Powhatan Wildlife Management Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Powhatan Wildlife Management Area clear sky chart from 2005-11-06 to 2025-08-05.

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	13% 6% 2 6% 4 4 4 4 6% 8% 43%	125282
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 44%	122747
Transparency	Day	37% 7% 12% 22% 18% 4	128887
	Night	38% 6% 10% 22% 19% 5%	127211
Seeing	Day	19% 11% 26% 24% 15% 5%	16068
	Night	17% 10% 27% 31% 13% 1	25785

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	15% 5% 2 4 3 3 4 3 4 5% 53%	4056
	11th to 20th	Day	14% 7% 2 4 3 3 3 2 4 4 52%	4060
	21st to end	Day	15% 7% 2 7% 4 3 3 3 4 5% 46%	4466
February	1st to 10th	Day	13% 7% 3 7% 4 5% 5% 4 6% 7% 41%	1800
	11th to 20th	Day	22% 7% 2 4 3 4 3 3 5% 5% 42%	1788
	21st to end	Day	19% 6% 3 7% 4 4 4 4 5% 7% 38%	1695
March	1st to 10th	Day	17% 7% 2 7% 4 5% 5% 3 5% 6% 38%	4935
	11th to 20th	Day	11% 5% 2 5% 3 3 4 3 5% 7% 52%	4980
	21st to end	Day	17% 6% 2 6% 5% 4 4 3 5% 6% 42%	5465
April	1st to 10th	Day	11% 6% 2 5% 3 3 4 4 5% 7% 50%	2385
	11th to 20th	Day	12% 6% 3 5% 4 4 3 3 5% 7% 49%	2374
	21st to end	Day	15% 6% 2 6% 4 4 4 3 5% 7% 43%	2400
May	1st to 10th	Day	13% 7% 2 7% 5% 5% 6% 5% 7% 9% 33%	5789
	11th to 20th	Day	20% 7% 3 7% 5% 5% 5% 4 6% 8% 31%	5861
	21st to end	Day	15% 5% 2 5% 4 4 4 4 5% 9% 43%	6816
June	1st to 10th	Day	10% 4 2 5% 4 4 5% 5% 7% 10% 44%	2800
	11th to 20th	Day	10% 5% 2 6% 5% 4 5% 4 8% 9% 42%	2800
	21st to end	Day	7% 5% 2 5% 5% 5% 6% 5% 7% 10% 44%	2800
July	1st to 10th	Day	7% 5% 2 6% 4 5% 5% 4 8% 11% 42%	6096
	11th to 20th	Day	10% 6% 2 7% 5% 5% 6% 6% 10% 13% 30%	5900
	21st to end	Day	8% 5% 2 6% 5% 5% 6% 5% 8% 11% 40%	6424
August	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 5% 8% 10% 30%	4156
	11th to 20th	Day	9% 5% 2 7% 5% 5% 6% 5% 7% 11% 38%	3893
	21st to end	Day	9% 4 2 5% 3 3 5% 4 6% 11% 49%	4180
September	1st to 10th	Day	12% 6% 2 6% 4 5% 4 4 5% 7% 46%	2280
	11th to 20th	Day	13% 6% 2 5% 4 4 4 3 6% 8% 44%	2245
	21st to end	Day	21% 7% 2 8% 4 3 3 3 5% 7% 38%	2000
October	1st to 10th	Day	16% 6% 2 6% 3 4 3 3 4 6% 48%	1900
	11th to 20th	Day	16% 4 2 4 3 4 2 3 4 5% 53%	1900
	21st to end	Day	13% 5% 2 5% 3 3 3 3 3 6% 54%	2090
November	1st to 10th	Day	13% 5% 2 4 3 3 3 3 4 5% 54%	1957
	11th to 20th	Day	15% 5% 2 5% 4 3 3 2 5% 6% 49%	1813
	21st to end	Day	14% 5% 2 5% 3 3 3 3 4 6% 52%	1600
December	1st to 10th	Day	12% 5% 2 5% 3 3 4 3 5% 6% 51%	2600
	11th to 20th	Day	19% 6% 2 5% 3 3 4 2 4 6% 47%	2990
	21st to end	Day	16% 7% 2 6% 4 4 4 4 5% 7% 42%	3988
January	1st to 10th	Night	13% 6% 2 4 3 3 3 3 4 5% 54%	5889
	11th to 20th	Night	14% 6% 2 4 3 2 3 3 3 4 55%	5900
	21st to end	Night	17% 7% 2 5% 3 3 3 3 4 5% 50%	6490
February	1st to 10th	Night	15% 7% 2 5% 5% 3 4 4 5% 7% 43%	2600
	11th to 20th	Night	20% 7% 2 5% 4 4 4 3 4 6% 43%	2497
	21st to end	Night	16% 7% 2 5% 4 3 3 3 5% 5% 46%	1930
