Woodstock
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Woodstock clear sky chart from 2005-11-06 to 2026-06-01.

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	18% 10% 3 8% 5% 5% 4 4 5% 7% 30%	131742
	Night	18% 11% 4 8% 5% 4 4 4 5% 6% 31%	131494
Transparency	Day	53% 5% 11% 20% 9% 1	135238
	Night	53% 5% 11% 20% 10% 1	136086
Seeing	Day	27% 15% 29% 19% 8% 2	18112
	Night	25% 14% 30% 24% 7%	26190

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% 18% 8% 12% 7% 5% 4 3 4 5% 23%	4150
	11th to 20th	Day	16% 14% 6% 16% 6% 4 4 3 4 5% 22%	4650
	21st to end	Day	6% 9% 4 10% 8% 7% 6% 4 6% 8% 30%	5262
February	1st to 10th	Day	13% 13% 4 11% 8% 6% 5% 4 5% 6% 27%	1890
	11th to 20th	Day	14% 13% 4 12% 8% 6% 5% 3 5% 5% 25%	1848
	21st to end	Day	11% 12% 4 9% 8% 5% 5% 4 5% 5% 32%	1730
March	1st to 10th	Day	23% 14% 4 11% 5% 4 4 3 4 4 25%	4711
	11th to 20th	Day	19% 17% 4 9% 5% 5% 4 3 5% 5% 24%	5090
	21st to end	Day	24% 14% 5% 9% 4 4 3 3 5% 7% 22%	5587
April	1st to 10th	Day	23% 13% 3 8% 5% 4 3 4 5% 6% 26%	2489
	11th to 20th	Day	21% 12% 3 7% 4 4 3 4 5% 6% 32%	2702
	21st to end	Day	24% 10% 3 8% 4 4 4 3 4 5% 33%	2730
May	1st to 10th	Day	24% 10% 3 9% 5% 5% 4 4 5% 6% 24%	6016
	11th to 20th	Day	25% 9% 3 8% 5% 5% 4 3 5% 6% 27%	6195
	21st to end	Day	19% 9% 3 8% 5% 5% 5% 5% 6% 7% 29%	7565
June	1st to 10th	Day	25% 8% 3 7% 5% 4 4 4 6% 6% 27%	3000
	11th to 20th	Day	21% 8% 2 6% 4 4 4 4 6% 8% 34%	3000
	21st to end	Day	26% 9% 3 6% 5% 4 5% 4 5% 7% 26%	3000
July	1st to 10th	Day	16% 7% 3 8% 6% 6% 6% 5% 8% 9% 27%	6820
	11th to 20th	Day	16% 7% 3 7% 4 5% 5% 4 7% 8% 36%	6665
	21st to end	Day	13% 7% 2 6% 4 4 4 4 6% 9% 39%	6801
August	1st to 10th	Day	18% 7% 3 7% 4 5% 5% 4 6% 8% 32%	4235
	11th to 20th	Day	15% 8% 3 8% 5% 5% 5% 5% 7% 8% 31%	4175
	21st to end	Day	16% 6% 2 6% 5% 4 5% 4 6% 8% 38%	4675
September	1st to 10th	Day	13% 6% 2 6% 5% 4 5% 4 5% 6% 44%	2366
	11th to 20th	Day	17% 6% 2 6% 4 3 3 3 4 6% 47%	2200
	21st to end	Day	18% 6% 2 6% 4 4 3 3 5% 8% 41%	2200
October	1st to 10th	Day	19% 9% 3 6% 4 4 4 3 5% 6% 39%	2080
	11th to 20th	Day	23% 8% 2 7% 4 4 4 3 5% 6% 35%	2000
	21st to end	Day	23% 12% 3 7% 5% 4 4 3 4 6% 29%	2002
November	1st to 10th	Day	20% 11% 2 7% 5% 5% 5% 4 5% 6% 32%	1839
	11th to 20th	Day	20% 11% 4 7% 4 5% 4 4 5% 6% 31%	1680
	21st to end	Day	21% 12% 4 9% 5% 4 5% 3 4 6% 27%	1680
December	1st to 10th	Day	18% 12% 3 10% 5% 5% 4 4 6% 5% 27%	2468
	11th to 20th	Day	20% 11% 4 9% 5% 4 4 3 4 5% 32%	2688
	21st to end	Day	19% 14% 4 11% 6% 5% 3 3 3 5% 27%	3553
January	1st to 10th	Night	14% 17% 7% 13% 6% 4 4 3 4 5% 23%	8756
	11th to 20th	Night	16% 14% 7% 13% 7% 5% 5% 4 4 5% 22%	8235
	21st to end	Night	7% 10% 4 10% 7% 6% 5% 4 6% 7% 33%	8905
February	1st to 10th	Night	12% 14% 4 10% 7% 5% 5% 4 5% 6% 29%	2730
	11th to 20th	Night	14% 14% 5% 10% 7% 5% 5% 3 4 5% 26%	2652
