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 2025-04-26.

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% 10% 3 9% 5% 5% 5% 4 6% 7% 32%	114038
	Night	14% 10% 4 8% 5% 5% 5% 4 5% 7% 33%	114516
Transparency	Day	48% 7% 14% 19% 11% 1	117677
	Night	48% 7% 13% 19% 11% 1	119041
Seeing	Day	18% 13% 30% 23% 11% 4	15142
	Night	19% 10% 31% 28% 11% 1	24503

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% 11% 4 14% 6% 6% 6% 4 6% 6% 24%	3597
	11th to 20th	Day	11% 17% 6% 18% 10% 8% 5% 3 4 4 15%	3930
	21st to end	Day	16% 16% 6% 13% 7% 5% 6% 3 5% 5% 17%	4466
February	1st to 10th	Day	15% 16% 4 13% 6% 6% 5% 4 5% 5% 21%	1800
	11th to 20th	Day	12% 14% 6% 12% 8% 5% 5% 3 5% 6% 23%	1753
	21st to end	Day	17% 15% 5% 10% 5% 5% 6% 4 4 6% 25%	1543
March	1st to 10th	Day	18% 10% 4 9% 6% 5% 5% 3 4 5% 31%	4932
	11th to 20th	Day	11% 12% 4 9% 5% 5% 5% 4 6% 8% 31%	4980
	21st to end	Day	18% 10% 4 9% 5% 4 4 3 4 5% 33%	5465
April	1st to 10th	Day	16% 13% 3 9% 6% 4 5% 3 5% 6% 29%	2355
	11th to 20th	Day	19% 10% 3 7% 4 4 4 4 5% 5% 35%	2460
	21st to end	Day	20% 8% 3 8% 5% 4 4 3 5% 6% 33%	2535
May	1st to 10th	Day	18% 8% 3 7% 5% 4 4 4 6% 8% 33%	4108
	11th to 20th	Day	16% 9% 3 9% 5% 5% 4 4 5% 8% 32%	4360
	21st to end	Day	11% 6% 2 6% 4 4 5% 4 5% 8% 46%	4837
June	1st to 10th	Day	13% 8% 2 7% 6% 4 5% 5% 6% 8% 37%	2660
	11th to 20th	Day	12% 6% 2 6% 5% 4 4 4 7% 11% 39%	2660
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 5% 7% 9% 38%	2822
July	1st to 10th	Day	9% 5% 2 6% 4 5% 6% 5% 8% 11% 39%	4509
	11th to 20th	Day	9% 4 2 5% 4 4 5% 5% 8% 10% 44%	4440
	21st to end	Day	7% 5% 2 7% 5% 5% 6% 5% 8% 9% 40%	4483
August	1st to 10th	Day	16% 7% 2 6% 4 4 5% 4 7% 9% 36%	4104
	11th to 20th	Day	9% 7% 3 9% 5% 5% 6% 5% 8% 10% 34%	4044
	21st to end	Day	8% 5% 3 7% 5% 5% 5% 5% 7% 10% 41%	4372
September	1st to 10th	Day	12% 6% 2 7% 5% 5% 4 4 6% 7% 41%	2280
	11th to 20th	Day	11% 5% 2 6% 4 5% 4 3 6% 8% 45%	2159
	21st to end	Day	13% 7% 3 7% 6% 5% 6% 4 6% 9% 35%	2057
October	1st to 10th	Day	18% 8% 3 7% 4 4 5% 4 6% 6% 35%	1900
	11th to 20th	Day	19% 8% 3 9% 5% 6% 5% 3 6% 7% 29%	1900
	21st to end	Day	23% 11% 4 8% 6% 5% 5% 4 5% 6% 22%	2090
November	1st to 10th	Day	13% 10% 3 8% 6% 5% 5% 4 6% 7% 32%	1691
	11th to 20th	Day	15% 12% 4 10% 6% 5% 6% 5% 6% 7% 25%	1600
	21st to end	Day	17% 15% 4 10% 6% 6% 5% 4 6% 6% 20%	1600
December	1st to 10th	Day	18% 18% 5% 12% 6% 6% 6% 4 5% 6% 15%	2600
	11th to 20th	Day	20% 17% 4 11% 5% 4 4 3 5% 5% 21%	2986
	21st to end	Day	27% 17% 6% 12% 6% 4 4 3 4 4 14%	3960
January	1st to 10th	Night	14% 11% 5% 11% 6% 7% 6% 5% 6% 7% 23%	6349
	11th to 20th	Night	12% 14% 6% 14% 10% 7% 6% 4 5% 5% 15%	5951
	21st to end	Night	16% 13% 6% 11% 6% 6% 6% 3 6% 6% 21%	6490
February	1st to 10th	Night	13% 16% 4 10% 7% 5% 5% 4 6% 6% 25%	2600
	11th to 20th	Night	13% 14% 5% 9% 8% 5% 5% 4 5% 5% 26%	2533
