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 2025-10-04.

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	14% 10% 4 10% 5% 4 4 3 5% 6% 34%	125964
	Night	15% 13% 5% 12% 6% 5% 4 3 4 6% 28%	123621
Transparency	Day	49% 7% 12% 21% 10% 1	129431
	Night	56% 7% 11% 17% 8% 1	128228
Seeing	Day	16% 6% 19% 32% 22% 6%	16961
	Night	20% 7% 24% 30% 16% 3	26530

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	11% 14% 11% 33% 8% 5% 4 3 2 3 7%	3617
	11th to 20th	Day	14% 14% 7% 24% 15% 9% 3 2 3 3 5%	3589
	21st to end	Day	12% 20% 7% 19% 10% 5% 6% 3 3 5% 10%	3982
February	1st to 10th	Day	8% 14% 6% 13% 11% 6% 4 4 7% 7% 21%	1676
	11th to 20th	Day	12% 15% 5% 11% 10% 6% 5% 4 5% 6% 20%	1928
	21st to end	Day	12% 12% 5% 10% 8% 6% 6% 5% 5% 5% 25%	1650
March	1st to 10th	Day	13% 9% 3 10% 7% 4 4 3 5% 7% 34%	4478
	11th to 20th	Day	13% 10% 4 13% 6% 5% 5% 3 5% 7% 28%	4834
	21st to end	Day	19% 11% 6% 13% 7% 5% 4 3 4 5% 23%	5690
April	1st to 10th	Day	17% 11% 4 9% 4 4 5% 4 5% 7% 31%	2400
	11th to 20th	Day	18% 10% 4 8% 4 3 4 4 5% 6% 36%	2486
	21st to end	Day	15% 8% 3 10% 5% 5% 5% 4 5% 7% 35%	2600
May	1st to 10th	Day	13% 8% 2 7% 4 4 4 3 5% 6% 46%	5888
	11th to 20th	Day	11% 7% 3 8% 5% 4 4 4 5% 6% 44%	6178
	21st to end	Day	10% 9% 3 6% 4 4 3 3 5% 8% 46%	6949
June	1st to 10th	Day	11% 7% 2 6% 5% 4 5% 4 5% 9% 43%	2989
	11th to 20th	Day	11% 7% 3 7% 5% 4 4 4 6% 9% 41%	3000
	21st to end	Day	15% 7% 2 6% 4 4 4 4 6% 8% 41%	2984
July	1st to 10th	Day	13% 6% 2 5% 3 3 3 3 5% 8% 48%	6359
	11th to 20th	Day	8% 5% 2 4 3 3 3 3 5% 9% 54%	6360
	21st to end	Day	9% 5% 2 5% 3 4 3 4 6% 8% 51%	6926
August	1st to 10th	Day	7% 5% 2 7% 4 4 5% 5% 6% 9% 46%	4439
	11th to 20th	Day	13% 6% 2 5% 4 3 4 3 5% 7% 50%	4174
	21st to end	Day	13% 6% 2 6% 4 4 4 3 4 6% 48%	4496
September	1st to 10th	Day	16% 7% 2 5% 3 3 4 4 6% 8% 43%	2383
	11th to 20th	Day	13% 6% 2 6% 4 4 4 4 6% 8% 45%	2200
	21st to end	Day	16% 8% 2 7% 5% 3 5% 3 5% 8% 38%	2200
October	1st to 10th	Day	19% 9% 3 7% 5% 4 4 3 5% 6% 36%	2123
	11th to 20th	Day	22% 16% 4 9% 5% 5% 5% 3 4 5% 22%	1776
	21st to end	Day	25% 16% 4 10% 5% 5% 4 3 5% 5% 18%	1881
November	1st to 10th	Day	19% 17% 5% 9% 4 4 4 3 5% 6% 24%	1762
	11th to 20th	Day	17% 20% 8% 12% 6% 5% 4 4 4 4 16%	1800
	21st to end	Day	20% 23% 9% 12% 6% 4 3 3 4 4 12%	1560
December	1st to 10th	Day	17% 27% 10% 18% 6% 5% 4 2 3 3 6%	2280
	11th to 20th	Day	17% 23% 7% 17% 8% 6% 4 3 4 3 8%	2621
	21st to end	Day	26% 25% 9% 14% 7% 3 3 2 2 2 7%	3706
January	1st to 10th	Night	11% 16% 8% 30% 8% 5% 4 2 3 3 10%	6348
	11th to 20th	Night	11% 18% 7% 21% 14% 6% 4 3 3 3 9%	6316
	21st to end	Night	11% 16% 8% 18% 8% 7% 5% 3 4 4 15%	6996
February	1st to 10th	Night	9% 16% 6% 12% 9% 8% 6% 4 5% 5% 21%	2722
	11th to 20th	Night	10% 15% 5% 13% 9% 5% 5% 3 5% 7% 22%	2357
	21st to end	Night	13% 16% 4 12% 7% 5% 5% 4 5% 5% 24%	1980
