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Kline-Dodge Dark Sky Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kline-Dodge Dark Sky Site clear sky chart from 2005-11-06 to 2025-11-03.

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	5% 5% 2 4 3 4 4 4 6% 8% 57%	135396
	Night	5% 6% 2 5% 4 4 4 4 6% 7% 54%	132075
Transparency	Day	25% 5% 10% 24% 25% 11%	130361
	Night	28% 5% 11% 24% 23% 9%	128117
Seeing	Day	8% 8% 26% 32% 20% 7%	16982
	Night	8% 6% 34% 40% 12% 1	26923

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 7% 3 8% 3 3 3 3 5% 7% 56%	3638
	11th to 20th	Day	2 5% 2 7% 4 4 5% 3 6% 7% 55%	3640
	21st to end	Day	3 6% 2 5% 4 3 4 3 4 6% 60%	4446
February	1st to 10th	Day	3 8% 3 7% 3 4 3 3 5% 7% 54%	1858
	11th to 20th	Day	2 6% 2 6% 4 5% 4 4 5% 6% 56%	1949
	21st to end	Day	3 7% 3 5% 4 3 4 3 4 5% 58%	1650
March	1st to 10th	Day	3 9% 3 4 2 3 3 3 4 6% 60%	4500
	11th to 20th	Day	6% 7% 2 5% 3 4 3 3 5% 7% 56%	4739
	21st to end	Day	4 6% 2 5% 3 4 4 4 6% 8% 53%	5942
April	1st to 10th	Day	6% 7% 2 4 3 3 4 4 6% 7% 53%	2400
	11th to 20th	Day	10% 8% 3 5% 4 4 4 4 5% 7% 47%	2371
	21st to end	Day	10% 7% 1 5% 3 4 3 5% 7% 7% 49%	2400
May	1st to 10th	Day	8% 6% 2 5% 4 4 4 4 5% 7% 52%	5898
	11th to 20th	Day	7% 5% 2 5% 3 4 4 3 6% 8% 52%	6068
	21st to end	Day	9% 4 2 4 3 4 4 4 6% 8% 51%	6925
June	1st to 10th	Day	6% 3 1 4 3 4 5% 4 8% 9% 53%	2800
	11th to 20th	Day	6% 3 1 4 3 4 4 4 5% 8% 57%	2800
	21st to end	Day	3 3 1 4 3 5% 5% 5% 8% 9% 56%	2800
July	1st to 10th	Day	4 2 1 4 3 4 4 4 5% 8% 61%	6339
	11th to 20th	Day	2 2 1 4 4 4 5% 4 8% 10% 56%	6340
	21st to end	Day	4 3 2 4 4 4 5% 5% 8% 10% 51%	6903
August	1st to 10th	Day	6% 2 1 4 3 4 5% 5% 7% 11% 51%	5705
	11th to 20th	Day	3 2 1 3 3 4 5% 4 7% 9% 59%	5366
	21st to end	Day	5% 4 2 5% 5% 5% 5% 4 7% 9% 49%	5984
September	1st to 10th	Day	4 3 1 3 3 3 3 3 5% 6% 65%	2400
	11th to 20th	Day	5% 2 1 3 3 2 4 3 6% 7% 63%	2320
	21st to end	Day	6% 3 1 3 2 3 2 2 4 6% 66%	2200
October	1st to 10th	Day	5% 3 2 2 1 2 2 2 3 78%	3440
	11th to 20th	Day	4 3 1 3 3 3 3 2 4 6% 66%	3250
	21st to end	Day	6% 6% 1 3 2 2 2 2 3 5% 67%	3304
November	1st to 10th	Day	3 4 2 4 2 2 3 3 4 7% 66%	1781
	11th to 20th	Day	3 5% 1 4 5% 3 3 3 5% 6% 63%	1800
	21st to end	Day	3 7% 2 4 2 3 2 3 4 6% 63%	1790
December	1st to 10th	Day	1 6% 2 5% 2 3 3 3 4 5% 66%	2620
	11th to 20th	Day	2 4 1 4 3 3 3 3 4 6% 66%	3026
	21st to end	Day	5% 8% 2 6% 4 4 4 3 5% 7% 53%	4004
January	1st to 10th	Night	3 9% 3 7% 4 4 4 3 5% 7% 52%	6327
	11th to 20th	Night	2 6% 2 7% 4 5% 5% 4 5% 7% 53%	6340
	21st to end	Night	3 5% 2 6% 4 4 4 3 5% 6% 59%	6563
February	1st to 10th	Night	3 8% 4 6% 4 3 4 3 4 7% 54%	2540
	11th to 20th	Night	3 8% 4 8% 5% 4 4 5% 5% 8% 47%	2338
	21st to end	Night	3 8% 2 6% 3 4 3 3 5% 6% 59%	1980
March	1st to 10th	Night	5% 9% 3 5% 3 3 3 2 4 5% 59%	5374
