Hendersonville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hendersonville clear sky chart from 2005-11-06 to 2026-08-30.

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 7% 5% 5% 5% 4 6% 8% 38%	143878
	Night	14% 7% 3 7% 4 4 4 4 5% 7% 40%	138412
Transparency	Day	42% 6% 12% 22% 15% 3	147569
	Night	41% 6% 11% 22% 17% 4	142795
Seeing	Day	16% 10% 23% 24% 19% 8%	17622
	Night	17% 8% 24% 30% 19% 3	27216

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	16% 12% 6% 10% 5% 4 4 3 4 5% 30%	4691
	11th to 20th	Day	14% 7% 3 10% 4 3 4 2 4 5% 44%	4971
	21st to end	Day	21% 9% 4 6% 4 4 4 3 5% 6% 34%	6291
February	1st to 10th	Day	18% 11% 4 8% 5% 4 4 3 3 7% 35%	2100
	11th to 20th	Day	22% 10% 3 8% 5% 3 4 3 4 6% 33%	2048
	21st to end	Day	20% 9% 3 7% 4 4 4 3 5% 5% 38%	1730
March	1st to 10th	Day	16% 12% 4 8% 5% 5% 4 3 4 5% 35%	4580
	11th to 20th	Day	13% 8% 2 7% 4 4 4 2 4 5% 46%	4891
	21st to end	Day	12% 7% 3 7% 5% 4 4 3 5% 7% 43%	5864
April	1st to 10th	Day	13% 7% 2 5% 5% 4 5% 3 5% 6% 46%	2520
	11th to 20th	Day	14% 7% 3 6% 4 4 4 3 5% 7% 43%	2494
	21st to end	Day	13% 7% 3 6% 6% 5% 5% 4 6% 7% 40%	2578
May	1st to 10th	Day	16% 8% 3 7% 5% 4 5% 4 6% 9% 32%	7616
	11th to 20th	Day	12% 8% 3 8% 5% 5% 5% 4 5% 7% 37%	7626
	21st to end	Day	17% 10% 4 9% 5% 4 5% 4 5% 6% 30%	8391
June	1st to 10th	Day	9% 6% 2 7% 4 6% 6% 4 6% 9% 42%	2731
	11th to 20th	Day	5% 5% 2 5% 4 5% 6% 5% 8% 10% 45%	2940
	21st to end	Day	4 4 2 5% 5% 6% 6% 6% 9% 12% 41%	2940
July	1st to 10th	Day	6% 5% 3 8% 6% 6% 6% 5% 8% 11% 35%	8280
	11th to 20th	Day	6% 6% 3 8% 6% 7% 8% 6% 10% 13% 27%	8083
	21st to end	Day	10% 7% 2 7% 5% 5% 6% 5% 8% 12% 31%	8340
August	1st to 10th	Day	4 3 2 5% 4 4 5% 5% 8% 9% 50%	4196
	11th to 20th	Day	6% 4 2 6% 5% 6% 7% 5% 8% 10% 40%	3969
	21st to end	Day	6% 3 1 5% 4 4 4 4 6% 9% 54%	4420
September	1st to 10th	Day	11% 6% 2 6% 4 5% 6% 5% 6% 8% 42%	2365
	11th to 20th	Day	12% 6% 2 6% 4 5% 4 3 6% 7% 47%	2200
	21st to end	Day	11% 5% 2 5% 4 4 4 4 5% 6% 48%	2200
October	1st to 10th	Day	10% 5% 2 5% 3 3 3 3 4 7% 55%	2200
	11th to 20th	Day	11% 6% 2 5% 3 3 2 3 4 7% 53%	2165
	21st to end	Day	17% 6% 2 6% 3 4 4 3 4 5% 46%	1981
November	1st to 10th	Day	12% 6% 2 5% 4 2 4 2 4 6% 53%	1852
	11th to 20th	Day	14% 7% 2 4 3 3 4 4 5% 7% 48%	1890
	21st to end	Day	14% 9% 2 7% 4 4 3 3 5% 5% 44%	1890
December	1st to 10th	Day	16% 8% 3 7% 3 4 5% 3 5% 6% 41%	3020
	11th to 20th	Day	21% 9% 4 8% 5% 4 4 3 3 7% 33%	3463
	21st to end	Day	19% 11% 5% 8% 5% 5% 5% 4 6% 7% 27%	4362
January	1st to 10th	Night	16% 10% 3 9% 5% 4 4 3 5% 5% 36%	8232
	11th to 20th	Night	16% 9% 2 7% 5% 4 4 4 4 5% 40%	7983
	21st to end	Night	18% 11% 3 9% 4 4 4 3 4 5% 35%	7888
February	1st to 10th	Night	21% 10% 3 9% 4 4 4 3 5% 5% 32%	2520
	11th to 20th	Night	24% 9% 3 6% 5% 3 3 2 5% 5% 35%	2458
	21st to end	Night	23% 8% 4 7% 4 3 3 3 5% 5% 34%	2076
