Great Plains State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Great Plains State Park clear sky chart from 2005-11-06 to 2025-05-26.

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	7% 5% 2 4 3 3 3 3 5% 6% 58%	114483
	Night	7% 4 2 4 3 3 3 3 5% 7% 60%	115059
Transparency	Day	26% 4 9% 24% 26% 10%	118293
	Night	24% 4 8% 24% 28% 13%	119365
Seeing	Day	10% 8% 27% 32% 20% 4	15993
	Night	9% 8% 34% 36% 12% 1	25994

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	7% 7% 2 6% 3 3 3 3 4 6% 56%	4077
	11th to 20th	Day	5% 5% 1 2 2 2 3 3 4 5% 68%	4080
	21st to end	Day	12% 7% 3 6% 3 3 2 2 3 7% 52%	4552
February	1st to 10th	Day	8% 8% 3 5% 3 3 3 3 4 5% 56%	2000
	11th to 20th	Day	9% 6% 2 5% 3 3 3 3 4 6% 56%	1949
	21st to end	Day	9% 8% 1 5% 4 4 3 2 3 4 57%	1650
March	1st to 10th	Day	10% 5% 2 4 3 3 3 3 4 5% 59%	4666
	11th to 20th	Day	7% 5% 2 5% 3 3 3 3 5% 6% 58%	4980
	21st to end	Day	8% 7% 2 5% 4 3 3 3 5% 7% 52%	5462
April	1st to 10th	Day	8% 5% 2 4 3 3 3 3 4 7% 59%	2220
	11th to 20th	Day	11% 6% 2 5% 4 3 3 3 4 6% 53%	2374
	21st to end	Day	11% 5% 2 5% 3 3 4 3 5% 6% 54%	2598
May	1st to 10th	Day	14% 6% 2 6% 4 4 3 3 5% 6% 47%	4212
	11th to 20th	Day	11% 5% 2 5% 4 3 3 3 5% 6% 53%	4212
	21st to end	Day	10% 4 2 5% 4 4 4 3 5% 6% 52%	4543
June	1st to 10th	Day	6% 4 1 4 4 4 4 5% 6% 10% 52%	2470
	11th to 20th	Day	5% 3 1 3 4 4 4 4 6% 7% 59%	2470
	21st to end	Day	5% 2 1 4 3 3 3 3 6% 7% 64%	2470
July	1st to 10th	Day	7% 4 2 5% 4 4 5% 5% 6% 8% 51%	4120
	11th to 20th	Day	3 3 1 4 3 4 4 4 5% 8% 60%	4120
	21st to end	Day	2 3 1 4 3 3 4 4 6% 9% 61%	4465
August	1st to 10th	Day	4 3 1 4 3 3 4 3 5% 7% 62%	4104
	11th to 20th	Day	4 3 1 3 3 3 4 4 5% 9% 61%	3888
	21st to end	Day	3 2 1 4 3 3 3 3 5% 7% 65%	4180
September	1st to 10th	Day	8% 4 1 4 3 3 3 3 4 6% 59%	2106
	11th to 20th	Day	8% 5% 3 6% 4 4 4 3 4 8% 50%	2090
	21st to end	Day	8% 3 1 3 2 3 4 3 5% 6% 61%	2090
October	1st to 10th	Day	7% 3 1 4 2 3 3 2 5% 6% 63%	2090
	11th to 20th	Day	10% 3 1 3 2 2 2 2 3 4 68%	1956
	21st to end	Day	10% 4 2 3 3 3 3 2 3 4 65%	2090
November	1st to 10th	Day	7% 4 1 3 2 2 3 3 4 6% 64%	1780
	11th to 20th	Day	6% 3 1 3 3 2 3 2 4 5% 69%	1800
	21st to end	Day	10% 4 1 4 2 3 3 2 4 6% 61%	1800
December	1st to 10th	Day	5% 5% 2 5% 3 3 4 3 5% 6% 60%	2940
	11th to 20th	Day	5% 4 1 4 3 3 4 3 5% 5% 62%	3391
	21st to end	Day	10% 8% 3 7% 4 4 4 3 4 5% 49%	4488
January	1st to 10th	Night	10% 6% 2 6% 3 3 3 3 4 6% 54%	5888
	11th to 20th	Night	3 2 1 3 2 3 3 3 5% 6% 68%	5900
	21st to end	Night	10% 9% 2 5% 2 3 3 3 4 5% 54%	6467
February	1st to 10th	Night	11% 5% 2 4 3 3 3 3 4 5% 57%	2400
	11th to 20th	Night	10% 6% 2 5% 3 3 3 3 5% 7% 54%	2338
	21st to end	Night	8% 6% 2 5% 4 3 3 2 4 6% 56%	1980
March	1st to 10th	Night	6% 4 2 5% 3 3 4 3 4 6% 60%	5198
