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 2024-03-01.

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% 5% 2 5% 4 3 4 4 5% 7% 52%	78471
	Night	7% 6% 2 5% 5% 3 4 4 5% 7% 51%	80991
Transparency	Day	30% 6% 14% 28% 18% 4	78177
	Night	31% 6% 14% 28% 18% 4	80808
Seeing	Day	10% 7% 30% 32% 16% 3	14763
	Night	10% 8% 37% 36% 9%	24904

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% 9% 4 6% 5% 3 3 3 4 6% 52%	2538
	11th to 20th	Day	4 8% 3 6% 5% 3 5% 6% 8% 8% 44%	2540
	21st to end	Day	5% 5% 3 5% 4 3 4 4 6% 8% 53%	2803
February	1st to 10th	Day	7% 8% 4 8% 6% 4 4 4 5% 7% 42%	1833
	11th to 20th	Day	6% 8% 4 6% 6% 3 5% 4 4 7% 47%	1849
	21st to end	Day	8% 7% 3 4 4 1 3 4 5% 6% 56%	1570
March	1st to 10th	Day	7% 4 2 4 4 2 3 4 4 7% 57%	1800
	11th to 20th	Day	9% 7% 2 4 4 2 5% 4 6% 8% 48%	1914
	21st to end	Day	11% 9% 4 6% 6% 3 4 4 5% 8% 40%	2250
April	1st to 10th	Day	12% 6% 2 4 4 3 3 3 4 6% 52%	2160
	11th to 20th	Day	13% 8% 3 5% 5% 3 4 4 5% 7% 44%	2149
	21st to end	Day	14% 6% 3 5% 4 2 3 5% 5% 6% 47%	2340
May	1st to 10th	Day	13% 5% 2 5% 4 3 4 5% 5% 8% 46%	2340
	11th to 20th	Day	16% 5% 2 4 4 3 4 4 5% 8% 45%	2302
	21st to end	Day	13% 6% 2 5% 5% 3 4 5% 5% 7% 45%	2672
June	1st to 10th	Day	7% 3 1 3 4 2 4 4 6% 9% 56%	2520
	11th to 20th	Day	8% 4 2 4 4 2 4 5% 5% 7% 54%	2520
	21st to end	Day	4 2 1 3 4 2 3 5% 5% 8% 62%	2520
July	1st to 10th	Day	7% 3 2 4 4 2 4 5% 6% 9% 54%	2520
	11th to 20th	Day	5% 3 1 4 4 3 4 5% 6% 8% 58%	2520
	21st to end	Day	5% 3 2 4 4 3 5% 6% 6% 9% 52%	2729
August	1st to 10th	Day	7% 4 2 5% 6% 2 5% 5% 8% 10% 46%	2328
	11th to 20th	Day	6% 3 2 4 4 3 4 5% 5% 8% 57%	2274
	21st to end	Day	5% 3 2 5% 4 3 4 3 5% 7% 60%	2376
September	1st to 10th	Day	8% 4 1 3 3 2 3 4 5% 7% 59%	2152
	11th to 20th	Day	8% 4 1 3 3 1 3 4 5% 6% 61%	1980
	21st to end	Day	9% 5% 2 3 3 2 3 3 4 4 63%	1980
October	1st to 10th	Day	12% 6% 1 3 3 2 3 3 3 6% 58%	1980
	11th to 20th	Day	8% 5% 1 4 3 2 4 3 4 5% 60%	1787
	21st to end	Day	10% 5% 3 5% 3 2 3 3 4 6% 55%	1782
November	1st to 10th	Day	4 5% 1 4 3 2 5% 5% 6% 8% 57%	1673
	11th to 20th	Day	4 5% 2 4 5% 3 3 4 5% 7% 59%	1710
	21st to end	Day	7% 7% 2 4 2 2 3 5% 5% 5% 58%	1710
December	1st to 10th	Day	6% 8% 3 5% 5% 3 3 5% 5% 7% 51%	1630
	11th to 20th	Day	6% 5% 3 5% 4 2 3 3 5% 7% 57%	1926
	21st to end	Day	10% 11% 4 7% 5% 3 4 4 4 6% 42%	2794
January	1st to 10th	Night	5% 10% 2 8% 7% 3 5% 5% 5% 7% 42%	4417
	11th to 20th	Night	3 8% 4 7% 5% 3 4 5% 5% 6% 52%	4430
	21st to end	Night	3 5% 4 7% 6% 3 5% 4 5% 7% 51%	4863
February	1st to 10th	Night	8% 9% 4 7% 6% 3 4 4 4 7% 43%	2365
	11th to 20th	Night	4 7% 3 6% 7% 3 4 5% 5% 8% 46%	2218
	21st to end	Night	4 7% 2 5% 6% 3 4 4 6% 7% 52%	1884
March	1st to 10th	Night	7% 7% 3 5% 4 2 4 3 5% 7% 53%	2166
	11th to 20th	Night	9% 7% 3 4 4 2 3 4 4 7% 53%	2044
