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 2026-10-29.

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% 10% 4 8% 5% 5% 5% 4 6% 7% 32%	149409
	Night	15% 11% 4 9% 5% 5% 4 3 5% 7% 33%	142675
Transparency	Day	50% 5% 11% 21% 12% 1	153057
	Night	50% 5% 11% 21% 13% 2	147099
Seeing	Day	22% 13% 26% 21% 13% 5%	17540
	Night	20% 10% 26% 28% 14% 2	27564

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	16% 20% 6% 16% 7% 4 4 3 4 5% 15%	5258
	11th to 20th	Day	12% 19% 8% 16% 8% 7% 5% 3 3 4 16%	5280
	21st to end	Day	19% 16% 7% 11% 9% 6% 5% 3 4 5% 14%	5780
February	1st to 10th	Day	20% 15% 5% 10% 7% 4 3 3 4 5% 24%	1890
	11th to 20th	Day	17% 13% 7% 12% 6% 4 3 2 5% 6% 24%	1989
	21st to end	Day	18% 15% 5% 9% 5% 4 3 3 4 6% 29%	1730
March	1st to 10th	Day	17% 14% 6% 10% 6% 4 4 3 4 5% 28%	4855
	11th to 20th	Day	12% 9% 3 8% 5% 5% 5% 3 5% 6% 40%	5090
	21st to end	Day	19% 10% 3 8% 5% 4 5% 4 5% 6% 31%	5586
April	1st to 10th	Day	16% 13% 3 8% 5% 4 5% 3 5% 6% 32%	2319
	11th to 20th	Day	16% 10% 3 7% 4 4 5% 3 5% 6% 36%	2681
	21st to end	Day	18% 8% 3 7% 6% 5% 4 5% 5% 6% 34%	2730
May	1st to 10th	Day	20% 10% 3 8% 5% 6% 5% 4 5% 5% 28%	7616
	11th to 20th	Day	18% 8% 3 7% 4 4 5% 4 6% 8% 33%	7626
	21st to end	Day	19% 8% 3 7% 4 4 5% 4 6% 7% 33%	8391
June	1st to 10th	Day	12% 7% 3 7% 5% 6% 5% 4 7% 9% 37%	2730
	11th to 20th	Day	12% 7% 3 7% 5% 5% 5% 4 8% 10% 35%	2730
	21st to end	Day	12% 7% 2 6% 5% 5% 6% 5% 7% 10% 36%	2730
July	1st to 10th	Day	9% 7% 3 8% 5% 5% 5% 4 6% 9% 39%	7680
	11th to 20th	Day	10% 7% 2 7% 5% 5% 5% 5% 8% 11% 37%	7680
	21st to end	Day	10% 7% 3 7% 5% 5% 6% 5% 8% 9% 36%	8340
August	1st to 10th	Day	11% 7% 3 8% 5% 5% 6% 4 7% 9% 34%	6014
	11th to 20th	Day	13% 8% 3 8% 5% 5% 6% 5% 7% 9% 30%	5951
	21st to end	Day	5% 4 2 5% 5% 5% 6% 4 7% 10% 47%	6548
September	1st to 10th	Day	13% 5% 2 5% 4 4 4 4 5% 7% 47%	2310
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 4 5% 8% 48%	2310
	21st to end	Day	19% 7% 3 6% 4 4 4 3 4 6% 41%	2310
October	1st to 10th	Day	13% 6% 2 6% 3 3 4 4 5% 7% 46%	2222
	11th to 20th	Day	15% 7% 2 7% 4 4 4 3 5% 6% 42%	2100
	21st to end	Day	21% 9% 3 7% 4 3 4 3 5% 5% 37%	2253
November	1st to 10th	Day	12% 8% 3 6% 4 4 4 3 5% 7% 46%	1852
	11th to 20th	Day	17% 12% 4 7% 4 4 4 3 5% 6% 33%	1890
	21st to end	Day	19% 15% 4 9% 5% 4 3 3 4 6% 28%	1890
December	1st to 10th	Day	20% 14% 5% 15% 5% 4 4 3 4 4 23%	3020
	11th to 20th	Day	24% 16% 5% 10% 5% 4 3 2 4 5% 21%	3463
	21st to end	Day	23% 23% 5% 11% 5% 4 4 3 4 4 14%	4565
January	1st to 10th	Night	15% 18% 7% 18% 6% 5% 4 3 4 4 16%	7635
	11th to 20th	Night	11% 17% 8% 15% 8% 7% 6% 3 4 4 16%	7680
	21st to end	Night	17% 14% 6% 10% 6% 5% 4 3 4 6% 25%	8401
February	1st to 10th	Night	19% 14% 4 10% 6% 4 4 3 4 4 27%	2730
	11th to 20th	Night	19% 13% 4 11% 6% 5% 5% 3 4 6% 25%	2515
	21st to end	Night	19% 14% 5% 11% 4 5% 4 3 3 4 27%	2076
