Asheville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Asheville clear sky chart from 2005-11-06 to 2026-09-14.

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	9% 7% 3 8% 5% 5% 6% 5% 7% 8% 38%	148725
	Night	10% 7% 3 7% 5% 5% 5% 4 6% 8% 40%	142351
Transparency	Day	39% 10% 13% 19% 15% 5%	152436
	Night	37% 10% 14% 20% 15% 5%	146712
Seeing	Day	18% 15% 24% 22% 14% 7%	17530
	Night	16% 13% 22% 28% 18% 3	27535

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	11% 6% 2 7% 3 4 4 3 5% 8% 48%	5258
	11th to 20th	Day	7% 4 2 5% 4 4 4 3 5% 6% 57%	5280
	21st to end	Day	10% 9% 5% 8% 4 4 5% 4 4 6% 41%	5780
February	1st to 10th	Day	11% 8% 2 6% 6% 5% 4 4 6% 7% 42%	1979
	11th to 20th	Day	12% 10% 3 7% 5% 5% 4 4 5% 6% 38%	2048
	21st to end	Day	11% 8% 3 8% 5% 5% 6% 4 5% 6% 40%	1730
March	1st to 10th	Day	14% 8% 3 8% 5% 4 5% 4 5% 6% 39%	4942
	11th to 20th	Day	9% 8% 3 6% 4 3 3 3 5% 6% 50%	5090
	21st to end	Day	13% 7% 3 6% 4 3 4 3 5% 6% 44%	5586
April	1st to 10th	Day	10% 6% 2 6% 4 5% 5% 4 7% 8% 43%	2310
	11th to 20th	Day	11% 7% 2 6% 4 4 4 4 5% 8% 44%	2517
	21st to end	Day	11% 6% 2 6% 4 5% 5% 5% 5% 7% 45%	2730
May	1st to 10th	Day	9% 8% 3 9% 6% 6% 6% 4 7% 8% 35%	7616
	11th to 20th	Day	12% 7% 3 8% 5% 6% 6% 5% 7% 8% 35%	7626
	21st to end	Day	10% 8% 3 10% 7% 6% 6% 5% 7% 9% 29%	8391
June	1st to 10th	Day	9% 6% 2 8% 6% 7% 7% 5% 8% 10% 32%	2730
	11th to 20th	Day	6% 5% 3 7% 6% 7% 6% 6% 9% 10% 35%	2730
	21st to end	Day	7% 6% 2 7% 7% 6% 7% 7% 8% 10% 34%	2730
July	1st to 10th	Day	4 5% 2 8% 7% 7% 8% 6% 9% 11% 33%	7680
	11th to 20th	Day	7% 6% 3 10% 8% 7% 8% 6% 8% 10% 26%	7680
	21st to end	Day	9% 7% 4 11% 8% 7% 8% 5% 8% 10% 24%	8340
August	1st to 10th	Day	10% 8% 3 10% 8% 8% 8% 6% 9% 11% 19%	6014
	11th to 20th	Day	5% 4 2 6% 5% 7% 6% 5% 9% 13% 37%	5951
	21st to end	Day	5% 4 2 6% 5% 5% 6% 5% 7% 9% 46%	6092
September	1st to 10th	Day	9% 7% 3 7% 6% 6% 5% 5% 8% 7% 38%	2310
	11th to 20th	Day	14% 6% 3 8% 6% 6% 5% 5% 7% 8% 32%	2233
	21st to end	Day	12% 7% 3 7% 5% 5% 6% 5% 6% 6% 37%	2200
October	1st to 10th	Day	11% 6% 2 7% 4 4 4 4 6% 5% 48%	2165
	11th to 20th	Day	8% 5% 3 6% 4 3 5% 3 5% 6% 54%	2000
	21st to end	Day	11% 7% 2 6% 4 3 3 3 4 6% 53%	2200
November	1st to 10th	Day	8% 7% 2 6% 4 4 4 3 3 6% 55%	1959
	11th to 20th	Day	9% 6% 2 5% 5% 3 4 3 5% 7% 50%	1890
	21st to end	Day	11% 7% 3 6% 3 3 4 3 6% 7% 47%	1890
December	1st to 10th	Day	9% 6% 2 7% 4 5% 5% 4 5% 7% 47%	3020
	11th to 20th	Day	11% 6% 3 7% 5% 5% 5% 4 6% 9% 39%	3463
	21st to end	Day	14% 6% 2 6% 5% 5% 5% 4 4 8% 39%	4565
January	1st to 10th	Night	12% 7% 2 9% 5% 4 5% 4 5% 7% 42%	7635
	11th to 20th	Night	8% 6% 2 6% 4 5% 5% 3 5% 6% 50%	7680
	21st to end	Night	10% 9% 4 8% 5% 4 4 3 5% 6% 43%	8401
February	1st to 10th	Night	10% 8% 2 6% 4 5% 5% 4 6% 7% 41%	2635
	11th to 20th	Night	14% 9% 3 7% 4 5% 4 3 5% 7% 38%	2458
	21st to end	Night	12% 7% 3 9% 5% 6% 5% 5% 5% 6% 37%	2076
