AVAC Kings Canyon Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the AVAC Kings Canyon Site clear sky chart from 2005-11-06 to 2025-08-05.

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	2 2 1 2 2 2 2 2 4 6% 75%	129354
	Night	2 2 1 2 2 2 3 3 4 7% 72%	127677
Transparency	Day	12% 2 4 16% 28% 37%	129073
	Night	14% 2 5% 18% 30% 31%	127472
Seeing	Day	6% 14% 32% 30% 14% 4	16516
	Night	4 9% 27% 37% 19% 3	26246

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	2 3 1 3 2 2 2 2 3 7% 72%	3639
	11th to 20th	Day	4 3 1 2 2 2 2 2 4 8% 68%	3987
	21st to end	Day	6% 5% 2 5% 4 4 3 3 6% 9% 54%	4808
February	1st to 10th	Day	4 5% 2 4 3 3 3 3 5% 6% 62%	2000
	11th to 20th	Day	4 4 1 3 3 3 3 3 6% 8% 63%	1950
	21st to end	Day	5% 5% 2 5% 3 3 3 2 6% 6% 59%	1650
March	1st to 10th	Day	4 4 2 5% 4 4 5% 4 7% 7% 53%	4518
	11th to 20th	Day	2 3 1 4 4 4 5% 4 6% 9% 58%	4723
	21st to end	Day	3 3 1 4 3 3 4 4 6% 11% 58%	5969
April	1st to 10th	Day	3 3 1 3 3 3 3 2 6% 8% 66%	2400
	11th to 20th	Day	2 2 1 2 2 2 2 3 5% 6% 72%	2369
	21st to end	Day	1 2 1 2 2 2 3 2 5% 9% 72%	2400
May	1st to 10th	Day	1 1 1 2 1 2 2 2 4 5% 79%	5568
	11th to 20th	Day	1 1 1 1 2 2 4 8% 79%	5841
	21st to end	Day	1 1 1 1 1 2 1 3 5% 85%	6423
June	1st to 10th	Day	1 1 2 2 2 2 2 4 6% 79%	2731
	11th to 20th	Day	1 1 1 1 1 2 3 5% 87%	2800
	21st to end	Day	1 1 1 1 1 1 1 1 2 89%	2800
July	1st to 10th	Day	1 1 1 1 2 93%	6319
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 88%	6320
	21st to end	Day	1 1 1 1 1 1 1 2 3 89%	6112
August	1st to 10th	Day	1 1 2 1 1 2 1 2 3 86%	3832
	11th to 20th	Day	1 1 1 1 1 1 2 92%	3724
	21st to end	Day	1 1 1 1 1 1 3 91%	4180
September	1st to 10th	Day	1 1 1 1 1 2 1 3 4 84%	2280
	11th to 20th	Day	1 1 1 1 1 1 2 4 88%	2162
	21st to end	Day	1 1 1 2 2 1 3 4 85%	2090
October	1st to 10th	Day	1 1 1 1 1 1 1 3 4 86%	3490
	11th to 20th	Day	1 1 1 1 1 2 1 3 5% 84%	3194
	21st to end	Day	1 1 1 3 2 3 3 3 5% 7% 73%	3394
November	1st to 10th	Day	2 1 2 3 2 3 2 4 6% 75%	1764
	11th to 20th	Day	2 2 1 3 2 2 3 2 5% 5% 72%	1800
	21st to end	Day	3 3 1 3 4 3 4 4 6% 7% 63%	1800
December	1st to 10th	Day	2 2 1 3 3 3 4 3 6% 7% 66%	2950
	11th to 20th	Day	6% 4 1 4 3 3 4 3 7% 7% 57%	3363
	21st to end	Day	7% 5% 1 5% 4 4 4 3 6% 9% 52%	4004
January	1st to 10th	Night	3 3 1 3 3 2 3 3 5% 7% 67%	6306
	11th to 20th	Night	2 2 1 3 3 3 3 3 4 7% 69%	5985
	21st to end	Night	5% 5% 2 4 3 3 3 3 6% 8% 56%	6178
February	1st to 10th	Night	4 4 1 3 3 3 4 3 5% 7% 62%	2400
	11th to 20th	Night	5% 2 1 3 3 3 3 3 5% 8% 64%	2338
	21st to end	Night	4 4 1 3 3 3 4 3 5% 7% 62%	1980
March	1st to 10th	Night	3 4 2 5% 4 5% 5% 5% 7% 10% 51%	5376
	11th to 20th	Night	2 3 1 4 4 4 5% 4 6% 8% 58%	5247
