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 2024-01-13.

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% 9% 4 7% 6% 3 5% 5% 5% 7% 35%	74754
	Night	14% 11% 5% 9% 7% 4 5% 5% 5% 6% 30%	74986
Transparency	Day	48% 7% 13% 22% 9% 1	74460
	Night	55% 6% 11% 19% 8% 1	74814
Seeing	Day	16% 4 18% 33% 23% 6%	14925
	Night	19% 5% 24% 32% 18% 3	24950

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	9% 12% 7% 14% 12% 7% 8% 5% 5% 5% 16%	1517
	11th to 20th	Day	12% 15% 8% 14% 11% 5% 9% 4 4 5% 13%	1456
	21st to end	Day	9% 12% 6% 13% 10% 6% 8% 8% 6% 6% 16%	1593
February	1st to 10th	Day	8% 10% 5% 12% 8% 6% 9% 8% 5% 5% 23%	1620
	11th to 20th	Day	9% 12% 4 9% 7% 4 7% 5% 5% 7% 31%	1574
	21st to end	Day	10% 11% 6% 8% 9% 5% 6% 5% 6% 8% 27%	1468
March	1st to 10th	Day	10% 9% 3 8% 6% 3 6% 6% 6% 8% 34%	1798
	11th to 20th	Day	13% 9% 4 8% 6% 4 4 4 5% 6% 38%	1958
	21st to end	Day	16% 9% 5% 7% 6% 3 4 5% 5% 7% 32%	2306
April	1st to 10th	Day	15% 8% 4 6% 7% 4 6% 5% 5% 6% 34%	2160
	11th to 20th	Day	19% 11% 4 5% 5% 3 5% 5% 4 6% 33%	2134
	21st to end	Day	20% 9% 3 5% 5% 3 4 4 4 6% 37%	2346
May	1st to 10th	Day	17% 6% 3 5% 5% 3 5% 4 5% 7% 39%	2520
	11th to 20th	Day	15% 6% 3 6% 4 3 5% 5% 7% 8% 38%	2479
	21st to end	Day	14% 7% 3 5% 5% 3 6% 5% 5% 9% 39%	2725
June	1st to 10th	Day	11% 6% 2 5% 5% 3 5% 5% 6% 9% 43%	2520
	11th to 20th	Day	12% 7% 4 5% 5% 3 4 5% 6% 8% 40%	2520
	21st to end	Day	13% 4 2 5% 5% 4 5% 4 6% 9% 42%	2520
July	1st to 10th	Day	7% 4 2 3 4 2 4 4 7% 11% 53%	2520
	11th to 20th	Day	8% 4 2 4 4 3 4 5% 6% 10% 50%	2520
	21st to end	Day	7% 4 1 3 4 2 4 5% 5% 9% 55%	2743
August	1st to 10th	Day	8% 4 2 4 5% 3 5% 5% 7% 9% 49%	2507
	11th to 20th	Day	10% 6% 2 5% 5% 3 4 4 5% 7% 50%	2327
	21st to end	Day	10% 5% 2 5% 4 2 4 4 5% 7% 52%	2390
September	1st to 10th	Day	12% 5% 2 5% 4 3 4 5% 6% 8% 46%	2160
	11th to 20th	Day	13% 6% 2 5% 4 3 4 5% 6% 8% 43%	2156
	21st to end	Day	19% 8% 3 5% 6% 3 3 4 5% 7% 37%	1926
October	1st to 10th	Day	18% 8% 3 5% 6% 3 4 5% 6% 7% 35%	1800
	11th to 20th	Day	19% 14% 4 7% 5% 3 5% 4 5% 7% 27%	1800
	21st to end	Day	20% 15% 5% 8% 5% 4 5% 5% 3 5% 26%	1800
November	1st to 10th	Day	15% 14% 5% 9% 7% 3 4 5% 5% 6% 27%	1634
	11th to 20th	Day	16% 16% 8% 15% 8% 3 4 3 5% 5% 16%	1520
	21st to end	Day	16% 13% 6% 14% 12% 3 4 6% 4 5% 17%	1520
December	1st to 10th	Day	11% 17% 9% 18% 12% 5% 5% 3 4 5% 11%	1520
	11th to 20th	Day	13% 15% 7% 17% 12% 7% 6% 5% 4 4 10%	1914
	21st to end	Day	25% 17% 8% 13% 8% 4 4 3 3 3 13%	2783
January	1st to 10th	Night	10% 12% 5% 15% 11% 8% 8% 5% 4 5% 17%	2648
	11th to 20th	Night	13% 14% 7% 13% 11% 6% 8% 5% 5% 5% 12%	2549
	21st to end	Night	13% 13% 8% 12% 9% 6% 7% 5% 6% 6% 14%	2758
February	1st to 10th	Night	8% 14% 6% 10% 9% 6% 8% 7% 5% 5% 22%	2340
	11th to 20th	Night	10% 9% 4 9% 8% 6% 7% 6% 7% 6% 28%	2273
