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 2024-01-14.

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% 8% 3 6% 6% 3 5% 5% 6% 8% 38%	74816
	Night	14% 9% 3 6% 5% 3 5% 4 5% 7% 38%	74962
Transparency	Day	44% 8% 14% 22% 11% 1	74517
	Night	46% 7% 13% 21% 12% 1	74782
Seeing	Day	15% 7% 27% 30% 17% 4	14767
	Night	18% 9% 28% 29% 15% 2	24763

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	13% 9% 5% 6% 6% 3 4 6% 8% 9% 31%	1517
	11th to 20th	Day	15% 14% 6% 10% 7% 4 5% 6% 6% 6% 21%	1464
	21st to end	Day	12% 15% 6% 10% 8% 3 5% 5% 5% 7% 25%	1584
February	1st to 10th	Day	10% 11% 6% 9% 6% 3 5% 5% 5% 8% 31%	1571
	11th to 20th	Day	13% 11% 4 7% 6% 3 4 5% 6% 6% 36%	1748
	21st to end	Day	13% 11% 4 9% 6% 4 5% 5% 5% 7% 32%	1480
March	1st to 10th	Day	14% 8% 4 7% 7% 4 5% 5% 5% 7% 36%	1800
	11th to 20th	Day	11% 10% 5% 6% 6% 3 4 5% 6% 8% 37%	1844
	21st to end	Day	16% 9% 4 7% 6% 4 5% 5% 6% 6% 31%	2376
April	1st to 10th	Day	15% 11% 5% 8% 6% 4 5% 5% 5% 6% 30%	2160
	11th to 20th	Day	18% 8% 3 7% 6% 4 5% 5% 4 6% 35%	2134
	21st to end	Day	17% 9% 3 6% 6% 3 5% 5% 5% 7% 34%	2324
May	1st to 10th	Day	15% 7% 3 5% 6% 3 6% 6% 6% 7% 36%	2347
	11th to 20th	Day	16% 6% 3 5% 5% 3 5% 5% 5% 6% 41%	2479
	21st to end	Day	11% 6% 3 6% 5% 3 7% 5% 7% 7% 40%	2725
June	1st to 10th	Day	11% 5% 2 5% 6% 3 5% 5% 5% 9% 43%	2520
	11th to 20th	Day	13% 5% 2 4 5% 3 5% 5% 6% 9% 43%	2520
	21st to end	Day	9% 5% 2 6% 5% 3 5% 5% 7% 9% 44%	2520
July	1st to 10th	Day	5% 3 2 5% 5% 3 5% 6% 8% 11% 48%	2520
	11th to 20th	Day	8% 4 2 4 5% 3 5% 5% 6% 9% 50%	2520
	21st to end	Day	6% 4 2 4 5% 3 5% 5% 5% 10% 50%	2743
August	1st to 10th	Day	7% 4 2 5% 6% 3 5% 5% 7% 10% 45%	2503
	11th to 20th	Day	9% 4 2 5% 4 3 5% 6% 6% 9% 47%	2239
	21st to end	Day	10% 5% 2 4 5% 4 4 4 5% 8% 48%	2376
September	1st to 10th	Day	12% 4 2 6% 6% 3 5% 5% 6% 8% 44%	2160
	11th to 20th	Day	12% 4 2 5% 6% 3 4 4 5% 8% 46%	2038
	21st to end	Day	11% 6% 3 7% 7% 3 5% 5% 6% 7% 41%	1980
October	1st to 10th	Day	14% 7% 3 5% 5% 3 4 5% 5% 7% 43%	1935
	11th to 20th	Day	21% 8% 3 7% 7% 4 5% 5% 5% 7% 29%	1736
	21st to end	Day	16% 9% 4 7% 6% 4 4 5% 5% 7% 32%	1782
November	1st to 10th	Day	13% 8% 2 4 5% 3 4 5% 6% 8% 42%	1672
	11th to 20th	Day	11% 11% 5% 7% 7% 4 5% 5% 6% 7% 32%	1710
	21st to end	Day	17% 11% 4 6% 5% 3 4 4 4 7% 35%	1568
December	1st to 10th	Day	15% 10% 5% 7% 8% 5% 6% 4 6% 8% 26%	1520
	11th to 20th	Day	14% 10% 4 9% 7% 4 6% 6% 7% 7% 25%	1918
	21st to end	Day	20% 17% 8% 9% 7% 4 4 5% 5% 5% 17%	2783
January	1st to 10th	Night	13% 12% 6% 8% 6% 3 5% 4 6% 8% 31%	2648
	11th to 20th	Night	16% 15% 6% 8% 6% 3 4 6% 5% 6% 25%	2569
	21st to end	Night	14% 12% 5% 10% 6% 3 6% 5% 6% 9% 25%	2772
February	1st to 10th	Night	13% 13% 5% 7% 6% 4 4 5% 4 5% 33%	2382
	11th to 20th	Night	12% 11% 5% 7% 5% 3 5% 5% 6% 5% 36%	2098
	21st to end	Night	16% 14% 4 5% 4 2 5% 4 5% 6% 36%	1776