March	1st to 10th	Night	19% 13% 4 6% 4 4 4 3 4 5% 33%	5216
	11th to 20th	Night	12% 8% 4 7% 5% 5% 4 4 5% 8% 41%	5090
	21st to end	Night	18% 9% 3 7% 5% 4 4 3 4 6% 36%	5588
April	1st to 10th	Night	17% 11% 3 6% 4 3 3 4 5% 7% 36%	2310
	11th to 20th	Night	14% 7% 3 7% 5% 5% 5% 4 6% 7% 37%	1897
	21st to end	Night	16% 8% 3 6% 4 5% 4 4 5% 7% 38%	1890
May	1st to 10th	Night	23% 9% 3 7% 5% 5% 4 4 6% 6% 28%	5237
	11th to 20th	Night	15% 8% 3 7% 4 4 4 4 5% 9% 37%	5234
	21st to end	Night	17% 8% 2 7% 5% 4 4 4 6% 8% 36%	5761
June	1st to 10th	Night	9% 5% 2 7% 5% 4 4 4 7% 8% 46%	1890
	11th to 20th	Night	10% 6% 2 6% 4 4 4 4 7% 9% 44%	1890
	21st to end	Night	10% 6% 2 6% 4 5% 4 5% 7% 9% 42%	1890
July	1st to 10th	Night	9% 6% 3 7% 5% 5% 5% 4 6% 8% 42%	5278
	11th to 20th	Night	10% 7% 2 7% 6% 5% 4 4 6% 9% 39%	5277
	21st to end	Night	7% 6% 3 7% 5% 5% 5% 5% 7% 8% 42%	5736
August	1st to 10th	Night	11% 9% 3 9% 6% 6% 6% 4 6% 7% 33%	4135
	11th to 20th	Night	14% 9% 4 8% 4 5% 4 3 5% 7% 38%	4095
	21st to end	Night	4 3 2 5% 4 5% 5% 5% 8% 9% 50%	4532
September	1st to 10th	Night	11% 5% 1 4 3 4 4 3 4 7% 52%	2303
	11th to 20th	Night	8% 4 2 5% 4 3 3 3 5% 7% 56%	2310
	21st to end	Night	17% 6% 2 5% 4 3 4 3 5% 6% 44%	2310
October	1st to 10th	Night	9% 6% 2 5% 4 3 4 3 5% 7% 50%	2396
	11th to 20th	Night	15% 7% 3 6% 4 4 3 3 5% 7% 43%	2520
	21st to end	Night	20% 6% 2 7% 4 4 4 3 5% 6% 39%	2762
November	1st to 10th	Night	13% 8% 2 5% 4 3 3 3 4 6% 47%	2666
	11th to 20th	Night	17% 10% 4 7% 4 4 4 3 5% 6% 35%	2730
	21st to end	Night	20% 13% 5% 8% 5% 4 4 3 6% 5% 28%	2730
December	1st to 10th	Night	18% 13% 6% 11% 5% 5% 5% 4 5% 5% 25%	4380
	11th to 20th	Night	19% 18% 8% 10% 5% 4 3 3 4 5% 22%	4952
	21st to end	Night	23% 20% 5% 10% 6% 4 4 3 4 5% 17%	6633

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	72% 3 12% 10% 3	5259
	11th to 20th	Day	74% 3 8% 7% 8% 1	5280
	21st to end	Day	72% 4 8% 10% 5%	5780
February	1st to 10th	Day	63% 4 9% 16% 8%	1890
	11th to 20th	Day	62% 4 8% 17% 9% 1	1999
	21st to end	Day	58% 3 11% 19% 7% 2	1730
March	1st to 10th	Day	59% 4 7% 22% 7% 1	4855
	11th to 20th	Day	45% 4 10% 29% 10% 2	5090
	21st to end	Day	53% 4 9% 22% 11% 1	5586
April	1st to 10th	Day	53% 4 11% 19% 12% 2	2319
	11th to 20th	Day	48% 5% 11% 19% 14% 3	2681
	21st to end	Day	49% 5% 10% 23% 12% 2	2730
May	1st to 10th	Day	55% 6% 10% 20% 8% 2	7651
	11th to 20th	Day	48% 5% 12% 22% 12%	7630
	21st to end	Day	47% 6% 10% 18% 14% 5%	8405
June	1st to 10th	Day	42% 6% 11% 23% 16% 1	2730
	11th to 20th	Day	42% 6% 14% 22% 14% 1	2730
	21st to end	Day	42% 7% 15% 21% 14% 2	2730
July	1st to 10th	Day	40% 6% 12% 27% 13% 1	7615
	11th to 20th	Day	39% 7% 12% 30% 12%	7611
	21st to end	Day	41% 6% 12% 21% 18% 2	8156
August	1st to 10th	Day	45% 7% 13% 20% 13% 2	6001
	11th to 20th	Day	47% 8% 11% 24% 10%	5990
