Voorhees State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Voorhees State Park clear sky chart from 2005-11-06 to 2025-09-04.

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	17% 7% 2 6% 4 4 4 4 6% 7% 39%	126242
	Night	17% 7% 2 6% 4 4 4 3 5% 7% 42%	122465
Transparency	Day	43% 5% 12% 22% 16% 3	129756
	Night	42% 4 12% 23% 16% 3	127038
Seeing	Day	23% 16% 30% 20% 9% 2	16012
	Night	21% 14% 31% 25% 8% 1	25183

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	13% 7% 2 6% 4 4 4 3 5% 6% 45%	3597
	11th to 20th	Day	14% 8% 3 10% 5% 5% 4 3 4 5% 38%	3570
	21st to end	Day	18% 7% 3 7% 5% 4 4 3 4 5% 40%	4447
February	1st to 10th	Day	17% 8% 3 7% 5% 4 5% 3 6% 6% 38%	1800
	11th to 20th	Day	16% 8% 3 8% 4 4 4 3 5% 6% 39%	1908
	21st to end	Day	20% 10% 2 6% 5% 4 4 3 5% 5% 37%	1650
March	1st to 10th	Day	21% 7% 2 5% 4 4 4 3 4 5% 42%	4476
	11th to 20th	Day	12% 6% 3 6% 5% 4 5% 4 6% 7% 42%	4924
	21st to end	Day	19% 6% 2 5% 3 4 4 3 5% 7% 42%	5830
April	1st to 10th	Day	19% 8% 3 6% 5% 5% 4 4 5% 6% 37%	2400
	11th to 20th	Day	17% 7% 2 6% 5% 4 4 4 6% 7% 39%	2374
	21st to end	Day	16% 7% 2 6% 5% 4 5% 4 5% 7% 40%	2400
May	1st to 10th	Day	27% 7% 2 6% 4 4 4 4 6% 7% 28%	5917
	11th to 20th	Day	24% 9% 3 6% 4 3 4 3 5% 6% 33%	6318
	21st to end	Day	20% 6% 2 6% 4 4 5% 4 6% 9% 35%	6949
June	1st to 10th	Day	15% 6% 2 6% 4 5% 6% 5% 6% 9% 37%	2800
	11th to 20th	Day	15% 6% 2 7% 5% 5% 5% 4 6% 8% 36%	2800
	21st to end	Day	13% 6% 2 6% 4 5% 5% 3 6% 7% 42%	2800
July	1st to 10th	Day	9% 6% 3 8% 5% 5% 5% 4 6% 10% 38%	6360
	11th to 20th	Day	12% 7% 2 6% 5% 6% 6% 6% 8% 11% 32%	6360
	21st to end	Day	12% 7% 2 6% 4 5% 5% 4 6% 9% 39%	6926
August	1st to 10th	Day	21% 6% 2 6% 4 4 5% 4 7% 8% 32%	4248
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 6% 8% 42%	3850
	21st to end	Day	13% 5% 2 5% 4 3 4 3 5% 8% 48%	4312
September	1st to 10th	Day	15% 5% 2 6% 4 4 4 3 6% 7% 44%	2316
	11th to 20th	Day	13% 5% 2 5% 3 3 4 3 5% 8% 50%	2235
	21st to end	Day	20% 6% 3 6% 4 4 5% 3 4 6% 40%	2090
October	1st to 10th	Day	19% 6% 2 6% 4 4 4 4 5% 6% 40%	1924
	11th to 20th	Day	16% 5% 2 5% 4 4 4 3 4 6% 46%	1900
	21st to end	Day	19% 7% 2 4 4 3 4 3 6% 6% 42%	1989
November	1st to 10th	Day	14% 6% 2 5% 3 2 3 3 4 5% 53%	1761
	11th to 20th	Day	17% 5% 2 4 4 3 4 4 5% 6% 46%	1800
	21st to end	Day	16% 7% 2 5% 4 5% 4 4 5% 6% 43%	1665
December	1st to 10th	Day	17% 7% 2 6% 4 3 4 4 5% 7% 42%	2600
	11th to 20th	Day	23% 7% 2 4 3 4 3 2 5% 5% 40%	2986
	21st to end	Day	18% 7% 3 7% 5% 5% 4 4 5% 8% 34%	3960
January	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 6% 7% 47%	6349
	11th to 20th	Night	13% 8% 2 7% 4 3 4 3 5% 7% 43%	6315
	21st to end	Night	18% 8% 2 5% 4 4 4 3 5% 6% 41%	6494
February	1st to 10th	Night	16% 9% 3 6% 4 4 4 3 5% 6% 40%	2600
	11th to 20th	Night	17% 8% 3 6% 5% 4 4 3 5% 5% 40%	2377
	21st to end	Night	18% 8% 2 5% 4 4 3 3 5% 6% 41%	1980
