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 2025-07-06.

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	16% 11% 4 8% 5% 5% 5% 4 5% 7% 32%	120231
	Night	15% 11% 4 8% 5% 4 4 3 5% 6% 33%	118579
Transparency	Day	50% 5% 10% 21% 12% 1	123921
	Night	50% 4 10% 21% 13% 2	123026
Seeing	Day	22% 13% 27% 21% 13% 5%	15746
	Night	21% 10% 26% 28% 14% 2	25843

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	15% 21% 7% 18% 8% 4 4 3 4 4 13%	4056
	11th to 20th	Day	14% 21% 8% 14% 6% 8% 5% 3 3 4 15%	4060
	21st to end	Day	20% 18% 8% 10% 8% 6% 5% 3 3 4 14%	4466
February	1st to 10th	Day	21% 15% 5% 10% 7% 4 3 3 4 4 24%	1800
	11th to 20th	Day	17% 13% 7% 12% 6% 4 3 2 5% 6% 25%	1892
	21st to end	Day	18% 15% 5% 9% 5% 4 3 3 4 6% 28%	1650
March	1st to 10th	Day	17% 14% 6% 10% 6% 4 4 3 4 5% 28%	4749
	11th to 20th	Day	12% 9% 3 8% 5% 5% 5% 3 5% 6% 40%	4980
	21st to end	Day	19% 10% 3 8% 5% 4 5% 4 5% 6% 31%	5465
April	1st to 10th	Day	16% 13% 3 8% 5% 4 5% 3 5% 6% 32%	2209
	11th to 20th	Day	17% 11% 3 7% 4 4 5% 3 5% 6% 36%	2552
	21st to end	Day	18% 8% 3 7% 6% 5% 4 5% 5% 7% 34%	2600
May	1st to 10th	Day	22% 10% 3 8% 5% 6% 5% 4 5% 5% 27%	5862
	11th to 20th	Day	20% 9% 3 7% 4 4 4 4 6% 7% 31%	5861
	21st to end	Day	17% 7% 3 7% 5% 4 5% 5% 7% 8% 33%	6433
June	1st to 10th	Day	12% 7% 3 7% 5% 6% 5% 4 7% 9% 37%	2600
	11th to 20th	Day	12% 7% 3 7% 5% 5% 5% 4 7% 9% 35%	2600
	21st to end	Day	12% 7% 2 5% 5% 5% 6% 5% 7% 10% 36%	2600
July	1st to 10th	Day	11% 7% 3 7% 5% 6% 5% 4 6% 9% 38%	4185
	11th to 20th	Day	8% 5% 2 5% 5% 4 5% 5% 7% 11% 42%	4120
	21st to end	Day	12% 6% 3 7% 5% 5% 6% 5% 7% 9% 35%	4466
August	1st to 10th	Day	10% 6% 3 7% 5% 5% 6% 4 7% 10% 37%	4104
	11th to 20th	Day	9% 6% 3 7% 5% 5% 6% 5% 8% 10% 35%	4044
	21st to end	Day	6% 4 2 5% 5% 6% 7% 4 7% 10% 45%	4501
September	1st to 10th	Day	14% 5% 2 5% 3 4 4 4 5% 7% 47%	2090
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 5% 9% 48%	2090
	21st to end	Day	19% 7% 3 6% 4 4 4 3 4 6% 41%	2090
October	1st to 10th	Day	14% 7% 2 6% 3 3 4 4 5% 7% 44%	2010
	11th to 20th	Day	15% 8% 2 7% 4 4 5% 3 5% 6% 41%	1900
	21st to end	Day	21% 9% 3 7% 4 3 4 3 5% 5% 35%	2065
November	1st to 10th	Day	12% 7% 3 6% 4 4 4 3 5% 7% 47%	1762
	11th to 20th	Day	17% 13% 4 7% 5% 4 4 4 5% 6% 33%	1800
	21st to end	Day	19% 15% 4 9% 5% 5% 3 3 4 6% 29%	1800
December	1st to 10th	Day	20% 13% 5% 15% 5% 3 4 3 4 4 23%	2930
	11th to 20th	Day	24% 16% 5% 10% 5% 3 3 2 4 5% 21%	3373
	21st to end	Day	23% 23% 5% 11% 5% 4 4 3 4 4 14%	4466
January	1st to 10th	Night	15% 19% 8% 19% 5% 4 4 3 4 4 16%	5889
	11th to 20th	Night	13% 18% 7% 15% 8% 7% 6% 3 4 4 15%	5900
	21st to end	Night	20% 14% 7% 11% 6% 4 3 2 3 5% 24%	6490
February	1st to 10th	Night	20% 15% 3 10% 6% 4 4 3 4 5% 27%	2600
	11th to 20th	Night	19% 13% 4 11% 6% 5% 5% 3 4 6% 25%	2392
