Cumberland Mountain State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cumberland Mountain State Park clear sky chart from 2005-11-06 to 2026-03-03.

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% 8% 3 8% 5% 5% 5% 4 6% 7% 36%	131023
	Night	13% 8% 3 7% 4 4 4 3 5% 7% 40%	130161
Transparency	Day	43% 8% 10% 20% 15% 3	134748
	Night	41% 7% 11% 21% 16% 4	134492
Seeing	Day	18% 14% 25% 22% 15% 7%	16393
	Night	16% 12% 24% 27% 17% 3	26504

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	17% 10% 6% 9% 4 4 4 3 5% 5% 32%	5258
	11th to 20th	Day	12% 7% 3 14% 4 3 3 2 3 4 45%	5280
	21st to end	Day	19% 9% 5% 8% 4 3 4 3 5% 5% 35%	5960
February	1st to 10th	Day	16% 12% 3 8% 5% 4 4 4 4 6% 34%	2100
	11th to 20th	Day	21% 10% 5% 8% 5% 3 4 3 4 6% 31%	2048
	21st to end	Day	18% 10% 3 10% 4 4 3 3 4 6% 35%	1730
March	1st to 10th	Day	17% 12% 4 8% 4 4 4 3 5% 6% 31%	4515
	11th to 20th	Day	12% 9% 3 7% 4 4 4 3 4 5% 45%	4980
	21st to end	Day	13% 9% 3 7% 5% 4 4 3 5% 6% 41%	5465
April	1st to 10th	Day	12% 8% 3 6% 6% 4 4 4 6% 7% 40%	2362
	11th to 20th	Day	13% 9% 3 6% 4 5% 4 3 5% 6% 43%	2374
	21st to end	Day	13% 7% 3 7% 6% 5% 4 4 6% 7% 38%	2555
May	1st to 10th	Day	17% 11% 4 8% 5% 5% 5% 4 7% 8% 27%	5862
	11th to 20th	Day	15% 10% 4 10% 6% 5% 6% 4 6% 7% 28%	5861
	21st to end	Day	14% 9% 3 8% 5% 5% 5% 3 5% 7% 35%	6433
June	1st to 10th	Day	10% 6% 3 7% 5% 5% 6% 5% 8% 10% 35%	2600
	11th to 20th	Day	5% 5% 2 7% 7% 7% 7% 5% 7% 10% 39%	2600
	21st to end	Day	7% 5% 2 6% 6% 6% 6% 6% 8% 13% 36%	2600
July	1st to 10th	Day	6% 5% 2 7% 6% 6% 7% 6% 8% 10% 37%	5900
	11th to 20th	Day	8% 6% 3 9% 7% 7% 8% 6% 8% 10% 27%	5900
	21st to end	Day	11% 10% 4 11% 8% 7% 6% 6% 7% 9% 22%	6424
August	1st to 10th	Day	6% 5% 3 7% 5% 6% 6% 7% 8% 11% 37%	4234
	11th to 20th	Day	7% 5% 2 7% 6% 6% 7% 6% 8% 11% 33%	3918
	21st to end	Day	6% 5% 2 7% 5% 5% 6% 6% 8% 9% 42%	4312
September	1st to 10th	Day	13% 7% 3 7% 4 6% 6% 4 6% 7% 37%	2270
	11th to 20th	Day	13% 7% 2 7% 5% 4 5% 4 6% 7% 39%	2200
	21st to end	Day	15% 6% 2 6% 4 5% 4 4 5% 6% 43%	2200
October	1st to 10th	Day	10% 5% 2 6% 3 4 4 3 5% 5% 52%	2200
	11th to 20th	Day	11% 6% 2 5% 3 3 3 3 4 5% 54%	2107
	21st to end	Day	15% 7% 2 5% 3 3 4 4 5% 7% 46%	2095
November	1st to 10th	Day	9% 7% 2 5% 4 4 5% 3 4 6% 52%	1852
	11th to 20th	Day	11% 9% 2 6% 4 4 4 3 5% 6% 46%	1890
	21st to end	Day	14% 9% 3 7% 5% 4 3 3 5% 6% 42%	1890
December	1st to 10th	Day	13% 9% 4 7% 4 4 4 4 4 5% 42%	3020
	11th to 20th	Day	18% 11% 6% 10% 5% 4 4 4 5% 5% 28%	3463
	21st to end	Day	17% 11% 6% 8% 4 4 4 3 6% 8% 29%	4565
January	1st to 10th	Night	15% 11% 5% 9% 3 3 3 3 4 6% 38%	7635
	11th to 20th	Night	14% 9% 4 8% 5% 4 3 2 3 5% 44%	7680
	21st to end	Night	17% 12% 5% 8% 4 3 3 2 3 5% 37%	8203
February	1st to 10th	Night	15% 10% 4 8% 5% 4 4 4 5% 7% 34%	2520
	11th to 20th	Night	21% 10% 4 8% 5% 4 4 3 4 4 33%	2458
