Manitowoc
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Manitowoc clear sky chart from 2005-11-06 to 2026-01-17.

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% 8% 3 7% 5% 4 5% 4 6% 7% 39%	127488
	Night	13% 9% 3 7% 4 4 4 4 5% 7% 39%	124456
Transparency	Day	42% 7% 14% 24% 12% 1	130975
	Night	44% 6% 13% 22% 13% 2	129043
Seeing	Day	14% 8% 27% 30% 17% 4	17560
	Night	17% 9% 28% 29% 15% 2	27503

By Month

Percentage Cloud Cover SE (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% 9% 4 11% 5% 5% 5% 5% 6% 7% 33%	3697
	11th to 20th	Day	11% 10% 4 9% 5% 4 6% 7% 5% 6% 33%	3668
	21st to end	Day	14% 15% 6% 8% 5% 4 4 3 4 7% 30%	3982
February	1st to 10th	Day	10% 12% 5% 10% 5% 4 5% 4 6% 7% 31%	1747
	11th to 20th	Day	12% 11% 4 9% 5% 5% 4 4 6% 6% 36%	1948
	21st to end	Day	12% 11% 4 9% 5% 4 5% 4 5% 7% 33%	1650
March	1st to 10th	Day	14% 6% 2 6% 4 4 4 3 5% 7% 45%	4480
	11th to 20th	Day	12% 8% 3 6% 5% 4 5% 4 6% 8% 39%	4648
	21st to end	Day	22% 11% 3 10% 5% 4 4 3 5% 4 29%	5967
April	1st to 10th	Day	15% 12% 4 8% 5% 5% 5% 3 5% 6% 31%	2400
	11th to 20th	Day	17% 8% 3 7% 5% 5% 5% 4 5% 6% 35%	2374
	21st to end	Day	16% 9% 3 8% 5% 5% 5% 4 5% 7% 34%	2583
May	1st to 10th	Day	14% 7% 3 6% 4 4 4 4 5% 7% 44%	5897
	11th to 20th	Day	12% 9% 4 7% 4 5% 4 4 6% 7% 39%	6319
	21st to end	Day	15% 7% 3 6% 5% 4 4 4 5% 7% 40%	6935
June	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 5% 6% 8% 42%	2800
	11th to 20th	Day	13% 6% 2 5% 4 5% 5% 4 7% 9% 40%	2800
	21st to end	Day	9% 5% 2 7% 5% 4 5% 4 7% 9% 43%	2800
July	1st to 10th	Day	11% 5% 2 6% 5% 4 5% 4 7% 9% 40%	6360
	11th to 20th	Day	7% 4 1 5% 4 4 5% 4 7% 10% 50%	6360
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 4 6% 9% 46%	6924
August	1st to 10th	Day	9% 5% 2 7% 4 5% 5% 4 6% 9% 44%	4544
	11th to 20th	Day	10% 5% 2 5% 4 4 5% 4 6% 8% 48%	4050
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 4 6% 8% 44%	4312
September	1st to 10th	Day	11% 4 2 6% 5% 4 4 5% 6% 8% 45%	2400
	11th to 20th	Day	11% 4 2 6% 5% 4 4 3 5% 8% 47%	2264
	21st to end	Day	11% 6% 2 8% 5% 4 4 4 6% 7% 42%	2200
October	1st to 10th	Day	13% 7% 2 5% 4 4 4 3 6% 7% 45%	2149
	11th to 20th	Day	19% 8% 3 9% 6% 5% 5% 4 5% 7% 30%	1928
	21st to end	Day	15% 9% 3 8% 5% 5% 4 4 6% 7% 34%	1980
November	1st to 10th	Day	13% 8% 3 5% 5% 4 4 4 6% 8% 41%	1852
	11th to 20th	Day	11% 12% 4 8% 6% 5% 4 4 6% 7% 32%	1890
	21st to end	Day	16% 13% 3 7% 5% 4 4 3 4 7% 33%	1732
December	1st to 10th	Day	12% 11% 4 7% 6% 5% 6% 4 6% 7% 31%	2690
	11th to 20th	Day	13% 14% 4 9% 5% 5% 5% 4 7% 7% 27%	3088
	21st to end	Day	20% 19% 6% 10% 5% 4 4 3 4 5% 18%	4070
January	1st to 10th	Night	11% 12% 4 9% 4 4 4 3 5% 7% 37%	6488
	11th to 20th	Night	11% 12% 4 10% 6% 5% 6% 6% 6% 6% 27%	6445
	21st to end	Night	11% 15% 5% 9% 4 4 4 3 5% 7% 33%	6996
February	1st to 10th	Night	13% 13% 5% 8% 5% 5% 4 4 5% 5% 33%	2646
