Woodbridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Woodbridge clear sky chart from 2005-11-06 to 2026-09-14.

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	14% 9% 3 9% 5% 5% 5% 4 6% 7% 33%	149794
	Night	14% 10% 3 8% 5% 5% 5% 4 5% 7% 34%	141202
Transparency	Day	47% 7% 13% 21% 11% 1	153390
	Night	47% 7% 13% 20% 12% 1	145695
Seeing	Day	18% 13% 30% 23% 11% 4	17002
	Night	18% 10% 31% 28% 11% 1	26127

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	17% 11% 4 13% 6% 6% 5% 4 6% 6% 21%	4661
	11th to 20th	Day	10% 18% 7% 18% 9% 7% 5% 4 4 4 13%	5122
	21st to end	Day	13% 15% 6% 14% 8% 6% 6% 4 5% 6% 18%	5780
February	1st to 10th	Day	14% 16% 4 13% 6% 5% 5% 4 5% 5% 22%	1890
	11th to 20th	Day	12% 14% 6% 12% 8% 5% 5% 3 5% 6% 23%	1843
	21st to end	Day	16% 15% 5% 10% 5% 5% 6% 4 4 6% 25%	1618
March	1st to 10th	Day	18% 10% 4 9% 6% 5% 4 3 4 5% 31%	5042
	11th to 20th	Day	11% 13% 4 9% 5% 5% 5% 4 6% 7% 31%	5090
	21st to end	Day	18% 10% 4 9% 6% 4 4 3 4 5% 33%	5586
April	1st to 10th	Day	17% 13% 3 9% 6% 4 5% 3 5% 6% 29%	2473
	11th to 20th	Day	19% 10% 3 8% 4 4 4 4 5% 5% 34%	2584
	21st to end	Day	20% 8% 3 8% 5% 4 4 3 5% 6% 33%	2730
May	1st to 10th	Day	19% 9% 3 8% 4 4 4 4 5% 7% 32%	7642
	11th to 20th	Day	14% 8% 3 8% 4 5% 5% 4 6% 8% 36%	8156
	21st to end	Day	17% 6% 2 5% 4 4 4 3 5% 7% 43%	9060
June	1st to 10th	Day	13% 7% 2 6% 5% 4 5% 5% 6% 8% 38%	2940
	11th to 20th	Day	11% 5% 2 6% 5% 4 5% 5% 7% 10% 38%	2940
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 5% 7% 9% 38%	3120
July	1st to 10th	Day	8% 6% 3 7% 5% 6% 6% 5% 8% 10% 37%	8404
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 7% 11% 48%	8280
	21st to end	Day	8% 5% 2 7% 4 5% 6% 4 8% 8% 43%	8385
August	1st to 10th	Day	17% 7% 3 7% 4 4 5% 4 6% 7% 37%	6014
	11th to 20th	Day	8% 6% 2 8% 5% 5% 6% 6% 8% 10% 35%	5951
	21st to end	Day	10% 6% 3 8% 5% 5% 5% 5% 7% 9% 37%	6359
September	1st to 10th	Day	12% 5% 2 7% 5% 5% 5% 4 6% 7% 42%	2520
	11th to 20th	Day	10% 5% 2 6% 4 5% 4 3 6% 9% 46%	2308
	21st to end	Day	14% 7% 3 7% 5% 5% 6% 4 6% 9% 35%	2165
October	1st to 10th	Day	17% 8% 3 6% 4 4 4 4 6% 6% 37%	2000
	11th to 20th	Day	19% 8% 3 9% 5% 5% 5% 4 6% 7% 30%	2000
	21st to end	Day	23% 11% 4 8% 6% 5% 5% 4 5% 7% 22%	2200
November	1st to 10th	Day	14% 11% 3 8% 6% 5% 5% 4 6% 7% 32%	1777
	11th to 20th	Day	14% 12% 4 9% 6% 5% 6% 5% 6% 7% 26%	1680
	21st to end	Day	16% 16% 4 10% 6% 6% 5% 4 6% 6% 20%	1680
December	1st to 10th	Day	17% 18% 5% 12% 6% 6% 6% 4 5% 6% 15%	2680
	11th to 20th	Day	20% 17% 4 11% 5% 4 4 3 5% 5% 21%	3066
	21st to end	Day	26% 17% 6% 12% 6% 4 4 3 4 4 14%	4048
January	1st to 10th	Night	14% 12% 5% 11% 6% 6% 6% 4 6% 7% 23%	8234
	11th to 20th	Night	11% 17% 6% 14% 10% 7% 6% 4 5% 5% 14%	7759
	21st to end	Night	13% 12% 5% 11% 8% 6% 6% 4 6% 7% 22%	8401
February	1st to 10th	Night	12% 15% 4 10% 7% 5% 5% 4 5% 6% 26%	2730