	21st to end	Night	20% 10% 4 7% 5% 4 4 3 5% 5% 33%	2076
March	1st to 10th	Night	17% 12% 5% 8% 5% 4 4 3 5% 6% 32%	5381
	11th to 20th	Night	10% 7% 2 6% 4 3 4 4 5% 6% 48%	4980
	21st to end	Night	14% 8% 3 8% 5% 5% 4 4 4 6% 39%	5467
April	1st to 10th	Night	12% 6% 3 6% 4 4 5% 4 6% 7% 44%	2054
	11th to 20th	Night	12% 7% 2 6% 3 3 4 3 5% 7% 47%	1975
	21st to end	Night	11% 7% 2 6% 5% 4 4 4 6% 7% 43%	1845
May	1st to 10th	Night	13% 10% 4 8% 5% 5% 5% 5% 6% 9% 29%	4033
	11th to 20th	Night	16% 10% 4 10% 6% 5% 5% 4 5% 6% 29%	4032
	21st to end	Night	13% 8% 3 8% 5% 5% 5% 4 5% 8% 37%	4421
June	1st to 10th	Night	6% 7% 2 6% 6% 5% 5% 4 7% 8% 43%	1800
	11th to 20th	Night	4 3 2 5% 4 5% 5% 4 7% 12% 50%	1800
	21st to end	Night	5% 6% 2 6% 6% 5% 5% 4 7% 12% 42%	1800
July	1st to 10th	Night	6% 6% 2 6% 4 5% 5% 5% 9% 10% 41%	4058
	11th to 20th	Night	8% 5% 2 6% 5% 5% 5% 5% 8% 13% 38%	4057
	21st to end	Night	9% 8% 4 9% 6% 5% 6% 5% 9% 12% 28%	4427
August	1st to 10th	Night	4 5% 2 6% 4 4 4 4 8% 11% 49%	2915
	11th to 20th	Night	6% 6% 3 6% 5% 4 4 4 7% 11% 45%	3127
	21st to end	Night	5% 4 1 4 3 3 4 4 6% 9% 56%	3586
September	1st to 10th	Night	9% 7% 3 6% 4 5% 5% 3 6% 7% 44%	2109
	11th to 20th	Night	9% 8% 3 6% 4 4 3 4 6% 8% 46%	2200
	21st to end	Night	12% 5% 2 7% 4 3 3 3 4 6% 51%	2200
October	1st to 10th	Night	10% 5% 2 5% 3 2 2 2 4 6% 59%	2200
	11th to 20th	Night	12% 6% 2 5% 3 3 3 3 4 5% 54%	2291
	21st to end	Night	13% 8% 3 5% 3 3 3 2 4 6% 49%	2740
November	1st to 10th	Night	10% 6% 3 6% 3 3 3 3 4 6% 51%	2666
	11th to 20th	Night	11% 8% 3 6% 3 3 3 3 5% 7% 48%	2730
	21st to end	Night	14% 10% 4 6% 4 4 4 3 4 6% 42%	2730
December	1st to 10th	Night	16% 10% 3 8% 5% 5% 4 3 4 5% 37%	4380
	11th to 20th	Night	19% 12% 6% 9% 4 3 3 2 4 4 34%	4952
	21st to end	Night	15% 10% 6% 10% 5% 5% 5% 4 6% 7% 27%	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	51% 7% 7% 19% 15% 1	5259
	11th to 20th	Day	43% 5% 3 17% 29% 4	5280
	21st to end	Day	50% 5% 7% 21% 13% 4	5960
February	1st to 10th	Day	51% 6% 7% 16% 17% 3	2100
	11th to 20th	Day	54% 5% 6% 17% 14% 3	2058
	21st to end	Day	51% 5% 7% 14% 17% 5%	1730
March	1st to 10th	Day	51% 6% 6% 13% 15% 9%	4515
	11th to 20th	Day	39% 5% 6% 20% 19% 10%	4980
	21st to end	Day	43% 5% 9% 27% 15% 1	5465
April	1st to 10th	Day	41% 6% 11% 22% 16% 3	2362
	11th to 20th	Day	40% 6% 8% 19% 24% 3	2374
	21st to end	Day	43% 8% 11% 25% 13% 1	2555
May	1st to 10th	Day	51% 9% 11% 20% 8% 1	5897
	11th to 20th	Day	53% 10% 12% 20% 6%	5865
	21st to end	Day	45% 8% 9% 21% 13% 2	6447
June	1st to 10th	Day	41% 10% 15% 21% 12% 2	2600
	11th to 20th	Day	37% 9% 18% 21% 13% 2	2600
	21st to end	Day	36% 12% 17% 19% 13% 3	2600
July	1st to 10th	Day	36% 13% 17% 20% 12% 1	5835
	11th to 20th	Day	45% 14% 19% 16% 4 1	5831
	21st to end	Day	53% 12% 14% 16% 4 1	6240
August	1st to 10th	Day	34% 11% 17% 29% 9%	4221
	11th to 20th	Day	36% 11% 17% 23% 12% 1	3956
