Great Smokey Mountains National Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Great Smokey Mountains National Park clear sky chart from 2005-11-06 to 2026-08-15.

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% 9% 4 9% 6% 5% 5% 4 6% 7% 32%	143325
	Night	12% 11% 4 9% 6% 5% 5% 4 5% 6% 34%	138572
Transparency	Day	29% 38% 9% 12% 8% 3	147075
	Night	28% 38% 10% 12% 9% 4	142894
Seeing	Day	19% 17% 26% 21% 12% 5%	17266
	Night	18% 14% 24% 26% 16% 3	27268

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	13% 11% 6% 7% 4 4 4 4 5% 5% 37%	5258
	11th to 20th	Day	8% 10% 4 11% 4 3 3 2 4 5% 46%	5280
	21st to end	Day	12% 13% 6% 11% 3 3 3 3 5% 5% 34%	5780
February	1st to 10th	Day	14% 11% 5% 10% 5% 4 5% 4 4 5% 32%	2059
	11th to 20th	Day	19% 12% 5% 9% 5% 4 3 3 4 6% 30%	2048
	21st to end	Day	17% 11% 4 10% 4 4 4 3 5% 5% 33%	1730
March	1st to 10th	Day	16% 11% 4 8% 5% 5% 4 4 5% 6% 33%	4803
	11th to 20th	Day	11% 9% 3 7% 4 4 3 3 5% 6% 44%	5090
	21st to end	Day	14% 11% 3 7% 5% 4 4 3 4 5% 39%	5586
April	1st to 10th	Day	11% 11% 3 6% 6% 5% 4 5% 6% 6% 37%	2327
	11th to 20th	Day	13% 9% 3 6% 5% 4 4 4 5% 6% 40%	2536
	21st to end	Day	15% 9% 3 7% 6% 4 5% 4 5% 6% 36%	2730
May	1st to 10th	Day	15% 10% 4 9% 6% 6% 6% 4 6% 7% 28%	7616
	11th to 20th	Day	13% 10% 4 11% 6% 6% 6% 4 6% 7% 29%	7626
	21st to end	Day	15% 11% 5% 12% 7% 6% 5% 4 5% 7% 22%	8391
June	1st to 10th	Day	11% 8% 3 9% 7% 7% 6% 5% 7% 9% 28%	2730
	11th to 20th	Day	7% 7% 3 10% 8% 7% 7% 5% 8% 9% 28%	2730
	21st to end	Day	11% 7% 3 8% 7% 5% 7% 6% 8% 9% 29%	2730
July	1st to 10th	Day	7% 6% 3 9% 7% 8% 9% 7% 9% 9% 25%	7680
	11th to 20th	Day	12% 9% 4 12% 9% 9% 8% 6% 8% 7% 17%	7680
	21st to end	Day	14% 10% 4 12% 8% 8% 7% 6% 6% 8% 16%	8340
August	1st to 10th	Day	11% 7% 3 9% 7% 7% 7% 6% 8% 9% 24%	4364
	11th to 20th	Day	10% 7% 3 9% 7% 7% 7% 5% 8% 10% 28%	4198
	21st to end	Day	9% 6% 3 9% 6% 6% 7% 6% 8% 10% 30%	4284
September	1st to 10th	Day	13% 8% 4 10% 6% 5% 6% 5% 6% 7% 32%	2200
	11th to 20th	Day	15% 8% 3 8% 6% 5% 5% 4 7% 7% 32%	2200
	21st to end	Day	14% 8% 3 7% 6% 6% 5% 4 6% 6% 36%	2200
October	1st to 10th	Day	11% 7% 2 7% 5% 4 5% 4 5% 6% 45%	2200
	11th to 20th	Day	11% 9% 2 5% 3 3 3 3 4 6% 51%	2024
	21st to end	Day	13% 8% 2 5% 4 4 4 2 4 6% 48%	2200
November	1st to 10th	Day	10% 8% 2 6% 3 3 3 3 5% 5% 51%	1877
	11th to 20th	Day	10% 8% 3 7% 5% 4 4 4 6% 6% 45%	1890
	21st to end	Day	12% 10% 3 7% 4 4 4 3 6% 5% 41%	1890
December	1st to 10th	Day	11% 10% 3 8% 5% 4 4 3 5% 5% 40%	3020
	11th to 20th	Day	12% 11% 5% 12% 7% 5% 4 3 5% 5% 31%	3463
	21st to end	Day	9% 10% 6% 10% 6% 5% 5% 4 5% 7% 34%	4565
January	1st to 10th	Night	11% 13% 4 9% 5% 4 4 3 5% 6% 34%	7635
	11th to 20th	Night	12% 10% 4 10% 5% 4 3 3 4 5% 40%	7680
	21st to end	Night	12% 16% 5% 10% 5% 4 4 3 4 4 34%	8401
February	1st to 10th	Night	13% 12% 4 10% 5% 4 4 4 5% 5% 33%	2557
