Wayah Bald
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wayah Bald clear sky chart from 2005-11-06 to 2024-02-25.

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% 7% 3 7% 6% 4 5% 5% 6% 7% 36%	78795
	Night	12% 8% 3 6% 6% 3 5% 5% 5% 7% 39%	80518
Transparency	Day	45% 8% 11% 16% 16% 4	78518
	Night	42% 8% 12% 17% 17% 5%	80314
Seeing	Day	18% 14% 24% 20% 16% 8%	13931
	Night	16% 11% 21% 27% 20% 4	24089

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	14% 8% 4 6% 5% 3 4 5% 6% 7% 38%	2836
	11th to 20th	Day	12% 8% 4 8% 5% 3 4 3 4 5% 43%	2840
	21st to end	Day	20% 11% 4 5% 4 2 3 3 3 5% 40%	3124
February	1st to 10th	Day	14% 10% 3 7% 6% 3 4 4 4 6% 38%	1879
	11th to 20th	Day	15% 8% 3 8% 6% 3 4 4 5% 6% 37%	1848
	21st to end	Day	16% 10% 4 8% 5% 3 4 4 4 6% 36%	1520
March	1st to 10th	Day	12% 8% 3 6% 5% 3 5% 5% 5% 7% 42%	1880
	11th to 20th	Day	17% 7% 4 7% 6% 3 5% 4 7% 7% 33%	1980
	21st to end	Day	14% 10% 4 7% 6% 4 5% 5% 5% 6% 35%	2178
April	1st to 10th	Day	11% 7% 3 6% 5% 3 5% 6% 7% 6% 41%	1987
	11th to 20th	Day	14% 6% 3 6% 6% 3 5% 5% 5% 6% 40%	2161
	21st to end	Day	12% 6% 3 6% 5% 4 5% 5% 5% 7% 43%	2340
May	1st to 10th	Day	12% 7% 3 7% 6% 4 5% 5% 6% 7% 38%	2340
	11th to 20th	Day	15% 8% 4 7% 8% 4 5% 5% 5% 7% 30%	2301
	21st to end	Day	12% 7% 3 7% 6% 4 6% 6% 7% 10% 31%	2531
June	1st to 10th	Day	12% 7% 3 8% 9% 5% 7% 6% 7% 9% 29%	2340
	11th to 20th	Day	7% 5% 3 9% 8% 5% 7% 7% 8% 9% 32%	2340
	21st to end	Day	9% 5% 3 7% 8% 5% 7% 7% 9% 9% 30%	2340
July	1st to 10th	Day	9% 8% 4 10% 9% 5% 8% 7% 8% 9% 22%	2340
	11th to 20th	Day	13% 7% 3 7% 10% 6% 8% 9% 8% 8% 21%	2340
	21st to end	Day	10% 6% 3 8% 9% 6% 8% 9% 8% 8% 24%	2547
August	1st to 10th	Day	12% 6% 4 9% 9% 5% 8% 8% 7% 10% 22%	2327
	11th to 20th	Day	13% 7% 4 9% 8% 5% 7% 6% 7% 10% 24%	2275
	21st to end	Day	14% 8% 3 8% 9% 6% 7% 6% 6% 8% 25%	2358
September	1st to 10th	Day	13% 6% 3 8% 8% 5% 5% 6% 6% 7% 32%	1980
	11th to 20th	Day	15% 7% 3 7% 7% 4 5% 6% 6% 8% 31%	1980
	21st to end	Day	14% 7% 2 6% 7% 4 5% 4 5% 7% 39%	1980
October	1st to 10th	Day	13% 6% 3 5% 4 3 4 5% 5% 7% 47%	1980
	11th to 20th	Day	11% 7% 2 4 4 2 4 5% 4 6% 50%	1828
	21st to end	Day	13% 5% 3 4 4 3 3 4 3 6% 52%	1980
November	1st to 10th	Day	10% 5% 2 4 5% 3 3 4 4 5% 55%	1708
	11th to 20th	Day	13% 5% 3 4 4 2 5% 4 5% 7% 49%	1710
	21st to end	Day	13% 8% 3 6% 5% 3 4 4 5% 6% 45%	1710
December	1st to 10th	Day	17% 9% 4 8% 6% 3 4 5% 5% 6% 35%	1710
	11th to 20th	Day	14% 7% 3 6% 5% 3 5% 4 4 6% 43%	2153
	21st to end	Day	15% 8% 4 7% 6% 3 3 5% 5% 6% 37%	3124
January	1st to 10th	Night	13% 11% 5% 6% 5% 3 4 4 5% 6% 38%	4109
	11th to 20th	Night	10% 10% 3 7% 6% 3 4 4 4 5% 43%	4120
	21st to end	Night	19% 15% 4 6% 5% 2 3 3 3 4 36%	4532
February	1st to 10th	Night	11% 7% 4 7% 6% 3 5% 5% 5% 6% 40%	2299
	11th to 20th	Night	15% 9% 4 8% 6% 3 5% 4 4 5% 37%	2218
	21st to end	Night	17% 8% 5% 8% 5% 3 5% 4 5% 5% 33%	1831