	21st to end	Day	32% 11% 13% 31% 11% 1	4311
September	1st to 10th	Day	42% 9% 12% 17% 16% 5%	2270
	11th to 20th	Day	41% 8% 11% 22% 16% 2	2200
	21st to end	Day	40% 7% 10% 21% 17% 5%	2200
October	1st to 10th	Day	24% 5% 7% 20% 32% 12%	3590
	11th to 20th	Day	24% 3 6% 24% 30% 13%	3412
	21st to end	Day	30% 6% 9% 23% 23% 10%	3358
November	1st to 10th	Day	32% 6% 8% 23% 26% 5%	1852
	11th to 20th	Day	39% 5% 6% 23% 22% 6%	1890
	21st to end	Day	42% 5% 7% 21% 20% 4	1890
December	1st to 10th	Day	43% 6% 4 20% 25% 2	3020
	11th to 20th	Day	55% 7% 6% 16% 13% 3	3460
	21st to end	Day	50% 6% 12% 18% 11% 2	4565
January	1st to 10th	Night	46% 6% 12% 20% 14% 2	7636
	11th to 20th	Night	43% 5% 4 16% 25% 6%	7680
	21st to end	Night	51% 4 7% 14% 17% 7%	8203
February	1st to 10th	Night	49% 6% 9% 19% 15% 3	2520
	11th to 20th	Night	55% 4 6% 18% 13% 5%	2459
	21st to end	Night	52% 6% 6% 16% 16% 4	2076
March	1st to 10th	Night	50% 7% 6% 15% 16% 5%	5381
	11th to 20th	Night	35% 6% 6% 21% 17% 14%	4980
	21st to end	Night	46% 6% 8% 25% 13% 2	5467
April	1st to 10th	Night	37% 7% 10% 23% 20% 3	2054
	11th to 20th	Night	37% 5% 8% 21% 23% 5%	1975
	21st to end	Night	37% 8% 12% 29% 14% 1	1845
May	1st to 10th	Night	48% 9% 14% 20% 7% 1	4060
	11th to 20th	Night	53% 9% 13% 16% 9%	4033
	21st to end	Night	43% 10% 12% 23% 12% 1	4429
June	1st to 10th	Night	36% 9% 15% 26% 12% 2	1800
	11th to 20th	Night	26% 8% 22% 28% 14% 2	1800
	21st to end	Night	33% 10% 16% 25% 13% 4	1800
July	1st to 10th	Night	33% 10% 21% 23% 12% 1	4015
	11th to 20th	Night	34% 11% 26% 22% 5% 2	4006
	21st to end	Night	45% 12% 21% 17% 4 1	4297
August	1st to 10th	Night	26% 9% 15% 36% 12% 1	2904
	11th to 20th	Night	29% 10% 23% 25% 13% 1	3155
	21st to end	Night	24% 7% 14% 40% 15% 1	3586
September	1st to 10th	Night	36% 9% 13% 21% 16% 5%	2109
	11th to 20th	Night	36% 7% 13% 22% 21% 1	2200
	21st to end	Night	34% 6% 11% 22% 21% 5%	2200
October	1st to 10th	Night	21% 5% 6% 26% 29% 14%	3590
	11th to 20th	Night	21% 4 6% 24% 28% 17%	3725
	21st to end	Night	25% 4 7% 25% 26% 12%	4414
November	1st to 10th	Night	35% 4 8% 23% 23% 7%	2666
	11th to 20th	Night	37% 4 7% 21% 25% 7%	2730
	21st to end	Night	44% 5% 5% 22% 20% 4	2730
December	1st to 10th	Night	48% 6% 6% 16% 23% 2	4380
	11th to 20th	Night	52% 6% 5% 18% 17% 2	4954
	21st to end	Night	51% 9% 11% 18% 10% 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	30% 25% 33% 11% 1 1	330
	11th to 20th	Day	31% 29% 26% 10% 3	330
	21st to end	Day	26% 29% 35% 8% 1	363
February	1st to 10th	Day	24% 31% 33% 11% 1	330
	11th to 20th	Day	39% 28% 28% 3 1 1	330
	21st to end	Day	38% 23% 32% 5% 1	273
March	1st to 10th	Day	30% 24% 33% 12% 1	308
	11th to 20th	Day	27% 24% 29% 16% 4 1	500
	21st to end	Day	25% 21% 34% 16% 5%	550
April	1st to 10th	Day	23% 22% 27% 19% 8% 1	500
	11th to 20th	Day	21% 17% 33% 18% 9% 1	492
	21st to end	Day	19% 15% 34% 21% 10% 2	500
