State Camp
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the State Camp clear sky chart from 2005-11-06 to 2025-12-03.

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	16% 10% 4 9% 5% 5% 5% 4 5% 7% 31%	127190
	Night	16% 10% 4 9% 5% 5% 5% 4 5% 6% 32%	123489
Transparency	Day	49% 7% 12% 20% 11% 1	130784
	Night	48% 8% 12% 19% 11% 1	127981
Seeing	Day	24% 16% 27% 19% 11% 3	16096
	Night	22% 14% 25% 26% 11% 1	25519

By Month

Percentage Cloud Cover NE (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% 16% 6% 14% 5% 5% 4 4 4 4 24%	3597
	11th to 20th	Day	10% 16% 9% 22% 8% 6% 4 3 3 4 14%	3953
	21st to end	Day	19% 13% 8% 11% 5% 4 5% 3 4 5% 23%	4466
February	1st to 10th	Day	16% 15% 6% 11% 7% 5% 4 3 5% 5% 24%	1800
	11th to 20th	Day	14% 13% 6% 10% 7% 5% 4 4 5% 6% 27%	1753
	21st to end	Day	19% 13% 3 9% 7% 4 3 3 5% 5% 28%	1628
March	1st to 10th	Day	18% 12% 5% 8% 5% 4 3 3 4 5% 34%	4878
	11th to 20th	Day	13% 11% 4 9% 5% 5% 4 3 4 6% 35%	4980
	21st to end	Day	14% 10% 3 9% 6% 5% 5% 3 4 5% 35%	5525
April	1st to 10th	Day	17% 13% 4 9% 5% 4 4 3 5% 6% 31%	2400
	11th to 20th	Day	17% 11% 3 6% 5% 4 5% 5% 5% 5% 34%	2374
	21st to end	Day	20% 9% 2 7% 5% 4 4 3 5% 5% 35%	2485
May	1st to 10th	Day	26% 8% 3 8% 5% 4 5% 4 5% 6% 26%	5888
	11th to 20th	Day	24% 9% 3 7% 5% 4 4 4 5% 7% 27%	6306
	21st to end	Day	19% 7% 2 7% 5% 5% 6% 5% 6% 7% 31%	6949
June	1st to 10th	Day	15% 7% 3 7% 6% 6% 5% 4 6% 7% 35%	2800
	11th to 20th	Day	16% 7% 3 7% 6% 4 5% 4 6% 8% 34%	2800
	21st to end	Day	13% 6% 3 5% 6% 4 6% 4 6% 10% 36%	2800
July	1st to 10th	Day	7% 6% 3 8% 6% 6% 6% 5% 7% 8% 39%	6360
	11th to 20th	Day	7% 8% 3 9% 6% 6% 6% 5% 8% 10% 31%	6360
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 4 7% 7% 41%	6437
August	1st to 10th	Day	19% 7% 2 7% 5% 5% 5% 4 6% 9% 31%	4234
	11th to 20th	Day	14% 7% 3 8% 5% 6% 6% 5% 7% 8% 31%	4141
	21st to end	Day	15% 6% 2 5% 4 4 5% 4 7% 10% 39%	4312
September	1st to 10th	Day	17% 6% 2 6% 5% 4 5% 3 4 6% 43%	2400
	11th to 20th	Day	14% 5% 2 5% 5% 3 4 3 4 7% 46%	2395
	21st to end	Day	24% 7% 3 5% 4 4 4 3 5% 6% 34%	2089
October	1st to 10th	Day	15% 8% 3 7% 4 3 4 4 6% 8% 38%	2000
	11th to 20th	Day	19% 8% 3 7% 5% 4 5% 4 5% 6% 33%	2000
	21st to end	Day	19% 9% 3 7% 5% 5% 5% 4 5% 6% 32%	2200
November	1st to 10th	Day	11% 8% 4 8% 5% 4 4 3 5% 6% 41%	1911
	11th to 20th	Day	15% 14% 4 9% 6% 5% 4 4 6% 6% 28%	1727
