Mount Mitchell
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Mitchell clear sky chart from 2005-11-06 to 2025-11-18.

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% 6% 2 7% 5% 5% 5% 4 6% 8% 37%	126842
	Night	13% 6% 2 6% 4 4 4 4 6% 8% 42%	123544
Transparency	Day	42% 7% 13% 18% 15% 6%	130540
	Night	37% 7% 14% 20% 16% 6%	127915
Seeing	Day	23% 15% 25% 20% 12% 6%	16471
	Night	20% 13% 22% 25% 16% 3	26508

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% 5% 2 5% 3 3 3 3 6% 8% 52%	4056
	11th to 20th	Day	9% 6% 2 5% 3 3 3 3 3 6% 57%	4060
	21st to end	Day	17% 6% 2 5% 4 4 4 3 4 6% 44%	4466
February	1st to 10th	Day	13% 8% 3 5% 5% 4 4 4 6% 8% 40%	1858
	11th to 20th	Day	17% 9% 2 6% 4 4 4 3 4 6% 40%	1948
	21st to end	Day	15% 8% 2 7% 4 5% 4 4 5% 6% 39%	1650
March	1st to 10th	Day	18% 6% 2 5% 4 4 4 3 5% 6% 43%	4862
	11th to 20th	Day	11% 6% 2 5% 3 3 3 3 4 6% 53%	4980
	21st to end	Day	16% 7% 2 6% 4 4 4 3 5% 6% 43%	5465
April	1st to 10th	Day	11% 6% 2 4 4 5% 5% 5% 6% 9% 41%	2200
	11th to 20th	Day	15% 7% 2 5% 4 4 5% 4 6% 8% 41%	2392
	21st to end	Day	15% 6% 2 6% 4 4 4 4 5% 7% 43%	2600
May	1st to 10th	Day	12% 7% 3 8% 7% 6% 6% 5% 7% 8% 31%	5862
	11th to 20th	Day	20% 7% 2 8% 5% 6% 7% 5% 7% 8% 24%	5861
	21st to end	Day	15% 6% 2 6% 5% 5% 5% 5% 8% 9% 35%	6433
June	1st to 10th	Day	13% 7% 2 8% 6% 7% 7% 5% 7% 10% 30%	2600
	11th to 20th	Day	9% 5% 3 8% 8% 7% 6% 5% 7% 10% 30%	2600
	21st to end	Day	9% 7% 3 8% 7% 7% 6% 5% 8% 9% 33%	2600
July	1st to 10th	Day	7% 6% 2 8% 6% 7% 8% 5% 8% 10% 32%	5900
	11th to 20th	Day	8% 7% 3 10% 8% 7% 8% 6% 10% 11% 22%	5900
	21st to end	Day	12% 8% 4 11% 8% 8% 8% 7% 8% 8% 18%	6424
August	1st to 10th	Day	16% 8% 3 8% 7% 7% 6% 6% 9% 9% 21%	4234
	11th to 20th	Day	10% 6% 2 8% 7% 6% 7% 6% 9% 12% 28%	4174
	21st to end	Day	9% 6% 2 8% 6% 7% 6% 5% 7% 8% 37%	4361
September	1st to 10th	Day	13% 8% 3 7% 6% 5% 6% 5% 7% 8% 33%	2200
	11th to 20th	Day	19% 7% 3 6% 6% 5% 7% 5% 6% 7% 29%	2200
	21st to end	Day	19% 8% 3 6% 5% 5% 4 4 6% 6% 34%	2200
October	1st to 10th	Day	16% 6% 2 6% 3 3 4 3 4 7% 46%	2146
	11th to 20th	Day	12% 6% 2 5% 3 3 3 2 5% 6% 54%	2000
	21st to end	Day	15% 5% 2 4 3 3 3 3 4 6% 53%	2200
November	1st to 10th	Day	11% 6% 2 4 3 4 3 2 5% 6% 54%	1978
	11th to 20th	Day	11% 6% 2 4 4 4 3 4 5% 7% 51%	1863
	21st to end	Day	14% 5% 2 5% 4 4 3 3 4 8% 48%	1800
December	1st to 10th	Day	11% 5% 2 6% 3 5% 4 3 5% 7% 49%	2930
	11th to 20th	Day	14% 5% 2 5% 5% 5% 5% 4 6% 7% 43%	3373
	21st to end	Day	19% 7% 3 3 3 4 3 3 4 7% 43%	4466
January	1st to 10th	Night	12% 5% 1 4 3 3 4 3 5% 8% 52%	5889
	11th to 20th	Night	10% 6% 2 5% 3 3 4 3 5% 5% 53%	5900
	21st to end	Night	15% 7% 2 5% 4 4 4 3 5% 6% 47%	6490
February	1st to 10th	Night	12% 7% 2 4 5% 4 5% 4 6% 8% 43%	2539
	11th to 20th	Night	17% 8% 2 6% 4 4 4 3 4 6% 41%	2338
	21st to end	Night	14% 7% 3 6% 5% 5% 5% 4 6% 8% 39%	1980
