Madeline Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Madeline Island clear sky chart from 2005-11-06 to 2025-10-19.

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	12% 9% 4 9% 5% 5% 5% 4 5% 7% 36%	127086
	Night	13% 11% 4 11% 6% 5% 5% 4 5% 6% 30%	122910
Transparency	Day	47% 6% 13% 23% 10% 1	130526
	Night	54% 6% 11% 19% 9% 1	127544
Seeing	Day	16% 4 19% 33% 23% 5%	17470
	Night	19% 5% 24% 32% 18% 3	27289

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	6% 13% 6% 24% 15% 7% 5% 2 4 4 13%	3617
	11th to 20th	Day	6% 15% 5% 15% 15% 17% 9% 6% 2 3 7%	3589
	21st to end	Day	7% 14% 6% 15% 7% 8% 7% 5% 7% 6% 19%	4005
February	1st to 10th	Day	7% 11% 5% 13% 6% 8% 9% 5% 5% 5% 23%	1800
	11th to 20th	Day	8% 12% 4 10% 7% 6% 7% 4 6% 7% 30%	1754
	21st to end	Day	8% 12% 5% 9% 9% 6% 6% 4 6% 8% 27%	1637
March	1st to 10th	Day	11% 8% 2 7% 5% 4 5% 4 6% 8% 39%	4478
	11th to 20th	Day	8% 10% 4 11% 7% 5% 6% 5% 6% 7% 31%	4930
	21st to end	Day	21% 11% 4 9% 4 3 3 3 4 5% 33%	5801
April	1st to 10th	Day	15% 10% 3 7% 6% 5% 5% 4 6% 6% 33%	2400
	11th to 20th	Day	17% 11% 4 6% 5% 5% 5% 4 5% 6% 33%	2374
	21st to end	Day	20% 10% 3 6% 4 4 4 3 4 6% 36%	2608
May	1st to 10th	Day	16% 6% 2 5% 3 3 3 2 5% 5% 50%	6348
	11th to 20th	Day	14% 7% 3 7% 4 4 5% 4 6% 6% 41%	6319
	21st to end	Day	12% 8% 3 7% 5% 4 5% 4 5% 7% 41%	6949
June	1st to 10th	Day	11% 7% 2 6% 4 4 5% 4 6% 9% 42%	2800
	11th to 20th	Day	12% 7% 3 7% 5% 5% 4 4 7% 8% 38%	2800
	21st to end	Day	14% 5% 2 6% 4 5% 5% 4 6% 9% 41%	2800
July	1st to 10th	Day	9% 6% 2 5% 3 3 4 4 6% 9% 49%	6359
	11th to 20th	Day	10% 5% 2 5% 3 4 4 3 6% 10% 50%	6360
	21st to end	Day	7% 4 2 4 3 3 4 4 6% 8% 54%	6926
August	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 4 6% 8% 44%	4563
	11th to 20th	Day	12% 5% 1 4 3 3 3 2 5% 7% 54%	4211
	21st to end	Day	10% 6% 2 6% 4 4 4 4 6% 9% 46%	4327
September	1st to 10th	Day	12% 5% 3 6% 3 4 4 4 6% 8% 46%	2400
	11th to 20th	Day	12% 7% 2 6% 4 4 4 4 6% 9% 43%	2395
	21st to end	Day	17% 8% 3 6% 5% 3 3 3 5% 6% 40%	2139
October	1st to 10th	Day	17% 7% 3 6% 5% 4 5% 3 6% 7% 38%	2000
	11th to 20th	Day	18% 14% 4 8% 4 4 4 3 5% 7% 28%	1980
	21st to end	Day	20% 15% 5% 8% 4 5% 4 4 4 5% 27%	1899
November	1st to 10th	Day	15% 15% 4 11% 5% 4 4 3 5% 6% 27%	1722
	11th to 20th	Day	15% 17% 7% 17% 7% 4 4 3 5% 5% 17%	1600
	21st to end	Day	16% 14% 7% 17% 8% 4 5% 4 4 5% 16%	1600
December	1st to 10th	Day	9% 21% 11% 26% 8% 5% 3 2 3 3 9%	2610
	11th to 20th	Day	10% 16% 8% 19% 9% 12% 6% 3 3 3 10%	3004
	21st to end	Day	20% 17% 8% 16% 7% 5% 4 3 3 3 14%	3982
January	1st to 10th	Night	7% 16% 7% 22% 8% 7% 5% 3 3 4 18%	6348
	11th to 20th	Night	8% 14% 7% 16% 13% 13% 11% 4 3 3 7%	6316
	21st to end	Night	7% 14% 6% 15% 8% 8% 6% 5% 6% 5% 19%	6968
February	1st to 10th	Night	8% 15% 4 11% 9% 8% 8% 5% 5% 5% 22%	2600
	11th to 20th	Night	9% 9% 4 10% 8% 8% 6% 5% 7% 6% 27%	2533