	21st to end	Night	20% 14% 5% 11% 4 5% 4 3 3 4 27%	1980
March	1st to 10th	Night	19% 13% 4 6% 4 4 4 3 4 5% 33%	5102
	11th to 20th	Night	11% 8% 4 7% 5% 5% 4 4 5% 8% 41%	4980
	21st to end	Night	18% 9% 3 7% 5% 4 4 3 4 6% 36%	5467
April	1st to 10th	Night	17% 11% 3 6% 4 3 3 4 6% 7% 36%	2200
	11th to 20th	Night	14% 7% 3 7% 5% 5% 4 4 6% 7% 38%	1806
	21st to end	Night	16% 8% 3 6% 4 5% 4 4 5% 8% 38%	1800
May	1st to 10th	Night	25% 10% 3 7% 5% 4 4 4 6% 6% 27%	4033
	11th to 20th	Night	16% 8% 3 6% 4 4 4 4 5% 10% 35%	4032
	21st to end	Night	14% 7% 3 7% 5% 4 4 4 6% 9% 37%	4421
June	1st to 10th	Night	9% 5% 2 7% 5% 4 4 4 7% 8% 46%	1800
	11th to 20th	Night	10% 6% 2 6% 4 4 4 4 7% 9% 44%	1800
	21st to end	Night	9% 5% 2 6% 4 5% 5% 5% 7% 10% 43%	1800
July	1st to 10th	Night	11% 6% 3 6% 4 4 5% 4 6% 8% 45%	2885
	11th to 20th	Night	8% 5% 2 5% 5% 5% 4 5% 6% 9% 46%	2840
	21st to end	Night	7% 7% 3 7% 5% 6% 6% 5% 6% 8% 39%	3087
August	1st to 10th	Night	8% 7% 3 8% 6% 6% 6% 4 7% 9% 37%	2825
	11th to 20th	Night	10% 8% 4 8% 4 4 3 3 4 7% 45%	2785
	21st to end	Night	5% 3 2 5% 4 5% 5% 5% 8% 9% 49%	3124
September	1st to 10th	Night	12% 5% 1 4 3 4 4 3 4 7% 52%	2083
	11th to 20th	Night	8% 4 1 5% 4 3 3 3 5% 7% 56%	2090
	21st to end	Night	16% 6% 2 5% 4 4 4 4 4 6% 45%	2090
October	1st to 10th	Night	10% 6% 2 6% 4 3 4 3 5% 8% 49%	2168
	11th to 20th	Night	15% 7% 3 7% 4 4 4 3 5% 8% 41%	2280
	21st to end	Night	21% 7% 2 7% 4 4 4 3 4 6% 37%	2532
November	1st to 10th	Night	14% 8% 2 5% 4 3 3 3 4 6% 47%	2536
	11th to 20th	Night	17% 11% 4 8% 4 4 4 3 5% 6% 35%	2600
	21st to end	Night	20% 13% 4 8% 5% 4 4 3 6% 5% 28%	2600
December	1st to 10th	Night	18% 13% 6% 10% 5% 5% 5% 4 5% 5% 25%	4250
	11th to 20th	Night	19% 18% 8% 10% 4 4 3 3 4 5% 22%	4822
	21st to end	Night	23% 20% 5% 10% 6% 4 4 3 4 5% 16%	6490

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	74% 4 8% 10% 4	4057
	11th to 20th	Day	75% 3 7% 8% 6%	4060
	21st to end	Day	74% 4 8% 9% 5%	4466
February	1st to 10th	Day	64% 4 9% 15% 8%	1800
	11th to 20th	Day	62% 4 8% 17% 9% 1	1902
	21st to end	Day	59% 3 11% 18% 8% 2	1650
March	1st to 10th	Day	59% 4 7% 22% 7% 1	4749
	11th to 20th	Day	44% 4 10% 29% 11% 2	4980
	21st to end	Day	53% 4 9% 22% 11% 1	5465
April	1st to 10th	Day	54% 4 10% 19% 12% 2	2209
	11th to 20th	Day	49% 5% 11% 19% 14% 3	2552
	21st to end	Day	50% 5% 9% 22% 12% 2	2600
May	1st to 10th	Day	57% 6% 9% 17% 9% 2	5897
	11th to 20th	Day	51% 5% 11% 20% 12% 1	5865
	21st to end	Day	45% 7% 12% 22% 12% 3	6447
June	1st to 10th	Day	42% 6% 11% 23% 16% 1	2600
	11th to 20th	Day	43% 6% 14% 21% 14% 1	2600
	21st to end	Day	41% 7% 15% 21% 14% 2	2600
July	1st to 10th	Day	43% 5% 11% 22% 16% 2	4120
	11th to 20th	Day	34% 6% 12% 30% 17% 1	4051
	21st to end	Day	42% 7% 12% 17% 18% 3	4324
August	1st to 10th	Day	40% 8% 15% 26% 12%	4091
	11th to 20th	Day	39% 7% 10% 29% 14%	4083
