38%8%17%26%9%
2438
September1st to 15thDay
40%6%14%30%7%
2160
16th to endDay
48%6%16%23%4
1971
October1st to 15thDay
54%6%14%18%6%
1706
16th to endDay
63%411%16%4
1681
November1st to 15thDay
60%6%11%15%5%
1407
16th to endDay
71%6%7%9%4
1440
December1st to 15thDay
70%7%10%8%2
1413
16th to endDay
75%47%8%3
1344
January1st to 15thNight
63%6%9%16%4
2685
16th to endNight
63%6%11%14%3
2679
February1st to 15thNight
52%6%14%17%8%
2288
16th to endNight
56%6%11%19%5%
2036
March1st to 15thNight
52%7%11%18%9%
2058
16th to endNight
51%5%13%19%8%2
2076
April1st to 15thNight
48%410%19%14%1
1797
16th to endNight
52%5%9%16%14%1
1605
May1st to 15thNight
51%6%11%20%9%
1440
16th to endNight
44%6%11%22%12%2
1498
June1st to 15thNight
42%5%14%24%12%
1263
16th to endNight
41%7%15%24%8%1
1260
July1st to 15thNight
31%6%15%32%13%
1190
16th to endNight
29%7%14%32%14%1
1355
August1st to 15thNight
29%6%15%32%14%1
1517
16th to endNight
31%6%16%30%13%
1764
September1st to 15thNight
35%7%16%30%9%
1800
16th to endNight
44%7%15%26%5%
1974
October1st to 15thNight
49%7%12%25%6%
2052
16th to endNight
57%6%12%19%3
2188
November1st to 15thNight
60%6%11%15%5%
2451
16th to endNight
67%7%10%9%4
2520
December1st to 15thNight
68%8%10%9%2
2544
16th to endNight
74%5%7%9%2
2880

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
18%17%34%21%7%
90
16th to endDay
27%5%38%22%33
96
February1st to 15thDay
20%20%40%16%3
90
16th to endDay
28%19%32%12%6%1
81
March1st to 15thDay
16%13%28%30%8%2
90
16th to endDay
20%16%25%21%11%5%
132
April1st to 15thDay
14%21%31%22%8%1
270
16th to endDay
26%21%25%18%7%1
438
May1st to 15thDay
25%23%25%16%7%2
468
16th to endDay
24%19%22%21%9%3
517
June1st to 15thDay
18%22%30%17%8%3
495
16th to endDay
18%18%26%21%10%4
495
July1st to 15thDay
17%14%21%28%13%5%
475
16th to endDay
11%19%24%23%14%6%
515
August1st to 15thDay
11%12%25%24%20%4
493
16th to endDay
17%12%24%25%16%3
478
September1st to 15thDay
13%11%31%27%13%2
315
16th to endDay
27%16%26%20%7%1
195
October1st to 15thDay
27%10%32%14%13%2
107
16th to endDay
33%7%40%14%22
96
November1st to 15thDay
24%12%32%21%8%1
90
16th to endDay
43%11%21%15%8%
90
December1st to 15thDay
31%442%20%2
90
16th to endDay
23%14%36%18%33
96
January1st to 15thNight
13%25%31%18%9%1
900
16th to endNight
15%25%34%20%3
960
February1st to 15thNight
11%25%28%23%9%1
880
16th to endNight
11%22%27%22%10%3
774
March1st to 15thNight
13%26%24%24%9%
618
16th to endNight
18%24%22%21%9%3
576
April1st to 15thNight
17%22%28%23%6%
539
16th to endNight
23%23%20%24%7%
540
May1st to 15thNight
21%22%27%19%7%1
540
16th to endNight
16%23%23%25%11%
563
June1st to 15thNight
17%21%23%27%9%
540
16th to endNight
15%21%18%29%13%1
540
July1st to 15thNight
9%15%25%31%17%
510
16th to endNight
9%20%24%26%17%1
564
August1st to 15thNight
10%11%20%32%22%3
539
16th to endNight
13%12%25%30%15%2
573
September1st to 15thNight
15%12%24%28%17%1
540
16th to endNight
19%14%26%24%13%1
594
October1st to 15thNight
22%19%26%23%7%
684
16th to endNight
27%17%27%22%5%
709
November1st to 15thNight
20%24%28%20%5%1
875
16th to endNight
20%26%27%18%6%
900
December1st to 15thNight
16%25%31%19%6%
900
16th to endNight
21%25%24%20%6%1
960
Page generated at 2017-10-07 13:07:46. Version ac04

Copyright 2017 A. Danko


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