	21st to end	Night	11% 14% 5% 9% 6% 4 5% 4 5% 7% 30%	1992
March	1st to 10th	Night	9% 7% 3 7% 4 5% 5% 4 6% 8% 43%	5362
	11th to 20th	Night	10% 11% 5% 11% 7% 5% 5% 4 6% 7% 28%	5071
	21st to end	Night	22% 12% 5% 10% 5% 4 4 3 4 4 26%	5129
April	1st to 10th	Night	17% 14% 3 9% 5% 5% 4 3 5% 6% 30%	2000
	11th to 20th	Night	19% 11% 3 7% 4 4 4 3 5% 5% 34%	1975
	21st to end	Night	19% 10% 3 7% 4 4 3 3 5% 6% 35%	1788
May	1st to 10th	Night	14% 6% 2 7% 5% 4 4 3 5% 6% 45%	3613
	11th to 20th	Night	14% 7% 2 7% 5% 5% 4 4 5% 6% 42%	3596
	21st to end	Night	12% 8% 2 8% 5% 4 5% 4 6% 7% 38%	3949
June	1st to 10th	Night	14% 6% 2 6% 5% 4 5% 4 6% 7% 40%	1600
	11th to 20th	Night	13% 7% 3 7% 5% 6% 6% 4 6% 9% 35%	1600
	21st to end	Night	13% 7% 3 6% 4 5% 4 5% 6% 8% 40%	1600
July	1st to 10th	Night	8% 6% 2 7% 4 5% 5% 4 6% 10% 42%	3620
	11th to 20th	Night	10% 4 2 5% 3 3 4 4 6% 8% 51%	3620
	21st to end	Night	9% 6% 3 6% 4 4 4 4 6% 8% 47%	3948
August	1st to 10th	Night	12% 5% 2 6% 4 4 4 4 6% 8% 45%	2597
	11th to 20th	Night	13% 5% 2 5% 3 3 4 3 6% 7% 48%	2845
	21st to end	Night	15% 7% 2 6% 3 3 4 3 5% 7% 44%	3571
September	1st to 10th	Night	11% 6% 2 5% 4 4 4 3 5% 8% 47%	2000
	11th to 20th	Night	12% 6% 2 5% 4 4 5% 3 5% 8% 45%	2000
	21st to end	Night	17% 8% 2 6% 4 4 5% 4 5% 7% 39%	2244
October	1st to 10th	Night	18% 7% 2 7% 4 3 4 4 5% 6% 42%	2400
	11th to 20th	Night	17% 13% 4 8% 5% 4 4 3 5% 6% 31%	2377
	21st to end	Night	21% 14% 5% 9% 5% 4 4 4 5% 6% 24%	2698
November	1st to 10th	Night	16% 15% 5% 10% 5% 4 5% 4 5% 6% 26%	2571
	11th to 20th	Night	15% 19% 8% 14% 6% 4 3 3 4 4 20%	2800
	21st to end	Night	15% 15% 6% 16% 8% 4 4 3 4 6% 18%	2800
December	1st to 10th	Night	12% 20% 10% 23% 8% 4 4 2 3 3 10%	4580
	11th to 20th	Night	11% 18% 8% 18% 8% 11% 4 3 3 3 12%	5203
	21st to end	Night	21% 19% 6% 12% 7% 5% 4 3 3 4 15%	6996

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	75% 5% 7% 9% 3	3618
	11th to 20th	Day	84% 5% 6% 5% 1	3620
	21st to end	Day	62% 8% 13% 14% 3	4005
February	1st to 10th	Day	60% 6% 15% 16% 4	1800
	11th to 20th	Day	53% 7% 13% 21% 7%	1763
	21st to end	Day	53% 7% 13% 16% 10% 1	1637
March	1st to 10th	Day	42% 6% 16% 22% 12% 2	4480
	11th to 20th	Day	50% 7% 14% 17% 11%	4930
	21st to end	Day	54% 4 11% 20% 11%	5801
April	1st to 10th	Day	50% 7% 10% 19% 13% 1	2400
	11th to 20th	Day	51% 6% 11% 19% 12% 2	2374
	21st to end	Day	50% 4 10% 23% 12% 1	2608
May	1st to 10th	Day	37% 5% 12% 27% 19% 1	6357
	11th to 20th	Day	42% 7% 13% 23% 9% 6%	6323
	21st to end	Day	42% 7% 9% 25% 16% 1	6949
June	1st to 10th	Day	37% 7% 15% 26% 14% 1	2800
	11th to 20th	Day	42% 7% 13% 23% 14% 1	2800
	21st to end	Day	39% 8% 15% 26% 10% 1	2800
July	1st to 10th	Day	32% 7% 20% 30% 11% 1	6291
	11th to 20th	Day	30% 6% 18% 35% 11% 1	6285
	21st to end	Day	27% 7% 16% 35% 16% 1	6728
August	1st to 10th	Day	37% 6% 17% 27% 12% 1	4548
