Metuchen
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Metuchen clear sky chart from 2005-11-06 to 2026-08-30.

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% 7% 2 6% 4 4 4 4 6% 7% 40%	144157
	Night	16% 7% 2 6% 4 4 4 3 5% 6% 42%	138061
Transparency	Day	41% 6% 12% 22% 17% 2	147686
	Night	40% 6% 11% 23% 17% 3	142621
Seeing	Day	20% 15% 30% 22% 10% 3	17341
	Night	20% 13% 32% 27% 8% 1	26456

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	13% 6% 2 5% 4 4 4 4 5% 6% 47%	4661
	11th to 20th	Day	15% 8% 2 6% 3 4 4 3 4 5% 45%	4650
	21st to end	Day	16% 7% 3 6% 4 4 4 3 5% 6% 40%	5678
February	1st to 10th	Day	15% 8% 2 6% 4 4 4 3 4 6% 42%	1890
	11th to 20th	Day	15% 7% 3 6% 5% 4 4 4 4 6% 41%	2046
	21st to end	Day	18% 8% 3 7% 4 4 4 3 6% 5% 38%	1730
March	1st to 10th	Day	21% 7% 2 4 4 3 3 3 5% 6% 43%	4576
	11th to 20th	Day	12% 7% 2 7% 4 4 4 4 6% 8% 42%	4938
	21st to end	Day	18% 6% 2 6% 4 3 4 4 5% 6% 43%	6025
April	1st to 10th	Day	18% 7% 3 6% 4 4 5% 3 5% 7% 38%	2520
	11th to 20th	Day	16% 5% 2 6% 5% 3 4 4 5% 9% 40%	2494
	21st to end	Day	18% 7% 2 5% 4 5% 5% 4 6% 7% 39%	2520
May	1st to 10th	Day	23% 7% 2 6% 4 4 4 3 5% 7% 33%	7634
	11th to 20th	Day	20% 8% 3 6% 4 4 4 3 5% 7% 39%	8198
	21st to end	Day	24% 7% 2 6% 3 4 5% 3 6% 7% 33%	9060
June	1st to 10th	Day	14% 6% 2 6% 5% 4 4 5% 7% 9% 39%	2940
	11th to 20th	Day	14% 7% 2 6% 5% 4 4 4 7% 8% 38%	2940
	21st to end	Day	12% 6% 2 7% 5% 5% 5% 4 7% 8% 39%	2940
July	1st to 10th	Day	12% 6% 3 7% 5% 5% 5% 4 6% 9% 38%	8280
	11th to 20th	Day	8% 7% 3 7% 4 5% 5% 5% 8% 11% 37%	8280
	21st to end	Day	11% 7% 2 7% 5% 4 5% 4 7% 9% 38%	8993
August	1st to 10th	Day	18% 7% 2 7% 5% 5% 5% 4 7% 9% 32%	4383
	11th to 20th	Day	13% 6% 2 5% 4 4 5% 4 6% 8% 41%	3970
	21st to end	Day	10% 5% 2 5% 4 4 4 3 6% 9% 48%	4420
September	1st to 10th	Day	14% 6% 2 5% 5% 4 4 4 5% 6% 45%	2400
	11th to 20th	Day	13% 6% 2 5% 3 3 3 3 5% 8% 49%	2327
	21st to end	Day	19% 6% 3 6% 4 4 4 4 5% 6% 39%	2200
October	1st to 10th	Day	18% 6% 2 5% 4 4 4 4 5% 6% 43%	2069
	11th to 20th	Day	15% 5% 2 5% 4 3 5% 3 5% 7% 47%	2000
	21st to end	Day	18% 5% 2 5% 3 3 3 3 4 7% 46%	2065
November	1st to 10th	Day	13% 6% 2 6% 3 3 2 3 4 6% 51%	1851
	11th to 20th	Day	16% 5% 2 5% 3 3 3 4 5% 6% 47%	1890
	21st to end	Day	16% 7% 2 4 4 3 4 3 5% 8% 44%	1795
December	1st to 10th	Day	15% 7% 3 5% 3 3 3 3 6% 7% 45%	2680
	11th to 20th	Day	21% 7% 2 4 3 3 3 3 4 6% 44%	3066
	21st to end	Day	17% 7% 2 6% 5% 4 5% 4 5% 7% 38%	4048
January	1st to 10th	Night	12% 8% 3 6% 4 3 4 3 5% 6% 47%	8234
	11th to 20th	Night	15% 8% 3 6% 3 3 4 3 5% 6% 46%	8235
	21st to end	Night	16% 9% 2 5% 4 4 4 3 4 6% 44%	8488
February	1st to 10th	Night	15% 10% 2 5% 4 4 3 3 5% 6% 41%	2730
	11th to 20th	Night	17% 8% 3 6% 4 4 4 3 5% 5% 40%	2458
	21st to end	Night	18% 9% 2 5% 4 3 4 4 4 6% 42%	2076
