Island Beach State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Island Beach State Park clear sky chart from 2005-11-06 to 2026-02-01.

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	15% 7% 2 6% 4 4 4 4 5% 8% 41%	127475
	Night	16% 8% 3 6% 4 4 4 3 5% 7% 42%	124559
Transparency	Day	41% 6% 12% 23% 16% 3	131015
	Night	41% 5% 11% 23% 17% 3	129093
Seeing	Day	17% 6% 23% 31% 18% 4	16622
	Night	18% 8% 28% 30% 14% 2	25923

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 4 2 3 3 3 5% 6% 53%	3677
	11th to 20th	Day	13% 7% 3 7% 4 3 4 3 5% 5% 47%	3650
	21st to end	Day	18% 10% 3 7% 4 3 3 3 4 6% 39%	4514
February	1st to 10th	Day	15% 9% 3 7% 5% 4 3 3 6% 7% 39%	1840
	11th to 20th	Day	18% 7% 2 6% 3 4 4 4 5% 6% 41%	1948
	21st to end	Day	17% 9% 2 8% 4 4 3 4 4 6% 40%	1650
March	1st to 10th	Day	19% 6% 2 4 3 3 3 2 5% 5% 48%	4476
	11th to 20th	Day	12% 12% 2 5% 4 4 4 3 5% 7% 44%	4789
	21st to end	Day	16% 7% 2 5% 4 4 4 3 5% 6% 44%	5919
April	1st to 10th	Day	18% 8% 2 5% 5% 4 4 3 5% 7% 40%	2400
	11th to 20th	Day	15% 7% 3 5% 3 3 4 4 5% 7% 43%	2374
	21st to end	Day	17% 6% 2 5% 4 5% 5% 4 6% 7% 39%	2400
May	1st to 10th	Day	21% 11% 4 8% 5% 4 4 4 5% 7% 28%	5876
	11th to 20th	Day	24% 9% 3 6% 4 3 3 3 4 6% 35%	6170
	21st to end	Day	19% 8% 3 7% 4 4 4 3 5% 9% 35%	6949
June	1st to 10th	Day	13% 6% 3 6% 5% 4 5% 5% 6% 9% 38%	2800
	11th to 20th	Day	12% 6% 2 5% 4 5% 4 5% 6% 10% 40%	2800
	21st to end	Day	8% 6% 2 6% 5% 5% 5% 4 8% 10% 43%	2800
July	1st to 10th	Day	8% 7% 3 7% 5% 5% 6% 5% 6% 10% 39%	6360
	11th to 20th	Day	10% 7% 3 7% 6% 6% 7% 6% 8% 10% 30%	6360
	21st to end	Day	10% 7% 2 7% 4 5% 5% 4 7% 8% 41%	6926
August	1st to 10th	Day	14% 6% 2 7% 5% 4 5% 4 7% 10% 35%	4170
	11th to 20th	Day	13% 6% 2 6% 5% 4 4 4 6% 8% 42%	3850
	21st to end	Day	8% 5% 2 5% 4 4 4 4 7% 10% 49%	4312
September	1st to 10th	Day	14% 6% 2 5% 3 3 3 3 5% 9% 48%	2400
	11th to 20th	Day	10% 5% 2 6% 4 3 4 3 5% 8% 51%	2310
	21st to end	Day	18% 7% 4 7% 4 4 5% 3 4 6% 38%	2200
October	1st to 10th	Day	19% 6% 2 5% 3 3 3 3 5% 7% 45%	2097
	11th to 20th	Day	16% 5% 2 5% 3 2 3 3 4 6% 51%	2000
	21st to end	Day	17% 6% 2 5% 3 3 4 3 5% 7% 45%	2065
November	1st to 10th	Day	13% 6% 2 5% 3 3 4 3 4 7% 50%	1851
	11th to 20th	Day	15% 6% 2 6% 4 4 3 3 4 6% 46%	1890
	21st to end	Day	15% 5% 2 5% 5% 4 4 4 5% 8% 44%	1858
December	1st to 10th	Day	13% 6% 1 5% 3 4 4 3 5% 7% 48%	2680
	11th to 20th	Day	18% 10% 2 5% 3 2 2 2 3 5% 47%	3066
	21st to end	Day	14% 8% 3 6% 3 4 4 4 6% 8% 40%	4048
January	1st to 10th	Night	13% 6% 2 4 3 3 3 3 4 6% 52%	6489
	11th to 20th	Night	16% 8% 2 5% 3 3 3 3 4 4 49%	6455
	21st to end	Night	17% 8% 3 7% 4 3 4 3 4 6% 41%	6680
February	1st to 10th	Night	18% 8% 3 6% 3 4 4 3 5% 5% 41%	2560
	11th to 20th	Night	19% 9% 3 5% 4 3 3 3 5% 6% 41%	2338
	21st to end	Night	18% 8% 2 6% 4 3 3 3 5% 6% 43%	1980