March	1st to 10th	Night	9% 8% 4 7% 5% 3 5% 5% 5% 6% 42%	2078
	11th to 20th	Night	14% 9% 4 7% 6% 3 5% 4 6% 8% 36%	1980
	21st to end	Night	13% 8% 4 6% 7% 4 5% 5% 5% 6% 37%	2178
April	1st to 10th	Night	11% 6% 3 5% 6% 3 4 5% 6% 7% 45%	1980
	11th to 20th	Night	11% 7% 3 5% 5% 3 4 3 5% 7% 47%	1753
	21st to end	Night	10% 6% 3 6% 4 2 5% 4 6% 8% 46%	1620
May	1st to 10th	Night	12% 7% 2 5% 7% 4 4 5% 6% 7% 42%	1620
	11th to 20th	Night	11% 6% 3 7% 5% 3 6% 6% 7% 8% 37%	1592
	21st to end	Night	10% 7% 3 6% 7% 4 5% 6% 8% 9% 38%	1744
June	1st to 10th	Night	9% 6% 4 8% 6% 4 6% 5% 8% 10% 34%	1620
	11th to 20th	Night	5% 5% 2 4 6% 3 5% 7% 8% 12% 43%	1620
	21st to end	Night	7% 4 3 5% 6% 3 7% 6% 9% 10% 41%	1620
July	1st to 10th	Night	10% 7% 2 7% 7% 4 6% 8% 8% 11% 30%	1620
	11th to 20th	Night	8% 6% 3 6% 7% 5% 8% 8% 7% 12% 30%	1620
	21st to end	Night	7% 5% 3 7% 6% 4 7% 8% 8% 12% 33%	1771
August	1st to 10th	Night	11% 6% 3 7% 7% 4 6% 6% 8% 10% 32%	1611
	11th to 20th	Night	11% 5% 4 8% 7% 3 6% 6% 7% 8% 36%	1622
	21st to end	Night	12% 7% 3 6% 5% 4 6% 7% 8% 10% 33%	1980
September	1st to 10th	Night	9% 6% 3 8% 7% 4 7% 6% 7% 8% 36%	1980
	11th to 20th	Night	14% 7% 3 6% 6% 3 5% 6% 6% 8% 35%	1980
	21st to end	Night	12% 7% 2 5% 6% 3 5% 4 5% 7% 44%	1980
October	1st to 10th	Night	13% 7% 2 3 4 2 3 4 4 6% 51%	1980
	11th to 20th	Night	10% 8% 3 6% 5% 3 5% 3 3 6% 48%	2132
	21st to end	Night	11% 7% 2 5% 4 2 3 3 4 5% 52%	2376
November	1st to 10th	Night	10% 7% 2 5% 5% 3 4 3 4 6% 51%	2368
	11th to 20th	Night	12% 7% 3 5% 5% 3 4 4 4 5% 48%	2470
	21st to end	Night	12% 8% 3 5% 5% 3 5% 5% 6% 6% 42%	2470
December	1st to 10th	Night	16% 9% 4 8% 6% 3 4 5% 6% 6% 34%	2470
	11th to 20th	Night	12% 10% 4 7% 5% 3 4 3 4 6% 42%	3042
	21st to end	Night	16% 10% 5% 9% 7% 4 5% 5% 6% 7% 28%	4532

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	43% 4 8% 15% 23% 6%	2837
	11th to 20th	Day	43% 4 9% 12% 24% 7%	2840
	21st to end	Day	48% 3 7% 14% 21% 6%	3124
February	1st to 10th	Day	47% 5% 7% 17% 18% 6%	1879
	11th to 20th	Day	48% 5% 7% 16% 17% 6%	1858
	21st to end	Day	49% 5% 9% 12% 18% 7%	1520
March	1st to 10th	Day	40% 6% 9% 17% 21% 8%	1880
	11th to 20th	Day	50% 6% 10% 13% 15% 6%	1980
	21st to end	Day	48% 6% 12% 17% 14% 2	2178
April	1st to 10th	Day	39% 8% 11% 21% 18% 4	1987
	11th to 20th	Day	43% 6% 9% 17% 20% 5%	2161
	21st to end	Day	39% 7% 12% 24% 15% 2	2340
May	1st to 10th	Day	43% 8% 13% 20% 13% 3	2340
	11th to 20th	Day	51% 10% 11% 16% 10% 1	2305
	21st to end	Day	45% 11% 14% 19% 10% 1	2531
June	1st to 10th	Day	49% 12% 14% 19% 7%	2340
	11th to 20th	Day	44% 13% 16% 17% 10% 1	2340
	21st to end	Day	44% 14% 15% 16% 9% 2	2340
July	1st to 10th	Day	53% 14% 14% 14% 5% 1	2275
	11th to 20th	Day	53% 15% 15% 9% 6% 2	2271
	21st to end	Day	49% 15% 15% 15% 6% 1	2405
August	1st to 10th	Day	51% 14% 15% 15% 4	2314
	11th to 20th	Day	52% 12% 13% 13% 7% 1	2275
