Wachapreague
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wachapreague clear sky chart from 2005-11-06 to 2026-02-16.

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	12% 6% 2 6% 4 4 4 4 6% 8% 43%	130695
	Night	13% 7% 3 7% 4 4 4 4 5% 7% 42%	130147
Transparency	Day	37% 5% 14% 24% 16% 3	134284
	Night	40% 5% 11% 24% 17% 4	134628
Seeing	Day	15% 5% 18% 30% 24% 7%	16826
	Night	16% 7% 23% 31% 19% 4	26396

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	12% 5% 2 6% 3 3 4 3 5% 6% 51%	4661
	11th to 20th	Day	12% 6% 3 7% 3 3 3 2 4 5% 53%	5280
	21st to end	Day	12% 7% 3 8% 5% 4 4 3 5% 5% 44%	5780
February	1st to 10th	Day	12% 8% 2 7% 5% 4 5% 4 7% 8% 39%	1890
	11th to 20th	Day	19% 8% 2 6% 4 3 3 3 4 6% 42%	1989
	21st to end	Day	17% 9% 2 6% 5% 4 3 3 5% 5% 40%	1650
March	1st to 10th	Day	17% 6% 2 7% 4 4 4 3 5% 7% 40%	4614
	11th to 20th	Day	9% 5% 3 6% 4 3 3 4 5% 7% 51%	4980
	21st to end	Day	13% 7% 2 6% 4 3 4 3 5% 7% 46%	5730
April	1st to 10th	Day	11% 6% 2 6% 3 4 4 4 6% 7% 47%	2400
	11th to 20th	Day	10% 5% 2 5% 3 4 4 3 5% 8% 49%	2374
	21st to end	Day	12% 6% 2 5% 4 4 4 3 6% 7% 48%	2400
May	1st to 10th	Day	12% 8% 3 8% 5% 4 5% 5% 7% 10% 33%	5405
	11th to 20th	Day	15% 8% 3 8% 5% 5% 5% 4 6% 8% 33%	6213
	21st to end	Day	13% 5% 2 6% 4 5% 5% 4 6% 10% 38%	6934
June	1st to 10th	Day	9% 5% 2 5% 3 4 4 4 9% 10% 45%	2800
	11th to 20th	Day	9% 5% 2 4 4 4 4 4 7% 11% 46%	2800
	21st to end	Day	6% 4 2 5% 5% 4 5% 4 6% 12% 46%	2800
July	1st to 10th	Day	7% 4 2 5% 4 4 5% 5% 7% 12% 45%	6360
	11th to 20th	Day	10% 6% 3 7% 6% 6% 5% 5% 8% 11% 34%	6315
	21st to end	Day	6% 5% 2 6% 5% 5% 5% 5% 8% 11% 43%	6424
August	1st to 10th	Day	13% 8% 3 7% 5% 5% 4 4 6% 11% 34%	4152
	11th to 20th	Day	8% 6% 2 6% 5% 6% 6% 4 7% 9% 41%	3850
	21st to end	Day	8% 4 1 5% 4 3 5% 4 6% 11% 48%	4312
September	1st to 10th	Day	14% 5% 2 5% 3 4 4 4 5% 8% 46%	2400
	11th to 20th	Day	11% 5% 3 7% 5% 4 4 3 6% 7% 44%	2385
	21st to end	Day	19% 7% 2 7% 4 4 4 4 4 7% 38%	2180
October	1st to 10th	Day	13% 6% 1 6% 5% 4 5% 3 4 6% 48%	2000
	11th to 20th	Day	15% 5% 2 6% 3 3 3 3 4 5% 51%	2000
	21st to end	Day	14% 5% 2 6% 4 4 4 3 4 6% 48%	2200
November	1st to 10th	Day	12% 6% 2 6% 4 3 4 3 5% 7% 47%	1881
	11th to 20th	Day	11% 8% 2 5% 4 4 3 4 5% 8% 48%	1890
	21st to end	Day	15% 5% 2 5% 4 3 5% 3 5% 7% 48%	1848
December	1st to 10th	Day	12% 8% 2 5% 4 4 3 4 5% 5% 49%	2680
	11th to 20th	Day	16% 9% 3 7% 4 3 3 2 4 6% 44%	3070
	21st to end	Day	11% 7% 2 5% 4 4 4 3 5% 7% 47%	4048
January	1st to 10th	Night	11% 6% 3 5% 4 4 4 4 5% 7% 45%	8215
	11th to 20th	Night	12% 6% 3 7% 4 3 3 2 3 4 51%	7680
	21st to end	Night	14% 7% 3 8% 4 4 4 3 4 5% 45%	8401
February	1st to 10th	Night	16% 8% 3 6% 4 3 3 3 5% 6% 42%	2730
	11th to 20th	Night	19% 8% 2 4 4 3 4 3 5% 7% 41%	2405
	21st to end	Night	17% 8% 2 6% 4 3 4 3 4 5% 45%	1980