March	1st to 10th	Night	17% 9% 3 5% 3 2 3 2 3 6% 46%	5364
	11th to 20th	Night	12% 14% 3 5% 3 4 3 2 4 5% 45%	5168
	21st to end	Night	17% 8% 3 7% 4 3 3 3 5% 5% 41%	5012
April	1st to 10th	Night	18% 9% 3 7% 4 4 3 3 4 6% 40%	2000
	11th to 20th	Night	16% 8% 3 5% 4 4 3 3 5% 5% 43%	1975
	21st to end	Night	17% 6% 3 5% 3 4 4 4 5% 8% 41%	2000
May	1st to 10th	Night	20% 11% 4 7% 4 4 5% 4 5% 9% 27%	4063
	11th to 20th	Night	23% 10% 4 6% 3 3 3 3 5% 6% 33%	3766
	21st to end	Night	22% 8% 3 6% 4 4 4 3 5% 8% 34%	3926
June	1st to 10th	Night	16% 8% 3 6% 4 5% 5% 4 4 8% 37%	1600
	11th to 20th	Night	14% 6% 3 6% 4 4 4 4 7% 8% 41%	1600
	21st to end	Night	9% 6% 2 6% 4 5% 5% 5% 7% 11% 41%	1600
July	1st to 10th	Night	9% 10% 3 8% 5% 5% 6% 4 6% 8% 35%	3600
	11th to 20th	Night	11% 9% 3 8% 6% 6% 6% 4 7% 10% 31%	3600
	21st to end	Night	11% 7% 3 7% 5% 4 4 4 7% 9% 39%	3926
August	1st to 10th	Night	19% 9% 3 7% 5% 4 5% 3 5% 9% 31%	2942
	11th to 20th	Night	10% 6% 3 7% 5% 4 4 4 6% 7% 44%	3197
	21st to end	Night	8% 5% 2 5% 4 4 5% 4 6% 8% 52%	3586
September	1st to 10th	Night	14% 6% 2 6% 4 4 5% 3 5% 7% 45%	2000
	11th to 20th	Night	13% 6% 2 5% 3 3 3 3 5% 7% 50%	2088
	21st to end	Night	20% 8% 3 5% 3 4 4 3 5% 7% 38%	2200
October	1st to 10th	Night	19% 7% 2 5% 4 3 4 3 5% 5% 44%	2299
	11th to 20th	Night	17% 5% 2 4 3 3 4 3 4 7% 50%	2400
	21st to end	Night	18% 7% 2 5% 4 3 3 2 4 6% 45%	2774
November	1st to 10th	Night	12% 6% 2 4 4 3 4 3 4 6% 52%	2667
	11th to 20th	Night	16% 7% 3 6% 3 3 3 3 5% 5% 48%	2730
	21st to end	Night	13% 5% 2 4 5% 5% 4 3 5% 6% 46%	2756
December	1st to 10th	Night	13% 7% 2 5% 3 3 4 3 5% 8% 48%	4720
	11th to 20th	Night	21% 7% 2 5% 3 3 3 3 4 6% 42%	5348
	21st to end	Night	15% 9% 3 6% 4 4 4 3 6% 6% 40%	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	33% 4 7% 29% 25% 2	3678
	11th to 20th	Day	40% 4 8% 24% 18% 6%	3680
	21st to end	Day	46% 5% 9% 26% 11% 3	4514
February	1st to 10th	Day	44% 5% 13% 24% 13% 1	1840
	11th to 20th	Day	43% 5% 8% 24% 16% 3	1957
	21st to end	Day	45% 5% 9% 23% 14% 4	1650
March	1st to 10th	Day	39% 3 9% 24% 17% 8%	4479
	11th to 20th	Day	39% 5% 9% 27% 16% 4	4789
	21st to end	Day	41% 5% 10% 16% 22% 6%	5919
April	1st to 10th	Day	44% 5% 10% 19% 16% 5%	2400
	11th to 20th	Day	39% 6% 14% 23% 16% 3	2374
	21st to end	Day	42% 6% 10% 19% 19% 4	2400
May	1st to 10th	Day	54% 8% 13% 16% 8% 1	5887
	11th to 20th	Day	50% 6% 9% 23% 11% 1	6174
	21st to end	Day	45% 8% 10% 21% 15% 1	6949
June	1st to 10th	Day	41% 9% 13% 21% 15% 1	2800
	11th to 20th	Day	37% 9% 14% 26% 12% 2	2800
	21st to end	Day	34% 10% 16% 22% 17% 1	2800
July	1st to 10th	Day	41% 11% 15% 20% 13% 1	6290
	11th to 20th	Day	47% 8% 20% 18% 7% 1	6285
	21st to end	Day	38% 7% 12% 22% 19% 1	6728
August	1st to 10th	Day	45% 7% 19% 21% 9%	4156
	11th to 20th	Day	39% 7% 14% 29% 10% 1	3886
	21st to end	Day	30% 7% 15% 29% 18% 2	4312
