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 2024-11-06.

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% 3 9% 5% 5% 5% 4 5% 7% 36%	101664
	Night	13% 12% 4 10% 6% 5% 5% 3 5% 6% 31%	97560
Transparency	Day	47% 7% 14% 23% 10% 1	105121
	Night	53% 6% 12% 20% 9% 1	102178
Seeing	Day	16% 4 18% 33% 23% 5%	16124
	Night	19% 5% 24% 32% 18% 3	25993

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% 17% 7% 21% 9% 7% 5% 3 4 4 14%	2527
	11th to 20th	Day	7% 16% 6% 17% 14% 16% 8% 2 2 3 8%	2530
	21st to end	Day	8% 16% 6% 16% 7% 8% 6% 5% 6% 6% 16%	2792
February	1st to 10th	Day	8% 11% 5% 13% 6% 7% 8% 6% 5% 5% 24%	1710
	11th to 20th	Day	9% 12% 4 10% 7% 6% 6% 4 6% 7% 30%	1664
	21st to end	Day	9% 12% 5% 9% 9% 6% 6% 4 6% 8% 27%	1557
March	1st to 10th	Day	9% 9% 3 9% 5% 5% 5% 4 6% 7% 38%	3118
	11th to 20th	Day	8% 9% 4 11% 7% 5% 6% 5% 7% 8% 32%	3444
	21st to end	Day	18% 11% 4 11% 5% 4 4 3 5% 6% 30%	4053
April	1st to 10th	Day	15% 10% 3 7% 6% 5% 5% 4 6% 6% 33%	2280
	11th to 20th	Day	18% 11% 4 6% 4 5% 5% 4 4 6% 33%	2254
	21st to end	Day	20% 10% 3 6% 4 5% 4 3 4 6% 36%	2478
May	1st to 10th	Day	19% 7% 2 5% 3 3 4 3 5% 6% 42%	4428
	11th to 20th	Day	14% 6% 2 6% 4 4 5% 4 6% 7% 41%	4399
	21st to end	Day	16% 9% 3 7% 5% 4 5% 4 5% 8% 35%	4837
June	1st to 10th	Day	11% 7% 2 6% 4 4 5% 4 6% 9% 43%	2660
	11th to 20th	Day	12% 7% 3 7% 4 5% 4 4 7% 8% 39%	2660
	21st to end	Day	14% 5% 2 6% 4 5% 5% 4 6% 9% 42%	2660
July	1st to 10th	Day	9% 6% 2 5% 3 3 3 4 7% 10% 48%	4440
	11th to 20th	Day	6% 4 2 5% 3 4 4 4 6% 11% 52%	4440
	21st to end	Day	7% 4 2 4 3 3 4 4 6% 8% 56%	4814
August	1st to 10th	Day	9% 6% 2 7% 5% 5% 6% 4 6% 8% 44%	4423
	11th to 20th	Day	13% 5% 1 4 3 3 3 2 5% 7% 54%	4080
	21st to end	Day	10% 6% 2 6% 4 4 4 4 6% 9% 45%	4194
September	1st to 10th	Day	11% 5% 2 6% 3 4 4 4 6% 8% 47%	2280
	11th to 20th	Day	12% 6% 2 6% 3 4 5% 4 6% 8% 44%	2275
	21st to end	Day	18% 8% 3 6% 5% 3 3 3 5% 6% 39%	2032
October	1st to 10th	Day	18% 7% 3 6% 5% 4 4 3 6% 7% 36%	1900
	11th to 20th	Day	18% 15% 4 8% 4 4 4 3 5% 7% 28%	1900
	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%	1679
	11th to 20th	Day	16% 18% 8% 17% 7% 4 4 2 5% 4 16%	1520
	21st to end	Day	16% 13% 7% 16% 8% 5% 5% 4 5% 5% 17%	1520
December	1st to 10th	Day	10% 19% 7% 19% 11% 7% 4 3 4 5% 11%	1520
	11th to 20th	Day	13% 16% 7% 19% 10% 9% 5% 4 4 3 9%	1914
	21st to end	Day	25% 17% 7% 14% 7% 5% 4 2 3 3 13%	2783
January	1st to 10th	Night	10% 19% 7% 17% 7% 7% 5% 3 3 4 18%	4428
	11th to 20th	Night	9% 15% 7% 16% 13% 14% 8% 2 4 4 8%	4440
	21st to end	Night	9% 17% 7% 15% 8% 7% 6% 3 5% 5% 17%	4870