	21st to end	Night	3 3 1 4 2 3 4 3 6% 10% 61%	5006
April	1st to 10th	Night	3 3 2 3 3 2 4 3 5% 7% 66%	2000
	11th to 20th	Night	1 2 1 2 2 3 2 3 6% 7% 71%	1979
	21st to end	Night	1 2 1 1 1 2 3 3 7% 9% 71%	2000
May	1st to 10th	Night	1 1 2 2 2 3 2 5% 6% 76%	4422
	11th to 20th	Night	1 1 1 1 2 2 5% 9% 78%	4074
	21st to end	Night	1 1 1 1 1 1 3 6% 86%	4474
June	1st to 10th	Night	1 2 1 2 2 2 4 8% 79%	1662
	11th to 20th	Night	1 1 1 1 1 1 3 6% 86%	1600
	21st to end	Night	1 1 1 1 1 1 2 2 90%	1600
July	1st to 10th	Night	1 1 2 94%	3640
	11th to 20th	Night	1 1 1 1 1 2 3 90%	3640
	21st to end	Night	1 1 1 1 1 1 2 3 89%	4768
August	1st to 10th	Night	1 1 1 1 1 2 2 2 3 86%	3206
	11th to 20th	Night	1 1 1 2 3 92%	3126
	21st to end	Night	1 1 1 1 1 1 2 92%	3498
September	1st to 10th	Night	1 1 1 1 1 1 1 2 3 87%	1900
	11th to 20th	Night	1 1 1 1 1 3 4 87%	2016
	21st to end	Night	1 1 1 1 2 3 3 86%	2090
October	1st to 10th	Night	1 1 1 1 1 1 2 2 3 87%	3490
	11th to 20th	Night	1 1 1 1 1 2 1 3 5% 85%	3740
	21st to end	Night	1 1 1 2 2 2 2 2 4 5% 79%	4171
November	1st to 10th	Night	1 2 1 2 2 2 3 3 4 8% 73%	2535
	11th to 20th	Night	2 2 2 3 3 3 3 5% 6% 72%	2600
	21st to end	Night	3 3 2 3 2 3 3 4 6% 7% 63%	2600
December	1st to 10th	Night	3 3 1 2 3 2 2 3 5% 8% 68%	4240
	11th to 20th	Night	5% 4 2 4 3 3 4 4 7% 11% 55%	4838
	21st to end	Night	5% 3 1 5% 4 5% 5% 5% 8% 11% 47%	6952

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	15% 2 4 35% 30% 14%	3639
	11th to 20th	Day	18% 2 11% 17% 23% 30%	3987
	21st to end	Day	27% 3 6% 22% 21% 21%	4808
February	1st to 10th	Day	23% 4 5% 20% 28% 21%	2000
	11th to 20th	Day	20% 3 4 22% 35% 16%	1960
	21st to end	Day	26% 3 5% 21% 32% 14%	1650
March	1st to 10th	Day	27% 3 6% 21% 27% 16%	4518
	11th to 20th	Day	20% 4 9% 29% 27% 10%	4723
	21st to end	Day	21% 3 13% 30% 25% 8%	5969
April	1st to 10th	Day	18% 3 9% 26% 30% 14%	2400
	11th to 20th	Day	14% 2 8% 24% 34% 18%	2372
	21st to end	Day	12% 3 8% 25% 38% 15%	2400
May	1st to 10th	Day	8% 2 7% 20% 36% 27%	5568
	11th to 20th	Day	6% 2 4 18% 42% 27%	5844
	21st to end	Day	6% 1 2 18% 40% 34%	6424
June	1st to 10th	Day	9% 2 4 18% 33% 34%	2731
	11th to 20th	Day	4 1 3 13% 27% 51%	2800
	21st to end	Day	6% 1 1 4 22% 66%	2800
July	1st to 10th	Day	2 1 3 11% 83%	6251
	11th to 20th	Day	5% 1 1 5% 15% 73%	6245
	21st to end	Day	4 1 1 6% 30% 58%	5936
August	1st to 10th	Day	7% 1 1 6% 26% 59%	3819
	11th to 20th	Day	3 1 3 20% 72%	3760
	21st to end	Day	4 1 6% 22% 68%	4179
September	1st to 10th	Day	7% 2 1 6% 24% 60%	2280
	11th to 20th	Day	5% 1 1 10% 33% 50%	2162
	21st to end	Day	7% 2 1 8% 38% 44%	2090
October	1st to 10th	Day	7% 1 2 10% 20% 61%	3490
	11th to 20th	Day	6% 1 2 11% 39% 41%	3194