March	1st to 10th	Night	20% 11% 3 6% 4 4 4 3 5% 6% 34%	5493
	11th to 20th	Night	11% 6% 2 5% 4 4 4 4 6% 6% 49%	5289
	21st to end	Night	13% 7% 3 7% 5% 4 4 3 6% 7% 41%	5336
April	1st to 10th	Night	12% 6% 2 6% 4 4 5% 3 5% 7% 46%	2100
	11th to 20th	Night	15% 7% 2 4 3 4 4 3 5% 7% 47%	2075
	21st to end	Night	13% 7% 3 6% 5% 4 4 3 6% 8% 42%	2041
May	1st to 10th	Night	14% 9% 4 9% 5% 5% 5% 4 5% 6% 34%	5237
	11th to 20th	Night	12% 8% 3 8% 6% 5% 5% 3 6% 8% 36%	5234
	21st to end	Night	15% 9% 3 9% 5% 5% 5% 4 6% 8% 30%	5761
June	1st to 10th	Night	8% 6% 2 6% 4 5% 4 4 7% 8% 46%	1882
	11th to 20th	Night	3 3 1 4 5% 5% 4 4 7% 10% 52%	1680
	21st to end	Night	4 4 2 5% 4 5% 5% 6% 7% 11% 48%	1680
July	1st to 10th	Night	6% 5% 2 6% 5% 5% 6% 5% 7% 12% 40%	4708
	11th to 20th	Night	6% 6% 2 7% 6% 6% 6% 5% 9% 13% 33%	4878
	21st to end	Night	7% 7% 3 8% 6% 6% 5% 6% 8% 13% 32%	5736
August	1st to 10th	Night	4 3 1 4 4 4 4 3 6% 9% 58%	3169
	11th to 20th	Night	4 4 1 5% 4 4 5% 5% 8% 13% 48%	3300
	21st to end	Night	4 3 1 4 3 3 5% 4 6% 8% 58%	3676
September	1st to 10th	Night	9% 5% 2 6% 5% 4 4 4 5% 6% 49%	2015
	11th to 20th	Night	9% 5% 3 7% 4 4 4 3 6% 7% 48%	2200
	21st to end	Night	11% 5% 2 5% 4 4 4 3 6% 6% 51%	2200
October	1st to 10th	Night	9% 4 2 4 3 3 3 3 4 7% 60%	2200
	11th to 20th	Night	13% 5% 2 5% 3 4 3 2 4 7% 52%	2230
	21st to end	Night	15% 7% 2 5% 3 3 3 3 4 6% 49%	2856
November	1st to 10th	Night	13% 5% 2 5% 4 3 4 3 5% 5% 51%	2666
	11th to 20th	Night	13% 6% 2 5% 3 3 3 3 5% 7% 49%	2730
	21st to end	Night	17% 7% 3 5% 4 3 4 3 5% 6% 44%	2730
December	1st to 10th	Night	18% 10% 3 8% 4 3 4 4 4 5% 37%	4380
	11th to 20th	Night	24% 8% 2 5% 3 3 3 3 3 5% 39%	4952
	21st to end	Night	19% 12% 4 9% 5% 5% 4 3 5% 5% 27%	6821

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	55% 5% 12% 19% 8% 1	4692
	11th to 20th	Day	43% 4 5% 26% 20% 1	4971
	21st to end	Day	51% 3 8% 21% 13% 4	6291
February	1st to 10th	Day	52% 3 9% 21% 12% 2	2100
	11th to 20th	Day	54% 4 8% 18% 13% 3	2058
	21st to end	Day	49% 4 9% 18% 15% 6%	1730
March	1st to 10th	Day	51% 5% 6% 14% 16% 8%	4580
	11th to 20th	Day	40% 5% 8% 22% 19% 6%	4891
	21st to end	Day	41% 5% 10% 29% 15% 1	5866
April	1st to 10th	Day	37% 6% 11% 23% 19% 3	2520
	11th to 20th	Day	39% 6% 8% 22% 20% 5%	2494
	21st to end	Day	42% 7% 10% 24% 15% 2	2578
May	1st to 10th	Day	47% 6% 14% 21% 10% 1	7651
	11th to 20th	Day	45% 6% 13% 21% 13% 1	7630
	21st to end	Day	53% 7% 9% 16% 13% 2	8405
June	1st to 10th	Day	37% 9% 12% 22% 17% 3	2731
	11th to 20th	Day	30% 10% 17% 22% 18% 3	2940
	21st to end	Day	30% 11% 17% 23% 15% 4	2940
July	1st to 10th	Day	39% 7% 18% 25% 10% 1	8211
	11th to 20th	Day	44% 7% 22% 21% 5% 1	8008
	21st to end	Day	44% 5% 22% 21% 7% 1	8156
August	1st to 10th	Day	26% 8% 15% 32% 18% 1	4183
	11th to 20th	Day	35% 7% 14% 27% 16% 1	4005
	21st to end	Day	26% 7% 11% 32% 22% 2	4419
