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 2026-09-29.

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% 7% 58%	148848
	Night	7% 4 1 4 3 3 3 3 5% 7% 60%	143019
Transparency	Day	26% 4 9% 24% 27% 10%	152617
	Night	24% 4 8% 24% 28% 12%	147304
Seeing	Day	9% 8% 27% 32% 20% 4	17908
	Night	9% 8% 34% 36% 12% 1	27698

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	5% 6% 2 5% 3 3 4 3 4 6% 58%	5289
	11th to 20th	Day	4 5% 1 3 2 2 2 2 3 4 71%	5310
	21st to end	Day	13% 8% 2 5% 3 3 2 2 3 7% 51%	5904
February	1st to 10th	Day	8% 7% 3 5% 3 3 3 2 4 5% 57%	2100
	11th to 20th	Day	9% 6% 2 5% 3 3 3 3 4 5% 57%	2049
	21st to end	Day	9% 8% 1 5% 4 3 3 2 3 4 58%	1730
March	1st to 10th	Day	10% 5% 2 4 3 3 3 3 4 5% 59%	4770
	11th to 20th	Day	7% 5% 2 5% 3 3 3 3 5% 6% 58%	5090
	21st to end	Day	7% 7% 2 5% 4 3 3 3 5% 7% 53%	5583
April	1st to 10th	Day	8% 5% 2 4 3 3 3 3 4 7% 59%	2331
	11th to 20th	Day	11% 5% 2 5% 4 3 4 3 4 6% 53%	2494
	21st to end	Day	11% 5% 2 4 3 3 4 3 5% 6% 53%	2728
May	1st to 10th	Day	13% 6% 2 5% 4 3 3 3 5% 6% 48%	7617
	11th to 20th	Day	9% 5% 2 5% 3 3 3 3 5% 6% 56%	7627
	21st to end	Day	10% 6% 3 7% 5% 4 4 4 6% 6% 45%	8392
June	1st to 10th	Day	6% 4 1 4 4 4 4 5% 6% 10% 51%	2730
	11th to 20th	Day	5% 3 1 3 4 4 4 4 6% 7% 58%	2730
	21st to end	Day	5% 3 1 4 3 3 3 4 6% 7% 62%	2730
July	1st to 10th	Day	7% 5% 2 6% 5% 4 5% 5% 7% 9% 46%	7680
	11th to 20th	Day	3 3 1 4 4 4 5% 5% 6% 9% 55%	7680
	21st to end	Day	1 2 1 3 3 3 3 3 5% 9% 67%	8337
August	1st to 10th	Day	3 2 1 3 3 2 3 3 5% 7% 68%	6014
	11th to 20th	Day	3 2 1 2 2 3 3 3 4 7% 70%	5720
	21st to end	Day	3 2 1 4 3 3 3 3 6% 7% 65%	6079
September	1st to 10th	Day	8% 4 1 4 3 3 3 3 5% 6% 60%	2328
	11th to 20th	Day	8% 5% 3 5% 4 4 4 3 4 8% 52%	2310
	21st to end	Day	8% 3 1 4 2 3 4 3 5% 6% 60%	2288
October	1st to 10th	Day	7% 3 1 4 2 3 3 2 5% 6% 63%	2200
	11th to 20th	Day	9% 3 1 3 2 2 2 2 3 5% 68%	2059
	21st to end	Day	10% 4 2 3 3 3 3 2 3 4 65%	2200
November	1st to 10th	Day	7% 4 1 3 2 2 3 3 4 6% 65%	1871
	11th to 20th	Day	6% 3 1 3 3 2 3 2 4 5% 69%	1890
	21st to end	Day	10% 4 1 4 2 3 3 2 4 6% 62%	1890
December	1st to 10th	Day	5% 5% 2 5% 3 3 4 3 5% 6% 60%	3030
	11th to 20th	Day	5% 4 1 4 3 3 4 3 4 5% 63%	3481
	21st to end	Day	10% 8% 3 7% 4 4 4 3 4 5% 50%	4587
January	1st to 10th	Night	8% 5% 1 5% 3 4 4 3 5% 6% 55%	7634
	11th to 20th	Night	2 2 1 3 2 3 2 2 4 5% 73%	7680
	21st to end	Night	12% 8% 2 5% 3 3 3 3 4 6% 52%	8365
February	1st to 10th	Night	10% 5% 2 4 3 3 3 3 4 5% 57%	2520
	11th to 20th	Night	9% 6% 2 4 3 3 3 3 5% 7% 54%	2458
	21st to end	Night	8% 6% 2 5% 4 3 3 2 4 6% 58%	2076
March	1st to 10th	Night	6% 4 2 5% 3 3 4 3 4 6% 60%	5314
	11th to 20th	Night	6% 3 1 3 2 3 3 3 4 6% 66%	5090
	21st to end	Night	6% 5% 2 5% 4 3 4 4 6% 8% 54%	5588
April	1st to 10th	Night	8% 4 2 3 3 3 4 3 5% 8% 58%	2284
	11th to 20th	Night	11% 4 1 5% 3 3 3 3 6% 7% 54%	2077
	21st to end	Night	11% 4 2 4 3 3 3 4 5% 7% 54%	1890
May	1st to 10th	Night	13% 5% 1 4 3 3 5% 3 5% 6% 51%	5266
	11th to 20th	Night	8% 4 1 4 3 3 4 4 6% 8% 55%	5265
	21st to end	Night	11% 5% 2 5% 4 4 4 4 5% 8% 49%	5793
June	1st to 10th	Night	4 3 1 3 3 3 3 4 8% 11% 56%	1890
	11th to 20th	Night	4 3 2 4 3 3 4 3 7% 11% 58%	1890
	21st to end	Night	3 2 1 3 3 3 3 3 6% 9% 62%	1890
July	1st to 10th	Night	4 5% 2 6% 4 4 5% 4 7% 11% 48%	5308