	11th to 20th	Night	6% 3 1 3 2 3 3 3 4 6% 66%	4980
	21st to end	Night	6% 5% 2 5% 4 3 4 4 6% 8% 54%	5467
April	1st to 10th	Night	8% 4 2 3 3 3 4 3 5% 7% 58%	2175
	11th to 20th	Night	11% 4 1 5% 3 3 3 3 6% 7% 54%	1977
	21st to end	Night	11% 5% 2 5% 3 3 3 3 5% 6% 54%	1800
May	1st to 10th	Night	16% 5% 2 3 3 3 3 3 4 5% 53%	2913
	11th to 20th	Night	11% 5% 2 5% 4 4 3 3 5% 7% 50%	2913
	21st to end	Night	8% 4 2 4 3 3 3 3 4 6% 59%	3140
June	1st to 10th	Night	3 3 1 3 3 4 3 4 8% 11% 57%	1710
	11th to 20th	Night	4 3 1 4 3 3 4 3 7% 11% 58%	1710
	21st to end	Night	4 3 1 3 3 3 3 3 6% 9% 64%	1710
July	1st to 10th	Night	4 4 2 5% 4 3 4 4 6% 10% 53%	2850
	11th to 20th	Night	2 2 1 2 3 3 4 3 6% 13% 62%	2850
	21st to end	Night	2 2 1 3 3 3 4 3 6% 8% 66%	3098
August	1st to 10th	Night	2 2 2 3 2 4 3 6% 9% 66%	2836
	11th to 20th	Night	4 2 1 4 3 3 4 4 7% 11% 57%	2947
	21st to end	Night	2 2 1 3 3 3 4 4 6% 10% 64%	3487
September	1st to 10th	Night	7% 4 1 4 3 2 3 3 5% 7% 59%	2072
	11th to 20th	Night	8% 6% 2 6% 4 3 4 3 4 7% 53%	2090
	21st to end	Night	7% 3 1 4 3 3 3 3 5% 6% 63%	2090
October	1st to 10th	Night	7% 3 1 4 2 3 3 3 4 6% 63%	2090
	11th to 20th	Night	8% 3 2 3 3 3 2 2 3 4 68%	2204
	21st to end	Night	9% 5% 1 3 2 2 2 2 4 5% 66%	2508
November	1st to 10th	Night	7% 4 1 3 2 2 2 2 4 6% 67%	2515
	11th to 20th	Night	5% 3 1 3 2 2 3 2 4 6% 68%	2600
	21st to end	Night	10% 4 1 4 3 3 3 2 4 6% 61%	2600
December	1st to 10th	Night	5% 4 2 3 2 2 3 2 4 7% 65%	4250
	11th to 20th	Night	5% 5% 2 4 3 3 3 3 4 6% 63%	4816
	21st to end	Night	10% 7% 2 5% 3 4 3 3 4 5% 54%	6490

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	29% 3 7% 30% 25% 5%	4078
	11th to 20th	Day	19% 3 8% 21% 38% 11%	4080
	21st to end	Day	36% 2 5% 19% 29% 10%	4552
February	1st to 10th	Day	31% 3 6% 23% 28% 9%	2000
	11th to 20th	Day	31% 3 7% 26% 23% 9%	1959
	21st to end	Day	34% 2 5% 16% 29% 15%	1650
March	1st to 10th	Day	28% 3 5% 13% 23% 28%	4666
	11th to 20th	Day	28% 3 7% 16% 28% 18%	4980
	21st to end	Day	31% 3 10% 28% 23% 5%	5464
April	1st to 10th	Day	26% 4 11% 24% 23% 13%	2220
	11th to 20th	Day	33% 4 7% 20% 23% 13%	2374
	21st to end	Day	31% 5% 10% 24% 24% 6%	2598
May	1st to 10th	Day	38% 5% 9% 17% 18% 13%	4250
	11th to 20th	Day	32% 4 11% 26% 20% 7%	4216
	21st to end	Day	33% 5% 10% 21% 19% 12%	4555
June	1st to 10th	Day	27% 7% 15% 28% 16% 6%	2470
	11th to 20th	Day	22% 6% 12% 27% 26% 7%	2470
	21st to end	Day	20% 5% 13% 26% 26% 9%	2470
July	1st to 10th	Day	28% 8% 10% 28% 21% 5%	4056
	11th to 20th	Day	20% 5% 10% 30% 30% 5%	4051
	21st to end	Day	18% 5% 11% 32% 30% 3	4325
August	1st to 10th	Day	20% 4 11% 22% 31% 12%	4090
	11th to 20th	Day	20% 6% 12% 28% 25% 9%	3927
	21st to end	Day	18% 6% 13% 33% 26% 5%	4179
September	1st to 10th	Day	27% 5% 8% 21% 25% 14%	2106
