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 2024-03-01.

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	11% 6% 3 6% 6% 4 6% 6% 6% 8% 38%	78856
	Night	11% 7% 3 6% 6% 4 5% 5% 6% 8% 40%	80564
Transparency	Day	40% 10% 13% 18% 15% 4	78579
	Night	38% 9% 14% 19% 16% 4	80360
Seeing	Day	18% 15% 24% 22% 15% 7%	14059
	Night	16% 13% 22% 28% 19% 3	24235

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 5% 4 3 4 5% 6% 9% 44%	2836
	11th to 20th	Day	11% 5% 3 5% 4 4 5% 5% 7% 6% 44%	2840
	21st to end	Day	15% 10% 5% 8% 5% 2 3 4 4 6% 38%	3124
February	1st to 10th	Day	12% 8% 2 5% 6% 4 4 5% 5% 7% 41%	1790
	11th to 20th	Day	12% 10% 4 6% 6% 4 4 4 5% 7% 39%	1848
	21st to end	Day	12% 8% 4 6% 6% 3 5% 6% 5% 6% 40%	1570
March	1st to 10th	Day	12% 6% 3 5% 5% 3 4 5% 6% 8% 45%	1932
	11th to 20th	Day	15% 8% 4 7% 6% 3 5% 5% 6% 6% 35%	1980
	21st to end	Day	14% 8% 4 6% 6% 3 5% 5% 6% 7% 36%	2178
April	1st to 10th	Day	9% 5% 2 5% 5% 4 6% 5% 6% 9% 43%	1980
	11th to 20th	Day	13% 7% 3 5% 5% 3 4 5% 5% 9% 42%	2153
	21st to end	Day	11% 6% 2 6% 5% 4 5% 6% 5% 7% 44%	2340
May	1st to 10th	Day	9% 6% 4 7% 6% 4 5% 5% 5% 8% 39%	2340
	11th to 20th	Day	12% 6% 3 6% 7% 4 7% 7% 7% 7% 34%	2301
	21st to end	Day	10% 6% 3 6% 6% 5% 6% 7% 7% 10% 34%	2531
June	1st to 10th	Day	10% 6% 3 6% 7% 5% 7% 7% 7% 10% 31%	2340
	11th to 20th	Day	7% 5% 3 7% 7% 5% 7% 7% 9% 9% 35%	2340
	21st to end	Day	7% 6% 3 6% 7% 5% 8% 8% 7% 9% 33%	2340
July	1st to 10th	Day	8% 7% 4 8% 9% 5% 8% 8% 8% 10% 26%	2340
	11th to 20th	Day	10% 6% 3 8% 7% 5% 9% 8% 8% 9% 26%	2340
	21st to end	Day	8% 5% 3 7% 9% 5% 8% 8% 8% 10% 28%	2547
August	1st to 10th	Day	10% 7% 3 8% 8% 5% 7% 7% 9% 11% 24%	2327
	11th to 20th	Day	11% 7% 4 7% 8% 6% 7% 7% 7% 10% 26%	2303
	21st to end	Day	10% 6% 3 7% 7% 5% 7% 8% 7% 9% 31%	2391
September	1st to 10th	Day	10% 6% 3 7% 7% 4 6% 6% 7% 7% 36%	1980
	11th to 20th	Day	14% 6% 3 6% 7% 4 6% 6% 7% 8% 33%	1980
	21st to end	Day	11% 6% 4 6% 6% 4 6% 7% 6% 6% 39%	1980
October	1st to 10th	Day	12% 6% 3 6% 5% 3 4 4 5% 5% 48%	1949
	11th to 20th	Day	9% 5% 3 5% 5% 2 4 5% 4 6% 52%	1800
	21st to end	Day	11% 6% 2 5% 4 2 3 4 4 5% 53%	1980
November	1st to 10th	Day	8% 6% 2 5% 4 2 4 3 3 5% 56%	1769
	11th to 20th	Day	9% 5% 3 5% 5% 2 4 4 5% 7% 50%	1710
	21st to end	Day	12% 6% 4 5% 4 2 4 4 5% 7% 47%	1710
December	1st to 10th	Day	14% 8% 3 7% 5% 4 7% 5% 6% 6% 36%	1710
	11th to 20th	Day	11% 6% 2 5% 6% 3 5% 5% 6% 8% 42%	2153
	21st to end	Day	15% 6% 3 5% 7% 4 7% 6% 4 7% 37%	3124
January	1st to 10th	Night	13% 7% 3 7% 6% 4 6% 6% 6% 8% 35%	4109
	11th to 20th	Night	11% 8% 3 7% 6% 4 4 4 5% 7% 42%	4120
	21st to end	Night	15% 11% 4 7% 5% 3 4 4 5% 5% 36%	4532
February	1st to 10th	Night	10% 8% 3 6% 5% 3 6% 5% 6% 7% 42%	2385
	11th to 20th	Night	14% 8% 3 6% 5% 4 4 5% 5% 7% 38%	2218
	21st to end	Night	13% 7% 4 7% 6% 4 6% 6% 5% 7% 36%	1884
March	1st to 10th	Night	11% 6% 3 6% 6% 3 5% 5% 6% 6% 43%	2033
