Fort Hays State University
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Hays State University clear sky chart from 2005-11-06 to 2024-11-28.

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	8% 5% 2 5% 3 3 4 3 5% 7% 54%	105921
	Night	8% 5% 2 5% 3 3 3 3 5% 7% 56%	102251
Transparency	Day	30% 3 12% 27% 22% 6%	105680
	Night	29% 3 12% 27% 24% 6%	102082
Seeing	Day	11% 8% 31% 32% 15% 3	15696
	Night	10% 8% 35% 36% 10% 1	25620

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	7% 8% 3 7% 3 4 4 3 6% 7% 48%	2847
	11th to 20th	Day	6% 9% 3 7% 5% 5% 5% 3 5% 7% 45%	2850
	21st to end	Day	7% 10% 4 7% 3 3 3 2 4 6% 51%	3135
February	1st to 10th	Day	7% 10% 3 6% 4 4 4 2 5% 7% 47%	1814
	11th to 20th	Day	5% 6% 2 6% 5% 5% 4 4 5% 6% 52%	1849
	21st to end	Day	7% 6% 2 5% 4 4 4 3 5% 5% 56%	1570
March	1st to 10th	Day	9% 6% 1 3 3 3 3 3 4 6% 59%	3174
	11th to 20th	Day	9% 6% 2 4 3 3 3 3 4 5% 58%	3480
	21st to end	Day	10% 7% 2 4 3 4 4 4 6% 7% 50%	3814
April	1st to 10th	Day	9% 5% 2 4 3 4 4 3 5% 7% 55%	2209
	11th to 20th	Day	9% 7% 3 5% 4 4 4 3 5% 7% 48%	2301
	21st to end	Day	15% 6% 2 5% 3 3 4 3 5% 7% 46%	2470
May	1st to 10th	Day	13% 5% 2 6% 4 4 4 4 5% 7% 47%	4120
	11th to 20th	Day	10% 5% 2 5% 3 4 4 3 6% 8% 48%	4082
	21st to end	Day	11% 4 2 5% 4 4 4 4 5% 7% 49%	4489
June	1st to 10th	Day	5% 3 2 3 3 4 4 4 5% 9% 59%	2470
	11th to 20th	Day	6% 4 1 4 4 3 4 4 6% 7% 58%	2592
	21st to end	Day	5% 3 2 4 4 4 3 3 6% 8% 59%	2660
July	1st to 10th	Day	7% 4 2 5% 4 4 4 4 6% 8% 52%	4430
	11th to 20th	Day	4 3 1 4 3 4 4 5% 7% 10% 56%	4184
	21st to end	Day	4 3 1 4 4 4 5% 4 7% 9% 55%	4466
August	1st to 10th	Day	11% 6% 2 5% 3 3 3 4 5% 8% 50%	4103
	11th to 20th	Day	9% 4 2 4 3 4 4 4 6% 9% 50%	4041
	21st to end	Day	4 3 1 4 3 3 4 4 6% 7% 62%	4196
September	1st to 10th	Day	10% 4 2 4 3 3 3 2 5% 5% 60%	2172
	11th to 20th	Day	8% 5% 2 5% 2 2 3 3 5% 6% 59%	2090
	21st to end	Day	7% 3 1 4 3 3 4 3 4 6% 61%	2090
October	1st to 10th	Day	9% 2 1 2 1 2 2 2 3 5% 71%	3480
	11th to 20th	Day	5% 3 1 3 3 3 3 3 5% 7% 65%	3182
	21st to end	Day	8% 5% 1 3 2 2 2 2 4 6% 65%	3219
November	1st to 10th	Day	7% 4 1 4 3 2 3 2 4 6% 62%	1763
	11th to 20th	Day	6% 6% 1 4 3 2 3 3 5% 5% 64%	1800
	21st to end	Day	10% 6% 2 3 3 2 2 2 4 5% 62%	1773
December	1st to 10th	Day	6% 7% 2 5% 3 3 4 4 5% 7% 54%	1710
	11th to 20th	Day	7% 6% 3 6% 4 3 3 2 5% 6% 56%	2161
	21st to end	Day	9% 14% 5% 9% 4 4 3 3 5% 6% 38%	3135
January	1st to 10th	Night	6% 9% 3 12% 4 4 3 2 4 6% 47%	4108
	11th to 20th	Night	5% 6% 3 6% 4 5% 3 3 5% 6% 55%	4120
	21st to end	Night	10% 8% 3 7% 3 3 3 3 4 5% 51%	4532
February	1st to 10th	Night	8% 9% 3 7% 5% 4 3 3 4 5% 49%	2380
	11th to 20th	Night	6% 5% 2 6% 5% 4 5% 4 6% 7% 50%	2218
	21st to end	Night	6% 6% 3 6% 4 3 3 2 4 4 58%	1884
March	1st to 10th	Night	9% 4 2 4 2 2 2 3 4 6% 61%	3686