March	1st to 10th	Night	15% 10% 4 8% 5% 4 4 4 6% 6% 35%	5129
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 6% 8% 49%	5090
	21st to end	Night	13% 8% 2 5% 5% 4 4 3 5% 7% 43%	5588
April	1st to 10th	Night	10% 7% 3 6% 5% 4 4 5% 6% 8% 45%	2310
	11th to 20th	Night	8% 7% 3 6% 4 4 4 4 6% 8% 47%	2069
	21st to end	Night	9% 6% 2 7% 5% 4 4 3 5% 8% 47%	1890
May	1st to 10th	Night	10% 8% 3 8% 4 4 5% 5% 8% 11% 35%	5237
	11th to 20th	Night	12% 8% 4 9% 5% 5% 5% 4 6% 8% 35%	5234
	21st to end	Night	13% 9% 4 9% 6% 6% 5% 5% 7% 9% 28%	5761
June	1st to 10th	Night	6% 7% 3 7% 5% 6% 7% 5% 8% 12% 34%	1890
	11th to 20th	Night	6% 6% 2 5% 5% 5% 4 6% 9% 12% 40%	1890
	21st to end	Night	5% 6% 2 5% 6% 5% 6% 5% 8% 11% 42%	1890
July	1st to 10th	Night	4 5% 3 8% 7% 6% 8% 5% 8% 12% 33%	5278
	11th to 20th	Night	6% 6% 3 9% 7% 7% 7% 6% 9% 11% 29%	5277
	21st to end	Night	9% 8% 4 11% 7% 7% 7% 5% 7% 10% 26%	5736
August	1st to 10th	Night	8% 8% 3 11% 8% 7% 8% 6% 8% 9% 24%	4135
	11th to 20th	Night	5% 5% 2 7% 5% 6% 7% 5% 8% 12% 37%	4095
	21st to end	Night	6% 6% 3 6% 4 5% 7% 5% 7% 9% 42%	4967
September	1st to 10th	Night	9% 5% 2 7% 6% 6% 5% 5% 6% 8% 41%	2310
	11th to 20th	Night	12% 7% 3 10% 5% 6% 5% 4 6% 7% 35%	2234
	21st to end	Night	10% 6% 3 8% 4 5% 5% 4 5% 6% 44%	2200
October	1st to 10th	Night	12% 6% 2 7% 4 4 4 3 5% 6% 47%	2235
	11th to 20th	Night	9% 6% 2 6% 4 5% 4 4 6% 6% 49%	2400
	21st to end	Night	10% 7% 2 5% 3 3 4 3 5% 5% 53%	2640
November	1st to 10th	Night	10% 6% 3 6% 3 4 4 4 5% 6% 49%	2556
	11th to 20th	Night	10% 6% 2 6% 5% 4 4 3 5% 7% 49%	2730
	21st to end	Night	10% 6% 3 6% 4 5% 4 4 6% 7% 45%	2730
December	1st to 10th	Night	10% 5% 3 6% 4 4 5% 4 6% 7% 46%	4380
	11th to 20th	Night	13% 9% 4 10% 5% 5% 5% 4 5% 7% 35%	4952
	21st to end	Night	14% 8% 3 7% 4 4 5% 4 6% 7% 39%	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	33% 4 11% 25% 24% 3	5259
	11th to 20th	Day	25% 5% 7% 14% 35% 14%	5280
	21st to end	Day	39% 7% 8% 19% 18% 9%	5780
February	1st to 10th	Day	40% 6% 11% 22% 18% 4	1979
	11th to 20th	Day	43% 6% 10% 18% 17% 4	2058
	21st to end	Day	43% 7% 10% 15% 19% 6%	1730
March	1st to 10th	Day	41% 7% 8% 14% 20% 10%	4942
	11th to 20th	Day	33% 6% 7% 15% 22% 18%	5090
	21st to end	Day	38% 7% 10% 25% 15% 4	5586
April	1st to 10th	Day	34% 9% 14% 22% 17% 4	2310
	11th to 20th	Day	36% 7% 10% 20% 21% 6%	2517
	21st to end	Day	36% 9% 13% 26% 14% 2	2730
May	1st to 10th	Day	43% 9% 14% 21% 12% 1	7651
	11th to 20th	Day	42% 11% 15% 19% 11% 1	7630
	21st to end	Day	47% 11% 13% 15% 11% 2	8405
June	1st to 10th	Day	42% 14% 18% 17% 8% 1	2730
	11th to 20th	Day	39% 13% 19% 18% 10% 1	2730
	21st to end	Day	41% 13% 17% 16% 11% 2	2730
July	1st to 10th	Day	38% 15% 20% 20% 7%	7615
	11th to 20th	Day	47% 16% 20% 14% 3	7611
	21st to end	Day	51% 13% 16% 12% 7% 1	8156
August	1st to 10th	Day	52% 17% 17% 13% 2	6001
	11th to 20th	Day	31% 13% 28% 18% 7% 2	5990