March	1st to 10th	Night	17% 7% 2 6% 3 3 4 3 5% 6% 44%	5236
	11th to 20th	Night	12% 7% 3 6% 4 4 4 3 4 7% 47%	4980
	21st to end	Night	14% 8% 2 5% 4 3 3 3 5% 6% 46%	5202
April	1st to 10th	Night	14% 8% 3 7% 5% 4 4 4 6% 7% 39%	2000
	11th to 20th	Night	11% 5% 2 5% 4 4 4 3 6% 7% 50%	1975
	21st to end	Night	13% 6% 1 5% 4 4 4 4 5% 8% 44%	2000
May	1st to 10th	Night	14% 7% 3 9% 5% 6% 5% 4 7% 8% 31%	4490
	11th to 20th	Night	19% 9% 3 7% 5% 4 4 4 6% 9% 31%	3707
	21st to end	Night	15% 8% 4 9% 4 4 4 4 6% 8% 34%	3920
June	1st to 10th	Night	12% 7% 2 7% 5% 5% 5% 5% 6% 10% 38%	1600
	11th to 20th	Night	8% 5% 2 8% 4 5% 6% 5% 6% 10% 40%	1600
	21st to end	Night	7% 5% 2 6% 5% 5% 5% 4 6% 11% 44%	1600
July	1st to 10th	Night	8% 5% 2 7% 5% 5% 7% 5% 8% 10% 37%	3598
	11th to 20th	Night	8% 7% 3 7% 6% 6% 6% 4 8% 13% 32%	3637
	21st to end	Night	9% 6% 3 7% 5% 5% 5% 5% 8% 10% 38%	4427
August	1st to 10th	Night	14% 9% 4 9% 4 5% 5% 4 6% 9% 31%	2964
	11th to 20th	Night	10% 5% 3 8% 5% 5% 5% 4 5% 9% 40%	3197
	21st to end	Night	8% 5% 2 6% 4 4 4 3 6% 10% 47%	3586
September	1st to 10th	Night	11% 5% 3 6% 4 4 5% 4 5% 7% 47%	2000
	11th to 20th	Night	11% 6% 2 7% 4 5% 4 4 6% 7% 44%	2014
	21st to end	Night	19% 7% 3 8% 4 5% 4 4 6% 7% 34%	2215
October	1st to 10th	Night	13% 6% 3 5% 4 3 4 3 5% 6% 47%	2400
	11th to 20th	Night	16% 5% 2 5% 4 3 4 3 4 5% 48%	2400
	21st to end	Night	15% 6% 2 5% 4 4 3 3 4 7% 47%	2640
November	1st to 10th	Night	14% 6% 2 6% 4 3 4 3 5% 6% 48%	2636
	11th to 20th	Night	14% 7% 3 6% 4 4 4 4 5% 7% 44%	2730
	21st to end	Night	11% 5% 2 5% 4 4 4 3 6% 7% 49%	2767
December	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 5% 7% 49%	4720
	11th to 20th	Night	17% 8% 4 8% 4 4 4 4 5% 7% 36%	5345
	21st to end	Night	11% 8% 3 6% 4 4 4 4 5% 7% 44%	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	35% 3 11% 27% 20% 5%	4662
	11th to 20th	Day	36% 2 6% 22% 28% 6%	5280
	21st to end	Day	43% 3 9% 30% 14% 2	5780
February	1st to 10th	Day	42% 4 12% 25% 14% 3	1890
	11th to 20th	Day	45% 3 8% 22% 17% 5%	1998
	21st to end	Day	46% 4 10% 20% 16% 4	1650
March	1st to 10th	Day	43% 4 9% 19% 20% 5%	4614
	11th to 20th	Day	33% 4 9% 25% 22% 7%	4980
	21st to end	Day	39% 4 12% 19% 19% 6%	5730
April	1st to 10th	Day	36% 5% 12% 23% 20% 5%	2400
	11th to 20th	Day	33% 4 12% 26% 20% 5%	2374
	21st to end	Day	36% 5% 12% 26% 18% 4	2400
May	1st to 10th	Day	46% 8% 17% 19% 10% 1	5437
	11th to 20th	Day	47% 6% 14% 24% 8% 1	6217
	21st to end	Day	41% 7% 14% 24% 12% 2	6949
June	1st to 10th	Day	32% 7% 17% 27% 15% 2	2800
	11th to 20th	Day	32% 7% 17% 28% 14% 2	2800
	21st to end	Day	30% 7% 17% 28% 16% 1	2800
July	1st to 10th	Day	30% 9% 25% 22% 12% 2	6290
	11th to 20th	Day	42% 11% 25% 19% 4	6240
	21st to end	Day	33% 8% 18% 24% 16%	6240
August	1st to 10th	Day	42% 7% 20% 24% 6%	4139
	11th to 20th	Day	36% 7% 18% 29% 9%	3886
	21st to end	Day	29% 6% 16% 30% 18% 2	4312