	21st to end	Day	12% 2 3 10% 35% 39%	3394
November	1st to 10th	Day	11% 3 4 19% 37% 27%	1764
	11th to 20th	Day	15% 2 5% 17% 33% 29%	1800
	21st to end	Day	20% 3 5% 18% 27% 26%	1800
December	1st to 10th	Day	17% 2 5% 19% 32% 25%	2950
	11th to 20th	Day	26% 2 5% 26% 33% 8%	3362
	21st to end	Day	29% 3 8% 26% 26% 7%	4004
January	1st to 10th	Night	17% 3 6% 27% 33% 14%	6306
	11th to 20th	Night	16% 3 8% 20% 26% 28%	5985
	21st to end	Night	25% 3 6% 18% 25% 23%	6178
February	1st to 10th	Night	22% 3 6% 20% 26% 24%	2400
	11th to 20th	Night	20% 2 6% 21% 30% 20%	2339
	21st to end	Night	22% 3 7% 23% 29% 17%	1980
March	1st to 10th	Night	24% 4 9% 22% 27% 14%	5376
	11th to 20th	Night	20% 5% 12% 32% 21% 10%	5247
	21st to end	Night	19% 3 14% 34% 24% 6%	5006
April	1st to 10th	Night	18% 3 9% 31% 25% 15%	2000
	11th to 20th	Night	13% 2 8% 28% 31% 17%	1979
	21st to end	Night	11% 3 8% 29% 38% 11%	2000
May	1st to 10th	Night	10% 2 7% 23% 38% 21%	4419
	11th to 20th	Night	6% 2 3 24% 45% 20%	4075
	21st to end	Night	4 1 4 22% 42% 28%	4474
June	1st to 10th	Night	8% 1 6% 23% 33% 29%	1662
	11th to 20th	Night	4 1 4 15% 29% 47%	1600
	21st to end	Night	4 1 1 5% 26% 62%	1600
July	1st to 10th	Night	2 1 3 14% 80%	3600
	11th to 20th	Night	4 1 1 6% 17% 71%	3592
	21st to end	Night	4 1 1 8% 40% 46%	4632
August	1st to 10th	Night	7% 1 1 6% 34% 51%	3196
	11th to 20th	Night	3 1 1 5% 23% 68%	3156
	21st to end	Night	3 1 1 6% 27% 63%	3498
September	1st to 10th	Night	7% 1 1 6% 30% 55%	1900
	11th to 20th	Night	4 1 1 11% 36% 46%	2016
	21st to end	Night	6% 1 1 10% 39% 44%	2090
October	1st to 10th	Night	7% 1 2 9% 17% 65%	3490
	11th to 20th	Night	6% 1 2 11% 42% 38%	3740
	21st to end	Night	10% 1 2 9% 34% 42%	4171
November	1st to 10th	Night	12% 2 4 18% 35% 28%	2535
	11th to 20th	Night	14% 2 4 15% 34% 31%	2600
	21st to end	Night	19% 3 6% 20% 26% 27%	2600
December	1st to 10th	Night	17% 1 4 14% 37% 28%	4240
	11th to 20th	Night	23% 3 11% 23% 30% 10%	4838
	21st to end	Night	28% 3 10% 29% 23% 6%	6952

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	10% 22% 36% 23% 11%	200
	11th to 20th	Day	13% 20% 36% 23% 7% 1	352
	21st to end	Day	13% 22% 33% 20% 11% 1	505
February	1st to 10th	Day	12% 22% 32% 24% 8% 2	500
	11th to 20th	Day	12% 25% 33% 20% 8% 2	495
	21st to end	Day	11% 22% 39% 21% 6% 1	414
March	1st to 10th	Day	14% 25% 35% 17% 8% 1	500
	11th to 20th	Day	11% 21% 35% 24% 7% 2	500
	21st to end	Day	15% 26% 34% 17% 7% 2	550
April	1st to 10th	Day	11% 20% 35% 21% 11% 3	500
	11th to 20th	Day	9% 27% 34% 19% 8% 3	492
	21st to end	Day	7% 25% 31% 21% 9% 6%	500
May	1st to 10th	Day	7% 17% 37% 24% 12% 3	503
	11th to 20th	Day	4 18% 40% 26% 9% 3	528
	21st to end	Day	5% 15% 36% 29% 12% 3	573