	21st to end	Day	54% 11% 13% 13% 8% 2	2358
September	1st to 10th	Day	47% 9% 11% 16% 13% 3	1980
	11th to 20th	Day	49% 10% 9% 16% 15% 2	1980
	21st to end	Day	43% 7% 11% 16% 17% 6%	1980
October	1st to 10th	Day	36% 7% 9% 17% 25% 5%	1980
	11th to 20th	Day	35% 6% 8% 20% 21% 10%	1828
	21st to end	Day	34% 4 7% 21% 24% 10%	1980
November	1st to 10th	Day	31% 5% 8% 15% 31% 10%	1708
	11th to 20th	Day	35% 5% 7% 18% 25% 10%	1710
	21st to end	Day	40% 4 7% 17% 25% 6%	1710
December	1st to 10th	Day	49% 6% 6% 16% 17% 6%	1710
	11th to 20th	Day	42% 5% 9% 12% 22% 11%	2150
	21st to end	Day	45% 5% 10% 18% 18% 3	3124
January	1st to 10th	Night	46% 4 8% 12% 22% 7%	4109
	11th to 20th	Night	43% 4 8% 11% 23% 10%	4120
	21st to end	Night	53% 3 8% 11% 18% 7%	4532
February	1st to 10th	Night	42% 6% 12% 16% 20% 5%	2299
	11th to 20th	Night	49% 5% 7% 17% 17% 5%	2219
	21st to end	Night	51% 7% 7% 15% 15% 5%	1831
March	1st to 10th	Night	42% 7% 9% 14% 20% 8%	2078
	11th to 20th	Night	45% 8% 12% 17% 14% 4	1980
	21st to end	Night	45% 8% 12% 19% 14% 2	2178
April	1st to 10th	Night	36% 7% 13% 20% 21% 3	1980
	11th to 20th	Night	38% 4 11% 21% 20% 5%	1753
	21st to end	Night	35% 8% 12% 29% 14% 1	1620
May	1st to 10th	Night	39% 10% 14% 23% 12% 2	1620
	11th to 20th	Night	41% 13% 17% 20% 10% 1	1593
	21st to end	Night	39% 12% 15% 24% 8% 1	1745
June	1st to 10th	Night	41% 13% 17% 20% 7% 1	1620
	11th to 20th	Night	30% 14% 24% 24% 7% 1	1620
	21st to end	Night	32% 15% 20% 20% 11% 3	1620
July	1st to 10th	Night	43% 15% 19% 16% 6% 1	1575
	11th to 20th	Night	42% 16% 24% 13% 5% 2	1566
	21st to end	Night	37% 18% 22% 17% 6% 1	1672
August	1st to 10th	Night	42% 17% 17% 19% 5%	1600
	11th to 20th	Night	42% 15% 15% 16% 11%	1622
	21st to end	Night	43% 12% 19% 18% 7% 2	1980
September	1st to 10th	Night	40% 12% 17% 16% 12% 3	1980
	11th to 20th	Night	43% 10% 15% 17% 15% 1	1980
	21st to end	Night	39% 8% 12% 18% 18% 5%	1980
October	1st to 10th	Night	34% 5% 12% 18% 26% 4	1980
	11th to 20th	Night	38% 6% 9% 21% 20% 7%	2132
	21st to end	Night	34% 5% 6% 20% 26% 9%	2376
November	1st to 10th	Night	34% 5% 8% 19% 24% 10%	2368
	11th to 20th	Night	39% 4 7% 17% 23% 11%	2470
	21st to end	Night	40% 5% 7% 19% 22% 6%	2470
December	1st to 10th	Night	49% 7% 9% 14% 15% 6%	2470
	11th to 20th	Night	43% 6% 8% 12% 24% 7%	3044
	21st to end	Night	51% 6% 11% 15% 14% 3	4532

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% 26% 31% 12% 1	270
	11th to 20th	Day	31% 28% 26% 13% 3	270
	21st to end	Day	30% 31% 27% 8% 3	297
February	1st to 10th	Day	30% 23% 34% 11% 2	270
	11th to 20th	Day	37% 31% 27% 4 1	270
	21st to end	Day	40% 31% 22% 6%	210
March	1st to 10th	Day	25% 21% 33% 14% 6%	320
	11th to 20th	Day	27% 22% 27% 17% 5% 1	420
	21st to end	Day	24% 23% 28% 17% 7% 1	462
April	1st to 10th	Day	25% 15% 29% 21% 10% 1	420
	11th to 20th	Day	22% 21% 24% 17% 13% 3	412
