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 2025-04-26.

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%	117295
	Night	7% 6% 2 6% 4 4 4 3 5% 7% 52%	120097
Transparency	Day	29% 6% 13% 28% 20% 5%	117041
	Night	31% 5% 13% 27% 20% 4	119942
Seeing	Day	11% 8% 31% 32% 16% 3	16349
	Night	10% 8% 37% 36% 9%	26441

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% 12% 4 8% 5% 4 4 2 4 6% 46%	3638
	11th to 20th	Day	4 8% 3 6% 4 5% 5% 4 6% 7% 48%	3640
	21st to end	Day	4 5% 3 7% 4 4 4 4 6% 7% 53%	4026
February	1st to 10th	Day	7% 10% 4 9% 5% 5% 4 3 5% 7% 42%	1930
	11th to 20th	Day	6% 9% 3 7% 5% 4 4 4 4 7% 46%	1949
	21st to end	Day	7% 7% 3 5% 3 2 3 2 5% 6% 57%	1650
March	1st to 10th	Day	9% 7% 2 5% 3 2 3 3 4 5% 56%	4500
	11th to 20th	Day	7% 6% 1 4 3 3 4 3 4 7% 58%	4836
	21st to end	Day	11% 8% 3 6% 4 4 3 3 6% 8% 45%	5647
April	1st to 10th	Day	11% 7% 2 4 3 4 3 4 5% 7% 51%	2400
	11th to 20th	Day	12% 8% 2 6% 4 4 4 3 5% 7% 45%	2391
	21st to end	Day	14% 6% 2 5% 4 3 4 4 5% 6% 47%	2536
May	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 6% 7% 47%	4120
	11th to 20th	Day	11% 5% 2 5% 3 4 4 3 5% 8% 51%	4082
	21st to end	Day	13% 5% 1 5% 4 4 4 4 5% 7% 47%	4734
June	1st to 10th	Day	7% 4 1 4 3 3 4 3 7% 9% 56%	2660
	11th to 20th	Day	8% 5% 2 4 4 3 4 4 6% 7% 54%	2660
	21st to end	Day	4 2 1 4 3 3 3 4 6% 8% 61%	2660
July	1st to 10th	Day	7% 3 2 5% 4 3 4 4 6% 8% 54%	4430
	11th to 20th	Day	4 3 1 5% 4 4 5% 5% 7% 10% 52%	4430
	21st to end	Day	3 3 1 4 3 4 4 4 7% 9% 58%	4777
August	1st to 10th	Day	10% 5% 2 5% 4 3 4 4 7% 9% 48%	4103
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 6% 8% 46%	3986
	21st to end	Day	4 3 1 5% 3 4 4 3 5% 7% 62%	4180
September	1st to 10th	Day	8% 4 1 3 3 3 3 3 6% 7% 60%	2271
	11th to 20th	Day	7% 4 1 4 3 2 3 3 6% 6% 60%	2090
	21st to end	Day	8% 5% 1 4 2 2 3 2 4 4 63%	2090
October	1st to 10th	Day	7% 4 1 2 1 1 1 1 2 4 75%	3480
	11th to 20th	Day	8% 4 1 4 2 3 3 2 4 6% 63%	3120
	21st to end	Day	8% 6% 2 5% 4 4 3 3 5% 7% 55%	3091
November	1st to 10th	Day	6% 6% 1 4 3 3 4 3 7% 7% 55%	1763
	11th to 20th	Day	4 5% 2 5% 4 3 3 3 5% 6% 60%	1800
	21st to end	Day	7% 7% 2 4 2 3 3 4 5% 6% 57%	1800
December	1st to 10th	Day	3 5% 1 4 4 4 3 3 5% 6% 61%	2795
	11th to 20th	Day	4 5% 2 5% 4 3 3 3 5% 7% 59%	3026
	21st to end	Day	8% 10% 3 7% 4 4 4 3 5% 7% 44%	4004
January	1st to 10th	Night	5% 11% 3 11% 6% 4 6% 4 5% 6% 38%	6327
	11th to 20th	Night	2 7% 3 8% 4 4 5% 4 5% 6% 52%	6340
	21st to end	Night	3 5% 3 8% 6% 5% 4 3 4 6% 53%	6951
February	1st to 10th	Night	8% 10% 3 8% 5% 3 4 4 5% 7% 43%	2489
	11th to 20th	Night	4 9% 3 8% 6% 5% 4 4 5% 8% 44%	2338
	21st to end	Night	4 7% 2 6% 4 4 4 3 6% 7% 53%	1980
March	1st to 10th	Night	8% 6% 2 5% 3 3 3 2 4 5% 56%	5374
	11th to 20th	Night	7% 7% 2 4 3 3 4 3 4 6% 57%	5128