	21st to end	Night	13% 13% 4 10% 7% 5% 4 5% 6% 6% 28%	2082
March	1st to 10th	Night	16% 9% 5% 8% 6% 6% 5% 4 5% 6% 30%	4908
	11th to 20th	Night	9% 9% 3 7% 5% 5% 5% 4 7% 9% 36%	4979
	21st to end	Night	20% 8% 3 5% 4 4 4 3 5% 5% 39%	5467
April	1st to 10th	Night	17% 11% 3 8% 6% 4 4 5% 5% 6% 31%	2044
	11th to 20th	Night	15% 9% 3 7% 5% 4 4 4 5% 6% 38%	1907
	21st to end	Night	16% 9% 4 6% 4 5% 4 4 6% 8% 36%	1761
May	1st to 10th	Night	18% 7% 2 6% 4 4 5% 4 5% 6% 39%	2833
	11th to 20th	Night	15% 9% 3 6% 4 4 4 4 6% 7% 38%	2532
	21st to end	Night	10% 4 2 5% 4 4 4 3 6% 8% 51%	2738
June	1st to 10th	Night	12% 5% 2 5% 6% 5% 5% 4 6% 8% 42%	1520
	11th to 20th	Night	8% 6% 3 6% 4 5% 5% 4 7% 9% 43%	1520
	21st to end	Night	10% 6% 2 6% 5% 5% 4 4 6% 7% 46%	1343
July	1st to 10th	Night	6% 4 2 5% 4 4 4 4 5% 10% 51%	2427
	11th to 20th	Night	11% 4 2 4 3 3 4 4 6% 8% 51%	2520
	21st to end	Night	7% 4 2 6% 4 4 5% 4 6% 9% 51%	3053
August	1st to 10th	Night	9% 6% 2 7% 4 5% 4 3 6% 7% 48%	2825
	11th to 20th	Night	10% 5% 1 6% 4 3 4 3 5% 8% 50%	2785
	21st to end	Night	10% 5% 2 6% 4 4 4 4 6% 8% 47%	3252
September	1st to 10th	Night	8% 5% 2 6% 5% 4 4 4 7% 7% 48%	1900
	11th to 20th	Night	10% 5% 1 4 3 3 4 4 5% 8% 53%	2019
	21st to end	Night	15% 7% 3 7% 4 4 4 3 6% 6% 41%	2123
October	1st to 10th	Night	16% 7% 3 7% 4 4 5% 4 5% 6% 39%	2280
	11th to 20th	Night	17% 8% 2 8% 6% 4 5% 3 5% 6% 35%	2280
	21st to end	Night	19% 10% 3 8% 4 5% 5% 4 6% 7% 29%	2508
November	1st to 10th	Night	16% 8% 2 6% 5% 5% 5% 3 6% 6% 38%	2603
	11th to 20th	Night	16% 11% 3 8% 6% 5% 5% 4 6% 7% 29%	2800
	21st to end	Night	19% 11% 4 8% 6% 5% 4 4 6% 7% 25%	2800
December	1st to 10th	Night	18% 15% 5% 11% 7% 6% 5% 4 6% 6% 17%	4580
	11th to 20th	Night	16% 18% 4 11% 6% 5% 5% 4 5% 5% 21%	5208
	21st to end	Night	24% 15% 6% 12% 6% 5% 4 3 4 5% 16%	6996

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	57% 8% 14% 12% 10%	3598
	11th to 20th	Day	71% 5% 12% 9% 3	3964
	21st to end	Day	67% 5% 12% 9% 7%	4466
February	1st to 10th	Day	62% 8% 11% 15% 4 1	1800
	11th to 20th	Day	59% 7% 12% 13% 7% 1	1762
	21st to end	Day	59% 7% 12% 14% 7% 1	1543
March	1st to 10th	Day	53% 5% 15% 13% 12% 1	4935
	11th to 20th	Day	48% 7% 17% 18% 8% 2	4980
	21st to end	Day	51% 6% 10% 19% 12% 1	5465
April	1st to 10th	Day	54% 6% 11% 18% 10% 1	2355
	11th to 20th	Day	48% 6% 11% 21% 13% 1	2460
	21st to end	Day	51% 7% 11% 18% 11% 2	2535
May	1st to 10th	Day	44% 8% 15% 18% 13% 1	4120
	11th to 20th	Day	47% 11% 15% 19% 8% 1	4364
	21st to end	Day	34% 8% 14% 23% 17% 3	4837
June	1st to 10th	Day	42% 8% 13% 21% 14% 1	2660
	11th to 20th	Day	38% 8% 15% 23% 15% 1	2660
	21st to end	Day	39% 8% 15% 23% 14% 1	2822
July	1st to 10th	Day	36% 6% 17% 25% 15% 2	4439
	11th to 20th	Day	31% 7% 14% 36% 11% 1	4365
	21st to end	Day	35% 9% 15% 21% 18% 1	4340
August	1st to 10th	Day	42% 8% 15% 21% 14% 1	4091