	11th to 20th	Night	13% 14% 5% 9% 8% 5% 5% 4 5% 5% 26%	2663
	21st to end	Night	12% 14% 4 10% 7% 5% 4 5% 6% 6% 28%	2183
March	1st to 10th	Night	16% 9% 5% 8% 6% 6% 5% 4 5% 6% 30%	5018
	11th to 20th	Night	10% 9% 3 7% 5% 5% 5% 4 7% 9% 36%	5089
	21st to end	Night	20% 8% 3 5% 4 4 4 3 5% 5% 39%	5588
April	1st to 10th	Night	17% 10% 3 8% 6% 4 4 5% 5% 6% 31%	2146
	11th to 20th	Night	15% 9% 3 7% 5% 4 4 4 5% 6% 38%	2003
	21st to end	Night	15% 8% 3 6% 4 5% 4 4 6% 8% 37%	1890
May	1st to 10th	Night	20% 8% 2 6% 4 4 4 4 5% 6% 36%	5257
	11th to 20th	Night	14% 9% 3 7% 4 4 4 4 5% 7% 39%	4703
	21st to end	Night	17% 5% 2 5% 3 3 3 3 5% 6% 47%	5114
June	1st to 10th	Night	12% 5% 2 5% 6% 4 4 3 6% 8% 44%	1680
	11th to 20th	Night	8% 6% 3 6% 4 5% 5% 4 6% 10% 43%	1680
	21st to end	Night	10% 6% 2 7% 5% 5% 4 4 6% 7% 45%	1484
July	1st to 10th	Night	7% 5% 2 6% 4 4 4 4 5% 10% 48%	4509
	11th to 20th	Night	8% 4 2 4 4 4 4 4 6% 9% 52%	4680
	21st to end	Night	8% 4 2 6% 4 4 5% 4 6% 8% 50%	5675
August	1st to 10th	Night	12% 7% 2 7% 5% 4 4 3 5% 6% 43%	4135
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 5% 8% 50%	4095
	21st to end	Night	11% 5% 3 6% 4 4 4 4 7% 9% 43%	4720
September	1st to 10th	Night	8% 5% 2 6% 4 4 5% 4 6% 7% 48%	2100
	11th to 20th	Night	10% 5% 1 4 4 3 4 4 5% 7% 54%	2156
	21st to end	Night	15% 7% 3 7% 4 4 4 3 6% 6% 41%	2235
October	1st to 10th	Night	15% 7% 2 7% 4 4 5% 3 5% 6% 41%	2400
	11th to 20th	Night	18% 8% 2 8% 6% 4 4 3 5% 6% 36%	2400
	21st to end	Night	19% 10% 3 8% 4 5% 5% 4 6% 7% 30%	2640
November	1st to 10th	Night	16% 8% 2 6% 5% 5% 4 3 6% 6% 38%	2737
	11th to 20th	Night	15% 11% 3 9% 6% 5% 5% 4 6% 7% 30%	2940
	21st to end	Night	19% 12% 4 9% 6% 5% 4 4 6% 7% 24%	2940
December	1st to 10th	Night	17% 15% 5% 10% 7% 6% 5% 4 6% 6% 17%	4720
	11th to 20th	Night	16% 18% 4 11% 6% 5% 5% 4 5% 5% 21%	5348
	21st to end	Night	24% 15% 6% 13% 6% 5% 4 3 4 5% 16%	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	61% 7% 13% 11% 9%	4662
	11th to 20th	Day	73% 5% 10% 9% 4	5156
	21st to end	Day	64% 5% 12% 10% 8%	5780
February	1st to 10th	Day	61% 8% 11% 15% 5% 1	1890
	11th to 20th	Day	60% 7% 12% 14% 6% 1	1852
	21st to end	Day	59% 7% 12% 15% 7% 1	1618
March	1st to 10th	Day	53% 5% 15% 13% 12% 1	5045
	11th to 20th	Day	49% 7% 16% 18% 8% 2	5090
	21st to end	Day	52% 6% 10% 19% 12% 1	5586
April	1st to 10th	Day	55% 6% 11% 18% 10% 1	2473
	11th to 20th	Day	49% 6% 11% 21% 13% 1	2584
	21st to end	Day	50% 7% 12% 18% 11% 2	2730
May	1st to 10th	Day	48% 7% 14% 17% 11% 4	7651
	11th to 20th	Day	44% 9% 12% 20% 14% 1	8160
	21st to end	Day	40% 5% 11% 28% 14% 2	9061
June	1st to 10th	Day	41% 8% 12% 22% 16% 1	2940
	11th to 20th	Day	38% 8% 15% 24% 14% 1	2940
	21st to end	Day	39% 8% 15% 24% 14% 1	3120
July	1st to 10th	Day	38% 7% 16% 25% 13% 1	8335
	11th to 20th	Day	28% 5% 13% 37% 16% 1	8205
	21st to end	Day	34% 7% 14% 28% 16%	8200