	11th to 20th	Day	34% 5% 9% 19% 25% 7%	2090
	21st to end	Day	24% 5% 7% 23% 31% 10%	2090
October	1st to 10th	Day	14% 3 7% 14% 39% 23%	3480
	11th to 20th	Day	18% 4 6% 22% 31% 19%	3222
	21st to end	Day	20% 3 5% 28% 34% 10%	3428
November	1st to 10th	Day	22% 3 8% 24% 27% 15%	1780
	11th to 20th	Day	18% 3 6% 29% 32% 12%	1800
	21st to end	Day	27% 2 6% 23% 31% 12%	1800
December	1st to 10th	Day	24% 4 8% 36% 23% 6%	2940
	11th to 20th	Day	25% 3 8% 18% 35% 12%	3389
	21st to end	Day	37% 4 5% 27% 20% 7%	4488
January	1st to 10th	Night	31% 4 6% 31% 23% 4	5888
	11th to 20th	Night	17% 3 10% 20% 35% 15%	5900
	21st to end	Night	34% 2 6% 19% 28% 11%	6467
February	1st to 10th	Night	30% 4 7% 22% 26% 11%	2400
	11th to 20th	Night	31% 3 7% 22% 25% 12%	2338
	21st to end	Night	30% 3 5% 18% 25% 20%	1980
March	1st to 10th	Night	25% 4 4 15% 22% 30%	5198
	11th to 20th	Night	20% 3 5% 19% 23% 29%	4980
	21st to end	Night	27% 4 11% 20% 31% 7%	5467
April	1st to 10th	Night	25% 4 10% 19% 25% 16%	2175
	11th to 20th	Night	29% 4 8% 21% 24% 13%	1977
	21st to end	Night	30% 4 10% 27% 22% 7%	1800
May	1st to 10th	Night	34% 5% 8% 17% 21% 14%	2940
	11th to 20th	Night	33% 5% 13% 22% 19% 7%	2914
	21st to end	Night	26% 5% 11% 20% 21% 16%	3149
June	1st to 10th	Night	19% 6% 20% 32% 17% 7%	1710
	11th to 20th	Night	20% 6% 15% 27% 25% 7%	1710
	21st to end	Night	18% 4 11% 29% 27% 11%	1710
July	1st to 10th	Night	25% 6% 11% 36% 20% 3	2805
	11th to 20th	Night	14% 4 8% 36% 30% 7%	2796
	21st to end	Night	16% 5% 12% 29% 34% 4	2999
August	1st to 10th	Night	14% 4 10% 23% 35% 14%	2826
	11th to 20th	Night	20% 5% 9% 31% 27% 8%	2974
	21st to end	Night	16% 6% 13% 35% 25% 5%	3487
September	1st to 10th	Night	25% 5% 9% 21% 27% 13%	2072
	11th to 20th	Night	33% 4 9% 19% 25% 10%	2090
	21st to end	Night	22% 4 7% 23% 30% 14%	2090
October	1st to 10th	Night	14% 3 6% 16% 37% 24%	3480
	11th to 20th	Night	20% 4 5% 18% 35% 19%	3651
	21st to end	Night	18% 2 5% 27% 35% 14%	4120
November	1st to 10th	Night	21% 3 7% 22% 31% 16%	2515
	11th to 20th	Night	19% 3 6% 24% 33% 15%	2600
	21st to end	Night	26% 3 6% 21% 30% 15%	2600
December	1st to 10th	Night	20% 3 6% 33% 31% 7%	4250
	11th to 20th	Night	24% 3 5% 22% 33% 14%	4817
	21st to end	Night	32% 5% 7% 24% 25% 8%	6490

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	12% 12% 38% 27% 9% 2	300
	11th to 20th	Day	14% 19% 30% 28% 9%	300
	21st to end	Day	10% 14% 41% 28% 6%	330
February	1st to 10th	Day	14% 14% 40% 27% 5%	300
	11th to 20th	Day	13% 17% 44% 20% 5%	300
	21st to end	Day	15% 20% 37% 20% 7%	249
March	1st to 10th	Day	13% 20% 36% 27% 4 1	300
	11th to 20th	Day	17% 19% 39% 18% 6% 1	300
	21st to end	Day	12% 17% 43% 22% 6%	330
April	1st to 10th	Day	15% 19% 35% 24% 7%	320
	11th to 20th	Day	15% 17% 46% 19% 2	492