	21st to end	Day	30% 11% 15% 31% 12% 1	6092
September	1st to 10th	Day	40% 10% 14% 18% 15% 3	2310
	11th to 20th	Day	45% 11% 12% 17% 13% 2	2233
	21st to end	Day	43% 10% 13% 16% 13% 4	2200
October	1st to 10th	Day	27% 6% 9% 19% 27% 11%	3529
	11th to 20th	Day	21% 4 7% 22% 24% 22%	3240
	21st to end	Day	27% 4 8% 24% 23% 14%	3538
November	1st to 10th	Day	31% 5% 9% 20% 27% 8%	1959
	11th to 20th	Day	31% 6% 8% 23% 25% 7%	1890
	21st to end	Day	34% 6% 9% 24% 22% 5%	1890
December	1st to 10th	Day	34% 7% 7% 19% 27% 6%	3020
	11th to 20th	Day	37% 7% 12% 20% 19% 5%	3460
	21st to end	Day	38% 7% 13% 25% 14% 3	4565
January	1st to 10th	Night	34% 6% 13% 27% 17% 3	7636
	11th to 20th	Night	27% 6% 8% 20% 31% 9%	7680
	21st to end	Night	39% 5% 9% 19% 20% 8%	8401
February	1st to 10th	Night	38% 7% 13% 21% 18% 4	2635
	11th to 20th	Night	43% 6% 11% 19% 16% 5%	2459
	21st to end	Night	43% 8% 11% 17% 16% 5%	2076
March	1st to 10th	Night	40% 11% 9% 13% 20% 6%	5129
	11th to 20th	Night	28% 8% 8% 20% 23% 14%	5090
	21st to end	Night	40% 8% 11% 25% 12% 5%	5588
April	1st to 10th	Night	33% 8% 16% 21% 18% 3	2310
	11th to 20th	Night	33% 7% 12% 24% 20% 4	2069
	21st to end	Night	33% 9% 15% 25% 15% 2	1890
May	1st to 10th	Night	39% 11% 15% 25% 8% 1	5264
	11th to 20th	Night	42% 10% 16% 22% 8%	5235
	21st to end	Night	46% 12% 16% 17% 8% 1	5771
June	1st to 10th	Night	37% 16% 20% 18% 8% 1	1890
	11th to 20th	Night	33% 14% 24% 22% 8% 1	1890
	21st to end	Night	32% 15% 20% 20% 12% 2	1890
July	1st to 10th	Night	36% 18% 23% 19% 5%	5235
	11th to 20th	Night	41% 21% 23% 13% 2 1	5226
	21st to end	Night	48% 14% 19% 12% 6% 2	5606
August	1st to 10th	Night	47% 20% 19% 11% 3	4124
	11th to 20th	Night	32% 16% 27% 19% 6%	4122
	21st to end	Night	32% 13% 18% 29% 7% 1	4967
September	1st to 10th	Night	38% 13% 14% 20% 13% 2	2310
	11th to 20th	Night	45% 11% 13% 15% 14% 1	2234
	21st to end	Night	39% 8% 14% 20% 16% 3	2200
October	1st to 10th	Night	30% 7% 12% 17% 25% 10%	3651
	11th to 20th	Night	22% 7% 7% 20% 24% 20%	3899
	21st to end	Night	29% 5% 8% 23% 23% 13%	4252
November	1st to 10th	Night	33% 9% 9% 20% 21% 8%	2556
	11th to 20th	Night	33% 5% 10% 21% 24% 8%	2730
	21st to end	Night	35% 7% 8% 23% 21% 6%	2730
December	1st to 10th	Night	34% 6% 10% 22% 24% 4	4380
	11th to 20th	Night	41% 9% 11% 18% 17% 4	4954
	21st to end	Night	40% 7% 15% 20% 17% 2	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	34% 26% 31% 7% 2	330
	11th to 20th	Day	38% 21% 25% 14% 2	330
	21st to end	Day	28% 35% 26% 10% 2	363
February	1st to 10th	Day	26% 29% 31% 13% 1	330
	11th to 20th	Day	40% 31% 23% 6% 1	330
	21st to end	Day	35% 33% 23% 8% 1	273
March	1st to 10th	Day	26% 22% 29% 16% 6%	485
	11th to 20th	Day	29% 24% 29% 15% 4 1	540
	21st to end	Day	25% 24% 29% 16% 4	594
April	1st to 10th	Day	23% 24% 26% 18% 8% 1	540
	11th to 20th	Day	18% 22% 27% 20% 10% 2	532
	21st to end	Day	19% 17% 28% 20% 11% 4	540
