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 2024-11-05.

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 Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(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

By Month

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 Forecast	Data Points
Cloud Cover	Day	13% 11% 4 9% 6% 5% 5% 4 6% 7% 32%	102295
	Night	13% 12% 5% 10% 6% 5% 5% 4 5% 6% 29%	96893
Transparency	Day	28% 47% 7% 12% 5%	105750
	Night	30% 47% 7% 11% 5%	101525
Seeing	Day	20% 17% 34% 19% 7% 2	16182
	Night	19% 15% 34% 24% 8% 1	26065

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	8% 15% 7% 15% 12% 6% 6% 5% 5% 6% 15%	2527
	11th to 20th	Day	6% 10% 5% 17% 11% 8% 8% 6% 7% 5% 17%	2530
	21st to end	Day	8% 17% 13% 18% 8% 5% 5% 5% 6% 4 11%	2783
February	1st to 10th	Day	7% 12% 6% 12% 6% 5% 9% 6% 7% 5% 23%	1690
	11th to 20th	Day	8% 11% 4 12% 8% 7% 6% 3 6% 6% 28%	1664
	21st to end	Day	7% 16% 6% 11% 7% 5% 4 3 5% 7% 29%	1522
March	1st to 10th	Day	8% 11% 4 8% 6% 5% 4 3 5% 6% 39%	3118
	11th to 20th	Day	5% 13% 9% 12% 6% 5% 4 3 5% 6% 33%	3466
	21st to end	Day	16% 16% 5% 13% 5% 5% 3 3 4 5% 27%	4032
April	1st to 10th	Day	13% 14% 4 11% 6% 5% 5% 4 5% 5% 28%	2280
	11th to 20th	Day	18% 14% 4 9% 5% 4 4 3 5% 6% 30%	2254
	21st to end	Day	18% 12% 4 8% 5% 5% 4 3 4 5% 32%	2550
May	1st to 10th	Day	18% 11% 2 7% 5% 4 3 3 4 6% 37%	4428
	11th to 20th	Day	16% 8% 3 7% 5% 4 5% 4 6% 7% 35%	4399
	21st to end	Day	19% 9% 3 6% 4 4 4 3 5% 6% 37%	4837
June	1st to 10th	Day	16% 6% 2 6% 5% 4 5% 4 6% 7% 38%	2660
	11th to 20th	Day	16% 7% 3 6% 5% 5% 5% 4 7% 8% 34%	2800
	21st to end	Day	18% 7% 2 6% 5% 4 4 5% 7% 8% 34%	2850
July	1st to 10th	Day	9% 7% 3 8% 6% 6% 5% 5% 8% 9% 36%	4702
	11th to 20th	Day	11% 5% 2 5% 4 4 4 5% 7% 10% 43%	4440
	21st to end	Day	11% 6% 2 6% 5% 4 5% 4 6% 9% 42%	4814
August	1st to 10th	Day	14% 7% 3 7% 5% 5% 6% 5% 6% 8% 35%	4423
	11th to 20th	Day	14% 4 2 4 3 3 5% 4 6% 9% 45%	4133
	21st to end	Day	12% 7% 2 7% 4 4 4 4 7% 9% 40%	4258
September	1st to 10th	Day	15% 6% 2 6% 5% 5% 4 3 6% 7% 41%	2280
	11th to 20th	Day	15% 8% 3 6% 5% 4 5% 3 5% 8% 38%	2280
	21st to end	Day	19% 10% 4 7% 4 4 3 3 4 7% 35%	2018
October	1st to 10th	Day	17% 14% 3 7% 5% 4 4 4 6% 7% 30%	1900
	11th to 20th	Day	18% 19% 5% 8% 5% 4 5% 3 4 6% 24%	1900
	21st to end	Day	19% 21% 5% 9% 4 3 2 3 4 4 27%	1887
November	1st to 10th	Day	14% 20% 6% 11% 5% 5% 4 3 4 5% 22%	1613
