Boundary Waters Canoe Area Wilderness
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Boundary Waters Canoe Area Wilderness clear sky chart from 2005-11-06 to 2024-01-12.

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
25%
25013
12%
74201
6%
24952
31%
24952
16%
54961

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
16%
950
10%
2648
4%
946
23%
946
11%
2116
January11th to 20thNight
15%
906
8%
2535
2%
906
21%
906
10%
2067
January21st to endNight
13%
990
9%
2772
2%
990
19%
990
10%
2274
February1st to 10thNight
17%
900
10%
2358
2%
900
23%
900
14%
1850
February11th to 20thNight
22%
879
16%
2274
5%
875
29%
875
18%
1697
February21st to endNight
20%
636
14%
1820
4%
636
29%
636
13%
1384
March1st to 10thNight
25%
718
15%
2160
8%
718
31%
718
16%
1575
March11th to 20thNight
23%
570
17%
2010
7%
570
36%
570
15%
1351
March21st to endNight
29%
594
17%
2057
12%
594
37%
594
15%
1447
April1st to 10thNight
24%
540
13%
1800
8%
540
33%
540
14%
1279
April11th to 20thNight
27%
533
14%
1775
10%
533
34%
533
16%
1262
April21st to endNight
26%
540
13%
1541
6%
540
32%
540
18%
1138
May1st to 10thNight
27%
540
13%
1440
5%
540
32%
540
20%
1060
May11th to 20thNight
30%
531
14%
1416
6%
531
36%
531
24%
984
May21st to endNight
35%
584
10%
1552
4%
582
38%
582
26%
1066
June1st to 10thNight
35%
540
8%
1440
4%
540
38%
540
26%
988
June11th to 20thNight
33%
540
9%
1303
3%
540
38%
540
31%
873
June21st to endNight
41%
540
9%
1260
5%
540
43%
540
30%
880
July1st to 10thNight
50%
525
12%
1242
6%
525
53%
525
42%
773
July11th to 20thNight
40%
522
12%
1392
5%
522
43%
522
32%
902
July21st to endNight
49%
591
16%
1487
8%
558
51%
558
38%
908
August1st to 10thNight
46%
537
17%
1423
8%
534
51%
534
35%
905
August11th to 20thNight
49%
534
19%
1543
13%
534
56%
534
31%
948
August21st to endNight
41%
594
16%
1930
13%
594
48%
594
28%
1155
September1st to 10thNight
43%
540
16%
1800
13%
540
50%
540
25%
1112
September11th to 20thNight
40%
540
16%
1800
13%
540
47%
540
26%
1096
September21st to endNight
27%
693
14%
2025
8%
693
33%
693
20%
1429
October1st to 10thNight
26%
720
15%
2160
8%
720
32%
720
17%
1563
October11th to 20thNight
19%
720
14%
2160
5%
720
27%
720
14%
1615
October21st to endNight
19%
792
10%
2567
5%
792
25%
792
12%
1968
November1st to 10thNight
19%
835
12%
2501
6%
835
26%
835
12%
1934
November11th to 20thNight
13%
950
8%
2660
3%
950
19%
950
9%
2203
November21st to endNight
13%
950
8%
2660
3%
950
17%
950
8%
2215
December1st to 10thNight
14%
950
6%
2660
2%
950
18%
950
7%
2254
December11th to 20thNight
15%
950
9%
3212
3%
948
20%
948
6%
2590
December21st to endNight
10%
1039
4%
4818
2%
1026
15%
1026
4%
4100

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%11%48%7%45%5%5%7%31%
75210
Night
13%12%5%9%7%45%5%5%6%29%
74505
TransparencyDay
53%5%12%20%9%1
74912
Night
56%5%11%19%9%1
74337
SeeingDay
20%17%34%19%7%2
14981
Night
19%15%34%24%8%1
25021

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
9%14%7%11%8%7%7%8%6%6%17%
1517