	21st to end	Day	21% 17% 25% 20% 13% 5%	420
May	1st to 10th	Day	14% 25% 27% 15% 13% 5%	423
	11th to 20th	Day	17% 9% 27% 24% 15% 9%	447
	21st to end	Day	14% 9% 22% 25% 16% 14%	485
June	1st to 10th	Day	13% 6% 24% 24% 19% 13%	450
	11th to 20th	Day	7% 6% 22% 25% 22% 18%	450
	21st to end	Day	9% 7% 27% 24% 18% 14%	450
July	1st to 10th	Day	10% 4 18% 25% 25% 17%	445
	11th to 20th	Day	8% 4 17% 27% 23% 21%	444
	21st to end	Day	8% 2 15% 24% 27% 23%	488
August	1st to 10th	Day	14% 4 20% 22% 21% 19%	446
	11th to 20th	Day	12% 4 15% 27% 26% 16%	439
	21st to end	Day	14% 3 15% 20% 29% 19%	495
September	1st to 10th	Day	13% 3 16% 22% 32% 14%	450
	11th to 20th	Day	14% 6% 16% 23% 28% 14%	450
	21st to end	Day	14% 7% 20% 27% 26% 7%	450
October	1st to 10th	Day	17% 8% 17% 28% 21% 8%	450
	11th to 20th	Day	16% 14% 25% 22% 19% 4	450
	21st to end	Day	18% 14% 24% 26% 15% 3	495
November	1st to 10th	Day	17% 14% 31% 25% 11% 2	306
	11th to 20th	Day	20% 23% 34% 19% 5%	270
	21st to end	Day	16% 21% 35% 18% 8% 1	270
December	1st to 10th	Day	30% 25% 29% 12% 4 1	270
	11th to 20th	Day	20% 24% 31% 19% 6% 1	270
	21st to end	Day	27% 22% 34% 12% 5% 1	297
January	1st to 10th	Night	24% 18% 29% 23% 6%	760
	11th to 20th	Night	22% 20% 28% 23% 6%	760
	21st to end	Night	22% 19% 33% 24% 3	836
February	1st to 10th	Night	18% 18% 29% 30% 4	760
	11th to 20th	Night	26% 19% 33% 20% 1	743
	21st to end	Night	27% 22% 29% 18% 4	611
March	1st to 10th	Night	17% 22% 30% 27% 4	720
	11th to 20th	Night	20% 18% 29% 23% 9% 1	720
	21st to end	Night	19% 18% 28% 26% 8%	792
April	1st to 10th	Night	18% 18% 26% 28% 10%	720
	11th to 20th	Night	19% 12% 24% 29% 15% 2	541
	21st to end	Night	13% 11% 23% 32% 18% 2	540
May	1st to 10th	Night	16% 10% 22% 30% 21% 2	540
	11th to 20th	Night	12% 6% 21% 30% 27% 4	531
	21st to end	Night	12% 2 12% 30% 34% 9%	584
June	1st to 10th	Night	9% 2 15% 32% 34% 8%	540
	11th to 20th	Night	5% 3 15% 28% 37% 12%	540
	21st to end	Night	7% 2 12% 30% 41% 7%	540
July	1st to 10th	Night	11% 1 10% 22% 45% 11%	525
	11th to 20th	Night	8% 2 8% 23% 43% 16%	522
	21st to end	Night	7% 1 9% 20% 47% 16%	591
August	1st to 10th	Night	11% 2 8% 24% 42% 13%	537
	11th to 20th	Night	12% 2 8% 26% 40% 12%	534
	21st to end	Night	12% 2 9% 22% 42% 13%	594
September	1st to 10th	Night	10% 3 12% 25% 39% 11%	720
	11th to 20th	Night	16% 3 12% 25% 37% 8%	720
	21st to end	Night	15% 4 14% 29% 34% 4	720
October	1st to 10th	Night	15% 8% 17% 25% 27% 8%	720
	11th to 20th	Night	15% 11% 20% 30% 21% 3	720
	21st to end	Night	16% 13% 20% 34% 16% 3	792
November	1st to 10th	Night	13% 10% 20% 32% 21% 4	740
	11th to 20th	Night	17% 14% 19% 33% 14% 2	760
	21st to end	Night	16% 14% 20% 34% 15% 1	760
December	1st to 10th	Night	22% 16% 23% 28% 9%	760
	11th to 20th	Night	18% 16% 26% 32% 8% 1	760
	21st to end	Night	22% 15% 27% 31% 6%	836

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