May	1st to 10th	Day	17% 22% 27% 20% 9% 5%	543
	11th to 20th	Day	17% 14% 23% 26% 13% 7%	567
	21st to end	Day	15% 12% 24% 23% 16% 10%	617
June	1st to 10th	Day	12% 6% 29% 26% 16% 10%	570
	11th to 20th	Day	8% 9% 24% 25% 22% 12%	570
	21st to end	Day	9% 7% 27% 27% 18% 12%	570
July	1st to 10th	Day	8% 5% 15% 27% 29% 16%	565
	11th to 20th	Day	7% 5% 13% 28% 27% 19%	564
	21st to end	Day	9% 4 15% 28% 29% 15%	620
August	1st to 10th	Day	18% 6% 17% 24% 20% 15%	566
	11th to 20th	Day	8% 4 19% 31% 23% 15%	559
	21st to end	Day	10% 4 17% 27% 28% 14%	627
September	1st to 10th	Day	8% 4 17% 31% 26% 14%	570
	11th to 20th	Day	14% 6% 19% 24% 26% 10%	542
	21st to end	Day	15% 10% 19% 31% 21% 5%	530
October	1st to 10th	Day	16% 10% 19% 30% 18% 6%	530
	11th to 20th	Day	13% 17% 24% 28% 14% 4	530
	21st to end	Day	20% 15% 24% 26% 12% 3	583
November	1st to 10th	Day	18% 16% 31% 24% 9% 2	437
	11th to 20th	Day	22% 24% 33% 17% 5%	330
	21st to end	Day	23% 24% 31% 16% 6% 1	330
December	1st to 10th	Day	26% 30% 29% 13% 1	330
	11th to 20th	Day	25% 20% 32% 17% 5% 1	330
	21st to end	Day	25% 25% 34% 11% 4 1	363
January	1st to 10th	Night	26% 21% 26% 22% 5%	840
	11th to 20th	Night	22% 22% 30% 22% 4	840
	21st to end	Night	21% 21% 34% 22% 3	924
February	1st to 10th	Night	19% 18% 32% 27% 4	840
	11th to 20th	Night	26% 26% 29% 18% 1	823
	21st to end	Night	23% 25% 30% 20% 2	692
March	1st to 10th	Night	19% 21% 30% 27% 4	840
	11th to 20th	Night	22% 18% 32% 22% 7% 1	840
	21st to end	Night	20% 18% 33% 22% 7%	924
April	1st to 10th	Night	18% 21% 27% 26% 8%	840
	11th to 20th	Night	17% 17% 27% 27% 11% 1	725
	21st to end	Night	13% 13% 23% 35% 16% 1	630
May	1st to 10th	Night	13% 11% 26% 33% 16% 1	630
	11th to 20th	Night	14% 10% 20% 33% 21% 2	621
	21st to end	Night	13% 7% 15% 29% 30% 6%	683
June	1st to 10th	Night	8% 5% 16% 38% 28% 6%	630
	11th to 20th	Night	7% 3 17% 30% 34% 9%	630
	21st to end	Night	6% 3 12% 36% 38% 6%	630
July	1st to 10th	Night	9% 3 8% 25% 48% 7%	615
	11th to 20th	Night	8% 4 7% 24% 46% 12%	612
	21st to end	Night	8% 3 7% 29% 42% 11%	690
August	1st to 10th	Night	11% 3 11% 26% 41% 9%	627
	11th to 20th	Night	12% 3 11% 27% 38% 9%	624
	21st to end	Night	9% 2 10% 30% 41% 8%	748
September	1st to 10th	Night	9% 3 14% 29% 38% 6%	840
	11th to 20th	Night	14% 6% 15% 27% 33% 6%	813
	21st to end	Night	16% 7% 16% 31% 27% 3	800
October	1st to 10th	Night	15% 9% 18% 27% 25% 6%	800
	11th to 20th	Night	15% 11% 25% 30% 18% 2	800
	21st to end	Night	16% 14% 19% 35% 14% 2	880
November	1st to 10th	Night	16% 10% 23% 33% 15% 3	820
	11th to 20th	Night	18% 14% 24% 33% 10% 1	840
	21st to end	Night	20% 16% 23% 29% 12% 1	840
December	1st to 10th	Night	22% 19% 26% 28% 5%	840
	11th to 20th	Night	19% 15% 29% 30% 7% 1	840
	21st to end	Night	23% 17% 27% 28% 5%	924

Page generated at 2026-09-11 04:11:51. Version ac07

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