September	1st to 10th	Day	37% 5% 17% 22% 17% 3	2400
	11th to 20th	Day	39% 5% 10% 26% 19% 2	2385
	21st to end	Day	46% 5% 10% 20% 16% 2	2180
October	1st to 10th	Day	31% 6% 9% 27% 24% 5%	3260
	11th to 20th	Day	27% 3 7% 23% 32% 8%	3240
	21st to end	Day	26% 4 9% 28% 24% 9%	3538
November	1st to 10th	Day	36% 4 10% 29% 17% 4	1881
	11th to 20th	Day	36% 4 13% 22% 21% 4	1890
	21st to end	Day	37% 4 10% 27% 19% 3	1848
December	1st to 10th	Day	38% 4 11% 30% 16% 2	2680
	11th to 20th	Day	44% 3 13% 21% 16% 3	3066
	21st to end	Day	36% 5% 15% 28% 15% 1	4048
January	1st to 10th	Night	39% 3 10% 24% 20% 4	8216
	11th to 20th	Night	37% 4 5% 24% 24% 6%	7680
	21st to end	Night	41% 4 8% 30% 14% 3	8401
February	1st to 10th	Night	44% 3 11% 24% 17% 2	2730
	11th to 20th	Night	44% 2 7% 25% 17% 4	2407
	21st to end	Night	43% 3 8% 23% 18% 6%	1980
March	1st to 10th	Night	41% 4 8% 22% 18% 8%	5236
	11th to 20th	Night	38% 4 7% 23% 21% 7%	4980
	21st to end	Night	40% 4 8% 24% 17% 7%	5202
April	1st to 10th	Night	43% 5% 11% 19% 20% 4	2000
	11th to 20th	Night	35% 4 10% 24% 22% 5%	1975
	21st to end	Night	38% 5% 12% 23% 18% 4	2000
May	1st to 10th	Night	48% 6% 16% 20% 8% 1	4520
	11th to 20th	Night	50% 6% 12% 23% 8% 1	3708
	21st to end	Night	48% 6% 11% 23% 12%	3927
June	1st to 10th	Night	42% 6% 12% 24% 15% 1	1600
	11th to 20th	Night	38% 6% 16% 23% 15% 1	1600
	21st to end	Night	32% 7% 17% 25% 16% 2	1600
July	1st to 10th	Night	39% 9% 18% 20% 12% 2	3560
	11th to 20th	Night	42% 10% 22% 20% 5% 1	3592
	21st to end	Night	40% 8% 14% 24% 15%	4297
August	1st to 10th	Night	48% 6% 18% 22% 6%	2953
	11th to 20th	Night	40% 6% 16% 26% 11%	3227
	21st to end	Night	32% 6% 11% 26% 24% 1	3586
September	1st to 10th	Night	36% 6% 16% 22% 16% 4	2000
	11th to 20th	Night	38% 5% 9% 27% 19% 2	2014
	21st to end	Night	49% 5% 11% 18% 15% 2	2215
October	1st to 10th	Night	35% 5% 11% 25% 23% 3	3920
	11th to 20th	Night	29% 3 7% 24% 28% 9%	3899
	21st to end	Night	25% 2 7% 31% 24% 11%	4252
November	1st to 10th	Night	38% 4 9% 26% 19% 4	2636
	11th to 20th	Night	41% 4 10% 21% 18% 5%	2730
	21st to end	Night	35% 3 11% 28% 20% 3	2767
December	1st to 10th	Night	35% 4 11% 28% 20% 2	4720
	11th to 20th	Night	48% 4 11% 20% 12% 4	5348
	21st to end	Night	39% 4 14% 27% 14% 1	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	20% 11% 29% 32% 8%	220
	11th to 20th	Day	16% 13% 36% 26% 9%	330
	21st to end	Day	19% 7% 32% 34% 8% 1	363
February	1st to 10th	Day	15% 11% 25% 37% 12%	330
	11th to 20th	Day	27% 11% 32% 25% 5%	507
	21st to end	Day	22% 7% 29% 34% 7% 1	414
March	1st to 10th	Day	17% 8% 29% 36% 8% 1	500
	11th to 20th	Day	17% 7% 28% 36% 11% 1	500
	21st to end	Day	15% 6% 31% 36% 11% 1	550
April	1st to 10th	Day	13% 8% 31% 33% 13% 2	500
	11th to 20th	Day	11% 4 25% 40% 17% 3	492
	21st to end	Day	15% 6% 20% 37% 19% 3	500