	11th to 20th	Night	12% 8% 3 8% 6% 4 5% 5% 6% 8% 36%	1980
	21st to end	Night	12% 7% 3 6% 6% 4 5% 4 6% 8% 39%	2178
April	1st to 10th	Night	10% 6% 3 4 6% 3 4 5% 5% 8% 46%	1980
	11th to 20th	Night	9% 7% 3 6% 4 3 4 4 6% 8% 46%	1771
	21st to end	Night	10% 5% 3 6% 6% 3 4 4 4 8% 48%	1620
May	1st to 10th	Night	9% 6% 3 6% 5% 4 5% 5% 7% 8% 42%	1620
	11th to 20th	Night	11% 6% 3 6% 6% 4 6% 6% 7% 8% 37%	1592
	21st to end	Night	9% 5% 3 7% 6% 3 5% 5% 7% 12% 38%	1744
June	1st to 10th	Night	7% 6% 3 6% 6% 3 7% 7% 8% 13% 35%	1620
	11th to 20th	Night	6% 6% 3 4 5% 3 5% 6% 9% 11% 42%	1620
	21st to end	Night	6% 5% 2 4 6% 4 6% 6% 8% 11% 42%	1620
July	1st to 10th	Night	7% 7% 3 7% 7% 5% 7% 6% 7% 11% 35%	1620
	11th to 20th	Night	8% 5% 3 6% 6% 4 7% 7% 9% 12% 34%	1620
	21st to end	Night	5% 4 4 7% 8% 5% 8% 7% 8% 11% 34%	1771
August	1st to 10th	Night	8% 4 2 6% 7% 4 6% 7% 8% 10% 36%	1611
	11th to 20th	Night	9% 6% 3 6% 8% 4 6% 6% 8% 10% 34%	1598
	21st to end	Night	8% 7% 3 6% 5% 5% 8% 7% 7% 9% 35%	1941
September	1st to 10th	Night	9% 5% 3 6% 7% 4 5% 6% 6% 8% 40%	1980
	11th to 20th	Night	13% 6% 3 8% 6% 4 5% 4 5% 7% 37%	1980
	21st to end	Night	9% 6% 3 6% 5% 4 5% 5% 6% 6% 46%	1980
October	1st to 10th	Night	13% 6% 2 5% 5% 3 4 4 4 5% 48%	2011
	11th to 20th	Night	10% 6% 2 5% 5% 3 4 5% 6% 6% 47%	2160
	21st to end	Night	10% 6% 2 5% 3 2 4 4 6% 5% 53%	2376
November	1st to 10th	Night	10% 5% 3 5% 4 3 4 5% 5% 6% 50%	2306
	11th to 20th	Night	11% 5% 3 5% 5% 3 4 4 5% 7% 49%	2470
	21st to end	Night	11% 6% 3 5% 5% 3 5% 5% 6% 7% 45%	2470
December	1st to 10th	Night	14% 7% 4 7% 6% 3 5% 6% 6% 7% 35%	2470
	11th to 20th	Night	13% 9% 3 7% 5% 3 4 5% 5% 7% 40%	3042
	21st to end	Night	14% 9% 3 6% 6% 4 5% 6% 6% 7% 33%	4532

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	31% 5% 11% 24% 23% 5%	2837
	11th to 20th	Day	34% 8% 11% 16% 25% 7%	2840
	21st to end	Day	42% 6% 9% 19% 20% 4	3124
February	1st to 10th	Day	41% 6% 11% 20% 18% 4	1790
	11th to 20th	Day	43% 6% 10% 18% 17% 5%	1858
	21st to end	Day	43% 7% 11% 15% 18% 6%	1570
March	1st to 10th	Day	35% 7% 10% 21% 20% 7%	1932
	11th to 20th	Day	46% 8% 11% 15% 15% 5%	1980
	21st to end	Day	44% 9% 13% 19% 13% 2	2178
April	1st to 10th	Day	34% 9% 13% 22% 18% 4	1980
	11th to 20th	Day	39% 7% 10% 18% 21% 6%	2153
	21st to end	Day	36% 9% 13% 24% 15% 2	2340
May	1st to 10th	Day	40% 10% 14% 20% 14% 2	2340
	11th to 20th	Day	46% 14% 13% 16% 10% 1	2305
	21st to end	Day	41% 13% 15% 21% 9%	2531
June	1st to 10th	Day	44% 15% 18% 16% 7% 1	2340
	11th to 20th	Day	41% 14% 18% 16% 10% 2	2340
	21st to end	Day	43% 13% 16% 16% 11% 2	2340
July	1st to 10th	Day	48% 14% 17% 12% 8% 1	2275
	11th to 20th	Day	48% 15% 17% 10% 8% 1	2271
	21st to end	Day	45% 16% 18% 13% 6% 1	2405
August	1st to 10th	Day	50% 16% 16% 14% 4	2314
	11th to 20th	Day	49% 15% 16% 14% 6% 1	2303
	21st to end	Day	45% 14% 16% 16% 6% 3	2391