August	1st to 10th	Day	45% 7% 14% 17% 15% 3	6001
	11th to 20th	Day	39% 8% 18% 26% 8%	5990
	21st to end	Day	40% 7% 15% 30% 8%	6359
September	1st to 10th	Day	38% 9% 15% 27% 10% 1	2520
	11th to 20th	Day	33% 7% 16% 30% 14%	2308
	21st to end	Day	43% 9% 14% 25% 9%	2165
October	1st to 10th	Day	37% 7% 15% 26% 13% 1	3260
	11th to 20th	Day	39% 5% 16% 25% 14%	3240
	21st to end	Day	53% 7% 13% 19% 7%	3538
November	1st to 10th	Day	48% 8% 16% 20% 8% 1	1777
	11th to 20th	Day	53% 9% 14% 15% 8%	1680
	21st to end	Day	60% 9% 15% 14% 3	1680
December	1st to 10th	Day	67% 8% 14% 8% 3	2680
	11th to 20th	Day	63% 7% 12% 9% 8%	3066
	21st to end	Day	73% 7% 7% 8% 6%	4048
January	1st to 10th	Night	57% 7% 13% 17% 6%	8234
	11th to 20th	Night	67% 8% 10% 10% 5% 1	7800
	21st to end	Night	59% 6% 12% 11% 12% 1	8401
February	1st to 10th	Night	56% 7% 11% 19% 6% 1	2730
	11th to 20th	Night	56% 7% 12% 16% 8%	2665
	21st to end	Night	54% 7% 14% 17% 8%	2183
March	1st to 10th	Night	51% 7% 13% 16% 11% 2	5028
	11th to 20th	Night	40% 7% 20% 21% 10% 2	5090
	21st to end	Night	46% 6% 10% 20% 17% 2	5588
April	1st to 10th	Night	51% 6% 12% 17% 12% 2	2146
	11th to 20th	Night	47% 6% 10% 21% 14% 2	2003
	21st to end	Night	43% 8% 12% 18% 16% 2	1890
May	1st to 10th	Night	47% 6% 12% 16% 15% 5%	5264
	11th to 20th	Night	43% 8% 13% 20% 14% 2	4704
	21st to end	Night	38% 6% 12% 25% 18% 2	5115
June	1st to 10th	Night	36% 7% 12% 24% 19% 2	1680
	11th to 20th	Night	35% 7% 12% 24% 21% 2	1680
	21st to end	Night	36% 7% 13% 25% 17% 1	1484
July	1st to 10th	Night	31% 6% 16% 28% 17% 2	4469
	11th to 20th	Night	28% 5% 12% 33% 22% 1	4632
	21st to end	Night	30% 7% 12% 28% 21% 1	5546
August	1st to 10th	Night	41% 5% 12% 22% 15% 5%	4124
	11th to 20th	Night	32% 6% 16% 34% 11% 1	4122
	21st to end	Night	36% 6% 16% 29% 11% 1	4720
September	1st to 10th	Night	32% 8% 16% 29% 14% 1	2100
	11th to 20th	Night	28% 7% 12% 35% 18% 1	2156
	21st to end	Night	42% 7% 13% 26% 12%	2235
October	1st to 10th	Night	33% 5% 11% 27% 24% 1	3920
	11th to 20th	Night	41% 6% 13% 27% 12%	3899
	21st to end	Night	40% 8% 17% 25% 10% 1	4252
November	1st to 10th	Night	45% 6% 15% 22% 11% 1	2737
	11th to 20th	Night	50% 9% 14% 17% 9% 1	2940
	21st to end	Night	56% 7% 19% 14% 3	2940
December	1st to 10th	Night	63% 8% 14% 12% 3	4720
	11th to 20th	Night	62% 6% 12% 11% 8%	5348
	21st to end	Night	69% 8% 10% 8% 5%	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	22% 21% 31% 20% 5% 1	220
	11th to 20th	Day	24% 26% 31% 13% 5% 1	306
	21st to end	Day	25% 21% 32% 19% 3	363
February	1st to 10th	Day	25% 22% 36% 13% 4 1	330
	11th to 20th	Day	25% 22% 39% 12% 2	330
	21st to end	Day	31% 21% 36% 12%	286
March	1st to 10th	Day	22% 16% 35% 21% 5%	540
	11th to 20th	Day	25% 18% 36% 16% 5% 1	540
	21st to end	Day	27% 20% 30% 18% 5% 1	594
April	1st to 10th	Day	24% 21% 32% 17% 6%	540
	11th to 20th	Day	27% 18% 28% 17% 7% 2	532