	21st to end	Day	14% 16% 37% 25% 7% 1	698
May	1st to 10th	Day	10% 12% 39% 31% 8% 1	703
	11th to 20th	Day	11% 11% 32% 28% 16% 2	725
	21st to end	Day	11% 7% 34% 30% 14% 3	760
June	1st to 10th	Day	7% 2 25% 38% 23% 4	680
	11th to 20th	Day	6% 3 25% 45% 19% 2	680
	21st to end	Day	5% 2 18% 44% 26% 6%	680
July	1st to 10th	Day	5% 1 13% 35% 36% 11%	671
	11th to 20th	Day	2 2 10% 39% 38% 9%	668
	21st to end	Day	2 1 6% 37% 42% 12%	739
August	1st to 10th	Day	4 2 8% 42% 38% 7%	676
	11th to 20th	Day	7% 1 11% 38% 35% 7%	577
	21st to end	Day	4 1 6% 37% 38% 13%	539
September	1st to 10th	Day	10% 2 6% 31% 39% 12%	316
	11th to 20th	Day	6% 1 11% 38% 34% 10%	300
	21st to end	Day	11% 4 13% 37% 26% 10%	300
October	1st to 10th	Day	5% 3 27% 34% 25% 6%	300
	11th to 20th	Day	9% 10% 31% 35% 14% 1	300
	21st to end	Day	19% 10% 27% 26% 15% 2	330
November	1st to 10th	Day	14% 6% 37% 28% 13% 2	300
	11th to 20th	Day	11% 12% 33% 28% 14% 2	300
	21st to end	Day	14% 10% 38% 24% 13% 1	300
December	1st to 10th	Day	9% 10% 42% 28% 11%	300
	11th to 20th	Day	13% 11% 38% 28% 9% 1	300
	21st to end	Day	16% 16% 40% 23% 5%	330
January	1st to 10th	Night	9% 11% 40% 32% 8% 1	1000
	11th to 20th	Night	9% 12% 35% 36% 8%	1000
	21st to end	Night	9% 10% 39% 34% 7%	1090
February	1st to 10th	Night	13% 11% 40% 30% 6%	800
	11th to 20th	Night	13% 13% 42% 27% 5%	784
	21st to end	Night	12% 14% 44% 27% 3	660
March	1st to 10th	Night	10% 14% 40% 31% 5%	728
	11th to 20th	Night	16% 13% 40% 26% 5%	600
	21st to end	Night	9% 16% 45% 26% 4	660
April	1st to 10th	Night	9% 15% 47% 24% 5%	600
	11th to 20th	Night	14% 12% 52% 20% 2	593
	21st to end	Night	12% 14% 42% 27% 5% 1	600
May	1st to 10th	Night	11% 9% 48% 26% 6%	600
	11th to 20th	Night	10% 8% 39% 32% 10% 1	591
	21st to end	Night	7% 6% 39% 35% 12% 1	634
June	1st to 10th	Night	4 4 33% 42% 16% 1	570
	11th to 20th	Night	4 3 41% 45% 7%	570
	21st to end	Night	4 2 27% 49% 17% 1	570
July	1st to 10th	Night	6% 2 14% 46% 30% 2	555
	11th to 20th	Night	3 1 13% 55% 26% 2	552
	21st to end	Night	2 7% 58% 30% 2	624
August	1st to 10th	Night	2 1 12% 51% 32% 1	567
	11th to 20th	Night	5% 1 15% 49% 28% 1	564
	21st to end	Night	3 1 12% 47% 35% 2	627
September	1st to 10th	Night	8% 2 17% 44% 29% 2	570
	11th to 20th	Night	12% 2 23% 38% 23% 2	570
	21st to end	Night	7% 3 24% 44% 21% 2	570
October	1st to 10th	Night	7% 3 29% 41% 18% 1	570
	11th to 20th	Night	9% 6% 36% 37% 12%	684
	21st to end	Night	11% 9% 35% 32% 13% 1	836
November	1st to 10th	Night	9% 7% 36% 36% 10% 1	955
	11th to 20th	Night	7% 8% 38% 35% 11%	1000
	21st to end	Night	12% 11% 34% 33% 10%	1000
December	1st to 10th	Night	10% 10% 35% 36% 9%	1000
	11th to 20th	Night	12% 10% 39% 33% 6%	1000
	21st to end	Night	13% 11% 37% 32% 6%	1100

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