March	1st to 10th	Night	14% 8% 4 6% 5% 4 4 4 6% 6% 37%	2160
	11th to 20th	Night	12% 6% 3 5% 5% 3 5% 5% 6% 7% 42%	2120
	21st to end	Night	19% 8% 3 6% 5% 3 5% 4 5% 6% 36%	1990
April	1st to 10th	Night	16% 10% 5% 6% 5% 3 4 4 5% 7% 35%	1800
	11th to 20th	Night	20% 7% 3 6% 4 2 4 3 5% 6% 39%	1775
	21st to end	Night	17% 8% 3 7% 6% 3 4 4 5% 6% 37%	1634
May	1st to 10th	Night	16% 7% 4 6% 6% 3 5% 5% 6% 7% 34%	1611
	11th to 20th	Night	18% 7% 3 6% 6% 3 3 5% 4 7% 40%	1416
	21st to end	Night	13% 5% 3 5% 4 3 4 5% 7% 9% 42%	1551
June	1st to 10th	Night	11% 5% 2 4 6% 4 5% 5% 5% 7% 46%	1440
	11th to 20th	Night	11% 5% 3 5% 5% 3 5% 5% 5% 9% 45%	1440
	21st to end	Night	8% 4 3 5% 4 3 5% 6% 6% 9% 47%	1440
July	1st to 10th	Night	7% 3 2 3 5% 2 4 6% 7% 8% 52%	1440
	11th to 20th	Night	6% 4 2 5% 5% 3 5% 5% 6% 8% 52%	1440
	21st to end	Night	6% 4 2 5% 5% 3 5% 4 6% 9% 52%	1575
August	1st to 10th	Night	7% 5% 2 5% 5% 3 5% 5% 7% 10% 47%	1436
	11th to 20th	Night	8% 4 2 4 4 3 5% 4 6% 8% 53%	1660
	21st to end	Night	10% 4 1 4 5% 3 4 4 5% 7% 53%	1980
September	1st to 10th	Night	9% 5% 2 5% 5% 3 4 5% 5% 8% 51%	1800
	11th to 20th	Night	11% 4 2 4 4 2 4 3 5% 7% 54%	1903
	21st to end	Night	12% 6% 2 6% 6% 4 5% 4 5% 8% 43%	1980
October	1st to 10th	Night	14% 6% 2 5% 4 3 4 4 5% 6% 47%	2023
	11th to 20th	Night	18% 7% 3 6% 5% 3 5% 4 5% 6% 38%	2222
	21st to end	Night	19% 8% 4 6% 5% 3 4 4 5% 7% 35%	2574
November	1st to 10th	Night	12% 7% 2 4 5% 3 4 4 5% 6% 46%	2406
	11th to 20th	Night	15% 9% 4 7% 6% 4 4 4 5% 6% 35%	2470
	21st to end	Night	17% 9% 3 5% 5% 2 5% 5% 5% 6% 38%	2608
December	1st to 10th	Night	15% 11% 4 8% 6% 4 6% 5% 5% 8% 28%	2660
	11th to 20th	Night	16% 13% 4 7% 6% 4 6% 6% 5% 6% 28%	3279
	21st to end	Night	22% 18% 5% 8% 6% 3 5% 4 4 6% 20%	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	49% 12% 18% 15% 6% 1	1518
	11th to 20th	Day	63% 8% 15% 11% 3	1464
	21st to end	Day	60% 9% 14% 11% 5%	1584
February	1st to 10th	Day	53% 10% 15% 16% 6%	1571
	11th to 20th	Day	49% 8% 13% 18% 10% 2	1758
	21st to end	Day	52% 8% 12% 18% 10% 1	1480
March	1st to 10th	Day	48% 9% 15% 19% 8% 2	1800
	11th to 20th	Day	45% 7% 14% 18% 13% 2	1844
	21st to end	Day	52% 8% 13% 20% 7% 1	2376
April	1st to 10th	Day	52% 8% 12% 17% 11%	2160
	11th to 20th	Day	49% 7% 10% 19% 13% 2	2134
	21st to end	Day	49% 8% 12% 18% 12% 2	2324
May	1st to 10th	Day	44% 9% 12% 23% 10% 1	2347
	11th to 20th	Day	43% 7% 12% 24% 13% 2	2483
	21st to end	Day	40% 8% 13% 23% 14% 2	2725
June	1st to 10th	Day	35% 8% 11% 28% 15% 2	2520
	11th to 20th	Day	36% 8% 13% 27% 15% 1	2520
	21st to end	Day	33% 10% 16% 25% 15% 1	2520
July	1st to 10th	Day	27% 10% 14% 32% 14% 3	2451
	11th to 20th	Day	29% 9% 15% 27% 17% 3	2445
	21st to end	Day	28% 9% 16% 26% 18% 3	2591
August	1st to 10th	Day	30% 10% 18% 29% 11% 2	2488
	11th to 20th	Day	31% 10% 16% 29% 13% 2	2239