March	1st to 10th	Night	16% 5% 2 5% 3 3 4 3 5% 6% 47%	4918
	11th to 20th	Night	12% 4 2 5% 3 3 3 3 5% 7% 52%	4980
	21st to end	Night	13% 6% 2 6% 4 4 4 3 5% 6% 47%	5467
April	1st to 10th	Night	14% 7% 3 6% 4 4 4 4 4 6% 46%	2013
	11th to 20th	Night	11% 6% 2 4 4 4 4 3 6% 8% 48%	1975
	21st to end	Night	14% 7% 2 5% 4 4 4 4 6% 6% 46%	2000
May	1st to 10th	Night	14% 7% 3 8% 5% 5% 5% 4 6% 9% 34%	4135
	11th to 20th	Night	21% 8% 3 7% 5% 4 4 4 5% 7% 33%	4032
	21st to end	Night	15% 7% 2 5% 4 4 4 4 7% 9% 39%	4020
June	1st to 10th	Night	11% 5% 2 6% 4 5% 5% 5% 7% 9% 43%	1600
	11th to 20th	Night	9% 6% 3 6% 4 5% 5% 4 7% 11% 40%	1600
	21st to end	Night	8% 6% 1 5% 5% 4 5% 4 7% 11% 44%	1600
July	1st to 10th	Night	9% 6% 3 7% 5% 5% 6% 5% 7% 9% 38%	3843
	11th to 20th	Night	11% 8% 3 8% 6% 6% 6% 6% 8% 11% 27%	4057
	21st to end	Night	8% 6% 2 9% 6% 6% 7% 6% 7% 8% 33%	4427
August	1st to 10th	Night	16% 7% 3 8% 4 5% 5% 5% 7% 10% 31%	2861
	11th to 20th	Night	9% 5% 3 8% 4 5% 6% 5% 7% 10% 37%	2903
	21st to end	Night	8% 5% 2 6% 5% 5% 4 4 6% 8% 45%	3476
September	1st to 10th	Night	13% 6% 2 5% 5% 4 5% 3 5% 8% 44%	1900
	11th to 20th	Night	12% 6% 2 5% 4 5% 5% 4 5% 7% 46%	1931
	21st to end	Night	22% 8% 2 5% 4 4 4 4 5% 5% 38%	2179
October	1st to 10th	Night	16% 6% 3 5% 3 4 4 3 5% 5% 46%	2280
	11th to 20th	Night	15% 5% 1 5% 4 3 3 3 4 7% 49%	2280
	21st to end	Night	12% 4 2 5% 3 4 3 3 4 6% 52%	2508
November	1st to 10th	Night	12% 7% 2 5% 4 4 4 3 5% 5% 51%	2341
	11th to 20th	Night	14% 6% 2 5% 3 3 4 3 4 5% 50%	2580
	21st to end	Night	13% 4 2 4 3 3 5% 4 5% 7% 51%	2800
December	1st to 10th	Night	10% 5% 2 4 3 3 4 3 5% 6% 55%	4580
	11th to 20th	Night	20% 8% 2 5% 4 4 4 3 5% 5% 40%	5205
	21st to end	Night	15% 7% 2 5% 4 3 4 4 5% 7% 44%	6950

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	34% 3 5% 25% 23% 10%	4057
	11th to 20th	Day	35% 4 5% 19% 25% 11%	4060
	21st to end	Day	41% 4 8% 25% 18% 4	4466
February	1st to 10th	Day	42% 5% 9% 26% 14% 3	1800
	11th to 20th	Day	43% 5% 6% 21% 19% 5%	1797
	21st to end	Day	46% 5% 11% 15% 18% 5%	1695
March	1st to 10th	Day	44% 6% 8% 18% 16% 9%	4935
	11th to 20th	Day	31% 5% 9% 23% 23% 10%	4980
	21st to end	Day	43% 6% 9% 18% 18% 6%	5465
April	1st to 10th	Day	33% 5% 12% 22% 19% 8%	2385
	11th to 20th	Day	35% 5% 11% 22% 21% 6%	2374
	21st to end	Day	40% 6% 11% 22% 16% 5%	2400
May	1st to 10th	Day	43% 10% 15% 19% 11% 1	5823
	11th to 20th	Day	48% 7% 12% 19% 12% 1	5865
	21st to end	Day	37% 7% 15% 21% 19% 2	6831
June	1st to 10th	Day	33% 9% 17% 25% 16% 1	2800
	11th to 20th	Day	35% 9% 16% 21% 16% 2	2800
	21st to end	Day	32% 10% 16% 25% 16% 2	2800
July	1st to 10th	Day	33% 10% 22% 18% 14% 4	6031
	11th to 20th	Day	40% 12% 23% 18% 6% 1	5831
	21st to end	Day	35% 9% 15% 23% 18%	6240
August	1st to 10th	Day	47% 8% 17% 21% 7% 1	4143
	11th to 20th	Day	36% 10% 18% 24% 12% 1	3932