11th to 20thDay
11%14%6%14%9%46%5%6%5%19%
1448
21st to endDay
10%13%8%12%10%6%7%8%8%6%13%
1584
February1st to 10thDay
7%12%7%10%7%49%8%7%6%23%
1601
11th to 20thDay
8%10%410%9%5%6%5%7%7%28%
1574
21st to endDay
8%13%8%11%8%445%47%28%
1435
March1st to 10thDay
7%12%5%8%8%46%5%5%6%34%
1798
11th to 20thDay
10%13%6%8%8%34346%34%
1966
21st to endDay
14%12%49%8%4445%6%30%
2299
April1st to 10thDay
14%12%5%10%7%46%5%5%6%28%
2160
11th to 20thDay
18%13%48%5%3445%6%30%
2134
21st to endDay
18%11%5%8%6%44445%32%
2415
May1st to 10thDay
16%12%47%7%34446%32%
2520
11th to 20thDay
17%9%46%5%35%6%6%8%32%
2479
21st to endDay
18%7%25%43446%8%37%
2725
June1st to 10thDay
16%6%35%6%35%5%6%8%38%
2520
11th to 20thDay
16%6%35%5%35%5%7%8%36%
2652
21st to endDay
18%7%25%5%346%7%9%35%
2700
July1st to 10thDay
9%5%246%45%6%6%9%46%
2678
11th to 20thDay
14%6%35%5%35%6%6%10%37%
2520
21st to endDay
13%425%5%45%6%6%8%43%
2743
August1st to 10thDay
10%6%25%6%46%6%6%9%39%
2507
11th to 20thDay
13%6%35%5%35%5%6%9%41%
2354
21st to endDay
13%5%35%5%345%6%9%42%
2426
September1st to 10thDay
16%6%25%6%4446%6%41%
2160
11th to 20thDay
16%8%36%5%3445%8%38%
2160
21st to endDay
20%10%46%6%34446%33%
1913
October1st to 10thDay
18%14%37%5%35%5%6%7%28%
1800
11th to 20thDay
19%18%6%7%6%35%446%23%
1800
21st to endDay
19%21%5%8%5%2233426%
1788
November1st to 10thDay
14%18%7%10%6%45%446%23%
1577
11th to 20thDay
15%16%8%13%10%45%34418%
1520
21st to endDay
15%16%6%14%9%5%6%44417%
1520
December1st to 10thDay
8%14%7%14%13%7%8%45%5%15%
1520
11th to 20thDay
10%16%9%13%8%5%6%6%5%419%
1914
21st to endDay
20%21%8%11%10%4333314%
2783
January1st to 10thNight
8%12%7%14%9%5%7%8%8%6%16%
2648
11th to 20thNight
11%13%7%12%10%6%7%8%6%416%
2535
21st to endNight
9%16%8%12%10%46%9%6%5%14%
2772
February1st to 10thNight
7%11%7%10%9%6%10%8%7%6%21%
2358
11th to 20thNight
8%11%5%9%8%5%8%8%5%6%29%
2273
21st to endNight
7%13%7%13%9%5%5%6%46%24%
1820
March1st to 10thNight
10%10%49%9%5%6%5%46%31%
2149
11th to 20thNight
9%12%5%7%7%35%447%36%
2009
21st to endNight
14%12%38%8%45%45%7%31%
2057
April1st to 10thNight
15%12%47%6%45%6%5%6%30%
1800
11th to 20thNight
16%12%5%6%6%345%6%6%31%
1775
21st to endNight
18%11%47%6%345%5%5%31%
1541
May1st to 10thNight
17%11%46%5%346%5%7%33%
1440
11th to 20thNight
16%8%35%5%35%5%6%7%38%
1416
21st to endNight
17%6%35%4245%6%7%39%
1551
June1st to 10thNight
17%8%35%5%2445%8%38%
1440
11th to 20thNight
13%5%35%5%345%7%8%41%
1303
21st to endNight
14%6%24435%6%7%8%41%
1260
July1st to 10thNight
9%4244345%6%9%51%
1278
11th to 20thNight
11%5%25%5%445%6%7%45%
1440
21st to endNight
8%4244345%5%9%51%
1575
August1st to 10thNight
8%5%25%5%445%7%9%47%
1432
11th to 20thNight
13%6%3443345%7%48%
1543
21st to endNight
13%7%35%42446%8%45%
1930
September1st to 10thNight
14%6%25%435%45%7%45%
1800
11th to 20thNight
15%7%245%2445%7%47%
1800
21st to endNight
22%10%26%5%33346%36%
2025
October1st to 10thNight
19%12%35%5%35%447%33%
2160
11th to 20thNight
17%18%47%5%34446%29%
2160