	21st to end	Day	30% 7% 16% 33% 12% 2	6548
September	1st to 10th	Day	36% 5% 11% 23% 22% 3	2310
	11th to 20th	Day	35% 4 11% 26% 21% 3	2310
	21st to end	Day	45% 3 8% 22% 20% 1	2310
October	1st to 10th	Day	26% 4 9% 34% 25% 1	3547
	11th to 20th	Day	36% 4 12% 25% 19% 4	3340
	21st to end	Day	39% 3 12% 26% 18% 2	3567
November	1st to 10th	Day	38% 5% 10% 27% 17% 2	1852
	11th to 20th	Day	52% 4 9% 21% 11% 3	1890
	21st to end	Day	58% 4 10% 18% 9% 1	1890
December	1st to 10th	Day	66% 3 13% 14% 4	3020
	11th to 20th	Day	67% 4 10% 15% 5%	3460
	21st to end	Day	74% 4 8% 9% 4	4565
January	1st to 10th	Night	73% 4 8% 12% 3	7636
	11th to 20th	Night	71% 3 9% 10% 6% 1	7680
	21st to end	Night	62% 3 12% 16% 6% 1	8401
February	1st to 10th	Night	60% 4 10% 18% 8% 1	2730
	11th to 20th	Night	61% 4 9% 16% 9% 1	2516
	21st to end	Night	62% 3 10% 15% 9% 2	2076
March	1st to 10th	Night	53% 4 8% 24% 10% 2	5216
	11th to 20th	Night	41% 5% 10% 32% 11% 1	5090
	21st to end	Night	50% 4 8% 22% 14% 2	5588
April	1st to 10th	Night	48% 4 11% 21% 14% 2	2310
	11th to 20th	Night	44% 4 13% 17% 18% 3	1897
	21st to end	Night	45% 5% 11% 21% 16% 2	1890
May	1st to 10th	Night	54% 7% 10% 18% 8% 3	5264
	11th to 20th	Night	45% 5% 10% 26% 13% 1	5235
	21st to end	Night	45% 6% 12% 21% 12% 4	5771
June	1st to 10th	Night	35% 7% 12% 24% 21% 2	1890
	11th to 20th	Night	35% 7% 15% 24% 18% 2	1890
	21st to end	Night	35% 7% 14% 24% 17% 3	1890
July	1st to 10th	Night	39% 6% 12% 23% 17% 3	5235
	11th to 20th	Night	40% 7% 12% 29% 12% 1	5226
	21st to end	Night	36% 7% 12% 22% 21% 2	5606
August	1st to 10th	Night	48% 6% 12% 19% 13% 2	4124
	11th to 20th	Night	47% 6% 10% 21% 16% 1	4122
	21st to end	Night	25% 7% 17% 32% 16% 2	4532
September	1st to 10th	Night	32% 4 12% 24% 22% 6%	2303
	11th to 20th	Night	28% 5% 11% 28% 25% 3	2310
	21st to end	Night	41% 4 10% 21% 23% 2	2310
October	1st to 10th	Night	28% 3 6% 30% 30% 2	3851
	11th to 20th	Night	31% 3 11% 28% 22% 5%	4019
	21st to end	Night	34% 3 8% 27% 24% 4	4398
November	1st to 10th	Night	38% 3 12% 25% 19% 3	2666
	11th to 20th	Night	51% 3 8% 21% 14% 2	2730
	21st to end	Night	58% 3 10% 20% 7% 1	2730
December	1st to 10th	Night	61% 4 11% 18% 5%	4380
	11th to 20th	Night	65% 4 13% 14% 4	4954
	21st to end	Night	71% 4 9% 12% 4	6633

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% 22% 32% 8% 5%	330
	11th to 20th	Day	36% 21% 34% 7% 2	330
	21st to end	Day	35% 22% 29% 10% 3	363
February	1st to 10th	Day	30% 25% 29% 14% 2	330
	11th to 20th	Day	35% 28% 27% 8% 2 1	330
	21st to end	Day	29% 26% 38% 5% 1	273
March	1st to 10th	Day	28% 23% 30% 15% 4	449
	11th to 20th	Day	31% 17% 33% 13% 6%	540
	21st to end	Day	31% 18% 30% 17% 4	594
April	1st to 10th	Day	27% 16% 32% 16% 7% 2	540
	11th to 20th	Day	27% 18% 28% 16% 8% 3	532
	21st to end	Day	25% 14% 34% 17% 7% 2	540
May	1st to 10th	Day	30% 17% 27% 15% 7% 3	543
