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 2026-08-30.

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	11% 8% 3 8% 5% 5% 5% 4 6% 7% 36%	143498
	Night	11% 8% 3 8% 5% 5% 4 4 6% 7% 39%	138734
Transparency	Day	41% 8% 13% 18% 15% 5%	147248
	Night	38% 8% 14% 19% 16% 5%	143056
Seeing	Day	18% 14% 24% 21% 15% 8%	17343
	Night	16% 11% 21% 28% 20% 4	27327

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% 10% 4 7% 3 3 3 3 5% 5% 44%	5258
	11th to 20th	Day	7% 7% 4 8% 3 3 2 2 3 4 57%	5280
	21st to end	Day	15% 11% 5% 10% 4 3 3 2 3 6% 38%	5780
February	1st to 10th	Day	12% 9% 3 8% 5% 5% 4 4 5% 6% 39%	2077
	11th to 20th	Day	15% 10% 2 9% 5% 4 4 4 5% 6% 37%	2048
	21st to end	Day	14% 10% 4 8% 5% 4 4 3 5% 6% 37%	1730
March	1st to 10th	Day	16% 9% 3 8% 5% 4 4 3 4 6% 38%	4805
	11th to 20th	Day	9% 7% 3 6% 4 3 3 3 5% 6% 50%	5090
	21st to end	Day	13% 10% 3 7% 4 4 4 3 4 5% 42%	5586
April	1st to 10th	Day	10% 7% 3 7% 5% 5% 6% 4 8% 6% 39%	2319
	11th to 20th	Day	12% 6% 2 7% 5% 5% 4 4 5% 6% 43%	2527
	21st to end	Day	12% 7% 2 7% 5% 4 5% 4 5% 7% 42%	2730
May	1st to 10th	Day	12% 10% 4 9% 5% 5% 5% 5% 6% 8% 32%	7616
	11th to 20th	Day	13% 8% 3 9% 5% 6% 6% 5% 7% 7% 30%	7626
	21st to end	Day	11% 11% 4 11% 7% 6% 6% 4 6% 7% 25%	8391
June	1st to 10th	Day	11% 7% 3 9% 8% 6% 7% 5% 7% 8% 29%	2730
	11th to 20th	Day	6% 5% 3 9% 7% 7% 7% 7% 9% 9% 32%	2730
	21st to end	Day	8% 6% 3 8% 7% 7% 6% 7% 9% 10% 30%	2730
July	1st to 10th	Day	4 5% 3 9% 7% 7% 9% 7% 9% 11% 28%	7680
	11th to 20th	Day	8% 7% 3 10% 9% 8% 9% 8% 9% 9% 19%	7680
	21st to end	Day	9% 8% 4 11% 8% 8% 8% 6% 8% 9% 20%	8340
August	1st to 10th	Day	10% 7% 3 9% 7% 6% 8% 7% 7% 11% 25%	4364
	11th to 20th	Day	8% 6% 3 8% 6% 6% 7% 6% 9% 12% 30%	4244
	21st to end	Day	8% 6% 2 8% 6% 7% 7% 4 7% 8% 37%	4387
September	1st to 10th	Day	12% 7% 3 9% 7% 6% 6% 5% 7% 7% 32%	2200
	11th to 20th	Day	15% 8% 3 9% 6% 6% 5% 5% 6% 8% 31%	2200
	21st to end	Day	15% 7% 2 7% 6% 5% 5% 4 6% 7% 36%	2200
October	1st to 10th	Day	12% 6% 2 6% 3 4 5% 4 5% 7% 47%	2200
	11th to 20th	Day	10% 7% 2 5% 3 3 4 3 4 6% 53%	2030
	21st to end	Day	12% 6% 2 5% 3 3 4 2 4 6% 52%	2200
November	1st to 10th	Day	10% 6% 2 5% 4 4 3 3 4 5% 53%	1892
	11th to 20th	Day	12% 5% 3 5% 4 3 4 3 5% 7% 49%	1890
	21st to end	Day	11% 9% 2 7% 4 3 4 3 5% 7% 46%	1890
December	1st to 10th	Day	12% 8% 3 7% 4 3 4 3 5% 5% 46%	3020
	11th to 20th	Day	12% 10% 4 10% 5% 5% 4 3 5% 5% 38%	3463
	21st to end	Day	12% 10% 4 7% 4 3 3 3 5% 7% 41%	4565
January	1st to 10th	Night	12% 10% 3 6% 4 4 4 2 5% 6% 44%	7635
	11th to 20th	Night	8% 9% 3 8% 5% 3 3 3 3 4 51%	7680
	21st to end	Night	13% 13% 3 7% 4 4 4 3 4 4 41%	8401
February	1st to 10th	Night	10% 8% 3 8% 5% 5% 4 4 5% 6% 40%	2540
	11th to 20th	Night	15% 10% 4 9% 5% 4 4 3 4 5% 37%	2458
	21st to end	Night	15% 9% 4 9% 5% 5% 5% 3 5% 5% 34%	2076
March	1st to 10th	Night	15% 13% 4 9% 4 5% 4 4 5% 5% 33%	5266