	21st to end	Night	8% 8% 3 8% 5% 5% 5% 4 6% 8% 39%	5275
April	1st to 10th	Night	11% 8% 2 5% 4 4 4 3 6% 7% 46%	2000
	11th to 20th	Night	12% 7% 2 4 4 4 3 4 5% 7% 48%	1957
	21st to end	Night	14% 7% 2 7% 4 3 4 4 5% 7% 44%	1760
May	1st to 10th	Night	16% 6% 2 6% 4 3 5% 4 5% 7% 43%	2850
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 7% 8% 48%	2823
	21st to end	Night	13% 6% 2 5% 4 4 4 4 6% 8% 44%	2837
June	1st to 10th	Night	7% 5% 2 4 3 3 5% 4 6% 10% 51%	1520
	11th to 20th	Night	9% 6% 2 5% 3 3 4 5% 7% 9% 47%	1520
	21st to end	Night	4 3 1 6% 5% 5% 5% 5% 7% 11% 49%	1520
July	1st to 10th	Night	10% 4 1 5% 4 3 3 3 5% 6% 55%	2540
	11th to 20th	Night	5% 4 2 5% 4 4 5% 3 8% 9% 51%	2540
	21st to end	Night	3 3 1 4 4 4 4 4 7% 9% 57%	2783
August	1st to 10th	Night	7% 5% 3 7% 4 4 5% 4 8% 10% 43%	2836
	11th to 20th	Night	11% 5% 2 6% 4 4 5% 4 6% 8% 45%	2850
	21st to end	Night	4 4 1 5% 3 4 4 4 7% 9% 54%	3487
September	1st to 10th	Night	8% 4 1 4 3 3 3 3 6% 6% 60%	1909
	11th to 20th	Night	6% 4 1 4 3 4 3 3 5% 7% 59%	2090
	21st to end	Night	9% 3 1 4 3 2 2 3 4 6% 62%	2090
October	1st to 10th	Night	7% 2 1 2 2 2 1 2 2 3 75%	3480
	11th to 20th	Night	9% 3 1 3 2 3 3 2 4 6% 65%	3768
	21st to end	Night	7% 5% 2 5% 4 3 4 3 5% 6% 56%	4467
November	1st to 10th	Night	5% 5% 2 4 4 3 3 4 5% 7% 57%	2535
	11th to 20th	Night	5% 5% 1 4 4 4 5% 4 6% 7% 56%	2600
	21st to end	Night	6% 6% 1 4 4 3 4 3 4 8% 56%	2600
December	1st to 10th	Night	3 4 2 4 3 3 3 3 5% 7% 63%	4378
	11th to 20th	Night	3 6% 2 5% 4 4 4 4 5% 8% 55%	5181
	21st to end	Night	9% 10% 3 6% 4 4 4 3 5% 6% 44%	6974

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	40% 3 9% 31% 16% 1	3639
	11th to 20th	Day	34% 7% 10% 25% 21% 3	3640
	21st to end	Day	30% 5% 15% 26% 20% 4	4026
February	1st to 10th	Day	42% 5% 14% 21% 13% 4	1930
	11th to 20th	Day	38% 6% 11% 24% 18% 4	1959
	21st to end	Day	28% 4 12% 32% 19% 5%	1650
March	1st to 10th	Day	30% 4 7% 25% 29% 5%	4500
	11th to 20th	Day	27% 4 11% 27% 30% 2	4836
	21st to end	Day	37% 6% 19% 24% 12% 1	5647
April	1st to 10th	Day	33% 4 16% 28% 16% 3	2400
	11th to 20th	Day	38% 6% 13% 23% 16% 3	2394
	21st to end	Day	37% 6% 14% 27% 16% 1	2536
May	1st to 10th	Day	31% 9% 15% 22% 17% 6%	4120
	11th to 20th	Day	30% 8% 16% 28% 16% 1	4086
	21st to end	Day	34% 8% 16% 28% 11% 3	4734
June	1st to 10th	Day	24% 7% 21% 33% 13% 2	2660
	11th to 20th	Day	29% 6% 14% 27% 18% 6%	2660
	21st to end	Day	18% 7% 14% 33% 23% 5%	2660
July	1st to 10th	Day	26% 6% 11% 26% 27% 4	4361
	11th to 20th	Day	25% 7% 12% 31% 21% 5%	4355
	21st to end	Day	19% 7% 14% 26% 25% 10%	4626
August	1st to 10th	Day	31% 7% 14% 27% 18% 3	4090
	11th to 20th	Day	36% 7% 14% 23% 19% 2	4025
	21st to end	Day	22% 5% 16% 22% 23% 12%	4179
September	1st to 10th	Day	24% 4 10% 28% 24% 10%	2271
	11th to 20th	Day	22% 5% 11% 30% 26% 6%	2090