	11th to 20th	Day	14% 18% 6% 15% 8% 6% 4 3 5% 4 18%	1520
	21st to end	Day	15% 17% 6% 16% 8% 6% 5% 3 4 4 17%	1520
December	1st to 10th	Day	7% 16% 6% 16% 12% 8% 6% 4 5% 5% 15%	1520
	11th to 20th	Day	10% 17% 8% 14% 7% 7% 6% 5% 5% 4 19%	1914
	21st to end	Day	20% 22% 7% 12% 9% 4 3 3 3 3 14%	2783
January	1st to 10th	Night	9% 16% 6% 15% 8% 5% 6% 5% 6% 5% 20%	4428
	11th to 20th	Night	6% 10% 6% 17% 11% 10% 9% 7% 5% 4 13%	4440
	21st to end	Night	7% 18% 12% 17% 8% 5% 5% 5% 5% 5% 13%	4884
February	1st to 10th	Night	7% 11% 6% 11% 7% 8% 10% 6% 6% 6% 22%	2489
	11th to 20th	Night	8% 11% 4 11% 7% 7% 8% 5% 6% 6% 28%	2403
	21st to end	Night	6% 14% 6% 13% 8% 6% 5% 4 5% 6% 25%	1931
March	1st to 10th	Night	9% 12% 3 10% 6% 6% 5% 3 4 6% 34%	3722
	11th to 20th	Night	8% 14% 5% 13% 7% 6% 5% 3 4 6% 29%	3523
	21st to end	Night	17% 15% 3 12% 5% 4 4 3 5% 6% 25%	3599
April	1st to 10th	Night	14% 14% 4 8% 4 5% 5% 4 6% 6% 30%	1900
	11th to 20th	Night	16% 13% 4 7% 5% 4 4 4 6% 6% 31%	1875
	21st to end	Night	18% 12% 4 8% 5% 4 4 4 5% 4 32%	1625
May	1st to 10th	Night	17% 10% 3 5% 4 4 4 4 5% 7% 37%	2523
	11th to 20th	Night	13% 9% 3 7% 5% 5% 4 4 5% 6% 38%	2506
	21st to end	Night	20% 7% 2 6% 4 3 4 4 5% 7% 39%	2750
June	1st to 10th	Night	17% 9% 3 5% 5% 3 4 4 6% 7% 38%	1520
	11th to 20th	Night	12% 6% 3 5% 5% 4 5% 4 7% 8% 41%	1375
	21st to end	Night	14% 6% 2 5% 4 4 6% 4 7% 8% 41%	1330
July	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 7% 10% 46%	2251
	11th to 20th	Night	9% 6% 2 5% 4 4 4 3 6% 8% 49%	2530
	21st to end	Night	9% 5% 2 5% 4 3 4 4 5% 9% 50%	2750
August	1st to 10th	Night	17% 4 1 5% 4 4 4 4 7% 9% 42%	2517
	11th to 20th	Night	12% 5% 2 5% 4 3 4 4 6% 8% 47%	2702
	21st to end	Night	15% 7% 3 6% 4 3 4 3 5% 7% 44%	3400
September	1st to 10th	Night	13% 6% 2 5% 4 4 5% 3 5% 6% 45%	1900
	11th to 20th	Night	14% 6% 2 5% 4 4 4 3 5% 7% 46%	1900
	21st to end	Night	21% 10% 2 6% 4 3 3 2 4 6% 38%	2138
October	1st to 10th	Night	18% 11% 3 6% 4 4 4 4 4 7% 34%	2280
	11th to 20th	Night	17% 18% 4 8% 4 4 4 3 4 5% 29%	2280
	21st to end	Night	20% 16% 4 9% 5% 3 4 3 5% 6% 25%	2710
November	1st to 10th	Night	14% 19% 6% 10% 6% 4 4 3 5% 7% 23%	2565
	11th to 20th	Night	14% 16% 8% 15% 7% 5% 4 3 4 5% 18%	2660
	21st to end	Night	12% 15% 7% 17% 10% 6% 5% 3 4 5% 18%	2660
December	1st to 10th	Night	10% 17% 6% 17% 11% 7% 5% 4 5% 4 14%	2660
	11th to 20th	Night	9% 16% 6% 13% 9% 8% 6% 6% 5% 5% 17%	3283
	21st to end	Night	20% 23% 7% 13% 6% 4 4 3 4 3 13%	4884

