Beaver Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Beaver Island clear sky chart from 2005-11-06 to 2026-04-02.

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	22% 11% 3 8% 5% 4 4 4 5% 6% 28%	131826
	Night	23% 11% 3 7% 4 4 4 3 5% 6% 29%	130236
Transparency	Day	55% 7% 11% 18% 9% 1	135359
	Night	56% 6% 11% 18% 9% 1	134795
Seeing	Day	27% 10% 27% 25% 9% 1	19346
	Night	28% 11% 28% 23% 9% 1	27104

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	13% 11% 4 12% 6% 6% 6% 4 6% 8% 25%	4690
	11th to 20th	Day	19% 11% 5% 12% 7% 5% 4 4 5% 6% 23%	4681
	21st to end	Day	13% 9% 3 8% 5% 5% 6% 5% 7% 8% 32%	5684
February	1st to 10th	Day	21% 11% 4 7% 5% 5% 6% 5% 5% 6% 25%	1890
	11th to 20th	Day	17% 10% 4 9% 6% 4 5% 5% 5% 5% 29%	1843
	21st to end	Day	14% 12% 4 6% 5% 4 5% 4 6% 6% 34%	1667
March	1st to 10th	Day	19% 12% 4 10% 5% 5% 4 4 5% 5% 28%	4804
	11th to 20th	Day	17% 14% 4 7% 4 4 4 4 6% 7% 30%	5090
	21st to end	Day	29% 9% 3 9% 5% 5% 5% 3 5% 5% 22%	5741
April	1st to 10th	Day	27% 9% 3 6% 4 5% 5% 4 4 6% 29%	2412
	11th to 20th	Day	24% 9% 3 7% 3 4 4 3 5% 6% 31%	2374
	21st to end	Day	25% 10% 3 6% 5% 4 4 3 5% 5% 31%	2566
May	1st to 10th	Day	30% 14% 4 7% 4 4 4 3 5% 5% 20%	6248
	11th to 20th	Day	25% 11% 3 7% 5% 4 4 3 5% 5% 27%	6318
	21st to end	Day	23% 13% 3 8% 5% 4 4 3 5% 6% 25%	6948
June	1st to 10th	Day	30% 10% 3 7% 4 4 4 4 5% 7% 22%	2800
	11th to 20th	Day	24% 10% 2 7% 5% 4 4 4 5% 6% 30%	2800
	21st to end	Day	34% 13% 4 7% 4 4 4 3 4 4 20%	2800
July	1st to 10th	Day	26% 13% 4 9% 6% 5% 4 4 5% 6% 18%	6360
	11th to 20th	Day	25% 16% 4 7% 5% 4 4 3 4 6% 22%	6360
	21st to end	Day	17% 11% 3 8% 5% 4 4 3 5% 7% 33%	6927
August	1st to 10th	Day	25% 12% 4 9% 4 4 4 4 5% 6% 24%	4278
	11th to 20th	Day	19% 9% 3 6% 4 4 4 4 7% 9% 29%	4175
	21st to end	Day	12% 7% 2 6% 4 4 4 4 4 7% 46%	4358
September	1st to 10th	Day	18% 8% 2 6% 4 4 4 3 5% 7% 38%	2400
	11th to 20th	Day	20% 7% 2 5% 4 3 4 4 7% 7% 38%	2400
	21st to end	Day	19% 7% 2 5% 4 5% 4 4 5% 7% 37%	2099
October	1st to 10th	Day	17% 6% 2 6% 5% 6% 4 4 7% 7% 36%	2000
	11th to 20th	Day	20% 8% 3 6% 4 4 4 4 6% 7% 34%	2000
	21st to end	Day	23% 8% 3 6% 5% 4 4 4 5% 8% 29%	2130
November	1st to 10th	Day	23% 8% 3 7% 4 4 4 3 6% 6% 31%	1787
	11th to 20th	Day	23% 11% 2 7% 4 5% 5% 4 5% 6% 28%	1680
	21st to end	Day	19% 10% 3 8% 6% 5% 4 4 7% 8% 27%	1680
December	1st to 10th	Day	19% 11% 4 9% 5% 5% 4 4 5% 6% 29%	2690
	11th to 20th	Day	28% 10% 3 5% 4 4 4 3 5% 5% 29%	3076
	21st to end	Day	20% 11% 6% 10% 4 4 4 3 4 5% 30%	4070
January	1st to 10th	Night	14% 14% 4 9% 6% 5% 4 4 6% 7% 27%	8234
	11th to 20th	Night	23% 12% 5% 11% 5% 5% 5% 4 5% 5% 20%	8234
	21st to end	Night	12% 11% 4 8% 5% 5% 5% 4 7% 7% 30%	8485
February	1st to 10th	Night	22% 11% 4 9% 5% 5% 5% 4 6% 7% 23%	2730
	11th to 20th	Night	18% 11% 4 9% 6% 5% 5% 4 6% 6% 27%	2663