	21st to end	Day	18% 16% 3 9% 6% 4 4 3 4 6% 26%	1680
December	1st to 10th	Day	16% 15% 7% 15% 8% 6% 5% 3 4 4 17%	2616
	11th to 20th	Day	21% 16% 5% 8% 4 4 4 3 4 5% 25%	2986
	21st to end	Day	21% 17% 5% 12% 6% 5% 4 3 4 5% 16%	3960
January	1st to 10th	Night	12% 14% 5% 17% 6% 5% 5% 4 5% 6% 21%	6349
	11th to 20th	Night	13% 13% 5% 19% 7% 5% 5% 4 5% 7% 18%	5928
	21st to end	Night	18% 11% 5% 12% 7% 6% 7% 4 4 4 22%	6490
February	1st to 10th	Night	16% 12% 5% 10% 6% 5% 5% 3 5% 6% 27%	2600
	11th to 20th	Night	16% 11% 5% 9% 6% 5% 5% 5% 5% 6% 28%	2533
	21st to end	Night	18% 11% 4 10% 6% 5% 5% 3 5% 6% 29%	2000
March	1st to 10th	Night	18% 12% 5% 8% 5% 5% 4 3 4 5% 31%	4960
	11th to 20th	Night	11% 11% 5% 7% 5% 4 4 3 5% 6% 38%	4979
	21st to end	Night	14% 10% 3 9% 5% 5% 4 3 5% 5% 37%	5406
April	1st to 10th	Night	19% 14% 3 7% 5% 3 4 3 4 7% 30%	2000
	11th to 20th	Night	17% 10% 3 6% 5% 5% 4 3 5% 6% 36%	1975
	21st to end	Night	19% 7% 2 6% 4 5% 5% 4 5% 7% 36%	1932
May	1st to 10th	Night	30% 9% 3 6% 5% 4 4 3 4 5% 27%	4053
	11th to 20th	Night	25% 9% 3 7% 5% 4 4 3 4 5% 31%	3585
	21st to end	Night	20% 8% 2 7% 5% 4 4 4 6% 7% 33%	3926
June	1st to 10th	Night	15% 7% 2 5% 4 5% 4 3 5% 8% 42%	1600
	11th to 20th	Night	13% 7% 2 6% 4 5% 4 4 5% 9% 40%	1600
	21st to end	Night	12% 6% 3 5% 5% 4 5% 4 8% 8% 41%	1600
July	1st to 10th	Night	9% 8% 3 7% 5% 5% 4 4 7% 9% 39%	3600
	11th to 20th	Night	8% 8% 3 8% 5% 6% 6% 4 7% 9% 36%	3600
	21st to end	Night	10% 5% 2 7% 4 4 5% 3 5% 8% 46%	4397
August	1st to 10th	Night	18% 6% 2 5% 5% 4 5% 4 6% 8% 36%	2915
	11th to 20th	Night	17% 7% 3 7% 3 4 4 4 5% 6% 40%	2875
	21st to end	Night	15% 5% 2 5% 3 4 4 4 5% 7% 46%	3585
September	1st to 10th	Night	16% 5% 3 6% 4 3 4 3 5% 6% 46%	2000
	11th to 20th	Night	14% 5% 2 4 3 3 3 2 5% 7% 51%	2001
	21st to end	Night	22% 6% 3 6% 5% 4 4 3 6% 6% 37%	2310
October	1st to 10th	Night	18% 6% 2 6% 4 4 3 3 5% 6% 44%	2400
	11th to 20th	Night	18% 8% 2 6% 3 4 4 4 4 7% 40%	2400
	21st to end	Night	21% 9% 3 6% 4 3 4 3 5% 8% 35%	2640
November	1st to 10th	Night	11% 8% 2 7% 4 3 4 4 5% 7% 45%	2607
	11th to 20th	Night	18% 11% 4 8% 5% 5% 4 4 5% 6% 30%	2890
	21st to end	Night	16% 13% 5% 9% 5% 4 4 3 6% 7% 28%	2940
December	1st to 10th	Night	14% 14% 6% 11% 6% 5% 6% 6% 7% 6% 19%	4609
	11th to 20th	Night	22% 12% 5% 9% 5% 5% 4 3 4 5% 27%	5208
	21st to end	Night	21% 15% 6% 11% 6% 5% 4 3 5% 5% 20%	6996

