Shenandoah County Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shenandoah County Park clear sky chart from 2005-11-06 to 2024-11-04.

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% 7% 2 6% 5% 5% 5% 4 6% 8% 40%	101111
	Night	13% 7% 2 6% 4 4 4 4 6% 7% 42%	97835
Transparency	Day	39% 8% 12% 23% 15% 3	104757
	Night	38% 8% 12% 23% 16% 3	102328
Seeing	Day	19% 14% 26% 23% 13% 4	14935
	Night	17% 12% 26% 31% 13% 1	24570

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% 8% 3 6% 5% 4 4 3 5% 6% 41%	2772
	11th to 20th	Day	12% 10% 4 8% 7% 5% 4 3 4 5% 37%	2840
	21st to end	Day	15% 10% 3 8% 5% 4 4 3 5% 6% 37%	3124
February	1st to 10th	Day	10% 10% 3 8% 5% 5% 5% 4 5% 6% 39%	1710
	11th to 20th	Day	15% 8% 2 7% 5% 4 6% 3 5% 6% 38%	1663
	21st to end	Day	15% 9% 3 6% 4 4 4 4 4 5% 41%	1603
March	1st to 10th	Day	19% 10% 3 7% 5% 5% 4 3 4 5% 36%	3435
	11th to 20th	Day	9% 6% 2 5% 4 4 4 3 5% 7% 51%	3480
	21st to end	Day	17% 8% 3 6% 4 4 4 4 5% 6% 38%	3815
April	1st to 10th	Day	10% 7% 2 6% 6% 5% 5% 4 6% 8% 41%	2253
	11th to 20th	Day	12% 7% 2 6% 4 3 4 3 5% 6% 47%	2254
	21st to end	Day	17% 7% 2 6% 5% 5% 4 3 6% 7% 39%	2332
May	1st to 10th	Day	19% 8% 3 7% 5% 5% 5% 5% 6% 8% 30%	4082
	11th to 20th	Day	23% 7% 2 7% 4 4 4 4 6% 8% 31%	4081
	21st to end	Day	10% 5% 2 6% 4 5% 6% 4 7% 9% 42%	4823
June	1st to 10th	Day	11% 6% 2 5% 5% 5% 6% 4 6% 9% 41%	2660
	11th to 20th	Day	9% 5% 2 6% 5% 6% 6% 4 7% 10% 39%	2660
	21st to end	Day	9% 5% 1 5% 5% 5% 6% 5% 7% 9% 43%	2660
July	1st to 10th	Day	5% 4 2 7% 5% 6% 6% 5% 8% 10% 43%	4385
	11th to 20th	Day	8% 5% 2 6% 6% 6% 5% 5% 8% 12% 38%	4120
	21st to end	Day	10% 8% 3 7% 6% 6% 6% 5% 6% 8% 35%	4466
August	1st to 10th	Day	14% 6% 3 7% 5% 6% 6% 5% 8% 9% 31%	4104
	11th to 20th	Day	8% 5% 2 7% 5% 6% 6% 5% 7% 9% 40%	3988
	21st to end	Day	9% 5% 2 6% 4 4 5% 4 6% 8% 47%	4180
September	1st to 10th	Day	14% 5% 2 6% 4 5% 5% 3 5% 6% 45%	2280
	11th to 20th	Day	13% 6% 2 5% 4 4 5% 4 5% 7% 46%	2214
	21st to end	Day	21% 6% 2 5% 5% 5% 4 3 5% 5% 39%	2019
October	1st to 10th	Day	16% 5% 2 6% 3 3 4 3 6% 7% 45%	1900
	11th to 20th	Day	14% 6% 2 6% 4 5% 3 3 5% 5% 48%	1900
	21st to end	Day	13% 6% 2 5% 4 4 4 3 5% 6% 49%	2090
November	1st to 10th	Day	10% 5% 2 5% 4 4 4 4 5% 6% 53%	1887
	11th to 20th	Day	12% 7% 2 5% 4 4 4 4 5% 6% 46%	1609
	21st to end	Day	14% 5% 2 5% 4 4 5% 4 4 6% 48%	1520
December	1st to 10th	Day	14% 9% 3 6% 4 5% 5% 4 5% 7% 38%	1520
	11th to 20th	Day	13% 8% 3 6% 5% 4 4 4 4 7% 43%	1910
	21st to end	Day	16% 7% 2 5% 5% 5% 6% 5% 7% 8% 34%	2772
January	1st to 10th	Night	10% 8% 3 6% 4 5% 5% 3 6% 7% 44%	4169
	11th to 20th	Night	15% 9% 3 5% 4 3 4 3 5% 6% 44%	4120
	21st to end	Night	16% 9% 3 7% 4 3 4 3 5% 5% 39%	4532
February	1st to 10th	Night	12% 8% 3 7% 5% 4 5% 4 6% 6% 41%	2470
	11th to 20th	Night	15% 9% 2 6% 4 4 5% 5% 6% 6% 39%	2403
	21st to end	Night	14% 10% 3 7% 5% 4 3 4 6% 6% 39%	1846