	21st to end	Night	12% 13% 6% 9% 6% 3 5% 5% 5% 7% 30%	1787
March	1st to 10th	Night	11% 10% 4 7% 7% 4 4 5% 5% 7% 36%	2149
	11th to 20th	Night	12% 11% 3 6% 6% 3 5% 5% 5% 6% 38%	2015
	21st to end	Night	17% 8% 4 8% 6% 4 5% 4 5% 6% 34%	2049
April	1st to 10th	Night	17% 12% 4 8% 6% 4 4 4 5% 6% 30%	1800
	11th to 20th	Night	20% 10% 3 6% 5% 3 4 4 5% 6% 34%	1775
	21st to end	Night	19% 10% 3 7% 5% 3 4 4 5% 6% 34%	1611
May	1st to 10th	Night	16% 8% 4 8% 8% 4 5% 5% 4 5% 33%	1440
	11th to 20th	Night	17% 6% 3 5% 6% 4 4 4 5% 6% 39%	1416
	21st to end	Night	16% 6% 2 6% 6% 3 5% 5% 6% 8% 38%	1551
June	1st to 10th	Night	14% 6% 2 5% 5% 3 5% 5% 6% 8% 40%	1440
	11th to 20th	Night	13% 6% 3 6% 6% 4 6% 5% 6% 10% 36%	1440
	21st to end	Night	13% 6% 3 5% 5% 3 5% 5% 5% 8% 41%	1440
July	1st to 10th	Night	6% 4 2 5% 5% 3 4 5% 6% 10% 50%	1440
	11th to 20th	Night	7% 4 3 5% 6% 2 5% 6% 7% 9% 46%	1440
	21st to end	Night	7% 4 2 4 4 2 5% 5% 6% 8% 53%	1575
August	1st to 10th	Night	9% 3 2 3 4 2 4 5% 7% 9% 51%	1432
	11th to 20th	Night	12% 5% 2 5% 4 2 4 4 5% 7% 50%	1571
	21st to end	Night	11% 6% 2 4 4 2 4 4 5% 8% 49%	1966
September	1st to 10th	Night	11% 5% 2 5% 4 3 4 5% 5% 8% 48%	1800
	11th to 20th	Night	12% 5% 2 5% 5% 3 4 4 5% 8% 46%	1800
	21st to end	Night	19% 7% 3 6% 5% 3 4 5% 5% 7% 37%	2019
October	1st to 10th	Night	20% 7% 3 6% 5% 2 3 5% 4 6% 40%	2160
	11th to 20th	Night	18% 12% 4 8% 5% 3 5% 4 5% 6% 30%	2160
	21st to end	Night	21% 13% 5% 8% 6% 3 4 4 4 6% 24%	2556
November	1st to 10th	Night	16% 15% 5% 9% 6% 3 5% 4 6% 6% 26%	2439
	11th to 20th	Night	15% 18% 8% 13% 7% 3 4 4 4 4 20%	2660
	21st to end	Night	16% 13% 7% 14% 9% 3 5% 4 4 6% 19%	2660
December	1st to 10th	Night	13% 19% 7% 16% 11% 4 5% 4 4 3 13%	2660
	11th to 20th	Night	11% 16% 8% 13% 12% 5% 6% 4 4 5% 16%	3283
	21st to end	Night	25% 21% 6% 10% 7% 4 4 3 2 4 14%	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	70% 6% 11% 11% 3	1518
	11th to 20th	Day	75% 6% 9% 9% 1	1456
	21st to end	Day	66% 6% 14% 10% 4	1593
February	1st to 10th	Day	60% 6% 15% 16% 3	1620
	11th to 20th	Day	51% 7% 14% 21% 7%	1583
	21st to end	Day	55% 7% 11% 15% 11% 1	1468
March	1st to 10th	Day	47% 8% 17% 19% 9%	1800
	11th to 20th	Day	48% 5% 14% 20% 12% 1	1958
	21st to end	Day	51% 7% 12% 19% 10% 1	2306
April	1st to 10th	Day	50% 7% 11% 19% 12% 1	2160
	11th to 20th	Day	52% 6% 11% 18% 12% 2	2134
	21st to end	Day	50% 4 10% 24% 11% 1	2346
May	1st to 10th	Day	45% 8% 10% 25% 11% 1	2520
	11th to 20th	Day	42% 8% 14% 23% 11% 2	2483
	21st to end	Day	42% 8% 11% 25% 13% 1	2725
June	1st to 10th	Day	36% 8% 15% 26% 13% 1	2520
	11th to 20th	Day	41% 7% 12% 24% 15% 1	2520
	21st to end	Day	38% 9% 16% 27% 10% 1	2520
July	1st to 10th	Day	26% 8% 16% 32% 17% 1	2451
	11th to 20th	Day	29% 9% 16% 29% 16% 2	2445
	21st to end	Day	25% 9% 16% 31% 17% 1	2591
August	1st to 10th	Day	31% 8% 15% 33% 11% 2	2492