	11th to 20th	Night	7% 4 2 4 3 3 4 3 5% 7% 58%	3480
	21st to end	Night	11% 7% 2 5% 3 4 4 3 4 7% 51%	3817
April	1st to 10th	Night	9% 5% 1 4 3 3 4 2 5% 9% 54%	1967
	11th to 20th	Night	12% 4 2 5% 4 3 4 3 5% 7% 50%	1825
	21st to end	Night	14% 5% 2 4 4 3 3 4 5% 6% 51%	1710
May	1st to 10th	Night	15% 6% 2 4 4 3 3 3 6% 6% 48%	2850
	11th to 20th	Night	12% 4 2 6% 3 4 4 3 6% 8% 49%	2823
	21st to end	Night	10% 4 2 5% 4 3 4 4 6% 9% 48%	3098
June	1st to 10th	Night	5% 3 1 4 3 3 4 4 7% 11% 56%	1710
	11th to 20th	Night	7% 3 2 4 4 4 4 3 7% 9% 53%	1581
	21st to end	Night	5% 2 1 4 4 4 6% 4 6% 10% 54%	1520
July	1st to 10th	Night	8% 4 1 5% 5% 5% 5% 4 6% 7% 49%	2540
	11th to 20th	Night	4 3 1 4 4 4 4 5% 7% 11% 53%	2779
	21st to end	Night	5% 3 1 4 3 4 4 4 6% 10% 58%	3097
August	1st to 10th	Night	6% 3 2 5% 4 4 4 4 7% 11% 49%	2836
	11th to 20th	Night	8% 5% 2 5% 4 4 4 3 5% 8% 51%	2798
	21st to end	Night	4 3 2 4 3 3 3 4 7% 10% 57%	3454
September	1st to 10th	Night	7% 3 1 4 3 2 3 3 4 6% 64%	2006
	11th to 20th	Night	8% 3 1 5% 2 3 3 3 5% 6% 61%	2090
	21st to end	Night	7% 4 1 4 3 3 3 3 5% 6% 62%	2090
October	1st to 10th	Night	6% 2 1 3 2 2 2 2 3 5% 73%	3480
	11th to 20th	Night	6% 2 1 3 2 3 2 2 5% 5% 69%	3705
	21st to end	Night	5% 3 1 3 2 2 3 2 3 7% 68%	4332
November	1st to 10th	Night	7% 3 2 3 2 3 3 2 4 5% 66%	2535
	11th to 20th	Night	7% 4 1 3 3 2 3 2 4 5% 65%	2600
	21st to end	Night	8% 6% 2 4 3 3 3 3 4 5% 59%	2562
December	1st to 10th	Night	5% 5% 2 4 4 3 3 3 4 8% 58%	2470
	11th to 20th	Night	7% 4 2 4 3 3 3 3 5% 7% 59%	3036
	21st to end	Night	11% 12% 4 6% 3 3 3 3 4 6% 45%	4532

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	37% 3 14% 28% 17% 2	2848
	11th to 20th	Day	40% 4 15% 24% 12% 5%	2850
	21st to end	Day	37% 2 16% 28% 15% 2	3135
February	1st to 10th	Day	38% 4 14% 24% 15% 5%	1814
	11th to 20th	Day	33% 3 15% 25% 17% 7%	1859
	21st to end	Day	29% 4 9% 25% 24% 8%	1570
March	1st to 10th	Day	28% 2 9% 19% 31% 10%	3174
	11th to 20th	Day	30% 2 10% 27% 27% 4	3480
	21st to end	Day	34% 3 19% 32% 10% 2	3814
April	1st to 10th	Day	29% 4 10% 26% 23% 7%	2209
	11th to 20th	Day	36% 4 10% 27% 17% 5%	2304
	21st to end	Day	37% 4 11% 29% 17% 2	2470
May	1st to 10th	Day	36% 4 13% 25% 12% 10%	4120
	11th to 20th	Day	34% 4 16% 29% 16% 1	4086
	21st to end	Day	35% 5% 14% 24% 19% 3	4489
June	1st to 10th	Day	22% 4 19% 35% 15% 4	2470
	11th to 20th	Day	25% 4 13% 29% 21% 7%	2592
	21st to end	Day	24% 4 10% 30% 24% 8%	2660
July	1st to 10th	Day	31% 3 11% 25% 23% 7%	4361
	11th to 20th	Day	25% 3 14% 28% 26% 4	4112
	21st to end	Day	24% 3 13% 26% 25% 8%	4325
August	1st to 10th	Day	33% 3 13% 26% 21% 3	4090
	11th to 20th	Day	32% 4 16% 24% 20% 4	4080
	21st to end	Day	22% 3 13% 30% 23% 8%	4195
September	1st to 10th	Day	28% 2 9% 27% 23% 11%	2172
