South Haven Pier
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the South Haven Pier clear sky chart from 2005-11-06 to 2025-11-18.

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	14% 11% 4 9% 5% 4 4 3 5% 7% 35%	126681
	Night	16% 14% 5% 10% 5% 4 4 3 4 5% 30%	123896
Transparency	Day	49% 3 11% 23% 12% 1	130220
	Night	56% 3 9% 19% 11% 1	128431
Seeing	Day	20% 16% 30% 21% 10% 3	17227
	Night	22% 14% 27% 25% 11% 1	27048

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% 23% 11% 21% 6% 3 3 2 3 3 11%	3617
	11th to 20th	Day	11% 20% 7% 23% 13% 9% 5% 2 2 2 6%	3620
	21st to end	Day	19% 19% 8% 17% 6% 3 6% 2 3 3 14%	3982
February	1st to 10th	Day	14% 18% 6% 17% 10% 5% 4 3 3 4 16%	1866
	11th to 20th	Day	14% 16% 7% 19% 8% 4 3 3 3 4 20%	1948
	21st to end	Day	16% 14% 6% 13% 6% 5% 4 3 5% 6% 22%	1650
March	1st to 10th	Day	15% 12% 5% 11% 5% 4 4 3 4 6% 32%	4480
	11th to 20th	Day	10% 9% 7% 8% 4 4 4 3 6% 8% 36%	4786
	21st to end	Day	19% 14% 7% 11% 5% 4 4 3 5% 5% 25%	5772
April	1st to 10th	Day	18% 14% 4 7% 4 4 4 3 5% 7% 30%	2400
	11th to 20th	Day	16% 11% 3 6% 3 4 4 3 5% 5% 40%	2391
	21st to end	Day	17% 9% 3 7% 4 4 4 3 6% 7% 36%	2600
May	1st to 10th	Day	18% 7% 2 6% 4 4 4 4 5% 7% 38%	5862
	11th to 20th	Day	14% 6% 2 6% 4 4 4 3 5% 8% 42%	5905
	21st to end	Day	16% 6% 2 5% 3 3 3 3 5% 7% 46%	6935
June	1st to 10th	Day	10% 5% 2 5% 4 4 4 4 5% 7% 48%	2800
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 7% 9% 47%	2800
	21st to end	Day	12% 5% 2 6% 4 4 3 4 6% 8% 46%	2800
July	1st to 10th	Day	12% 6% 2 6% 4 4 4 3 7% 10% 42%	6360
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 6% 9% 49%	6360
	21st to end	Day	9% 5% 2 6% 4 4 4 4 6% 9% 47%	6924
August	1st to 10th	Day	11% 5% 2 5% 4 3 4 3 6% 8% 48%	4307
	11th to 20th	Day	11% 5% 2 5% 3 4 4 4 5% 7% 51%	4119
	21st to end	Day	8% 4 2 6% 4 4 4 3 6% 9% 50%	4312
September	1st to 10th	Day	10% 5% 2 5% 4 4 5% 3 6% 8% 47%	2392
	11th to 20th	Day	11% 5% 2 5% 3 4 4 3 6% 8% 50%	2200
	21st to end	Day	12% 7% 2 7% 5% 3 5% 3 6% 8% 41%	2200
October	1st to 10th	Day	16% 6% 3 6% 4 4 4 3 4 6% 45%	2200
	11th to 20th	Day	24% 9% 2 9% 5% 4 4 3 5% 7% 28%	1951
	21st to end	Day	26% 12% 3 7% 5% 5% 5% 4 4 5% 25%	1980
November	1st to 10th	Day	15% 14% 3 6% 4 4 4 3 4 6% 36%	1852
	11th to 20th	Day	16% 24% 5% 9% 5% 4 4 3 3 5% 22%	1863
	21st to end	Day	23% 21% 6% 10% 5% 3 3 2 4 4 20%	1800
December	1st to 10th	Day	13% 27% 14% 13% 4 3 2 2 3 4 15%	2657
	11th to 20th	Day	16% 27% 13% 12% 6% 3 3 2 3 4 9%	3008
	21st to end	Day	25% 23% 9% 12% 4 3 3 2 3 4 11%	3982
January	1st to 10th	Night	13% 26% 12% 21% 5% 3 3 2 2 3 9%	6348
	11th to 20th	Night	13% 22% 12% 21% 9% 9% 3 1 2 2 6%	6360
	21st to end	Night	19% 19% 10% 16% 5% 6% 4 2 2 3 14%	6996
February	1st to 10th	Night	14% 18% 6% 17% 9% 4 3 2 4 4 19%	2526
	11th to 20th	Night	14% 18% 8% 15% 8% 4 3 3 4 4 19%	2338
