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 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	12% 8% 3 8% 5% 5% 5% 4 6% 7% 37%	113995
	Night	11% 8% 3 8% 5% 4 4 4 5% 7% 40%	114640
Transparency	Day	41% 8% 11% 18% 17% 6%	117789
	Night	39% 7% 12% 19% 17% 5%	118985
Seeing	Day	18% 14% 24% 21% 15% 8%	15502
	Night	16% 11% 21% 28% 20% 4	25634

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	12% 9% 4 7% 3 3 3 3 5% 5% 46%	4056
	11th to 20th	Day	9% 8% 4 9% 3 3 2 2 3 4 52%	4060
	21st to end	Day	15% 11% 5% 8% 3 3 3 2 3 6% 41%	4466
February	1st to 10th	Day	13% 10% 3 8% 5% 5% 3 4 5% 6% 38%	1978
	11th to 20th	Day	16% 10% 2 9% 5% 4 4 3 4 6% 36%	1948
	21st to end	Day	15% 10% 4 8% 5% 4 4 3 5% 6% 37%	1650
March	1st to 10th	Day	16% 9% 3 8% 5% 4 4 3 4 6% 38%	4700
	11th to 20th	Day	9% 7% 3 6% 4 3 3 2 5% 6% 51%	4980
	21st to end	Day	13% 10% 3 7% 4 4 4 3 4 5% 42%	5465
April	1st to 10th	Day	10% 8% 3 7% 5% 5% 5% 4 8% 6% 40%	2209
	11th to 20th	Day	13% 7% 2 7% 5% 4 5% 4 5% 6% 41%	2405
	21st to end	Day	12% 7% 2 7% 5% 5% 5% 4 5% 7% 42%	2535
May	1st to 10th	Day	12% 9% 3 9% 5% 5% 5% 4 6% 7% 33%	4082
	11th to 20th	Day	17% 10% 4 9% 5% 6% 5% 4 6% 6% 28%	4081
	21st to end	Day	9% 6% 3 7% 6% 6% 6% 5% 8% 10% 35%	4476
June	1st to 10th	Day	11% 8% 3 9% 8% 7% 6% 4 7% 8% 29%	2470
	11th to 20th	Day	6% 6% 3 9% 7% 6% 7% 6% 9% 9% 33%	2470
	21st to end	Day	9% 6% 3 8% 7% 7% 6% 6% 9% 9% 30%	2470
July	1st to 10th	Day	6% 7% 3 10% 8% 7% 8% 6% 8% 10% 25%	4120
	11th to 20th	Day	10% 7% 3 9% 8% 7% 8% 7% 8% 8% 26%	4120
	21st to end	Day	12% 11% 5% 13% 10% 9% 8% 6% 6% 6% 14%	4466
August	1st to 10th	Day	9% 7% 3 9% 7% 6% 8% 6% 8% 12% 26%	4104
	11th to 20th	Day	8% 6% 3 8% 6% 7% 7% 6% 9% 12% 30%	3988
	21st to end	Day	8% 6% 2 8% 6% 6% 7% 4 7% 8% 37%	4148
September	1st to 10th	Day	12% 7% 3 9% 7% 5% 6% 5% 7% 7% 32%	2090
	11th to 20th	Day	16% 8% 3 9% 6% 6% 5% 4 6% 7% 30%	2090
	21st to end	Day	15% 7% 2 7% 6% 5% 5% 3 5% 7% 37%	2090
October	1st to 10th	Day	12% 6% 2 6% 3 4 4 4 5% 7% 47%	2090
	11th to 20th	Day	10% 7% 2 5% 3 3 4 3 4 6% 52%	1929
	21st to end	Day	12% 6% 2 5% 3 3 4 2 3 6% 52%	2090
November	1st to 10th	Day	10% 6% 2 5% 4 4 3 4 4 5% 53%	1800
	11th to 20th	Day	12% 5% 3 5% 4 3 4 3 5% 7% 49%	1800
	21st to end	Day	12% 8% 2 7% 4 3 4 3 5% 7% 46%	1800
December	1st to 10th	Day	12% 8% 3 7% 4 3 3 3 4 6% 47%	2930
	11th to 20th	Day	12% 10% 4 10% 5% 5% 4 3 5% 5% 37%	3373
	21st to end	Day	13% 10% 4 7% 4 3 3 3 5% 7% 41%	4466
January	1st to 10th	Night	11% 10% 4 7% 4 3 4 2 4 6% 45%	5889
	11th to 20th	Night	9% 10% 3 8% 5% 4 3 3 3 4 48%	5900
	21st to end	Night	13% 12% 3 6% 4 4 3 3 4 5% 43%	6490
February	1st to 10th	Night	11% 8% 4 8% 5% 5% 5% 4 5% 6% 39%	2419
	11th to 20th	Night	15% 10% 4 8% 5% 4 4 3 4 4 37%	2338
	21st to end	Night	16% 9% 4 8% 5% 5% 4 3 5% 5% 35%	1980
March	1st to 10th	Night	15% 13% 4 9% 4 4 4 4 5% 5% 33%	5151