	21st to end	Day	34% 8% 14% 27% 16% 1	2376
September	1st to 10th	Day	37% 9% 13% 25% 14% 1	2160
	11th to 20th	Day	37% 8% 15% 28% 11% 1	2038
	21st to end	Day	40% 8% 14% 29% 8%	1980
October	1st to 10th	Day	40% 8% 13% 27% 11% 1	1935
	11th to 20th	Day	53% 8% 13% 18% 8% 1	1736
	21st to end	Day	51% 7% 14% 18% 9%	1782
November	1st to 10th	Day	40% 9% 13% 24% 14% 1	1672
	11th to 20th	Day	51% 9% 16% 17% 6% 1	1710
	21st to end	Day	53% 7% 16% 19% 5% 1	1568
December	1st to 10th	Day	58% 10% 14% 13% 5%	1520
	11th to 20th	Day	57% 7% 16% 13% 5% 2	1915
	21st to end	Day	70% 8% 9% 10% 4	2783
January	1st to 10th	Night	54% 7% 17% 12% 9% 1	2648
	11th to 20th	Night	60% 8% 16% 12% 4	2569
	21st to end	Night	57% 7% 16% 13% 7%	2772
February	1st to 10th	Night	54% 7% 11% 18% 9% 1	2382
	11th to 20th	Night	49% 7% 13% 19% 10% 2	2099
	21st to end	Night	51% 6% 13% 17% 12% 1	1776
March	1st to 10th	Night	46% 7% 16% 21% 9% 1	2160
	11th to 20th	Night	40% 8% 13% 23% 14% 2	2120
	21st to end	Night	51% 5% 10% 23% 10% 1	1990
April	1st to 10th	Night	50% 6% 8% 19% 16% 1	1800
	11th to 20th	Night	47% 4 9% 21% 16% 4	1775
	21st to end	Night	47% 5% 11% 21% 14% 2	1634
May	1st to 10th	Night	46% 8% 13% 19% 12% 2	1611
	11th to 20th	Night	46% 7% 9% 22% 14% 3	1417
	21st to end	Night	37% 8% 12% 25% 16% 2	1552
June	1st to 10th	Night	35% 8% 11% 29% 16% 2	1440
	11th to 20th	Night	35% 7% 13% 25% 19% 2	1440
	21st to end	Night	33% 8% 15% 26% 15% 3	1440
July	1st to 10th	Night	26% 9% 13% 31% 18% 3	1400
	11th to 20th	Night	28% 8% 12% 29% 18% 4	1392
	21st to end	Night	28% 7% 15% 28% 18% 4	1487
August	1st to 10th	Night	29% 8% 15% 30% 15% 3	1427
	11th to 20th	Night	29% 8% 14% 30% 18% 1	1660
	21st to end	Night	31% 8% 12% 28% 19% 2	1980
September	1st to 10th	Night	33% 7% 12% 24% 22% 2	1800
	11th to 20th	Night	31% 7% 12% 34% 14% 1	1903
	21st to end	Night	41% 5% 12% 29% 13% 1	1980
October	1st to 10th	Night	37% 7% 11% 28% 16% 1	2023
	11th to 20th	Night	47% 6% 16% 19% 11% 1	2222
	21st to end	Night	49% 6% 16% 19% 10%	2574
November	1st to 10th	Night	39% 7% 11% 24% 17% 2	2406
	11th to 20th	Night	51% 6% 15% 15% 11% 1	2470
	21st to end	Night	48% 7% 18% 21% 6% 1	2608
December	1st to 10th	Night	57% 8% 14% 16% 4	2660
	11th to 20th	Night	57% 8% 13% 13% 7% 1	3281
	21st to end	Night	67% 7% 10% 12% 4	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	16% 11% 36% 25% 11% 1	270
	11th to 20th	Day	22% 9% 35% 24% 8% 1	249
	21st to end	Day	19% 11% 33% 29% 8% 1	264
February	1st to 10th	Day	14% 18% 41% 24% 4	240
	11th to 20th	Day	15% 18% 42% 19% 6%	240
	21st to end	Day	20% 14% 44% 20% 2	198
March	1st to 10th	Day	14% 17% 48% 17% 4	240
	11th to 20th	Day	20% 12% 28% 28% 10% 2	280
	21st to end	Day	23% 10% 32% 25% 9% 1	462
April	1st to 10th	Day	21% 10% 35% 26% 9%	420
	11th to 20th	Day	20% 13% 30% 24% 9% 4	412
