Tryon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tryon 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	8% 6% 2 5% 3 3 4 3 5% 7% 53%	152320
	Night	7% 6% 2 6% 4 4 4 4 5% 7% 50%	147340
Transparency	Day	30% 5% 12% 28% 20% 5%	147159
	Night	32% 5% 12% 27% 20% 4	143514
Seeing	Day	11% 8% 31% 32% 16% 3	18350
	Night	10% 8% 37% 36% 9%	28174

By Month

Percentage Cloud Cover SW (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	6% 10% 4 7% 4 3 3 2 4 5% 50%	4720
	11th to 20th	Day	4 8% 3 7% 4 4 5% 4 6% 6% 49%	4740
	21st to end	Day	4 6% 3 8% 5% 5% 4 4 6% 7% 47%	5223
February	1st to 10th	Day	6% 9% 4 8% 5% 5% 4 3 5% 7% 42%	2027
	11th to 20th	Day	6% 9% 3 7% 5% 4 4 4 4 7% 47%	2049
	21st to end	Day	7% 6% 3 5% 3 2 3 2 6% 6% 57%	1730
March	1st to 10th	Day	9% 7% 2 5% 3 2 3 3 4 5% 56%	4600
	11th to 20th	Day	6% 6% 1 5% 3 3 4 3 4 7% 58%	4942
	21st to end	Day	11% 8% 3 6% 4 4 3 3 6% 8% 45%	5772
April	1st to 10th	Day	11% 7% 2 4 3 4 3 4 5% 7% 51%	2520
	11th to 20th	Day	12% 8% 3 6% 4 4 4 3 5% 7% 45%	2512
	21st to end	Day	15% 6% 2 5% 4 3 4 4 5% 6% 47%	2730
May	1st to 10th	Day	9% 5% 2 5% 3 4 4 4 6% 7% 51%	7655
	11th to 20th	Day	11% 5% 2 5% 3 3 4 3 5% 7% 53%	7627
	21st to end	Day	16% 6% 2 6% 4 4 4 3 5% 6% 44%	8857
June	1st to 10th	Day	7% 4 1 4 3 3 4 3 7% 9% 55%	2940
	11th to 20th	Day	8% 5% 2 4 4 3 4 4 6% 7% 54%	2940
	21st to end	Day	6% 3 1 4 3 3 3 4 6% 8% 59%	2940
July	1st to 10th	Day	6% 3 2 5% 4 3 4 4 5% 8% 55%	8249
	11th to 20th	Day	5% 3 1 4 3 3 4 3 5% 8% 61%	8250
	21st to end	Day	6% 5% 2 6% 4 4 5% 4 7% 9% 49%	8906
August	1st to 10th	Day	10% 5% 2 5% 4 3 4 4 6% 8% 50%	5931
	11th to 20th	Day	8% 4 2 5% 3 4 4 4 6% 8% 52%	5866
	21st to end	Day	9% 6% 2 7% 4 4 4 3 5% 7% 49%	6093
September	1st to 10th	Day	7% 4 1 4 3 3 3 3 6% 7% 60%	2390
	11th to 20th	Day	8% 4 1 4 3 3 3 4 6% 6% 58%	2200
	21st to end	Day	8% 5% 1 4 2 2 2 2 4 5% 64%	2200
October	1st to 10th	Day	7% 4 1 2 2 1 1 2 2 4 74%	3590
	11th to 20th	Day	8% 4 1 4 2 3 4 2 5% 6% 62%	3219
	21st to end	Day	8% 6% 2 5% 4 4 3 3 5% 6% 55%	3190
November	1st to 10th	Day	5% 6% 1 4 3 3 4 3 7% 7% 57%	1853
	11th to 20th	Day	4 5% 2 5% 4 3 3 3 5% 6% 60%	1890
	21st to end	Day	7% 7% 2 4 2 3 3 4 5% 6% 57%	1890
December	1st to 10th	Day	3 5% 2 4 4 4 3 3 5% 7% 60%	2881
	11th to 20th	Day	4 5% 2 6% 4 3 3 3 5% 7% 58%	3106
	21st to end	Day	8% 9% 3 7% 4 4 4 3 5% 7% 44%	4092
January	1st to 10th	Night	5% 10% 3 11% 6% 4 5% 3 5% 6% 42%	8201
	11th to 20th	Night	2 6% 3 7% 5% 5% 5% 4 5% 7% 51%	8250
	21st to end	Night	3 7% 4 8% 6% 5% 5% 3 4 6% 50%	8990
February	1st to 10th	Night	7% 10% 3 8% 5% 3 4 4 5% 7% 43%	2613
	11th to 20th	Night	4 9% 3 8% 6% 5% 4 4 6% 8% 45%	2458
	21st to end	Night	4 7% 2 6% 4 4 4 3 5% 6% 54%	2076
March	1st to 10th	Night	8% 6% 2 5% 3 3 3 2 5% 5% 55%	5494
	11th to 20th	Night	7% 7% 2 4 3 3 4 3 4 6% 57%	5242