	11th to 20th	Night	9% 6% 3 6% 4 4 3 3 6% 8% 49%	5090
	21st to end	Night	11% 7% 4 8% 5% 5% 4 4 5% 6% 41%	5588
April	1st to 10th	Night	10% 7% 3 6% 5% 3 5% 4 6% 7% 43%	2310
	11th to 20th	Night	10% 7% 2 6% 4 4 3 2 5% 6% 48%	2047
	21st to end	Night	10% 7% 3 7% 4 3 5% 3 6% 7% 45%	1890
May	1st to 10th	Night	10% 8% 3 10% 7% 6% 6% 5% 7% 7% 31%	5237
	11th to 20th	Night	15% 8% 3 9% 5% 5% 5% 4 5% 7% 33%	5234
	21st to end	Night	14% 10% 4 10% 6% 5% 5% 4 6% 7% 28%	5761
June	1st to 10th	Night	8% 7% 4 10% 5% 5% 6% 4 8% 9% 34%	1890
	11th to 20th	Night	5% 5% 2 6% 5% 5% 5% 5% 8% 12% 41%	1890
	21st to end	Night	7% 5% 2 5% 5% 4 6% 5% 9% 10% 41%	1890
July	1st to 10th	Night	5% 5% 2 9% 6% 7% 6% 5% 8% 12% 35%	5278
	11th to 20th	Night	8% 7% 3 9% 7% 6% 7% 5% 8% 11% 29%	5277
	21st to end	Night	10% 10% 4 11% 6% 5% 5% 5% 7% 10% 28%	5736
August	1st to 10th	Night	9% 7% 3 9% 6% 6% 6% 4 8% 12% 30%	3005
	11th to 20th	Night	11% 6% 3 8% 5% 5% 5% 5% 6% 9% 37%	3020
	21st to end	Night	7% 6% 3 5% 4 5% 5% 4 7% 9% 44%	3676
September	1st to 10th	Night	9% 7% 3 9% 6% 6% 6% 4 7% 8% 35%	2200
	11th to 20th	Night	14% 7% 3 7% 5% 4 5% 5% 6% 8% 35%	2200
	21st to end	Night	13% 8% 2 7% 5% 4 4 3 5% 7% 41%	2200
October	1st to 10th	Night	13% 7% 2 5% 4 3 4 4 4 5% 50%	2200
	11th to 20th	Night	9% 7% 2 6% 4 5% 4 2 3 5% 51%	2370
	21st to end	Night	11% 8% 2 6% 4 3 3 3 4 4 52%	2640
November	1st to 10th	Night	10% 7% 2 6% 5% 3 4 2 4 6% 50%	2624
	11th to 20th	Night	11% 7% 2 6% 5% 5% 4 3 4 5% 48%	2730
	21st to end	Night	11% 8% 3 5% 5% 5% 4 3 6% 6% 43%	2730
December	1st to 10th	Night	11% 8% 3 8% 4 4 4 4 5% 5% 45%	4380
	11th to 20th	Night	12% 10% 5% 11% 5% 4 4 3 4 5% 37%	4952
	21st to end	Night	14% 10% 4 9% 5% 4 4 3 5% 6% 35%	6633

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	38% 4 9% 21% 23% 5%	5259
	11th to 20th	Day	32% 3 5% 10% 36% 14%	5280
	21st to end	Day	46% 3 8% 15% 17% 11%	5780
February	1st to 10th	Day	44% 5% 7% 20% 18% 6%	2077
	11th to 20th	Day	48% 5% 7% 17% 17% 6%	2058
	21st to end	Day	45% 5% 9% 13% 21% 6%	1730
March	1st to 10th	Day	43% 5% 6% 15% 21% 11%	4805
	11th to 20th	Day	34% 5% 6% 14% 24% 18%	5090
	21st to end	Day	42% 5% 8% 26% 14% 6%	5586
April	1st to 10th	Day	38% 8% 12% 21% 17% 4	2319
	11th to 20th	Day	39% 6% 10% 19% 21% 5%	2527
	21st to end	Day	39% 7% 12% 25% 15% 2	2730
May	1st to 10th	Day	44% 8% 15% 22% 11% 1	7651
	11th to 20th	Day	44% 9% 18% 20% 9% 1	7630
	21st to end	Day	49% 11% 12% 15% 11% 2	8405
June	1st to 10th	Day	47% 11% 14% 19% 7% 1	2730
	11th to 20th	Day	41% 12% 18% 18% 10% 1	2730
	21st to end	Day	42% 13% 17% 17% 10% 2	2730
July	1st to 10th	Day	37% 14% 24% 18% 6%	7615
	11th to 20th	Day	46% 16% 25% 11% 2	7611
	21st to end	Day	49% 13% 19% 13% 6% 1	8156
August	1st to 10th	Day	44% 12% 17% 22% 5%	4351
	11th to 20th	Day	37% 10% 24% 16% 10% 3	4283
	21st to end	Day	37% 9% 14% 24% 14% 1	4387
