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 2024-11-28.

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 6% 8% 40%	101469
	Night	16% 8% 3 6% 4 4 4 3 5% 7% 41%	98080
Transparency	Day	40% 7% 12% 23% 15% 2	105027
	Night	42% 5% 11% 23% 16% 3	102598
Seeing	Day	17% 6% 23% 32% 18% 4	15182
	Night	18% 7% 27% 30% 14% 2	24382

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	14% 9% 2 5% 3 3 3 3 5% 6% 47%	2517
	11th to 20th	Day	15% 9% 3 8% 4 4 4 3 5% 6% 40%	2520
	21st to end	Day	22% 11% 3 8% 4 4 3 3 4 5% 33%	3088
February	1st to 10th	Day	15% 10% 3 7% 4 4 3 3 6% 7% 39%	1748
	11th to 20th	Day	18% 7% 2 6% 3 4 3 4 5% 6% 42%	1848
	21st to end	Day	17% 9% 2 8% 4 4 4 4 5% 6% 39%	1570
March	1st to 10th	Day	26% 7% 2 4 3 3 3 2 4 5% 40%	3116
	11th to 20th	Day	9% 4 2 6% 4 4 4 4 5% 8% 49%	3345
	21st to end	Day	19% 8% 2 5% 3 3 4 3 5% 5% 42%	4129
April	1st to 10th	Day	17% 8% 2 5% 5% 4 4 3 5% 7% 40%	2280
	11th to 20th	Day	14% 7% 3 5% 3 3 4 4 5% 7% 44%	2254
	21st to end	Day	17% 7% 2 5% 4 5% 5% 4 6% 6% 39%	2280
May	1st to 10th	Day	22% 12% 4 9% 5% 4 5% 3 5% 7% 25%	4096
	11th to 20th	Day	25% 7% 2 6% 5% 4 4 3 4 5% 32%	4292
	21st to end	Day	12% 7% 3 7% 4 4 5% 4 6% 10% 40%	4837
June	1st to 10th	Day	13% 6% 3 6% 4 4 5% 5% 6% 9% 38%	2660
	11th to 20th	Day	11% 6% 2 5% 4 5% 5% 5% 7% 10% 40%	2660
	21st to end	Day	8% 5% 2 5% 5% 5% 5% 4 8% 10% 43%	2660
July	1st to 10th	Day	7% 8% 3 7% 5% 5% 6% 5% 7% 10% 37%	4440
	11th to 20th	Day	10% 6% 2 6% 5% 5% 6% 5% 8% 9% 38%	4440
	21st to end	Day	11% 8% 2 7% 5% 6% 6% 5% 7% 8% 34%	4814
August	1st to 10th	Day	15% 6% 2 7% 5% 4 5% 4 7% 10% 34%	4042
	11th to 20th	Day	12% 6% 2 6% 5% 4 4 4 6% 8% 42%	3730
	21st to end	Day	8% 5% 2 5% 4 4 4 4 7% 10% 48%	4180
September	1st to 10th	Day	14% 6% 2 5% 3 3 3 3 5% 9% 48%	2280
	11th to 20th	Day	9% 5% 2 6% 4 3 4 3 5% 8% 50%	2195
	21st to end	Day	18% 7% 4 6% 4 4 5% 3 4 6% 39%	2090
October	1st to 10th	Day	20% 6% 2 5% 3 3 3 3 5% 6% 44%	1992
	11th to 20th	Day	16% 5% 2 5% 3 2 3 2 4 6% 52%	1900
	21st to end	Day	18% 6% 2 5% 3 3 4 3 5% 7% 44%	1962
November	1st to 10th	Day	13% 6% 2 5% 3 4 4 3 4 7% 49%	1761
	11th to 20th	Day	15% 6% 3 6% 4 4 3 3 4 6% 47%	1800
	21st to end	Day	15% 5% 2 5% 5% 4 4 4 5% 8% 44%	1745
December	1st to 10th	Day	18% 7% 2 6% 3 4 4 3 5% 8% 39%	1520
	11th to 20th	Day	18% 8% 2 5% 3 3 3 3 4 6% 45%	1906
	21st to end	Day	15% 8% 3 6% 4 4 4 4 6% 7% 39%	2772
January	1st to 10th	Night	17% 7% 2 4 3 3 3 3 4 6% 47%	4429
	11th to 20th	Night	19% 9% 2 6% 4 3 3 3 4 5% 43%	4440
	21st to end	Night	22% 10% 3 7% 4 4 3 3 4 6% 35%	4564
February	1st to 10th	Night	18% 8% 3 6% 3 4 4 3 5% 6% 42%	2432
	11th to 20th	Night	18% 9% 3 5% 4 3 3 3 5% 6% 41%	2218
	21st to end	Night	19% 8% 2 6% 4 2 3 3 5% 6% 43%	1884
March	1st to 10th	Night	22% 11% 4 6% 4 3 3 2 3 5% 38%	3724