21st to endNight
20%16%48%5%2445%6%25%
2567
November1st to 10thNight
14%17%7%9%6%35%45%7%23%
2501
11th to 20thNight
15%15%8%13%9%45%445%18%
2660
21st to endNight
12%14%7%15%11%5%5%445%18%
2660
December1st to 10thNight
10%16%7%15%12%5%6%5%5%415%
2660
11th to 20thNight
9%14%7%12%10%6%6%8%5%5%17%
3283
21st to endNight
20%22%8%12%8%3434313%
4884

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
65%39%16%7%
1518
11th to 20thDay
67%46%17%6%
1448
21st to endDay
67%48%13%8%
1584
February1st to 10thDay
58%49%15%12%1
1601
11th to 20thDay
54%410%21%10%1
1583
21st to endDay
57%49%15%14%2
1435
March1st to 10thDay
51%413%19%11%2
1800
11th to 20thDay
54%411%19%12%1
1966
21st to endDay
57%411%15%11%2
2299
April1st to 10thDay
57%6%6%16%13%2
2160
11th to 20thDay
55%5%10%18%11%1
2134
21st to endDay
56%48%17%13%2
2415
May1st to 10thDay
53%5%11%21%9%1
2520
11th to 20thDay
49%6%13%22%9%1
2483
21st to endDay
45%7%13%22%12%1
2725
June1st to 10thDay
44%6%14%24%11%1
2520
11th to 20thDay
44%7%12%23%14%1
2652
21st to endDay
45%8%14%25%8%
2700
July1st to 10thDay
35%6%13%30%15%1
2605
11th to 20thDay
41%7%13%29%10%
2445
21st to endDay
39%7%14%30%10%1
2591
August1st to 10thDay
39%7%17%27%9%1
2492
11th to 20thDay
40%7%18%26%9%
2354
21st to endDay
39%6%17%27%12%
2426
September1st to 10thDay
44%415%28%9%
2160
11th to 20thDay
45%6%21%22%6%
2160
21st to endDay
53%5%13%22%6%
1913
October1st to 10thDay
55%5%14%20%5%
1800
11th to 20thDay
64%410%17%41
1800
21st to endDay
64%38%19%6%
1788
November1st to 10thDay
64%5%10%15%6%1
1577
11th to 20thDay
70%49%12%5%
1520
21st to endDay
71%5%10%9%41
1520
December1st to 10thDay
70%412%11%31
1520
11th to 20thDay
69%311%10%7%1
1915
21st to endDay
77%15%12%4
2783
January1st to 10thNight
64%5%8%15%7%
2648
11th to 20thNight
67%48%14%6%
2535
21st to endNight
68%46%13%8%
2772
February1st to 10thNight
61%49%15%9%1
2358
11th to 20thNight
55%412%17%11%1
2274
21st to endNight
59%49%17%9%2
1820
March1st to 10thNight
55%411%16%12%2
2160
11th to 20thNight
50%411%19%13%2
2010
21st to endNight
53%5%11%18%10%3
2057
April1st to 10thNight
53%6%9%18%14%1
1800
11th to 20thNight
53%5%10%19%12%2
1775
21st to endNight
54%5%7%21%11%2
1541
May1st to 10thNight
50%7%10%21%12%
1440
11th to 20thNight
45%7%12%22%13%2
1417
21st to endNight
43%7%11%24%13%2
1552
June1st to 10thNight
44%5%12%25%12%1
1440
11th to 20thNight
39%5%14%25%16%1
1303
21st to endNight
38%9%16%25%10%2
1260
July1st to 10thNight
29%6%16%33%15%1
1242
11th to 20thNight
35%7%13%29%14%1
1392
21st to endNight
30%7%18%30%14%1
1487
August1st to 10thNight
34%6%17%30%10%2
1423
11th to 20thNight
36%5%16%34%9%1
1543
21st to endNight
37%5%19%26%13%
1930
September1st to 10thNight
39%7%15%30%9%1
1800
11th to 20thNight
38%6%21%30%5%
1800
21st to endNight
51%414%26%5%
2025
October1st to 10thNight
53%6%12%23%6%1
2160
11th to 20thNight
58%5%10%22%5%
2160
21st to endNight
60%6%11%17%5%
2567
November1st to 10thNight
63%411%16%6%
2501
11th to 20thNight
70%410%11%5%
2660
21st to endNight