	11th to 20th	Night	9% 6% 3 6% 4 4 3 3 6% 8% 49%	4980
	21st to end	Night	11% 8% 4 8% 5% 5% 4 4 5% 6% 41%	5467
April	1st to 10th	Night	11% 8% 3 6% 5% 3 5% 4 6% 7% 43%	2200
	11th to 20th	Night	11% 8% 3 6% 5% 4 4 3 5% 6% 47%	1949
	21st to end	Night	10% 7% 2 7% 4 4 5% 3 6% 7% 45%	1761
May	1st to 10th	Night	11% 9% 3 10% 7% 5% 5% 4 6% 7% 34%	2813
	11th to 20th	Night	16% 9% 3 9% 4 4 5% 4 5% 7% 33%	2812
	21st to end	Night	8% 6% 3 7% 5% 5% 5% 5% 8% 10% 40%	3079
June	1st to 10th	Night	9% 6% 4 10% 5% 6% 6% 4 8% 10% 34%	1710
	11th to 20th	Night	4 5% 2 5% 5% 5% 5% 5% 8% 12% 43%	1710
	21st to end	Night	7% 5% 2 5% 5% 5% 7% 5% 9% 10% 40%	1710
July	1st to 10th	Night	8% 7% 3 10% 6% 6% 6% 5% 8% 11% 30%	2840
	11th to 20th	Night	7% 7% 3 7% 6% 6% 7% 6% 8% 11% 34%	2840
	21st to end	Night	11% 11% 4 12% 7% 6% 6% 5% 7% 9% 21%	3087
August	1st to 10th	Night	9% 6% 3 9% 6% 6% 6% 4 8% 12% 31%	2825
	11th to 20th	Night	11% 6% 3 8% 5% 5% 6% 5% 6% 8% 37%	2837
	21st to end	Night	7% 6% 3 5% 4 5% 5% 4 7% 9% 45%	3476
September	1st to 10th	Night	9% 7% 3 9% 6% 6% 6% 4 7% 8% 36%	2090
	11th to 20th	Night	15% 8% 3 7% 5% 4 5% 4 6% 8% 34%	2090
	21st to end	Night	13% 7% 2 7% 5% 4 4 3 5% 7% 42%	2090
October	1st to 10th	Night	13% 7% 2 5% 4 3 3 4 4 6% 51%	2090
	11th to 20th	Night	9% 8% 3 7% 4 4 4 2 3 5% 50%	2251
	21st to end	Night	11% 8% 2 6% 4 3 3 3 4 4 53%	2508
November	1st to 10th	Night	11% 7% 2 6% 5% 3 4 2 4 6% 50%	2496
	11th to 20th	Night	12% 7% 2 6% 5% 4 4 3 4 6% 48%	2600
	21st to end	Night	11% 8% 3 5% 5% 5% 4 3 6% 6% 43%	2600
December	1st to 10th	Night	11% 8% 3 8% 4 4 4 3 5% 5% 45%	4250
	11th to 20th	Night	12% 10% 5% 11% 5% 4 4 3 4 5% 37%	4822
	21st to end	Night	15% 10% 3 9% 5% 4 4 3 5% 6% 35%	6490

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% 4 6% 17% 29% 6%	4057
	11th to 20th	Day	36% 3 6% 12% 33% 9%	4060
	21st to end	Day	44% 3 9% 15% 20% 9%	4466
February	1st to 10th	Day	45% 5% 7% 19% 17% 6%	1978
	11th to 20th	Day	48% 5% 7% 17% 17% 6%	1958
	21st to end	Day	46% 5% 9% 13% 20% 7%	1650
March	1st to 10th	Day	43% 5% 6% 15% 21% 11%	4700
	11th to 20th	Day	34% 5% 6% 14% 24% 18%	4980
	21st to end	Day	42% 5% 8% 26% 14% 6%	5465
April	1st to 10th	Day	39% 8% 11% 21% 17% 4	2209
	11th to 20th	Day	41% 6% 9% 18% 21% 5%	2405
	21st to end	Day	40% 7% 12% 24% 15% 2	2535
May	1st to 10th	Day	47% 9% 12% 19% 11% 2	4120
	11th to 20th	Day	53% 9% 9% 19% 9% 1	4085
	21st to end	Day	40% 11% 14% 20% 15% 1	4489
June	1st to 10th	Day	48% 12% 14% 19% 6% 1	2470
	11th to 20th	Day	42% 12% 16% 18% 10% 1	2470
	21st to end	Day	43% 14% 16% 16% 10% 2	2470
July	1st to 10th	Day	43% 14% 19% 17% 6%	4055
	11th to 20th	Day	46% 14% 20% 15% 4 1	4051
	21st to end	Day	60% 15% 12% 9% 3	4324
August	1st to 10th	Day	43% 12% 17% 23% 5%	4091
	11th to 20th	Day	37% 10% 24% 15% 11% 3	4027
	21st to end	Day	38% 9% 14% 24% 14% 1	4148