February	1st to 10th	Night	8% 15% 5% 11% 8% 8% 8% 6% 5% 5% 23%	2470
	11th to 20th	Night	9% 9% 4 10% 8% 8% 6% 5% 7% 6% 28%	2403
	21st to end	Night	11% 14% 5% 9% 6% 4 5% 4 5% 7% 30%	1896
March	1st to 10th	Night	8% 9% 3 8% 5% 5% 4 4 5% 8% 41%	3722
	11th to 20th	Night	10% 11% 5% 11% 6% 5% 5% 3 5% 7% 32%	3543
	21st to end	Night	20% 12% 6% 11% 5% 5% 4 3 4 4 26%	3577
April	1st to 10th	Night	17% 13% 3 8% 5% 5% 4 4 5% 6% 30%	1900
	11th to 20th	Night	19% 11% 3 7% 5% 4 4 4 5% 5% 34%	1875
	21st to end	Night	19% 11% 3 8% 4 4 3 3 5% 6% 34%	1699
May	1st to 10th	Night	16% 7% 3 8% 6% 5% 5% 4 5% 6% 36%	2523
	11th to 20th	Night	15% 7% 2 5% 5% 5% 3 3 5% 7% 42%	2506
	21st to end	Night	15% 8% 3 10% 6% 4 5% 5% 6% 7% 32%	2750
June	1st to 10th	Night	14% 6% 2 6% 5% 4 5% 4 7% 7% 40%	1520
	11th to 20th	Night	13% 7% 3 6% 5% 6% 5% 4 7% 9% 35%	1520
	21st to end	Night	12% 7% 3 6% 4 5% 4 5% 6% 8% 40%	1520
July	1st to 10th	Night	8% 5% 2 7% 4 4 5% 4 6% 10% 45%	2530
	11th to 20th	Night	5% 4 2 5% 4 3 5% 4 6% 9% 52%	2530
	21st to end	Night	8% 5% 2 4 3 3 4 3 6% 7% 56%	2750
August	1st to 10th	Night	12% 5% 2 6% 4 4 4 4 6% 8% 45%	2517
	11th to 20th	Night	13% 5% 2 4 3 3 4 3 6% 7% 48%	2756
	21st to end	Night	15% 7% 2 6% 3 3 4 3 5% 7% 43%	3462
September	1st to 10th	Night	10% 6% 2 6% 3 4 4 4 5% 8% 48%	1900
	11th to 20th	Night	11% 5% 2 5% 4 4 5% 3 5% 8% 46%	1900
	21st to end	Night	17% 7% 2 6% 4 4 4 4 5% 7% 39%	2132
October	1st to 10th	Night	19% 7% 2 6% 4 3 4 4 4 5% 41%	2280
	11th to 20th	Night	17% 13% 4 8% 5% 4 5% 3 5% 6% 30%	2280
	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% 3 5% 6% 26%	2516
	11th to 20th	Night	15% 19% 8% 14% 6% 4 3 3 4 4 19%	2660
	21st to end	Night	15% 15% 6% 15% 8% 4 4 3 4 6% 19%	2660
December	1st to 10th	Night	12% 20% 6% 18% 9% 6% 5% 2 4 3 13%	2660
	11th to 20th	Night	11% 17% 6% 15% 10% 7% 4 3 4 4 16%	3283
	21st to end	Night	25% 22% 6% 11% 6% 4 4 2 3 3 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	74% 7% 8% 10% 2	2528
	11th to 20th	Day	81% 6% 7% 6% 1	2530
	21st to end	Day	66% 8% 14% 9% 2	2792
February	1st to 10th	Day	59% 6% 15% 16% 4	1710
	11th to 20th	Day	52% 7% 13% 21% 7%	1673
	21st to end	Day	54% 7% 12% 15% 11% 1	1557
March	1st to 10th	Day	43% 8% 15% 24% 10%	3120
	11th to 20th	Day	47% 8% 15% 18% 10%	3444
	21st to end	Day	55% 5% 12% 21% 6% 1	4053
April	1st to 10th	Day	49% 8% 10% 19% 13% 1	2280
	11th to 20th	Day	51% 6% 10% 19% 12% 2	2254
	21st to end	Day	50% 4 10% 24% 12% 1	2478
May	1st to 10th	Day	42% 6% 10% 24% 16% 1	4440
	11th to 20th	Day	41% 8% 14% 27% 10% 1	4403
	21st to end	Day	46% 9% 10% 19% 15% 1	4837