	21st to end	Night	8% 8% 3 8% 5% 5% 5% 4 6% 8% 39%	5392
April	1st to 10th	Night	11% 8% 2 5% 4 3 4 4 6% 7% 46%	2100
	11th to 20th	Night	12% 8% 2 4 4 4 3 4 5% 7% 48%	2056
	21st to end	Night	14% 7% 2 6% 4 3 4 4 5% 7% 44%	1890
May	1st to 10th	Night	12% 6% 2 6% 4 3 4 3 5% 6% 48%	5292
	11th to 20th	Night	9% 5% 2 5% 4 4 4 4 6% 7% 51%	5265
	21st to end	Night	17% 7% 3 6% 4 4 4 3 5% 6% 42%	5334
June	1st to 10th	Night	7% 5% 2 4 4 3 5% 4 6% 9% 50%	1680
	11th to 20th	Night	9% 6% 2 5% 3 4 4 5% 7% 9% 47%	1680
	21st to end	Night	5% 4 2 6% 5% 5% 5% 5% 7% 10% 47%	1680
July	1st to 10th	Night	7% 5% 2 6% 5% 4 4 4 7% 8% 49%	4740
	11th to 20th	Night	7% 4 2 4 3 3 4 3 6% 8% 57%	4740
	21st to end	Night	7% 5% 2 6% 5% 4 6% 5% 8% 10% 44%	5200
August	1st to 10th	Night	8% 6% 3 8% 5% 5% 6% 4 8% 10% 38%	4101
	11th to 20th	Night	8% 4 2 6% 4 5% 5% 5% 7% 10% 46%	4199
	21st to end	Night	8% 8% 2 7% 4 4 5% 4 7% 8% 43%	5083
September	1st to 10th	Night	8% 4 1 4 3 3 3 3 5% 6% 60%	2010
	11th to 20th	Night	7% 4 1 4 3 4 3 3 5% 7% 58%	2200
	21st to end	Night	9% 3 2 4 3 3 3 3 4 6% 61%	2200
October	1st to 10th	Night	7% 2 1 2 2 2 1 2 2 3 75%	3590
	11th to 20th	Night	9% 3 1 3 2 2 3 2 4 6% 65%	3888
	21st to end	Night	7% 6% 2 5% 4 3 4 3 5% 6% 56%	4610
November	1st to 10th	Night	5% 5% 2 4 4 4 4 4 5% 7% 57%	2665
	11th to 20th	Night	4 4 1 4 4 4 5% 4 6% 7% 56%	2730
	21st to end	Night	7% 6% 1 5% 4 3 4 3 4 8% 55%	2730
December	1st to 10th	Night	3 4 2 4 3 3 3 3 5% 7% 63%	4512
	11th to 20th	Night	3 6% 2 5% 4 4 4 4 5% 8% 55%	5321
	21st to end	Night	9% 10% 3 6% 4 4 4 3 5% 6% 45%	7128

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	37% 3 10% 30% 19% 1	4723
	11th to 20th	Day	33% 6% 11% 26% 19% 4	4740
	21st to end	Day	35% 5% 13% 25% 19% 3	5223
February	1st to 10th	Day	41% 5% 14% 22% 14% 4	2027
	11th to 20th	Day	37% 5% 11% 24% 19% 4	2059
	21st to end	Day	28% 3 12% 33% 19% 5%	1730
March	1st to 10th	Day	30% 4 7% 25% 29% 5%	4600
	11th to 20th	Day	27% 4 11% 27% 30% 2	4942
	21st to end	Day	36% 6% 19% 24% 12% 2	5772
April	1st to 10th	Day	33% 4 16% 28% 15% 3	2520
	11th to 20th	Day	38% 6% 12% 22% 18% 3	2515
	21st to end	Day	37% 6% 13% 27% 17% 1	2730
May	1st to 10th	Day	29% 6% 12% 29% 20% 4	7655
	11th to 20th	Day	31% 6% 11% 29% 20% 4	7631
	21st to end	Day	39% 6% 13% 25% 14% 3	8858
June	1st to 10th	Day	25% 7% 20% 32% 13% 3	2940
	11th to 20th	Day	28% 6% 14% 27% 19% 6%	2940
	21st to end	Day	21% 6% 13% 31% 22% 6%	2940
July	1st to 10th	Day	26% 5% 11% 29% 26% 3	8181
	11th to 20th	Day	22% 5% 10% 29% 22% 11%	8175
	21st to end	Day	29% 7% 17% 22% 19% 6%	8708
August	1st to 10th	Day	31% 7% 14% 27% 18% 3	4350
	11th to 20th	Day	35% 7% 14% 23% 18% 2	4281
	21st to end	Day	23% 5% 16% 22% 22% 11%	4420
September	1st to 10th	Day	23% 5% 11% 28% 23% 10%	2390