September	1st to 10th	Day	38% 9% 11% 19% 19% 4	2365
	11th to 20th	Day	37% 6% 10% 24% 21% 2	2200
	21st to end	Day	35% 6% 11% 22% 22% 4	2200
October	1st to 10th	Day	22% 4 6% 18% 41% 9%	3590
	11th to 20th	Day	23% 4 7% 25% 29% 13%	3509
	21st to end	Day	31% 4 7% 24% 27% 8%	3181
November	1st to 10th	Day	33% 4 8% 25% 24% 5%	1852
	11th to 20th	Day	36% 4 8% 24% 22% 5%	1890
	21st to end	Day	42% 4 7% 24% 18% 4	1890
December	1st to 10th	Day	45% 4 7% 25% 18% 1	3020
	11th to 20th	Day	53% 4 9% 20% 11% 2	3460
	21st to end	Day	54% 6% 12% 21% 6% 1	4362
January	1st to 10th	Night	48% 5% 15% 20% 11% 1	8233
	11th to 20th	Night	44% 6% 5% 20% 21% 3	7983
	21st to end	Night	52% 3 7% 19% 14% 5%	7888
February	1st to 10th	Night	54% 4 9% 18% 14% 1	2520
	11th to 20th	Night	53% 3 7% 20% 14% 4	2459
	21st to end	Night	52% 5% 7% 15% 17% 4	2076
March	1st to 10th	Night	49% 6% 7% 15% 18% 5%	5493
	11th to 20th	Night	34% 5% 9% 21% 20% 12%	5289
	21st to end	Night	42% 5% 10% 27% 15% 2	5336
April	1st to 10th	Night	37% 6% 12% 23% 20% 3	2100
	11th to 20th	Night	36% 5% 10% 20% 22% 7%	2075
	21st to end	Night	39% 7% 10% 25% 17% 2	2041
May	1st to 10th	Night	48% 6% 13% 20% 12% 1	5264
	11th to 20th	Night	45% 7% 14% 16% 16% 1	5235
	21st to end	Night	50% 8% 13% 17% 10% 1	5771
June	1st to 10th	Night	34% 8% 13% 26% 16% 4	1882
	11th to 20th	Night	25% 6% 18% 30% 19% 3	1680
	21st to end	Night	27% 10% 17% 27% 15% 4	1680
July	1st to 10th	Night	36% 7% 20% 25% 11% 1	4670
	11th to 20th	Night	39% 8% 24% 21% 5% 1	4833
	21st to end	Night	43% 5% 24% 20% 7% 1	5606
August	1st to 10th	Night	23% 6% 11% 37% 22% 1	3158
	11th to 20th	Night	26% 7% 20% 31% 14% 1	3330
	21st to end	Night	22% 6% 12% 34% 24% 3	3676
September	1st to 10th	Night	34% 7% 12% 22% 20% 5%	2015
	11th to 20th	Night	34% 6% 11% 23% 24% 3	2200
	21st to end	Night	32% 6% 11% 21% 24% 7%	2200
October	1st to 10th	Night	22% 4 6% 19% 39% 11%	3590
	11th to 20th	Night	21% 5% 6% 23% 31% 14%	3625
	21st to end	Night	26% 4 8% 24% 30% 10%	4606
November	1st to 10th	Night	34% 4 8% 23% 23% 7%	2666
	11th to 20th	Night	33% 5% 8% 22% 25% 7%	2730
	21st to end	Night	42% 4 8% 24% 18% 4	2730
December	1st to 10th	Night	49% 6% 6% 17% 20% 2	4380
	11th to 20th	Night	47% 4 7% 21% 18% 2	4954
	21st to end	Night	56% 6% 9% 19% 8% 1	6821

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	23% 21% 31% 18% 5% 1	330
	11th to 20th	Day	27% 25% 29% 15% 4 1	330
	21st to end	Day	23% 21% 41% 13% 2	363
February	1st to 10th	Day	26% 18% 35% 17% 2 1	330
	11th to 20th	Day	35% 24% 30% 8% 3	330
	21st to end	Day	30% 21% 35% 11% 3	273
March	1st to 10th	Day	26% 20% 35% 15% 4 1	330
	11th to 20th	Day	24% 20% 33% 16% 6%	445
	21st to end	Day	25% 16% 34% 18% 7%	594
April	1st to 10th	Day	22% 14% 29% 26% 8% 1	540
	11th to 20th	Day	20% 14% 31% 22% 11% 2	532
	21st to end	Day	19% 14% 31% 21% 13% 2	540