March	1st to 10th	Night	16% 10% 3 7% 6% 4 3 3 4 7% 37%	5362
	11th to 20th	Night	11% 11% 5% 10% 6% 5% 5% 4 5% 7% 32%	5123
	21st to end	Night	21% 11% 5% 9% 5% 4 3 4 5% 6% 28%	5284
April	1st to 10th	Night	18% 11% 3 8% 5% 5% 4 3 5% 6% 30%	2000
	11th to 20th	Night	19% 9% 4 8% 4 4 4 3 5% 5% 35%	1862
	21st to end	Night	16% 8% 4 9% 5% 4 4 3 5% 5% 36%	1800
May	1st to 10th	Night	15% 7% 2 7% 4 4 4 3 5% 6% 43%	4053
	11th to 20th	Night	14% 8% 3 8% 6% 4 4 3 5% 6% 39%	3728
	21st to end	Night	17% 8% 2 6% 4 3 3 3 5% 6% 42%	3949
June	1st to 10th	Night	13% 5% 2 7% 5% 4 4 4 6% 9% 39%	1409
	11th to 20th	Night	13% 7% 3 7% 6% 5% 4 4 7% 7% 39%	1400
	21st to end	Night	15% 7% 3 6% 4 3 3 4 5% 8% 43%	1410
July	1st to 10th	Night	13% 6% 3 7% 4 3 4 3 5% 8% 42%	3620
	11th to 20th	Night	8% 5% 3 5% 4 3 3 3 5% 7% 54%	3620
	21st to end	Night	7% 5% 2 6% 3 4 4 3 6% 9% 52%	3948
August	1st to 10th	Night	10% 7% 2 6% 4 5% 4 4 5% 8% 43%	2714
	11th to 20th	Night	13% 5% 2 5% 3 3 4 3 5% 7% 50%	2875
	21st to end	Night	11% 6% 2 5% 4 4 3 3 5% 7% 51%	3386
September	1st to 10th	Night	13% 6% 3 7% 5% 4 3 3 5% 7% 45%	2000
	11th to 20th	Night	15% 7% 2 5% 3 4 4 4 6% 7% 44%	2196
	21st to end	Night	17% 8% 3 6% 5% 4 3 3 5% 7% 39%	2200
October	1st to 10th	Night	17% 9% 2 7% 4 4 4 3 5% 6% 37%	2124
	11th to 20th	Night	22% 13% 4 8% 5% 4 5% 4 5% 6% 25%	2402
	21st to end	Night	27% 14% 4 9% 5% 4 4 3 4 5% 21%	2717
November	1st to 10th	Night	18% 14% 5% 8% 5% 4 4 3 5% 6% 28%	2536
	11th to 20th	Night	18% 19% 6% 13% 6% 5% 4 3 4 4 18%	2600
	21st to end	Night	19% 23% 9% 12% 6% 4 4 3 4 4 12%	2834
December	1st to 10th	Night	15% 24% 9% 16% 6% 5% 5% 3 5% 4 9%	4910
	11th to 20th	Night	16% 21% 7% 20% 9% 5% 4 3 4 4 9%	5586
	21st to end	Night	24% 21% 12% 15% 6% 4 3 2 2 3 7%	7254

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	84% 6% 4 5% 1	3618
	11th to 20th	Day	83% 8% 4 3 1	3620
	21st to end	Day	76% 8% 8% 6% 2	3982
February	1st to 10th	Day	59% 9% 13% 16% 3	1676
	11th to 20th	Day	61% 9% 12% 11% 7%	1938
	21st to end	Day	57% 8% 11% 17% 7%	1650
March	1st to 10th	Day	48% 6% 16% 16% 12% 2	4480
	11th to 20th	Day	53% 7% 16% 17% 7% 1	4834
	21st to end	Day	61% 7% 10% 16% 6%	5690
April	1st to 10th	Day	51% 7% 11% 22% 9% 1	2400
	11th to 20th	Day	47% 5% 10% 23% 13% 2	2486
	21st to end	Day	47% 6% 11% 18% 14% 3	2600
May	1st to 10th	Day	39% 6% 10% 22% 21% 2	5897
	11th to 20th	Day	41% 7% 9% 26% 16% 1	6182
	21st to end	Day	35% 6% 12% 25% 17% 5%	6949
June	1st to 10th	Day	36% 8% 13% 27% 14% 2	2989
	11th to 20th	Day	38% 8% 13% 24% 16% 1	3000
	21st to end	Day	41% 7% 14% 24% 12% 2	2984
July	1st to 10th	Day	35% 5% 15% 30% 13% 1	6291
	11th to 20th	Day	27% 7% 16% 38% 11% 1	6285
	21st to end	Day	30% 7% 15% 32% 16% 1	6728
August	1st to 10th	Day	33% 8% 16% 31% 12% 1	4424
	11th to 20th	Day	34% 7% 13% 35% 11% 1	4213