	11th to 20th	Night	18% 14% 4 10% 5% 4 4 4 4 3 30%	2458
	21st to end	Night	18% 13% 4 9% 6% 4 5% 4 4 4 30%	2076
March	1st to 10th	Night	14% 14% 6% 10% 5% 4 4 4 4 6% 29%	5269
	11th to 20th	Night	10% 9% 3 7% 5% 4 4 4 5% 6% 44%	5090
	21st to end	Night	11% 9% 4 8% 7% 5% 4 3 5% 6% 39%	5588
April	1st to 10th	Night	13% 11% 3 6% 5% 4 4 3 5% 7% 39%	2310
	11th to 20th	Night	12% 11% 3 7% 4 4 3 3 5% 6% 43%	2030
	21st to end	Night	14% 9% 3 7% 5% 4 5% 3 5% 7% 39%	1890
May	1st to 10th	Night	14% 12% 4 9% 6% 5% 6% 5% 6% 7% 26%	5237
	11th to 20th	Night	15% 10% 4 10% 6% 4 5% 4 5% 7% 31%	5234
	21st to end	Night	15% 12% 5% 12% 7% 6% 5% 4 5% 7% 24%	5761
June	1st to 10th	Night	9% 8% 3 8% 6% 6% 6% 5% 8% 9% 33%	1890
	11th to 20th	Night	7% 5% 2 6% 6% 6% 6% 5% 9% 11% 37%	1890
	21st to end	Night	9% 7% 2 8% 6% 5% 6% 5% 7% 9% 36%	1890
July	1st to 10th	Night	7% 7% 3 9% 7% 6% 6% 5% 8% 10% 31%	5278
	11th to 20th	Night	11% 8% 4 10% 6% 7% 7% 5% 7% 9% 26%	5277
	21st to end	Night	11% 11% 4 11% 8% 7% 7% 5% 7% 9% 20%	5736
August	1st to 10th	Night	10% 7% 3 8% 6% 5% 6% 6% 7% 10% 32%	3005
	11th to 20th	Night	13% 8% 3 7% 5% 6% 6% 6% 7% 8% 32%	2934
	21st to end	Night	7% 5% 2 7% 5% 5% 6% 6% 7% 9% 41%	3586
September	1st to 10th	Night	12% 8% 3 7% 5% 5% 5% 4 7% 7% 37%	2194
	11th to 20th	Night	13% 8% 3 8% 5% 5% 5% 3 6% 7% 38%	2200
	21st to end	Night	13% 8% 3 7% 6% 4 4 3 5% 6% 42%	2200
October	1st to 10th	Night	13% 9% 2 5% 4 3 4 3 4 6% 48%	2200
	11th to 20th	Night	14% 8% 2 6% 4 4 4 3 4 4 49%	2375
	21st to end	Night	11% 10% 3 5% 4 4 4 3 4 5% 47%	2640
November	1st to 10th	Night	11% 9% 3 6% 4 4 3 3 5% 5% 47%	2636
	11th to 20th	Night	12% 10% 3 7% 4 3 4 3 5% 5% 44%	2730
	21st to end	Night	12% 11% 3 8% 5% 3 4 3 4 6% 40%	2730
December	1st to 10th	Night	11% 12% 6% 11% 6% 4 4 3 4 4 35%	4380
	11th to 20th	Night	14% 12% 4 12% 6% 5% 4 3 4 5% 30%	4952
	21st to end	Night	10% 12% 6% 12% 6% 5% 4 4 6% 6% 29%	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	34% 24% 11% 14% 16% 2	5259
	11th to 20th	Day	30% 22% 5% 10% 23% 10%	5280
	21st to end	Day	39% 26% 5% 14% 12% 5%	5780
February	1st to 10th	Day	22% 59% 4 8% 6% 1	2059
	11th to 20th	Day	24% 58% 2 7% 6% 1	2058
	21st to end	Day	22% 59% 2 5% 8% 3	1730
March	1st to 10th	Day	35% 30% 8% 8% 10% 8%	4803
	11th to 20th	Day	23% 29% 5% 14% 14% 14%	5090
	21st to end	Day	28% 32% 6% 23% 8% 3	5586
April	1st to 10th	Day	19% 60% 5% 9% 6%	2327
	11th to 20th	Day	19% 60% 4 10% 6% 1	2536
	21st to end	Day	18% 60% 5% 11% 6% 1	2730
May	1st to 10th	Day	37% 30% 10% 16% 7%	7651
	11th to 20th	Day	35% 30% 11% 18% 6%	7630
	21st to end	Day	44% 30% 9% 9% 7% 1	8405
June	1st to 10th	Day	20% 62% 5% 8% 4	2730
	11th to 20th	Day	20% 62% 8% 7% 3	2730
	21st to end	Day	19% 62% 9% 7% 3	2730
July	1st to 10th	Day	29% 35% 18% 14% 4	7615
	11th to 20th	Day	41% 34% 16% 9% 1	7611
	21st to end	Day	46% 29% 12% 8% 4	8156
August	1st to 10th	Day	29% 43% 12% 14% 3	4351