	11th to 20th	Day	33% 7% 16% 31% 12%	2327
	21st to end	Day	32% 7% 14% 33% 14% 1	2390
September	1st to 10th	Day	36% 7% 14% 33% 9%	2160
	11th to 20th	Day	38% 8% 19% 28% 7%	2156
	21st to end	Day	47% 7% 14% 25% 8%	1926
October	1st to 10th	Day	47% 8% 14% 25% 6%	1800
	11th to 20th	Day	56% 7% 13% 18% 7%	1800
	21st to end	Day	61% 7% 11% 16% 5%	1800
November	1st to 10th	Day	57% 5% 12% 18% 7% 1	1634
	11th to 20th	Day	71% 6% 10% 10% 4	1520
	21st to end	Day	69% 8% 10% 10% 3 1	1520
December	1st to 10th	Day	76% 6% 9% 8% 1	1520
	11th to 20th	Day	79% 6% 6% 7% 1	1915
	21st to end	Day	78% 4 7% 10%	2783
January	1st to 10th	Night	69% 5% 11% 11% 3	2648
	11th to 20th	Night	74% 8% 11% 6% 1	2549
	21st to end	Night	71% 4 11% 10% 3	2758
February	1st to 10th	Night	62% 6% 13% 14% 4 1	2340
	11th to 20th	Night	55% 7% 14% 17% 7%	2274
	21st to end	Night	56% 6% 10% 19% 8% 1	1787
March	1st to 10th	Night	48% 6% 13% 21% 11% 1	2160
	11th to 20th	Night	46% 8% 11% 23% 11% 1	2016
	21st to end	Night	52% 6% 10% 19% 11% 2	2049
April	1st to 10th	Night	55% 6% 9% 17% 13% 1	1800
	11th to 20th	Night	52% 4 9% 21% 12% 2	1775
	21st to end	Night	51% 6% 7% 22% 15%	1611
May	1st to 10th	Night	53% 8% 10% 18% 10% 2	1440
	11th to 20th	Night	45% 6% 9% 24% 14% 2	1417
	21st to end	Night	44% 8% 11% 23% 12% 2	1552
June	1st to 10th	Night	40% 8% 13% 24% 13% 2	1440
	11th to 20th	Night	43% 8% 11% 20% 17% 1	1440
	21st to end	Night	40% 8% 12% 26% 12% 1	1440
July	1st to 10th	Night	30% 8% 12% 32% 17% 2	1400
	11th to 20th	Night	32% 8% 15% 27% 15% 3	1392
	21st to end	Night	28% 7% 15% 30% 17% 3	1487
August	1st to 10th	Night	28% 8% 15% 33% 12% 4	1423
	11th to 20th	Night	34% 6% 15% 30% 14% 1	1571
	21st to end	Night	34% 7% 13% 28% 16% 1	1966
September	1st to 10th	Night	35% 7% 13% 31% 13% 1	1800
	11th to 20th	Night	37% 6% 15% 35% 7%	1800
	21st to end	Night	47% 6% 16% 24% 8%	2019
October	1st to 10th	Night	45% 6% 14% 25% 9% 1	2160
	11th to 20th	Night	55% 6% 13% 19% 7% 1	2160
	21st to end	Night	61% 6% 10% 17% 6%	2556
November	1st to 10th	Night	60% 5% 10% 19% 6% 1	2439
	11th to 20th	Night	70% 5% 9% 10% 6%	2660
	21st to end	Night	68% 6% 13% 9% 4	2660
December	1st to 10th	Night	76% 5% 9% 8% 1	2660
	11th to 20th	Night	71% 6% 10% 12% 2	3281
	21st to end	Night	76% 5% 7% 10% 1	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	14% 7% 34% 26% 16% 3	270
	11th to 20th	Day	18% 4 28% 31% 17% 2	246
	21st to end	Day	16% 3 28% 38% 13% 2	264
February	1st to 10th	Day	13% 5% 29% 38% 13% 1	240
	11th to 20th	Day	13% 5% 38% 28% 14% 2	240
	21st to end	Day	18% 3 29% 44% 6%	198
March	1st to 10th	Day	13% 6% 19% 42% 19% 1	240
	11th to 20th	Day	15% 4 22% 40% 14% 6%	240
	21st to end	Day	20% 5% 22% 30% 19% 4	392
April	1st to 10th	Day	20% 6% 20% 37% 15% 2	420
	11th to 20th	Day	24% 5% 15% 33% 20% 3	412
	21st to end	Day	26% 4 18% 29% 19% 5%	513