	11th to 20th	Day	23% 11% 28% 23% 10% 5%	567
	21st to end	Day	17% 10% 26% 24% 17% 6%	617
June	1st to 10th	Day	13% 8% 28% 29% 15% 7%	570
	11th to 20th	Day	16% 11% 24% 27% 16% 6%	570
	21st to end	Day	14% 8% 25% 29% 18% 7%	570
July	1st to 10th	Day	14% 5% 16% 28% 20% 18%	565
	11th to 20th	Day	13% 5% 21% 27% 24% 11%	564
	21st to end	Day	13% 6% 21% 28% 20% 12%	620
August	1st to 10th	Day	11% 5% 19% 28% 24% 13%	566
	11th to 20th	Day	13% 6% 23% 28% 20% 10%	559
	21st to end	Day	8% 5% 18% 29% 29% 12%	627
September	1st to 10th	Day	14% 5% 18% 27% 24% 12%	570
	11th to 20th	Day	10% 3 17% 26% 32% 13%	570
	21st to end	Day	24% 8% 19% 25% 18% 6%	570
October	1st to 10th	Day	12% 8% 28% 28% 19% 5%	570
	11th to 20th	Day	18% 13% 30% 23% 12% 3	570
	21st to end	Day	26% 13% 30% 19% 10% 2	588
November	1st to 10th	Day	21% 15% 34% 20% 8% 2	330
	11th to 20th	Day	30% 18% 30% 15% 7% 1	330
	21st to end	Day	29% 22% 33% 15% 2	330
December	1st to 10th	Day	29% 23% 31% 13% 3 1	330
	11th to 20th	Day	32% 24% 31% 11% 2 1	330
	21st to end	Day	37% 18% 31% 12% 2	363
January	1st to 10th	Night	27% 19% 33% 17% 3	840
	11th to 20th	Night	30% 18% 33% 17% 3	840
	21st to end	Night	28% 18% 31% 21% 2	924
February	1st to 10th	Night	28% 13% 32% 24% 3	840
	11th to 20th	Night	28% 18% 33% 19% 2	823
	21st to end	Night	28% 14% 38% 18% 2	692
March	1st to 10th	Night	24% 15% 31% 25% 4	840
	11th to 20th	Night	24% 15% 32% 22% 7%	840
	21st to end	Night	26% 12% 33% 22% 6% 1	924
April	1st to 10th	Night	23% 15% 34% 22% 6%	840
	11th to 20th	Night	18% 14% 34% 24% 10% 1	632
	21st to end	Night	21% 7% 36% 27% 7% 1	630
May	1st to 10th	Night	22% 10% 28% 27% 12% 1	630
	11th to 20th	Night	19% 6% 26% 33% 14% 1	621
	21st to end	Night	12% 4 22% 36% 24% 2	683
June	1st to 10th	Night	11% 3 25% 39% 21% 1	630
	11th to 20th	Night	14% 5% 19% 40% 21% 2	630
	21st to end	Night	11% 5% 23% 35% 23% 3	630
July	1st to 10th	Night	10% 3 14% 37% 29% 7%	615
	11th to 20th	Night	8% 3 15% 36% 34% 4	612
	21st to end	Night	10% 3 13% 37% 34% 3	690
August	1st to 10th	Night	8% 3 13% 39% 33% 4	627
	11th to 20th	Night	11% 3 12% 40% 30% 4	624
	21st to end	Night	9% 2 15% 34% 34% 6%	693
September	1st to 10th	Night	14% 3 14% 36% 27% 5%	837
	11th to 20th	Night	9% 3 13% 36% 34% 4	840
	21st to end	Night	20% 5% 22% 31% 20% 3	840
October	1st to 10th	Night	13% 5% 24% 34% 22% 3	840
	11th to 20th	Night	21% 9% 28% 27% 14% 1	840
	21st to end	Night	23% 10% 28% 27% 11%	913
November	1st to 10th	Night	19% 10% 28% 28% 14% 1	820
	11th to 20th	Night	24% 15% 28% 24% 7% 1	840
	21st to end	Night	28% 14% 27% 25% 6%	840
December	1st to 10th	Night	30% 16% 29% 20% 4	840
	11th to 20th	Night	26% 16% 31% 22% 4	840
	21st to end	Night	33% 14% 28% 23% 2	924

Page generated at 2026-10-26 04:37:46. Version ac07

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