	11th to 20th	Night	11% 12% 4 8% 5% 5% 4 4 6% 5% 37%	2338
	21st to end	Night	15% 14% 4 6% 3 4 5% 3 5% 6% 37%	1980
March	1st to 10th	Night	15% 7% 2 5% 4 3 4 3 5% 7% 45%	5373
	11th to 20th	Night	11% 8% 3 6% 5% 4 5% 4 6% 8% 42%	5330
	21st to end	Night	19% 10% 3 9% 5% 5% 4 4 4 5% 32%	4972
April	1st to 10th	Night	16% 11% 4 7% 4 4 3 3 5% 6% 36%	2000
	11th to 20th	Night	20% 8% 3 6% 4 3 3 3 5% 5% 40%	1975
	21st to end	Night	17% 8% 3 8% 5% 4 4 3 5% 6% 38%	1815
May	1st to 10th	Night	14% 7% 2 6% 4 4 4 4 5% 7% 42%	3998
	11th to 20th	Night	10% 8% 4 7% 5% 4 4 4 5% 7% 41%	3596
	21st to end	Night	19% 7% 3 6% 4 4 4 3 5% 6% 39%	3942
June	1st to 10th	Night	11% 5% 2 5% 6% 5% 5% 4 5% 7% 45%	1600
	11th to 20th	Night	12% 6% 3 7% 4 4 4 4 5% 8% 43%	1600
	21st to end	Night	9% 6% 2 6% 4 4 5% 4 6% 8% 46%	1600
July	1st to 10th	Night	11% 5% 2 6% 4 4 5% 5% 6% 8% 45%	3618
	11th to 20th	Night	7% 4 2 5% 3 3 3 3 6% 9% 55%	3617
	21st to end	Night	5% 4 2 6% 4 4 4 4 6% 9% 52%	3947
August	1st to 10th	Night	10% 5% 2 6% 4 3 5% 3 6% 8% 46%	2614
	11th to 20th	Night	11% 4 2 5% 4 3 5% 3 5% 7% 50%	2997
	21st to end	Night	11% 4 2 5% 4 4 4 4 5% 7% 49%	3586
September	1st to 10th	Night	9% 5% 2 6% 3 4 4 4 5% 8% 52%	2000
	11th to 20th	Night	10% 4 2 5% 3 4 4 3 5% 7% 54%	2115
	21st to end	Night	12% 6% 2 7% 4 5% 4 3 5% 7% 45%	2200
October	1st to 10th	Night	13% 6% 2 5% 3 3 4 3 5% 6% 49%	2249
	11th to 20th	Night	17% 8% 2 7% 4 4 5% 3 5% 6% 39%	2470
	21st to end	Night	18% 8% 3 7% 4 4 4 3 5% 7% 37%	2860
November	1st to 10th	Night	13% 8% 2 5% 4 4 4 3 5% 6% 45%	2666
	11th to 20th	Night	14% 10% 3 8% 5% 5% 4 3 6% 6% 36%	2730
	21st to end	Night	17% 10% 3 6% 5% 4 5% 4 5% 6% 37%	2884
December	1st to 10th	Night	12% 10% 3 7% 4 4 4 4 5% 7% 39%	4720
	11th to 20th	Night	16% 17% 5% 9% 5% 5% 5% 3 4 5% 26%	5339
	21st to end	Night	22% 16% 5% 9% 5% 4 5% 3 5% 6% 21%	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	50% 9% 17% 17% 6%	3698
	11th to 20th	Day	48% 9% 15% 19% 8%	3668
	21st to end	Day	55% 6% 11% 17% 11%	3982
February	1st to 10th	Day	52% 10% 15% 16% 7% 1	1747
	11th to 20th	Day	49% 8% 13% 19% 10% 1	1958
	21st to end	Day	50% 8% 13% 19% 10% 1	1650
March	1st to 10th	Day	39% 7% 14% 19% 15% 6%	4480
	11th to 20th	Day	40% 5% 18% 22% 12% 2	4648
	21st to end	Day	57% 6% 10% 17% 9%	5969
April	1st to 10th	Day	52% 8% 12% 17% 11%	2400
	11th to 20th	Day	48% 7% 10% 20% 13% 2	2374
	21st to end	Day	47% 8% 13% 18% 12% 2	2583
May	1st to 10th	Day	38% 7% 13% 24% 16% 3	5932
	11th to 20th	Day	40% 7% 14% 24% 14% 1	6323
	21st to end	Day	41% 6% 10% 26% 14% 3	6949
June	1st to 10th	Day	36% 8% 12% 27% 15% 2	2800
	11th to 20th	Day	38% 8% 13% 26% 14% 1	2800
	21st to end	Day	34% 10% 15% 25% 15% 1	2800
July	1st to 10th	Day	36% 8% 14% 31% 9% 1	6291
	11th to 20th	Day	27% 8% 16% 34% 14% 1	6285
	21st to end	Day	31% 8% 17% 24% 18% 2	6728
August	1st to 10th	Day	34% 8% 15% 30% 12% 1	4529