	11th to 20th	Day	24% 5% 12% 29% 25% 5%	2200
	21st to end	Day	24% 3 8% 30% 29% 6%	2200
October	1st to 10th	Day	17% 2 6% 22% 35% 18%	3590
	11th to 20th	Day	25% 4 11% 35% 21% 4	3219
	21st to end	Day	30% 4 8% 34% 18% 6%	3190
November	1st to 10th	Day	25% 6% 15% 29% 21% 6%	1853
	11th to 20th	Day	25% 4 11% 29% 26% 6%	1890
	21st to end	Day	28% 4 13% 30% 21% 5%	1890
December	1st to 10th	Day	24% 4 12% 34% 23% 3	2881
	11th to 20th	Day	26% 3 17% 34% 17% 3	3104
	21st to end	Day	39% 5% 9% 33% 13% 2	4092
January	1st to 10th	Night	42% 4 11% 25% 16% 2	8202
	11th to 20th	Night	31% 5% 14% 27% 21% 2	8250
	21st to end	Night	36% 4 10% 26% 20% 4	8990
February	1st to 10th	Night	39% 6% 12% 24% 15% 3	2613
	11th to 20th	Night	37% 5% 13% 28% 14% 4	2458
	21st to end	Night	29% 5% 12% 27% 21% 6%	2076
March	1st to 10th	Night	30% 4 8% 25% 28% 5%	5494
	11th to 20th	Night	30% 3 8% 25% 29% 5%	5242
	21st to end	Night	40% 9% 16% 23% 11% 1	5392
April	1st to 10th	Night	36% 6% 14% 25% 16% 3	2100
	11th to 20th	Night	36% 6% 12% 25% 18% 3	2056
	21st to end	Night	38% 7% 14% 25% 13% 2	1890
May	1st to 10th	Night	36% 6% 11% 27% 19% 2	5293
	11th to 20th	Night	30% 7% 13% 28% 20% 3	5266
	21st to end	Night	43% 6% 13% 25% 12% 1	5336
June	1st to 10th	Night	27% 9% 22% 26% 13% 2	1680
	11th to 20th	Night	32% 7% 18% 25% 14% 5%	1680
	21st to end	Night	29% 8% 16% 26% 18% 2	1680
July	1st to 10th	Night	32% 6% 16% 29% 16% 1	4700
	11th to 20th	Night	25% 5% 14% 25% 21% 10%	4692
	21st to end	Night	33% 8% 16% 23% 16% 4	5086
August	1st to 10th	Night	35% 7% 17% 25% 14% 2	3006
	11th to 20th	Night	36% 7% 14% 25% 15% 3	3060
	21st to end	Night	27% 6% 15% 24% 18% 10%	3687
September	1st to 10th	Night	25% 4 11% 25% 27% 8%	2010
	11th to 20th	Night	25% 6% 13% 28% 22% 7%	2200
	21st to end	Night	25% 4 8% 28% 28% 6%	2200
October	1st to 10th	Night	17% 3 5% 20% 46% 9%	3590
	11th to 20th	Night	23% 4 9% 31% 26% 7%	3888
	21st to end	Night	29% 4 12% 26% 24% 6%	4610
November	1st to 10th	Night	25% 5% 12% 29% 23% 7%	2665
	11th to 20th	Night	25% 5% 13% 28% 24% 6%	2730
	21st to end	Night	28% 5% 11% 30% 22% 4	2730
December	1st to 10th	Night	23% 3 16% 35% 21% 4	4512
	11th to 20th	Night	28% 4 14% 35% 17% 2	5322
	21st to end	Night	39% 5% 10% 30% 15% 1	7128

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	11% 6% 42% 27% 12% 2	330
	11th to 20th	Day	10% 15% 36% 31% 7% 1	330
	21st to end	Day	8% 9% 51% 20% 9% 3	363
February	1st to 10th	Day	9% 12% 49% 25% 4	330
	11th to 20th	Day	12% 7% 48% 25% 6% 2	330
	21st to end	Day	9% 14% 52% 22% 4	273
March	1st to 10th	Day	11% 10% 42% 24% 12% 2	330
	11th to 20th	Day	14% 9% 34% 31% 11% 1	330
	21st to end	Day	19% 11% 38% 23% 6% 2	447
April	1st to 10th	Day	14% 14% 38% 25% 8% 1	540
	11th to 20th	Day	15% 17% 35% 25% 7%	553
	21st to end	Day	17% 13% 33% 25% 11% 2	750