	11th to 20th	Day	23% 42% 19% 8% 6%	4237
	21st to end	Day	19% 42% 12% 23% 4 1	4284
September	1st to 10th	Day	18% 60% 5% 8% 9% 1	2200
	11th to 20th	Day	18% 60% 6% 11% 6%	2200
	21st to end	Day	18% 60% 8% 9% 4	2200
October	1st to 10th	Day	17% 38% 4 11% 20% 10%	3590
	11th to 20th	Day	13% 36% 3 12% 17% 18%	3277
	21st to end	Day	13% 38% 4 21% 14% 9%	3538
November	1st to 10th	Day	19% 53% 5% 10% 10% 2	1877
	11th to 20th	Day	17% 55% 3 10% 12% 3	1890
	21st to end	Day	19% 56% 4 10% 9% 2	1890
December	1st to 10th	Day	24% 38% 8% 11% 15% 5%	3020
	11th to 20th	Day	34% 35% 8% 9% 10% 3	3460
	21st to end	Day	30% 30% 11% 18% 9% 2	4565
January	1st to 10th	Night	35% 26% 11% 15% 10% 3	7636
	11th to 20th	Night	34% 23% 5% 10% 19% 10%	7680
	21st to end	Night	39% 25% 6% 9% 14% 8%	8401
February	1st to 10th	Night	22% 59% 3 8% 7% 1	2557
	11th to 20th	Night	26% 59% 3 6% 6% 1	2459
	21st to end	Night	22% 59% 4 6% 6% 3	2076
March	1st to 10th	Night	36% 33% 8% 10% 9% 4	5269
	11th to 20th	Night	19% 31% 7% 16% 13% 14%	5090
	21st to end	Night	28% 31% 12% 17% 9% 3	5588
April	1st to 10th	Night	19% 60% 6% 9% 5% 1	2310
	11th to 20th	Night	18% 60% 5% 10% 6% 2	2030
	21st to end	Night	17% 61% 5% 12% 5%	1890
May	1st to 10th	Night	36% 31% 11% 16% 5%	5264
	11th to 20th	Night	35% 29% 14% 16% 6%	5235
	21st to end	Night	41% 32% 12% 11% 4	5771
June	1st to 10th	Night	17% 62% 8% 8% 4	1890
	11th to 20th	Night	14% 64% 10% 9% 3	1890
	21st to end	Night	16% 61% 9% 10% 4	1890
July	1st to 10th	Night	26% 33% 23% 15% 3	5235
	11th to 20th	Night	34% 33% 21% 10% 1	5226
	21st to end	Night	41% 31% 15% 8% 4 1	5606
August	1st to 10th	Night	26% 41% 15% 15% 3	2994
	11th to 20th	Night	23% 41% 23% 9% 4	2961
	21st to end	Night	14% 41% 17% 22% 6%	3586
September	1st to 10th	Night	15% 61% 6% 10% 7% 1	2194
	11th to 20th	Night	16% 61% 6% 11% 5%	2200
	21st to end	Night	17% 60% 8% 10% 6%	2200
October	1st to 10th	Night	17% 38% 6% 15% 14% 11%	3590
	11th to 20th	Night	15% 36% 4 11% 14% 20%	3861
	21st to end	Night	12% 36% 4 19% 16% 13%	4252
November	1st to 10th	Night	22% 54% 4 11% 8% 1	2636
	11th to 20th	Night	18% 55% 4 9% 10% 4	2730
	21st to end	Night	21% 55% 3 10% 10% 1	2730
December	1st to 10th	Night	32% 37% 5% 8% 15% 4	4380
	11th to 20th	Night	34% 35% 7% 10% 11% 2	4954
	21st to end	Night	34% 30% 11% 13% 11% 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	27% 34% 30% 8% 1	330
	11th to 20th	Day	37% 28% 22% 11% 1	330
	21st to end	Day	27% 36% 28% 8% 1	363
February	1st to 10th	Day	24% 33% 33% 8% 2	330
	11th to 20th	Day	40% 36% 19% 4 1	330
	21st to end	Day	40% 33% 21% 6%	273
March	1st to 10th	Day	28% 27% 30% 12% 3	423
	11th to 20th	Day	29% 27% 31% 10% 3 1	540
	21st to end	Day	25% 24% 32% 14% 4	594
April	1st to 10th	Day	23% 25% 26% 18% 6% 1	540
	11th to 20th	Day	22% 25% 27% 17% 8% 1	532
	21st to end	Day	24% 18% 28% 20% 8% 2	540
