Newark
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Newark clear sky chart from 2005-11-06 to 2026-03-18.

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	17% 7% 2 6% 4 4 4 4 5% 7% 40%	131131
	Night	17% 7% 2 6% 4 4 4 3 5% 6% 42%	130357
Transparency	Day	41% 6% 12% 22% 17% 3	134658
	Night	41% 5% 11% 22% 17% 3	134917
Seeing	Day	20% 15% 31% 22% 10% 3	16674
	Night	20% 11% 31% 28% 9% 1	25950

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	12% 6% 2 5% 4 4 4 3 5% 6% 49%	4661
	11th to 20th	Day	15% 8% 3 5% 4 4 3 3 5% 6% 45%	4650
	21st to end	Day	16% 8% 3 7% 4 4 4 3 5% 6% 42%	5616
February	1st to 10th	Day	16% 8% 3 6% 4 4 3 3 6% 6% 41%	1895
	11th to 20th	Day	15% 7% 3 6% 3 4 4 3 4 6% 43%	2048
	21st to end	Day	20% 8% 2 5% 4 3 4 4 5% 6% 38%	1730
March	1st to 10th	Day	22% 6% 2 5% 4 3 3 3 5% 5% 42%	4576
	11th to 20th	Day	13% 8% 2 6% 4 4 5% 3 6% 7% 42%	4864
	21st to end	Day	18% 6% 2 6% 4 3 3 3 5% 6% 43%	5917
April	1st to 10th	Day	19% 8% 2 6% 4 4 4 4 5% 7% 38%	2400
	11th to 20th	Day	17% 6% 2 6% 4 5% 4 3 5% 7% 41%	2374
	21st to end	Day	19% 6% 2 6% 4 4 4 3 5% 7% 40%	2414
May	1st to 10th	Day	29% 8% 2 5% 4 4 4 4 5% 8% 28%	5886
	11th to 20th	Day	24% 8% 3 6% 4 3 4 3 4 7% 34%	6288
	21st to end	Day	21% 5% 2 5% 4 4 5% 4 6% 9% 36%	6949
June	1st to 10th	Day	16% 6% 2 5% 5% 4 5% 5% 7% 8% 38%	2800
	11th to 20th	Day	16% 7% 2 6% 5% 4 5% 4 6% 8% 37%	2800
	21st to end	Day	11% 6% 2 6% 5% 5% 5% 5% 7% 9% 40%	2800
July	1st to 10th	Day	10% 6% 3 7% 5% 5% 6% 5% 7% 11% 36%	6360
	11th to 20th	Day	10% 7% 3 8% 5% 5% 6% 5% 8% 11% 32%	6360
	21st to end	Day	12% 7% 2 6% 5% 5% 6% 5% 6% 9% 37%	6926
August	1st to 10th	Day	19% 6% 2 6% 5% 5% 5% 4 7% 9% 32%	4270
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 4 6% 8% 44%	3850
	21st to end	Day	10% 5% 2 6% 5% 4 4 4 6% 8% 46%	4312
September	1st to 10th	Day	14% 5% 2 5% 4 5% 5% 4 5% 7% 44%	2400
	11th to 20th	Day	13% 5% 2 5% 3 3 4 3 5% 7% 50%	2319
	21st to end	Day	18% 6% 3 7% 5% 4 4 4 5% 6% 39%	2200
October	1st to 10th	Day	19% 6% 2 5% 4 3 4 3 4 7% 43%	2080
	11th to 20th	Day	16% 5% 2 5% 4 4 4 3 5% 6% 48%	2000
	21st to end	Day	20% 5% 1 5% 3 4 4 3 5% 6% 45%	2050
November	1st to 10th	Day	14% 5% 2 5% 3 3 3 3 4 5% 52%	1851
	11th to 20th	Day	17% 5% 2 5% 4 3 4 3 4 6% 48%	1890
	21st to end	Day	16% 7% 1 5% 3 4 4 3 5% 6% 44%	1801
December	1st to 10th	Day	16% 7% 2 5% 3 3 4 2 5% 8% 45%	2680
	11th to 20th	Day	23% 6% 2 4 3 2 3 2 4 6% 45%	3066
	21st to end	Day	18% 7% 2 7% 4 4 4 4 5% 7% 38%	4048
January	1st to 10th	Night	12% 8% 3 5% 4 3 4 3 5% 6% 47%	8234
	11th to 20th	Night	15% 9% 2 6% 3 3 4 3 4 5% 46%	8235
	21st to end	Night	16% 8% 2 5% 3 4 4 3 5% 6% 44%	8563
February	1st to 10th	Night	16% 9% 3 5% 4 4 4 3 5% 6% 42%	2723
	11th to 20th	Night	18% 8% 2 6% 4 4 3 3 5% 6% 40%	2458
	21st to end	Night	19% 8% 2 6% 4 4 3 3 5% 6% 41%	2076