March	1st to 10th	Night	19% 7% 3 7% 4 4 4 4 5% 6% 36%	3418
	11th to 20th	Night	10% 6% 3 6% 4 4 4 4 5% 6% 49%	3480
	21st to end	Night	13% 6% 2 6% 4 3 4 3 4 6% 48%	3817
April	1st to 10th	Night	12% 8% 3 7% 5% 4 5% 4 6% 6% 40%	1925
	11th to 20th	Night	11% 5% 2 7% 5% 4 4 3 6% 8% 45%	1875
	21st to end	Night	15% 6% 2 5% 4 5% 4 4 5% 7% 44%	1862
May	1st to 10th	Night	20% 8% 3 8% 5% 5% 5% 3 5% 8% 31%	2813
	11th to 20th	Night	22% 8% 2 7% 5% 4 4 3 5% 5% 35%	2798
	21st to end	Night	10% 5% 2 5% 4 4 5% 5% 7% 9% 44%	2732
June	1st to 10th	Night	10% 5% 2 6% 4 5% 5% 4 7% 8% 46%	1520
	11th to 20th	Night	10% 6% 3 5% 4 5% 5% 5% 7% 9% 42%	1520
	21st to end	Night	8% 4 2 7% 5% 4 5% 4 9% 9% 43%	1520
July	1st to 10th	Night	6% 4 2 6% 5% 6% 6% 5% 8% 10% 42%	2571
	11th to 20th	Night	6% 5% 2 7% 6% 5% 6% 4 8% 11% 39%	2840
	21st to end	Night	8% 7% 3 8% 5% 5% 6% 5% 7% 9% 36%	3087
August	1st to 10th	Night	14% 5% 2 7% 5% 6% 6% 5% 6% 9% 35%	2825
	11th to 20th	Night	8% 6% 3 8% 6% 6% 5% 4 6% 9% 39%	2807
	21st to end	Night	10% 5% 2 5% 4 4 4 4 6% 9% 48%	3476
September	1st to 10th	Night	13% 5% 2 6% 4 4 4 3 5% 7% 46%	1900
	11th to 20th	Night	12% 4 2 6% 4 4 3 3 6% 8% 49%	1963
	21st to end	Night	18% 7% 2 6% 4 4 4 2 4 6% 43%	2161
October	1st to 10th	Night	18% 5% 2 5% 3 3 4 3 4 7% 46%	2280
	11th to 20th	Night	13% 5% 2 4 4 3 3 3 5% 6% 52%	2280
	21st to end	Night	14% 5% 2 3 3 4 3 3 5% 6% 52%	2508
November	1st to 10th	Night	9% 7% 2 5% 3 3 4 3 4 6% 52%	2264
	11th to 20th	Night	12% 7% 3 5% 4 3 4 3 6% 7% 47%	2564
	21st to end	Night	12% 5% 2 6% 4 4 5% 3 6% 7% 45%	2660
December	1st to 10th	Night	13% 8% 3 7% 5% 5% 4 4 5% 6% 41%	2660
	11th to 20th	Night	14% 6% 2 7% 5% 3 5% 4 5% 6% 43%	3285
	21st to end	Night	16% 7% 2 7% 4 5% 5% 4 7% 8% 36%	4884

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	41% 6% 10% 25% 15% 3	2773
	11th to 20th	Day	48% 7% 10% 16% 15% 5%	2840
	21st to end	Day	47% 7% 10% 21% 13% 2	3124
February	1st to 10th	Day	45% 7% 12% 21% 13% 2	1710
	11th to 20th	Day	45% 6% 11% 21% 16% 2	1672
	21st to end	Day	44% 6% 12% 18% 15% 4	1603
March	1st to 10th	Day	49% 6% 9% 19% 13% 3	3435
	11th to 20th	Day	32% 7% 8% 28% 21% 3	3480
	21st to end	Day	45% 9% 11% 19% 14% 3	3815
April	1st to 10th	Day	39% 9% 12% 18% 16% 6%	2253
	11th to 20th	Day	38% 7% 10% 21% 20% 5%	2254
	21st to end	Day	43% 8% 11% 20% 14% 4	2332
May	1st to 10th	Day	49% 10% 11% 20% 9% 1	4120
	11th to 20th	Day	49% 9% 11% 23% 7% 1	4085
	21st to end	Day	34% 12% 15% 21% 17% 2	4837
June	1st to 10th	Day	38% 10% 13% 23% 15% 1	2660
	11th to 20th	Day	38% 12% 15% 20% 13% 2	2660
	21st to end	Day	35% 11% 15% 24% 14% 2	2660
July	1st to 10th	Day	34% 11% 18% 22% 10% 5%	4316
	11th to 20th	Day	36% 10% 15% 28% 9% 1	4051
	21st to end	Day	44% 9% 9% 23% 15% 1	4324
August	1st to 10th	Day	45% 10% 16% 22% 7%	4091
	11th to 20th	Day	37% 10% 12% 26% 14% 1	4027