September	1st to 10th	Day	35% 6% 14% 23% 20% 2	2400
	11th to 20th	Day	32% 7% 12% 25% 22% 3	2310
	21st to end	Day	47% 6% 9% 18% 18% 2	2200
October	1st to 10th	Day	34% 4 12% 23% 23% 4	3409
	11th to 20th	Day	26% 3 9% 24% 32% 6%	3240
	21st to end	Day	28% 4 15% 26% 24% 4	3316
November	1st to 10th	Day	36% 4 12% 26% 19% 3	1851
	11th to 20th	Day	39% 5% 9% 22% 22% 3	1890
	21st to end	Day	39% 5% 12% 30% 12% 2	1858
December	1st to 10th	Day	37% 4 16% 26% 15% 2	2680
	11th to 20th	Day	43% 3 9% 29% 13% 3	3066
	21st to end	Day	41% 6% 12% 23% 17% 2	4048
January	1st to 10th	Night	35% 3 8% 26% 22% 6%	6489
	11th to 20th	Night	40% 3 9% 24% 17% 7%	6500
	21st to end	Night	44% 4 9% 22% 19% 3	6680
February	1st to 10th	Night	44% 4 13% 23% 13% 2	2560
	11th to 20th	Night	44% 4 8% 21% 18% 5%	2340
	21st to end	Night	43% 4 8% 22% 18% 5%	1980
March	1st to 10th	Night	43% 3 8% 23% 14% 10%	5374
	11th to 20th	Night	42% 4 11% 25% 13% 5%	5169
	21st to end	Night	45% 5% 6% 16% 24% 4	5012
April	1st to 10th	Night	46% 5% 9% 18% 18% 5%	2000
	11th to 20th	Night	43% 4 10% 20% 20% 4	1975
	21st to end	Night	40% 6% 8% 20% 20% 5%	2000
May	1st to 10th	Night	53% 6% 12% 18% 8% 3	4069
	11th to 20th	Night	53% 4 10% 18% 14% 1	3767
	21st to end	Night	47% 7% 11% 20% 14% 1	3927
June	1st to 10th	Night	45% 8% 8% 20% 19% 1	1600
	11th to 20th	Night	40% 8% 12% 25% 13% 2	1600
	21st to end	Night	36% 8% 16% 24% 15% 2	1600
July	1st to 10th	Night	46% 8% 12% 21% 12% 1	3560
	11th to 20th	Night	48% 6% 16% 22% 7% 1	3552
	21st to end	Night	40% 6% 14% 21% 18% 1	3809
August	1st to 10th	Night	50% 6% 18% 16% 9% 1	2932
	11th to 20th	Night	38% 5% 13% 32% 11% 1	3227
	21st to end	Night	31% 6% 11% 30% 20% 2	3586
September	1st to 10th	Night	40% 6% 12% 21% 19% 3	2000
	11th to 20th	Night	33% 5% 12% 24% 23% 3	2088
	21st to end	Night	46% 6% 7% 21% 18% 2	2200
October	1st to 10th	Night	38% 5% 10% 22% 23% 3	3754
	11th to 20th	Night	25% 3 10% 27% 29% 5%	3899
	21st to end	Night	28% 3 10% 30% 24% 4	4473
November	1st to 10th	Night	34% 5% 11% 25% 21% 4	2667
	11th to 20th	Night	39% 5% 8% 22% 21% 4	2730
	21st to end	Night	38% 5% 12% 26% 18% 2	2756
December	1st to 10th	Night	37% 3 12% 29% 15% 3	4720
	11th to 20th	Night	44% 4 9% 24% 15% 4	5348
	21st to end	Night	43% 5% 12% 21% 16% 3	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	14% 11% 46% 22% 6%	220
	11th to 20th	Day	17% 18% 37% 24% 3	220
	21st to end	Day	20% 10% 38% 25% 5% 1	350
February	1st to 10th	Day	21% 10% 38% 26% 5%	340
	11th to 20th	Day	24% 13% 38% 23% 2	496
	21st to end	Day	21% 12% 36% 25% 5% 1	414
March	1st to 10th	Day	16% 12% 39% 27% 6%	500
	11th to 20th	Day	15% 10% 38% 29% 7% 2	500
	21st to end	Day	21% 8% 34% 29% 7% 1	550
April	1st to 10th	Day	21% 9% 33% 27% 8% 1	500
	11th to 20th	Day	16% 7% 31% 34% 11% 1	492
	21st to end	Day	24% 6% 25% 31% 13% 1	500
