Wytheville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wytheville clear sky chart from 2005-11-06 to 2026-04-02.

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% 7% 3 8% 5% 5% 5% 4 6% 8% 37%	131690
	Night	12% 7% 3 7% 5% 4 5% 4 6% 8% 40%	130160
Transparency	Day	44% 5% 12% 21% 15% 4	135335
	Night	41% 5% 12% 23% 15% 4	134584
Seeing	Day	22% 16% 24% 20% 12% 5%	17017
	Night	18% 14% 23% 27% 15% 2	27172

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% 10% 3 8% 5% 4 4 3 4 6% 41%	5258
	11th to 20th	Day	8% 8% 4 11% 6% 5% 4 3 4 5% 43%	5280
	21st to end	Day	13% 8% 4 9% 5% 4 4 3 5% 5% 42%	5780
February	1st to 10th	Day	12% 10% 4 9% 5% 5% 5% 4 5% 6% 37%	1890
	11th to 20th	Day	17% 8% 3 9% 5% 4 4 3 5% 7% 36%	1980
	21st to end	Day	16% 8% 4 8% 5% 4 4 3 5% 7% 37%	1751
March	1st to 10th	Day	16% 7% 4 8% 4 4 5% 4 5% 7% 35%	5045
	11th to 20th	Day	9% 8% 3 7% 4 4 3 3 4 7% 49%	5090
	21st to end	Day	13% 7% 2 7% 5% 5% 4 3 5% 7% 41%	5586
April	1st to 10th	Day	11% 7% 3 7% 5% 5% 4 3 5% 8% 42%	2221
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 6% 7% 43%	2393
	21st to end	Day	14% 7% 2 8% 5% 5% 5% 4 5% 7% 37%	2600
May	1st to 10th	Day	11% 7% 3 9% 6% 6% 7% 6% 8% 9% 27%	5862
	11th to 20th	Day	18% 8% 3 8% 6% 6% 5% 5% 8% 9% 25%	5861
	21st to end	Day	13% 5% 2 7% 5% 5% 6% 6% 8% 10% 32%	6433
June	1st to 10th	Day	10% 6% 2 6% 5% 6% 6% 4 8% 10% 37%	2600
	11th to 20th	Day	8% 5% 2 7% 6% 7% 7% 6% 8% 10% 34%	2600
	21st to end	Day	8% 5% 2 6% 6% 6% 6% 5% 8% 10% 37%	2600
July	1st to 10th	Day	6% 5% 2 7% 6% 6% 6% 6% 8% 10% 37%	5900
	11th to 20th	Day	7% 5% 3 8% 7% 7% 7% 6% 9% 13% 28%	5900
	21st to end	Day	10% 8% 3 11% 7% 7% 7% 6% 7% 10% 23%	6424
August	1st to 10th	Day	13% 7% 3 8% 7% 6% 7% 6% 8% 10% 25%	4234
	11th to 20th	Day	8% 6% 3 7% 5% 8% 7% 6% 9% 10% 32%	4174
	21st to end	Day	6% 4 2 6% 4 5% 5% 4 6% 11% 47%	4446
September	1st to 10th	Day	12% 6% 2 5% 5% 5% 5% 4 7% 6% 42%	2254
	11th to 20th	Day	14% 8% 3 7% 5% 5% 5% 4 6% 8% 36%	2200
	21st to end	Day	21% 7% 2 6% 5% 5% 4 3 6% 6% 34%	2200
October	1st to 10th	Day	15% 6% 2 5% 4 4 4 3 4 6% 48%	2070
	11th to 20th	Day	13% 7% 3 6% 4 3 5% 3 5% 6% 48%	2000
	21st to end	Day	14% 7% 2 6% 3 3 4 3 4 7% 47%	2200
November	1st to 10th	Day	11% 6% 2 5% 4 3 4 3 5% 7% 50%	2030
	11th to 20th	Day	10% 7% 2 5% 4 5% 4 3 6% 7% 46%	1890
	21st to end	Day	12% 8% 2 7% 5% 4 4 3 5% 7% 44%	1890
December	1st to 10th	Day	10% 8% 3 8% 5% 4 4 4 5% 6% 43%	3020
	11th to 20th	Day	15% 8% 3 8% 5% 5% 5% 4 5% 7% 34%	3463
	21st to end	Day	14% 10% 4 7% 5% 4 5% 5% 7% 8% 31%	4565
January	1st to 10th	Night	11% 10% 4 10% 5% 5% 4 4 5% 7% 36%	7635
	11th to 20th	Night	10% 7% 4 10% 6% 4 4 3 4 5% 44%	7680
	21st to end	Night	13% 9% 3 8% 4 4 4 4 5% 6% 41%	8401
February	1st to 10th	Night	12% 8% 3 8% 5% 4 4 3 6% 7% 40%	2730
	11th to 20th	Night	17% 9% 2 7% 5% 5% 5% 4 6% 6% 34%	2525