	21st to end	Night	13% 14% 3 8% 7% 4 4 3 4 5% 34%	2076
March	1st to 10th	Night	24% 12% 5% 9% 5% 5% 5% 3 4 4 23%	5349
	11th to 20th	Night	18% 15% 4 7% 5% 4 4 4 5% 6% 26%	5089
	21st to end	Night	28% 12% 4 6% 4 3 3 3 5% 6% 27%	5587
April	1st to 10th	Night	23% 13% 3 8% 4 3 4 3 4 6% 29%	2127
	11th to 20th	Night	24% 7% 3 6% 4 5% 4 3 4 6% 34%	1868
	21st to end	Night	25% 9% 2 6% 4 4 4 4 5% 5% 33%	1890
May	1st to 10th	Night	23% 10% 3 7% 5% 4 5% 4 6% 7% 27%	4144
	11th to 20th	Night	24% 7% 2 6% 4 5% 4 4 5% 7% 31%	3915
	21st to end	Night	19% 7% 2 6% 4 4 4 4 6% 7% 36%	3616
June	1st to 10th	Night	23% 8% 3 7% 5% 5% 6% 3 5% 7% 29%	1400
	11th to 20th	Night	19% 7% 2 6% 5% 4 5% 5% 6% 7% 35%	1400
	21st to end	Night	25% 9% 3 6% 5% 4 4 3 5% 7% 30%	1400
July	1st to 10th	Night	17% 7% 3 7% 5% 5% 5% 4 6% 7% 34%	3160
	11th to 20th	Night	15% 6% 2 7% 5% 4 5% 4 6% 8% 37%	3292
	21st to end	Night	10% 6% 3 7% 5% 5% 5% 4 6% 8% 41%	4004
August	1st to 10th	Night	18% 6% 3 8% 5% 5% 4 5% 6% 7% 32%	2915
	11th to 20th	Night	13% 7% 3 7% 4 6% 6% 4 7% 8% 35%	2872
	21st to end	Night	15% 6% 2 6% 4 4 4 3 5% 7% 44%	3223
September	1st to 10th	Night	15% 6% 2 4 3 4 4 4 5% 7% 47%	2030
	11th to 20th	Night	16% 6% 2 5% 4 2 4 3 4 6% 50%	2200
	21st to end	Night	18% 5% 2 5% 4 4 4 4 5% 6% 43%	2200
October	1st to 10th	Night	20% 6% 3 5% 4 3 3 4 5% 7% 42%	2320
	11th to 20th	Night	19% 10% 3 6% 5% 3 4 3 6% 5% 36%	2400
	21st to end	Night	23% 11% 3 7% 4 3 3 3 4 6% 32%	2835
November	1st to 10th	Night	21% 9% 3 7% 4 4 5% 4 5% 6% 33%	2678
	11th to 20th	Night	20% 10% 3 8% 4 4 3 3 5% 6% 34%	2940
	21st to end	Night	20% 11% 3 8% 5% 4 4 4 5% 6% 29%	2940
December	1st to 10th	Night	17% 12% 5% 10% 6% 5% 5% 3 5% 6% 26%	4938
	11th to 20th	Night	23% 10% 3 7% 5% 4 4 3 5% 5% 31%	5741
	21st to end	Night	19% 13% 4 11% 5% 4 4 3 5% 5% 26%	7667

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	66% 4 9% 15% 6%	4151
	11th to 20th	Day	63% 6% 9% 16% 7%	4680
	21st to end	Day	51% 5% 9% 18% 16% 1	5262
February	1st to 10th	Day	58% 4 10% 19% 8% 1	1890
	11th to 20th	Day	60% 4 9% 18% 9% 1	1856
	21st to end	Day	52% 5% 10% 22% 9% 2	1730
March	1st to 10th	Day	64% 3 7% 10% 13% 3	4715
	11th to 20th	Day	63% 5% 11% 13% 7% 1	5090
	21st to end	Day	62% 4 5% 18% 10% 1	5587
April	1st to 10th	Day	58% 4 9% 17% 10% 2	2489
	11th to 20th	Day	53% 4 9% 21% 12% 1	2702
	21st to end	Day	55% 3 8% 18% 12% 4	2730
May	1st to 10th	Day	60% 5% 7% 20% 8% 1	6027
	11th to 20th	Day	58% 5% 11% 18% 6% 2	6199
	21st to end	Day	52% 6% 10% 18% 13% 1	7565
June	1st to 10th	Day	56% 5% 11% 18% 10% 1	3000
	11th to 20th	Day	47% 5% 13% 20% 13% 2	3000
	21st to end	Day	58% 5% 11% 17% 8% 1	3000
July	1st to 10th	Day	50% 7% 17% 19% 7%	6745
	11th to 20th	Day	44% 7% 15% 27% 7%	6584
	21st to end	Day	41% 5% 15% 30% 8%	6605
August	1st to 10th	Day	49% 7% 14% 25% 6%	4222
