Kansas State University
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kansas State University clear sky chart from 2005-11-06 to 2026-01-17.

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	10% 6% 2 6% 4 4 4 3 5% 7% 48%	127265
	Night	10% 6% 2 6% 3 3 4 3 5% 6% 51%	124634
Transparency	Day	35% 5% 11% 26% 20% 4	130929
	Night	33% 4 11% 26% 21% 4	129033
Seeing	Day	13% 10% 31% 28% 14% 3	17270
	Night	13% 9% 33% 34% 11% 1	27227

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% 8% 3 10% 4 5% 4 3 5% 8% 37%	4167
	11th to 20th	Day	7% 10% 4 10% 5% 6% 4 3 4 6% 41%	4134
	21st to end	Day	9% 11% 5% 8% 4 4 3 3 3 5% 45%	4488
February	1st to 10th	Day	11% 12% 3 8% 4 4 3 3 5% 6% 41%	1800
	11th to 20th	Day	9% 10% 3 6% 3 5% 5% 3 6% 7% 43%	1863
	21st to end	Day	8% 8% 2 7% 3 4 4 3 5% 8% 48%	1650
March	1st to 10th	Day	11% 7% 2 5% 3 3 3 2 3 6% 55%	4867
	11th to 20th	Day	11% 6% 1 4 3 3 3 3 5% 6% 55%	4980
	21st to end	Day	11% 8% 4 7% 4 4 5% 4 6% 6% 41%	5462
April	1st to 10th	Day	13% 7% 3 6% 4 3 3 3 5% 7% 48%	2212
	11th to 20th	Day	12% 7% 2 6% 4 5% 4 4 5% 7% 44%	2477
	21st to end	Day	18% 7% 3 5% 5% 4 5% 3 4 6% 40%	2600
May	1st to 10th	Day	14% 8% 2 6% 3 4 3 3 4 5% 46%	5862
	11th to 20th	Day	12% 5% 2 5% 4 3 4 3 5% 6% 51%	5862
	21st to end	Day	18% 6% 2 5% 4 4 4 4 6% 7% 39%	6434
June	1st to 10th	Day	6% 4 2 5% 4 4 4 4 5% 9% 54%	2600
	11th to 20th	Day	7% 5% 2 4 4 4 4 4 6% 9% 51%	2600
	21st to end	Day	6% 3 2 5% 4 4 5% 4 7% 9% 52%	2600
July	1st to 10th	Day	8% 5% 2 5% 4 4 4 4 6% 9% 48%	5900
	11th to 20th	Day	8% 4 2 6% 4 5% 5% 4 7% 9% 46%	5900
	21st to end	Day	7% 4 2 5% 4 4 5% 5% 7% 9% 49%	6422
August	1st to 10th	Day	7% 4 2 6% 4 4 5% 3 6% 8% 53%	4234
	11th to 20th	Day	12% 5% 2 5% 4 4 4 3 5% 7% 49%	4171
	21st to end	Day	6% 3 1 5% 3 3 4 4 6% 8% 56%	4581
September	1st to 10th	Day	11% 4 2 4 3 3 3 4 5% 6% 56%	2251
	11th to 20th	Day	9% 5% 2 5% 4 4 4 3 5% 7% 52%	2200
	21st to end	Day	9% 5% 2 4 3 3 3 4 5% 6% 56%	2200
October	1st to 10th	Day	12% 5% 2 4 3 2 3 2 5% 6% 56%	2081
	11th to 20th	Day	10% 5% 2 4 3 3 3 3 3 5% 61%	2000
	21st to end	Day	14% 6% 2 5% 4 4 3 2 4 5% 52%	2200
November	1st to 10th	Day	8% 4 2 4 3 4 3 3 5% 6% 59%	1909
	11th to 20th	Day	10% 6% 2 5% 4 3 3 3 4 5% 56%	1890
	21st to end	Day	13% 7% 2 4 3 3 3 2 4 6% 51%	1890
December	1st to 10th	Day	6% 4 2 5% 3 3 5% 3 5% 7% 58%	2744
	11th to 20th	Day	8% 7% 2 7% 4 3 3 2 3 6% 54%	3447
	21st to end	Day	17% 12% 6% 13% 4 3 3 3 4 5% 30%	4587
January	1st to 10th	Night	12% 9% 3 14% 5% 4 3 3 4 6% 37%	6018
	11th to 20th	Night	6% 7% 3 7% 4 6% 5% 4 5% 6% 48%	5979
	21st to end	Night	12% 11% 4 6% 4 3 4 2 4 5% 46%	6490
February	1st to 10th	Night	10% 11% 3 6% 5% 4 4 3 5% 6% 42%	2600
	11th to 20th	Night	10% 7% 3 8% 5% 4 4 4 5% 6% 44%	2440
	21st to end	Night	8% 7% 2 5% 4 4 4 4 5% 5% 52%	1980