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	58% 8% 12% 15% 7% 2	3598
	11th to 20th	Day	72% 7% 7% 10% 4 1	3987
	21st to end	Day	61% 6% 10% 16% 7% 1	4466
February	1st to 10th	Day	62% 5% 11% 14% 7% 1	1800
	11th to 20th	Day	57% 6% 10% 20% 8% 1	1762
	21st to end	Day	57% 5% 9% 19% 8% 2	1628
March	1st to 10th	Day	50% 7% 11% 19% 10% 3	4881
	11th to 20th	Day	47% 8% 16% 18% 8% 4	4980
	21st to end	Day	47% 8% 9% 18% 15% 3	5525
April	1st to 10th	Day	54% 5% 10% 19% 11% 2	2400
	11th to 20th	Day	47% 7% 12% 17% 14% 2	2374
	21st to end	Day	49% 6% 9% 20% 14% 3	2485
May	1st to 10th	Day	56% 7% 10% 16% 9% 2	5897
	11th to 20th	Day	53% 9% 10% 18% 9% 1	6310
	21st to end	Day	46% 9% 12% 21% 10% 2	6949
June	1st to 10th	Day	46% 7% 13% 20% 13% 2	2800
	11th to 20th	Day	45% 8% 14% 19% 12% 1	2800
	21st to end	Day	40% 8% 15% 24% 13%	2800
July	1st to 10th	Day	40% 7% 14% 25% 12% 1	6290
	11th to 20th	Day	42% 10% 16% 21% 11%	6285
	21st to end	Day	38% 7% 12% 25% 17%	6252
August	1st to 10th	Day	48% 8% 15% 20% 9%	4221
	11th to 20th	Day	46% 8% 13% 25% 7%	4180
	21st to end	Day	38% 6% 13% 30% 11% 2	4312
September	1st to 10th	Day	43% 5% 10% 25% 15% 2	2400
	11th to 20th	Day	37% 6% 11% 25% 19% 1	2395
	21st to end	Day	50% 5% 12% 17% 15% 1	2089
October	1st to 10th	Day	39% 7% 11% 24% 16% 3	3260
	11th to 20th	Day	41% 7% 10% 22% 17% 3	3240
	21st to end	Day	36% 6% 15% 28% 14% 1	3538
November	1st to 10th	Day	42% 6% 13% 23% 14% 3	1911
	11th to 20th	Day	54% 7% 12% 18% 7% 2	1727
	21st to end	Day	56% 6% 12% 18% 7% 1	1680
December	1st to 10th	Day	64% 10% 9% 13% 4	2616
	11th to 20th	Day	60% 5% 12% 16% 7%	2986
	21st to end	Day	68% 7% 11% 9% 4 1	3960
January	1st to 10th	Night	56% 10% 11% 15% 7% 1	6349
	11th to 20th	Night	58% 10% 13% 10% 6% 2	5969
	21st to end	Night	60% 7% 10% 12% 9% 1	6490
February	1st to 10th	Night	55% 7% 13% 18% 7%	2600
	11th to 20th	Night	54% 7% 12% 19% 9%	2535
	21st to end	Night	56% 5% 10% 17% 11% 1	2000
March	1st to 10th	Night	53% 6% 12% 18% 10% 2	4970
	11th to 20th	Night	43% 7% 18% 21% 7% 4	4980
	21st to end	Night	45% 7% 9% 18% 18% 2	5406
April	1st to 10th	Night	53% 5% 9% 17% 13% 1	2000
	11th to 20th	Night	46% 8% 11% 20% 13% 2	1975
	21st to end	Night	45% 7% 12% 21% 14% 2	1932
May	1st to 10th	Night	58% 6% 8% 16% 9% 3	4060
	11th to 20th	Night	50% 11% 12% 15% 11% 1	3586
	21st to end	Night	45% 10% 11% 19% 12% 3	3927
June	1st to 10th	Night	39% 8% 12% 24% 15% 1	1600
	11th to 20th	Night	39% 8% 14% 23% 14% 2	1600
	21st to end	Night	37% 9% 14% 26% 14% 1	1600
July	1st to 10th	Night	38% 8% 13% 24% 15% 1	3560
	11th to 20th	Night	39% 10% 16% 22% 12% 1	3552
	21st to end	Night	34% 7% 13% 23% 22% 1	4267
August	1st to 10th	Night	43% 10% 14% 23% 9% 1	2904
	11th to 20th	Night	41% 8% 12% 27% 12%	2902
	21st to end	Night	36% 7% 12% 33% 12% 2	3585
September	1st to 10th	Night	38% 6% 11% 26% 17% 3	2000
	11th to 20th	Night	32% 5% 13% 28% 19% 1	2001
	21st to end	Night	46% 6% 12% 20% 15% 1	2310
October	1st to 10th	Night	39% 6% 11% 23% 20% 1	3920
	11th to 20th	Night	35% 7% 11% 24% 18% 5%	3899
	21st to end	Night	35% 6% 16% 26% 16% 2	4252
November	1st to 10th	Night	37% 6% 15% 23% 17% 2	2607
	11th to 20th	Night	51% 7% 12% 19% 10% 2	2890
	21st to end	Night	53% 7% 14% 20% 6% 1	2940
December	1st to 10th	Night	54% 10% 14% 18% 3	4609
	11th to 20th	Night	58% 6% 13% 18% 6%	5208
	21st to end	Night	62% 8% 10% 14% 5%	6996