	21st to end	Night	18% 16% 5% 12% 6% 4 2 3 4 5% 25%	1980
March	1st to 10th	Night	16% 11% 5% 10% 4 3 3 3 5% 5% 34%	5373
	11th to 20th	Night	11% 9% 3 7% 5% 4 4 3 4 6% 43%	5174
	21st to end	Night	19% 13% 6% 9% 4 3 4 3 4 5% 30%	5201
April	1st to 10th	Night	15% 12% 3 7% 4 5% 5% 4 5% 6% 35%	2000
	11th to 20th	Night	20% 10% 3 6% 4 3 4 4 4 6% 37%	1956
	21st to end	Night	17% 8% 3 7% 4 4 4 3 6% 8% 37%	1800
May	1st to 10th	Night	18% 9% 3 8% 5% 4 4 3 5% 7% 34%	4033
	11th to 20th	Night	16% 7% 3 6% 4 4 3 3 5% 7% 43%	3975
	21st to end	Night	18% 7% 3 6% 4 4 4 2 4 6% 42%	3942
June	1st to 10th	Night	10% 4 2 6% 4 4 4 4 7% 9% 47%	1600
	11th to 20th	Night	10% 6% 2 7% 5% 4 4 5% 6% 8% 43%	1600
	21st to end	Night	10% 5% 3 5% 5% 4 6% 4 6% 9% 43%	1600
July	1st to 10th	Night	11% 5% 2 6% 5% 4 5% 4 6% 9% 43%	3618
	11th to 20th	Night	9% 4 2 6% 4 4 4 3 5% 8% 51%	3617
	21st to end	Night	9% 6% 2 6% 4 5% 4 4 6% 9% 46%	3947
August	1st to 10th	Night	10% 4 2 6% 4 5% 4 4 6% 8% 47%	2842
	11th to 20th	Night	12% 4 2 5% 4 4 4 3 4 7% 50%	2926
	21st to end	Night	9% 6% 2 7% 5% 4 4 4 5% 7% 48%	3586
September	1st to 10th	Night	10% 6% 2 6% 4 3 4 3 5% 7% 50%	2000
	11th to 20th	Night	11% 4 2 4 3 4 4 3 5% 6% 53%	2187
	21st to end	Night	13% 8% 3 8% 4 4 4 4 5% 7% 42%	2200
October	1st to 10th	Night	17% 6% 2 6% 3 4 3 3 5% 5% 46%	2200
	11th to 20th	Night	22% 11% 4 6% 4 3 3 3 4 5% 35%	2444
	21st to end	Night	27% 12% 3 6% 4 3 4 2 4 5% 31%	2860
November	1st to 10th	Night	17% 14% 5% 7% 4 4 3 4 4 5% 34%	2666
	11th to 20th	Night	17% 23% 5% 9% 4 3 3 3 4 5% 24%	2692
	21st to end	Night	19% 23% 5% 9% 4 3 3 2 4 5% 23%	2600
December	1st to 10th	Night	15% 27% 11% 14% 5% 4 3 3 3 3 13%	4514
	11th to 20th	Night	18% 27% 11% 14% 6% 3 3 2 3 4 10%	5199
	21st to end	Night	25% 23% 7% 10% 5% 4 4 3 3 4 11%	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	81% 2 8% 9% 1	3618
	11th to 20th	Day	88% 2 6% 3 1	3620
	21st to end	Day	78% 2 9% 9% 2	3982
February	1st to 10th	Day	75% 3 8% 11% 4	1866
	11th to 20th	Day	69% 3 8% 14% 5% 1	1958
	21st to end	Day	64% 3 11% 15% 6% 1	1650
March	1st to 10th	Day	56% 2 13% 20% 8%	4480
	11th to 20th	Day	47% 3 15% 27% 8% 1	4786
	21st to end	Day	62% 3 9% 17% 8%	5774
April	1st to 10th	Day	55% 3 9% 21% 12%	2400
	11th to 20th	Day	47% 3 9% 25% 13% 3	2391
	21st to end	Day	48% 4 12% 21% 14% 2	2600
May	1st to 10th	Day	46% 4 10% 24% 15% 1	5897
	11th to 20th	Day	42% 4 13% 26% 15% 2	5909
	21st to end	Day	39% 3 10% 29% 19% 1	6949
June	1st to 10th	Day	35% 4 12% 28% 20% 2	2800
	11th to 20th	Day	33% 5% 13% 27% 20% 2	2800
	21st to end	Day	36% 4 15% 24% 18% 2	2800
July	1st to 10th	Day	38% 4 13% 27% 15% 2	6291
	11th to 20th	Day	31% 5% 14% 31% 18% 1	6285
	21st to end	Day	32% 5% 16% 25% 19% 2	6728
August	1st to 10th	Day	34% 4 14% 32% 15% 1	4292
