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 2024-03-18.

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	16% 10% 4 7% 6% 3 5% 5% 5% 7% 32%	79025
	Night	16% 10% 4 7% 5% 3 4 4 5% 7% 34%	80778
Transparency	Day	52% 5% 11% 19% 11% 1	78748
	Night	51% 5% 11% 20% 12% 2	80574
Seeing	Day	22% 12% 26% 21% 13% 6%	13973
	Night	20% 10% 26% 28% 14% 2	24176

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	19% 19% 6% 11% 7% 3 4 4 4 6% 18%	2836
	11th to 20th	Day	15% 19% 9% 11% 7% 6% 7% 3 3 4 15%	2840
	21st to end	Day	26% 21% 10% 9% 6% 4 3 3 3 3 12%	3124
February	1st to 10th	Day	21% 14% 5% 9% 8% 3 4 4 4 4 25%	1710
	11th to 20th	Day	16% 12% 7% 11% 7% 3 4 3 5% 6% 25%	1794
	21st to end	Day	19% 14% 6% 8% 6% 3 3 3 3 6% 29%	1570
March	1st to 10th	Day	18% 11% 5% 7% 6% 3 4 4 5% 6% 31%	2007
	11th to 20th	Day	18% 13% 4 7% 5% 4 3 4 5% 6% 31%	2058
	21st to end	Day	22% 10% 4 7% 6% 3 4 5% 4 7% 28%	2178
April	1st to 10th	Day	16% 12% 3 7% 6% 3 4 4 5% 6% 34%	1987
	11th to 20th	Day	18% 9% 3 6% 5% 3 5% 4 5% 6% 35%	2294
	21st to end	Day	20% 7% 3 6% 7% 4 5% 5% 4 6% 32%	2340
May	1st to 10th	Day	20% 8% 3 6% 6% 4 5% 5% 6% 7% 31%	2340
	11th to 20th	Day	21% 7% 3 6% 5% 3 5% 5% 5% 7% 32%	2301
	21st to end	Day	10% 5% 3 5% 7% 3 6% 6% 7% 10% 37%	2531
June	1st to 10th	Day	12% 6% 3 6% 5% 4 6% 6% 7% 8% 37%	2340
	11th to 20th	Day	13% 6% 3 5% 6% 4 5% 5% 7% 10% 35%	2340
	21st to end	Day	13% 6% 3 4 5% 4 6% 6% 7% 10% 36%	2340
July	1st to 10th	Day	13% 6% 3 5% 6% 4 5% 6% 6% 9% 37%	2340
	11th to 20th	Day	11% 6% 3 5% 6% 3 4 6% 6% 9% 41%	2340
	21st to end	Day	12% 5% 2 5% 6% 4 6% 6% 7% 10% 37%	2547
August	1st to 10th	Day	9% 5% 2 6% 6% 4 6% 6% 7% 10% 38%	2327
	11th to 20th	Day	10% 5% 3 6% 6% 4 6% 7% 8% 11% 34%	2303
	21st to end	Day	9% 5% 2 4 6% 4 6% 5% 7% 10% 43%	2557
September	1st to 10th	Day	15% 5% 2 4 4 3 4 5% 5% 7% 45%	1980
	11th to 20th	Day	10% 4 2 6% 4 3 5% 5% 5% 8% 47%	1980
	21st to end	Day	17% 6% 3 5% 4 3 4 4 4 6% 43%	1980
October	1st to 10th	Day	14% 7% 3 6% 4 2 4 6% 5% 8% 42%	1905
	11th to 20th	Day	16% 8% 2 7% 5% 3 4 5% 5% 6% 40%	1800
	21st to end	Day	22% 9% 4 6% 5% 3 4 4 5% 5% 34%	1957
November	1st to 10th	Day	11% 7% 3 5% 4 4 4 4 5% 6% 47%	1672
	11th to 20th	Day	18% 12% 4 7% 5% 2 4 4 4 6% 34%	1710
	21st to end	Day	19% 12% 4 7% 6% 3 4 4 5% 6% 30%	1710
December	1st to 10th	Day	21% 17% 8% 9% 6% 2 4 4 5% 4 20%	1710
	11th to 20th	Day	20% 16% 5% 10% 7% 3 4 4 5% 5% 22%	2153
	21st to end	Day	22% 24% 5% 10% 6% 4 4 4 4 5% 12%	3124
January	1st to 10th	Night	16% 19% 8% 11% 6% 4 5% 4 3 4 19%	4109
	11th to 20th	Night	15% 17% 7% 15% 6% 4 6% 5% 4 4 16%	4120
	21st to end	Night	26% 18% 9% 10% 7% 2 3 2 2 4 16%	4532
February	1st to 10th	Night	21% 14% 4 9% 6% 3 4 4 4 5% 28%	2470
	11th to 20th	Night	18% 12% 4 9% 6% 4 5% 5% 4 6% 26%	2270
	21st to end	Night	20% 13% 6% 10% 6% 4 4 4 3 4 27%	1884