March	1st to 10th	Night	11% 6% 2 4 2 3 3 2 4 5% 57%	4976
	11th to 20th	Night	8% 4 1 5% 3 3 3 3 5% 8% 57%	4980
	21st to end	Night	12% 7% 3 6% 4 4 4 3 5% 7% 44%	5467
April	1st to 10th	Night	11% 5% 2 5% 4 3 3 3 4 7% 52%	2186
	11th to 20th	Night	13% 7% 2 6% 3 4 4 3 5% 7% 47%	1870
	21st to end	Night	15% 6% 2 6% 4 4 4 3 5% 7% 44%	1800
May	1st to 10th	Night	16% 6% 2 5% 3 3 3 3 5% 6% 49%	4053
	11th to 20th	Night	14% 4 2 4 3 3 3 3 4 6% 54%	4053
	21st to end	Night	17% 5% 2 5% 3 3 3 3 4 6% 48%	4443
June	1st to 10th	Night	6% 3 1 4 3 4 5% 3 6% 9% 56%	1800
	11th to 20th	Night	6% 4 1 3 3 4 4 5% 7% 9% 54%	1800
	21st to end	Night	6% 2 1 4 4 4 3 3 7% 9% 58%	1800
July	1st to 10th	Night	7% 4 2 6% 3 4 5% 4 5% 8% 52%	4078
	11th to 20th	Night	4 5% 2 5% 4 4 4 4 6% 9% 53%	4077
	21st to end	Night	8% 4 2 5% 4 4 4 3 5% 9% 53%	4449
August	1st to 10th	Night	2 3 1 5% 3 4 4 4 6% 10% 56%	2926
	11th to 20th	Night	9% 6% 2 6% 4 4 4 4 4 7% 51%	2888
	21st to end	Night	5% 3 1 4 3 3 3 3 5% 7% 61%	3323
September	1st to 10th	Night	10% 3 1 4 3 3 3 3 4 6% 59%	2145
	11th to 20th	Night	9% 4 2 5% 4 3 3 3 5% 6% 56%	2200
	21st to end	Night	8% 3 2 4 4 3 3 3 5% 5% 60%	2200
October	1st to 10th	Night	12% 4 2 5% 3 3 4 3 5% 6% 54%	2298
	11th to 20th	Night	11% 5% 2 4 2 3 2 2 4 6% 60%	2400
	21st to end	Night	13% 6% 2 5% 3 2 2 3 4 5% 55%	2640
November	1st to 10th	Night	8% 5% 2 4 3 3 3 2 4 6% 61%	2605
	11th to 20th	Night	8% 5% 2 4 3 3 3 3 5% 6% 59%	2730
	21st to end	Night	12% 7% 2 5% 3 3 3 2 4 5% 54%	2730
December	1st to 10th	Night	5% 5% 2 4 3 3 4 3 5% 6% 61%	4631
	11th to 20th	Night	9% 6% 2 6% 4 4 4 4 5% 7% 51%	4946
	21st to end	Night	16% 12% 5% 9% 4 3 3 3 4 4 37%	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	46% 5% 12% 23% 12% 1	4168
	11th to 20th	Day	45% 3 13% 19% 17% 3	4134
	21st to end	Day	43% 4 11% 24% 16% 2	4488
February	1st to 10th	Day	45% 5% 14% 22% 11% 4	1800
	11th to 20th	Day	40% 5% 13% 25% 14% 4	1872
	21st to end	Day	34% 4 9% 26% 21% 5%	1650
March	1st to 10th	Day	33% 3 8% 19% 26% 11%	4867
	11th to 20th	Day	30% 3 8% 21% 29% 8%	4980
	21st to end	Day	42% 5% 13% 30% 8% 1	5464
April	1st to 10th	Day	37% 4 12% 23% 20% 4	2212
	11th to 20th	Day	39% 6% 11% 23% 18% 2	2477
	21st to end	Day	44% 6% 11% 26% 13%	2600
May	1st to 10th	Day	40% 6% 9% 25% 19% 2	5900
	11th to 20th	Day	34% 5% 9% 21% 24% 7%	5866
	21st to end	Day	42% 7% 10% 26% 14% 2	6447
June	1st to 10th	Day	27% 7% 15% 33% 16% 2	2600
	11th to 20th	Day	30% 7% 14% 27% 20% 3	2600
	21st to end	Day	26% 7% 14% 29% 19% 5%	2600
July	1st to 10th	Day	31% 5% 12% 27% 22% 4	5836
	11th to 20th	Day	33% 6% 13% 27% 18% 3	5831
	21st to end	Day	29% 6% 13% 32% 18% 2	6240
August	1st to 10th	Day	29% 6% 13% 25% 22% 4	4220
	11th to 20th	Day	35% 5% 14% 26% 18% 2	4210
	21st to end	Day	25% 6% 15% 28% 19% 7%	4580
September	1st to 10th	Day	29% 5% 12% 27% 20% 7%	2251