	11th to 20th	Night	13% 6% 3 5% 4 4 4 2 5% 6% 47%	3612
	21st to end	Night	21% 9% 3 7% 4 3 3 3 3 4 41%	3502
April	1st to 10th	Night	17% 8% 3 7% 4 4 3 3 4 7% 41%	1900
	11th to 20th	Night	16% 8% 3 5% 4 4 3 3 5% 5% 44%	1875
	21st to end	Night	17% 7% 3 5% 3 4 4 4 5% 8% 41%	1900
May	1st to 10th	Night	21% 12% 4 8% 4 4 4 3 5% 7% 27%	2843
	11th to 20th	Night	26% 10% 3 6% 4 3 3 3 4 6% 31%	2630
	21st to end	Night	15% 9% 3 6% 5% 4 4 3 5% 8% 38%	2738
June	1st to 10th	Night	16% 8% 3 6% 4 4 5% 4 5% 8% 38%	1520
	11th to 20th	Night	13% 5% 3 6% 5% 4 4 3 6% 8% 42%	1520
	21st to end	Night	8% 6% 2 6% 4 5% 5% 5% 7% 11% 42%	1520
July	1st to 10th	Night	8% 10% 4 8% 5% 5% 7% 4 6% 8% 35%	2520
	11th to 20th	Night	9% 7% 3 7% 5% 5% 4 4 8% 11% 38%	2520
	21st to end	Night	15% 9% 3 8% 5% 5% 5% 4 6% 8% 33%	2739
August	1st to 10th	Night	18% 9% 3 7% 5% 4 5% 3 5% 9% 31%	2851
	11th to 20th	Night	10% 6% 2 7% 5% 4 4 4 6% 7% 44%	3097
	21st to end	Night	8% 5% 2 5% 4 4 4 4 6% 8% 52%	3476
September	1st to 10th	Night	14% 6% 2 6% 4 4 5% 3 5% 7% 44%	1900
	11th to 20th	Night	12% 6% 3 4 3 3 3 3 5% 8% 50%	1983
	21st to end	Night	20% 8% 3 5% 3 4 3 3 5% 6% 39%	2090
October	1st to 10th	Night	20% 8% 2 5% 4 3 4 3 5% 5% 42%	2184
	11th to 20th	Night	16% 5% 2 4 3 3 4 3 4 7% 50%	2280
	21st to end	Night	18% 7% 2 5% 4 3 3 2 4 6% 45%	2635
November	1st to 10th	Night	13% 6% 2 4 4 3 4 3 4 6% 52%	2537
	11th to 20th	Night	16% 7% 3 6% 3 3 3 3 5% 4 47%	2600
	21st to end	Night	13% 5% 2 4 5% 4 4 3 5% 6% 47%	2585
December	1st to 10th	Night	19% 8% 3 5% 4 3 3 3 5% 7% 40%	2660
	11th to 20th	Night	17% 5% 2 6% 4 4 4 3 5% 8% 41%	3288
	21st to end	Night	15% 9% 3 6% 4 4 4 4 5% 6% 39%	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	39% 4 10% 27% 17% 3	2518
	11th to 20th	Day	45% 5% 10% 23% 14% 4	2520
	21st to end	Day	53% 7% 7% 22% 9% 2	3088
February	1st to 10th	Day	44% 5% 13% 24% 13% 1	1748
	11th to 20th	Day	42% 6% 8% 26% 16% 3	1857
	21st to end	Day	47% 5% 9% 22% 13% 5%	1570
March	1st to 10th	Day	47% 4 9% 27% 10% 2	3119
	11th to 20th	Day	31% 7% 11% 33% 17% 3	3345
	21st to end	Day	44% 5% 9% 18% 20% 5%	4129
April	1st to 10th	Day	43% 6% 10% 20% 16% 5%	2280
	11th to 20th	Day	38% 6% 14% 23% 16% 3	2254
	21st to end	Day	42% 6% 10% 19% 18% 4	2280
May	1st to 10th	Day	56% 9% 9% 16% 8% 2	4110
	11th to 20th	Day	52% 8% 12% 19% 8% 1	4296
	21st to end	Day	37% 10% 12% 22% 17% 2	4837
June	1st to 10th	Day	40% 9% 14% 21% 15% 2	2660
	11th to 20th	Day	36% 9% 14% 27% 12% 2	2660
	21st to end	Day	34% 10% 16% 23% 17% 1	2660
July	1st to 10th	Day	41% 12% 15% 18% 14% 1	4370
	11th to 20th	Day	39% 9% 20% 21% 10% 1	4365
	21st to end	Day	44% 9% 13% 20% 13% 1	4661
August	1st to 10th	Day	45% 7% 19% 20% 8%	4028
	11th to 20th	Day	39% 7% 14% 29% 10% 1	3766
	21st to end	Day	30% 7% 15% 29% 17% 2	4180
September	1st to 10th	Day	35% 6% 14% 21% 20% 2	2280