May	1st to 10th	Day	15% 5% 19% 36% 21% 3	503
	11th to 20th	Day	17% 3 17% 34% 24% 4	527
	21st to end	Day	17% 3 12% 28% 29% 11%	573
June	1st to 10th	Day	11% 2 9% 31% 37% 10%	530
	11th to 20th	Day	10% 2 9% 33% 36% 12%	530
	21st to end	Day	8% 2 10% 30% 38% 12%	530
July	1st to 10th	Day	11% 1 4 25% 42% 17%	525
	11th to 20th	Day	7% 2 2 24% 48% 16%	524
	21st to end	Day	10% 2 3 27% 47% 11%	576
August	1st to 10th	Day	11% 2 6% 30% 38% 13%	526
	11th to 20th	Day	11% 2 4 26% 38% 18%	519
	21st to end	Day	10% 2 7% 27% 37% 16%	583
September	1st to 10th	Day	15% 2 9% 26% 31% 17%	530
	11th to 20th	Day	14% 3 11% 27% 32% 13%	530
	21st to end	Day	25% 4 12% 28% 24% 7%	530
October	1st to 10th	Day	16% 4 10% 29% 28% 12%	530
	11th to 20th	Day	17% 6% 20% 30% 21% 6%	530
	21st to end	Day	17% 7% 22% 28% 19% 7%	583
November	1st to 10th	Day	15% 7% 26% 28% 19% 5%	441
	11th to 20th	Day	13% 13% 31% 29% 13% 2	430
	21st to end	Day	16% 13% 25% 25% 18% 2	388
December	1st to 10th	Day	23% 8% 27% 30% 11% 1	220
	11th to 20th	Day	20% 8% 29% 26% 15%	220
	21st to end	Day	17% 8% 29% 32% 12% 2	242
January	1st to 10th	Night	16% 16% 34% 27% 7%	840
	11th to 20th	Night	18% 15% 32% 27% 8%	840
	21st to end	Night	19% 12% 35% 30% 4	924
February	1st to 10th	Night	21% 8% 35% 31% 5%	840
	11th to 20th	Night	24% 13% 37% 23% 4	804
	21st to end	Night	21% 9% 31% 32% 5% 1	660
March	1st to 10th	Night	16% 9% 34% 31% 10%	800
	11th to 20th	Night	20% 8% 32% 31% 8% 2	800
	21st to end	Night	20% 6% 32% 34% 9%	880
April	1st to 10th	Night	17% 7% 35% 33% 8% 1	800
	11th to 20th	Night	14% 5% 27% 40% 14% 1	791
	21st to end	Night	15% 5% 25% 39% 15% 2	800
May	1st to 10th	Night	18% 6% 23% 37% 15% 2	800
	11th to 20th	Night	17% 4 19% 37% 21% 2	461
	21st to end	Night	15% 3 11% 33% 31% 7%	433
June	1st to 10th	Night	14% 3 12% 38% 31% 4	400
	11th to 20th	Night	8% 1 10% 44% 30% 7%	400
	21st to end	Night	8% 2 10% 39% 36% 5%	400
July	1st to 10th	Night	8% 1 7% 37% 40% 8%	390
	11th to 20th	Night	8% 3 3 26% 48% 11%	402
	21st to end	Night	9% 3 7% 34% 39% 8%	657
August	1st to 10th	Night	11% 3 5% 36% 38% 8%	620
	11th to 20th	Night	13% 3 6% 32% 39% 9%	790
	21st to end	Night	10% 1 7% 31% 40% 11%	880
September	1st to 10th	Night	14% 3 8% 29% 36% 11%	800
	11th to 20th	Night	14% 2 9% 28% 38% 10%	800
	21st to end	Night	22% 4 12% 30% 28% 4	800
October	1st to 10th	Night	17% 5% 16% 28% 28% 8%	800
	11th to 20th	Night	19% 6% 22% 31% 20% 3	800
	21st to end	Night	18% 8% 21% 31% 16% 5%	880
November	1st to 10th	Night	17% 8% 22% 31% 17% 5%	820
	11th to 20th	Night	18% 10% 29% 30% 12% 2	840
	21st to end	Night	14% 12% 28% 29% 15% 2	840
December	1st to 10th	Night	21% 9% 35% 24% 10% 1	840
	11th to 20th	Night	18% 10% 36% 26% 9%	840
	21st to end	Night	17% 11% 31% 31% 10%	924

Page generated at 2026-02-13 01:42:14. Version ac07

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