	21st to end	Night	10% 8% 3 5% 5% 3 5% 5% 6% 8% 42%	2102
April	1st to 10th	Night	11% 7% 3 4 5% 2 5% 4 5% 8% 46%	1800
	11th to 20th	Night	13% 8% 2 4 4 2 4 4 5% 7% 47%	1759
	21st to end	Night	13% 6% 2 6% 5% 2 4 5% 5% 7% 45%	1620
May	1st to 10th	Night	11% 5% 2 5% 4 3 5% 6% 6% 9% 44%	1620
	11th to 20th	Night	15% 7% 2 4 4 2 4 4 5% 8% 45%	1593
	21st to end	Night	15% 7% 3 5% 5% 3 5% 5% 7% 8% 39%	1601
June	1st to 10th	Night	7% 5% 2 3 3 2 5% 5% 6% 10% 51%	1440
	11th to 20th	Night	9% 5% 2 4 4 2 5% 6% 7% 10% 47%	1440
	21st to end	Night	4 3 2 5% 5% 3 5% 6% 7% 10% 49%	1440
July	1st to 10th	Night	6% 5% 2 4 5% 2 4 4 6% 9% 53%	1440
	11th to 20th	Night	4 3 2 4 4 2 4 5% 7% 7% 57%	1440
	21st to end	Night	5% 3 2 4 5% 4 5% 5% 7% 10% 51%	1586
August	1st to 10th	Night	6% 4 1 5% 7% 3 5% 5% 8% 10% 46%	1611
	11th to 20th	Night	6% 3 2 4 4 3 4 5% 6% 9% 55%	1624
	21st to end	Night	4 4 1 4 3 2 4 4 6% 7% 60%	1980
September	1st to 10th	Night	9% 4 1 3 3 2 3 3 5% 6% 60%	1808
	11th to 20th	Night	7% 4 2 3 4 3 3 4 5% 6% 59%	1980
	21st to end	Night	10% 3 2 3 3 2 3 3 4 6% 61%	1980
October	1st to 10th	Night	13% 4 2 4 4 2 3 3 4 6% 56%	1980
	11th to 20th	Night	8% 4 1 3 3 2 4 3 4 7% 61%	2151
	21st to end	Night	9% 6% 2 4 4 2 3 4 4 5% 58%	2574
November	1st to 10th	Night	5% 4 2 3 4 2 4 4 5% 7% 59%	2405
	11th to 20th	Night	5% 3 2 4 5% 3 5% 5% 6% 7% 55%	2470
	21st to end	Night	6% 5% 1 4 5% 2 4 4 4 8% 56%	2470
December	1st to 10th	Night	5% 6% 3 5% 4 2 3 3 5% 8% 55%	2546
	11th to 20th	Night	5% 5% 2 5% 4 3 4 4 5% 8% 56%	3271
	21st to end	Night	12% 11% 3 5% 5% 2 4 4 4 6% 45%	4873

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	35% 4 10% 33% 17% 1	2539
	11th to 20th	Day	33% 10% 12% 26% 16% 4	2540
	21st to end	Day	28% 6% 18% 29% 15% 3	2803
February	1st to 10th	Day	42% 5% 14% 22% 13% 4	1833
	11th to 20th	Day	37% 6% 11% 24% 18% 4	1859
	21st to end	Day	29% 4 13% 31% 18% 5%	1570
March	1st to 10th	Day	27% 5% 13% 29% 23% 4	1800
	11th to 20th	Day	32% 7% 14% 26% 18% 3	1914
	21st to end	Day	43% 6% 17% 22% 11% 1	2250
April	1st to 10th	Day	34% 4 16% 27% 15% 3	2160
	11th to 20th	Day	39% 6% 13% 23% 15% 3	2152
	21st to end	Day	36% 5% 13% 27% 17% 1	2340
May	1st to 10th	Day	36% 6% 16% 28% 13% 1	2340
	11th to 20th	Day	38% 7% 20% 25% 10% 1	2306
	21st to end	Day	37% 8% 17% 24% 12% 2	2672
June	1st to 10th	Day	24% 7% 20% 34% 13% 2	2520
	11th to 20th	Day	28% 6% 15% 26% 18% 6%	2520
	21st to end	Day	18% 7% 14% 33% 23% 5%	2520
July	1st to 10th	Day	25% 7% 14% 30% 20% 4	2451
	11th to 20th	Day	23% 6% 11% 28% 25% 8%	2445
	21st to end	Day	24% 8% 16% 30% 19% 3	2577
August	1st to 10th	Day	30% 10% 17% 27% 12% 4	2314
	11th to 20th	Day	25% 7% 15% 31% 20% 3	2274
	21st to end	Day	24% 5% 10% 26% 26% 8%	2376
September	1st to 10th	Day	25% 4 10% 27% 23% 11%	2152