September	1st to 10th	Day	46% 9% 11% 16% 14% 3	2090
	11th to 20th	Day	49% 9% 9% 16% 15% 2	2090
	21st to end	Day	44% 7% 12% 15% 16% 5%	2090
October	1st to 10th	Day	26% 7% 8% 17% 30% 12%	3480
	11th to 20th	Day	22% 4 5% 18% 24% 27%	3182
	21st to end	Day	27% 5% 8% 22% 24% 14%	3428
November	1st to 10th	Day	32% 5% 8% 16% 29% 10%	1800
	11th to 20th	Day	34% 5% 7% 19% 25% 10%	1800
	21st to end	Day	38% 5% 8% 18% 25% 6%	1800
December	1st to 10th	Day	34% 5% 8% 17% 27% 8%	2930
	11th to 20th	Day	42% 8% 10% 14% 18% 8%	3370
	21st to end	Day	40% 5% 12% 24% 16% 2	4466
January	1st to 10th	Night	39% 4 8% 16% 26% 7%	5889
	11th to 20th	Night	39% 4 7% 13% 28% 10%	5900
	21st to end	Night	41% 4 8% 16% 21% 10%	6490
February	1st to 10th	Night	42% 6% 12% 17% 19% 4	2419
	11th to 20th	Night	49% 5% 8% 16% 17% 5%	2339
	21st to end	Night	49% 6% 7% 16% 17% 5%	1980
March	1st to 10th	Night	47% 6% 7% 14% 21% 5%	5151
	11th to 20th	Night	29% 5% 8% 22% 21% 15%	4980
	21st to end	Night	40% 6% 10% 25% 13% 6%	5467
April	1st to 10th	Night	37% 7% 14% 20% 20% 3	2200
	11th to 20th	Night	37% 4 11% 22% 21% 5%	1949
	21st to end	Night	37% 8% 12% 28% 14% 1	1761
May	1st to 10th	Night	45% 11% 13% 21% 8% 1	2840
	11th to 20th	Night	49% 9% 14% 19% 9%	2813
	21st to end	Night	34% 13% 17% 25% 10% 1	3087
June	1st to 10th	Night	42% 13% 17% 19% 7% 1	1710
	11th to 20th	Night	30% 14% 24% 25% 7% 1	1710
	21st to end	Night	32% 15% 20% 20% 11% 3	1710
July	1st to 10th	Night	41% 15% 23% 17% 4	2795
	11th to 20th	Night	36% 17% 27% 16% 3 1	2786
	21st to end	Night	51% 17% 18% 10% 3	2988
August	1st to 10th	Night	39% 12% 26% 19% 4	2814
	11th to 20th	Night	37% 11% 24% 17% 11%	2864
	21st to end	Night	33% 10% 19% 29% 8% 1	3476
September	1st to 10th	Night	40% 12% 17% 16% 13% 3	2090
	11th to 20th	Night	45% 9% 15% 16% 14% 1	2090
	21st to end	Night	40% 8% 13% 18% 17% 5%	2090
October	1st to 10th	Night	24% 6% 12% 20% 30% 8%	3480
	11th to 20th	Night	22% 3 6% 21% 31% 16%	3737
	21st to end	Night	30% 4 7% 21% 28% 10%	4120
November	1st to 10th	Night	35% 6% 9% 19% 23% 9%	2496
	11th to 20th	Night	38% 4 7% 17% 23% 10%	2600
	21st to end	Night	39% 5% 8% 20% 22% 6%	2600
December	1st to 10th	Night	36% 7% 7% 19% 24% 6%	4250
	11th to 20th	Night	42% 8% 11% 15% 19% 5%	4824
	21st to end	Night	45% 5% 13% 20% 15% 2	6490

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	31% 26% 30% 11% 1	300
	11th to 20th	Day	32% 28% 26% 12% 3	300
	21st to end	Day	30% 31% 28% 8% 3	330
February	1st to 10th	Day	28% 23% 35% 11% 2	300
	11th to 20th	Day	40% 30% 25% 4 1	300
	21st to end	Day	39% 28% 26% 6%	249
March	1st to 10th	Day	30% 19% 30% 14% 6% 1	390
	11th to 20th	Day	28% 22% 27% 18% 5% 1	500
	21st to end	Day	24% 24% 29% 16% 6% 1	550
April	1st to 10th	Day	26% 17% 29% 19% 8% 1	500
	11th to 20th	Day	21% 22% 25% 18% 12% 2	492
	21st to end	Day	21% 17% 26% 20% 12% 4	480