March	1st to 10th	Night	19% 8% 2 5% 4 3 3 2 4 5% 44%	5484
	11th to 20th	Night	13% 9% 3 5% 3 3 4 3 4 6% 47%	5236
	21st to end	Night	18% 8% 3 6% 4 4 4 3 4 5% 40%	5148
April	1st to 10th	Night	19% 7% 3 6% 4 4 5% 3 5% 6% 38%	2100
	11th to 20th	Night	17% 7% 3 7% 4 4 4 3 5% 7% 40%	2075
	21st to end	Night	18% 6% 2 5% 3 4 4 3 5% 7% 43%	2100
May	1st to 10th	Night	22% 8% 3 7% 4 4 4 3 5% 8% 30%	5262
	11th to 20th	Night	20% 8% 2 6% 4 4 4 4 5% 7% 36%	4705
	21st to end	Night	24% 8% 3 7% 3 3 4 4 5% 7% 32%	5114
June	1st to 10th	Night	15% 6% 2 6% 4 3 4 4 7% 8% 42%	1680
	11th to 20th	Night	13% 7% 2 6% 4 5% 5% 3 6% 9% 38%	1680
	21st to end	Night	11% 5% 2 6% 4 5% 5% 4 7% 10% 41%	1680
July	1st to 10th	Night	12% 6% 3 7% 6% 5% 5% 4 6% 9% 39%	4680
	11th to 20th	Night	10% 8% 3 7% 5% 5% 6% 4 7% 10% 35%	4680
	21st to end	Night	13% 7% 2 6% 4 4 4 4 6% 9% 41%	5084
August	1st to 10th	Night	22% 7% 2 6% 4 4 5% 4 6% 8% 32%	2948
	11th to 20th	Night	14% 6% 3 6% 5% 5% 5% 4 6% 7% 39%	3297
	21st to end	Night	10% 5% 2 5% 4 3 5% 3 5% 8% 51%	3677
September	1st to 10th	Night	14% 6% 3 7% 4 4 4 4 5% 6% 45%	2000
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 5% 7% 51%	2072
	21st to end	Night	18% 7% 2 6% 4 4 3 3 4 6% 42%	2200
October	1st to 10th	Night	18% 5% 2 6% 3 3 4 3 5% 6% 44%	2329
	11th to 20th	Night	15% 5% 2 5% 4 3 3 3 4 6% 51%	2400
	21st to end	Night	18% 7% 2 5% 3 3 3 3 5% 6% 46%	2775
November	1st to 10th	Night	11% 5% 2 5% 4 3 4 3 5% 6% 53%	2667
	11th to 20th	Night	17% 6% 2 6% 4 3 3 3 4 5% 48%	2730
	21st to end	Night	14% 6% 2 6% 4 3 4 3 5% 7% 45%	2819
December	1st to 10th	Night	14% 8% 3 6% 3 3 3 3 5% 5% 47%	4720
	11th to 20th	Night	24% 7% 2 4 3 3 3 3 4 5% 43%	5348
	21st to end	Night	19% 9% 3 7% 4 3 4 3 5% 4 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	37% 5% 9% 28% 19% 2	4662
	11th to 20th	Day	40% 4 9% 22% 19% 6%	4680
	21st to end	Day	43% 5% 11% 23% 16% 1	5678
February	1st to 10th	Day	44% 5% 13% 23% 13% 2	1890
	11th to 20th	Day	46% 5% 9% 23% 15% 3	2055
	21st to end	Day	46% 5% 10% 22% 14% 4	1730
March	1st to 10th	Day	41% 5% 10% 21% 15% 7%	4579
	11th to 20th	Day	38% 6% 12% 26% 13% 5%	4938
	21st to end	Day	42% 5% 9% 15% 23% 6%	6025
April	1st to 10th	Day	44% 6% 9% 20% 15% 5%	2520
	11th to 20th	Day	40% 6% 13% 21% 17% 3	2494
	21st to end	Day	42% 7% 10% 20% 17% 4	2520
May	1st to 10th	Day	49% 6% 13% 17% 14% 1	7646
	11th to 20th	Day	45% 6% 10% 23% 15% 1	8202
	21st to end	Day	49% 6% 10% 21% 13% 1	9061
June	1st to 10th	Day	39% 8% 13% 21% 17% 1	2940
	11th to 20th	Day	42% 8% 13% 22% 12% 2	2940
	21st to end	Day	40% 9% 13% 21% 16% 1	2940
July	1st to 10th	Day	42% 9% 13% 19% 17% 1	8210
	11th to 20th	Day	39% 9% 16% 23% 13% 1	8205
	21st to end	Day	38% 8% 11% 21% 21% 1	8795
August	1st to 10th	Day	47% 9% 14% 20% 9% 1	4369
	11th to 20th	Day	38% 8% 14% 26% 13% 1	4006
	21st to end	Day	32% 7% 11% 26% 22% 2	4420