	21st to end	Night	14% 13% 5% 10% 6% 4 4 4 5% 7% 30%	2139
March	1st to 10th	Night	24% 12% 4 10% 6% 5% 4 3 4 5% 23%	5254
	11th to 20th	Night	23% 13% 4 6% 5% 4 4 3 5% 6% 29%	5089
	21st to end	Night	32% 10% 4 8% 4 3 3 2 3 4 26%	5432
April	1st to 10th	Night	28% 11% 3 6% 4 4 3 3 5% 6% 27%	2011
	11th to 20th	Night	25% 8% 2 6% 4 5% 4 4 4 6% 33%	1976
	21st to end	Night	26% 9% 3 5% 4 3 3 3 5% 6% 31%	1830
May	1st to 10th	Night	33% 15% 4 7% 4 3 4 3 4 5% 19%	3708
	11th to 20th	Night	29% 13% 3 6% 4 3 4 3 4 5% 28%	3596
	21st to end	Night	23% 18% 4 6% 3 2 4 3 4 7% 26%	3948
June	1st to 10th	Night	32% 13% 3 5% 3 3 3 3 4 7% 24%	1600
	11th to 20th	Night	26% 9% 3 6% 4 4 4 3 5% 6% 31%	1600
	21st to end	Night	34% 14% 4 7% 3 4 3 2 3 4 21%	1600
July	1st to 10th	Night	29% 17% 4 7% 4 3 4 3 4 6% 20%	3619
	11th to 20th	Night	29% 20% 3 6% 4 2 3 2 3 5% 23%	3620
	21st to end	Night	23% 13% 2 5% 3 3 4 3 5% 6% 32%	3948
August	1st to 10th	Night	30% 12% 3 6% 3 3 3 3 4 6% 28%	2871
	11th to 20th	Night	19% 12% 3 7% 4 4 3 4 6% 8% 29%	2872
	21st to end	Night	16% 6% 1 4 3 3 3 4 5% 7% 48%	3538
September	1st to 10th	Night	19% 8% 2 5% 3 3 4 4 4 8% 40%	2000
	11th to 20th	Night	20% 6% 2 5% 3 3 4 4 5% 7% 41%	2000
	21st to end	Night	21% 8% 4 6% 4 4 4 2 5% 7% 37%	2297
October	1st to 10th	Night	18% 5% 2 6% 4 4 5% 3 6% 7% 40%	2400
	11th to 20th	Night	22% 7% 2 5% 4 4 4 3 5% 7% 37%	2400
	21st to end	Night	25% 8% 2 6% 4 4 4 3 5% 6% 32%	2710
November	1st to 10th	Night	21% 9% 3 7% 5% 4 4 4 5% 6% 33%	2729
	11th to 20th	Night	22% 11% 3 7% 5% 5% 4 3 5% 6% 29%	2940
	21st to end	Night	21% 12% 3 7% 5% 5% 4 3 5% 7% 28%	2940
December	1st to 10th	Night	18% 10% 3 8% 5% 5% 4 3 5% 6% 32%	4720
	11th to 20th	Night	27% 10% 3 7% 4 4 4 3 4 6% 29%	5353
	21st to end	Night	25% 10% 3 7% 4 4 4 3 5% 6% 28%	7150

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	56% 9% 13% 17% 5%	4691
	11th to 20th	Day	58% 7% 11% 17% 6% 1	4710
	21st to end	Day	48% 8% 10% 16% 15% 3	5684
February	1st to 10th	Day	59% 7% 11% 12% 10% 1	1890
	11th to 20th	Day	55% 8% 11% 16% 8% 2	1851
	21st to end	Day	49% 7% 12% 19% 11% 3	1667
March	1st to 10th	Day	56% 5% 9% 13% 11% 5%	4808
	11th to 20th	Day	50% 10% 15% 18% 6% 1	5090
	21st to end	Day	61% 6% 8% 16% 8% 2	5741
April	1st to 10th	Day	53% 7% 9% 15% 12% 2	2412
	11th to 20th	Day	52% 6% 9% 19% 13% 1	2374
	21st to end	Day	54% 5% 11% 17% 10% 2	2566
May	1st to 10th	Day	66% 6% 9% 13% 5%	6260
	11th to 20th	Day	56% 8% 10% 19% 7%	6322
	21st to end	Day	56% 8% 11% 18% 7%	6948
June	1st to 10th	Day	60% 8% 10% 15% 6%	2800
	11th to 20th	Day	55% 6% 10% 18% 10% 1	2800
	21st to end	Day	69% 5% 6% 12% 8% 1	2800
July	1st to 10th	Day	67% 6% 10% 10% 7%	6290
	11th to 20th	Day	64% 6% 7% 16% 7%	6284
	21st to end	Day	50% 7% 13% 21% 9%	6730
August	1st to 10th	Day	61% 6% 9% 17% 6%	4264