	21st to end	Day	29% 7% 17% 28% 17% 2	4180
September	1st to 10th	Day	37% 7% 13% 17% 22% 4	2280
	11th to 20th	Day	38% 7% 8% 24% 19% 4	2245
	21st to end	Day	47% 5% 9% 19% 16% 4	2000
October	1st to 10th	Day	35% 4 8% 18% 29% 5%	3160
	11th to 20th	Day	23% 4 6% 21% 32% 14%	3140
	21st to end	Day	20% 3 10% 29% 26% 12%	3428
November	1st to 10th	Day	32% 4 8% 24% 26% 5%	1957
	11th to 20th	Day	36% 3 9% 21% 22% 8%	1813
	21st to end	Day	34% 5% 8% 23% 25% 5%	1600
December	1st to 10th	Day	34% 5% 9% 27% 19% 8%	2600
	11th to 20th	Day	40% 4 12% 24% 16% 5%	2986
	21st to end	Day	41% 6% 12% 25% 16% 1	3988
January	1st to 10th	Night	33% 3 6% 20% 26% 11%	5889
	11th to 20th	Night	33% 3 5% 20% 29% 9%	5900
	21st to end	Night	37% 4 6% 27% 20% 6%	6490
February	1st to 10th	Night	40% 5% 11% 23% 18% 3	2600
	11th to 20th	Night	44% 3 8% 19% 19% 7%	2499
	21st to end	Night	41% 4 8% 22% 18% 8%	1930
March	1st to 10th	Night	37% 4 8% 22% 21% 9%	4918
	11th to 20th	Night	30% 5% 8% 19% 27% 11%	4980
	21st to end	Night	38% 5% 8% 22% 21% 6%	5467
April	1st to 10th	Night	40% 6% 9% 17% 22% 7%	2013
	11th to 20th	Night	34% 5% 12% 22% 22% 6%	1975
	21st to end	Night	37% 6% 12% 23% 17% 5%	2000
May	1st to 10th	Night	45% 9% 16% 18% 11% 2	4163
	11th to 20th	Night	50% 7% 12% 21% 9% 1	4033
	21st to end	Night	40% 8% 14% 24% 12% 1	4027
June	1st to 10th	Night	36% 9% 13% 26% 16% 1	1600
	11th to 20th	Night	36% 10% 17% 21% 15% 2	1600
	21st to end	Night	32% 8% 15% 23% 18% 4	1600
July	1st to 10th	Night	40% 11% 18% 15% 13% 2	3800
	11th to 20th	Night	48% 14% 18% 15% 5% 1	4006
	21st to end	Night	44% 11% 13% 19% 14%	4297
August	1st to 10th	Night	47% 8% 16% 22% 6%	2850
	11th to 20th	Night	38% 9% 18% 24% 11%	2930
	21st to end	Night	35% 8% 12% 30% 14% 2	3476
September	1st to 10th	Night	39% 7% 14% 17% 17% 6%	1900
	11th to 20th	Night	38% 6% 10% 22% 22% 3	1931
	21st to end	Night	48% 6% 10% 18% 15% 3	2179
October	1st to 10th	Night	39% 6% 10% 18% 22% 5%	3800
	11th to 20th	Night	25% 3 8% 21% 31% 11%	3779
	21st to end	Night	21% 3 7% 31% 26% 13%	4120
November	1st to 10th	Night	35% 5% 9% 21% 25% 5%	2341
	11th to 20th	Night	36% 4 8% 19% 23% 9%	2580
	21st to end	Night	33% 5% 9% 25% 23% 6%	2800
December	1st to 10th	Night	30% 4 8% 28% 25% 5%	4580
	11th to 20th	Night	46% 4 10% 19% 15% 7%	5208
	21st to end	Night	38% 6% 11% 27% 16% 2	6950

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	29% 23% 26% 17% 5%	300
	11th to 20th	Day	27% 27% 32% 12% 2	300
	21st to end	Day	27% 20% 38% 12% 3	330
February	1st to 10th	Day	24% 22% 37% 13% 3	300
	11th to 20th	Day	39% 23% 28% 7% 2	335
	21st to end	Day	29% 17% 31% 19% 3	414
March	1st to 10th	Day	22% 22% 31% 20% 5%	500
	11th to 20th	Day	23% 21% 33% 17% 5% 1	500
	21st to end	Day	25% 18% 35% 16% 6% 1	550
April	1st to 10th	Day	23% 21% 30% 18% 7% 1	500
	11th to 20th	Day	21% 13% 34% 20% 8% 4	492
	21st to end	Day	22% 12% 35% 21% 8% 2	500