	21st to end	Day	33% 8% 14% 31% 12% 3	4501
September	1st to 10th	Day	37% 5% 11% 22% 22% 3	2090
	11th to 20th	Day	34% 4 12% 26% 21% 3	2090
	21st to end	Day	45% 3 8% 23% 19% 1	2090
October	1st to 10th	Day	26% 4 10% 34% 25% 1	3335
	11th to 20th	Day	36% 4 12% 25% 18% 4	3140
	21st to end	Day	39% 3 12% 26% 18% 2	3379
November	1st to 10th	Day	37% 4 10% 28% 18% 3	1762
	11th to 20th	Day	53% 4 9% 21% 12% 3	1800
	21st to end	Day	58% 4 10% 18% 9% 1	1800
December	1st to 10th	Day	65% 3 14% 14% 4	2930
	11th to 20th	Day	67% 4 10% 14% 5%	3370
	21st to end	Day	74% 4 8% 10% 4	4466
January	1st to 10th	Night	73% 3 7% 13% 3	5889
	11th to 20th	Night	74% 3 9% 9% 5%	5900
	21st to end	Night	65% 2 11% 14% 6% 2	6490
February	1st to 10th	Night	61% 4 10% 18% 8% 1	2600
	11th to 20th	Night	61% 4 9% 16% 9% 1	2393
	21st to end	Night	62% 3 9% 15% 9% 2	1980
March	1st to 10th	Night	53% 4 8% 25% 10% 2	5102
	11th to 20th	Night	41% 5% 10% 32% 11% 1	4980
	21st to end	Night	50% 4 8% 22% 15% 2	5467
April	1st to 10th	Night	47% 4 11% 21% 14% 2	2200
	11th to 20th	Night	44% 4 12% 18% 19% 3	1806
	21st to end	Night	44% 5% 12% 21% 16% 2	1800
May	1st to 10th	Night	57% 7% 9% 15% 8% 4	4060
	11th to 20th	Night	46% 5% 10% 25% 13% 1	4033
	21st to end	Night	42% 7% 13% 26% 10% 2	4429
June	1st to 10th	Night	35% 7% 12% 24% 20% 2	1800
	11th to 20th	Night	35% 7% 14% 24% 18% 3	1800
	21st to end	Night	34% 7% 14% 25% 17% 3	1800
July	1st to 10th	Night	36% 6% 13% 22% 18% 5%	2840
	11th to 20th	Night	34% 6% 13% 30% 16% 1	2786
	21st to end	Night	39% 8% 13% 20% 17% 3	2988
August	1st to 10th	Night	41% 7% 14% 24% 13% 1	2814
	11th to 20th	Night	40% 5% 8% 25% 21% 1	2812
	21st to end	Night	27% 7% 15% 31% 17% 3	3124
September	1st to 10th	Night	33% 4 11% 24% 22% 6%	2083
	11th to 20th	Night	29% 4 11% 27% 26% 3	2090
	21st to end	Night	40% 4 10% 21% 23% 1	2090
October	1st to 10th	Night	29% 3 6% 30% 30% 2	3623
	11th to 20th	Night	31% 3 12% 28% 21% 5%	3779
	21st to end	Night	34% 3 9% 27% 24% 4	4168
November	1st to 10th	Night	39% 3 12% 24% 19% 3	2536
	11th to 20th	Night	51% 3 8% 21% 15% 2	2600
	21st to end	Night	58% 3 11% 20% 7% 1	2600
December	1st to 10th	Night	61% 4 11% 18% 5%	4250
	11th to 20th	Night	65% 4 13% 14% 4	4824
	21st to end	Night	71% 4 9% 12% 4	6490

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	30% 23% 32% 9% 5%	300
	11th to 20th	Day	33% 21% 36% 8% 2	300
	21st to end	Day	33% 23% 30% 11% 3	330
February	1st to 10th	Day	31% 26% 29% 12% 2	300
	11th to 20th	Day	35% 28% 27% 8% 2 1	300
	21st to end	Day	30% 26% 39% 5% 1	249
March	1st to 10th	Day	27% 23% 30% 16% 4	413
	11th to 20th	Day	30% 17% 33% 13% 6%	500
	21st to end	Day	32% 17% 29% 17% 4	550
April	1st to 10th	Day	28% 16% 31% 16% 7% 2	500
	11th to 20th	Day	27% 17% 28% 16% 9% 4	492
	21st to end	Day	26% 14% 34% 17% 6% 2	500
May	1st to 10th	Day	29% 16% 27% 17% 7% 4	503