March	1st to 10th	Night	20% 8% 2 5% 3 3 3 2 4 5% 43%	5484
	11th to 20th	Night	14% 9% 3 6% 3 3 3 3 4 6% 45%	5246
	21st to end	Night	18% 9% 3 7% 4 4 3 3 5% 6% 40%	5013
April	1st to 10th	Night	20% 7% 2 7% 4 4 4 4 6% 5% 38%	2000
	11th to 20th	Night	19% 7% 2 6% 4 4 5% 3 4 7% 40%	1975
	21st to end	Night	18% 7% 2 5% 4 3 4 3 4 7% 43%	1985
May	1st to 10th	Night	27% 10% 3 7% 4 4 4 3 5% 6% 28%	4054
	11th to 20th	Night	23% 9% 3 6% 5% 4 3 3 4 5% 35%	3634
	21st to end	Night	22% 8% 2 6% 4 4 4 3 5% 7% 35%	3926
June	1st to 10th	Night	16% 7% 2 5% 4 4 5% 3 6% 7% 40%	1600
	11th to 20th	Night	15% 7% 2 5% 5% 4 4 4 7% 8% 41%	1600
	21st to end	Night	10% 4 2 5% 5% 4 5% 4 7% 9% 43%	1600
July	1st to 10th	Night	10% 6% 3 8% 6% 6% 5% 5% 6% 9% 37%	3600
	11th to 20th	Night	14% 8% 3 8% 5% 4 5% 5% 7% 9% 32%	3600
	21st to end	Night	13% 6% 2 6% 4 4 5% 4 6% 9% 42%	3926
August	1st to 10th	Night	23% 6% 3 6% 4 4 5% 4 6% 8% 33%	2828
	11th to 20th	Night	14% 6% 3 7% 4 5% 4 4 6% 7% 40%	3197
	21st to end	Night	10% 5% 2 5% 4 3 4 3 5% 7% 52%	3586
September	1st to 10th	Night	15% 5% 2 7% 4 4 4 3 5% 6% 44%	2000
	11th to 20th	Night	14% 5% 1 4 3 3 4 3 4 7% 51%	2080
	21st to end	Night	18% 7% 2 6% 4 4 3 3 4 6% 43%	2200
October	1st to 10th	Night	18% 6% 3 5% 4 3 3 3 5% 7% 43%	2315
	11th to 20th	Night	15% 5% 2 6% 3 2 4 3 4 6% 50%	2400
	21st to end	Night	20% 7% 2 5% 3 3 3 3 4 5% 46%	2790
November	1st to 10th	Night	12% 5% 1 5% 4 3 4 3 5% 5% 52%	2667
	11th to 20th	Night	18% 6% 2 5% 3 3 3 3 4 5% 48%	2730
	21st to end	Night	15% 6% 2 5% 4 3 4 4 5% 7% 46%	2814
December	1st to 10th	Night	15% 7% 2 6% 3 3 3 3 5% 6% 47%	4720
	11th to 20th	Night	25% 7% 2 4 3 3 3 3 3 4 43%	5348
	21st to end	Night	20% 9% 3 6% 4 3 4 3 4 5% 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	36% 3 11% 30% 19% 2	4662
	11th to 20th	Day	41% 3 10% 22% 18% 6%	4680
	21st to end	Day	44% 3 11% 24% 17% 1	5616
February	1st to 10th	Day	44% 5% 13% 24% 13% 2	1895
	11th to 20th	Day	43% 4 10% 25% 16% 2	2057
	21st to end	Day	45% 5% 11% 22% 14% 3	1730
March	1st to 10th	Day	42% 5% 12% 20% 14% 8%	4579
	11th to 20th	Day	38% 7% 13% 27% 11% 4	4864
	21st to end	Day	42% 5% 10% 13% 25% 5%	5917
April	1st to 10th	Day	45% 5% 11% 19% 16% 4	2400
	11th to 20th	Day	42% 6% 11% 21% 17% 3	2374
	21st to end	Day	42% 5% 10% 21% 17% 4	2414
May	1st to 10th	Day	53% 6% 15% 14% 10% 1	5897
	11th to 20th	Day	49% 6% 10% 20% 14% 1	6292
	21st to end	Day	44% 7% 11% 23% 14% 1	6949
June	1st to 10th	Day	40% 9% 13% 21% 15% 2	2800
	11th to 20th	Day	43% 8% 13% 22% 12% 2	2800
	21st to end	Day	38% 9% 14% 22% 16% 1	2800
July	1st to 10th	Day	41% 9% 13% 21% 15% 1	6290
	11th to 20th	Day	41% 9% 19% 20% 10% 1	6285
	21st to end	Day	40% 6% 12% 20% 20% 2	6728
August	1st to 10th	Day	46% 8% 15% 21% 9% 1	4256
	11th to 20th	Day	37% 7% 14% 29% 13% 1	3886
	21st to end	Day	34% 6% 11% 27% 20% 2	4312