	21st to end	Night	12% 7% 3 9% 5% 5% 5% 5% 6% 6% 37%	2054
March	1st to 10th	Night	17% 9% 3 6% 5% 3 4 3 5% 5% 40%	5028
	11th to 20th	Night	10% 6% 3 6% 3 3 4 4 5% 7% 50%	5090
	21st to end	Night	12% 7% 3 7% 5% 5% 5% 4 5% 6% 41%	5588
April	1st to 10th	Night	9% 8% 3 6% 5% 5% 4 5% 6% 9% 40%	2202
	11th to 20th	Night	11% 7% 3 6% 3 3 4 4 6% 8% 45%	1972
	21st to end	Night	13% 6% 2 5% 5% 4 4 5% 6% 7% 43%	1800
May	1st to 10th	Night	13% 7% 3 8% 5% 5% 5% 4 7% 10% 34%	4033
	11th to 20th	Night	18% 7% 2 8% 5% 4 5% 4 6% 8% 31%	4032
	21st to end	Night	16% 6% 2 7% 4 5% 5% 4 6% 9% 36%	4421
June	1st to 10th	Night	8% 5% 2 5% 4 5% 6% 6% 6% 11% 41%	1800
	11th to 20th	Night	8% 5% 2 6% 5% 5% 5% 5% 7% 10% 44%	1800
	21st to end	Night	6% 5% 2 5% 5% 5% 5% 5% 7% 12% 44%	1800
July	1st to 10th	Night	6% 4 2 6% 5% 5% 6% 5% 8% 12% 40%	4058
	11th to 20th	Night	5% 6% 3 7% 6% 5% 7% 5% 9% 12% 34%	4057
	21st to end	Night	8% 8% 3 10% 7% 6% 6% 5% 8% 10% 28%	4427
August	1st to 10th	Night	13% 7% 3 7% 5% 6% 5% 5% 7% 11% 31%	2915
	11th to 20th	Night	8% 5% 2 7% 5% 6% 7% 5% 8% 9% 38%	2875
	21st to end	Night	6% 4 2 5% 4 3 4 4 5% 10% 52%	3417
September	1st to 10th	Night	11% 5% 3 6% 4 4 4 3 6% 8% 47%	2141
	11th to 20th	Night	15% 6% 2 6% 4 4 4 2 5% 7% 44%	2200
	21st to end	Night	18% 7% 3 6% 4 4 5% 3 5% 5% 40%	2200
October	1st to 10th	Night	15% 5% 2 6% 4 4 3 3 4 6% 48%	2328
	11th to 20th	Night	12% 7% 2 5% 4 3 3 3 4 6% 50%	2400
	21st to end	Night	13% 6% 2 5% 3 3 4 3 5% 7% 49%	2640
November	1st to 10th	Night	12% 7% 3 5% 4 4 4 3 4 6% 49%	2486
	11th to 20th	Night	11% 7% 2 6% 4 3 4 4 6% 7% 47%	2730
	21st to end	Night	11% 8% 3 6% 4 4 4 4 5% 6% 45%	2730
December	1st to 10th	Night	10% 6% 2 7% 4 5% 5% 4 5% 7% 44%	4380
	11th to 20th	Night	14% 10% 5% 11% 5% 5% 5% 3 5% 6% 31%	4952
	21st to end	Night	15% 8% 4 8% 5% 5% 6% 4 6% 8% 31%	6633

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	44% 3 9% 19% 23% 2	5259
	11th to 20th	Day	42% 3 4 19% 27% 6%	5280
	21st to end	Day	45% 2 7% 25% 17% 4	5780
February	1st to 10th	Day	48% 3 9% 20% 17% 2	1890
	11th to 20th	Day	51% 3 7% 21% 15% 3	1989
	21st to end	Day	48% 3 11% 16% 16% 6%	1751
March	1st to 10th	Day	47% 3 6% 19% 16% 8%	5045
	11th to 20th	Day	37% 3 7% 21% 23% 9%	5090
	21st to end	Day	44% 3 8% 25% 17% 3	5586
April	1st to 10th	Day	41% 3 11% 22% 17% 4	2221
	11th to 20th	Day	41% 3 10% 23% 17% 5%	2393
	21st to end	Day	45% 4 12% 24% 12% 2	2600
May	1st to 10th	Day	51% 5% 14% 19% 9% 1	5897
	11th to 20th	Day	54% 5% 12% 22% 7% 1	5865
	21st to end	Day	44% 6% 14% 20% 14% 3	6447
June	1st to 10th	Day	43% 7% 15% 23% 12%	2600
	11th to 20th	Day	42% 9% 16% 18% 14% 1	2600
	21st to end	Day	40% 7% 16% 22% 13% 2	2600
July	1st to 10th	Day	39% 9% 19% 21% 10% 3	5835
	11th to 20th	Day	45% 9% 23% 18% 4 1	5831
	21st to end	Day	55% 8% 14% 16% 7%	6240
August	1st to 10th	Day	51% 7% 17% 20% 5%	4221
	11th to 20th	Day	42% 8% 17% 22% 9% 2	4213