	11th to 20th	Day	48% 9% 14% 23% 6%	4214
	21st to end	Day	37% 7% 13% 28% 15%	4358
September	1st to 10th	Day	45% 6% 12% 22% 13% 2	2400
	11th to 20th	Day	43% 6% 13% 24% 13% 1	2400
	21st to end	Day	45% 8% 9% 23% 14%	2099
October	1st to 10th	Day	45% 8% 11% 25% 11% 1	3260
	11th to 20th	Day	37% 7% 12% 28% 15%	3240
	21st to end	Day	47% 6% 15% 20% 11% 2	3424
November	1st to 10th	Day	52% 7% 12% 19% 9% 1	1787
	11th to 20th	Day	56% 6% 12% 16% 8% 1	1680
	21st to end	Day	56% 6% 16% 14% 7% 1	1680
December	1st to 10th	Day	55% 7% 12% 21% 5%	2690
	11th to 20th	Day	59% 4 12% 12% 12%	3075
	21st to end	Day	58% 4 14% 15% 9%	4070
January	1st to 10th	Night	57% 7% 15% 17% 4	8234
	11th to 20th	Night	64% 7% 10% 14% 5%	8280
	21st to end	Night	51% 7% 11% 17% 12% 1	8485
February	1st to 10th	Night	61% 7% 12% 11% 8% 1	2730
	11th to 20th	Night	58% 6% 13% 14% 8% 2	2666
	21st to end	Night	54% 4 13% 18% 8% 1	2139
March	1st to 10th	Night	63% 5% 7% 13% 10% 2	5263
	11th to 20th	Night	56% 6% 13% 17% 8% 1	5090
	21st to end	Night	63% 4 7% 18% 8% 1	5432
April	1st to 10th	Night	58% 6% 9% 15% 11% 2	2011
	11th to 20th	Night	51% 6% 9% 19% 13% 2	1976
	21st to end	Night	54% 5% 9% 18% 12% 2	1830
May	1st to 10th	Night	66% 6% 7% 14% 6% 1	3713
	11th to 20th	Night	58% 6% 9% 19% 7% 1	3597
	21st to end	Night	58% 6% 11% 19% 5%	3949
June	1st to 10th	Night	61% 5% 8% 18% 7%	1600
	11th to 20th	Night	54% 5% 10% 17% 14%	1600
	21st to end	Night	69% 4 7% 13% 6% 1	1600
July	1st to 10th	Night	67% 5% 8% 13% 6% 1	3581
	11th to 20th	Night	65% 5% 7% 15% 8% 1	3572
	21st to end	Night	52% 6% 12% 21% 9%	3831
August	1st to 10th	Night	58% 5% 12% 20% 5%	2860
	11th to 20th	Night	51% 8% 15% 21% 5%	2899
	21st to end	Night	35% 7% 15% 28% 15%	3537
September	1st to 10th	Night	44% 6% 11% 24% 13% 1	2000
	11th to 20th	Night	43% 5% 12% 25% 14% 1	2000
	21st to end	Night	48% 5% 9% 25% 12% 1	2297
October	1st to 10th	Night	47% 7% 14% 22% 11%	3920
	11th to 20th	Night	36% 6% 12% 29% 16%	3899
	21st to end	Night	46% 6% 14% 22% 12%	4370
November	1st to 10th	Night	52% 8% 12% 18% 9%	2729
	11th to 20th	Night	56% 6% 13% 14% 9% 1	2940
	21st to end	Night	58% 6% 15% 14% 6%	2940
December	1st to 10th	Night	52% 7% 13% 22% 7%	4720
	11th to 20th	Night	57% 5% 11% 16% 9% 1	5355
	21st to end	Night	58% 5% 12% 16% 8%	7150

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	23% 22% 33% 19% 4	430
	11th to 20th	Day	27% 18% 31% 17% 7%	430
	21st to end	Day	21% 15% 38% 22% 4	473
February	1st to 10th	Day	27% 17% 33% 18% 4 1	430
	11th to 20th	Day	23% 18% 36% 19% 4	426
	21st to end	Day	21% 12% 40% 21% 5%	355
March	1st to 10th	Day	22% 15% 39% 21% 3	483
	11th to 20th	Day	22% 15% 32% 25% 5%	540
	21st to end	Day	27% 14% 35% 18% 5% 1	594
April	1st to 10th	Day	31% 13% 34% 19% 3	504
	11th to 20th	Day	30% 11% 35% 18% 6% 1	492
	21st to end	Day	26% 9% 28% 28% 7% 2	500