September	1st to 10th	Day	38% 7% 11% 22% 20% 3	2400
	11th to 20th	Day	33% 5% 11% 24% 24% 2	2319
	21st to end	Day	45% 6% 10% 18% 18% 3	2200
October	1st to 10th	Day	37% 4 11% 19% 23% 6%	3392
	11th to 20th	Day	26% 4 11% 23% 31% 5%	3240
	21st to end	Day	28% 4 13% 25% 26% 4	3288
November	1st to 10th	Day	34% 4 12% 23% 24% 3	1851
	11th to 20th	Day	38% 4 9% 24% 21% 4	1890
	21st to end	Day	40% 4 14% 28% 11% 2	1801
December	1st to 10th	Day	39% 3 15% 28% 13% 2	2680
	11th to 20th	Day	42% 3 13% 23% 16% 2	3066
	21st to end	Day	44% 7% 10% 22% 15% 2	4048
January	1st to 10th	Night	39% 4 12% 23% 19% 3	8234
	11th to 20th	Night	42% 3 12% 21% 17% 6%	8280
	21st to end	Night	42% 4 9% 21% 20% 4	8563
February	1st to 10th	Night	44% 5% 12% 24% 13% 2	2723
	11th to 20th	Night	45% 4 9% 19% 18% 4	2460
	21st to end	Night	44% 4 8% 25% 16% 3	2076
March	1st to 10th	Night	43% 5% 10% 21% 13% 9%	5494
	11th to 20th	Night	39% 6% 14% 24% 13% 4	5247
	21st to end	Night	46% 5% 7% 14% 23% 5%	5013
April	1st to 10th	Night	46% 5% 10% 18% 16% 4	2000
	11th to 20th	Night	45% 5% 9% 19% 19% 2	1975
	21st to end	Night	41% 6% 8% 21% 19% 4	1985
May	1st to 10th	Night	56% 6% 12% 14% 10% 1	4060
	11th to 20th	Night	51% 7% 13% 13% 14% 2	3635
	21st to end	Night	47% 6% 13% 21% 11% 2	3927
June	1st to 10th	Night	41% 7% 10% 20% 20% 2	1600
	11th to 20th	Night	39% 8% 14% 26% 12% 1	1600
	21st to end	Night	36% 9% 14% 24% 16% 2	1600
July	1st to 10th	Night	44% 8% 13% 19% 14% 2	3560
	11th to 20th	Night	47% 8% 14% 20% 10% 1	3552
	21st to end	Night	38% 6% 15% 20% 19% 1	3809
August	1st to 10th	Night	49% 8% 16% 17% 9% 1	2818
	11th to 20th	Night	41% 7% 13% 28% 10% 1	3227
	21st to end	Night	30% 6% 11% 31% 20% 2	3586
September	1st to 10th	Night	40% 7% 10% 24% 19% 1	2000
	11th to 20th	Night	33% 5% 11% 23% 25% 3	2080
	21st to end	Night	42% 5% 9% 21% 21% 2	2200
October	1st to 10th	Night	37% 6% 12% 23% 20% 2	3783
	11th to 20th	Night	25% 4 9% 27% 30% 4	3899
	21st to end	Night	30% 4 11% 29% 23% 2	4502
November	1st to 10th	Night	34% 5% 10% 24% 22% 4	2667
	11th to 20th	Night	39% 4 8% 24% 20% 5%	2730
	21st to end	Night	39% 4 12% 28% 16% 2	2814
December	1st to 10th	Night	39% 4 12% 30% 13% 2	4720
	11th to 20th	Night	46% 3 9% 22% 16% 4	5348
	21st to end	Night	45% 5% 10% 18% 17% 4	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	23% 28% 31% 15% 2	220
	11th to 20th	Day	24% 34% 31% 9% 2	220
	21st to end	Day	20% 29% 33% 13% 5% 1	333
February	1st to 10th	Day	24% 23% 36% 15% 1	335
	11th to 20th	Day	26% 21% 36% 15% 2	536
	21st to end	Day	26% 19% 37% 15% 3	446
March	1st to 10th	Day	24% 22% 31% 18% 4	540
	11th to 20th	Day	25% 20% 36% 15% 5% 1	528
	21st to end	Day	27% 21% 33% 13% 4 1	550
April	1st to 10th	Day	27% 22% 32% 12% 6% 1	500
	11th to 20th	Day	23% 21% 32% 15% 8% 1	492
	21st to end	Day	25% 18% 33% 17% 5% 2	500