June	1st to 10th	Day	37% 7% 15% 26% 13% 1	2660
	11th to 20th	Day	41% 7% 12% 24% 15% 1	2660
	21st to end	Day	38% 8% 15% 27% 10% 1	2660
July	1st to 10th	Day	32% 7% 21% 25% 14% 1	4371
	11th to 20th	Day	25% 7% 17% 36% 13% 1	4365
	21st to end	Day	25% 7% 14% 36% 17% 1	4662
August	1st to 10th	Day	38% 6% 17% 27% 12% 1	4408
	11th to 20th	Day	30% 5% 20% 33% 11%	4120
	21st to end	Day	35% 7% 17% 30% 10% 1	4193
September	1st to 10th	Day	35% 7% 15% 34% 10%	2280
	11th to 20th	Day	37% 8% 19% 29% 7%	2275
	21st to end	Day	45% 6% 14% 26% 9%	2032
October	1st to 10th	Day	36% 5% 17% 30% 11% 1	3160
	11th to 20th	Day	50% 5% 11% 25% 10%	3140
	21st to end	Day	55% 6% 15% 19% 5%	3099
November	1st to 10th	Day	58% 5% 11% 18% 7% 1	1679
	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	71% 6% 10% 11% 3	4428
	11th to 20th	Night	80% 7% 9% 4	4440
	21st to end	Night	68% 7% 12% 12% 2	4870
February	1st to 10th	Night	62% 6% 13% 14% 5% 1	2470
	11th to 20th	Night	55% 7% 14% 18% 6%	2404
	21st to end	Night	55% 6% 11% 19% 8% 1	1896
March	1st to 10th	Night	41% 5% 16% 22% 14% 2	3733
	11th to 20th	Night	51% 7% 11% 23% 7% 1	3544
	21st to end	Night	61% 5% 7% 15% 10% 1	3577
April	1st to 10th	Night	55% 6% 8% 17% 13% 1	1900
	11th to 20th	Night	51% 5% 8% 22% 12% 2	1875
	21st to end	Night	50% 6% 7% 23% 14%	1699
May	1st to 10th	Night	47% 8% 11% 22% 11% 1	2530
	11th to 20th	Night	41% 7% 9% 25% 15% 3	2507
	21st to end	Night	48% 9% 11% 19% 11% 2	2751
June	1st to 10th	Night	40% 8% 13% 24% 14% 2	1520
	11th to 20th	Night	43% 8% 11% 20% 17% 1	1520
	21st to end	Night	41% 8% 12% 26% 12% 1	1520
July	1st to 10th	Night	34% 8% 17% 26% 12% 3	2490
	11th to 20th	Night	26% 7% 16% 37% 12% 1	2482
	21st to end	Night	27% 6% 12% 32% 21% 2	2662
August	1st to 10th	Night	36% 6% 14% 27% 14% 3	2508
	11th to 20th	Night	35% 5% 18% 30% 12% 1	2782
	21st to end	Night	39% 7% 14% 27% 11% 1	3462
September	1st to 10th	Night	34% 7% 13% 32% 13% 1	1900
	11th to 20th	Night	36% 6% 16% 35% 7%	1900
	21st to end	Night	44% 6% 15% 25% 9%	2132
October	1st to 10th	Night	32% 4 11% 33% 19% 1	3800
	11th to 20th	Night	50% 4 11% 21% 13%	3779
	21st to end	Night	57% 5% 11% 20% 7%	4436
November	1st to 10th	Night	60% 5% 10% 18% 6% 1	2516
	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	16% 4 30% 31% 17% 2	270
	21st to end	Day	14% 4 28% 37% 15% 2	297
February	1st to 10th	Day	14% 5% 27% 38% 13% 3	270
	11th to 20th	Day	12% 7% 36% 29% 15% 2	270
	21st to end	Day	16% 3 28% 47% 6%	225
March	1st to 10th	Day	13% 6% 20% 42% 18% 1	270
	11th to 20th	Day	13% 4 22% 42% 14% 5%	270
	21st to end	Day	21% 5% 21% 33% 17% 3	433