	11th to 20th	Day	49% 7% 14% 24% 6%	4214
	21st to end	Day	41% 6% 15% 24% 13%	4675
September	1st to 10th	Day	39% 5% 13% 28% 14%	2366
	11th to 20th	Day	40% 3 11% 30% 15% 1	2200
	21st to end	Day	42% 6% 9% 29% 14% 1	2200
October	1st to 10th	Day	50% 5% 11% 27% 7%	3392
	11th to 20th	Day	49% 4 12% 27% 8%	3240
	21st to end	Day	43% 4 16% 23% 14%	3214
November	1st to 10th	Day	53% 5% 12% 20% 10% 1	1839
	11th to 20th	Day	54% 4 11% 19% 11% 1	1680
	21st to end	Day	59% 4 14% 18% 4	1680
December	1st to 10th	Day	58% 6% 16% 13% 7%	2468
	11th to 20th	Day	55% 4 9% 18% 10% 4	2688
	21st to end	Day	61% 4 10% 12% 11% 1	3553
January	1st to 10th	Night	63% 5% 11% 14% 7%	8756
	11th to 20th	Night	64% 6% 8% 15% 7% 1	8280
	21st to end	Night	48% 5% 8% 21% 17% 2	8905
February	1st to 10th	Night	55% 6% 9% 19% 10% 1	2730
	11th to 20th	Night	60% 4 8% 18% 9% 1	2655
	21st to end	Night	54% 3 9% 20% 12% 2	2076
March	1st to 10th	Night	65% 3 6% 14% 10% 2	5358
	11th to 20th	Night	57% 6% 15% 14% 7%	5090
	21st to end	Night	58% 3 6% 19% 13% 1	5587
April	1st to 10th	Night	57% 4 7% 16% 13% 3	2127
	11th to 20th	Night	52% 4 8% 19% 14% 2	1868
	21st to end	Night	53% 4 8% 19% 14% 2	1890
May	1st to 10th	Night	57% 4 11% 19% 9% 1	4150
	11th to 20th	Night	52% 7% 12% 22% 6% 1	3916
	21st to end	Night	45% 7% 14% 23% 10% 2	3617
June	1st to 10th	Night	55% 5% 9% 21% 11% 1	1400
	11th to 20th	Night	47% 6% 13% 22% 11% 1	1400
	21st to end	Night	56% 5% 12% 17% 10% 2	1400
July	1st to 10th	Night	48% 6% 17% 21% 8%	3125
	11th to 20th	Night	44% 7% 14% 29% 4	3250
	21st to end	Night	40% 7% 16% 28% 10%	3886
August	1st to 10th	Night	51% 7% 14% 22% 7%	2903
	11th to 20th	Night	45% 7% 19% 21% 8%	2899
	21st to end	Night	40% 5% 17% 22% 16%	3223
September	1st to 10th	Night	37% 5% 13% 31% 13% 1	2030
	11th to 20th	Night	37% 3 14% 31% 14%	2200
	21st to end	Night	42% 5% 12% 27% 14% 1	2200
October	1st to 10th	Night	47% 4 13% 25% 10%	3788
	11th to 20th	Night	46% 5% 11% 27% 10%	3899
	21st to end	Night	45% 5% 17% 22% 12%	4573
November	1st to 10th	Night	51% 5% 12% 22% 9% 1	2678
	11th to 20th	Night	53% 4 12% 19% 10% 1	2940
	21st to end	Night	56% 6% 13% 16% 8% 1	2940
December	1st to 10th	Night	58% 5% 11% 20% 6%	4938
	11th to 20th	Night	55% 4 8% 20% 11% 1	5742
	21st to end	Night	59% 5% 8% 16% 11% 2	7667

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	34% 16% 33% 15% 3	220
	11th to 20th	Day	34% 21% 30% 8% 6%	220
	21st to end	Day	23% 21% 34% 13% 7% 1	289
February	1st to 10th	Day	27% 17% 33% 17% 6% 1	430
	11th to 20th	Day	25% 22% 34% 14% 3 1	429
	21st to end	Day	22% 24% 33% 18% 4	446
March	1st to 10th	Day	32% 20% 31% 15% 2	540
	11th to 20th	Day	30% 20% 30% 14% 5% 1	540
	21st to end	Day	34% 18% 26% 15% 6% 1	594
April	1st to 10th	Day	37% 22% 24% 12% 4 1	540
	11th to 20th	Day	33% 19% 27% 15% 4 1	532
	21st to end	Day	34% 15% 30% 16% 4 1	540