70%49%12%41
2660
December1st to 10thNight
72%410%10%3
2660
11th to 20thNight
68%5%10%12%6%
3281
21st to endNight
77%35%10%5%
4884

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%19%37%22%5%
270
11th to 20thDay
17%17%39%21%6%
243
21st to endDay
16%23%41%16%4
264
February1st to 10thDay
17%24%43%13%3
240
11th to 20thDay
20%26%37%10%6%1
240
21st to endDay
18%29%41%9%21
198
March1st to 10thDay
12%22%44%18%4
240
11th to 20thDay
18%25%33%15%8%1
240
21st to endDay
24%21%32%14%8%2
385
April1st to 10thDay
24%18%34%18%6%
420
11th to 20thDay
25%19%27%20%8%
412
21st to endDay
26%17%30%19%7%1
564
May1st to 10thDay
23%21%33%17%5%2
603
11th to 20thDay
20%17%36%17%6%3
625
21st to endDay
24%15%32%20%6%2
679
June1st to 10thDay
21%17%32%18%9%3
630
11th to 20thDay
19%17%38%18%6%2
630
21st to endDay
21%15%32%20%9%3
630
July1st to 10thDay
11%11%39%24%11%4
621
11th to 20thDay
15%16%31%23%10%4
618
21st to endDay
13%12%34%23%12%6%
684
August1st to 10thDay
15%11%35%24%12%3
626
11th to 20thDay
16%11%27%28%14%4
615
21st to endDay
20%13%29%24%12%2
545
September1st to 10thDay
19%12%32%25%11%1
450
11th to 20thDay
21%15%32%21%10%2
450
21st to endDay
30%19%25%17%8%2
375
October1st to 10thDay
23%18%33%17%6%3
270
11th to 20thDay
27%21%38%10%3
270
21st to endDay
33%27%29%8%2
297
November1st to 10thDay
27%22%33%15%3
270
11th to 20thDay
23%27%36%10%31
270
21st to endDay
29%20%36%12%31
270
December1st to 10thDay
20%21%37%18%3
270
11th to 20thDay
22%20%39%17%2
270
21st to endDay
21%18%43%13%32
297
January1st to 10thNight
16%19%41%19%4
950
11th to 20thNight
17%19%40%19%5%1
906
21st to endNight
18%18%41%19%4
990
February1st to 10thNight
14%19%40%20%6%1
900
11th to 20thNight
15%21%34%21%7%1
879
21st to endNight
16%16%38%22%7%
636
March1st to 10thNight
15%18%33%27%7%1
720
11th to 20thNight
16%19%36%22%6%
570
21st to endNight
21%11%30%24%11%3
594
April1st to 10thNight
21%13%36%25%6%
540
11th to 20thNight
23%15%32%23%8%
533
21st to endNight
25%10%31%25%8%1
540
May1st to 10thNight
22%14%33%25%5%1
540
11th to 20thNight
20%12%33%26%9%1
531
21st to endNight
20%9%31%30%8%1
584
June1st to 10thNight
20%10%30%29%10%1
540
11th to 20thNight
16%9%37%30%8%
540
21st to endNight
16%10%29%32%13%1
540
July1st to 10thNight
11%5%31%38%15%
525
11th to 20thNight
14%8%33%31%14%1
522
21st to endNight
9%6%32%34%16%2
591
August1st to 10thNight
11%6%33%36%13%1
537
11th to 20thNight
16%8%22%32%19%4
534
21st to endNight
14%9%29%30%17%
594
September1st to 10thNight
19%8%27%31%14%1
540
11th to 20thNight
18%9%30%27%14%1
540
21st to endNight
28%11%29%22%7%2
693
October1st to 10thNight
26%14%29%21%8%1
720
11th to 20thNight
30%15%31%19%41
720
21st to endNight
28%14%33%20%5%
792
November1st to 10thNight
24%17%32%21%41
835
11th to 20thNight
24%19%34%17%6%1
950
21st to endNight
21%22%38%15%4
950
December1st to 10thNight
17%20%38%20%5%
950
11th to 20thNight
20%19%35%19%6%1
950
21st to endNight
25%17%35%17%6%
1045
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