March	1st to 10th	Night	19% 8% 2 5% 3 3 4 3 5% 5% 42%	5364
	11th to 20th	Night	13% 7% 3 5% 4 4 3 3 4 6% 49%	5033
	21st to end	Night	16% 8% 3 7% 4 4 4 3 4 5% 42%	5100
April	1st to 10th	Night	18% 7% 3 7% 5% 5% 4 4 6% 6% 36%	2000
	11th to 20th	Night	17% 7% 2 6% 5% 5% 4 3 5% 7% 39%	1975
	21st to end	Night	20% 6% 2 5% 3 3 4 3 5% 7% 44%	2000
May	1st to 10th	Night	28% 8% 3 6% 4 4 4 3 6% 7% 28%	4050
	11th to 20th	Night	24% 9% 3 6% 4 4 4 3 5% 6% 33%	3575
	21st to end	Night	22% 7% 2 6% 4 4 4 3 5% 8% 36%	3926
June	1st to 10th	Night	16% 5% 2 6% 4 4 5% 3 6% 7% 42%	1600
	11th to 20th	Night	15% 5% 2 6% 4 4 5% 4 7% 8% 40%	1600
	21st to end	Night	11% 5% 2 5% 4 4 5% 4 6% 11% 43%	1600
July	1st to 10th	Night	11% 7% 3 7% 6% 5% 5% 4 7% 9% 38%	3600
	11th to 20th	Night	16% 8% 3 6% 5% 4 6% 5% 7% 9% 32%	3600
	21st to end	Night	13% 6% 2 5% 4 4 4 4 6% 8% 44%	3926
August	1st to 10th	Night	22% 7% 2 6% 4 4 4 4 6% 8% 32%	2897
	11th to 20th	Night	14% 6% 2 6% 5% 5% 5% 4 5% 7% 40%	3164
	21st to end	Night	12% 4 2 5% 4 3 4 3 6% 8% 50%	3586
September	1st to 10th	Night	16% 6% 2 5% 5% 4 4 3 4 6% 45%	1931
	11th to 20th	Night	13% 4 2 5% 4 3 3 2 5% 7% 51%	1943
	21st to end	Night	19% 6% 2 6% 4 4 3 3 5% 6% 43%	2090
October	1st to 10th	Night	19% 6% 3 6% 3 3 3 3 4 7% 43%	2251
	11th to 20th	Night	16% 5% 2 5% 3 3 4 3 4 6% 49%	2280
	21st to end	Night	20% 6% 2 5% 3 3 3 3 4 5% 45%	2608
November	1st to 10th	Night	13% 6% 2 4 3 2 3 3 5% 6% 52%	2537
	11th to 20th	Night	18% 8% 2 4 3 3 3 3 3 5% 48%	2600
	21st to end	Night	15% 6% 2 6% 4 3 5% 4 5% 7% 43%	2730
December	1st to 10th	Night	14% 7% 3 7% 4 4 4 3 4 6% 45%	4580
	11th to 20th	Night	24% 7% 2 4 3 3 4 3 4 5% 41%	5208
	21st to end	Night	20% 10% 3 6% 4 3 3 3 4 5% 39%	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	39% 3 9% 28% 19% 2	3598
	11th to 20th	Day	46% 4 9% 21% 15% 5%	3600
	21st to end	Day	47% 4 10% 22% 15% 1	4447
February	1st to 10th	Day	45% 5% 15% 22% 12% 1	1800
	11th to 20th	Day	46% 5% 9% 23% 15% 3	1917
	21st to end	Day	49% 3 12% 22% 11% 3	1650
March	1st to 10th	Day	44% 3 9% 23% 14% 7%	4479
	11th to 20th	Day	40% 5% 13% 27% 11% 5%	4924
	21st to end	Day	42% 4 11% 14% 24% 5%	5830
April	1st to 10th	Day	47% 5% 9% 20% 14% 5%	2400
	11th to 20th	Day	42% 6% 12% 20% 17% 3	2374
	21st to end	Day	43% 6% 10% 20% 17% 4	2400
May	1st to 10th	Day	54% 4 14% 16% 10% 1	5928
	11th to 20th	Day	52% 5% 9% 21% 12% 1	6322
	21st to end	Day	45% 6% 11% 23% 14% 2	6949
June	1st to 10th	Day	42% 7% 14% 21% 14% 1	2800
	11th to 20th	Day	45% 8% 13% 22% 11% 2	2800
	21st to end	Day	41% 7% 13% 23% 15% 1	2800
July	1st to 10th	Day	42% 7% 13% 21% 15% 1	6290
	11th to 20th	Day	44% 5% 19% 22% 10% 1	6285
	21st to end	Day	41% 5% 11% 21% 21% 1	6728
August	1st to 10th	Day	49% 6% 13% 22% 10% 1	4234
	11th to 20th	Day	38% 6% 14% 29% 13% 1	3886