	11th to 20th	Day	22% 5% 11% 30% 26% 6%	1980
	21st to end	Day	25% 3 8% 31% 28% 5%	1980
October	1st to 10th	Day	30% 4 9% 27% 26% 4	1980
	11th to 20th	Day	27% 5% 10% 29% 21% 8%	1787
	21st to end	Day	30% 5% 9% 30% 20% 6%	1782
November	1st to 10th	Day	24% 6% 15% 29% 21% 5%	1673
	11th to 20th	Day	25% 4 11% 29% 26% 5%	1710
	21st to end	Day	27% 4 12% 30% 21% 5%	1710
December	1st to 10th	Day	32% 5% 12% 30% 18% 3	1630
	11th to 20th	Day	27% 4 15% 37% 16% 1	1924
	21st to end	Day	43% 5% 9% 28% 13% 2	2794
January	1st to 10th	Night	40% 5% 12% 27% 15% 1	4417
	11th to 20th	Night	31% 6% 16% 28% 17% 1	4430
	21st to end	Night	33% 6% 15% 29% 17% 1	4863
February	1st to 10th	Night	40% 7% 13% 23% 14% 3	2365
	11th to 20th	Night	35% 6% 14% 28% 14% 3	2218
	21st to end	Night	31% 5% 13% 26% 19% 6%	1884
March	1st to 10th	Night	32% 4 12% 28% 19% 5%	2166
	11th to 20th	Night	31% 5% 11% 28% 22% 3	2044
	21st to end	Night	39% 8% 16% 24% 12% 2	2102
April	1st to 10th	Night	36% 6% 14% 24% 16% 4	1800
	11th to 20th	Night	38% 6% 13% 25% 15% 3	1759
	21st to end	Night	38% 7% 13% 27% 14% 1	1620
May	1st to 10th	Night	35% 8% 18% 24% 14% 1	1620
	11th to 20th	Night	37% 7% 18% 25% 11% 1	1594
	21st to end	Night	42% 9% 18% 20% 9% 2	1602
June	1st to 10th	Night	26% 10% 23% 28% 12% 2	1440
	11th to 20th	Night	31% 7% 18% 25% 13% 6%	1440
	21st to end	Night	27% 8% 17% 29% 18% 2	1440
July	1st to 10th	Night	28% 7% 18% 30% 14% 3	1400
	11th to 20th	Night	23% 9% 14% 28% 22% 5%	1392
	21st to end	Night	25% 8% 17% 29% 18% 3	1498
August	1st to 10th	Night	30% 10% 20% 25% 12% 3	1601
	11th to 20th	Night	24% 8% 15% 31% 18% 4	1624
	21st to end	Night	22% 6% 12% 27% 24% 8%	1980
September	1st to 10th	Night	25% 4 11% 24% 27% 9%	1808
	11th to 20th	Night	25% 6% 12% 28% 23% 7%	1980
	21st to end	Night	25% 4 9% 29% 28% 5%	1980
October	1st to 10th	Night	29% 6% 9% 27% 25% 4	1980
	11th to 20th	Night	24% 4 10% 30% 23% 9%	2151
	21st to end	Night	29% 4 12% 24% 23% 8%	2574
November	1st to 10th	Night	23% 5% 12% 29% 23% 7%	2405
	11th to 20th	Night	26% 5% 13% 27% 24% 5%	2470
	21st to end	Night	27% 5% 11% 29% 23% 4	2470
December	1st to 10th	Night	29% 4 15% 29% 19% 4	2546
	11th to 20th	Night	27% 4 12% 37% 18% 1	3272
	21st to end	Night	40% 5% 11% 29% 13% 2	4873

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	9% 6% 42% 28% 13% 2	270
	11th to 20th	Day	10% 12% 36% 33% 7% 1	270
	21st to end	Day	9% 9% 49% 19% 10% 4	297
February	1st to 10th	Day	10% 11% 50% 24% 5%	270
	11th to 20th	Day	12% 6% 48% 24% 7% 2	270
	21st to end	Day	11% 13% 48% 23% 4	225
March	1st to 10th	Day	11% 10% 40% 24% 13% 2	240
	11th to 20th	Day	15% 6% 33% 34% 11% 1	240
	21st to end	Day	21% 9% 38% 23% 7% 2	336
April	1st to 10th	Day	14% 14% 37% 26% 8%	420
	11th to 20th	Day	16% 15% 36% 26% 7%	430
	21st to end	Day	16% 12% 33% 25% 13% 2	600