	11th to 20th	Day	32% 7% 12% 24% 23% 3	2195
	21st to end	Day	47% 6% 8% 19% 18% 2	2090
October	1st to 10th	Day	35% 4 12% 22% 23% 4	3304
	11th to 20th	Day	25% 4 9% 24% 32% 6%	3140
	21st to end	Day	28% 4 15% 26% 24% 4	3213
November	1st to 10th	Day	36% 4 12% 26% 19% 3	1761
	11th to 20th	Day	39% 5% 9% 22% 22% 3	1800
	21st to end	Day	39% 5% 12% 31% 11% 2	1745
December	1st to 10th	Day	45% 4 14% 22% 13% 1	1520
	11th to 20th	Day	42% 4 11% 26% 15% 2	1906
	21st to end	Day	42% 8% 13% 24% 13% 1	2772
January	1st to 10th	Night	38% 4 9% 32% 13% 4	4429
	11th to 20th	Night	45% 4 10% 25% 13% 3	4440
	21st to end	Night	50% 5% 7% 22% 14% 1	4564
February	1st to 10th	Night	43% 5% 14% 23% 14% 2	2432
	11th to 20th	Night	44% 4 8% 20% 18% 5%	2220
	21st to end	Night	43% 4 8% 23% 18% 5%	1884
March	1st to 10th	Night	51% 3 7% 23% 13% 3	3734
	11th to 20th	Night	37% 6% 11% 27% 15% 4	3613
	21st to end	Night	47% 5% 6% 17% 22% 4	3502
April	1st to 10th	Night	45% 5% 9% 19% 18% 5%	1900
	11th to 20th	Night	42% 4 10% 20% 20% 4	1875
	21st to end	Night	41% 6% 8% 20% 20% 5%	1900
May	1st to 10th	Night	55% 6% 9% 19% 9% 1	2849
	11th to 20th	Night	55% 5% 12% 17% 10% 1	2631
	21st to end	Night	41% 10% 13% 18% 17% 1	2739
June	1st to 10th	Night	44% 8% 8% 20% 18% 1	1520
	11th to 20th	Night	39% 8% 12% 26% 14% 2	1520
	21st to end	Night	35% 8% 16% 25% 14% 2	1520
July	1st to 10th	Night	46% 8% 13% 19% 11% 2	2480
	11th to 20th	Night	39% 7% 18% 26% 9% 1	2472
	21st to end	Night	48% 6% 14% 17% 14% 1	2651
August	1st to 10th	Night	50% 7% 19% 15% 8% 1	2841
	11th to 20th	Night	38% 6% 13% 32% 11% 1	3127
	21st to end	Night	31% 6% 11% 31% 20% 2	3476
September	1st to 10th	Night	40% 6% 12% 20% 19% 3	1900
	11th to 20th	Night	33% 5% 12% 23% 24% 3	1983
	21st to end	Night	46% 6% 7% 20% 19% 2	2090
October	1st to 10th	Night	38% 5% 10% 22% 22% 3	3639
	11th to 20th	Night	25% 3 10% 28% 29% 5%	3779
	21st to end	Night	28% 3 11% 30% 24% 4	4334
November	1st to 10th	Night	34% 5% 11% 25% 21% 4	2537
	11th to 20th	Night	40% 5% 8% 22% 21% 4	2600
	21st to end	Night	38% 5% 12% 27% 17% 2	2585
December	1st to 10th	Night	45% 5% 12% 23% 14% 2	2660
	11th to 20th	Night	42% 6% 11% 19% 18% 3	3288
	21st to end	Night	44% 6% 14% 24% 11% 1	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	14% 12% 44% 22% 7% 1	180
	11th to 20th	Day	17% 20% 35% 24% 3 1	180
	21st to end	Day	22% 10% 34% 26% 6% 2	286
February	1st to 10th	Day	22% 11% 37% 25% 5%	308
	11th to 20th	Day	23% 13% 38% 24% 2	456
	21st to end	Day	22% 13% 36% 24% 4 1	382
March	1st to 10th	Day	17% 12% 37% 28% 6%	460
	11th to 20th	Day	16% 10% 38% 29% 6% 2	460
	21st to end	Day	21% 8% 33% 29% 8% 1	506
April	1st to 10th	Day	20% 9% 33% 28% 9% 1	460
	11th to 20th	Day	15% 7% 31% 35% 11% 1	452
	21st to end	Day	25% 6% 26% 31% 11% 1	460
May	1st to 10th	Day	24% 6% 27% 30% 11% 3	463