March	1st to 10th	Night	17% 10% 4 7% 6% 3 5% 4 4 6% 34%	2171
	11th to 20th	Night	16% 10% 4 6% 6% 3 4 4 5% 7% 37%	2068
	21st to end	Night	20% 9% 4 6% 6% 3 4 4 4 6% 34%	2178
April	1st to 10th	Night	16% 9% 4 5% 4 2 3 5% 5% 8% 38%	1980
	11th to 20th	Night	15% 6% 4 6% 5% 4 4 5% 6% 7% 38%	1624
	21st to end	Night	17% 7% 3 6% 5% 3 5% 4 5% 8% 37%	1620
May	1st to 10th	Night	18% 7% 3 6% 7% 3 4 5% 7% 7% 33%	1620
	11th to 20th	Night	17% 8% 4 6% 5% 3 5% 4 5% 8% 36%	1592
	21st to end	Night	8% 5% 2 6% 5% 3 4 6% 7% 10% 43%	1744
June	1st to 10th	Night	8% 4 2 6% 6% 3 5% 5% 7% 8% 46%	1620
	11th to 20th	Night	10% 5% 2 4 5% 3 4 5% 7% 10% 45%	1620
	21st to end	Night	10% 4 3 5% 4 3 5% 6% 7% 10% 44%	1620
July	1st to 10th	Night	9% 4 2 5% 5% 3 5% 5% 6% 8% 47%	1620
	11th to 20th	Night	7% 4 1 5% 5% 3 5% 5% 6% 10% 48%	1620
	21st to end	Night	8% 6% 3 5% 5% 4 6% 6% 6% 8% 42%	1771
August	1st to 10th	Night	5% 4 2 5% 5% 4 6% 5% 8% 9% 45%	1611
	11th to 20th	Night	8% 5% 3 7% 5% 3 4 6% 5% 9% 46%	1598
	21st to end	Night	8% 3 2 4 5% 2 4 6% 7% 9% 51%	1782
September	1st to 10th	Night	13% 5% 2 3 3 3 4 4 4 7% 51%	1973
	11th to 20th	Night	9% 4 2 5% 4 2 3 3 5% 7% 56%	1980
	21st to end	Night	14% 6% 2 4 5% 3 4 4 4 6% 47%	1980
October	1st to 10th	Night	10% 6% 2 5% 5% 3 4 4 5% 8% 48%	2053
	11th to 20th	Night	16% 7% 3 6% 5% 3 4 4 5% 8% 39%	2160
	21st to end	Night	22% 7% 3 6% 5% 3 4 4 4 6% 36%	2398
November	1st to 10th	Night	14% 7% 3 5% 4 2 3 4 4 6% 47%	2406
	11th to 20th	Night	17% 9% 4 7% 5% 3 4 4 5% 6% 36%	2470
	21st to end	Night	19% 12% 5% 7% 5% 3 5% 3 6% 6% 29%	2470
December	1st to 10th	Night	23% 14% 6% 9% 5% 3 4 4 4 5% 23%	2470
	11th to 20th	Night	18% 14% 7% 8% 5% 3 4 4 5% 7% 26%	3042
	21st to end	Night	23% 20% 7% 8% 7% 3 4 4 4 5% 16%	4532

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	69% 4 10% 12% 5%	2837
	11th to 20th	Day	75% 4 8% 10% 3	2840
	21st to end	Day	78% 4 7% 8% 3 1	3124
February	1st to 10th	Day	64% 4 9% 14% 9%	1710
	11th to 20th	Day	62% 4 8% 17% 9% 1	1804
	21st to end	Day	60% 4 10% 18% 8% 2	1570
March	1st to 10th	Day	55% 4 10% 23% 7% 1	2007
	11th to 20th	Day	55% 5% 10% 19% 10% 1	2058
	21st to end	Day	57% 4 9% 20% 9% 1	2178
April	1st to 10th	Day	52% 4 11% 20% 12% 2	1987
	11th to 20th	Day	50% 5% 11% 17% 14% 3	2294
	21st to end	Day	52% 4 9% 21% 11% 2	2340
May	1st to 10th	Day	52% 5% 13% 19% 9% 1	2340
	11th to 20th	Day	52% 6% 12% 17% 12% 1	2305
	21st to end	Day	41% 8% 15% 23% 13% 1	2531
June	1st to 10th	Day	43% 6% 11% 23% 16% 1	2340
	11th to 20th	Day	43% 6% 14% 21% 14% 1	2340
	21st to end	Day	42% 7% 15% 21% 14% 2	2340
July	1st to 10th	Day	44% 7% 13% 21% 14% 2	2275
	11th to 20th	Day	39% 6% 12% 25% 15% 1	2271
	21st to end	Day	40% 7% 14% 24% 13% 2	2405
August	1st to 10th	Day	38% 8% 14% 25% 14% 1	2314
	11th to 20th	Day	42% 7% 13% 26% 11% 1	2303