May	1st to 10th	Day	23% 22% 31% 14% 6% 3	543
	11th to 20th	Day	15% 16% 29% 25% 9% 6%	567
	21st to end	Day	18% 13% 25% 24% 11% 9%	617
June	1st to 10th	Day	11% 12% 27% 27% 16% 6%	570
	11th to 20th	Day	7% 11% 26% 27% 21% 9%	570
	21st to end	Day	13% 7% 27% 29% 14% 10%	570
July	1st to 10th	Day	11% 6% 22% 26% 24% 12%	565
	11th to 20th	Day	12% 5% 20% 29% 19% 15%	564
	21st to end	Day	12% 8% 19% 27% 22% 11%	620
August	1st to 10th	Day	16% 10% 20% 24% 19% 11%	566
	11th to 20th	Day	10% 10% 19% 31% 22% 9%	535
	21st to end	Day	14% 4 16% 26% 29% 11%	583
September	1st to 10th	Day	10% 6% 23% 25% 27% 9%	530
	11th to 20th	Day	16% 7% 18% 28% 23% 8%	530
	21st to end	Day	15% 10% 19% 32% 18% 4	530
October	1st to 10th	Day	16% 9% 26% 27% 16% 6%	530
	11th to 20th	Day	16% 14% 31% 26% 11% 2	530
	21st to end	Day	21% 14% 29% 25% 9% 2	583
November	1st to 10th	Day	18% 21% 32% 21% 8% 1	355
	11th to 20th	Day	19% 28% 32% 17% 3	330
	21st to end	Day	21% 26% 32% 17% 4	330
December	1st to 10th	Day	29% 28% 30% 12% 1	330
	11th to 20th	Day	23% 25% 32% 17% 3	330
	21st to end	Day	25% 25% 36% 11% 3	363
January	1st to 10th	Night	23% 24% 28% 21% 4	840
	11th to 20th	Night	26% 26% 28% 16% 4	840
	21st to end	Night	21% 24% 33% 20% 2	924
February	1st to 10th	Night	22% 19% 32% 25% 2	840
	11th to 20th	Night	28% 25% 32% 14% 1	823
	21st to end	Night	28% 26% 29% 16% 1	692
March	1st to 10th	Night	22% 21% 31% 22% 4	840
	11th to 20th	Night	24% 21% 28% 20% 6%	840
	21st to end	Night	21% 21% 31% 20% 7%	924
April	1st to 10th	Night	20% 21% 30% 20% 8% 1	840
	11th to 20th	Night	20% 15% 31% 23% 11% 1	623
	21st to end	Night	17% 13% 31% 29% 9% 1	630
May	1st to 10th	Night	18% 14% 28% 26% 11% 2	630
	11th to 20th	Night	16% 10% 25% 31% 17% 2	621
	21st to end	Night	14% 5% 19% 32% 26% 4	683
June	1st to 10th	Night	9% 6% 19% 37% 25% 4	630
	11th to 20th	Night	6% 4 20% 35% 27% 9%	630
	21st to end	Night	9% 4 17% 34% 29% 6%	630
July	1st to 10th	Night	11% 2 12% 31% 39% 5%	615
	11th to 20th	Night	11% 3 10% 32% 35% 10%	612
	21st to end	Night	9% 4 13% 29% 37% 8%	690
August	1st to 10th	Night	10% 5% 10% 34% 35% 7%	627
	11th to 20th	Night	11% 4 12% 34% 34% 5%	606
	21st to end	Night	12% 3 10% 32% 35% 8%	660
September	1st to 10th	Night	12% 5% 11% 30% 35% 6%	794
	11th to 20th	Night	15% 4 13% 33% 29% 7%	800
	21st to end	Night	16% 6% 18% 32% 26% 2	800
October	1st to 10th	Night	17% 6% 20% 24% 27% 7%	800
	11th to 20th	Night	17% 10% 25% 31% 15% 2	800
	21st to end	Night	18% 13% 25% 29% 13% 2	880
November	1st to 10th	Night	18% 11% 22% 32% 15% 3	820
	11th to 20th	Night	18% 17% 27% 27% 10% 2	840
	21st to end	Night	20% 17% 26% 26% 11% 1	840
December	1st to 10th	Night	21% 23% 28% 22% 6%	840
	11th to 20th	Night	20% 20% 30% 24% 6% 1	840
	21st to end	Night	22% 20% 31% 24% 4	924

Page generated at 2026-08-12 03:37:15. Version ac07

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