	11th to 20th	Day	22% 3 20% 38% 15% 2	487
	21st to end	Day	19% 3 12% 33% 25% 8%	529
June	1st to 10th	Day	16% 3 19% 36% 23% 4	490
	11th to 20th	Day	11% 3 17% 41% 23% 4	490
	21st to end	Day	10% 2 15% 42% 28% 3	490
July	1st to 10th	Day	11% 3 9% 32% 35% 10%	485
	11th to 20th	Day	7% 1 6% 38% 37% 9%	484
	21st to end	Day	14% 1 12% 38% 30% 5%	532
August	1st to 10th	Day	12% 3 9% 37% 33% 8%	486
	11th to 20th	Day	12% 2 7% 37% 33% 9%	479
	21st to end	Day	11% 3 10% 36% 27% 13%	539
September	1st to 10th	Day	17% 2 16% 28% 26% 11%	490
	11th to 20th	Day	12% 1 14% 31% 32% 10%	490
	21st to end	Day	23% 5% 17% 33% 19% 3	490
October	1st to 10th	Day	24% 4 16% 30% 20% 7%	490
	11th to 20th	Day	16% 7% 23% 30% 22% 3	490
	21st to end	Day	19% 9% 25% 27% 17% 3	472
November	1st to 10th	Day	15% 6% 27% 30% 18% 4	395
	11th to 20th	Day	17% 11% 34% 25% 13%	400
	21st to end	Day	15% 12% 31% 30% 11% 2	363
December	1st to 10th	Day	22% 9% 36% 22% 9% 1	180
	11th to 20th	Day	23% 11% 34% 24% 7%	180
	21st to end	Day	24% 11% 27% 27% 12%	198
January	1st to 10th	Night	19% 13% 41% 21% 5%	760
	11th to 20th	Night	23% 13% 35% 24% 5%	760
	21st to end	Night	19% 13% 41% 24% 2	836
February	1st to 10th	Night	22% 11% 38% 25% 4	760
	11th to 20th	Night	22% 14% 43% 19% 1	743
	21st to end	Night	22% 13% 35% 26% 4	628
March	1st to 10th	Night	20% 10% 38% 25% 6%	760
	11th to 20th	Night	19% 10% 36% 27% 6% 1	760
	21st to end	Night	21% 7% 33% 31% 7% 1	836
April	1st to 10th	Night	21% 8% 35% 28% 7% 1	760
	11th to 20th	Night	19% 6% 27% 38% 11%	751
	21st to end	Night	19% 5% 29% 36% 9% 2	760
May	1st to 10th	Night	21% 6% 24% 37% 11% 2	579
	11th to 20th	Night	22% 4 25% 37% 11% 1	457
	21st to end	Night	18% 3 12% 32% 31% 5%	411
June	1st to 10th	Night	18% 2 16% 36% 26% 3	380
	11th to 20th	Night	13% 2 14% 43% 26% 2	380
	21st to end	Night	9% 3 14% 46% 26% 2	380
July	1st to 10th	Night	10% 4 11% 41% 31% 4	370
	11th to 20th	Night	9% 2 8% 39% 38% 4	368
	21st to end	Night	10% 2 13% 41% 32% 2	416
August	1st to 10th	Night	12% 2 10% 40% 32% 4	580
	11th to 20th	Night	11% 2 12% 36% 33% 6%	750
	21st to end	Night	13% 2 9% 36% 32% 7%	836
September	1st to 10th	Night	16% 3 14% 33% 28% 6%	760
	11th to 20th	Night	16% 3 13% 31% 30% 7%	760
	21st to end	Night	23% 3 17% 31% 22% 4	760
October	1st to 10th	Night	23% 3 24% 24% 20% 6%	760
	11th to 20th	Night	18% 7% 24% 33% 16% 2	760
	21st to end	Night	22% 7% 31% 27% 13% 1	836
November	1st to 10th	Night	15% 7% 30% 32% 13% 3	780
	11th to 20th	Night	19% 11% 32% 29% 9% 1	800
	21st to end	Night	15% 11% 36% 28% 8% 1	789
December	1st to 10th	Night	23% 13% 33% 22% 8% 1	760
	11th to 20th	Night	20% 10% 39% 25% 5% 1	760
	21st to end	Night	21% 10% 38% 27% 4	836

Page generated at 2024-11-25 00:22:15. Version ac07

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