May	1st to 10th	Day	21% 18% 31% 19% 9% 3	503
	11th to 20th	Day	14% 12% 29% 26% 14% 6%	527
	21st to end	Day	17% 10% 22% 25% 16% 10%	573
June	1st to 10th	Day	13% 9% 23% 28% 18% 10%	530
	11th to 20th	Day	7% 5% 19% 32% 25% 13%	530
	21st to end	Day	6% 4 23% 30% 23% 14%	530
July	1st to 10th	Day	10% 3 16% 28% 25% 18%	525
	11th to 20th	Day	10% 3 15% 24% 29% 18%	524
	21st to end	Day	12% 4 13% 26% 28% 18%	576
August	1st to 10th	Day	13% 5% 17% 27% 24% 15%	526
	11th to 20th	Day	10% 5% 18% 30% 26% 11%	519
	21st to end	Day	11% 4 12% 26% 30% 16%	583
September	1st to 10th	Day	12% 4 15% 29% 29% 12%	530
	11th to 20th	Day	13% 5% 11% 29% 30% 12%	530
	21st to end	Day	19% 5% 20% 26% 25% 6%	530
October	1st to 10th	Day	12% 8% 24% 28% 21% 7%	530
	11th to 20th	Day	12% 14% 28% 29% 15% 2	530
	21st to end	Day	21% 14% 29% 24% 11% 2	478
November	1st to 10th	Day	17% 15% 34% 25% 7% 2	330
	11th to 20th	Day	17% 17% 44% 19% 2	330
	21st to end	Day	22% 22% 35% 14% 6% 1	330
December	1st to 10th	Day	27% 23% 35% 11% 4 1	330
	11th to 20th	Day	25% 21% 35% 15% 4	330
	21st to end	Day	29% 23% 32% 12% 3	363
January	1st to 10th	Night	22% 23% 32% 19% 4	840
	11th to 20th	Night	25% 23% 29% 19% 3	840
	21st to end	Night	21% 20% 39% 19% 2	924
February	1st to 10th	Night	21% 19% 35% 23% 3	840
	11th to 20th	Night	29% 21% 33% 16% 1	823
	21st to end	Night	28% 20% 33% 17% 2	692
March	1st to 10th	Night	20% 19% 33% 25% 3	809
	11th to 20th	Night	19% 20% 32% 22% 6% 1	800
	21st to end	Night	21% 17% 29% 25% 8%	880
April	1st to 10th	Night	17% 15% 33% 26% 9% 1	654
	11th to 20th	Night	16% 13% 33% 28% 10% 1	593
	21st to end	Night	14% 9% 32% 35% 9% 1	600
May	1st to 10th	Night	12% 11% 30% 30% 14% 2	600
	11th to 20th	Night	14% 7% 24% 31% 19% 5%	591
	21st to end	Night	10% 6% 16% 35% 29% 4	650
June	1st to 10th	Night	8% 4 15% 38% 29% 5%	600
	11th to 20th	Night	5% 3 15% 34% 36% 8%	600
	21st to end	Night	6% 2 13% 37% 33% 10%	600
July	1st to 10th	Night	10% 2 8% 29% 42% 9%	585
	11th to 20th	Night	9% 3 9% 27% 41% 12%	582
	21st to end	Night	9% 2 7% 31% 41% 9%	657
August	1st to 10th	Night	8% 2 10% 30% 41% 9%	597
	11th to 20th	Night	9% 3 12% 33% 38% 6%	594
	21st to end	Night	10% 1 8% 33% 37% 10%	660
September	1st to 10th	Night	11% 4 14% 29% 35% 7%	709
	11th to 20th	Night	13% 3 14% 30% 34% 7%	800
	21st to end	Night	15% 4 18% 31% 29% 4	800
October	1st to 10th	Night	11% 6% 22% 27% 27% 8%	800
	11th to 20th	Night	16% 8% 25% 33% 16% 2	800
	21st to end	Night	18% 10% 27% 31% 14% 2	880
November	1st to 10th	Night	14% 11% 24% 33% 16% 2	820
	11th to 20th	Night	14% 18% 31% 26% 10% 1	840
	21st to end	Night	19% 17% 27% 26% 10%	840
December	1st to 10th	Night	25% 18% 27% 24% 6%	840
	11th to 20th	Night	22% 16% 31% 25% 6% 1	840
	21st to end	Night	27% 18% 27% 23% 4	924

Page generated at 2026-02-28 00:40:20. Version ac07

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