June	1st to 10th	Day	4 8% 35% 32% 16% 5%	530
	11th to 20th	Day	1 10% 37% 32% 17% 4	530
	21st to end	Day	2 6% 34% 36% 17% 5%	530
July	1st to 10th	Day	2 29% 45% 19% 3	526
	11th to 20th	Day	1 1 21% 42% 27% 7%	524
	21st to end	Day	2 19% 47% 25% 7%	575
August	1st to 10th	Day	1 3 27% 47% 15% 6%	504
	11th to 20th	Day	1 2 24% 47% 18% 7%	477
	21st to end	Day	1 2 27% 42% 21% 8%	539
September	1st to 10th	Day	1 3 30% 38% 21% 7%	490
	11th to 20th	Day	1 9% 36% 34% 17% 4	490
	21st to end	Day	1 10% 28% 38% 19% 4	490
October	1st to 10th	Day	3 12% 30% 32% 18% 6%	490
	11th to 20th	Day	4 10% 31% 34% 18% 4	490
	21st to end	Day	4 15% 31% 26% 20% 4	509
November	1st to 10th	Day	6% 13% 28% 30% 18% 5%	300
	11th to 20th	Day	7% 11% 31% 34% 14% 3	300
	21st to end	Day	9% 14% 31% 33% 11% 2	300
December	1st to 10th	Day	6% 13% 36% 30% 12% 3	300
	11th to 20th	Day	6% 17% 31% 31% 14% 1	290
	21st to end	Day	14% 25% 28% 25% 8% 1	220
January	1st to 10th	Night	9% 11% 29% 31% 16% 4	800
	11th to 20th	Night	7% 9% 31% 38% 13% 2	800
	21st to end	Night	10% 11% 31% 34% 13% 2	880
February	1st to 10th	Night	7% 14% 30% 30% 16% 4	800
	11th to 20th	Night	7% 13% 32% 30% 14% 4	784
	21st to end	Night	8% 10% 37% 32% 11% 2	660
March	1st to 10th	Night	8% 15% 33% 32% 11% 2	800
	11th to 20th	Night	6% 13% 32% 29% 16% 3	800
	21st to end	Night	8% 17% 34% 29% 11% 2	880
April	1st to 10th	Night	7% 16% 35% 28% 13% 2	800
	11th to 20th	Night	3 15% 39% 29% 12% 1	791
	21st to end	Night	4 17% 37% 27% 13% 2	800
May	1st to 10th	Night	2 14% 40% 32% 11% 1	740
	11th to 20th	Night	1 15% 35% 34% 14% 1	591
	21st to end	Night	3 12% 39% 34% 12% 1	650
June	1st to 10th	Night	6% 38% 46% 9%	462
	11th to 20th	Night	6% 30% 49% 14% 1	400
	21st to end	Night	1 2 27% 47% 23% 1	400
July	1st to 10th	Night	1 1 11% 59% 27% 1	390
	11th to 20th	Night	1 6% 57% 33% 2	388
	21st to end	Night	1 8% 53% 33% 5%	774
August	1st to 10th	Night	2 1 15% 48% 30% 3	772
	11th to 20th	Night	1 9% 46% 38% 5%	752
	21st to end	Night	1 11% 43% 38% 7%	836
September	1st to 10th	Night	2 1 12% 42% 37% 6%	760
	11th to 20th	Night	1 21% 45% 28% 5%	760
	21st to end	Night	1 5% 20% 42% 28% 6%	760
October	1st to 10th	Night	3 7% 23% 44% 22% 2	760
	11th to 20th	Night	1 6% 23% 41% 23% 5%	760
	21st to end	Night	2 7% 25% 36% 22% 8%	836
November	1st to 10th	Night	3 7% 26% 39% 20% 6%	780
	11th to 20th	Night	4 6% 26% 40% 20% 5%	800
	21st to end	Night	5% 8% 29% 36% 19% 4	800
December	1st to 10th	Night	8% 9% 30% 34% 17% 3	800
	11th to 20th	Night	9% 9% 28% 37% 17% 1	800
	21st to end	Night	9% 12% 31% 34% 12% 2	880

Page generated at 2025-08-01 22:32:25. Version ac07

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