May	1st to 10th	Day	14% 8% 31% 33% 12% 2	603
	11th to 20th	Day	20% 7% 29% 25% 16% 3	625
	21st to end	Day	17% 7% 30% 28% 17% 2	679
June	1st to 10th	Day	7% 3 22% 34% 23% 10%	630
	11th to 20th	Day	7% 6% 35% 34% 16% 2	630
	21st to end	Day	5% 5% 26% 40% 21% 3	630
July	1st to 10th	Day	7% 3 23% 37% 26% 4	621
	11th to 20th	Day	6% 2 21% 41% 23% 6%	618
	21st to end	Day	6% 2 17% 43% 28% 4	684
August	1st to 10th	Day	7% 4 16% 43% 26% 4	626
	11th to 20th	Day	6% 3 24% 40% 26% 3	588
	21st to end	Day	6% 2 25% 39% 21% 7%	495
September	1st to 10th	Day	8% 5% 25% 39% 18% 6%	442
	11th to 20th	Day	4 5% 17% 39% 26% 10%	270
	21st to end	Day	15% 7% 25% 33% 17% 3	270
October	1st to 10th	Day	16% 5% 21% 31% 20% 7%	270
	11th to 20th	Day	8% 12% 35% 28% 14% 2	270
	21st to end	Day	13% 14% 26% 29% 15% 3	297
November	1st to 10th	Day	7% 10% 39% 26% 14% 4	270
	11th to 20th	Day	7% 11% 37% 33% 9% 2	270
	21st to end	Day	15% 6% 39% 27% 9% 4	270
December	1st to 10th	Day	9% 9% 44% 27% 8% 3	270
	11th to 20th	Day	11% 11% 40% 28% 9% 1	270
	21st to end	Day	14% 14% 41% 26% 4 1	297
January	1st to 10th	Night	9% 11% 39% 31% 8% 1	950
	11th to 20th	Night	8% 13% 40% 32% 6% 1	950
	21st to end	Night	7% 10% 44% 30% 8% 1	1045
February	1st to 10th	Night	12% 10% 44% 27% 6%	845
	11th to 20th	Night	7% 9% 50% 29% 5%	744
	21st to end	Night	9% 10% 49% 28% 4	628
March	1st to 10th	Night	10% 11% 41% 32% 5%	722
	11th to 20th	Night	11% 8% 43% 32% 5% 1	604
	21st to end	Night	14% 7% 40% 31% 7%	594
April	1st to 10th	Night	14% 11% 44% 28% 2	540
	11th to 20th	Night	18% 12% 41% 26% 3	533
	21st to end	Night	15% 11% 34% 31% 9%	540
May	1st to 10th	Night	12% 6% 35% 37% 9%	540
	11th to 20th	Night	19% 7% 32% 31% 10%	531
	21st to end	Night	16% 6% 32% 35% 10% 1	584
June	1st to 10th	Night	9% 5% 31% 41% 14% 1	540
	11th to 20th	Night	11% 5% 41% 35% 9%	540
	21st to end	Night	4 4 29% 50% 12%	540
July	1st to 10th	Night	6% 4 25% 47% 17% 1	525
	11th to 20th	Night	5% 2 25% 54% 13% 1	522
	21st to end	Night	5% 2 24% 51% 17%	591
August	1st to 10th	Night	7% 2 20% 50% 20%	537
	11th to 20th	Night	6% 2 23% 54% 15%	534
	21st to end	Night	5% 2 29% 48% 15%	594
September	1st to 10th	Night	10% 3 31% 42% 14% 1	540
	11th to 20th	Night	8% 3 30% 42% 15% 1	540
	21st to end	Night	11% 5% 32% 38% 14% 1	540
October	1st to 10th	Night	15% 7% 27% 39% 11% 1	540
	11th to 20th	Night	10% 9% 32% 39% 11% 1	711
	21st to end	Night	12% 10% 32% 36% 10% 1	990
November	1st to 10th	Night	7% 6% 39% 38% 9% 1	925
	11th to 20th	Night	7% 8% 42% 34% 9%	950
	21st to end	Night	9% 7% 37% 37% 9% 1	950
December	1st to 10th	Night	8% 12% 43% 30% 6% 1	950
	11th to 20th	Night	9% 9% 42% 32% 8%	950
	21st to end	Night	12% 12% 38% 32% 6%	1045

Page generated at 2024-02-27 05:30:15. Version ac07

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