	21st to end	Day	33% 9% 15% 27% 15% 1	4180
September	1st to 10th	Day	39% 8% 13% 16% 20% 4	2280
	11th to 20th	Day	36% 7% 10% 25% 18% 3	2214
	21st to end	Day	47% 6% 9% 20% 16% 2	2019
October	1st to 10th	Day	32% 7% 9% 20% 27% 5%	3160
	11th to 20th	Day	27% 5% 8% 28% 22% 10%	3140
	21st to end	Day	25% 4 10% 29% 28% 5%	3428
November	1st to 10th	Day	32% 6% 11% 24% 23% 4	1887
	11th to 20th	Day	37% 6% 11% 19% 22% 5%	1609
	21st to end	Day	37% 5% 12% 26% 18% 2	1520
December	1st to 10th	Day	45% 7% 12% 22% 12% 2	1520
	11th to 20th	Day	39% 6% 13% 29% 11% 4	1906
	21st to end	Day	42% 8% 16% 22% 10% 1	2772
January	1st to 10th	Night	36% 8% 12% 24% 18% 3	4169
	11th to 20th	Night	41% 6% 11% 23% 15% 4	4120
	21st to end	Night	44% 7% 9% 25% 13% 1	4532
February	1st to 10th	Night	42% 7% 12% 24% 14% 1	2470
	11th to 20th	Night	44% 7% 9% 21% 15% 4	2405
	21st to end	Night	46% 6% 11% 20% 12% 5%	1846
March	1st to 10th	Night	45% 8% 11% 24% 10% 2	3418
	11th to 20th	Night	32% 8% 12% 26% 20% 2	3480
	21st to end	Night	35% 8% 10% 24% 19% 3	3817
April	1st to 10th	Night	41% 9% 11% 20% 17% 3	1925
	11th to 20th	Night	36% 9% 11% 21% 18% 5%	1875
	21st to end	Night	39% 8% 11% 26% 13% 3	1862
May	1st to 10th	Night	50% 9% 11% 18% 10% 2	2840
	11th to 20th	Night	48% 10% 11% 22% 8% 1	2799
	21st to end	Night	32% 12% 17% 27% 9% 4	2739
June	1st to 10th	Night	34% 11% 12% 28% 14% 2	1520
	11th to 20th	Night	36% 11% 15% 24% 13% 1	1520
	21st to end	Night	33% 9% 16% 23% 16% 2	1520
July	1st to 10th	Night	33% 12% 22% 17% 13% 3	2530
	11th to 20th	Night	37% 11% 19% 23% 9% 1	2786
	21st to end	Night	39% 12% 15% 20% 13%	2988
August	1st to 10th	Night	43% 9% 16% 24% 7%	2814
	11th to 20th	Night	39% 10% 12% 24% 15%	2834
	21st to end	Night	33% 8% 15% 30% 13% 1	3476
September	1st to 10th	Night	38% 8% 12% 19% 18% 4	1900
	11th to 20th	Night	32% 7% 13% 27% 19% 2	1963
	21st to end	Night	43% 6% 11% 21% 17% 2	2161
October	1st to 10th	Night	38% 7% 10% 21% 21% 3	3800
	11th to 20th	Night	24% 5% 11% 23% 31% 7%	3779
	21st to end	Night	22% 4 10% 32% 27% 5%	4120
November	1st to 10th	Night	32% 6% 11% 24% 22% 5%	2264
	11th to 20th	Night	36% 6% 9% 24% 21% 5%	2564
	21st to end	Night	38% 6% 12% 23% 18% 3	2660
December	1st to 10th	Night	45% 6% 11% 24% 12% 2	2660
	11th to 20th	Night	40% 7% 11% 22% 17% 3	3288
	21st to end	Night	42% 8% 17% 19% 13% 1	4884

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	31% 29% 23% 13% 3	252
	11th to 20th	Day	32% 26% 29% 11% 3	270
	21st to end	Day	29% 27% 30% 11% 2	297
February	1st to 10th	Day	27% 29% 31% 11% 1	270
	11th to 20th	Day	41% 29% 26% 4	270
	21st to end	Day	33% 23% 28% 15% 2	363
March	1st to 10th	Day	27% 24% 25% 21% 3	460
	11th to 20th	Day	28% 23% 27% 15% 6% 1	460
	21st to end	Day	24% 23% 30% 17% 4 1	506
April	1st to 10th	Day	23% 25% 27% 18% 6% 1	460
	11th to 20th	Day	19% 20% 29% 20% 9% 4	452
	21st to end	Day	25% 16% 31% 17% 9% 1	460