	11th to 20th	Day	31% 8% 13% 35% 11% 1	4089
	21st to end	Day	35% 8% 15% 24% 16% 1	4311
September	1st to 10th	Day	36% 9% 14% 27% 14% 1	2400
	11th to 20th	Day	36% 8% 15% 29% 12% 1	2264
	21st to end	Day	39% 8% 13% 30% 10% 1	2200
October	1st to 10th	Day	23% 5% 10% 38% 22% 2	3500
	11th to 20th	Day	44% 6% 11% 23% 15%	3118
	21st to end	Day	41% 6% 13% 28% 12% 1	3180
November	1st to 10th	Day	40% 9% 13% 23% 13% 2	1852
	11th to 20th	Day	50% 9% 15% 18% 8% 1	1890
	21st to end	Day	53% 6% 15% 19% 5% 1	1732
December	1st to 10th	Day	52% 9% 18% 16% 4	2690
	11th to 20th	Day	56% 7% 17% 13% 6% 1	3085
	21st to end	Day	68% 7% 10% 10% 5%	4070
January	1st to 10th	Night	49% 7% 13% 20% 11% 1	6488
	11th to 20th	Night	55% 9% 13% 12% 11%	6445
	21st to end	Night	52% 6% 16% 17% 9%	6996
February	1st to 10th	Night	53% 7% 11% 17% 10% 2	2646
	11th to 20th	Night	48% 7% 12% 21% 10% 1	2339
	21st to end	Night	49% 5% 14% 18% 11% 1	1980
March	1st to 10th	Night	40% 5% 15% 25% 12% 2	5373
	11th to 20th	Night	40% 6% 18% 22% 13% 2	5330
	21st to end	Night	55% 5% 10% 17% 11% 1	4972
April	1st to 10th	Night	49% 6% 9% 19% 17% 1	2000
	11th to 20th	Night	46% 4 8% 23% 15% 3	1975
	21st to end	Night	46% 5% 11% 22% 14% 2	1815
May	1st to 10th	Night	39% 6% 14% 19% 20% 2	4025
	11th to 20th	Night	40% 7% 14% 21% 16% 2	3597
	21st to end	Night	45% 6% 8% 23% 13% 5%	3950
June	1st to 10th	Night	35% 8% 11% 29% 16% 1	1600
	11th to 20th	Night	37% 6% 12% 24% 18% 2	1600
	21st to end	Night	35% 8% 14% 24% 16% 3	1600
July	1st to 10th	Night	35% 7% 13% 31% 11% 4	3580
	11th to 20th	Night	26% 5% 15% 33% 18% 3	3572
	21st to end	Night	28% 6% 15% 28% 21% 2	3832
August	1st to 10th	Night	33% 8% 13% 26% 19% 1	2605
	11th to 20th	Night	33% 7% 11% 31% 17%	3024
	21st to end	Night	33% 7% 13% 24% 20% 3	3586
September	1st to 10th	Night	31% 7% 12% 27% 21% 2	2000
	11th to 20th	Night	31% 7% 11% 33% 16% 1	2115
	21st to end	Night	39% 5% 11% 29% 15% 1	2200
October	1st to 10th	Night	27% 4 9% 39% 20% 1	3678
	11th to 20th	Night	37% 6% 15% 25% 16% 1	4019
	21st to end	Night	43% 5% 12% 24% 16%	4610
November	1st to 10th	Night	40% 7% 12% 24% 16% 2	2666
	11th to 20th	Night	50% 6% 15% 17% 11% 1	2730
	21st to end	Night	49% 7% 17% 20% 6% 1	2884
December	1st to 10th	Night	45% 7% 21% 20% 5% 1	4720
	11th to 20th	Night	61% 6% 11% 12% 9% 1	5341
	21st to end	Night	65% 7% 10% 12% 6%	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	16% 11% 35% 28% 11% 1	330
	11th to 20th	Day	18% 12% 39% 23% 7% 1	318
	21st to end	Day	20% 10% 34% 28% 7% 1	330
February	1st to 10th	Day	14% 17% 39% 24% 5% 1	300
	11th to 20th	Day	15% 16% 42% 20% 7%	300
	21st to end	Day	17% 14% 43% 23% 3	249
March	1st to 10th	Day	14% 16% 44% 21% 5%	300
	11th to 20th	Day	19% 13% 31% 26% 10% 2	345
	21st to end	Day	24% 11% 30% 26% 9% 1	550
April	1st to 10th	Day	22% 11% 34% 26% 8%	500
	11th to 20th	Day	20% 13% 32% 25% 8% 3	492
	21st to end	Day	18% 9% 32% 27% 12% 2	500