	21st to end	Day	19% 8% 31% 26% 13% 2	420
May	1st to 10th	Day	19% 6% 34% 29% 11% 2	430
	11th to 20th	Day	16% 3 29% 34% 13% 3	625
	21st to end	Day	13% 4 23% 31% 23% 6%	679
June	1st to 10th	Day	11% 3 25% 37% 20% 4	630
	11th to 20th	Day	15% 3 24% 34% 20% 4	630
	21st to end	Day	10% 5% 21% 37% 23% 3	630
July	1st to 10th	Day	6% 2 17% 35% 32% 8%	621
	11th to 20th	Day	9% 2 20% 39% 23% 7%	618
	21st to end	Day	5% 1 20% 41% 25% 7%	684
August	1st to 10th	Day	7% 2 17% 39% 27% 8%	622
	11th to 20th	Day	10% 3 14% 31% 32% 10%	439
	21st to end	Day	14% 3 19% 29% 28% 7%	495
September	1st to 10th	Day	13% 5% 20% 33% 21% 8%	450
	11th to 20th	Day	12% 4 19% 35% 23% 8%	450
	21st to end	Day	15% 7% 25% 24% 23% 5%	450
October	1st to 10th	Day	19% 8% 23% 30% 16% 4	405
	11th to 20th	Day	23% 16% 26% 27% 7% 1	270
	21st to end	Day	21% 12% 38% 20% 7% 1	297
November	1st to 10th	Day	14% 15% 29% 27% 13% 1	270
	11th to 20th	Day	13% 15% 42% 23% 7%	270
	21st to end	Day	21% 11% 39% 24% 5%	270
December	1st to 10th	Day	19% 17% 38% 20% 6%	270
	11th to 20th	Day	23% 17% 40% 13% 6% 1	270
	21st to end	Day	26% 20% 34% 15% 5%	297
January	1st to 10th	Night	19% 14% 40% 21% 6%	950
	11th to 20th	Night	23% 12% 34% 25% 6%	918
	21st to end	Night	20% 11% 37% 24% 7%	990
February	1st to 10th	Night	21% 13% 37% 25% 4 1	897
	11th to 20th	Night	17% 15% 37% 23% 8%	703
	21st to end	Night	25% 12% 37% 22% 4 1	592
March	1st to 10th	Night	19% 9% 33% 27% 11% 1	720
	11th to 20th	Night	14% 9% 37% 28% 10% 1	720
	21st to end	Night	21% 6% 27% 32% 12% 1	604
April	1st to 10th	Night	20% 9% 34% 29% 7% 1	540
	11th to 20th	Night	23% 6% 26% 31% 13% 2	533
	21st to end	Night	21% 6% 25% 32% 16% 1	540
May	1st to 10th	Night	19% 3 26% 38% 13% 1	540
	11th to 20th	Night	19% 4 23% 36% 17% 2	531
	21st to end	Night	14% 2 18% 36% 25% 5%	584
June	1st to 10th	Night	11% 3 18% 43% 22% 3	540
	11th to 20th	Night	14% 2 20% 35% 26% 4	540
	21st to end	Night	10% 2 17% 41% 28% 3	540
July	1st to 10th	Night	8% 2 10% 39% 35% 6%	525
	11th to 20th	Night	6% 2 16% 39% 33% 5%	522
	21st to end	Night	6% 2 16% 43% 32% 3	591
August	1st to 10th	Night	9% 1 12% 41% 33% 4	537
	11th to 20th	Night	8% 2 14% 35% 33% 8%	534
	21st to end	Night	11% 2 17% 34% 32% 4	594
September	1st to 10th	Night	10% 4 21% 33% 26% 7%	540
	11th to 20th	Night	11% 6% 19% 31% 26% 7%	643
	21st to end	Night	16% 7% 23% 25% 23% 6%	720
October	1st to 10th	Night	17% 6% 27% 26% 21% 3	720
	11th to 20th	Night	24% 11% 28% 25% 12%	720
	21st to end	Night	24% 10% 29% 26% 9% 1	792
November	1st to 10th	Night	16% 11% 33% 30% 10% 1	740
	11th to 20th	Night	21% 15% 33% 23% 8%	760
	21st to end	Night	23% 13% 33% 24% 7%	898
December	1st to 10th	Night	22% 16% 37% 19% 6%	950
	11th to 20th	Night	23% 15% 35% 21% 6% 1	950
	21st to end	Night	27% 15% 35% 21% 3	1045

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