May	1st to 10th	Day	33% 9% 29% 21% 6% 2	658
	11th to 20th	Day	28% 5% 27% 31% 6% 2	724
	21st to end	Day	33% 8% 24% 27% 7% 1	790
June	1st to 10th	Day	34% 6% 22% 28% 10% 1	730
	11th to 20th	Day	27% 6% 22% 34% 10% 1	730
	21st to end	Day	40% 4 17% 26% 11% 1	730
July	1st to 10th	Day	33% 4 17% 31% 13% 1	720
	11th to 20th	Day	35% 4 15% 30% 15% 1	718
	21st to end	Day	32% 4 17% 33% 13% 2	795
August	1st to 10th	Day	22% 4 21% 33% 17% 3	556
	11th to 20th	Day	26% 5% 22% 27% 17% 3	519
	21st to end	Day	21% 6% 22% 31% 16% 4	583
September	1st to 10th	Day	22% 6% 24% 29% 17% 2	530
	11th to 20th	Day	22% 8% 24% 28% 14% 3	530
	21st to end	Day	23% 5% 27% 27% 16% 2	456
October	1st to 10th	Day	20% 9% 28% 26% 15% 3	420
	11th to 20th	Day	20% 10% 29% 25% 15% 2	420
	21st to end	Day	26% 12% 33% 20% 8% 1	462
November	1st to 10th	Day	23% 14% 32% 24% 5% 2	425
	11th to 20th	Day	30% 17% 30% 15% 6%	430
	21st to end	Day	24% 18% 36% 17% 6%	430
December	1st to 10th	Day	27% 16% 33% 21% 3	430
	11th to 20th	Day	31% 22% 30% 15% 2	430
	21st to end	Day	25% 19% 32% 19% 5%	473
January	1st to 10th	Night	28% 17% 34% 18% 3	950
	11th to 20th	Night	29% 17% 33% 17% 4	950
	21st to end	Night	21% 19% 39% 17% 4	940
February	1st to 10th	Night	28% 17% 32% 20% 3	840
	11th to 20th	Night	24% 19% 37% 16% 3	823
	21st to end	Night	20% 14% 38% 21% 7%	692
March	1st to 10th	Night	23% 16% 39% 19% 3	840
	11th to 20th	Night	25% 13% 29% 25% 8%	840
	21st to end	Night	28% 13% 31% 22% 7%	859
April	1st to 10th	Night	33% 11% 28% 22% 5%	604
	11th to 20th	Night	28% 8% 30% 26% 7% 1	594
	21st to end	Night	31% 7% 25% 29% 8% 1	600
May	1st to 10th	Night	37% 5% 26% 21% 9% 2	600
	11th to 20th	Night	32% 5% 22% 27% 12% 3	592
	21st to end	Night	30% 5% 25% 29% 9% 1	649
June	1st to 10th	Night	38% 5% 20% 28% 9% 1	600
	11th to 20th	Night	32% 3 18% 35% 11% 1	600
	21st to end	Night	40% 3 18% 25% 13% 1	600
July	1st to 10th	Night	33% 3 15% 33% 15% 1	586
	11th to 20th	Night	35% 4 14% 28% 18% 1	582
	21st to end	Night	36% 4 14% 27% 18% 1	656
August	1st to 10th	Night	27% 4 14% 33% 20% 2	598
	11th to 20th	Night	25% 3 18% 32% 20% 2	592
	21st to end	Night	23% 3 18% 31% 22% 3	660
September	1st to 10th	Night	23% 3 23% 31% 18% 2	600
	11th to 20th	Night	24% 5% 23% 29% 18% 2	600
	21st to end	Night	24% 7% 26% 29% 12% 2	763
October	1st to 10th	Night	21% 7% 29% 30% 12% 2	800
	11th to 20th	Night	25% 10% 29% 25% 10% 2	800
	21st to end	Night	30% 12% 32% 20% 6%	919
November	1st to 10th	Night	26% 13% 31% 23% 5% 1	930
	11th to 20th	Night	29% 18% 28% 19% 7%	950
	21st to end	Night	29% 16% 32% 18% 4	950
December	1st to 10th	Night	30% 16% 33% 17% 5%	950
	11th to 20th	Night	30% 20% 33% 14% 2	950
	21st to end	Night	28% 17% 33% 17% 4 1	1045

Page generated at 2026-03-30 03:18:45. Version ac07

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