	11th to 20th	Day	26% 3 9% 28% 28% 5%	2090
	21st to end	Day	25% 4 10% 27% 27% 8%	2090
October	1st to 10th	Day	19% 1 5% 22% 41% 12%	3480
	11th to 20th	Day	21% 1 10% 35% 22% 10%	3182
	21st to end	Day	24% 1 6% 28% 33% 8%	3219
November	1st to 10th	Day	25% 2 9% 30% 27% 7%	1763
	11th to 20th	Day	24% 2 7% 29% 31% 6%	1800
	21st to end	Day	27% 2 8% 29% 29% 6%	1773
December	1st to 10th	Day	30% 4 13% 27% 22% 4	1710
	11th to 20th	Day	31% 2 10% 35% 20% 2	2159
	21st to end	Day	48% 2 9% 21% 16% 3	3135
January	1st to 10th	Night	41% 2 12% 27% 15% 2	4108
	11th to 20th	Night	31% 3 14% 26% 22% 4	4120
	21st to end	Night	38% 2 13% 27% 18% 2	4532
February	1st to 10th	Night	38% 4 12% 24% 17% 7%	2380
	11th to 20th	Night	33% 4 12% 27% 20% 4	2218
	21st to end	Night	30% 3 8% 22% 25% 12%	1884
March	1st to 10th	Night	25% 3 8% 24% 30% 11%	3686
	11th to 20th	Night	27% 2 11% 25% 29% 6%	3480
	21st to end	Night	34% 3 16% 35% 10% 2	3817
April	1st to 10th	Night	29% 4 13% 23% 27% 5%	1967
	11th to 20th	Night	33% 4 13% 25% 21% 4	1825
	21st to end	Night	35% 3 11% 28% 20% 3	1710
May	1st to 10th	Night	37% 4 12% 22% 15% 10%	2850
	11th to 20th	Night	34% 4 16% 26% 19% 1	2824
	21st to end	Night	30% 5% 18% 26% 16% 4	3099
June	1st to 10th	Night	21% 5% 17% 32% 20% 4	1710
	11th to 20th	Night	26% 5% 15% 26% 23% 5%	1581
	21st to end	Night	25% 5% 14% 26% 24% 7%	1520
July	1st to 10th	Night	32% 4 14% 20% 25% 4	2500
	11th to 20th	Night	24% 3 13% 29% 26% 5%	2728
	21st to end	Night	23% 2 15% 25% 25% 10%	2999
August	1st to 10th	Night	29% 3 14% 28% 22% 4	2826
	11th to 20th	Night	33% 4 16% 24% 19% 3	2825
	21st to end	Night	23% 3 15% 31% 21% 8%	3454
September	1st to 10th	Night	24% 3 10% 25% 28% 11%	2006
	11th to 20th	Night	25% 4 9% 25% 30% 8%	2090
	21st to end	Night	24% 3 8% 24% 31% 9%	2090
October	1st to 10th	Night	17% 2 5% 19% 46% 11%	3480
	11th to 20th	Night	18% 2 9% 26% 32% 13%	3705
	21st to end	Night	19% 2 8% 27% 37% 8%	4332
November	1st to 10th	Night	23% 3 8% 28% 28% 10%	2535
	11th to 20th	Night	23% 2 8% 29% 30% 9%	2600
	21st to end	Night	28% 2 9% 26% 24% 9%	2562
December	1st to 10th	Night	27% 3 14% 28% 23% 5%	2470
	11th to 20th	Night	27% 2 9% 38% 22% 3	3037
	21st to end	Night	42% 2 11% 28% 14% 2	4532

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% 10% 40% 31% 9% 1	270
	11th to 20th	Day	14% 11% 40% 27% 7%	270
	21st to end	Day	9% 11% 48% 25% 7%	297
February	1st to 10th	Day	16% 14% 44% 23% 3	270
	11th to 20th	Day	11% 11% 47% 21% 8% 2	270
	21st to end	Day	11% 19% 48% 18% 4	225
March	1st to 10th	Day	10% 11% 47% 26% 6%	270
	11th to 20th	Day	19% 15% 35% 20% 10% 1	270
	21st to end	Day	19% 11% 45% 19% 5% 1	297
April	1st to 10th	Day	14% 18% 43% 19% 5% 1	389
	11th to 20th	Day	13% 17% 42% 25% 4	502