	11th to 20th	Night	7% 9% 2 5% 4 3 3 3 5% 6% 52%	5247
	21st to end	Night	8% 8% 2 5% 4 4 4 4 7% 8% 46%	4998
April	1st to 10th	Night	7% 8% 2 6% 4 4 4 4 5% 6% 50%	2000
	11th to 20th	Night	11% 8% 2 5% 4 4 4 4 5% 8% 45%	1977
	21st to end	Night	13% 8% 2 6% 4 4 4 4 5% 7% 44%	2000
May	1st to 10th	Night	11% 6% 2 6% 4 4 4 4 6% 6% 47%	4080
	11th to 20th	Night	8% 5% 2 5% 4 4 5% 4 6% 9% 47%	3844
	21st to end	Night	13% 6% 2 5% 4 4 4 4 5% 7% 46%	3972
June	1st to 10th	Night	6% 3 1 4 3 3 4 4 8% 11% 54%	1600
	11th to 20th	Night	7% 3 1 4 3 4 5% 3 7% 8% 56%	1600
	21st to end	Night	4 4 2 4 4 5% 5% 4 9% 10% 47%	1600
July	1st to 10th	Night	5% 3 1 5% 4 4 5% 4 7% 8% 52%	3640
	11th to 20th	Night	4 3 1 5% 4 5% 5% 5% 7% 10% 50%	3640
	21st to end	Night	4 4 2 6% 5% 5% 6% 6% 7% 9% 46%	3970
August	1st to 10th	Night	7% 4 2 6% 6% 6% 6% 5% 7% 9% 42%	4099
	11th to 20th	Night	5% 3 2 6% 5% 5% 6% 5% 8% 9% 47%	4483
	21st to end	Night	8% 5% 2 7% 4 4 5% 4 7% 9% 45%	4993
September	1st to 10th	Night	5% 4 1 3 2 4 4 4 6% 8% 58%	2000
	11th to 20th	Night	6% 3 1 4 4 3 3 4 7% 7% 58%	2078
	21st to end	Night	6% 3 2 4 3 3 4 2 4 6% 63%	2200
October	1st to 10th	Night	6% 3 1 3 2 2 2 2 4 5% 68%	3740
	11th to 20th	Night	7% 3 1 4 3 3 3 4 5% 7% 60%	3898
	21st to end	Night	5% 6% 2 3 2 2 3 2 3 5% 66%	4462
November	1st to 10th	Night	3 4 2 4 3 3 3 3 6% 8% 63%	2562
	11th to 20th	Night	3 6% 1 4 3 3 3 3 5% 6% 63%	2600
	21st to end	Night	5% 6% 2 5% 3 3 3 3 5% 6% 59%	2605
December	1st to 10th	Night	1 4 1 4 2 2 3 2 4 5% 70%	4570
	11th to 20th	Night	2 5% 2 5% 4 3 4 3 5% 8% 59%	5181
	21st to end	Night	6% 9% 3 6% 4 4 4 3 5% 6% 51%	6974

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	28% 4 8% 32% 19% 9%	3639
	11th to 20th	Day	27% 4 11% 21% 30% 7%	3640
	21st to end	Day	25% 4 9% 27% 25% 9%	4446
February	1st to 10th	Day	30% 4 11% 28% 20% 7%	1858
	11th to 20th	Day	28% 5% 9% 29% 24% 7%	1959
	21st to end	Day	27% 4 10% 22% 25% 13%	1650
March	1st to 10th	Day	25% 3 8% 17% 30% 17%	4500
	11th to 20th	Day	27% 4 9% 22% 31% 7%	4739
	21st to end	Day	26% 5% 13% 34% 19% 3	5942
April	1st to 10th	Day	27% 5% 13% 24% 22% 9%	2400
	11th to 20th	Day	34% 5% 12% 22% 19% 9%	2374
	21st to end	Day	31% 5% 12% 27% 21% 3	2400
May	1st to 10th	Day	31% 6% 11% 28% 19% 6%	5898
	11th to 20th	Day	28% 6% 10% 21% 24% 11%	6072
	21st to end	Day	28% 7% 14% 25% 20% 6%	6926
June	1st to 10th	Day	24% 8% 17% 25% 18% 9%	2800
	11th to 20th	Day	24% 6% 10% 21% 24% 15%	2800
	21st to end	Day	22% 6% 11% 23% 25% 13%	2800
July	1st to 10th	Day	20% 6% 8% 18% 30% 19%	6271
	11th to 20th	Day	21% 6% 14% 26% 23% 11%	6265
	21st to end	Day	26% 6% 14% 20% 17% 17%	6705
August	1st to 10th	Day	28% 7% 16% 27% 17% 6%	4151
	11th to 20th	Day	21% 7% 13% 21% 26% 12%	3882
	21st to end	Day	23% 6% 11% 21% 26% 13%	4311
September	1st to 10th	Day	20% 4 7% 24% 27% 17%	2400