May	1st to 10th	Day	31% 18% 28% 15% 5% 2	503
	11th to 20th	Day	23% 14% 35% 20% 6% 1	527
	21st to end	Day	21% 8% 30% 25% 14% 2	573
June	1st to 10th	Day	17% 13% 29% 27% 12% 2	530
	11th to 20th	Day	18% 13% 32% 25% 11% 2	530
	21st to end	Day	14% 12% 30% 28% 15% 2	530
July	1st to 10th	Day	13% 5% 28% 32% 18% 5%	525
	11th to 20th	Day	10% 5% 28% 32% 20% 5%	524
	21st to end	Day	14% 7% 30% 30% 16% 3	576
August	1st to 10th	Day	12% 6% 27% 32% 17% 6%	526
	11th to 20th	Day	15% 5% 24% 33% 19% 5%	519
	21st to end	Day	11% 8% 30% 30% 15% 6%	583
September	1st to 10th	Day	18% 8% 29% 23% 15% 7%	530
	11th to 20th	Day	14% 7% 27% 28% 14% 9%	530
	21st to end	Day	22% 11% 28% 24% 11% 4	530
October	1st to 10th	Day	23% 8% 28% 21% 15% 5%	530
	11th to 20th	Day	20% 16% 29% 23% 10% 2	530
	21st to end	Day	22% 14% 34% 21% 7% 2	500
November	1st to 10th	Day	15% 14% 35% 22% 11% 3	425
	11th to 20th	Day	23% 19% 30% 22% 5%	430
	21st to end	Day	20% 19% 36% 19% 4 1	341
December	1st to 10th	Day	24% 24% 33% 13% 7%	220
	11th to 20th	Day	30% 23% 33% 11% 3	220
	21st to end	Day	27% 18% 37% 11% 7%	242
January	1st to 10th	Night	18% 17% 40% 22% 3	840
	11th to 20th	Night	25% 18% 31% 23% 3	840
	21st to end	Night	19% 17% 41% 21% 2	924
February	1st to 10th	Night	21% 15% 37% 25% 3	840
	11th to 20th	Night	23% 18% 39% 19% 1	823
	21st to end	Night	21% 19% 37% 21% 3	692
March	1st to 10th	Night	22% 15% 37% 22% 5%	840
	11th to 20th	Night	22% 16% 36% 21% 4 1	829
	21st to end	Night	21% 15% 38% 20% 5%	880
April	1st to 10th	Night	24% 16% 35% 21% 4	800
	11th to 20th	Night	22% 16% 34% 23% 5%	791
	21st to end	Night	21% 13% 35% 25% 6% 1	785
May	1st to 10th	Night	24% 13% 35% 22% 7%	600
	11th to 20th	Night	22% 10% 37% 25% 7%	427
	21st to end	Night	20% 5% 24% 38% 13% 1	433
June	1st to 10th	Night	19% 7% 29% 35% 11%	400
	11th to 20th	Night	16% 7% 26% 38% 14%	400
	21st to end	Night	11% 4 24% 50% 10% 1	400
July	1st to 10th	Night	12% 5% 24% 41% 17% 1	390
	11th to 20th	Night	14% 3 21% 42% 19% 1	388
	21st to end	Night	14% 4 21% 44% 16% 1	438
August	1st to 10th	Night	13% 3 18% 44% 21% 1	536
	11th to 20th	Night	15% 3 18% 39% 24% 1	790
	21st to end	Night	15% 4 20% 40% 20% 2	880
September	1st to 10th	Night	15% 5% 25% 35% 18% 2	800
	11th to 20th	Night	16% 3 23% 34% 19% 4	800
	21st to end	Night	22% 5% 25% 32% 15% 2	800
October	1st to 10th	Night	22% 8% 25% 27% 16% 3	800
	11th to 20th	Night	18% 11% 30% 29% 11% 1	800
	21st to end	Night	23% 9% 35% 24% 8%	880
November	1st to 10th	Night	15% 11% 33% 29% 11% 1	820
	11th to 20th	Night	21% 15% 33% 24% 7%	840
	21st to end	Night	18% 16% 35% 24% 6% 1	840
December	1st to 10th	Night	23% 14% 33% 24% 5% 1	840
	11th to 20th	Night	24% 14% 36% 24% 3	840
	21st to end	Night	23% 13% 37% 24% 3	924

Page generated at 2026-03-15 02:23:56. Version ac07

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