	11th to 20th	Day	33% 5% 13% 34% 14% 1	4158
	21st to end	Day	32% 4 14% 29% 18% 2	4311
September	1st to 10th	Day	36% 4 12% 29% 15% 4	2392
	11th to 20th	Day	33% 3 12% 34% 17% 2	2200
	21st to end	Day	42% 4 9% 29% 16% 1	2200
October	1st to 10th	Day	31% 3 8% 40% 17% 1	3590
	11th to 20th	Day	44% 4 10% 25% 18%	3154
	21st to end	Day	53% 3 11% 22% 10% 1	3180
November	1st to 10th	Day	51% 4 12% 20% 12% 1	1852
	11th to 20th	Day	66% 2 9% 17% 5% 1	1863
	21st to end	Day	71% 3 10% 13% 4	1800
December	1st to 10th	Day	76% 4 11% 7% 2	2657
	11th to 20th	Day	81% 3 9% 6% 1	3005
	21st to end	Day	80% 2 6% 10% 2	3982
January	1st to 10th	Night	82% 2 6% 7% 2	6348
	11th to 20th	Night	88% 2 4 4 2	6360
	21st to end	Night	79% 1 10% 7% 2	6996
February	1st to 10th	Night	72% 3 8% 11% 6%	2526
	11th to 20th	Night	70% 3 6% 15% 6%	2339
	21st to end	Night	64% 2 11% 15% 7% 1	1980
March	1st to 10th	Night	53% 3 12% 24% 8% 1	5373
	11th to 20th	Night	44% 3 11% 30% 10% 2	5174
	21st to end	Night	59% 2 9% 19% 11% 1	5201
April	1st to 10th	Night	50% 4 11% 21% 13% 1	2000
	11th to 20th	Night	50% 3 8% 20% 17% 3	1956
	21st to end	Night	47% 4 11% 21% 15% 3	1800
May	1st to 10th	Night	52% 2 9% 19% 13% 4	4060
	11th to 20th	Night	44% 4 10% 23% 17% 3	3976
	21st to end	Night	45% 3 8% 22% 21% 2	3950
June	1st to 10th	Night	34% 4 10% 31% 17% 3	1600
	11th to 20th	Night	38% 5% 11% 25% 19% 2	1600
	21st to end	Night	37% 5% 15% 24% 16% 3	1600
July	1st to 10th	Night	37% 5% 12% 28% 14% 5%	3580
	11th to 20th	Night	32% 6% 12% 24% 22% 4	3572
	21st to end	Night	35% 6% 13% 21% 23% 1	3832
August	1st to 10th	Night	34% 5% 13% 29% 18% 1	2833
	11th to 20th	Night	34% 5% 9% 32% 18% 1	2953
	21st to end	Night	36% 4 9% 28% 20% 2	3586
September	1st to 10th	Night	34% 4 11% 30% 18% 4	2000
	11th to 20th	Night	32% 3 8% 33% 22% 2	2187
	21st to end	Night	43% 4 10% 26% 17% 1	2200
October	1st to 10th	Night	30% 3 8% 34% 23% 2	3590
	11th to 20th	Night	43% 3 10% 23% 20% 1	3980
	21st to end	Night	47% 3 8% 26% 16% 1	4610
November	1st to 10th	Night	53% 3 8% 21% 13% 1	2666
	11th to 20th	Night	64% 2 10% 16% 6% 1	2692
	21st to end	Night	67% 2 12% 16% 3	2600
December	1st to 10th	Night	78% 3 10% 7% 2	4514
	11th to 20th	Night	81% 3 8% 6% 1	5201
	21st to end	Night	79% 3 9% 8% 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	22% 26% 33% 15% 3 1	300
	11th to 20th	Day	24% 21% 39% 12% 3	300
	21st to end	Day	32% 23% 31% 13% 1	330
February	1st to 10th	Day	29% 27% 27% 13% 3 1	300
	11th to 20th	Day	28% 33% 29% 9% 1	300
	21st to end	Day	32% 33% 27% 8% 1	249
March	1st to 10th	Day	24% 32% 32% 10% 2	300
	11th to 20th	Day	26% 23% 30% 16% 4 1	410
	21st to end	Day	33% 21% 27% 14% 4 1	550
April	1st to 10th	Day	28% 23% 30% 13% 5%	500
	11th to 20th	Day	27% 26% 27% 13% 5% 2	492
	21st to end	Day	26% 21% 31% 15% 7% 1	500
May	1st to 10th	Day	24% 18% 32% 18% 6% 2	503