September	1st to 10th	Day	38% 7% 11% 21% 20% 3	2400
	11th to 20th	Day	33% 6% 11% 24% 23% 3	2327
	21st to end	Day	46% 7% 9% 17% 19% 3	2200
October	1st to 10th	Day	35% 7% 11% 17% 25% 5%	3368
	11th to 20th	Day	25% 4 11% 24% 30% 6%	3240
	21st to end	Day	26% 4 14% 25% 27% 4	3316
November	1st to 10th	Day	34% 4 13% 24% 22% 3	1851
	11th to 20th	Day	38% 5% 9% 24% 21% 3	1890
	21st to end	Day	39% 4 13% 29% 12% 2	1795
December	1st to 10th	Day	39% 4 15% 27% 13% 1	2680
	11th to 20th	Day	42% 5% 12% 26% 13% 2	3066
	21st to end	Day	43% 6% 10% 23% 15% 2	4048
January	1st to 10th	Night	37% 4 12% 24% 18% 4	8234
	11th to 20th	Night	40% 4 11% 22% 16% 7%	8280
	21st to end	Night	41% 5% 9% 22% 20% 4	8488
February	1st to 10th	Night	43% 5% 12% 24% 13% 2	2730
	11th to 20th	Night	45% 5% 10% 19% 17% 4	2460
	21st to end	Night	43% 4 8% 24% 17% 4	2076
March	1st to 10th	Night	43% 4 9% 22% 12% 9%	5494
	11th to 20th	Night	37% 7% 14% 24% 14% 4	5237
	21st to end	Night	45% 5% 7% 15% 23% 5%	5148
April	1st to 10th	Night	44% 6% 10% 19% 17% 4	2100
	11th to 20th	Night	43% 6% 10% 18% 20% 2	2075
	21st to end	Night	40% 6% 10% 21% 19% 5%	2100
May	1st to 10th	Night	50% 7% 12% 18% 12% 1	5268
	11th to 20th	Night	47% 7% 13% 20% 13% 1	4706
	21st to end	Night	51% 7% 11% 20% 10% 1	5115
June	1st to 10th	Night	39% 7% 11% 21% 20% 2	1680
	11th to 20th	Night	40% 8% 15% 24% 12% 1	1680
	21st to end	Night	36% 9% 15% 23% 15% 1	1680
July	1st to 10th	Night	42% 9% 13% 22% 13% 1	4640
	11th to 20th	Night	41% 10% 15% 23% 11% 1	4632
	21st to end	Night	38% 7% 15% 21% 18% 1	4967
August	1st to 10th	Night	49% 8% 17% 16% 9% 1	2938
	11th to 20th	Night	40% 8% 12% 27% 11% 1	3327
	21st to end	Night	31% 6% 11% 29% 21% 1	3677
September	1st to 10th	Night	40% 7% 10% 22% 19% 2	2000
	11th to 20th	Night	33% 5% 11% 23% 25% 4	2072
	21st to end	Night	43% 7% 8% 21% 20% 2	2200
October	1st to 10th	Night	36% 6% 11% 23% 21% 2	3810
	11th to 20th	Night	25% 4 11% 27% 29% 5%	3899
	21st to end	Night	28% 4 11% 30% 24% 3	4474
November	1st to 10th	Night	33% 5% 12% 24% 23% 4	2667
	11th to 20th	Night	39% 4 8% 24% 20% 5%	2730
	21st to end	Night	38% 4 13% 26% 16% 1	2819
December	1st to 10th	Night	39% 4 12% 30% 12% 2	4720
	11th to 20th	Night	44% 5% 10% 24% 14% 4	5348
	21st to end	Night	45% 5% 11% 19% 16% 3	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% 32% 14% 3 1	220
	11th to 20th	Day	29% 32% 28% 10% 1	220
	21st to end	Day	24% 29% 31% 12% 3 1	344
February	1st to 10th	Day	25% 25% 36% 11% 3 1	330
	11th to 20th	Day	28% 23% 37% 11% 1	534
	21st to end	Day	27% 23% 30% 17% 3	446
March	1st to 10th	Day	25% 24% 32% 16% 3	540
	11th to 20th	Day	24% 25% 33% 14% 4 1	540
	21st to end	Day	27% 25% 31% 12% 4 1	594
April	1st to 10th	Day	28% 22% 32% 12% 6% 1	540
	11th to 20th	Day	22% 24% 32% 13% 8% 2	532
	21st to end	Day	26% 19% 31% 18% 4 2	540