April	1st to 10th	Day	21% 5% 19% 38% 14% 2	460
	11th to 20th	Day	23% 6% 17% 34% 18% 2	452
	21st to end	Day	25% 5% 18% 29% 19% 4	559
May	1st to 10th	Day	19% 4 15% 40% 18% 4	653
	11th to 20th	Day	18% 4 12% 37% 22% 7%	675
	21st to end	Day	19% 4 13% 32% 28% 5%	734
June	1st to 10th	Day	11% 2 15% 37% 29% 6%	680
	11th to 20th	Day	14% 2 16% 37% 27% 4	680
	21st to end	Day	16% 2 13% 36% 27% 7%	680
July	1st to 10th	Day	8% 2 8% 34% 37% 11%	671
	11th to 20th	Day	9% 1 11% 36% 32% 11%	668
	21st to end	Day	7% 2 9% 35% 35% 12%	739
August	1st to 10th	Day	12% 3 11% 33% 34% 8%	676
	11th to 20th	Day	13% 1 11% 28% 35% 12%	665
	21st to end	Day	15% 3 16% 29% 29% 8%	553
September	1st to 10th	Day	15% 2 15% 32% 29% 8%	490
	11th to 20th	Day	13% 2 16% 34% 27% 8%	490
	21st to end	Day	24% 4 18% 26% 22% 7%	432
October	1st to 10th	Day	18% 7% 21% 25% 23% 5%	300
	11th to 20th	Day	21% 8% 29% 24% 16% 2	300
	21st to end	Day	28% 8% 25% 29% 9% 1	330
November	1st to 10th	Day	19% 9% 26% 32% 13% 1	285
	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% 7% 33% 34% 11% 1	950
	11th to 20th	Night	19% 5% 34% 30% 11% 1	950
	21st to end	Night	18% 4 30% 37% 10% 1	1045
February	1st to 10th	Night	16% 5% 32% 33% 13% 1	950
	11th to 20th	Night	15% 3 33% 33% 15% 2	929
	21st to end	Night	19% 4 26% 38% 12% 1	640
March	1st to 10th	Night	14% 5% 24% 41% 14% 2	760
	11th to 20th	Night	19% 4 28% 35% 13% 2	608
	21st to end	Night	19% 5% 22% 34% 16% 5%	627
April	1st to 10th	Night	22% 6% 21% 35% 14% 2	570
	11th to 20th	Night	24% 6% 18% 34% 17% 3	563
	21st to end	Night	25% 4 15% 32% 21% 4	570
May	1st to 10th	Night	19% 5% 22% 36% 16% 4	570
	11th to 20th	Night	18% 3 14% 38% 23% 4	561
	21st to end	Night	18% 2 15% 27% 33% 5%	617
June	1st to 10th	Night	15% 3 14% 37% 26% 5%	570
	11th to 20th	Night	17% 2 13% 40% 25% 4	570
	21st to end	Night	15% 3 13% 33% 29% 7%	570
July	1st to 10th	Night	9% 1 9% 36% 37% 8%	555
	11th to 20th	Night	8% 3 14% 34% 34% 7%	552
	21st to end	Night	9% 1 11% 35% 36% 8%	624
August	1st to 10th	Night	12% 1 11% 35% 36% 5%	567
	11th to 20th	Night	13% 3 12% 29% 35% 9%	564
	21st to end	Night	15% 2 14% 34% 30% 5%	627
September	1st to 10th	Night	11% 3 17% 32% 29% 7%	570
	11th to 20th	Night	13% 2 16% 38% 27% 3	570
	21st to end	Night	21% 4 21% 27% 22% 5%	746
October	1st to 10th	Night	22% 5% 23% 28% 19% 4	760
	11th to 20th	Night	26% 8% 30% 24% 12% 1	760
	21st to end	Night	28% 8% 25% 27% 12%	836
November	1st to 10th	Night	23% 8% 25% 31% 12% 1	797
	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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