May	1st to 10th	Day	13% 9% 31% 32% 13% 2	753
	11th to 20th	Day	18% 8% 30% 27% 14% 3	775
	21st to end	Day	17% 7% 30% 28% 16% 2	844
June	1st to 10th	Day	8% 5% 24% 34% 21% 8%	780
	11th to 20th	Day	8% 8% 34% 33% 15% 2	780
	21st to end	Day	7% 6% 29% 37% 18% 3	780
July	1st to 10th	Day	7% 3 23% 37% 26% 4	771
	11th to 20th	Day	6% 2 20% 42% 25% 6%	768
	21st to end	Day	6% 2 19% 43% 27% 4	849
August	1st to 10th	Day	8% 4 18% 41% 25% 4	776
	11th to 20th	Day	7% 3 23% 40% 24% 3	732
	21st to end	Day	7% 2 24% 39% 23% 6%	620
September	1st to 10th	Day	7% 4 24% 40% 20% 5%	520
	11th to 20th	Day	4 5% 20% 39% 23% 8%	330
	21st to end	Day	13% 7% 25% 32% 18% 5%	330
October	1st to 10th	Day	13% 5% 24% 31% 21% 7%	330
	11th to 20th	Day	8% 14% 38% 26% 12% 2	330
	21st to end	Day	12% 13% 29% 28% 14% 4	363
November	1st to 10th	Day	11% 10% 39% 24% 12% 3	330
	11th to 20th	Day	7% 11% 38% 32% 8% 2	330
	21st to end	Day	15% 7% 37% 29% 9% 4	330
December	1st to 10th	Day	8% 10% 46% 26% 8% 2	330
	11th to 20th	Day	12% 12% 41% 27% 8% 1	330
	21st to end	Day	13% 13% 42% 27% 5% 1	363
January	1st to 10th	Night	9% 10% 40% 31% 8% 1	1050
	11th to 20th	Night	8% 14% 41% 31% 6% 1	1050
	21st to end	Night	7% 10% 45% 31% 7% 1	1155
February	1st to 10th	Night	11% 11% 46% 27% 6%	933
	11th to 20th	Night	8% 10% 49% 29% 4	824
	21st to end	Night	8% 10% 50% 28% 4	692
March	1st to 10th	Night	10% 11% 42% 32% 5%	840
	11th to 20th	Night	11% 8% 43% 32% 5% 1	704
	21st to end	Night	13% 8% 42% 31% 6%	693
April	1st to 10th	Night	15% 12% 44% 27% 2	630
	11th to 20th	Night	17% 13% 43% 25% 3	623
	21st to end	Night	16% 12% 35% 30% 8%	630
May	1st to 10th	Night	13% 7% 34% 37% 9%	630
	11th to 20th	Night	18% 8% 34% 30% 10%	621
	21st to end	Night	17% 6% 33% 34% 9%	683
June	1st to 10th	Night	8% 5% 33% 40% 13% 1	630
	11th to 20th	Night	11% 6% 41% 35% 8%	630
	21st to end	Night	6% 6% 31% 46% 11%	630
July	1st to 10th	Night	7% 4 25% 47% 16% 1	615
	11th to 20th	Night	6% 2 25% 54% 13% 1	612
	21st to end	Night	5% 3 25% 51% 16%	690
August	1st to 10th	Night	7% 3 22% 51% 17%	627
	11th to 20th	Night	7% 3 23% 53% 14%	624
	21st to end	Night	6% 2 28% 49% 14%	687
September	1st to 10th	Night	9% 3 31% 44% 13% 1	600
	11th to 20th	Night	8% 3 32% 40% 15% 1	600
	21st to end	Night	11% 5% 32% 37% 15% 1	600
October	1st to 10th	Night	14% 7% 28% 40% 11% 1	600
	11th to 20th	Night	10% 10% 32% 37% 10% 1	791
	21st to end	Night	12% 10% 33% 35% 9% 1	1100
November	1st to 10th	Night	8% 8% 39% 37% 8% 1	1025
	11th to 20th	Night	7% 8% 43% 34% 8%	1050
	21st to end	Night	10% 7% 38% 36% 8% 1	1050
December	1st to 10th	Night	8% 12% 44% 30% 6% 1	1050
	11th to 20th	Night	9% 10% 43% 31% 7%	1050
	21st to end	Night	12% 11% 40% 32% 5%	1155

Page generated at 2026-08-27 03:07:16. Version ac07

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