	21st to end	Day	20% 15% 38% 20% 6% 2	650
May	1st to 10th	Day	13% 13% 33% 30% 10% 1	653
	11th to 20th	Day	15% 9% 33% 26% 15% 2	675
	21st to end	Day	15% 9% 31% 33% 11% 2	734
June	1st to 10th	Day	5% 5% 27% 37% 19% 8%	680
	11th to 20th	Day	6% 6% 33% 37% 16% 3	680
	21st to end	Day	6% 5% 33% 38% 17% 1	680
July	1st to 10th	Day	8% 2 21% 39% 25% 6%	671
	11th to 20th	Day	3 2 20% 45% 27% 4	668
	21st to end	Day	7% 1 15% 42% 29% 6%	739
August	1st to 10th	Day	9% 2 15% 45% 25% 4	676
	11th to 20th	Day	8% 3 21% 40% 26% 2	665
	21st to end	Day	5% 3 20% 43% 25% 5%	555
September	1st to 10th	Day	10% 3 19% 43% 23% 3	382
	11th to 20th	Day	5% 5% 25% 40% 19% 5%	300
	21st to end	Day	12% 5% 28% 30% 20% 4	300
October	1st to 10th	Day	19% 7% 23% 29% 19% 3	300
	11th to 20th	Day	3 11% 42% 26% 14% 3	300
	21st to end	Day	17% 14% 32% 25% 10% 2	330
November	1st to 10th	Day	14% 10% 39% 25% 10% 1	300
	11th to 20th	Day	13% 12% 39% 25% 9% 2	300
	21st to end	Day	17% 9% 36% 24% 13% 2	291
December	1st to 10th	Day	10% 9% 39% 29% 11% 2	270
	11th to 20th	Day	14% 10% 40% 28% 8% 1	270
	21st to end	Day	19% 13% 42% 22% 4	297
January	1st to 10th	Night	10% 8% 39% 37% 7%	950
	11th to 20th	Night	8% 12% 37% 33% 9% 1	950
	21st to end	Night	9% 9% 43% 33% 5%	1045
February	1st to 10th	Night	13% 8% 41% 32% 6%	860
	11th to 20th	Night	10% 11% 42% 33% 5%	744
	21st to end	Night	10% 13% 44% 28% 5%	628
March	1st to 10th	Night	11% 15% 38% 33% 4	738
	11th to 20th	Night	14% 9% 37% 33% 6% 1	570
	21st to end	Night	19% 13% 40% 24% 4	627
April	1st to 10th	Night	13% 14% 43% 26% 4	570
	11th to 20th	Night	15% 15% 38% 27% 5%	563
	21st to end	Night	16% 14% 34% 30% 6%	570
May	1st to 10th	Night	14% 10% 40% 30% 6%	570
	11th to 20th	Night	14% 10% 32% 34% 9% 1	561
	21st to end	Night	12% 8% 39% 30% 11%	617
June	1st to 10th	Night	6% 6% 36% 36% 14% 1	570
	11th to 20th	Night	6% 8% 39% 38% 9%	570
	21st to end	Night	6% 5% 38% 41% 10%	570
July	1st to 10th	Night	7% 2 26% 46% 18% 1	555
	11th to 20th	Night	5% 1 23% 50% 20% 1	552
	21st to end	Night	8% 1 19% 48% 23% 1	624
August	1st to 10th	Night	7% 2 20% 52% 20%	567
	11th to 20th	Night	9% 2 24% 48% 17% 1	564
	21st to end	Night	4 2 24% 49% 20% 2	627
September	1st to 10th	Night	8% 2 28% 47% 15% 1	570
	11th to 20th	Night	10% 3 33% 39% 15% 1	570
	21st to end	Night	9% 5% 32% 40% 13% 2	570
October	1st to 10th	Night	13% 8% 31% 35% 13% 1	570
	11th to 20th	Night	12% 7% 38% 34% 9%	712
	21st to end	Night	11% 11% 34% 31% 12% 1	960
November	1st to 10th	Night	9% 9% 33% 39% 9% 1	975
	11th to 20th	Night	10% 11% 40% 31% 8%	1000
	21st to end	Night	12% 8% 32% 35% 11% 1	986
December	1st to 10th	Night	9% 8% 39% 37% 7%	950
	11th to 20th	Night	12% 10% 37% 34% 8%	950
	21st to end	Night	13% 11% 36% 35% 6%	1045

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