	21st to end	Day	25% 3 8% 30% 28% 6%	2090
October	1st to 10th	Day	17% 2 6% 22% 35% 18%	3480
	11th to 20th	Day	24% 4 11% 36% 21% 4	3120
	21st to end	Day	30% 4 8% 34% 18% 6%	3091
November	1st to 10th	Day	25% 6% 14% 29% 20% 5%	1763
	11th to 20th	Day	25% 4 11% 29% 26% 6%	1800
	21st to end	Day	27% 4 12% 30% 21% 5%	1800
December	1st to 10th	Day	24% 4 12% 34% 23% 3	2795
	11th to 20th	Day	25% 3 18% 34% 17% 3	3024
	21st to end	Day	39% 5% 9% 33% 13% 1	4004
January	1st to 10th	Night	45% 5% 11% 23% 14% 3	6327
	11th to 20th	Night	31% 6% 13% 25% 24% 1	6340
	21st to end	Night	33% 5% 11% 27% 21% 4	6951
February	1st to 10th	Night	40% 6% 12% 23% 15% 3	2489
	11th to 20th	Night	37% 6% 13% 27% 14% 3	2338
	21st to end	Night	29% 5% 12% 27% 20% 6%	1980
March	1st to 10th	Night	30% 4 7% 25% 28% 5%	5374
	11th to 20th	Night	29% 3 8% 25% 29% 5%	5128
	21st to end	Night	40% 9% 16% 23% 11% 1	5275
April	1st to 10th	Night	36% 6% 14% 25% 17% 3	2000
	11th to 20th	Night	36% 6% 13% 26% 16% 3	1957
	21st to end	Night	38% 7% 14% 26% 13% 2	1760
May	1st to 10th	Night	37% 8% 14% 23% 14% 4	2850
	11th to 20th	Night	30% 10% 17% 32% 9% 1	2824
	21st to end	Night	37% 9% 17% 27% 8% 2	2838
June	1st to 10th	Night	26% 10% 23% 27% 12% 2	1520
	11th to 20th	Night	32% 7% 18% 25% 12% 6%	1520
	21st to end	Night	27% 8% 17% 28% 19% 2	1520
July	1st to 10th	Night	30% 6% 14% 31% 18% 2	2500
	11th to 20th	Night	27% 7% 16% 27% 19% 3	2492
	21st to end	Night	21% 7% 15% 25% 24% 8%	2696
August	1st to 10th	Night	35% 7% 18% 26% 13% 2	2826
	11th to 20th	Night	36% 7% 14% 25% 15% 2	2877
	21st to end	Night	26% 6% 14% 25% 19% 10%	3487
September	1st to 10th	Night	24% 4 10% 25% 28% 8%	1909
	11th to 20th	Night	25% 6% 12% 28% 23% 7%	2090
	21st to end	Night	25% 4 8% 28% 28% 6%	2090
October	1st to 10th	Night	17% 3 5% 19% 47% 9%	3480
	11th to 20th	Night	22% 4 9% 32% 26% 7%	3768
	21st to end	Night	29% 4 12% 26% 24% 5%	4467
November	1st to 10th	Night	25% 5% 12% 29% 22% 7%	2535
	11th to 20th	Night	25% 5% 12% 27% 24% 6%	2600
	21st to end	Night	27% 5% 11% 30% 23% 4	2600
December	1st to 10th	Night	22% 3 16% 34% 21% 4	4378
	11th to 20th	Night	28% 4 14% 36% 17% 2	5182
	21st to end	Night	40% 5% 10% 29% 15% 1	6974

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% 41% 28% 13% 2	300
	11th to 20th	Day	10% 13% 36% 32% 8% 1	300
	21st to end	Day	8% 8% 52% 19% 9% 3	330
February	1st to 10th	Day	10% 13% 49% 24% 4	300
	11th to 20th	Day	13% 7% 47% 24% 7% 2	300
	21st to end	Day	10% 14% 50% 22% 4	249
March	1st to 10th	Day	12% 10% 39% 25% 12% 2	300
	11th to 20th	Day	14% 8% 34% 31% 12% 1	300
	21st to end	Day	21% 10% 38% 22% 7% 2	410
April	1st to 10th	Day	15% 15% 37% 24% 9% 1	500
	11th to 20th	Day	15% 16% 36% 26% 7%	512
	21st to end	Day	16% 12% 33% 26% 12% 2	676