May	1st to 10th	Day	34% 17% 27% 17% 4 1	543
	11th to 20th	Day	30% 17% 28% 18% 6% 1	654
	21st to end	Day	27% 15% 34% 18% 6% 1	845
June	1st to 10th	Day	32% 12% 28% 20% 7% 2	730
	11th to 20th	Day	25% 13% 30% 22% 8% 1	730
	21st to end	Day	31% 9% 30% 20% 8% 1	730
July	1st to 10th	Day	20% 12% 31% 24% 11% 2	720
	11th to 20th	Day	20% 7% 31% 28% 13% 1	654
	21st to end	Day	17% 8% 33% 31% 10% 2	576
August	1st to 10th	Day	15% 8% 32% 28% 14% 2	526
	11th to 20th	Day	20% 10% 22% 32% 12% 4	519
	21st to end	Day	20% 13% 26% 25% 12% 4	583
September	1st to 10th	Day	16% 10% 35% 23% 12% 4	530
	11th to 20th	Day	22% 11% 27% 21% 15% 5%	530
	21st to end	Day	21% 13% 28% 25% 9% 4	530
October	1st to 10th	Day	23% 13% 23% 22% 14% 4	464
	11th to 20th	Day	32% 13% 28% 15% 10% 3	420
	21st to end	Day	32% 16% 28% 17% 6%	462
November	1st to 10th	Day	32% 16% 26% 18% 7%	425
	11th to 20th	Day	30% 18% 29% 15% 7%	430
	21st to end	Day	32% 16% 32% 16% 4	430
December	1st to 10th	Day	30% 18% 31% 15% 4 1	299
	11th to 20th	Day	35% 23% 26% 12% 4	220
	21st to end	Day	33% 20% 31% 12% 3 1	242
January	1st to 10th	Night	26% 18% 31% 21% 3	937
	11th to 20th	Night	27% 17% 31% 20% 4	840
	21st to end	Night	20% 17% 36% 22% 4	924
February	1st to 10th	Night	23% 21% 32% 20% 5%	840
	11th to 20th	Night	25% 19% 36% 17% 3	823
	21st to end	Night	24% 19% 33% 20% 4	692
March	1st to 10th	Night	26% 15% 37% 21% 1	840
	11th to 20th	Night	30% 13% 32% 19% 5% 1	840
	21st to end	Night	27% 16% 29% 22% 6%	924
April	1st to 10th	Night	34% 17% 30% 16% 3	788
	11th to 20th	Night	31% 14% 33% 17% 5%	624
	21st to end	Night	32% 11% 32% 19% 5%	630
May	1st to 10th	Night	29% 14% 30% 22% 5%	630
	11th to 20th	Night	29% 13% 30% 23% 5%	622
	21st to end	Night	22% 13% 34% 25% 5%	496
June	1st to 10th	Night	27% 6% 30% 29% 8% 1	400
	11th to 20th	Night	21% 9% 30% 31% 9% 1	400
	21st to end	Night	29% 6% 30% 29% 6% 1	400
July	1st to 10th	Night	17% 3 38% 33% 9%	390
	11th to 20th	Night	15% 6% 28% 37% 12% 1	388
	21st to end	Night	18% 6% 26% 36% 13%	466
August	1st to 10th	Night	17% 4 28% 37% 14%	598
	11th to 20th	Night	16% 4 24% 39% 16% 1	592
	21st to end	Night	16% 6% 26% 36% 15% 1	660
September	1st to 10th	Night	19% 7% 34% 28% 12%	695
	11th to 20th	Night	19% 8% 24% 34% 15% 1	800
	21st to end	Night	21% 11% 27% 29% 12% 1	800
October	1st to 10th	Night	24% 9% 26% 29% 12% 1	800
	11th to 20th	Night	24% 12% 29% 26% 9% 1	800
	21st to end	Night	30% 17% 27% 23% 4	880
November	1st to 10th	Night	30% 16% 28% 20% 6%	826
	11th to 20th	Night	26% 18% 29% 21% 6% 1	950
	21st to end	Night	30% 16% 27% 21% 5%	950
December	1st to 10th	Night	32% 13% 30% 20% 4 1	950
	11th to 20th	Night	30% 20% 29% 17% 3	950
	21st to end	Night	30% 19% 29% 18% 3 1	1045

Page generated at 2026-05-29 02:53:24. Version ac07

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