September	1st to 10th	Day	44% 11% 14% 16% 13% 3	1980
	11th to 20th	Day	46% 11% 11% 16% 14% 2	1980
	21st to end	Day	42% 9% 12% 17% 15% 5%	1980
October	1st to 10th	Day	35% 7% 14% 16% 23% 5%	1949
	11th to 20th	Day	31% 7% 11% 23% 20% 9%	1800
	21st to end	Day	32% 5% 9% 23% 23% 9%	1980
November	1st to 10th	Day	30% 5% 8% 20% 27% 9%	1769
	11th to 20th	Day	32% 6% 8% 22% 25% 7%	1710
	21st to end	Day	34% 6% 9% 23% 23% 5%	1710
December	1st to 10th	Day	46% 7% 9% 19% 14% 5%	1710
	11th to 20th	Day	34% 6% 11% 21% 22% 6%	2150
	21st to end	Day	39% 8% 10% 24% 17% 2	3124
January	1st to 10th	Night	34% 8% 13% 23% 18% 5%	4109
	11th to 20th	Night	33% 8% 12% 17% 24% 7%	4120
	21st to end	Night	45% 7% 8% 16% 20% 4	4532
February	1st to 10th	Night	38% 6% 14% 20% 18% 4	2385
	11th to 20th	Night	42% 6% 11% 19% 16% 5%	2219
	21st to end	Night	43% 8% 11% 17% 16% 5%	1884
March	1st to 10th	Night	39% 7% 11% 16% 20% 7%	2033
	11th to 20th	Night	43% 9% 13% 19% 14% 3	1980
	21st to end	Night	43% 8% 13% 22% 13% 2	2178
April	1st to 10th	Night	34% 7% 15% 22% 19% 3	1980
	11th to 20th	Night	34% 7% 12% 22% 20% 5%	1771
	21st to end	Night	33% 9% 15% 25% 16% 2	1620
May	1st to 10th	Night	36% 11% 17% 24% 11% 1	1620
	11th to 20th	Night	42% 13% 15% 20% 10% 1	1593
	21st to end	Night	37% 12% 19% 23% 8% 1	1745
June	1st to 10th	Night	37% 16% 21% 19% 7% 1	1620
	11th to 20th	Night	32% 13% 25% 20% 8% 1	1620
	21st to end	Night	33% 15% 19% 19% 11% 2	1620
July	1st to 10th	Night	42% 15% 19% 15% 9% 1	1575
	11th to 20th	Night	38% 18% 22% 13% 7% 2	1566
	21st to end	Night	37% 18% 21% 18% 6% 1	1672
August	1st to 10th	Night	37% 20% 21% 15% 6%	1600
	11th to 20th	Night	41% 16% 17% 14% 10% 1	1598
	21st to end	Night	41% 15% 18% 19% 6% 1	1941
September	1st to 10th	Night	39% 13% 14% 19% 11% 3	1980
	11th to 20th	Night	45% 10% 13% 16% 15% 1	1980
	21st to end	Night	37% 8% 12% 22% 17% 3	1980
October	1st to 10th	Night	37% 7% 12% 18% 22% 3	2011
	11th to 20th	Night	34% 9% 11% 22% 18% 6%	2160
	21st to end	Night	30% 6% 9% 22% 25% 8%	2376
November	1st to 10th	Night	33% 8% 8% 20% 22% 8%	2306
	11th to 20th	Night	34% 5% 9% 19% 24% 9%	2470
	21st to end	Night	35% 7% 8% 23% 21% 6%	2470
December	1st to 10th	Night	44% 8% 13% 17% 14% 4	2470
	11th to 20th	Night	36% 8% 12% 17% 23% 4	3044
	21st to end	Night	42% 7% 12% 20% 15% 2	4532

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	30% 27% 33% 8% 1	270
	11th to 20th	Day	36% 22% 26% 14% 3	270
	21st to end	Day	26% 34% 28% 10% 2	297
February	1st to 10th	Day	28% 28% 30% 13% 1	270
	11th to 20th	Day	38% 31% 25% 6% 1	270
	21st to end	Day	37% 33% 22% 7% 1	225
March	1st to 10th	Day	23% 25% 31% 16% 5%	372
	11th to 20th	Day	28% 24% 27% 16% 5% 1	420
	21st to end	Day	26% 24% 28% 17% 5%	462
April	1st to 10th	Day	23% 22% 25% 20% 9% 1	420
	11th to 20th	Day	18% 21% 26% 22% 10% 3	412
	21st to end	Day	19% 17% 27% 20% 12% 4	420