	21st to end	Day	35% 5% 9% 29% 19% 2	4312
September	1st to 10th	Day	40% 6% 11% 22% 19% 3	2316
	11th to 20th	Day	33% 4 11% 24% 24% 4	2235
	21st to end	Day	46% 6% 9% 18% 20% 2	2090
October	1st to 10th	Day	39% 4 9% 19% 24% 5%	3197
	11th to 20th	Day	28% 4 10% 26% 27% 5%	3140
	21st to end	Day	27% 3 15% 24% 27% 4	3253
November	1st to 10th	Day	35% 3 13% 24% 22% 3	1761
	11th to 20th	Day	38% 5% 11% 24% 20% 3	1800
	21st to end	Day	40% 4 14% 29% 11% 2	1665
December	1st to 10th	Day	42% 3 15% 26% 12% 2	2600
	11th to 20th	Day	45% 4 13% 24% 12% 1	2986
	21st to end	Day	46% 5% 10% 21% 15% 1	3960
January	1st to 10th	Night	36% 3 10% 26% 21% 4	6349
	11th to 20th	Night	41% 4 14% 21% 14% 6%	6360
	21st to end	Night	45% 3 11% 20% 17% 4	6494
February	1st to 10th	Night	45% 4 13% 25% 11% 2	2600
	11th to 20th	Night	45% 5% 10% 20% 17% 4	2379
	21st to end	Night	43% 4 8% 24% 17% 3	1980
March	1st to 10th	Night	43% 4 10% 22% 12% 9%	5374
	11th to 20th	Night	39% 3 15% 24% 14% 4	5034
	21st to end	Night	45% 4 6% 17% 23% 5%	5100
April	1st to 10th	Night	46% 6% 10% 20% 14% 4	2000
	11th to 20th	Night	44% 5% 9% 20% 19% 2	1975
	21st to end	Night	40% 4 11% 22% 19% 5%	2000
May	1st to 10th	Night	55% 4 12% 16% 10% 2	4056
	11th to 20th	Night	52% 6% 13% 15% 13% 2	3576
	21st to end	Night	46% 6% 12% 24% 11% 2	3927
June	1st to 10th	Night	40% 7% 11% 22% 19% 1	1600
	11th to 20th	Night	38% 9% 15% 24% 13% 1	1600
	21st to end	Night	35% 8% 16% 25% 15% 1	1600
July	1st to 10th	Night	42% 7% 15% 19% 15% 2	3560
	11th to 20th	Night	48% 6% 15% 21% 10% 1	3552
	21st to end	Night	38% 5% 13% 24% 20% 1	3809
August	1st to 10th	Night	50% 6% 17% 17% 9% 1	2887
	11th to 20th	Night	43% 5% 13% 26% 13% 1	3194
	21st to end	Night	33% 5% 9% 31% 20% 1	3586
September	1st to 10th	Night	41% 6% 10% 22% 19% 2	1931
	11th to 20th	Night	34% 4 11% 23% 25% 4	1943
	21st to end	Night	42% 4 9% 23% 21% 1	2090
October	1st to 10th	Night	42% 4 10% 23% 20% 2	3758
	11th to 20th	Night	26% 3 10% 29% 27% 4	3779
	21st to end	Night	30% 3 12% 32% 21% 3	4294
November	1st to 10th	Night	33% 5% 12% 24% 22% 4	2537
	11th to 20th	Night	40% 4 9% 24% 19% 4	2600
	21st to end	Night	38% 5% 14% 27% 14% 1	2730
December	1st to 10th	Night	40% 3 13% 31% 11% 2	4580
	11th to 20th	Night	45% 4 11% 23% 15% 3	5208
	21st to end	Night	48% 4 10% 20% 16% 3	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	32% 26% 31% 10% 2 1	200
	11th to 20th	Day	36% 26% 30% 8% 1	200
	21st to end	Day	27% 27% 33% 9% 4	327
February	1st to 10th	Day	29% 28% 33% 7% 2	300
	11th to 20th	Day	35% 24% 32% 8% 1	456
	21st to end	Day	33% 25% 26% 14% 2	414
March	1st to 10th	Day	33% 22% 29% 13% 3	500
	11th to 20th	Day	28% 25% 30% 13% 3 1	500
	21st to end	Day	31% 23% 31% 10% 4 1	550
April	1st to 10th	Day	30% 23% 30% 12% 5%	500
	11th to 20th	Day	27% 24% 29% 12% 7% 1	492
	21st to end	Day	27% 20% 34% 15% 3 2	500