March	1st to 10th	Night	18% 8% 2 5% 4 3 4 4 5% 8% 39%	4990
	11th to 20th	Night	10% 4 2 5% 3 3 4 3 6% 9% 50%	4980
	21st to end	Night	16% 5% 1 5% 4 4 4 4 6% 8% 43%	5467
April	1st to 10th	Night	12% 7% 3 5% 4 4 3 4 6% 7% 45%	2200
	11th to 20th	Night	14% 6% 2 5% 3 3 4 3 6% 8% 47%	1972
	21st to end	Night	13% 7% 2 5% 4 4 4 3 5% 7% 46%	1800
May	1st to 10th	Night	13% 7% 3 6% 5% 5% 5% 5% 8% 11% 33%	4033
	11th to 20th	Night	22% 6% 2 7% 5% 4 5% 5% 7% 10% 27%	4032
	21st to end	Night	16% 5% 2 5% 4 4 4 4 8% 11% 37%	4421
June	1st to 10th	Night	11% 8% 2 6% 5% 5% 6% 6% 7% 11% 33%	1800
	11th to 20th	Night	10% 5% 3 6% 5% 5% 6% 4 7% 10% 39%	1800
	21st to end	Night	8% 5% 2 6% 5% 5% 6% 5% 8% 11% 41%	1800
July	1st to 10th	Night	8% 6% 2 6% 5% 5% 6% 5% 8% 11% 37%	4058
	11th to 20th	Night	8% 6% 2 7% 5% 6% 6% 5% 8% 14% 33%	4057
	21st to end	Night	11% 8% 3 9% 7% 6% 7% 5% 8% 11% 24%	4427
August	1st to 10th	Night	13% 9% 3 7% 5% 5% 6% 5% 8% 9% 31%	2915
	11th to 20th	Night	10% 7% 3 8% 5% 6% 6% 5% 7% 11% 32%	2875
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 6% 9% 46%	3498
September	1st to 10th	Night	12% 9% 3 7% 4 5% 5% 3 6% 8% 39%	2200
	11th to 20th	Night	20% 8% 2 6% 5% 4 4 3 5% 7% 35%	2200
	21st to end	Night	21% 7% 2 6% 3 4 4 2 4 6% 42%	2200
October	1st to 10th	Night	17% 7% 2 5% 3 3 4 3 5% 6% 45%	2252
	11th to 20th	Night	14% 7% 2 4 3 4 4 3 5% 5% 50%	2400
	21st to end	Night	14% 5% 1 4 3 3 3 2 5% 6% 54%	2640
November	1st to 10th	Night	13% 6% 2 5% 3 3 3 3 6% 5% 51%	2537
	11th to 20th	Night	12% 6% 1 4 3 4 4 4 5% 7% 50%	2692
	21st to end	Night	12% 5% 2 5% 4 3 4 4 6% 6% 47%	2600
December	1st to 10th	Night	11% 5% 2 6% 4 4 4 3 7% 7% 48%	4250
	11th to 20th	Night	13% 9% 3 8% 5% 5% 5% 3 5% 6% 40%	4822
	21st to end	Night	20% 5% 3 4 3 4 4 3 5% 7% 42%	6490

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	29% 4 7% 20% 32% 7%	4057
	11th to 20th	Day	29% 6% 6% 15% 32% 11%	4060
	21st to end	Day	41% 3 8% 17% 22% 8%	4466
February	1st to 10th	Day	41% 5% 12% 20% 18% 4	1858
	11th to 20th	Day	46% 4 11% 18% 17% 5%	1958
	21st to end	Day	44% 6% 9% 16% 19% 6%	1650
March	1st to 10th	Day	42% 4 7% 17% 18% 12%	4862
	11th to 20th	Day	32% 4 8% 18% 20% 19%	4980
	21st to end	Day	41% 4 10% 25% 15% 6%	5465
April	1st to 10th	Day	37% 7% 12% 22% 18% 4	2200
	11th to 20th	Day	40% 5% 10% 21% 19% 6%	2392
	21st to end	Day	41% 5% 13% 25% 14% 2	2600
May	1st to 10th	Day	47% 9% 14% 19% 10% 1	5897
	11th to 20th	Day	52% 9% 15% 16% 7% 1	5865
	21st to end	Day	41% 8% 17% 17% 15% 2	6447
June	1st to 10th	Day	47% 9% 18% 17% 8% 1	2600
	11th to 20th	Day	45% 9% 17% 16% 11% 1	2600
	21st to end	Day	45% 8% 17% 18% 10% 2	2600
July	1st to 10th	Day	44% 11% 17% 19% 8%	5835
	11th to 20th	Day	52% 12% 22% 10% 4	5831
	21st to end	Day	60% 11% 15% 10% 5%	6240
August	1st to 10th	Day	54% 10% 17% 16% 3	4221
	11th to 20th	Day	45% 10% 23% 13% 6% 4	4213