May	1st to 10th	Day	22% 13% 33% 21% 8% 3	503
	11th to 20th	Day	23% 9% 28% 25% 12% 3	527
	21st to end	Day	19% 7% 22% 28% 19% 5%	573
June	1st to 10th	Day	10% 6% 28% 28% 22% 6%	530
	11th to 20th	Day	12% 6% 23% 32% 19% 8%	530
	21st to end	Day	10% 5% 22% 33% 23% 7%	530
July	1st to 10th	Day	10% 4 18% 31% 27% 10%	525
	11th to 20th	Day	6% 3 17% 34% 28% 13%	524
	21st to end	Day	9% 4 20% 31% 24% 11%	576
August	1st to 10th	Day	14% 4 22% 27% 26% 8%	502
	11th to 20th	Day	12% 3 15% 31% 27% 11%	479
	21st to end	Day	10% 3 15% 29% 27% 16%	539
September	1st to 10th	Day	15% 5% 18% 26% 22% 16%	490
	11th to 20th	Day	15% 4 16% 31% 22% 11%	490
	21st to end	Day	28% 8% 20% 27% 12% 5%	490
October	1st to 10th	Day	23% 5% 23% 24% 18% 8%	490
	11th to 20th	Day	17% 12% 21% 28% 20% 3	490
	21st to end	Day	15% 12% 32% 26% 11% 4	539
November	1st to 10th	Day	17% 10% 27% 28% 14% 4	495
	11th to 20th	Day	20% 11% 31% 25% 11% 2	398
	21st to end	Day	22% 18% 28% 23% 8% 3	200
December	1st to 10th	Day	23% 17% 38% 14% 7% 2	200
	11th to 20th	Day	25% 13% 31% 24% 7% 1	200
	21st to end	Day	29% 15% 29% 16% 10% 2	227
January	1st to 10th	Night	20% 19% 36% 22% 3	800
	11th to 20th	Night	22% 18% 31% 26% 3	800
	21st to end	Night	20% 15% 39% 23% 3	880
February	1st to 10th	Night	21% 14% 37% 25% 3	800
	11th to 20th	Night	26% 17% 37% 18% 2	783
	21st to end	Night	22% 16% 35% 23% 3	660
March	1st to 10th	Night	19% 16% 36% 27% 3	800
	11th to 20th	Night	22% 16% 35% 22% 6%	800
	21st to end	Night	18% 15% 40% 23% 5%	880
April	1st to 10th	Night	18% 17% 37% 24% 5%	800
	11th to 20th	Night	14% 14% 37% 27% 8% 1	791
	21st to end	Night	17% 8% 35% 33% 7%	800
May	1st to 10th	Night	17% 8% 32% 34% 8% 1	651
	11th to 20th	Night	18% 7% 25% 35% 14% 1	591
	21st to end	Night	15% 4 18% 39% 23% 2	482
June	1st to 10th	Night	10% 4 19% 46% 22% 1	400
	11th to 20th	Night	11% 3 19% 41% 23% 3	400
	21st to end	Night	8% 3 21% 44% 23% 1	400
July	1st to 10th	Night	13% 3 13% 39% 29% 3	487
	11th to 20th	Night	5% 2 11% 42% 36% 5%	582
	21st to end	Night	7% 2 16% 42% 28% 4	657
August	1st to 10th	Night	12% 2 13% 43% 27% 3	579
	11th to 20th	Night	13% 2 11% 41% 29% 4	630
	21st to end	Night	10% 3 14% 35% 33% 5%	836
September	1st to 10th	Night	15% 3 12% 36% 28% 6%	760
	11th to 20th	Night	14% 4 15% 33% 31% 4	760
	21st to end	Night	24% 5% 18% 34% 19% 1	760
October	1st to 10th	Night	18% 4 19% 33% 21% 4	760
	11th to 20th	Night	18% 8% 27% 29% 18% 1	760
	21st to end	Night	16% 9% 28% 31% 15% 1	836
November	1st to 10th	Night	16% 8% 27% 33% 13% 2	780
	11th to 20th	Night	17% 11% 30% 31% 10% 1	800
	21st to end	Night	15% 13% 32% 32% 9% 1	800
December	1st to 10th	Night	21% 12% 34% 25% 7%	800
	11th to 20th	Night	19% 11% 32% 32% 5%	800
	21st to end	Night	22% 14% 26% 33% 4	880

Page generated at 2025-08-02 01:32:23. Version ac07

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