	21st to end	Day	36% 8% 13% 23% 16% 5%	2557
September	1st to 10th	Day	39% 5% 11% 22% 21% 3	1980
	11th to 20th	Day	36% 4 12% 26% 20% 2	1980
	21st to end	Day	43% 3 9% 24% 20% 1	1980
October	1st to 10th	Day	41% 6% 10% 23% 19% 1	1905
	11th to 20th	Day	44% 4 13% 23% 15% 1	1800
	21st to end	Day	53% 4 11% 21% 10% 2	1957
November	1st to 10th	Day	38% 5% 11% 27% 17% 3	1672
	11th to 20th	Day	52% 4 9% 21% 12% 3	1710
	21st to end	Day	56% 4 11% 19% 10% 1	1710
December	1st to 10th	Day	68% 4 10% 14% 4	1710
	11th to 20th	Day	65% 4 8% 17% 6%	2150
	21st to end	Day	76% 4 9% 7% 3	3124
January	1st to 10th	Night	69% 4 8% 14% 4	4109
	11th to 20th	Night	72% 3 10% 12% 3	4120
	21st to end	Night	75% 2 7% 12% 4 1	4532
February	1st to 10th	Night	61% 3 9% 17% 8% 1	2470
	11th to 20th	Night	60% 4 9% 17% 9% 1	2271
	21st to end	Night	63% 3 9% 14% 9% 2	1884
March	1st to 10th	Night	51% 4 8% 23% 12% 1	2171
	11th to 20th	Night	48% 4 10% 26% 10% 2	2068
	21st to end	Night	52% 4 8% 21% 13% 2	2178
April	1st to 10th	Night	46% 4 12% 22% 15% 2	1980
	11th to 20th	Night	44% 4 12% 17% 20% 3	1624
	21st to end	Night	45% 5% 12% 20% 15% 2	1620
May	1st to 10th	Night	49% 8% 11% 19% 10% 3	1620
	11th to 20th	Night	48% 5% 10% 21% 14% 3	1593
	21st to end	Night	35% 8% 17% 25% 13% 2	1745
June	1st to 10th	Night	35% 7% 12% 24% 19% 2	1620
	11th to 20th	Night	34% 7% 15% 24% 17% 3	1620
	21st to end	Night	34% 7% 14% 25% 17% 3	1620
July	1st to 10th	Night	34% 7% 14% 21% 20% 3	1575
	11th to 20th	Night	32% 6% 14% 27% 18% 3	1566
	21st to end	Night	37% 8% 13% 25% 15% 2	1672
August	1st to 10th	Night	32% 8% 15% 27% 17% 1	1600
	11th to 20th	Night	37% 6% 12% 26% 18% 1	1598
	21st to end	Night	28% 6% 14% 28% 19% 4	1782
September	1st to 10th	Night	34% 4 12% 23% 20% 6%	1973
	11th to 20th	Night	29% 5% 11% 27% 26% 3	1980
	21st to end	Night	38% 4 10% 22% 24% 1	1980
October	1st to 10th	Night	35% 5% 9% 27% 21% 2	2053
	11th to 20th	Night	44% 4 10% 25% 16% 1	2160
	21st to end	Night	50% 4 9% 22% 12% 3	2398
November	1st to 10th	Night	39% 4 12% 23% 19% 3	2406
	11th to 20th	Night	50% 3 8% 21% 15% 2	2470
	21st to end	Night	56% 3 11% 21% 8% 1	2470
December	1st to 10th	Night	65% 4 9% 16% 6%	2470
	11th to 20th	Night	59% 5% 11% 20% 6%	3044
	21st to end	Night	71% 4 9% 12% 3	4532

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% 33% 9% 6%	270
	11th to 20th	Day	32% 19% 38% 9% 2	270
	21st to end	Day	34% 21% 30% 11% 3	297
February	1st to 10th	Day	31% 23% 29% 13% 2	270
	11th to 20th	Day	32% 29% 28% 9% 2 1	270
	21st to end	Day	31% 26% 37% 5% 1	225
March	1st to 10th	Day	28% 21% 30% 17% 4	377
	11th to 20th	Day	29% 17% 34% 14% 6%	449
	21st to end	Day	32% 16% 30% 18% 4	462
April	1st to 10th	Day	27% 14% 30% 18% 8% 3	420
	11th to 20th	Day	27% 15% 27% 16% 10% 4	412
	21st to end	Day	28% 14% 35% 15% 6% 3	420
May	1st to 10th	Day	29% 15% 27% 16% 8% 4	423