May	1st to 10th	Day	14% 10% 31% 32% 12% 2	653
	11th to 20th	Day	19% 7% 29% 27% 16% 3	675
	21st to end	Day	16% 7% 31% 28% 17% 2	734
June	1st to 10th	Day	7% 4 23% 35% 22% 9%	680
	11th to 20th	Day	8% 7% 35% 33% 15% 2	680
	21st to end	Day	5% 6% 28% 39% 20% 3	680
July	1st to 10th	Day	8% 4 24% 35% 25% 5%	671
	11th to 20th	Day	5% 2 21% 42% 24% 6%	668
	21st to end	Day	6% 2 18% 43% 28% 4	739
August	1st to 10th	Day	8% 4 16% 42% 26% 4	676
	11th to 20th	Day	7% 3 24% 39% 24% 3	636
	21st to end	Day	6% 2 25% 39% 22% 7%	539
September	1st to 10th	Day	7% 4 24% 40% 19% 6%	481
	11th to 20th	Day	3 5% 20% 39% 24% 9%	300
	21st to end	Day	13% 8% 25% 32% 18% 4	300
October	1st to 10th	Day	14% 5% 22% 31% 21% 7%	300
	11th to 20th	Day	8% 11% 37% 29% 14% 2	300
	21st to end	Day	13% 13% 28% 29% 15% 3	330
November	1st to 10th	Day	11% 11% 37% 25% 13% 3	300
	11th to 20th	Day	8% 12% 37% 32% 9% 2	300
	21st to end	Day	14% 7% 38% 29% 9% 4	300
December	1st to 10th	Day	8% 10% 44% 27% 9% 2	300
	11th to 20th	Day	11% 11% 40% 28% 9% 1	300
	21st to end	Day	14% 13% 41% 27% 5% 1	330
January	1st to 10th	Night	10% 11% 39% 31% 8% 1	1000
	11th to 20th	Night	8% 13% 41% 32% 6% 1	1000
	21st to end	Night	7% 10% 44% 31% 8% 1	1100
February	1st to 10th	Night	11% 11% 45% 26% 6%	889
	11th to 20th	Night	8% 9% 49% 28% 5%	784
	21st to end	Night	8% 10% 49% 28% 4	660
March	1st to 10th	Night	10% 11% 41% 33% 5%	800
	11th to 20th	Night	11% 7% 43% 32% 5% 1	670
	21st to end	Night	13% 7% 41% 31% 6%	660
April	1st to 10th	Night	15% 12% 44% 27% 2	600
	11th to 20th	Night	17% 12% 42% 26% 3	593
	21st to end	Night	16% 11% 35% 30% 8%	587
May	1st to 10th	Night	13% 7% 35% 36% 9%	570
	11th to 20th	Night	18% 7% 32% 32% 10%	561
	21st to end	Night	16% 6% 33% 35% 10%	617
June	1st to 10th	Night	8% 5% 31% 42% 13% 1	570
	11th to 20th	Night	11% 5% 41% 34% 8%	570
	21st to end	Night	4 4 31% 49% 11%	570
July	1st to 10th	Night	7% 4 25% 47% 17% 1	555
	11th to 20th	Night	5% 2 26% 54% 13% 1	552
	21st to end	Night	5% 3 24% 52% 17%	624
August	1st to 10th	Night	8% 2 21% 50% 19%	567
	11th to 20th	Night	7% 3 23% 54% 14%	564
	21st to end	Night	5% 3 29% 49% 14%	627
September	1st to 10th	Night	9% 3 31% 42% 14% 1	570
	11th to 20th	Night	8% 4 31% 41% 15% 1	570
	21st to end	Night	11% 5% 32% 38% 14% 1	570
October	1st to 10th	Night	14% 7% 27% 39% 12% 1	570
	11th to 20th	Night	10% 9% 32% 38% 10% 1	751
	21st to end	Night	12% 10% 33% 35% 9% 1	1045
November	1st to 10th	Night	8% 7% 38% 38% 8% 1	975
	11th to 20th	Night	7% 8% 43% 33% 9%	1000
	21st to end	Night	9% 7% 38% 37% 8% 1	1000
December	1st to 10th	Night	7% 12% 43% 31% 6% 1	1000
	11th to 20th	Night	9% 10% 43% 31% 7%	1000
	21st to end	Night	12% 12% 39% 32% 6%	1100

Page generated at 2025-04-23 08:25:06. Version ac07

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