May	1st to 10th	Day	15% 25% 26% 16% 12% 5%	463
	11th to 20th	Day	18% 10% 27% 23% 14% 8%	487
	21st to end	Day	13% 10% 24% 24% 16% 12%	529
June	1st to 10th	Day	13% 7% 25% 24% 18% 12%	490
	11th to 20th	Day	7% 5% 23% 26% 21% 17%	490
	21st to end	Day	9% 7% 27% 24% 18% 15%	490
July	1st to 10th	Day	10% 4 18% 26% 26% 17%	485
	11th to 20th	Day	8% 4 17% 27% 24% 20%	484
	21st to end	Day	8% 3 15% 25% 27% 21%	532
August	1st to 10th	Day	13% 4 20% 24% 21% 17%	486
	11th to 20th	Day	11% 5% 16% 28% 25% 15%	479
	21st to end	Day	13% 3 14% 20% 30% 20%	539
September	1st to 10th	Day	12% 3 16% 23% 31% 14%	490
	11th to 20th	Day	15% 6% 16% 23% 28% 13%	490
	21st to end	Day	16% 7% 20% 26% 25% 7%	490
October	1st to 10th	Day	16% 8% 18% 30% 21% 8%	490
	11th to 20th	Day	15% 15% 24% 23% 20% 4	490
	21st to end	Day	17% 13% 24% 27% 16% 3	539
November	1st to 10th	Day	17% 14% 30% 25% 11% 2	338
	11th to 20th	Day	19% 23% 34% 19% 5%	300
	21st to end	Day	18% 23% 33% 18% 7% 1	300
December	1st to 10th	Day	29% 26% 30% 11% 3 1	300
	11th to 20th	Day	21% 23% 31% 19% 5% 1	300
	21st to end	Day	28% 21% 33% 13% 5% 1	330
January	1st to 10th	Night	25% 17% 30% 22% 6%	800
	11th to 20th	Night	22% 20% 29% 23% 6%	800
	21st to end	Night	21% 19% 34% 24% 2	880
February	1st to 10th	Night	18% 19% 29% 30% 4	800
	11th to 20th	Night	26% 20% 33% 20% 1	783
	21st to end	Night	26% 22% 30% 19% 3	660
March	1st to 10th	Night	19% 21% 30% 26% 4	800
	11th to 20th	Night	20% 18% 29% 24% 8% 1	800
	21st to end	Night	19% 19% 29% 26% 8%	880
April	1st to 10th	Night	18% 20% 27% 26% 9%	800
	11th to 20th	Night	18% 12% 24% 30% 13% 2	601
	21st to end	Night	13% 11% 24% 32% 17% 2	587
May	1st to 10th	Night	16% 10% 21% 30% 21% 2	570
	11th to 20th	Night	13% 6% 20% 30% 26% 4	561
	21st to end	Night	12% 3 13% 31% 33% 9%	617
June	1st to 10th	Night	9% 2 16% 33% 33% 7%	570
	11th to 20th	Night	5% 3 14% 29% 37% 12%	570
	21st to end	Night	7% 3 12% 30% 41% 7%	570
July	1st to 10th	Night	10% 2 10% 23% 44% 11%	555
	11th to 20th	Night	8% 2 8% 22% 43% 16%	552
	21st to end	Night	8% 1 9% 22% 45% 15%	624
August	1st to 10th	Night	10% 2 7% 27% 41% 12%	567
	11th to 20th	Night	12% 2 9% 27% 39% 11%	564
	21st to end	Night	12% 2 8% 22% 42% 14%	627
September	1st to 10th	Night	10% 3 12% 26% 38% 11%	760
	11th to 20th	Night	17% 3 12% 25% 36% 7%	760
	21st to end	Night	16% 4 14% 29% 33% 4	760
October	1st to 10th	Night	15% 7% 16% 28% 26% 8%	760
	11th to 20th	Night	14% 11% 20% 31% 20% 3	760
	21st to end	Night	15% 12% 19% 35% 16% 3	836
November	1st to 10th	Night	13% 10% 20% 33% 20% 4	780
	11th to 20th	Night	17% 14% 21% 33% 14% 2	800
	21st to end	Night	17% 14% 21% 34% 14% 1	800
December	1st to 10th	Night	21% 16% 25% 28% 9%	800
	11th to 20th	Night	18% 16% 26% 32% 8% 1	800
	21st to end	Night	22% 15% 26% 31% 6%	880

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