	11th to 20th	Day	32% 6% 10% 26% 23% 3	2200
	21st to end	Day	30% 6% 8% 27% 26% 4	2200
October	1st to 10th	Day	21% 3 7% 19% 43% 7%	3393
	11th to 20th	Day	18% 3 7% 30% 32% 10%	3240
	21st to end	Day	30% 3 9% 24% 30% 5%	3538
November	1st to 10th	Day	26% 4 13% 29% 22% 6%	1909
	11th to 20th	Day	31% 4 9% 27% 26% 4	1890
	21st to end	Day	35% 4 11% 29% 19% 2	1890
December	1st to 10th	Day	27% 4 10% 40% 18% 1	2744
	11th to 20th	Day	34% 3 11% 37% 14% 1	3445
	21st to end	Day	57% 3 9% 21% 8% 1	4587
January	1st to 10th	Night	49% 4 11% 24% 12% 1	6018
	11th to 20th	Night	37% 3 12% 25% 20% 3	5979
	21st to end	Night	42% 3 11% 18% 18% 7%	6490
February	1st to 10th	Night	43% 5% 12% 22% 14% 4	2600
	11th to 20th	Night	40% 5% 10% 26% 15% 3	2441
	21st to end	Night	33% 4 9% 23% 23% 8%	1980
March	1st to 10th	Night	30% 3 7% 25% 29% 6%	4976
	11th to 20th	Night	26% 3 7% 20% 34% 10%	4980
	21st to end	Night	40% 6% 16% 28% 10% 2	5467
April	1st to 10th	Night	32% 5% 12% 23% 24% 4	2186
	11th to 20th	Night	36% 5% 10% 24% 20% 3	1870
	21st to end	Night	40% 6% 11% 24% 17% 2	1800
May	1st to 10th	Night	36% 5% 11% 24% 20% 4	4080
	11th to 20th	Night	31% 5% 10% 24% 23% 8%	4054
	21st to end	Night	37% 6% 13% 26% 17% 1	4452
June	1st to 10th	Night	23% 9% 14% 32% 19% 3	1800
	11th to 20th	Night	25% 8% 13% 32% 18% 4	1800
	21st to end	Night	22% 6% 13% 33% 21% 5%	1800
July	1st to 10th	Night	30% 5% 13% 24% 22% 6%	4035
	11th to 20th	Night	27% 6% 12% 27% 26% 2	4026
	21st to end	Night	28% 5% 12% 33% 20% 2	4320
August	1st to 10th	Night	22% 6% 18% 25% 21% 7%	2916
	11th to 20th	Night	33% 6% 13% 26% 20% 2	2915
	21st to end	Night	22% 5% 15% 32% 21% 5%	3323
September	1st to 10th	Night	26% 5% 11% 28% 21% 9%	2145
	11th to 20th	Night	27% 6% 11% 26% 25% 5%	2200
	21st to end	Night	26% 5% 8% 25% 31% 5%	2200
October	1st to 10th	Night	22% 3 6% 18% 44% 7%	3753
	11th to 20th	Night	20% 3 5% 29% 31% 12%	3899
	21st to end	Night	28% 3 8% 28% 29% 4	4252
November	1st to 10th	Night	26% 4 11% 28% 25% 7%	2605
	11th to 20th	Night	27% 3 11% 30% 25% 5%	2730
	21st to end	Night	33% 4 10% 28% 21% 4	2730
December	1st to 10th	Night	25% 4 14% 35% 21% 1	4631
	11th to 20th	Night	34% 4 12% 30% 18% 2	4947
	21st to end	Night	52% 3 9% 24% 10% 1	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	15% 16% 36% 23% 9%	330
	11th to 20th	Day	19% 18% 40% 19% 4	318
	21st to end	Day	13% 11% 48% 24% 4	330
February	1st to 10th	Day	19% 20% 42% 15% 4	300
	11th to 20th	Day	17% 15% 46% 16% 6%	300
	21st to end	Day	14% 18% 50% 15% 2	249
March	1st to 10th	Day	17% 18% 40% 20% 4	300
	11th to 20th	Day	26% 13% 39% 17% 5%	300
	21st to end	Day	25% 20% 39% 13% 2 1	330
April	1st to 10th	Day	22% 19% 36% 18% 4	312
	11th to 20th	Day	17% 18% 38% 21% 5%	595
	21st to end	Day	23% 18% 32% 19% 7% 1	700