May	1st to 10th	Day	24% 6% 26% 30% 12% 2	503
	11th to 20th	Day	23% 3 21% 38% 13% 2	527
	21st to end	Day	21% 3 12% 34% 23% 7%	573
June	1st to 10th	Day	17% 3 18% 35% 23% 4	530
	11th to 20th	Day	13% 3 17% 40% 23% 4	530
	21st to end	Day	10% 2 14% 40% 29% 5%	530
July	1st to 10th	Day	11% 3 9% 32% 36% 10%	525
	11th to 20th	Day	8% 2 6% 38% 37% 10%	524
	21st to end	Day	13% 1 12% 37% 32% 5%	576
August	1st to 10th	Day	11% 3 8% 37% 33% 7%	526
	11th to 20th	Day	13% 2 7% 35% 34% 9%	519
	21st to end	Day	11% 3 10% 36% 28% 12%	583
September	1st to 10th	Day	17% 2 16% 29% 25% 10%	530
	11th to 20th	Day	12% 1 13% 33% 31% 10%	530
	21st to end	Day	22% 5% 16% 34% 19% 3	530
October	1st to 10th	Day	23% 3 16% 29% 21% 8%	530
	11th to 20th	Day	17% 7% 23% 29% 21% 3	530
	21st to end	Day	18% 9% 27% 26% 17% 3	509
November	1st to 10th	Day	15% 6% 28% 30% 17% 3	425
	11th to 20th	Day	16% 12% 35% 25% 13%	430
	21st to end	Day	15% 11% 31% 30% 10% 2	398
December	1st to 10th	Day	21% 10% 35% 25% 9%	220
	11th to 20th	Day	23% 10% 36% 25% 6%	220
	21st to end	Day	21% 11% 29% 27% 12%	242
January	1st to 10th	Night	18% 14% 41% 21% 5%	840
	11th to 20th	Night	22% 14% 36% 23% 4	840
	21st to end	Night	18% 14% 43% 23% 2	924
February	1st to 10th	Night	23% 10% 39% 24% 4	801
	11th to 20th	Night	22% 15% 42% 19% 1	783
	21st to end	Night	22% 13% 36% 27% 4	660
March	1st to 10th	Night	20% 10% 39% 25% 6%	800
	11th to 20th	Night	19% 10% 35% 27% 7% 1	800
	21st to end	Night	20% 7% 33% 32% 7% 1	880
April	1st to 10th	Night	22% 8% 34% 28% 7% 1	800
	11th to 20th	Night	19% 6% 28% 36% 10%	791
	21st to end	Night	18% 5% 29% 36% 10% 2	800
May	1st to 10th	Night	21% 5% 24% 37% 11% 2	609
	11th to 20th	Night	22% 4 25% 37% 11% 1	481
	21st to end	Night	20% 3 12% 31% 29% 4	433
June	1st to 10th	Night	18% 2 16% 36% 26% 3	400
	11th to 20th	Night	15% 3 13% 43% 26% 2	400
	21st to end	Night	10% 3 13% 44% 28% 2	400
July	1st to 10th	Night	11% 4 11% 40% 31% 3	390
	11th to 20th	Night	10% 2 8% 38% 37% 4	388
	21st to end	Night	10% 2 13% 41% 32% 3	438
August	1st to 10th	Night	12% 2 10% 39% 33% 4	611
	11th to 20th	Night	12% 2 12% 34% 34% 6%	790
	21st to end	Night	13% 2 9% 36% 32% 7%	880
September	1st to 10th	Night	16% 3 15% 33% 28% 6%	800
	11th to 20th	Night	16% 2 12% 32% 30% 7%	800
	21st to end	Night	24% 3 17% 31% 22% 4	800
October	1st to 10th	Night	22% 3 24% 24% 20% 7%	800
	11th to 20th	Night	19% 8% 24% 32% 16% 2	800
	21st to end	Night	21% 7% 31% 27% 12% 1	880
November	1st to 10th	Night	15% 8% 30% 32% 13% 3	820
	11th to 20th	Night	19% 12% 33% 28% 9%	840
	21st to end	Night	15% 11% 36% 28% 9% 1	840
December	1st to 10th	Night	22% 13% 35% 22% 8% 1	840
	11th to 20th	Night	20% 11% 38% 25% 5% 1	840
	21st to end	Night	21% 10% 38% 27% 5%	924

Page generated at 2026-01-29 01:21:41. Version ac07

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