	21st to end	Day	36% 7% 16% 32% 8% 1	4495
September	1st to 10th	Day	38% 8% 14% 28% 12% 1	2383
	11th to 20th	Day	37% 7% 18% 29% 8%	2200
	21st to end	Day	44% 7% 15% 23% 10%	2200
October	1st to 10th	Day	34% 5% 14% 31% 16%	3513
	11th to 20th	Day	54% 6% 12% 24% 4	2914
	21st to end	Day	59% 6% 16% 17% 3	3081
November	1st to 10th	Day	61% 6% 12% 16% 5%	1762
	11th to 20th	Day	72% 7% 11% 8% 3	1800
	21st to end	Day	77% 7% 10% 5% 1	1560
December	1st to 10th	Day	85% 5% 5% 3 1	2280
	11th to 20th	Day	80% 8% 7% 4 1	2621
	21st to end	Day	84% 5% 5% 4 2	3706
January	1st to 10th	Night	79% 7% 6% 5% 2	6348
	11th to 20th	Night	80% 7% 7% 4 2	6360
	21st to end	Night	71% 8% 10% 9% 2	6996
February	1st to 10th	Night	64% 8% 10% 12% 5%	2722
	11th to 20th	Night	61% 8% 12% 15% 4	2358
	21st to end	Night	60% 7% 12% 15% 6%	1980
March	1st to 10th	Night	47% 5% 18% 20% 9% 1	5373
	11th to 20th	Night	49% 6% 18% 19% 7% 1	5124
	21st to end	Night	55% 7% 12% 17% 9% 1	5284
April	1st to 10th	Night	55% 5% 10% 17% 12% 1	2000
	11th to 20th	Night	50% 4 11% 21% 11% 2	1862
	21st to end	Night	49% 6% 10% 19% 15% 3	1800
May	1st to 10th	Night	40% 7% 10% 24% 16% 3	4060
	11th to 20th	Night	45% 6% 7% 24% 16% 1	3729
	21st to end	Night	42% 7% 10% 23% 12% 7%	3950
June	1st to 10th	Night	40% 6% 14% 24% 15% 1	1409
	11th to 20th	Night	42% 7% 12% 22% 13% 3	1400
	21st to end	Night	40% 6% 14% 23% 15% 2	1410
July	1st to 10th	Night	39% 6% 14% 25% 15% 2	3580
	11th to 20th	Night	28% 7% 16% 32% 16% 1	3572
	21st to end	Night	29% 7% 15% 29% 19% 1	3832
August	1st to 10th	Night	37% 8% 14% 27% 13% 1	2705
	11th to 20th	Night	33% 6% 17% 30% 13% 1	2902
	21st to end	Night	33% 6% 15% 30% 15% 1	3386
September	1st to 10th	Night	39% 7% 14% 25% 15% 1	2000
	11th to 20th	Night	40% 6% 16% 27% 10% 1	2196
	21st to end	Night	45% 7% 14% 24% 10%	2200
October	1st to 10th	Night	41% 6% 13% 30% 10% 1	3514
	11th to 20th	Night	50% 7% 13% 21% 9%	3990
	21st to end	Night	58% 7% 13% 18% 4	4467
November	1st to 10th	Night	57% 7% 12% 17% 6%	2536
	11th to 20th	Night	70% 6% 10% 7% 6%	2600
	21st to end	Night	78% 6% 9% 6% 1	2834
December	1st to 10th	Night	78% 8% 8% 5% 1	4910
	11th to 20th	Night	78% 7% 9% 4 2	5585
	21st to end	Night	84% 6% 5% 3 1	7254

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% 10% 31% 30% 10% 1	300
	11th to 20th	Day	23% 11% 25% 29% 9% 2	300
	21st to end	Day	22% 5% 28% 30% 13%	330
February	1st to 10th	Day	14% 7% 36% 32% 9% 1	300
	11th to 20th	Day	16% 10% 33% 28% 12% 1	300
	21st to end	Day	19% 10% 29% 35% 6%	249
March	1st to 10th	Day	15% 8% 27% 38% 12% 1	300
	11th to 20th	Day	14% 8% 27% 33% 15% 3	432
	21st to end	Day	23% 7% 22% 33% 13% 2	550
April	1st to 10th	Day	19% 8% 20% 39% 12% 2	500
	11th to 20th	Day	19% 8% 23% 29% 16% 5%	492
	21st to end	Day	15% 5% 23% 35% 18% 4	500
May	1st to 10th	Day	19% 4 16% 36% 21% 4	503