	11th to 20th	Day	20% 15% 32% 20% 8% 5%	545
	21st to end	Day	15% 14% 35% 21% 11% 4	789
June	1st to 10th	Day	12% 13% 38% 24% 11% 3	730
	11th to 20th	Day	13% 12% 33% 29% 10% 3	730
	21st to end	Day	14% 11% 37% 25% 11% 2	730
July	1st to 10th	Day	9% 8% 29% 31% 16% 6%	721
	11th to 20th	Day	10% 9% 31% 31% 12% 6%	718
	21st to end	Day	7% 7% 33% 33% 15% 5%	794
August	1st to 10th	Day	9% 6% 24% 30% 21% 10%	574
	11th to 20th	Day	11% 7% 25% 29% 21% 7%	519
	21st to end	Day	11% 8% 24% 31% 19% 6%	583
September	1st to 10th	Day	15% 9% 24% 29% 17% 7%	530
	11th to 20th	Day	10% 6% 22% 27% 27% 9%	530
	21st to end	Day	18% 14% 22% 24% 16% 6%	530
October	1st to 10th	Day	19% 11% 28% 24% 15% 2	530
	11th to 20th	Day	28% 19% 30% 19% 4	396
	21st to end	Day	36% 18% 31% 11% 3	363
November	1st to 10th	Day	28% 21% 29% 15% 5% 1	330
	11th to 20th	Day	31% 26% 28% 12% 3	321
	21st to end	Day	35% 24% 31% 9%	300
December	1st to 10th	Day	31% 29% 23% 13% 3	300
	11th to 20th	Day	27% 31% 28% 11% 2 1	300
	21st to end	Day	30% 28% 31% 8% 2 1	330
January	1st to 10th	Night	27% 23% 29% 17% 4	1000
	11th to 20th	Night	29% 20% 31% 16% 4 1	1000
	21st to end	Night	26% 19% 32% 20% 3	1100
February	1st to 10th	Night	24% 20% 33% 19% 3	851
	11th to 20th	Night	25% 21% 31% 18% 4	783
	21st to end	Night	28% 21% 33% 15% 2	660
March	1st to 10th	Night	23% 19% 28% 23% 6% 1	800
	11th to 20th	Night	21% 17% 34% 22% 5% 1	800
	21st to end	Night	25% 14% 29% 25% 6% 1	769
April	1st to 10th	Night	21% 17% 32% 23% 6% 1	600
	11th to 20th	Night	27% 15% 28% 23% 7% 1	593
	21st to end	Night	21% 14% 30% 28% 7% 2	600
May	1st to 10th	Night	19% 12% 32% 28% 8% 1	600
	11th to 20th	Night	19% 11% 26% 31% 13%	591
	21st to end	Night	15% 6% 27% 33% 18% 2	650
June	1st to 10th	Night	12% 7% 25% 39% 17% 1	600
	11th to 20th	Night	12% 5% 30% 35% 17% 1	600
	21st to end	Night	11% 6% 25% 36% 20% 2	600
July	1st to 10th	Night	9% 3 20% 37% 28% 3	585
	11th to 20th	Night	9% 5% 21% 34% 27% 4	582
	21st to end	Night	8% 4 18% 42% 26% 2	657
August	1st to 10th	Night	8% 4 15% 44% 25% 4	597
	11th to 20th	Night	11% 4 14% 40% 26% 5%	594
	21st to end	Night	10% 6% 18% 36% 28% 3	660
September	1st to 10th	Night	12% 7% 18% 35% 23% 5%	600
	11th to 20th	Night	13% 6% 17% 33% 28% 4	787
	21st to end	Night	18% 10% 22% 27% 19% 5%	800
October	1st to 10th	Night	19% 9% 23% 30% 17% 2	800
	11th to 20th	Night	28% 15% 26% 24% 7% 1	800
	21st to end	Night	34% 15% 26% 20% 5%	880
November	1st to 10th	Night	25% 16% 31% 19% 8%	820
	11th to 20th	Night	32% 21% 27% 16% 3 1	829
	21st to end	Night	33% 16% 31% 17% 3	800
December	1st to 10th	Night	32% 21% 29% 15% 3	960
	11th to 20th	Night	31% 20% 31% 14% 3 1	1000
	21st to end	Night	36% 20% 29% 14% 2	1100

Page generated at 2025-11-15 00:55:55. Version ac07

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