May	1st to 10th	Day	17% 6% 32% 31% 12% 2	512
	11th to 20th	Day	15% 4 29% 33% 14% 4	725
	21st to end	Day	14% 5% 23% 33% 21% 5%	789
June	1st to 10th	Day	11% 3 25% 38% 19% 4	730
	11th to 20th	Day	15% 3 23% 35% 21% 3	730
	21st to end	Day	11% 5% 20% 38% 22% 3	730
July	1st to 10th	Day	7% 2 15% 36% 32% 8%	721
	11th to 20th	Day	8% 2 19% 38% 26% 7%	718
	21st to end	Day	5% 2 18% 41% 27% 8%	794
August	1st to 10th	Day	7% 2 16% 38% 28% 9%	720
	11th to 20th	Day	11% 3 12% 31% 32% 11%	519
	21st to end	Day	13% 3 17% 29% 30% 8%	583
September	1st to 10th	Day	12% 5% 19% 32% 22% 9%	530
	11th to 20th	Day	10% 3 17% 32% 27% 12%	530
	21st to end	Day	15% 6% 23% 25% 26% 6%	530
October	1st to 10th	Day	16% 8% 22% 32% 18% 5%	479
	11th to 20th	Day	21% 15% 25% 31% 8% 1	330
	21st to end	Day	18% 11% 35% 22% 12% 2	363
November	1st to 10th	Day	13% 14% 30% 29% 13% 1	330
	11th to 20th	Day	14% 15% 40% 23% 8%	330
	21st to end	Day	20% 11% 38% 26% 5%	330
December	1st to 10th	Day	19% 15% 37% 21% 7% 1	330
	11th to 20th	Day	22% 16% 42% 14% 6% 1	330
	21st to end	Day	27% 18% 32% 17% 5% 1	363
January	1st to 10th	Night	18% 14% 40% 22% 6%	1050
	11th to 20th	Night	22% 13% 36% 23% 6%	1031
	21st to end	Night	19% 11% 38% 25% 7%	1100
February	1st to 10th	Night	20% 13% 38% 24% 5% 1	996
	11th to 20th	Night	16% 16% 38% 22% 8%	783
	21st to end	Night	23% 12% 36% 25% 4 1	660
March	1st to 10th	Night	20% 8% 34% 27% 10% 1	800
	11th to 20th	Night	15% 10% 37% 29% 9% 1	800
	21st to end	Night	21% 6% 28% 32% 11% 1	670
April	1st to 10th	Night	20% 9% 34% 30% 7% 1	600
	11th to 20th	Night	22% 7% 27% 30% 12% 2	593
	21st to end	Night	19% 6% 26% 32% 15% 1	600
May	1st to 10th	Night	18% 3 26% 38% 14% 1	600
	11th to 20th	Night	17% 4 23% 37% 17% 2	591
	21st to end	Night	15% 3 18% 36% 24% 4	650
June	1st to 10th	Night	11% 4 18% 43% 22% 2	600
	11th to 20th	Night	14% 3 20% 36% 25% 3	600
	21st to end	Night	10% 3 17% 41% 27% 3	600
July	1st to 10th	Night	9% 2 10% 38% 35% 6%	585
	11th to 20th	Night	6% 2 14% 39% 34% 5%	582
	21st to end	Night	5% 2 15% 41% 34% 3	657
August	1st to 10th	Night	8% 1 12% 40% 33% 5%	597
	11th to 20th	Night	8% 2 14% 35% 34% 7%	594
	21st to end	Night	11% 2 16% 35% 32% 4	660
September	1st to 10th	Night	9% 4 21% 33% 26% 7%	600
	11th to 20th	Night	10% 6% 17% 29% 28% 10%	715
	21st to end	Night	15% 7% 21% 27% 23% 6%	800
October	1st to 10th	Night	16% 6% 27% 28% 22% 3	800
	11th to 20th	Night	23% 11% 28% 27% 12%	800
	21st to end	Night	23% 10% 28% 26% 12% 1	880
November	1st to 10th	Night	17% 10% 33% 30% 9%	820
	11th to 20th	Night	20% 15% 34% 23% 8%	840
	21st to end	Night	23% 13% 33% 24% 7%	994
December	1st to 10th	Night	22% 16% 37% 20% 6%	1050
	11th to 20th	Night	22% 16% 35% 20% 6% 1	1050
	21st to end	Night	27% 14% 34% 21% 4	1155

Page generated at 2026-01-14 00:14:25. Version ac07

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