	21st to end	Day	32% 5% 18% 31% 12% 2	4446
September	1st to 10th	Day	41% 6% 11% 21% 16% 5%	2254
	11th to 20th	Day	46% 5% 7% 24% 16% 1	2200
	21st to end	Day	50% 5% 10% 19% 14% 2	2200
October	1st to 10th	Day	33% 4 7% 20% 28% 8%	3369
	11th to 20th	Day	28% 3 6% 26% 19% 18%	3240
	21st to end	Day	28% 3 7% 30% 17% 15%	3538
November	1st to 10th	Day	36% 3 9% 22% 25% 5%	2030
	11th to 20th	Day	37% 3 8% 24% 23% 5%	1890
	21st to end	Day	41% 3 9% 23% 21% 4	1890
December	1st to 10th	Day	40% 4 10% 20% 22% 3	3020
	11th to 20th	Day	49% 4 9% 17% 18% 3	3460
	21st to end	Day	49% 4 10% 22% 13% 2	4565
January	1st to 10th	Night	46% 4 11% 21% 16% 3	7636
	11th to 20th	Night	43% 3 5% 19% 24% 6%	7680
	21st to end	Night	43% 3 8% 24% 19% 3	8401
February	1st to 10th	Night	43% 4 12% 24% 16% 1	2730
	11th to 20th	Night	50% 3 9% 20% 14% 4	2526
	21st to end	Night	47% 4 10% 23% 11% 5%	2054
March	1st to 10th	Night	46% 4 6% 23% 16% 6%	5028
	11th to 20th	Night	34% 3 7% 24% 23% 10%	5090
	21st to end	Night	43% 3 10% 25% 15% 3	5588
April	1st to 10th	Night	41% 5% 13% 23% 16% 3	2202
	11th to 20th	Night	38% 4 11% 24% 19% 5%	1972
	21st to end	Night	40% 5% 15% 27% 13% 1	1800
May	1st to 10th	Night	44% 8% 17% 22% 9%	4060
	11th to 20th	Night	51% 6% 15% 23% 5%	4033
	21st to end	Night	44% 5% 17% 25% 7% 2	4429
June	1st to 10th	Night	36% 9% 19% 23% 13% 1	1800
	11th to 20th	Night	35% 7% 20% 25% 12% 1	1800
	21st to end	Night	32% 8% 18% 26% 14% 2	1800
July	1st to 10th	Night	35% 10% 19% 26% 9% 1	4015
	11th to 20th	Night	39% 11% 24% 21% 4 1	4006
	21st to end	Night	48% 9% 17% 17% 8%	4297
August	1st to 10th	Night	45% 7% 22% 19% 6%	2904
	11th to 20th	Night	38% 8% 21% 24% 9%	2902
	21st to end	Night	29% 5% 16% 37% 12% 1	3417
September	1st to 10th	Night	36% 7% 15% 22% 17% 4	2141
	11th to 20th	Night	41% 4 12% 24% 18% 1	2200
	21st to end	Night	47% 5% 9% 24% 14% 2	2200
October	1st to 10th	Night	34% 6% 7% 22% 27% 5%	3809
	11th to 20th	Night	28% 3 9% 23% 21% 17%	3899
	21st to end	Night	24% 2 8% 31% 23% 12%	4252
November	1st to 10th	Night	37% 3 9% 22% 23% 5%	2486
	11th to 20th	Night	37% 3 8% 23% 23% 6%	2730
	21st to end	Night	39% 3 8% 25% 20% 4	2730
December	1st to 10th	Night	38% 5% 9% 28% 18% 2	4380
	11th to 20th	Night	53% 4 9% 17% 14% 3	4954
	21st to end	Night	49% 3 12% 21% 13% 1	6633

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	43% 25% 23% 6% 2 1	330
	11th to 20th	Day	40% 27% 26% 6% 1	330
	21st to end	Day	36% 34% 21% 8% 2	363
February	1st to 10th	Day	34% 31% 23% 9% 3	330
	11th to 20th	Day	50% 25% 19% 5% 1	330
	21st to end	Day	40% 27% 25% 7%	294
March	1st to 10th	Day	29% 25% 25% 16% 4 1	540
	11th to 20th	Day	31% 26% 26% 12% 4 1	540
	21st to end	Day	29% 24% 26% 16% 5%	594
April	1st to 10th	Day	26% 27% 23% 15% 8%	504
	11th to 20th	Day	24% 22% 24% 18% 8% 3	492
	21st to end	Day	23% 20% 28% 17% 10% 2	500