	21st to end	Day	42% 8% 17% 26% 5% 2	4361
September	1st to 10th	Day	46% 8% 12% 17% 14% 3	2200
	11th to 20th	Day	50% 7% 10% 18% 13% 2	2200
	21st to end	Day	48% 7% 12% 17% 13% 4	2200
October	1st to 10th	Day	31% 4 10% 15% 29% 11%	3497
	11th to 20th	Day	23% 3 5% 20% 24% 25%	3240
	21st to end	Day	26% 5% 7% 27% 20% 16%	3538
November	1st to 10th	Day	32% 3 10% 21% 25% 8%	1978
	11th to 20th	Day	33% 4 8% 22% 25% 9%	1863
	21st to end	Day	36% 4 7% 25% 23% 6%	1800
December	1st to 10th	Day	35% 4 9% 18% 26% 9%	2930
	11th to 20th	Day	39% 4 13% 19% 20% 6%	3370
	21st to end	Day	40% 3 11% 26% 16% 3	4466
January	1st to 10th	Night	30% 5% 9% 23% 21% 13%	5889
	11th to 20th	Night	33% 4 8% 17% 25% 13%	5900
	21st to end	Night	39% 3 8% 14% 24% 12%	6490
February	1st to 10th	Night	38% 5% 13% 22% 19% 3	2539
	11th to 20th	Night	44% 5% 9% 21% 16% 5%	2339
	21st to end	Night	41% 6% 11% 19% 16% 6%	1980
March	1st to 10th	Night	42% 6% 7% 16% 19% 10%	4990
	11th to 20th	Night	30% 5% 8% 22% 19% 17%	4980
	21st to end	Night	39% 5% 14% 25% 12% 6%	5467
April	1st to 10th	Night	37% 6% 13% 23% 17% 4	2200
	11th to 20th	Night	36% 5% 12% 22% 21% 5%	1972
	21st to end	Night	37% 7% 15% 26% 14% 2	1800
May	1st to 10th	Night	41% 11% 17% 22% 7% 1	4060
	11th to 20th	Night	48% 9% 20% 18% 6%	4033
	21st to end	Night	37% 8% 22% 23% 10% 1	4429
June	1st to 10th	Night	40% 11% 20% 20% 8% 1	1800
	11th to 20th	Night	37% 10% 23% 22% 8% 1	1800
	21st to end	Night	34% 11% 20% 20% 13% 2	1800
July	1st to 10th	Night	38% 12% 22% 22% 6%	4015
	11th to 20th	Night	37% 15% 31% 13% 3 1	4006
	21st to end	Night	49% 13% 21% 11% 5%	4297
August	1st to 10th	Night	45% 10% 25% 14% 4	2904
	11th to 20th	Night	42% 9% 25% 16% 7% 1	2902
	21st to end	Night	34% 7% 20% 30% 8% 1	3498
September	1st to 10th	Night	42% 10% 13% 18% 14% 3	2200
	11th to 20th	Night	48% 7% 12% 18% 15% 1	2200
	21st to end	Night	44% 6% 10% 21% 16% 3	2200
October	1st to 10th	Night	29% 6% 12% 18% 22% 13%	3681
	11th to 20th	Night	23% 3 7% 22% 23% 21%	3899
	21st to end	Night	28% 6% 6% 23% 22% 15%	4252
November	1st to 10th	Night	34% 5% 10% 22% 21% 8%	2537
	11th to 20th	Night	33% 4 7% 21% 25% 9%	2692
	21st to end	Night	35% 5% 7% 25% 23% 6%	2600
December	1st to 10th	Night	34% 4 11% 20% 22% 8%	4250
	11th to 20th	Night	44% 4 10% 19% 17% 6%	4824
	21st to end	Night	39% 5% 14% 22% 18% 3	6490

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	41% 24% 27% 7% 1	300
	11th to 20th	Day	40% 21% 28% 9% 1	300
	21st to end	Day	35% 32% 27% 6% 1	330
February	1st to 10th	Day	31% 27% 31% 9% 1	300
	11th to 20th	Day	50% 22% 25% 3	300
	21st to end	Day	40% 30% 24% 5% 1	249
March	1st to 10th	Day	30% 24% 27% 15% 3	464
	11th to 20th	Day	29% 26% 28% 13% 3 1	500
	21st to end	Day	30% 26% 27% 12% 5%	550
April	1st to 10th	Day	28% 22% 23% 19% 6% 1	500
	11th to 20th	Day	23% 23% 26% 19% 8% 2	492
	21st to end	Day	24% 16% 29% 17% 11% 3	500