	11th to 20th	Day	41% 9% 17% 23% 10%	4083
	21st to end	Day	35% 7% 13% 33% 10% 1	4372
September	1st to 10th	Day	39% 9% 15% 26% 11% 1	2280
	11th to 20th	Day	35% 7% 15% 29% 14%	2159
	21st to end	Day	43% 9% 14% 25% 8%	2057
October	1st to 10th	Day	38% 7% 15% 25% 13% 1	3160
	11th to 20th	Day	39% 6% 16% 25% 14%	3140
	21st to end	Day	53% 7% 14% 19% 6%	3428
November	1st to 10th	Day	48% 8% 16% 19% 8% 1	1691
	11th to 20th	Day	54% 10% 14% 14% 8%	1600
	21st to end	Day	59% 9% 15% 14% 2	1600
December	1st to 10th	Day	67% 8% 14% 8% 3	2600
	11th to 20th	Day	64% 8% 12% 9% 7%	2986
	21st to end	Day	72% 7% 7% 8% 6%	3960
January	1st to 10th	Night	56% 8% 13% 18% 6%	6349
	11th to 20th	Night	65% 9% 12% 10% 3	5992
	21st to end	Night	60% 7% 13% 10% 10% 1	6490
February	1st to 10th	Night	57% 7% 12% 18% 5% 1	2600
	11th to 20th	Night	57% 7% 12% 15% 8%	2535
	21st to end	Night	53% 7% 14% 17% 8%	2082
March	1st to 10th	Night	51% 7% 14% 15% 11% 2	4918
	11th to 20th	Night	40% 7% 20% 21% 10% 2	4980
	21st to end	Night	45% 6% 10% 20% 17% 2	5467
April	1st to 10th	Night	52% 6% 11% 17% 13% 2	2044
	11th to 20th	Night	47% 6% 10% 21% 15% 2	1907
	21st to end	Night	44% 8% 13% 17% 16% 2	1761
May	1st to 10th	Night	42% 8% 13% 17% 16% 3	2840
	11th to 20th	Night	42% 11% 16% 18% 11% 2	2533
	21st to end	Night	28% 8% 15% 23% 22% 3	2739
June	1st to 10th	Night	37% 7% 13% 23% 18% 2	1520
	11th to 20th	Night	35% 7% 13% 23% 21% 2	1520
	21st to end	Night	36% 7% 13% 25% 17% 1	1343
July	1st to 10th	Night	28% 6% 15% 25% 22% 4	2387
	11th to 20th	Night	30% 6% 14% 33% 16% 1	2472
	21st to end	Night	29% 8% 15% 30% 16% 2	2956
August	1st to 10th	Night	35% 6% 13% 28% 15% 2	2814
	11th to 20th	Night	33% 6% 16% 32% 12% 1	2812
	21st to end	Night	34% 7% 13% 31% 14% 1	3252
September	1st to 10th	Night	32% 8% 16% 28% 15% 1	1900
	11th to 20th	Night	29% 7% 12% 34% 18%	2019
	21st to end	Night	41% 7% 13% 27% 11%	2123
October	1st to 10th	Night	33% 5% 11% 27% 24% 1	3800
	11th to 20th	Night	41% 6% 14% 27% 12%	3779
	21st to end	Night	40% 8% 17% 25% 10% 1	4120
November	1st to 10th	Night	45% 6% 15% 22% 11% 1	2603
	11th to 20th	Night	50% 9% 14% 17% 9% 1	2800
	21st to end	Night	56% 8% 19% 14% 3	2800
December	1st to 10th	Night	63% 8% 14% 12% 3	4580
	11th to 20th	Night	63% 7% 12% 11% 7%	5208
	21st to end	Night	69% 8% 10% 8% 5%	6996

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	21% 20% 32% 21% 5% 1	200
	11th to 20th	Day	23% 26% 31% 14% 5% 1	278
	21st to end	Day	25% 22% 32% 18% 3	330
February	1st to 10th	Day	26% 23% 37% 11% 3	300
	11th to 20th	Day	25% 23% 39% 10% 2	300
	21st to end	Day	31% 21% 35% 12%	261
March	1st to 10th	Day	22% 17% 35% 20% 6%	500
	11th to 20th	Day	22% 17% 39% 17% 5% 1	500
	21st to end	Day	27% 18% 30% 18% 6% 1	550
April	1st to 10th	Day	22% 21% 33% 18% 6%	500
	11th to 20th	Day	26% 19% 28% 17% 7% 2	492