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	47% 36% 4 7% 6%	2528
	11th to 20th	Day	41% 36% 5% 15% 2	2530
	21st to end	Day	50% 39% 4 6% 1	2783
February	1st to 10th	Day	23% 65% 3 6% 3	1690
	11th to 20th	Day	22% 64% 3 8% 3	1673
	21st to end	Day	20% 65% 3 6% 6%	1522
March	1st to 10th	Day	25% 42% 5% 15% 12% 1	3120
	11th to 20th	Day	33% 40% 7% 14% 6%	3466
	21st to end	Day	39% 40% 2 11% 8% 1	4032
April	1st to 10th	Day	21% 65% 2 6% 5% 1	2280
	11th to 20th	Day	19% 65% 3 8% 4	2254
	21st to end	Day	20% 64% 3 8% 4 1	2550
May	1st to 10th	Day	28% 41% 6% 13% 12% 1	4440
	11th to 20th	Day	29% 41% 8% 16% 7% 1	4403
	21st to end	Day	32% 40% 6% 12% 10%	4837
June	1st to 10th	Day	16% 65% 6% 7% 5% 1	2660
	11th to 20th	Day	18% 66% 4 8% 4	2800
	21st to end	Day	18% 65% 5% 8% 3	2850
July	1st to 10th	Day	30% 41% 12% 14% 4	4629
	11th to 20th	Day	20% 39% 14% 21% 5%	4365
	21st to end	Day	23% 37% 11% 24% 6%	4662
August	1st to 10th	Day	30% 40% 10% 15% 5%	4408
	11th to 20th	Day	20% 40% 16% 22% 2	4175
	21st to end	Day	27% 39% 13% 17% 3	4257
September	1st to 10th	Day	18% 60% 7% 10% 4	2280
	11th to 20th	Day	18% 61% 10% 8% 2	2280
	21st to end	Day	23% 59% 5% 9% 3 1	2018
October	1st to 10th	Day	25% 38% 12% 16% 8% 1	3160
	11th to 20th	Day	30% 37% 9% 18% 5%	3140
	21st to end	Day	39% 39% 10% 12% 1	3087
November	1st to 10th	Day	32% 57% 4 5% 2	1613
	11th to 20th	Day	28% 60% 4 6% 2	1520
	21st to end	Day	32% 60% 3 3 3	1520
December	1st to 10th	Day	30% 60% 4 5% 2	1520
	11th to 20th	Day	34% 48% 7% 6% 4 1	1915
	21st to end	Day	49% 36% 3 9% 3	2783
January	1st to 10th	Night	43% 36% 5% 11% 4	4428
	11th to 20th	Night	46% 37% 7% 9% 2	4440
	21st to end	Night	47% 40% 5% 6% 1	4884
February	1st to 10th	Night	22% 65% 4 5% 3	2489
	11th to 20th	Night	22% 64% 5% 6% 2 1	2404
	21st to end	Night	22% 64% 2 6% 4	1931
March	1st to 10th	Night	28% 42% 7% 10% 12% 2	3733
	11th to 20th	Night	37% 40% 7% 11% 4 1	3524
	21st to end	Night	40% 40% 3 9% 8% 1	3599
April	1st to 10th	Night	21% 65% 3 4 6% 1	1900
	11th to 20th	Night	19% 65% 3 7% 4 1	1875
	21st to end	Night	18% 64% 3 10% 5%	1625
May	1st to 10th	Night	26% 41% 7% 16% 10%	2530
	11th to 20th	Night	29% 41% 7% 14% 7% 3	2507
	21st to end	Night	28% 41% 9% 15% 6% 2	2751
June	1st to 10th	Night	16% 64% 5% 9% 6% 1	1520
	11th to 20th	Night	15% 65% 4 10% 6%	1375
	21st to end	Night	16% 65% 6% 9% 4 1	1330
July	1st to 10th	Night	22% 41% 16% 15% 5%	2215
	11th to 20th	Night	17% 39% 15% 24% 4	2482
	21st to end	Night	19% 37% 10% 27% 7%	2662
August	1st to 10th	Night	25% 39% 11% 18% 6%	2508
	11th to 20th	Night	22% 40% 14% 22% 2	2726
	21st to end	Night	27% 39% 12% 19% 3	3400
September	1st to 10th	Night	18% 60% 7% 11% 4	1900
	11th to 20th	Night	14% 62% 11% 10% 2	1900
	21st to end	Night	20% 60% 6% 10% 3 1	2138
October	1st to 10th	Night	20% 37% 7% 24% 11%	3800
	11th to 20th	Night	31% 38% 7% 16% 8%	3779
	21st to end	Night	40% 38% 11% 9% 2	4460
November	1st to 10th	Night	30% 57% 5% 7% 1	2565
	11th to 20th	Night	29% 59% 5% 5% 2	2660
	21st to end	Night	31% 59% 3 5% 2	2660
December	1st to 10th	Night	31% 59% 4 5% 2	2660
	11th to 20th	Night	34% 49% 5% 8% 4	3281
	21st to end	Night	49% 37% 3 8% 4	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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	17% 20% 37% 21% 5%	270