May	1st to 10th	Day	21% 21% 32% 15% 7% 4	503
	11th to 20th	Day	21% 14% 30% 19% 11% 5%	527
	21st to end	Day	20% 12% 24% 21% 14% 9%	573
June	1st to 10th	Day	12% 9% 31% 25% 16% 7%	530
	11th to 20th	Day	8% 9% 26% 29% 18% 9%	530
	21st to end	Day	10% 12% 27% 26% 17% 9%	530
July	1st to 10th	Day	8% 6% 22% 29% 22% 12%	525
	11th to 20th	Day	5% 5% 20% 36% 24% 10%	524
	21st to end	Day	8% 7% 22% 28% 24% 11%	576
August	1st to 10th	Day	18% 7% 21% 23% 20% 11%	526
	11th to 20th	Day	10% 4 22% 27% 23% 13%	519
	21st to end	Day	10% 5% 19% 27% 21% 17%	583
September	1st to 10th	Day	11% 6% 20% 28% 24% 12%	530
	11th to 20th	Day	14% 6% 18% 26% 24% 12%	530
	21st to end	Day	25% 12% 19% 24% 15% 4	530
October	1st to 10th	Day	18% 9% 22% 24% 21% 6%	530
	11th to 20th	Day	18% 18% 21% 26% 14% 3	530
	21st to end	Day	23% 16% 25% 22% 11% 3	583
November	1st to 10th	Day	17% 17% 29% 24% 10% 2	508
	11th to 20th	Day	26% 19% 31% 18% 4 1	330
	21st to end	Day	27% 24% 28% 16% 4 1	330
December	1st to 10th	Day	32% 28% 29% 9% 2	330
	11th to 20th	Day	32% 22% 29% 12% 5% 1	330
	21st to end	Day	30% 25% 28% 11% 5% 1	363
January	1st to 10th	Night	26% 28% 27% 17% 3	840
	11th to 20th	Night	27% 24% 28% 20% 1	840
	21st to end	Night	24% 28% 30% 17% 1	924
February	1st to 10th	Night	25% 20% 31% 22% 2	840
	11th to 20th	Night	32% 27% 26% 14% 1	823
	21st to end	Night	23% 28% 32% 15% 2	692
March	1st to 10th	Night	21% 22% 31% 22% 3	840
	11th to 20th	Night	25% 21% 29% 20% 5%	840
	21st to end	Night	20% 20% 32% 22% 6%	924
April	1st to 10th	Night	20% 23% 26% 25% 6%	805
	11th to 20th	Night	17% 20% 26% 27% 9% 1	788
	21st to end	Night	16% 15% 25% 35% 9%	600
May	1st to 10th	Night	14% 14% 29% 29% 14% 1	600
	11th to 20th	Night	17% 9% 21% 32% 19% 1	591
	21st to end	Night	16% 5% 18% 30% 28% 4	650
June	1st to 10th	Night	10% 3 21% 40% 24% 3	600
	11th to 20th	Night	8% 3 18% 35% 33% 3	600
	21st to end	Night	6% 4 16% 37% 32% 4	600
July	1st to 10th	Night	7% 2 13% 34% 39% 5%	585
	11th to 20th	Night	5% 3 9% 34% 44% 5%	582
	21st to end	Night	7% 4 11% 36% 36% 6%	657
August	1st to 10th	Night	11% 4 12% 32% 37% 4	597
	11th to 20th	Night	13% 2 11% 34% 34% 6%	594
	21st to end	Night	11% 2 11% 32% 37% 7%	776
September	1st to 10th	Night	11% 4 12% 33% 35% 5%	800
	11th to 20th	Night	17% 4 13% 30% 31% 5%	800
	21st to end	Night	22% 5% 17% 32% 23% 1	800
October	1st to 10th	Night	17% 9% 17% 27% 26% 4	800
	11th to 20th	Night	16% 13% 24% 31% 15% 2	800
	21st to end	Night	18% 15% 21% 32% 11% 2	880
November	1st to 10th	Night	17% 14% 24% 30% 14% 2	820
	11th to 20th	Night	22% 15% 25% 30% 8% 1	840
	21st to end	Night	20% 18% 28% 25% 9%	840
December	1st to 10th	Night	24% 21% 30% 21% 4	840
	11th to 20th	Night	21% 21% 29% 25% 4	840
	21st to end	Night	26% 20% 26% 24% 4	924

Page generated at 2026-03-30 02:18:41. Version ac07

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