	21st to end	Day	24% 14% 36% 18% 7% 2	480
May	1st to 10th	Day	21% 12% 30% 22% 10% 5%	463
	11th to 20th	Day	17% 10% 30% 26% 13% 5%	487
	21st to end	Day	15% 7% 28% 28% 15% 5%	529
June	1st to 10th	Day	14% 13% 29% 32% 11% 2	490
	11th to 20th	Day	14% 9% 28% 31% 16% 2	490
	21st to end	Day	16% 8% 31% 31% 11% 4	652
July	1st to 10th	Day	9% 6% 26% 34% 20% 6%	528
	11th to 20th	Day	13% 5% 24% 33% 17% 8%	484
	21st to end	Day	8% 4 27% 39% 16% 7%	532
August	1st to 10th	Day	13% 6% 21% 29% 22% 9%	486
	11th to 20th	Day	10% 5% 25% 28% 21% 11%	479
	21st to end	Day	10% 7% 27% 28% 20% 9%	539
September	1st to 10th	Day	13% 8% 25% 28% 15% 10%	490
	11th to 20th	Day	10% 6% 22% 25% 22% 15%	490
	21st to end	Day	15% 10% 30% 24% 16% 6%	490
October	1st to 10th	Day	19% 13% 27% 22% 13% 5%	490
	11th to 20th	Day	18% 17% 36% 19% 8% 2	490
	21st to end	Day	29% 14% 30% 22% 5%	539
November	1st to 10th	Day	20% 22% 27% 22% 8% 1	283
	11th to 20th	Day	20% 26% 32% 18% 3 2	200
	21st to end	Day	24% 18% 41% 16% 2	200
December	1st to 10th	Day	28% 20% 34% 15% 4	200
	11th to 20th	Day	27% 25% 30% 16% 4	200
	21st to end	Day	27% 19% 39% 12% 3	220
January	1st to 10th	Night	22% 16% 37% 20% 4	800
	11th to 20th	Night	26% 16% 32% 23% 3	800
	21st to end	Night	20% 11% 40% 23% 6%	880
February	1st to 10th	Night	21% 16% 40% 22% 2	800
	11th to 20th	Night	22% 15% 37% 22% 3	783
	21st to end	Night	19% 17% 39% 22% 3	660
March	1st to 10th	Night	18% 16% 38% 24% 5%	800
	11th to 20th	Night	19% 17% 35% 23% 6%	800
	21st to end	Night	21% 11% 34% 25% 8%	880
April	1st to 10th	Night	24% 11% 37% 25% 4	800
	11th to 20th	Night	17% 13% 37% 23% 8% 1	723
	21st to end	Night	19% 9% 32% 30% 9%	587
May	1st to 10th	Night	17% 6% 30% 32% 13% 2	570
	11th to 20th	Night	16% 4 31% 36% 12% 1	398
	21st to end	Night	10% 4 29% 36% 20%	411
June	1st to 10th	Night	15% 4 29% 36% 16% 1	380
	11th to 20th	Night	10% 6% 28% 41% 15% 1	380
	21st to end	Night	11% 6% 23% 44% 16%	380
July	1st to 10th	Night	6% 4 24% 44% 22% 1	370
	11th to 20th	Night	11% 2 24% 41% 20% 2	368
	21st to end	Night	7% 3 20% 45% 23% 2	603
August	1st to 10th	Night	9% 1 17% 43% 28% 2	567
	11th to 20th	Night	8% 2 17% 44% 27% 2	564
	21st to end	Night	11% 3 23% 35% 25% 3	703
September	1st to 10th	Night	11% 6% 24% 34% 21% 4	760
	11th to 20th	Night	12% 4 20% 32% 28% 5%	760
	21st to end	Night	17% 6% 22% 31% 20% 4	760
October	1st to 10th	Night	18% 6% 28% 27% 18% 3	760
	11th to 20th	Night	20% 12% 31% 27% 10% 1	760
	21st to end	Night	25% 11% 33% 27% 4	836
November	1st to 10th	Night	22% 10% 31% 27% 10% 1	780
	11th to 20th	Night	21% 14% 34% 23% 7% 2	800
	21st to end	Night	25% 13% 34% 23% 5%	800
December	1st to 10th	Night	27% 13% 37% 18% 5%	800
	11th to 20th	Night	24% 16% 40% 18% 3	800
	21st to end	Night	30% 14% 33% 21% 3	880

Page generated at 2025-04-23 09:25:06. Version ac07

Copyright © 2025 Attilla Danko.