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 2024-10-25.

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	12% 8% 3 8% 6% 5% 5% 4 6% 7% 36%	100939
	Night	12% 9% 3 7% 5% 5% 5% 4 6% 7% 38%	97828
Transparency	Day	44% 8% 12% 17% 15% 4	100752
	Night	42% 8% 13% 17% 15% 4	97685
Seeing	Day	18% 14% 24% 21% 16% 8%	14896
	Night	16% 11% 21% 28% 20% 4	24919

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	13% 9% 4 7% 3 4 4 4 6% 6% 38%	2836
	11th to 20th	Day	12% 9% 3 9% 4 4 3 3 4 5% 43%	2840
	21st to end	Day	20% 11% 4 6% 3 3 2 2 3 5% 40%	3124
February	1st to 10th	Day	13% 10% 3 8% 5% 5% 3 4 5% 6% 38%	1879
	11th to 20th	Day	15% 10% 2 9% 5% 4 4 3 5% 6% 37%	1848
	21st to end	Day	16% 10% 4 8% 5% 4 4 3 5% 6% 35%	1570
March	1st to 10th	Day	20% 10% 3 5% 4 3 3 3 4 6% 38%	3270
	11th to 20th	Day	12% 7% 3 6% 4 4 4 2 5% 5% 49%	3480
	21st to end	Day	16% 10% 3 8% 5% 5% 4 3 5% 5% 38%	3815
April	1st to 10th	Day	10% 8% 3 7% 5% 5% 5% 4 7% 6% 40%	2098
	11th to 20th	Day	14% 7% 2 7% 6% 5% 4 4 5% 6% 40%	2283
	21st to end	Day	12% 7% 2 7% 5% 4 5% 4 5% 7% 43%	2470
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 4 6% 53%	2027
November	1st to 10th	Day	10% 5% 2 5% 4 3 3 3 4 5% 54%	1708
	11th to 20th	Day	12% 5% 3 5% 4 3 4 3 5% 7% 49%	1710
	21st to end	Day	13% 8% 2 7% 4 3 3 3 5% 6% 45%	1710
December	1st to 10th	Day	17% 10% 4 8% 5% 3 4 4 5% 6% 35%	1710
	11th to 20th	Day	14% 7% 3 7% 5% 5% 4 3 4 6% 43%	2153
	21st to end	Day	15% 8% 4 8% 5% 4 3 4 5% 6% 37%	3124
January	1st to 10th	Night	13% 12% 5% 7% 4 4 4 3 5% 6% 38%	4109
	11th to 20th	Night	10% 11% 3 8% 5% 4 3 3 4 5% 43%	4120
	21st to end	Night	18% 15% 3 7% 5% 3 3 2 3 4 36%	4532
February	1st to 10th	Night	11% 8% 3 8% 5% 5% 5% 5% 5% 6% 40%	2299
	11th to 20th	Night	15% 10% 4 8% 6% 4 4 3 4 4 37%	2218
	21st to end	Night	16% 9% 5% 9% 5% 5% 5% 3 5% 5% 33%	1884
March	1st to 10th	Night	17% 17% 4 9% 5% 5% 4 4 5% 5% 28%	3581
	11th to 20th	Night	10% 8% 3 6% 4 4 4 3 6% 8% 46%	3480
	21st to end	Night	15% 7% 3 7% 5% 5% 4 4 6% 5% 39%	3817
April	1st to 10th	Night	11% 7% 2 5% 5% 3 5% 4 6% 7% 43%	2090
	11th to 20th	Night	11% 8% 3 6% 4 4 4 2 5% 6% 46%	1851
	21st to end	Night	10% 6% 2 7% 4 4 5% 3 6% 7% 46%	1710
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% 7% 2 5% 4 3 3 3 5% 4 54%	2435
November	1st to 10th	Night	10% 7% 2 6% 4 3 4 2 4 6% 51%	2368
	11th to 20th	Night	12% 7% 2 5% 5% 5% 4 3 4 5% 48%	2470
	21st to end	Night	11% 9% 3 5% 5% 5% 5% 3 6% 6% 42%	2470
December	1st to 10th	Night	16% 10% 4 9% 5% 4 4 4 6% 6% 34%	2470
	11th to 20th	Night	11% 11% 4 8% 4 4 3 2 4 6% 42%	3042
	21st to end	Night	15% 10% 4 10% 6% 5% 5% 4 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	48% 5% 9% 13% 18% 7%	1570
March	1st to 10th	Day	47% 5% 7% 16% 16% 9%	3270
	11th to 20th	Day	38% 5% 7% 15% 24% 11%	3480
	21st to end	Day	47% 5% 9% 21% 14% 4	3815
April	1st to 10th	Day	39% 8% 11% 20% 18% 4	2098
	11th to 20th	Day	43% 6% 9% 17% 21% 5%	2283
	21st to end	Day	39% 7% 12% 24% 15% 2	2470
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	35% 7% 9% 17% 26% 6%	2090
	11th to 20th	Day	33% 6% 8% 20% 22% 12%	1929
	21st to end	Day	33% 4 7% 20% 25% 10%	2027
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% 14% 16% 5%	1884
March	1st to 10th	Night	56% 7% 9% 10% 13% 5%	3581
	11th to 20th	Night	34% 6% 10% 22% 19% 9%	3480
	21st to end	Night	44% 7% 9% 20% 13% 6%	3817
April	1st to 10th	Night	37% 7% 14% 19% 20% 3	2090
	11th to 20th	Night	39% 4 11% 21% 20% 5%	1851
	21st to end	Night	36% 8% 13% 28% 14% 1	1710
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	33% 6% 12% 18% 26% 5%	2090
	11th to 20th	Night	36% 5% 9% 21% 21% 8%	2251
	21st to end	Night	33% 5% 6% 20% 27% 9%	2435
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	42% 29% 23% 6%	225
March	1st to 10th	Day	28% 20% 31% 14% 6% 1	355
	11th to 20th	Day	27% 23% 28% 17% 5% 1	460
	21st to end	Day	24% 24% 28% 16% 7% 1	506
April	1st to 10th	Day	27% 16% 28% 19% 9% 1	460
	11th to 20th	Day	22% 22% 24% 17% 12% 2	452
	21st to end	Day	21% 17% 26% 20% 12% 4	460
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	18% 13% 24% 27% 16% 3	514
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	628
March	1st to 10th	Night	19% 21% 30% 26% 5%	760
	11th to 20th	Night	20% 18% 29% 24% 8% 1	760
	21st to end	Night	19% 18% 28% 26% 8%	836
April	1st to 10th	Night	18% 19% 27% 27% 9%	760
	11th to 20th	Night	19% 12% 24% 29% 14% 2	571
	21st to end	Night	13% 11% 24% 32% 18% 2	570
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% 34% 16% 3	812
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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