	11th to 20th	Day	30% 5% 20% 33% 11%	4251
	21st to end	Day	34% 7% 18% 30% 10% 1	4326
September	1st to 10th	Day	36% 7% 15% 33% 9%	2400
	11th to 20th	Day	37% 8% 19% 29% 6%	2395
	21st to end	Day	45% 6% 13% 26% 10%	2139
October	1st to 10th	Day	35% 5% 17% 31% 11% 1	3260
	11th to 20th	Day	50% 5% 11% 24% 10%	3220
	21st to end	Day	55% 6% 15% 19% 5%	3099
November	1st to 10th	Day	58% 5% 12% 17% 7% 1	1722
	11th to 20th	Day	70% 6% 10% 10% 4	1600
	21st to end	Day	70% 7% 10% 9% 3 1	1600
December	1st to 10th	Day	82% 5% 6% 6%	2610
	11th to 20th	Day	81% 5% 5% 5% 4	3005
	21st to end	Day	77% 4 7% 12% 1	3982
January	1st to 10th	Night	72% 5% 9% 10% 4	6348
	11th to 20th	Night	83% 5% 8% 4 1	6360
	21st to end	Night	64% 6% 14% 13% 3	6968
February	1st to 10th	Night	62% 6% 13% 14% 5% 1	2600
	11th to 20th	Night	55% 7% 13% 18% 7%	2534
	21st to end	Night	55% 6% 11% 20% 8% 1	1992
March	1st to 10th	Night	40% 4 16% 19% 18% 3	5373
	11th to 20th	Night	55% 7% 11% 21% 7%	5072
	21st to end	Night	61% 5% 7% 15% 12% 1	5129
April	1st to 10th	Night	56% 5% 8% 17% 13% 1	2000
	11th to 20th	Night	50% 5% 9% 22% 12% 2	1975
	21st to end	Night	50% 5% 7% 23% 15%	1788
May	1st to 10th	Night	40% 6% 12% 27% 14% 1	3620
	11th to 20th	Night	41% 6% 9% 23% 14% 6%	3597
	21st to end	Night	42% 7% 10% 25% 14% 1	3950
June	1st to 10th	Night	40% 7% 13% 24% 14% 2	1600
	11th to 20th	Night	44% 8% 11% 20% 17% 1	1600
	21st to end	Night	42% 8% 12% 26% 12% 1	1600
July	1st to 10th	Night	37% 7% 17% 27% 10% 2	3580
	11th to 20th	Night	31% 6% 19% 34% 10% 1	3572
	21st to end	Night	35% 6% 13% 28% 17% 1	3832
August	1st to 10th	Night	36% 6% 13% 27% 15% 2	2588
	11th to 20th	Night	36% 5% 18% 30% 11% 1	2871
	21st to end	Night	39% 7% 14% 28% 11% 1	3571
September	1st to 10th	Night	35% 7% 13% 32% 12% 1	2000
	11th to 20th	Night	38% 6% 16% 34% 6%	2000
	21st to end	Night	44% 6% 15% 25% 10%	2244
October	1st to 10th	Night	33% 4 11% 33% 19% 1	3920
	11th to 20th	Night	50% 4 11% 21% 13%	3876
	21st to end	Night	57% 5% 11% 20% 7%	4436
November	1st to 10th	Night	59% 5% 10% 18% 6% 1	2571
	11th to 20th	Night	69% 5% 10% 11% 6%	2800
	21st to end	Night	69% 6% 13% 9% 4	2800
December	1st to 10th	Night	81% 5% 8% 6% 1	4580
	11th to 20th	Night	78% 5% 7% 10% 1	5201
	21st to end	Night	73% 5% 8% 12% 2	6996

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	13% 7% 35% 27% 15% 3	300
	11th to 20th	Day	15% 5% 31% 32% 16% 2	300
	21st to end	Day	13% 6% 30% 36% 13% 2	330
February	1st to 10th	Day	12% 6% 31% 36% 12% 2	300
	11th to 20th	Day	11% 8% 34% 31% 15% 2	300
	21st to end	Day	14% 5% 29% 46% 6%	249
March	1st to 10th	Day	14% 6% 22% 40% 17% 1	300
	11th to 20th	Day	14% 4 24% 41% 13% 5%	300
	21st to end	Day	22% 5% 21% 33% 16% 3	473
April	1st to 10th	Day	21% 6% 20% 37% 13% 2	500
	11th to 20th	Day	22% 6% 17% 35% 17% 2	492
	21st to end	Day	25% 5% 17% 30% 19% 4	604