	11th to 20th	Day	18% 5% 8% 21% 31% 17%	2320
	21st to end	Day	20% 3 7% 22% 35% 14%	2200
October	1st to 10th	Day	14% 2 5% 16% 34% 29%	3440
	11th to 20th	Day	20% 3 7% 27% 32% 11%	3250
	21st to end	Day	21% 2 5% 23% 37% 12%	3304
November	1st to 10th	Day	19% 3 8% 29% 25% 15%	1781
	11th to 20th	Day	22% 3 6% 25% 34% 10%	1800
	21st to end	Day	24% 3 7% 22% 30% 14%	1790
December	1st to 10th	Day	22% 3 6% 34% 25% 9%	2620
	11th to 20th	Day	20% 3 7% 32% 33% 5%	3024
	21st to end	Day	31% 3 7% 29% 22% 8%	4004
January	1st to 10th	Night	31% 4 8% 31% 21% 6%	6327
	11th to 20th	Night	28% 4 12% 21% 22% 12%	6340
	21st to end	Night	27% 4 9% 26% 23% 11%	6563
February	1st to 10th	Night	30% 4 11% 25% 23% 8%	2540
	11th to 20th	Night	34% 5% 10% 26% 18% 6%	2338
	21st to end	Night	26% 3 8% 24% 26% 13%	1980
March	1st to 10th	Night	28% 3 7% 15% 34% 13%	5374
	11th to 20th	Night	31% 5% 11% 13% 28% 12%	5247
	21st to end	Night	32% 8% 11% 31% 16% 2	4998
April	1st to 10th	Night	32% 5% 12% 22% 21% 8%	2000
	11th to 20th	Night	37% 5% 13% 21% 19% 7%	1977
	21st to end	Night	37% 7% 12% 24% 17% 4	2000
May	1st to 10th	Night	34% 8% 14% 29% 9% 5%	4080
	11th to 20th	Night	31% 8% 15% 25% 13% 8%	3845
	21st to end	Night	35% 9% 17% 24% 12% 4	3972
June	1st to 10th	Night	23% 8% 23% 26% 14% 6%	1600
	11th to 20th	Night	24% 7% 15% 23% 19% 12%	1600
	21st to end	Night	28% 8% 11% 25% 21% 7%	1600
July	1st to 10th	Night	28% 6% 11% 23% 26% 6%	3600
	11th to 20th	Night	28% 6% 19% 22% 20% 5%	3592
	21st to end	Night	32% 8% 14% 17% 21% 8%	3856
August	1st to 10th	Night	40% 8% 16% 21% 11% 3	2977
	11th to 20th	Night	33% 8% 15% 21% 16% 6%	3243
	21st to end	Night	24% 7% 13% 29% 20% 7%	3597
September	1st to 10th	Night	23% 5% 13% 22% 26% 13%	2000
	11th to 20th	Night	22% 6% 10% 24% 24% 14%	2078
	21st to end	Night	23% 4 8% 22% 29% 14%	2200
October	1st to 10th	Night	19% 3 6% 17% 33% 21%	3740
	11th to 20th	Night	23% 5% 7% 26% 30% 10%	3898
	21st to end	Night	22% 3 6% 25% 30% 13%	4462
November	1st to 10th	Night	20% 4 9% 25% 28% 15%	2562
	11th to 20th	Night	21% 3 8% 26% 30% 12%	2600
	21st to end	Night	26% 4 7% 23% 30% 11%	2605
December	1st to 10th	Night	18% 3 7% 33% 30% 9%	4570
	11th to 20th	Night	23% 3 6% 30% 32% 5%	5182
	21st to end	Night	33% 3 7% 26% 25% 6%	6974

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	5% 8% 25% 42% 16% 4	300
	11th to 20th	Day	8% 10% 27% 39% 14% 1	300
	21st to end	Day	6% 7% 35% 34% 15% 3	330
February	1st to 10th	Day	5% 13% 39% 34% 7% 2	300
	11th to 20th	Day	3 12% 37% 38% 9% 2	300
	21st to end	Day	5% 12% 42% 27% 12% 2	249
March	1st to 10th	Day	7% 11% 31% 28% 19% 5%	300
	11th to 20th	Day	8% 15% 32% 29% 13% 3	382
	21st to end	Day	13% 15% 33% 27% 11% 1	550
April	1st to 10th	Day	12% 16% 32% 25% 11% 3	500
	11th to 20th	Day	16% 21% 30% 22% 10% 2	492