	11th to 20th	Day	23% 10% 27% 24% 10% 5%	527
	21st to end	Day	15% 11% 26% 24% 18% 7%	573
June	1st to 10th	Day	13% 8% 28% 29% 15% 6%	530
	11th to 20th	Day	15% 10% 23% 29% 17% 6%	530
	21st to end	Day	14% 7% 25% 30% 18% 7%	530
July	1st to 10th	Day	15% 5% 16% 26% 20% 19%	505
	11th to 20th	Day	12% 5% 21% 27% 24% 11%	484
	21st to end	Day	14% 5% 21% 27% 20% 12%	532
August	1st to 10th	Day	12% 4 18% 27% 25% 14%	486
	11th to 20th	Day	13% 5% 23% 28% 20% 10%	479
	21st to end	Day	8% 4 17% 27% 30% 13%	539
September	1st to 10th	Day	14% 5% 18% 25% 25% 12%	490
	11th to 20th	Day	10% 3 17% 25% 31% 13%	490
	21st to end	Day	25% 9% 18% 26% 17% 6%	490
October	1st to 10th	Day	12% 8% 29% 27% 19% 5%	490
	11th to 20th	Day	18% 14% 30% 23% 11% 3	490
	21st to end	Day	28% 13% 29% 19% 10% 1	514
November	1st to 10th	Day	19% 16% 34% 20% 9% 2	300
	11th to 20th	Day	28% 18% 30% 16% 7% 1	300
	21st to end	Day	27% 23% 34% 14% 2	300
December	1st to 10th	Day	30% 22% 30% 13% 4 1	300
	11th to 20th	Day	30% 24% 32% 11% 2 1	300
	21st to end	Day	36% 17% 31% 14% 3	330
January	1st to 10th	Night	26% 20% 34% 17% 3	800
	11th to 20th	Night	30% 16% 34% 18% 3	800
	21st to end	Night	28% 18% 31% 21% 2	880
February	1st to 10th	Night	29% 14% 31% 23% 2	800
	11th to 20th	Night	29% 17% 33% 19% 2	783
	21st to end	Night	28% 14% 38% 18% 2	660
March	1st to 10th	Night	24% 15% 32% 26% 5%	800
	11th to 20th	Night	23% 15% 32% 22% 7%	800
	21st to end	Night	26% 11% 33% 22% 7% 1	880
April	1st to 10th	Night	23% 14% 34% 22% 7%	800
	11th to 20th	Night	18% 12% 34% 24% 10% 1	602
	21st to end	Night	21% 7% 37% 28% 8% 1	600
May	1st to 10th	Night	22% 9% 28% 28% 12% 1	600
	11th to 20th	Night	20% 6% 26% 33% 15% 1	591
	21st to end	Night	11% 4 22% 36% 26% 2	650
June	1st to 10th	Night	10% 3 25% 39% 21% 1	600
	11th to 20th	Night	14% 4 18% 40% 22% 2	600
	21st to end	Night	11% 4 24% 36% 23% 3	600
July	1st to 10th	Night	11% 3 14% 38% 27% 7%	570
	11th to 20th	Night	7% 3 15% 35% 35% 4	552
	21st to end	Night	11% 3 13% 37% 34% 3	624
August	1st to 10th	Night	8% 2 12% 40% 33% 4	567
	11th to 20th	Night	11% 3 12% 40% 30% 4	564
	21st to end	Night	9% 1 15% 33% 34% 7%	627
September	1st to 10th	Night	15% 3 15% 34% 28% 6%	757
	11th to 20th	Night	10% 3 13% 36% 34% 4	760
	21st to end	Night	19% 5% 22% 31% 19% 3	760
October	1st to 10th	Night	14% 4 24% 34% 21% 3	760
	11th to 20th	Night	21% 9% 29% 27% 13% 1	760
	21st to end	Night	25% 10% 28% 27% 10%	836
November	1st to 10th	Night	18% 10% 27% 28% 15% 1	780
	11th to 20th	Night	24% 15% 29% 25% 8% 1	800
	21st to end	Night	27% 14% 27% 26% 6% 1	800
December	1st to 10th	Night	31% 16% 29% 20% 5%	800
	11th to 20th	Night	26% 16% 30% 23% 4	800
	21st to end	Night	33% 13% 27% 24% 2	880

Page generated at 2025-07-03 01:30:14. Version ac07

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