May	1st to 10th	Day	24% 18% 27% 16% 11% 3	463
	11th to 20th	Day	22% 15% 29% 20% 11% 3	487
	21st to end	Day	17% 8% 27% 26% 18% 5%	529
June	1st to 10th	Day	15% 11% 27% 26% 17% 4	490
	11th to 20th	Day	14% 8% 29% 27% 16% 6%	490
	21st to end	Day	11% 9% 30% 29% 17% 3	490
July	1st to 10th	Day	9% 5% 23% 33% 22% 9%	485
	11th to 20th	Day	6% 4 22% 33% 26% 8%	484
	21st to end	Day	13% 5% 21% 33% 20% 8%	532
August	1st to 10th	Day	10% 7% 24% 25% 23% 10%	486
	11th to 20th	Day	11% 3 24% 30% 22% 10%	479
	21st to end	Day	8% 4 22% 29% 24% 13%	539
September	1st to 10th	Day	16% 8% 19% 24% 22% 11%	490
	11th to 20th	Day	14% 5% 21% 28% 22% 10%	490
	21st to end	Day	28% 10% 22% 23% 14% 4	490
October	1st to 10th	Day	18% 8% 21% 29% 19% 4	490
	11th to 20th	Day	18% 14% 27% 25% 13% 2	490
	21st to end	Day	15% 19% 32% 22% 9% 3	539
November	1st to 10th	Day	19% 12% 30% 24% 11% 3	467
	11th to 20th	Day	20% 18% 29% 22% 9% 1	267
	21st to end	Day	24% 17% 36% 18% 4	180
December	1st to 10th	Day	24% 24% 34% 12% 4 1	180
	11th to 20th	Day	25% 23% 29% 17% 6%	180
	21st to end	Day	22% 21% 31% 20% 6% 1	198
January	1st to 10th	Night	19% 21% 34% 22% 4	760
	11th to 20th	Night	22% 19% 29% 26% 3	760
	21st to end	Night	19% 18% 38% 23% 1	836
February	1st to 10th	Night	17% 19% 33% 29% 2	760
	11th to 20th	Night	26% 25% 31% 17% 1	743
	21st to end	Night	25% 19% 35% 19% 2	628
March	1st to 10th	Night	20% 18% 36% 23% 4	760
	11th to 20th	Night	25% 21% 28% 21% 5% 1	760
	21st to end	Night	18% 19% 35% 22% 5% 1	836
April	1st to 10th	Night	17% 23% 33% 22% 5%	760
	11th to 20th	Night	16% 16% 34% 25% 10% 1	751
	21st to end	Night	18% 12% 30% 31% 8%	722
May	1st to 10th	Night	19% 11% 26% 29% 14% 1	570
	11th to 20th	Night	17% 6% 27% 35% 14% 1	560
	21st to end	Night	12% 4 24% 35% 24% 1	411
June	1st to 10th	Night	11% 3 26% 37% 21% 1	380
	11th to 20th	Night	9% 6% 19% 42% 22% 2	380
	21st to end	Night	7% 5% 20% 47% 20% 1	380
July	1st to 10th	Night	10% 2 17% 42% 24% 5%	394
	11th to 20th	Night	7% 1 12% 39% 37% 4	552
	21st to end	Night	9% 1 14% 45% 27% 4	624
August	1st to 10th	Night	9% 2 12% 46% 28% 3	567
	11th to 20th	Night	10% 3 12% 44% 28% 3	573
	21st to end	Night	10% 4 14% 39% 29% 4	836
September	1st to 10th	Night	15% 3 15% 33% 29% 5%	760
	11th to 20th	Night	11% 5% 17% 34% 29% 5%	760
	21st to end	Night	21% 5% 21% 31% 20% 1	760
October	1st to 10th	Night	20% 8% 19% 29% 22% 3	760
	11th to 20th	Night	15% 12% 26% 33% 13% 1	760
	21st to end	Night	17% 11% 28% 32% 10% 1	836
November	1st to 10th	Night	14% 11% 28% 35% 12% 1	755
	11th to 20th	Night	17% 16% 30% 28% 8% 1	760
	21st to end	Night	17% 17% 28% 30% 7% 1	760
December	1st to 10th	Night	20% 17% 31% 26% 6%	760
	11th to 20th	Night	18% 12% 35% 32% 3	760
	21st to end	Night	17% 16% 30% 34% 2	836

Page generated at 2024-11-01 22:47:46. Version ac07

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