May	1st to 10th	Day	34% 18% 30% 11% 7% 1	503
	11th to 20th	Day	24% 16% 34% 19% 6% 1	527
	21st to end	Day	22% 10% 29% 25% 11% 2	573
June	1st to 10th	Day	18% 15% 30% 24% 12% 2	530
	11th to 20th	Day	19% 13% 29% 26% 11% 1	530
	21st to end	Day	18% 12% 32% 25% 11% 2	530
July	1st to 10th	Day	13% 6% 30% 30% 18% 4	525
	11th to 20th	Day	11% 5% 26% 36% 18% 3	524
	21st to end	Day	15% 7% 31% 31% 12% 3	576
August	1st to 10th	Day	14% 6% 29% 31% 16% 4	526
	11th to 20th	Day	14% 5% 28% 30% 18% 5%	519
	21st to end	Day	13% 8% 31% 27% 14% 7%	583
September	1st to 10th	Day	20% 11% 23% 27% 14% 6%	502
	11th to 20th	Day	14% 7% 29% 26% 15% 10%	490
	21st to end	Day	24% 12% 29% 20% 11% 4	490
October	1st to 10th	Day	25% 11% 26% 21% 12% 5%	490
	11th to 20th	Day	18% 17% 32% 22% 9% 2	490
	21st to end	Day	25% 16% 32% 17% 10% 1	485
November	1st to 10th	Day	21% 15% 30% 22% 10% 2	395
	11th to 20th	Day	27% 19% 32% 19% 4	400
	21st to end	Day	26% 20% 35% 15% 4	265
December	1st to 10th	Day	33% 25% 29% 10% 5%	200
	11th to 20th	Day	39% 24% 25% 9% 5%	200
	21st to end	Day	31% 18% 30% 13% 6% 1	220
January	1st to 10th	Night	22% 24% 38% 14% 2	800
	11th to 20th	Night	28% 20% 32% 19% 3	800
	21st to end	Night	21% 22% 38% 17% 1	880
February	1st to 10th	Night	25% 19% 36% 19% 2	800
	11th to 20th	Night	27% 23% 37% 13% 1	783
	21st to end	Night	28% 20% 34% 16% 2	660
March	1st to 10th	Night	25% 23% 31% 18% 3	800
	11th to 20th	Night	25% 21% 33% 17% 4	800
	21st to end	Night	21% 22% 38% 15% 4	880
April	1st to 10th	Night	23% 21% 36% 16% 3	800
	11th to 20th	Night	23% 17% 36% 18% 5%	791
	21st to end	Night	22% 17% 33% 24% 5%	800
May	1st to 10th	Night	28% 15% 29% 22% 6%	609
	11th to 20th	Night	22% 11% 36% 24% 7%	394
	21st to end	Night	19% 6% 27% 35% 11% 1	433
June	1st to 10th	Night	18% 8% 30% 33% 11% 1	400
	11th to 20th	Night	15% 8% 32% 35% 10%	400
	21st to end	Night	12% 4 28% 44% 12% 1	400
July	1st to 10th	Night	13% 4 24% 39% 17% 2	390
	11th to 20th	Night	13% 4 23% 42% 17% 1	388
	21st to end	Night	12% 3 29% 40% 16% 1	438
August	1st to 10th	Night	15% 1 19% 44% 19% 2	579
	11th to 20th	Night	14% 3 22% 35% 24% 2	769
	21st to end	Night	15% 5% 21% 38% 20% 1	880
September	1st to 10th	Night	17% 6% 27% 33% 17% 2	773
	11th to 20th	Night	17% 4 22% 33% 20% 4	760
	21st to end	Night	24% 6% 24% 32% 14% 1	760
October	1st to 10th	Night	23% 9% 25% 27% 14% 2	760
	11th to 20th	Night	18% 12% 30% 30% 10%	760
	21st to end	Night	23% 15% 30% 24% 8%	836
November	1st to 10th	Night	17% 13% 33% 26% 9% 1	780
	11th to 20th	Night	24% 17% 31% 22% 6% 1	800
	21st to end	Night	20% 20% 35% 21% 5% 1	800
December	1st to 10th	Night	26% 18% 32% 19% 4	800
	11th to 20th	Night	24% 18% 35% 20% 3	800
	21st to end	Night	25% 19% 31% 23% 2	880

Page generated at 2025-09-01 01:51:03. Version ac07

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