May	1st to 10th	Day	22% 20% 30% 16% 7% 5%	503
	11th to 20th	Day	26% 13% 24% 18% 12% 6%	527
	21st to end	Day	21% 10% 24% 20% 14% 10%	573
June	1st to 10th	Day	16% 11% 25% 26% 13% 8%	530
	11th to 20th	Day	12% 8% 25% 26% 19% 10%	530
	21st to end	Day	10% 10% 29% 26% 14% 10%	530
July	1st to 10th	Day	11% 5% 19% 30% 24% 12%	525
	11th to 20th	Day	11% 3 16% 30% 24% 15%	524
	21st to end	Day	12% 5% 15% 32% 24% 13%	576
August	1st to 10th	Day	21% 8% 21% 23% 14% 13%	526
	11th to 20th	Day	13% 7% 16% 30% 22% 12%	519
	21st to end	Day	13% 5% 19% 29% 19% 14%	583
September	1st to 10th	Day	14% 5% 21% 29% 21% 11%	530
	11th to 20th	Day	22% 7% 18% 22% 23% 8%	530
	21st to end	Day	26% 9% 20% 25% 15% 4	530
October	1st to 10th	Day	22% 11% 22% 24% 15% 7%	530
	11th to 20th	Day	16% 15% 31% 24% 11% 3	530
	21st to end	Day	25% 12% 29% 23% 9% 2	583
November	1st to 10th	Day	23% 15% 33% 18% 8% 2	456
	11th to 20th	Day	26% 20% 34% 15% 4 1	321
	21st to end	Day	25% 23% 30% 16% 5% 1	300
December	1st to 10th	Day	32% 27% 30% 10% 1	300
	11th to 20th	Day	25% 19% 38% 15% 2 1	300
	21st to end	Day	30% 17% 37% 12% 3 1	330
January	1st to 10th	Night	29% 20% 27% 20% 5%	800
	11th to 20th	Night	27% 19% 30% 21% 4	800
	21st to end	Night	24% 22% 31% 20% 3	880
February	1st to 10th	Night	21% 19% 31% 25% 4	800
	11th to 20th	Night	28% 26% 27% 17% 2	783
	21st to end	Night	24% 25% 32% 16% 2	660
March	1st to 10th	Night	23% 22% 28% 23% 4	800
	11th to 20th	Night	25% 18% 31% 18% 7% 1	800
	21st to end	Night	24% 19% 30% 19% 7%	880
April	1st to 10th	Night	23% 19% 27% 23% 7% 1	800
	11th to 20th	Night	22% 19% 24% 23% 11% 2	713
	21st to end	Night	16% 14% 25% 32% 13% 1	600
May	1st to 10th	Night	15% 15% 29% 25% 14% 2	600
	11th to 20th	Night	20% 10% 20% 28% 20% 2	591
	21st to end	Night	18% 7% 15% 26% 28% 6%	650
June	1st to 10th	Night	13% 5% 19% 32% 26% 6%	600
	11th to 20th	Night	9% 5% 18% 29% 29% 10%	600
	21st to end	Night	7% 5% 15% 34% 33% 6%	600
July	1st to 10th	Night	12% 3 9% 31% 38% 6%	585
	11th to 20th	Night	10% 3 10% 28% 39% 9%	582
	21st to end	Night	9% 3 9% 31% 37% 10%	657
August	1st to 10th	Night	16% 4 10% 28% 36% 6%	597
	11th to 20th	Night	15% 5% 11% 26% 36% 8%	594
	21st to end	Night	15% 4 9% 26% 37% 9%	727
September	1st to 10th	Night	17% 4 13% 24% 35% 7%	800
	11th to 20th	Night	22% 6% 10% 24% 31% 6%	800
	21st to end	Night	25% 7% 15% 28% 24% 3	800
October	1st to 10th	Night	20% 11% 17% 21% 23% 8%	800
	11th to 20th	Night	21% 14% 22% 27% 14% 3	800
	21st to end	Night	21% 12% 20% 31% 11% 3	880
November	1st to 10th	Night	21% 13% 22% 27% 15% 3	820
	11th to 20th	Night	23% 15% 21% 30% 9% 2	829
	21st to end	Night	22% 15% 23% 29% 10% 2	800
December	1st to 10th	Night	26% 17% 26% 25% 6%	800
	11th to 20th	Night	22% 15% 28% 28% 7% 1	800
	21st to end	Night	28% 15% 25% 28% 4	880

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