	11th to 20th	Day	22% 10% 28% 26% 9% 5%	447
	21st to end	Day	13% 8% 25% 26% 19% 8%	485
June	1st to 10th	Day	14% 5% 28% 30% 16% 6%	450
	11th to 20th	Day	15% 10% 23% 28% 17% 7%	450
	21st to end	Day	14% 6% 26% 29% 18% 7%	450
July	1st to 10th	Day	15% 5% 14% 26% 20% 20%	445
	11th to 20th	Day	13% 3 20% 26% 25% 12%	444
	21st to end	Day	13% 5% 20% 28% 20% 13%	488
August	1st to 10th	Day	12% 3 17% 27% 26% 15%	446
	11th to 20th	Day	14% 5% 21% 28% 21% 10%	439
	21st to end	Day	9% 4 18% 27% 29% 13%	495
September	1st to 10th	Day	16% 4 18% 24% 26% 13%	450
	11th to 20th	Day	11% 4 18% 23% 30% 14%	450
	21st to end	Day	22% 9% 18% 27% 18% 6%	450
October	1st to 10th	Day	14% 7% 29% 27% 18% 6%	450
	11th to 20th	Day	19% 14% 31% 24% 11% 2	450
	21st to end	Day	30% 13% 29% 18% 9% 1	472
November	1st to 10th	Day	19% 16% 32% 21% 10% 2	270
	11th to 20th	Day	28% 18% 29% 17% 8% 1	270
	21st to end	Day	26% 21% 35% 16% 2	270
December	1st to 10th	Day	30% 20% 30% 14% 4 1	270
	11th to 20th	Day	28% 24% 33% 12% 2 1	270
	21st to end	Day	35% 16% 32% 14% 3	297
January	1st to 10th	Night	26% 19% 34% 17% 4	760
	11th to 20th	Night	30% 15% 34% 18% 3	760
	21st to end	Night	28% 17% 31% 22% 2	836
February	1st to 10th	Night	29% 13% 31% 24% 3	760
	11th to 20th	Night	28% 17% 34% 19% 2	743
	21st to end	Night	28% 14% 38% 18% 2	628
March	1st to 10th	Night	24% 14% 31% 26% 5%	760
	11th to 20th	Night	23% 15% 31% 23% 7%	752
	21st to end	Night	26% 10% 32% 23% 8% 1	792
April	1st to 10th	Night	21% 13% 35% 23% 8%	720
	11th to 20th	Night	18% 11% 34% 25% 11% 1	542
	21st to end	Night	21% 7% 36% 27% 7% 1	540
May	1st to 10th	Night	21% 9% 30% 26% 13% 1	540
	11th to 20th	Night	20% 5% 27% 33% 14% 1	531
	21st to end	Night	10% 4 21% 35% 28% 3	584
June	1st to 10th	Night	9% 3 24% 41% 22% 1	540
	11th to 20th	Night	14% 4 18% 39% 22% 2	540
	21st to end	Night	12% 4 23% 36% 23% 3	540
July	1st to 10th	Night	11% 2 14% 38% 28% 8%	525
	11th to 20th	Night	7% 2 15% 34% 36% 5%	522
	21st to end	Night	10% 3 13% 36% 35% 3	591
August	1st to 10th	Night	8% 2 11% 41% 34% 5%	537
	11th to 20th	Night	11% 3 11% 40% 31% 5%	534
	21st to end	Night	10% 2 16% 32% 34% 7%	594
September	1st to 10th	Night	16% 3 15% 32% 29% 6%	717
	11th to 20th	Night	11% 3 14% 34% 34% 5%	720
	21st to end	Night	17% 4 23% 32% 20% 4	720
October	1st to 10th	Night	14% 5% 24% 34% 21% 3	720
	11th to 20th	Night	21% 9% 29% 28% 13% 1	720
	21st to end	Night	26% 10% 28% 26% 9%	792
November	1st to 10th	Night	19% 10% 27% 28% 15% 1	740
	11th to 20th	Night	24% 14% 28% 25% 8% 1	760
	21st to end	Night	26% 13% 27% 26% 6% 1	760
December	1st to 10th	Night	31% 15% 29% 20% 4	760
	11th to 20th	Night	25% 16% 31% 23% 4	760
	21st to end	Night	33% 13% 28% 23% 2	836

Page generated at 2024-03-15 14:01:43. Version ac07

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