May	1st to 10th	Day	20% 4 14% 40% 19% 4	603
	11th to 20th	Day	19% 4 13% 36% 22% 7%	625
	21st to end	Day	19% 3 13% 32% 28% 5%	679
June	1st to 10th	Day	11% 2 14% 37% 30% 6%	630
	11th to 20th	Day	14% 2 14% 38% 28% 4	630
	21st to end	Day	15% 2 12% 36% 28% 7%	630
July	1st to 10th	Day	8% 2 8% 33% 38% 11%	621
	11th to 20th	Day	9% 1 11% 37% 32% 9%	618
	21st to end	Day	7% 2 9% 35% 34% 12%	684
August	1st to 10th	Day	12% 3 10% 33% 35% 8%	626
	11th to 20th	Day	13% 1 12% 27% 35% 12%	615
	21st to end	Day	15% 3 16% 29% 30% 8%	509
September	1st to 10th	Day	15% 2 14% 33% 29% 7%	450
	11th to 20th	Day	14% 2 17% 34% 26% 8%	450
	21st to end	Day	26% 4 18% 25% 21% 6%	396
October	1st to 10th	Day	19% 7% 19% 25% 25% 6%	270
	11th to 20th	Day	21% 7% 29% 23% 17% 2	270
	21st to end	Day	28% 8% 25% 29% 9% 1	297
November	1st to 10th	Day	17% 9% 27% 33% 13% 1	270
	11th to 20th	Day	21% 9% 36% 24% 7% 1	270
	21st to end	Day	23% 7% 33% 30% 7% 1	270
December	1st to 10th	Day	20% 8% 31% 29% 11% 2	270
	11th to 20th	Day	19% 12% 32% 28% 8% 1	270
	21st to end	Day	24% 7% 37% 24% 6% 2	297
January	1st to 10th	Night	15% 6% 33% 34% 11% 1	950
	11th to 20th	Night	20% 5% 33% 29% 11% 1	911
	21st to end	Night	18% 4 30% 37% 9% 1	990
February	1st to 10th	Night	16% 4 34% 33% 12% 1	900
	11th to 20th	Night	15% 3 33% 33% 15% 2	879
	21st to end	Night	19% 4 26% 38% 12% 1	603
March	1st to 10th	Night	14% 5% 25% 40% 14% 2	720
	11th to 20th	Night	19% 4 28% 35% 13% 2	576
	21st to end	Night	19% 4 21% 35% 16% 5%	594
April	1st to 10th	Night	22% 6% 22% 35% 13% 2	540
	11th to 20th	Night	25% 6% 16% 33% 17% 3	533
	21st to end	Night	25% 4 15% 32% 20% 4	540
May	1st to 10th	Night	19% 4 22% 35% 15% 4	540
	11th to 20th	Night	18% 3 15% 37% 23% 4	531
	21st to end	Night	18% 2 14% 27% 34% 5%	584
June	1st to 10th	Night	15% 3 14% 36% 27% 6%	540
	11th to 20th	Night	17% 2 13% 39% 25% 4	540
	21st to end	Night	14% 3 13% 32% 31% 7%	540
July	1st to 10th	Night	9% 1 10% 37% 37% 8%	525
	11th to 20th	Night	8% 3 15% 34% 34% 7%	522
	21st to end	Night	9% 1 12% 35% 35% 8%	591
August	1st to 10th	Night	11% 1 11% 35% 37% 5%	537
	11th to 20th	Night	13% 3 12% 29% 35% 9%	534
	21st to end	Night	15% 2 14% 34% 30% 5%	594
September	1st to 10th	Night	11% 3 17% 33% 29% 7%	540
	11th to 20th	Night	14% 2 17% 38% 26% 3	540
	21st to end	Night	22% 4 22% 27% 22% 4	706
October	1st to 10th	Night	23% 4 22% 28% 19% 4	720
	11th to 20th	Night	26% 8% 30% 23% 13% 1	720
	21st to end	Night	28% 8% 24% 27% 12%	792
November	1st to 10th	Night	23% 8% 25% 31% 12% 1	773
	11th to 20th	Night	23% 10% 32% 23% 10% 1	950
	21st to end	Night	21% 9% 34% 29% 7%	950
December	1st to 10th	Night	21% 10% 36% 24% 8% 1	950
	11th to 20th	Night	22% 8% 34% 26% 8% 2	950
	21st to end	Night	29% 8% 31% 25% 6%	1045

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