May	1st to 10th	Day	21% 13% 29% 22% 12% 3	543
	11th to 20th	Day	15% 7% 30% 24% 17% 6%	567
	21st to end	Day	14% 5% 21% 26% 20% 12%	617
June	1st to 10th	Day	12% 5% 19% 25% 24% 14%	571
	11th to 20th	Day	7% 4 18% 29% 30% 13%	780
	21st to end	Day	5% 3 18% 33% 24% 16%	780
July	1st to 10th	Day	8% 3 11% 29% 30% 19%	771
	11th to 20th	Day	9% 2 9% 26% 36% 18%	701
	21st to end	Day	9% 3 11% 27% 31% 20%	620
August	1st to 10th	Day	9% 4 9% 27% 33% 18%	566
	11th to 20th	Day	9% 3 13% 33% 30% 13%	559
	21st to end	Day	11% 2 10% 22% 35% 20%	619
September	1st to 10th	Day	12% 3 11% 29% 31% 15%	530
	11th to 20th	Day	13% 3 9% 28% 30% 18%	530
	21st to end	Day	16% 6% 17% 25% 28% 8%	530
October	1st to 10th	Day	12% 4 20% 27% 28% 8%	530
	11th to 20th	Day	14% 12% 28% 26% 16% 3	495
	21st to end	Day	23% 12% 28% 28% 8% 1	363
November	1st to 10th	Day	18% 11% 29% 27% 13% 2	330
	11th to 20th	Day	15% 20% 35% 23% 8%	330
	21st to end	Day	20% 15% 34% 22% 7% 2	330
December	1st to 10th	Day	25% 17% 30% 23% 5%	330
	11th to 20th	Day	23% 18% 32% 18% 9%	330
	21st to end	Day	27% 18% 33% 17% 4	363
January	1st to 10th	Night	24% 15% 28% 28% 4	1050
	11th to 20th	Night	27% 15% 31% 23% 4	948
	21st to end	Night	21% 14% 38% 24% 3	924
February	1st to 10th	Night	25% 13% 33% 25% 4	840
	11th to 20th	Night	28% 15% 34% 21% 3	823
	21st to end	Night	28% 16% 33% 22% 1	692
March	1st to 10th	Night	22% 14% 32% 27% 5%	840
	11th to 20th	Night	21% 13% 32% 27% 6% 1	840
	21st to end	Night	20% 11% 34% 28% 7%	814
April	1st to 10th	Night	15% 11% 32% 32% 9%	630
	11th to 20th	Night	19% 9% 32% 29% 11%	623
	21st to end	Night	18% 7% 31% 31% 12% 2	630
May	1st to 10th	Night	13% 6% 33% 31% 17% 1	630
	11th to 20th	Night	11% 4 25% 36% 19% 5%	621
	21st to end	Night	10% 2 17% 37% 28% 5%	683
June	1st to 10th	Night	12% 3 15% 39% 28% 4	630
	11th to 20th	Night	5% 1 11% 39% 37% 6%	630
	21st to end	Night	5% 1 12% 35% 39% 7%	630
July	1st to 10th	Night	9% 3 6% 30% 41% 11%	615
	11th to 20th	Night	8% 2 6% 29% 45% 11%	612
	21st to end	Night	9% 2 7% 31% 43% 8%	690
August	1st to 10th	Night	7% 1 5% 32% 46% 9%	627
	11th to 20th	Night	6% 2 8% 38% 40% 7%	624
	21st to end	Night	8% 1 8% 31% 43% 8%	687
September	1st to 10th	Night	10% 1 11% 33% 39% 6%	615
	11th to 20th	Night	12% 3 12% 30% 38% 6%	800
	21st to end	Night	13% 2 16% 29% 35% 4	800
October	1st to 10th	Night	10% 5% 18% 32% 29% 5%	800
	11th to 20th	Night	17% 6% 21% 35% 19% 1	800
	21st to end	Night	18% 9% 27% 29% 16% 1	880
November	1st to 10th	Night	16% 6% 22% 36% 17% 2	820
	11th to 20th	Night	16% 10% 32% 32% 10% 1	840
	21st to end	Night	21% 10% 27% 32% 10% 1	840
December	1st to 10th	Night	28% 10% 28% 28% 6%	840
	11th to 20th	Night	24% 9% 32% 29% 7% 1	840
	21st to end	Night	29% 12% 28% 26% 5%	1008

Page generated at 2026-08-27 03:07:10. Version ac07

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