May	1st to 10th	Day	18% 14% 36% 22% 9% 1	703
	11th to 20th	Day	18% 14% 26% 25% 14% 2	725
	21st to end	Day	17% 12% 30% 25% 14% 3	789
June	1st to 10th	Day	7% 5% 26% 34% 21% 7%	730
	11th to 20th	Day	8% 4 33% 33% 18% 3	730
	21st to end	Day	7% 7% 35% 37% 11% 2	730
July	1st to 10th	Day	10% 4 18% 35% 26% 7%	721
	11th to 20th	Day	5% 4 22% 38% 25% 6%	718
	21st to end	Day	7% 2 17% 40% 28% 5%	794
August	1st to 10th	Day	7% 3 21% 39% 27% 3	726
	11th to 20th	Day	8% 4 19% 42% 24% 5%	715
	21st to end	Day	10% 2 18% 34% 28% 8%	748
September	1st to 10th	Day	13% 2 17% 40% 24% 3	381
	11th to 20th	Day	6% 5% 25% 37% 22% 4	330
	21st to end	Day	12% 8% 29% 31% 16% 3	330
October	1st to 10th	Day	15% 8% 32% 29% 12% 5%	330
	11th to 20th	Day	8% 18% 40% 24% 9% 1	330
	21st to end	Day	21% 17% 32% 22% 6% 2	363
November	1st to 10th	Day	13% 19% 34% 25% 8% 1	330
	11th to 20th	Day	15% 17% 36% 22% 8% 1	330
	21st to end	Day	22% 13% 36% 18% 9% 2	330
December	1st to 10th	Day	11% 12% 42% 26% 8% 1	330
	11th to 20th	Day	14% 18% 39% 22% 7%	330
	21st to end	Day	20% 15% 39% 21% 5%	363
January	1st to 10th	Night	13% 13% 36% 31% 7%	1050
	11th to 20th	Night	14% 10% 40% 29% 6% 1	1031
	21st to end	Night	13% 9% 41% 33% 4	1100
February	1st to 10th	Night	17% 10% 41% 29% 3	1000
	11th to 20th	Night	13% 14% 40% 29% 4	886
	21st to end	Night	14% 13% 42% 26% 5%	660
March	1st to 10th	Night	15% 12% 42% 28% 3	633
	11th to 20th	Night	16% 12% 37% 29% 6%	600
	21st to end	Night	20% 15% 39% 21% 4	660
April	1st to 10th	Night	14% 14% 41% 25% 6%	600
	11th to 20th	Night	19% 16% 33% 28% 4 1	593
	21st to end	Night	19% 9% 40% 26% 6% 1	600
May	1st to 10th	Night	18% 9% 32% 33% 9% 1	600
	11th to 20th	Night	16% 8% 30% 34% 11% 1	591
	21st to end	Night	14% 7% 30% 33% 14% 1	650
June	1st to 10th	Night	7% 5% 25% 42% 20% 1	600
	11th to 20th	Night	7% 3 33% 38% 19%	600
	21st to end	Night	6% 4 32% 46% 11%	600
July	1st to 10th	Night	8% 2 18% 45% 27% 1	585
	11th to 20th	Night	3 1 23% 50% 21% 2	582
	21st to end	Night	7% 2 17% 46% 26% 2	657
August	1st to 10th	Night	4 2 22% 48% 23% 1	597
	11th to 20th	Night	6% 2 17% 48% 26% 1	594
	21st to end	Night	7% 2 16% 46% 27% 3	660
September	1st to 10th	Night	10% 2 24% 42% 20% 2	600
	11th to 20th	Night	10% 2 27% 39% 20% 2	600
	21st to end	Night	8% 4 25% 42% 19% 1	600
October	1st to 10th	Night	14% 6% 28% 35% 16% 2	698
	11th to 20th	Night	13% 9% 39% 31% 8%	800
	21st to end	Night	17% 12% 33% 28% 9%	880
November	1st to 10th	Night	10% 10% 33% 36% 10%	965
	11th to 20th	Night	11% 13% 38% 32% 6%	1050
	21st to end	Night	16% 12% 32% 32% 8%	1050
December	1st to 10th	Night	11% 11% 36% 34% 7%	1050
	11th to 20th	Night	17% 10% 38% 30% 5%	1050
	21st to end	Night	17% 12% 36% 31% 4	1155

Page generated at 2026-01-14 00:14:26. Version ac07

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