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	36% 23% 30% 7% 5% 1	200
	11th to 20th	Day	38% 26% 25% 10% 1	284
	21st to end	Day	31% 32% 25% 9% 2 1	330
February	1st to 10th	Day	34% 30% 26% 9% 1	300
	11th to 20th	Day	41% 25% 30% 4	300
	21st to end	Day	39% 22% 26% 12% 2	392
March	1st to 10th	Day	32% 21% 29% 15% 3	500
	11th to 20th	Day	31% 24% 26% 14% 3 1	500
	21st to end	Day	32% 23% 27% 12% 5% 1	550
April	1st to 10th	Day	34% 24% 23% 14% 5% 1	500
	11th to 20th	Day	30% 24% 21% 13% 8% 3	492
	21st to end	Day	28% 18% 33% 13% 8% 1	500
May	1st to 10th	Day	31% 20% 24% 14% 9% 3	503
	11th to 20th	Day	26% 16% 27% 19% 8% 4	527
	21st to end	Day	22% 12% 27% 20% 15% 4	573
June	1st to 10th	Day	17% 15% 30% 23% 12% 3	530
	11th to 20th	Day	21% 15% 24% 25% 13% 2	530
	21st to end	Day	16% 12% 33% 25% 11% 3	530
July	1st to 10th	Day	11% 8% 29% 28% 16% 7%	525
	11th to 20th	Day	6% 10% 30% 30% 17% 6%	524
	21st to end	Day	13% 7% 32% 26% 16% 5%	576
August	1st to 10th	Day	11% 7% 27% 28% 20% 7%	526
	11th to 20th	Day	14% 8% 25% 29% 16% 8%	519
	21st to end	Day	17% 8% 26% 22% 15% 11%	583
September	1st to 10th	Day	18% 12% 20% 24% 18% 8%	530
	11th to 20th	Day	15% 6% 21% 24% 25% 9%	530
	21st to end	Day	30% 10% 23% 19% 15% 4	530
October	1st to 10th	Day	22% 12% 22% 21% 19% 5%	530
	11th to 20th	Day	25% 17% 30% 18% 8% 2	530
	21st to end	Day	27% 18% 28% 19% 8% 1	583
November	1st to 10th	Day	23% 19% 26% 19% 12% 2	458
	11th to 20th	Day	28% 24% 28% 13% 7%	267
	21st to end	Day	33% 25% 31% 9% 3	220
December	1st to 10th	Day	35% 26% 25% 9% 4 1	204
	11th to 20th	Day	39% 19% 28% 13% 2	200
	21st to end	Day	41% 15% 30% 10% 4	220
January	1st to 10th	Night	26% 23% 33% 15% 3	800
	11th to 20th	Night	28% 21% 29% 19% 3	800
	21st to end	Night	26% 23% 30% 19% 2	880
February	1st to 10th	Night	27% 21% 30% 20% 2	800
	11th to 20th	Night	30% 23% 32% 14% 1	783
	21st to end	Night	30% 20% 29% 18% 2	660
March	1st to 10th	Night	27% 20% 30% 20% 3	800
	11th to 20th	Night	27% 21% 27% 21% 5% 1	800
	21st to end	Night	23% 20% 32% 19% 5% 1	880
April	1st to 10th	Night	29% 19% 27% 19% 5%	800
	11th to 20th	Night	24% 16% 28% 24% 7% 1	791
	21st to end	Night	23% 14% 26% 30% 7%	732
May	1st to 10th	Night	25% 10% 22% 30% 12%	600
	11th to 20th	Night	19% 11% 24% 38% 9%	404
	21st to end	Night	16% 7% 23% 32% 21% 1	433
June	1st to 10th	Night	15% 8% 20% 41% 16% 1	400
	11th to 20th	Night	15% 7% 23% 40% 16%	400
	21st to end	Night	12% 4 27% 40% 18%	400
July	1st to 10th	Night	14% 5% 18% 39% 21% 2	390
	11th to 20th	Night	7% 3 20% 42% 27% 1	388
	21st to end	Night	11% 4 19% 40% 25% 2	639
August	1st to 10th	Night	11% 3 15% 41% 27% 2	597
	11th to 20th	Night	13% 7% 12% 37% 27% 4	594
	21st to end	Night	14% 4 18% 35% 28% 2	879
September	1st to 10th	Night	17% 6% 20% 31% 23% 3	800
	11th to 20th	Night	15% 4 18% 28% 30% 5%	800
	21st to end	Night	23% 9% 17% 29% 19% 3	800
October	1st to 10th	Night	20% 9% 20% 27% 20% 4	800
	11th to 20th	Night	23% 14% 24% 29% 10% 1	800
	21st to end	Night	25% 16% 25% 28% 6%	880
November	1st to 10th	Night	18% 13% 28% 31% 10%	820
	11th to 20th	Night	28% 17% 24% 24% 5% 2	840
	21st to end	Night	26% 19% 26% 24% 4	840
December	1st to 10th	Night	28% 21% 31% 16% 5%	809
	11th to 20th	Night	29% 17% 28% 22% 4	800
	21st to end	Night	27% 18% 29% 25% 2	880

Page generated at 2025-11-30 01:00:52. Version ac07

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