	21st to end	Day	24% 13% 37% 18% 7% 2	540
May	1st to 10th	Day	22% 13% 31% 21% 8% 4	543
	11th to 20th	Day	16% 12% 32% 24% 12% 4	567
	21st to end	Day	17% 9% 30% 26% 14% 5%	617
June	1st to 10th	Day	13% 13% 31% 31% 11% 2	570
	11th to 20th	Day	14% 11% 30% 29% 15% 2	570
	21st to end	Day	16% 7% 32% 31% 11% 3	750
July	1st to 10th	Day	9% 7% 26% 34% 18% 6%	612
	11th to 20th	Day	12% 6% 25% 33% 16% 8%	564
	21st to end	Day	8% 4 30% 37% 15% 7%	620
August	1st to 10th	Day	13% 6% 21% 29% 22% 9%	566
	11th to 20th	Day	9% 5% 27% 29% 20% 10%	559
	21st to end	Day	11% 7% 26% 29% 19% 8%	627
September	1st to 10th	Day	13% 8% 25% 29% 16% 10%	570
	11th to 20th	Day	9% 5% 20% 27% 24% 15%	542
	21st to end	Day	15% 9% 29% 25% 16% 6%	530
October	1st to 10th	Day	18% 13% 26% 23% 14% 5%	530
	11th to 20th	Day	18% 17% 36% 19% 8% 2	530
	21st to end	Day	28% 15% 30% 22% 5%	583
November	1st to 10th	Day	21% 22% 28% 21% 8% 1	309
	11th to 20th	Day	21% 26% 30% 17% 4 1	220
	21st to end	Day	25% 18% 40% 15% 2	220
December	1st to 10th	Day	27% 20% 33% 16% 4	220
	11th to 20th	Day	27% 25% 30% 15% 4	220
	21st to end	Day	28% 21% 36% 12% 2	242
January	1st to 10th	Night	22% 16% 38% 20% 4	840
	11th to 20th	Night	26% 17% 31% 23% 3	840
	21st to end	Night	19% 11% 40% 23% 6%	924
February	1st to 10th	Night	20% 15% 39% 23% 3	840
	11th to 20th	Night	22% 15% 37% 23% 3	823
	21st to end	Night	20% 17% 38% 22% 3	692
March	1st to 10th	Night	18% 16% 38% 24% 4	840
	11th to 20th	Night	21% 17% 34% 23% 5%	840
	21st to end	Night	21% 12% 35% 25% 7%	924
April	1st to 10th	Night	23% 11% 36% 25% 4	840
	11th to 20th	Night	17% 13% 37% 24% 8% 1	759
	21st to end	Night	18% 10% 32% 31% 9%	630
May	1st to 10th	Night	18% 6% 30% 32% 12% 2	630
	11th to 20th	Night	17% 5% 31% 36% 10% 1	440
	21st to end	Night	12% 5% 29% 35% 18%	455
June	1st to 10th	Night	15% 4 28% 38% 15%	420
	11th to 20th	Night	10% 6% 29% 41% 14%	420
	21st to end	Night	11% 6% 22% 46% 14%	420
July	1st to 10th	Night	5% 4 23% 45% 21% 1	410
	11th to 20th	Night	10% 3 24% 42% 20% 2	408
	21st to end	Night	7% 3 21% 44% 22% 1	667
August	1st to 10th	Night	10% 1 16% 43% 29% 2	627
	11th to 20th	Night	8% 3 17% 45% 26% 2	624
	21st to end	Night	11% 4 22% 37% 24% 2	777
September	1st to 10th	Night	10% 6% 24% 35% 20% 4	840
	11th to 20th	Night	11% 4 19% 33% 28% 5%	813
	21st to end	Night	18% 6% 22% 31% 20% 4	800
October	1st to 10th	Night	18% 6% 28% 27% 19% 3	800
	11th to 20th	Night	20% 11% 32% 27% 9% 1	800
	21st to end	Night	24% 11% 33% 28% 4	880
November	1st to 10th	Night	21% 11% 30% 27% 9% 1	820
	11th to 20th	Night	20% 14% 34% 23% 7% 2	840
	21st to end	Night	26% 13% 34% 23% 5%	840
December	1st to 10th	Night	27% 13% 37% 18% 5%	840
	11th to 20th	Night	23% 16% 40% 18% 3	840
	21st to end	Night	30% 15% 33% 20% 2	924

Page generated at 2026-09-11 04:11:53. Version ac07

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