May	1st to 10th	Day	29% 19% 30% 15% 5% 2	543
	11th to 20th	Day	21% 14% 35% 22% 7% 1	567
	21st to end	Day	24% 9% 25% 26% 14% 2	617
June	1st to 10th	Day	15% 11% 31% 29% 11% 2	570
	11th to 20th	Day	18% 12% 30% 27% 11% 2	570
	21st to end	Day	15% 8% 33% 30% 12% 2	570
July	1st to 10th	Day	12% 6% 25% 33% 19% 5%	565
	11th to 20th	Day	8% 6% 26% 34% 20% 5%	564
	21st to end	Day	11% 7% 29% 33% 15% 4	620
August	1st to 10th	Day	11% 7% 22% 37% 17% 6%	566
	11th to 20th	Day	12% 5% 23% 35% 21% 4	559
	21st to end	Day	11% 7% 28% 31% 15% 7%	619
September	1st to 10th	Day	15% 9% 28% 25% 17% 7%	530
	11th to 20th	Day	15% 6% 26% 31% 14% 8%	530
	21st to end	Day	23% 11% 25% 27% 10% 4	530
October	1st to 10th	Day	23% 7% 25% 23% 15% 6%	530
	11th to 20th	Day	19% 14% 30% 24% 11% 3	530
	21st to end	Day	21% 15% 31% 21% 9% 2	509
November	1st to 10th	Day	15% 18% 32% 20% 12% 2	425
	11th to 20th	Day	24% 19% 31% 20% 6%	430
	21st to end	Day	22% 21% 33% 16% 7% 1	335
December	1st to 10th	Day	26% 25% 31% 10% 6%	220
	11th to 20th	Day	34% 21% 29% 12% 4	220
	21st to end	Day	26% 19% 33% 14% 7%	242
January	1st to 10th	Night	20% 21% 38% 18% 3	840
	11th to 20th	Night	25% 18% 34% 20% 3	840
	21st to end	Night	20% 21% 39% 20% 1	924
February	1st to 10th	Night	22% 17% 36% 23% 2	840
	11th to 20th	Night	26% 20% 38% 15% 1	823
	21st to end	Night	25% 20% 35% 18% 2	692
March	1st to 10th	Night	24% 19% 33% 21% 3	840
	11th to 20th	Night	23% 20% 34% 18% 4	840
	21st to end	Night	22% 15% 40% 18% 4	924
April	1st to 10th	Night	23% 20% 35% 18% 5%	840
	11th to 20th	Night	20% 16% 38% 21% 4	831
	21st to end	Night	20% 13% 38% 25% 4	840
May	1st to 10th	Night	24% 14% 35% 21% 5%	633
	11th to 20th	Night	22% 10% 36% 27% 6%	442
	21st to end	Night	18% 8% 26% 36% 11% 2	455
June	1st to 10th	Night	16% 7% 30% 37% 10%	420
	11th to 20th	Night	15% 7% 31% 37% 11%	420
	21st to end	Night	10% 4 30% 44% 12%	420
July	1st to 10th	Night	11% 4 26% 42% 16% 1	410
	11th to 20th	Night	12% 3 22% 43% 19% 1	408
	21st to end	Night	10% 3 27% 43% 17%	460
August	1st to 10th	Night	13% 3 19% 43% 20% 2	583
	11th to 20th	Night	13% 4 20% 38% 23% 2	830
	21st to end	Night	15% 4 19% 41% 19% 2	917
September	1st to 10th	Night	15% 4 27% 35% 17% 2	800
	11th to 20th	Night	14% 5% 22% 34% 21% 4	800
	21st to end	Night	21% 6% 24% 34% 14% 1	800
October	1st to 10th	Night	21% 8% 27% 26% 15% 3	800
	11th to 20th	Night	17% 12% 29% 31% 10%	800
	21st to end	Night	22% 13% 32% 26% 7%	880
November	1st to 10th	Night	15% 11% 35% 27% 11% 1	820
	11th to 20th	Night	21% 18% 32% 22% 7%	840
	21st to end	Night	18% 18% 35% 23% 6%	840
December	1st to 10th	Night	26% 16% 33% 19% 5% 1	840
	11th to 20th	Night	23% 16% 36% 22% 3	840
	21st to end	Night	25% 15% 35% 23% 3	924

Page generated at 2026-08-27 04:07:12. Version ac07

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