	11th to 20th	Day	16% 18% 42% 20% 5%	270
	21st to end	Day	15% 23% 40% 18% 4	297
February	1st to 10th	Day	16% 23% 43% 12% 4 2	270
	11th to 20th	Day	19% 27% 36% 11% 6% 1	270
	21st to end	Day	19% 29% 40% 10% 2	225
March	1st to 10th	Day	14% 22% 43% 17% 4	270
	11th to 20th	Day	17% 25% 37% 14% 7% 1	270
	21st to end	Day	24% 21% 32% 14% 7% 1	425
April	1st to 10th	Day	23% 18% 34% 18% 6%	460
	11th to 20th	Day	26% 20% 28% 19% 7%	452
	21st to end	Day	27% 17% 30% 19% 7% 1	612
May	1st to 10th	Day	24% 21% 33% 16% 4 2	653
	11th to 20th	Day	20% 17% 36% 18% 6% 3	675
	21st to end	Day	24% 16% 32% 21% 6% 2	734
June	1st to 10th	Day	22% 18% 31% 18% 9% 2	680
	11th to 20th	Day	20% 18% 37% 17% 5% 2	680
	21st to end	Day	21% 16% 32% 20% 8% 3	680
July	1st to 10th	Day	11% 11% 38% 24% 12% 4	671
	11th to 20th	Day	15% 15% 32% 23% 12% 4	668
	21st to end	Day	13% 12% 34% 23% 12% 6%	739
August	1st to 10th	Day	16% 11% 35% 24% 12% 3	676
	11th to 20th	Day	16% 10% 27% 29% 14% 4	665
	21st to end	Day	19% 13% 30% 25% 11% 2	591
September	1st to 10th	Day	18% 11% 33% 26% 11% 1	490
	11th to 20th	Day	19% 14% 33% 21% 11% 1	490
	21st to end	Day	28% 19% 25% 19% 8% 2	410
October	1st to 10th	Day	25% 19% 32% 16% 5% 3	300
	11th to 20th	Day	27% 20% 39% 11% 3	300
	21st to end	Day	32% 27% 29% 9% 2	330
November	1st to 10th	Day	28% 22% 31% 15% 3 1	282
	11th to 20th	Day	23% 27% 36% 10% 3 1	270
	21st to end	Day	29% 20% 36% 12% 3 1	270
December	1st to 10th	Day	20% 21% 37% 18% 3	270
	11th to 20th	Day	22% 20% 39% 17% 2	270
	21st to end	Day	21% 18% 43% 13% 3 2	297
January	1st to 10th	Night	16% 19% 42% 19% 4	950
	11th to 20th	Night	16% 20% 41% 18% 5% 1	950
	21st to end	Night	18% 17% 40% 20% 4	1045
February	1st to 10th	Night	15% 18% 39% 21% 7% 1	950
	11th to 20th	Night	15% 21% 35% 22% 7% 1	929
	21st to end	Night	16% 17% 37% 22% 7%	675
March	1st to 10th	Night	15% 18% 34% 26% 6% 1	760
	11th to 20th	Night	16% 18% 36% 23% 6%	601
	21st to end	Night	22% 11% 31% 25% 10% 2	627
April	1st to 10th	Night	21% 13% 36% 25% 6%	570
	11th to 20th	Night	22% 15% 32% 23% 7%	563
	21st to end	Night	25% 11% 31% 25% 8% 1	570
May	1st to 10th	Night	22% 14% 34% 25% 5% 1	570
	11th to 20th	Night	19% 13% 33% 26% 8% 1	561
	21st to end	Night	21% 9% 32% 30% 8% 1	617
June	1st to 10th	Night	21% 10% 30% 28% 10% 1	570
	11th to 20th	Night	16% 10% 37% 29% 8%	570
	21st to end	Night	15% 10% 29% 32% 12% 1	570
July	1st to 10th	Night	11% 5% 30% 37% 16% 1	555
	11th to 20th	Night	13% 8% 32% 32% 14% 1	552
	21st to end	Night	9% 6% 32% 34% 17% 2	624
August	1st to 10th	Night	12% 5% 32% 37% 13% 1	567
	11th to 20th	Night	15% 8% 22% 32% 20% 3	564
	21st to end	Night	14% 10% 29% 31% 16%	627
September	1st to 10th	Night	18% 8% 27% 32% 14% 1	570
	11th to 20th	Night	17% 9% 32% 28% 14% 1	570
	21st to end	Night	27% 11% 29% 24% 8% 2	732
October	1st to 10th	Night	26% 15% 30% 21% 7% 1	760
	11th to 20th	Night	30% 15% 32% 18% 4 1	760
	21st to end	Night	28% 15% 33% 20% 4	836
November	1st to 10th	Night	24% 17% 32% 21% 4 1	855
	11th to 20th	Night	24% 19% 34% 17% 6% 1	950
	21st to end	Night	21% 22% 38% 15% 4	950
December	1st to 10th	Night	17% 20% 38% 20% 5%	950
	11th to 20th	Night	20% 19% 35% 19% 6% 1	950
	21st to end	Night	25% 17% 35% 17% 6%	1045

Page generated at 2024-11-03 01:11:14. Version ac07

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