	21st to end	Day	17% 14% 32% 22% 12% 3	500
May	1st to 10th	Day	14% 12% 30% 29% 12% 4	701
	11th to 20th	Day	14% 8% 27% 31% 15% 5%	725
	21st to end	Day	11% 10% 26% 29% 19% 5%	789
June	1st to 10th	Day	9% 5% 21% 31% 23% 11%	730
	11th to 20th	Day	5% 8% 26% 34% 22% 5%	730
	21st to end	Day	4 4 25% 38% 21% 8%	730
July	1st to 10th	Day	6% 4 16% 36% 28% 10%	721
	11th to 20th	Day	4 2 15% 33% 32% 13%	718
	21st to end	Day	5% 2 13% 35% 31% 13%	794
August	1st to 10th	Day	5% 2 16% 34% 31% 11%	572
	11th to 20th	Day	3 3 23% 32% 26% 14%	517
	21st to end	Day	4 2 23% 36% 26% 10%	583
September	1st to 10th	Day	5% 2 21% 34% 25% 13%	530
	11th to 20th	Day	5% 4 21% 33% 25% 12%	450
	21st to end	Day	9% 3 18% 27% 28% 15%	330
October	1st to 10th	Day	10% 5% 20% 25% 23% 17%	330
	11th to 20th	Day	3 11% 30% 30% 18% 8%	330
	21st to end	Day	10% 9% 26% 32% 17% 5%	363
November	1st to 10th	Day	6% 8% 29% 33% 19% 4	306
	11th to 20th	Day	6% 6% 30% 38% 16% 5%	300
	21st to end	Day	7% 9% 28% 36% 16% 4	300
December	1st to 10th	Day	7% 12% 28% 31% 19% 3	300
	11th to 20th	Day	9% 6% 32% 38% 14% 1	300
	21st to end	Day	7% 9% 35% 38% 11% 1	330
January	1st to 10th	Night	5% 5% 36% 41% 11% 2	1000
	11th to 20th	Night	6% 7% 36% 40% 10% 1	1000
	21st to end	Night	7% 5% 37% 40% 11% 1	923
February	1st to 10th	Night	6% 5% 47% 36% 5% 1	800
	11th to 20th	Night	6% 8% 43% 38% 6%	784
	21st to end	Night	5% 8% 43% 39% 4 1	660
March	1st to 10th	Night	6% 8% 38% 40% 7% 1	800
	11th to 20th	Night	11% 6% 40% 36% 7%	800
	21st to end	Night	11% 8% 40% 35% 7%	674
April	1st to 10th	Night	11% 10% 45% 30% 4	600
	11th to 20th	Night	16% 9% 37% 35% 4	593
	21st to end	Night	16% 8% 34% 35% 6% 1	600
May	1st to 10th	Night	15% 10% 31% 35% 10%	600
	11th to 20th	Night	14% 5% 32% 38% 11% 1	591
	21st to end	Night	12% 8% 36% 34% 10% 1	650
June	1st to 10th	Night	7% 4 29% 43% 16% 1	600
	11th to 20th	Night	7% 4 38% 40% 11%	600
	21st to end	Night	5% 3 29% 47% 16% 1	600
July	1st to 10th	Night	7% 3 28% 42% 18% 2	585
	11th to 20th	Night	4 1 21% 46% 26% 2	582
	21st to end	Night	6% 2 17% 47% 26% 2	657
August	1st to 10th	Night	7% 2 18% 50% 22% 1	597
	11th to 20th	Night	7% 1 28% 45% 18% 1	594
	21st to end	Night	6% 1 26% 50% 16% 2	660
September	1st to 10th	Night	8% 2 26% 47% 16% 2	600
	11th to 20th	Night	7% 2 29% 46% 15% 2	600
	21st to end	Night	6% 3 28% 46% 16% 1	600
October	1st to 10th	Night	12% 5% 31% 35% 15% 2	685
	11th to 20th	Night	7% 6% 31% 43% 13% 2	800
	21st to end	Night	10% 6% 30% 39% 14% 1	1002
November	1st to 10th	Night	5% 6% 34% 43% 11% 1	986
	11th to 20th	Night	5% 6% 39% 40% 9% 1	1000
	21st to end	Night	8% 8% 29% 41% 13% 1	1000
December	1st to 10th	Night	5% 5% 38% 41% 11% 1	1000
	11th to 20th	Night	6% 7% 38% 39% 10% 1	1000
	21st to end	Night	8% 9% 36% 39% 8%	1100

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