September	1st to 10th	Day	45% 9% 12% 16% 14% 3	2200
	11th to 20th	Day	48% 10% 10% 17% 15% 1	2200
	21st to end	Day	44% 7% 13% 15% 16% 5%	2200
October	1st to 10th	Day	26% 7% 8% 17% 30% 12%	3590
	11th to 20th	Day	22% 4 5% 18% 25% 26%	3283
	21st to end	Day	28% 5% 8% 22% 24% 13%	3538
November	1st to 10th	Day	31% 5% 8% 16% 29% 10%	1892
	11th to 20th	Day	33% 5% 8% 20% 25% 10%	1890
	21st to end	Day	38% 4 8% 18% 25% 6%	1890
December	1st to 10th	Day	34% 6% 8% 18% 26% 8%	3020
	11th to 20th	Day	41% 8% 10% 14% 19% 8%	3460
	21st to end	Day	40% 5% 12% 25% 16% 2	4565
January	1st to 10th	Night	38% 4 14% 19% 20% 5%	7636
	11th to 20th	Night	35% 4 7% 15% 29% 11%	7680
	21st to end	Night	43% 5% 8% 16% 18% 10%	8401
February	1st to 10th	Night	41% 6% 12% 18% 20% 4	2540
	11th to 20th	Night	49% 5% 8% 17% 17% 4	2459
	21st to end	Night	49% 6% 7% 16% 17% 5%	2076
March	1st to 10th	Night	46% 6% 8% 14% 21% 5%	5266
	11th to 20th	Night	29% 5% 8% 22% 21% 14%	5090
	21st to end	Night	39% 6% 11% 25% 13% 6%	5588
April	1st to 10th	Night	36% 7% 15% 20% 19% 3	2310
	11th to 20th	Night	36% 4 11% 24% 21% 5%	2047
	21st to end	Night	36% 8% 13% 28% 14% 1	1890
May	1st to 10th	Night	41% 10% 18% 22% 8% 1	5264
	11th to 20th	Night	43% 9% 19% 20% 10%	5235
	21st to end	Night	45% 13% 17% 17% 7% 1	5771
June	1st to 10th	Night	41% 13% 17% 20% 8% 1	1890
	11th to 20th	Night	30% 14% 23% 25% 8% 1	1890
	21st to end	Night	31% 15% 20% 21% 11% 2	1890
July	1st to 10th	Night	33% 15% 30% 19% 3	5235
	11th to 20th	Night	39% 17% 29% 12% 1	5226
	21st to end	Night	43% 14% 23% 13% 5% 2	5606
August	1st to 10th	Night	40% 12% 26% 18% 4	2994
	11th to 20th	Night	37% 11% 24% 17% 11%	3047
	21st to end	Night	32% 10% 20% 29% 8% 1	3676
September	1st to 10th	Night	41% 12% 16% 16% 12% 3	2200
	11th to 20th	Night	43% 10% 16% 17% 14% 1	2200
	21st to end	Night	40% 8% 14% 18% 16% 5%	2200
October	1st to 10th	Night	25% 7% 12% 20% 29% 8%	3590
	11th to 20th	Night	22% 4 6% 22% 31% 16%	3856
	21st to end	Night	30% 4 7% 21% 28% 10%	4252
November	1st to 10th	Night	34% 5% 9% 20% 23% 9%	2624
	11th to 20th	Night	36% 4 8% 18% 24% 10%	2730
	21st to end	Night	39% 5% 8% 21% 22% 6%	2730
December	1st to 10th	Night	36% 8% 7% 19% 24% 6%	4380
	11th to 20th	Night	41% 8% 11% 14% 20% 5%	4954
	21st to end	Night	44% 5% 14% 21% 15% 2	6633

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% 11% 1	330
	11th to 20th	Day	32% 28% 26% 12% 2	330
	21st to end	Day	31% 31% 27% 9% 2	363
February	1st to 10th	Day	27% 24% 37% 11% 2	330
	11th to 20th	Day	38% 30% 26% 5% 1	330
	21st to end	Day	37% 28% 27% 7% 1	273
March	1st to 10th	Day	28% 19% 32% 16% 5%	425
	11th to 20th	Day	28% 22% 28% 17% 4 1	540
	21st to end	Day	23% 23% 30% 17% 6% 1	594
April	1st to 10th	Day	24% 16% 29% 19% 9% 2	540
	11th to 20th	Day	21% 22% 25% 18% 12% 2	532
	21st to end	Day	20% 16% 27% 20% 12% 4	540
May	1st to 10th	Day	15% 26% 27% 17% 11% 4	543