	11th to 20th	Day	16% 2 14% 36% 27% 5%	662
	21st to end	Day	14% 3 13% 33% 30% 7%	789
June	1st to 10th	Day	11% 2 14% 39% 29% 5%	730
	11th to 20th	Day	14% 2 13% 38% 27% 6%	730
	21st to end	Day	16% 3 12% 35% 27% 6%	730
July	1st to 10th	Day	9% 2 8% 37% 36% 9%	721
	11th to 20th	Day	9% 2 14% 32% 34% 9%	718
	21st to end	Day	9% 2 9% 34% 37% 10%	794
August	1st to 10th	Day	9% 3 9% 32% 36% 12%	654
	11th to 20th	Day	11% 4 8% 27% 38% 12%	519
	21st to end	Day	15% 4 12% 31% 29% 9%	583
September	1st to 10th	Day	19% 4 16% 28% 25% 9%	530
	11th to 20th	Day	12% 3 13% 28% 31% 12%	530
	21st to end	Day	16% 5% 19% 27% 27% 6%	530
October	1st to 10th	Day	19% 7% 26% 26% 18% 5%	502
	11th to 20th	Day	25% 11% 25% 27% 12% 1	356
	21st to end	Day	32% 9% 27% 23% 8% 2	330
November	1st to 10th	Day	21% 13% 28% 27% 12%	300
	11th to 20th	Day	23% 12% 34% 24% 6% 1	300
	21st to end	Day	25% 14% 38% 19% 4	227
December	1st to 10th	Day	30% 14% 29% 20% 7% 2	200
	11th to 20th	Day	25% 18% 32% 21% 4 1	200
	21st to end	Day	34% 16% 31% 13% 4 1	270
January	1st to 10th	Night	20% 9% 34% 28% 8% 1	1000
	11th to 20th	Night	22% 10% 32% 26% 9% 1	1000
	21st to end	Night	20% 8% 30% 32% 9% 1	1100
February	1st to 10th	Night	17% 6% 34% 33% 10% 1	922
	11th to 20th	Night	17% 7% 34% 31% 10% 1	783
	21st to end	Night	19% 7% 28% 36% 9% 1	660
March	1st to 10th	Night	17% 4 29% 36% 14% 1	800
	11th to 20th	Night	17% 5% 29% 36% 12% 1	800
	21st to end	Night	19% 5% 23% 38% 13% 2	800
April	1st to 10th	Night	21% 5% 29% 34% 9% 3	600
	11th to 20th	Night	22% 6% 20% 34% 16% 3	593
	21st to end	Night	19% 5% 21% 39% 15% 1	600
May	1st to 10th	Night	17% 4 18% 38% 22% 2	600
	11th to 20th	Night	18% 3 16% 41% 20% 3	591
	21st to end	Night	14% 3 13% 35% 31% 4	650
June	1st to 10th	Night	15% 1 13% 41% 27% 4	409
	11th to 20th	Night	14% 2 16% 39% 26% 5%	400
	21st to end	Night	16% 2 13% 32% 33% 4	410
July	1st to 10th	Night	12% 1 10% 36% 34% 6%	585
	11th to 20th	Night	10% 3 12% 34% 32% 10%	582
	21st to end	Night	9% 2 12% 40% 32% 5%	657
August	1st to 10th	Night	9% 2 11% 38% 33% 6%	597
	11th to 20th	Night	10% 3 12% 31% 35% 9%	594
	21st to end	Night	14% 3 12% 38% 29% 3	660
September	1st to 10th	Night	16% 4 18% 29% 26% 8%	600
	11th to 20th	Night	19% 4 15% 26% 27% 9%	796
	21st to end	Night	21% 6% 17% 27% 23% 7%	800
October	1st to 10th	Night	22% 6% 23% 27% 18% 3	773
	11th to 20th	Night	28% 11% 24% 27% 10% 1	760
	21st to end	Night	37% 8% 23% 24% 7% 1	836
November	1st to 10th	Night	26% 10% 29% 25% 10%	780
	11th to 20th	Night	27% 15% 32% 19% 7% 1	800
	21st to end	Night	29% 13% 34% 20% 5%	892
December	1st to 10th	Night	27% 14% 32% 20% 5% 1	1000
	11th to 20th	Night	27% 14% 36% 16% 6% 2	1000
	21st to end	Night	30% 12% 33% 20% 4 1	1100

Page generated at 2025-10-01 01:39:03. Version ac07

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