May	1st to 10th	Day	19% 4 15% 39% 19% 4	703
	11th to 20th	Day	18% 4 13% 37% 22% 6%	725
	21st to end	Day	18% 4 13% 32% 28% 5%	789
June	1st to 10th	Day	11% 2 15% 38% 29% 6%	730
	11th to 20th	Day	14% 2 17% 38% 25% 4	730
	21st to end	Day	15% 3 13% 36% 26% 6%	730
July	1st to 10th	Day	8% 2 8% 35% 37% 10%	721
	11th to 20th	Day	9% 1 11% 37% 31% 10%	718
	21st to end	Day	8% 2 9% 36% 34% 11%	794
August	1st to 10th	Day	11% 3 11% 32% 35% 8%	726
	11th to 20th	Day	13% 2 12% 28% 34% 11%	715
	21st to end	Day	14% 4 16% 28% 31% 8%	598
September	1st to 10th	Day	15% 2 15% 31% 29% 8%	530
	11th to 20th	Day	13% 2 15% 33% 28% 7%	530
	21st to end	Day	23% 4 17% 26% 23% 6%	469
October	1st to 10th	Day	17% 7% 22% 26% 22% 6%	330
	11th to 20th	Day	20% 7% 30% 25% 15% 2	324
	21st to end	Day	28% 8% 25% 29% 9% 1	330
November	1st to 10th	Day	19% 9% 26% 32% 13% 1	300
	11th to 20th	Day	20% 11% 36% 25% 7% 1	300
	21st to end	Day	23% 8% 33% 30% 6% 1	300
December	1st to 10th	Day	19% 9% 32% 28% 11% 2	300
	11th to 20th	Day	19% 11% 34% 28% 8% 1	300
	21st to end	Day	23% 7% 34% 27% 8% 2	330
January	1st to 10th	Night	14% 7% 32% 35% 11% 1	1000
	11th to 20th	Night	19% 5% 34% 30% 11% 1	1000
	21st to end	Night	17% 4 30% 37% 10% 1	1100
February	1st to 10th	Night	16% 5% 32% 33% 13% 1	1000
	11th to 20th	Night	14% 3 34% 33% 15% 2	979
	21st to end	Night	18% 4 26% 39% 12% 1	672
March	1st to 10th	Night	14% 5% 25% 41% 13% 2	800
	11th to 20th	Night	18% 5% 28% 35% 12% 2	640
	21st to end	Night	20% 5% 22% 33% 15% 5%	660
April	1st to 10th	Night	23% 6% 21% 34% 13% 2	600
	11th to 20th	Night	24% 6% 17% 34% 17% 3	593
	21st to end	Night	25% 4 14% 33% 20% 4	600
May	1st to 10th	Night	18% 4 21% 36% 17% 4	600
	11th to 20th	Night	17% 3 15% 38% 23% 4	591
	21st to end	Night	17% 2 15% 29% 32% 4	650
June	1st to 10th	Night	15% 3 14% 37% 26% 5%	600
	11th to 20th	Night	17% 2 12% 41% 24% 4	600
	21st to end	Night	15% 3 14% 34% 28% 7%	600
July	1st to 10th	Night	8% 1 9% 38% 36% 8%	585
	11th to 20th	Night	9% 3 14% 34% 34% 7%	582
	21st to end	Night	9% 1 11% 36% 36% 8%	657
August	1st to 10th	Night	12% 1 11% 34% 36% 6%	597
	11th to 20th	Night	14% 3 12% 29% 34% 8%	594
	21st to end	Night	14% 2 15% 33% 31% 5%	660
September	1st to 10th	Night	12% 4 17% 32% 29% 7%	600
	11th to 20th	Night	13% 3 16% 37% 28% 4	600
	21st to end	Night	20% 4 20% 28% 24% 5%	785
October	1st to 10th	Night	21% 5% 23% 28% 19% 4	800
	11th to 20th	Night	25% 7% 30% 25% 12% 1	793
	21st to end	Night	28% 8% 25% 27% 12%	836
November	1st to 10th	Night	23% 8% 26% 31% 12% 1	815
	11th to 20th	Night	23% 10% 32% 24% 10% 1	1000
	21st to end	Night	22% 9% 33% 29% 7%	1000
December	1st to 10th	Night	22% 10% 36% 24% 8% 1	1000
	11th to 20th	Night	22% 8% 34% 26% 8% 2	1000
	21st to end	Night	28% 8% 31% 26% 6% 1	1100

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