	11th to 20th	Day	17% 11% 28% 23% 14% 7%	567
	21st to end	Day	15% 11% 25% 24% 14% 11%	617
June	1st to 10th	Day	12% 8% 25% 24% 19% 12%	570
	11th to 20th	Day	6% 6% 24% 28% 21% 16%	570
	21st to end	Day	8% 7% 26% 24% 20% 16%	570
July	1st to 10th	Day	8% 4 17% 27% 26% 18%	565
	11th to 20th	Day	8% 4 15% 28% 25% 21%	564
	21st to end	Day	8% 3 16% 26% 27% 20%	620
August	1st to 10th	Day	14% 4 19% 26% 19% 17%	566
	11th to 20th	Day	10% 5% 15% 29% 25% 16%	559
	21st to end	Day	11% 4 15% 21% 30% 18%	619
September	1st to 10th	Day	12% 3 16% 25% 31% 13%	530
	11th to 20th	Day	14% 6% 16% 23% 28% 13%	530
	21st to end	Day	15% 6% 20% 26% 26% 6%	530
October	1st to 10th	Day	15% 7% 18% 29% 23% 8%	530
	11th to 20th	Day	14% 14% 24% 25% 19% 4	530
	21st to end	Day	19% 14% 25% 25% 15% 3	583
November	1st to 10th	Day	17% 15% 31% 24% 11% 2	370
	11th to 20th	Day	18% 24% 34% 19% 5%	330
	21st to end	Day	19% 23% 32% 18% 7% 1	330
December	1st to 10th	Day	29% 25% 31% 11% 3 1	330
	11th to 20th	Day	22% 22% 32% 19% 5% 1	330
	21st to end	Day	26% 22% 34% 12% 5% 1	363
January	1st to 10th	Night	25% 17% 30% 23% 5%	840
	11th to 20th	Night	22% 20% 30% 22% 6%	840
	21st to end	Night	21% 20% 34% 23% 2	924
February	1st to 10th	Night	18% 19% 29% 30% 4	840
	11th to 20th	Night	25% 20% 34% 19% 1	823
	21st to end	Night	26% 22% 30% 18% 3	692
March	1st to 10th	Night	18% 21% 30% 27% 4	840
	11th to 20th	Night	20% 18% 29% 25% 7% 1	840
	21st to end	Night	18% 18% 29% 27% 7%	924
April	1st to 10th	Night	17% 19% 26% 27% 10%	840
	11th to 20th	Night	18% 12% 24% 30% 14% 2	631
	21st to end	Night	13% 10% 24% 33% 18% 2	630
May	1st to 10th	Night	15% 10% 22% 32% 19% 2	630
	11th to 20th	Night	13% 7% 20% 32% 25% 3	621
	21st to end	Night	14% 4 13% 31% 30% 8%	683
June	1st to 10th	Night	9% 2 17% 33% 33% 7%	630
	11th to 20th	Night	5% 3 14% 31% 36% 11%	630
	21st to end	Night	7% 3 11% 30% 42% 7%	630
July	1st to 10th	Night	9% 2 9% 22% 46% 12%	615
	11th to 20th	Night	8% 2 8% 22% 44% 16%	612
	21st to end	Night	8% 2 9% 22% 45% 14%	690
August	1st to 10th	Night	11% 4 7% 26% 40% 11%	627
	11th to 20th	Night	12% 3 8% 26% 41% 11%	624
	21st to end	Night	11% 2 9% 25% 40% 13%	687
September	1st to 10th	Night	10% 4 12% 27% 37% 10%	800
	11th to 20th	Night	16% 4 12% 25% 37% 7%	800
	21st to end	Night	16% 4 14% 30% 32% 4	800
October	1st to 10th	Night	15% 7% 16% 28% 27% 7%	800
	11th to 20th	Night	14% 11% 19% 32% 20% 3	800
	21st to end	Night	16% 13% 20% 34% 15% 3	880
November	1st to 10th	Night	13% 10% 22% 33% 19% 4	820
	11th to 20th	Night	17% 14% 22% 33% 13% 2	840
	21st to end	Night	16% 15% 21% 33% 14% 1	840
December	1st to 10th	Night	21% 16% 27% 27% 9%	840
	11th to 20th	Night	18% 15% 26% 32% 7% 1	840
	21st to end	Night	21% 15% 27% 31% 6%	924

Page generated at 2026-08-27 04:07:09. Version ac07

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