May	1st to 10th	Day	16% 22% 26% 21% 10% 6%	423
	11th to 20th	Day	16% 12% 23% 27% 14% 9%	447
	21st to end	Day	13% 9% 22% 25% 18% 13%	485
June	1st to 10th	Day	13% 5% 26% 27% 17% 12%	450
	11th to 20th	Day	9% 7% 23% 24% 24% 13%	450
	21st to end	Day	10% 7% 28% 25% 18% 12%	450
July	1st to 10th	Day	9% 4 15% 28% 29% 15%	445
	11th to 20th	Day	7% 4 14% 28% 26% 20%	444
	21st to end	Day	8% 2 13% 27% 33% 17%	488
August	1st to 10th	Day	17% 5% 18% 22% 20% 18%	446
	11th to 20th	Day	8% 3 17% 31% 24% 17%	439
	21st to end	Day	11% 3 17% 26% 29% 15%	495
September	1st to 10th	Day	9% 4 15% 31% 27% 14%	450
	11th to 20th	Day	15% 6% 17% 24% 28% 10%	450
	21st to end	Day	14% 10% 18% 30% 23% 5%	450
October	1st to 10th	Day	18% 11% 18% 27% 19% 7%	450
	11th to 20th	Day	12% 18% 24% 27% 15% 3	450
	21st to end	Day	19% 15% 24% 28% 11% 3	495
November	1st to 10th	Day	17% 15% 29% 26% 11% 2	367
	11th to 20th	Day	21% 21% 34% 17% 5%	270
	21st to end	Day	17% 24% 34% 17% 7% 1	270
December	1st to 10th	Day	26% 28% 30% 14% 1	270
	11th to 20th	Day	23% 22% 32% 17% 6% 1	270
	21st to end	Day	25% 23% 36% 11% 5% 1	297
January	1st to 10th	Night	25% 22% 26% 22% 5%	760
	11th to 20th	Night	20% 22% 30% 23% 4	760
	21st to end	Night	20% 22% 33% 23% 3	836
February	1st to 10th	Night	18% 18% 31% 28% 4	760
	11th to 20th	Night	25% 26% 28% 20% 1	743
	21st to end	Night	22% 26% 30% 20% 2	628
March	1st to 10th	Night	18% 22% 30% 27% 4	723
	11th to 20th	Night	21% 18% 32% 21% 8% 1	720
	21st to end	Night	20% 17% 32% 23% 8%	792
April	1st to 10th	Night	17% 22% 27% 26% 8%	720
	11th to 20th	Night	17% 18% 26% 26% 12% 1	621
	21st to end	Night	14% 14% 21% 35% 15% 1	540
May	1st to 10th	Night	14% 11% 25% 32% 17% 1	540
	11th to 20th	Night	15% 9% 19% 32% 23% 2	531
	21st to end	Night	11% 4 14% 29% 34% 7%	584
June	1st to 10th	Night	9% 3 14% 36% 31% 6%	540
	11th to 20th	Night	7% 2 17% 28% 35% 11%	540
	21st to end	Night	6% 2 13% 35% 37% 7%	540
July	1st to 10th	Night	10% 3 8% 25% 46% 7%	525
	11th to 20th	Night	8% 3 7% 25% 44% 12%	522
	21st to end	Night	7% 2 7% 28% 45% 12%	591
August	1st to 10th	Night	10% 2 11% 24% 43% 10%	537
	11th to 20th	Night	12% 3 10% 27% 39% 9%	534
	21st to end	Night	10% 2 9% 29% 42% 9%	640
September	1st to 10th	Night	10% 3 14% 28% 38% 7%	720
	11th to 20th	Night	14% 5% 15% 27% 33% 6%	720
	21st to end	Night	14% 7% 17% 31% 28% 3	720
October	1st to 10th	Night	16% 10% 19% 24% 25% 7%	720
	11th to 20th	Night	15% 11% 26% 28% 18% 2	720
	21st to end	Night	16% 14% 19% 34% 15% 3	792
November	1st to 10th	Night	16% 10% 21% 33% 17% 3	740
	11th to 20th	Night	18% 14% 24% 33% 11% 1	760
	21st to end	Night	18% 16% 23% 30% 13% 1	760
December	1st to 10th	Night	23% 18% 25% 28% 6%	760
	11th to 20th	Night	17% 15% 29% 30% 7% 1	760
	21st to end	Night	23% 18% 26% 28% 6%	836

Page generated at 2024-02-27 06:30:18. Version ac07

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