	11th to 20th	Night	3 2 1 4 3 3 5% 3 6% 13% 57%	5307
	21st to end	Night	1 2 1 3 3 3 4 3 5% 8% 69%	5770
August	1st to 10th	Night	1 1 2 2 2 3 3 6% 9% 70%	4156
	11th to 20th	Night	3 2 1 3 2 3 3 3 6% 10% 65%	4328
	21st to end	Night	2 1 1 3 3 3 4 3 6% 11% 64%	5069
September	1st to 10th	Night	6% 4 1 4 3 2 3 3 4 7% 61%	2290
	11th to 20th	Night	7% 6% 2 5% 4 3 4 3 4 7% 54%	2310
	21st to end	Night	7% 3 1 4 3 3 4 3 5% 6% 61%	2288
October	1st to 10th	Night	6% 3 1 4 3 3 4 3 4 6% 63%	2200
	11th to 20th	Night	7% 3 2 3 3 3 2 2 3 4 68%	2320
	21st to end	Night	9% 5% 1 3 2 2 2 2 4 5% 65%	2640
November	1st to 10th	Night	7% 4 1 3 2 2 2 2 4 5% 68%	2644
	11th to 20th	Night	5% 3 1 3 2 2 3 2 4 6% 68%	2730
	21st to end	Night	10% 4 1 4 2 2 3 2 4 6% 61%	2730
December	1st to 10th	Night	5% 4 2 3 2 2 3 2 4 7% 65%	4380
	11th to 20th	Night	5% 5% 2 4 3 2 3 3 4 5% 64%	4946
	21st to end	Night	10% 7% 2 5% 3 4 3 3 4 5% 55%	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	27% 3 6% 28% 29% 7%	5290
	11th to 20th	Day	18% 2 7% 18% 43% 12%	5310
	21st to end	Day	36% 2 5% 20% 29% 9%	5904
February	1st to 10th	Day	31% 3 6% 23% 28% 9%	2100
	11th to 20th	Day	31% 3 7% 26% 23% 9%	2059
	21st to end	Day	32% 2 5% 16% 30% 15%	1730
March	1st to 10th	Day	28% 3 6% 13% 22% 28%	4770
	11th to 20th	Day	28% 2 7% 17% 29% 18%	5090
	21st to end	Day	31% 3 10% 28% 23% 5%	5585
April	1st to 10th	Day	26% 4 10% 24% 23% 13%	2331
	11th to 20th	Day	33% 5% 7% 19% 23% 13%	2494
	21st to end	Day	31% 5% 10% 25% 24% 6%	2728
May	1st to 10th	Day	37% 5% 10% 19% 21% 9%	7655
	11th to 20th	Day	29% 4 8% 23% 26% 10%	7631
	21st to end	Day	37% 7% 12% 21% 14% 9%	8405
June	1st to 10th	Day	28% 7% 15% 28% 16% 6%	2730
	11th to 20th	Day	23% 6% 12% 27% 25% 7%	2730
	21st to end	Day	21% 5% 13% 27% 25% 8%	2730
July	1st to 10th	Day	32% 8% 10% 25% 21% 4	7616
	11th to 20th	Day	23% 7% 15% 26% 24% 5%	7611
	21st to end	Day	15% 4 11% 37% 29% 3	8155
August	1st to 10th	Day	16% 4 10% 23% 33% 15%	6000
	11th to 20th	Day	14% 5% 9% 31% 32% 9%	5759
	21st to end	Day	18% 5% 11% 31% 30% 5%	6078
September	1st to 10th	Day	26% 5% 8% 22% 26% 13%	2328
	11th to 20th	Day	33% 5% 9% 22% 25% 7%	2310
	21st to end	Day	25% 5% 7% 24% 30% 10%	2288
October	1st to 10th	Day	14% 3 7% 14% 39% 22%	3590
	11th to 20th	Day	18% 4 6% 23% 31% 18%	3325
	21st to end	Day	20% 3 5% 27% 34% 10%	3538
November	1st to 10th	Day	21% 3 8% 24% 29% 15%	1871
	11th to 20th	Day	18% 3 6% 28% 33% 12%	1890
	21st to end	Day	27% 2 6% 24% 30% 11%	1890
December	1st to 10th	Day	24% 4 8% 35% 23% 6%	3030
	11th to 20th	Day	24% 3 8% 18% 36% 12%	3479
	21st to end	Day	36% 4 5% 27% 20% 8%	4587
January	1st to 10th	Night	29% 3 6% 30% 27% 5%	7635
	11th to 20th	Night	14% 2 9% 20% 38% 17%	7680
	21st to end	Night	35% 2 6% 20% 28% 10%	8365
February	1st to 10th	Night	30% 4 6% 22% 27% 11%	2520
	11th to 20th	Night	31% 3 7% 22% 25% 12%	2458
	21st to end	Night	29% 3 5% 18% 26% 20%	2076
March	1st to 10th	Night	25% 4 4 15% 22% 30%	5314
	11th to 20th	Night	20% 3 5% 19% 24% 29%	5090
	21st to end	Night	27% 4 11% 20% 30% 7%	5588
April	1st to 10th	Night	25% 4 10% 20% 25% 15%	2284
	11th to 20th	Night	29% 5% 9% 21% 24% 13%	2077
	21st to end	Night	30% 4 10% 27% 22% 7%	1890
May	1st to 10th	Night	33% 5% 12% 20% 20% 10%	5293
	11th to 20th	Night	27% 5% 9% 22% 25% 12%	5266
	21st to end	Night	33% 7% 14% 19% 14% 13%	5805
June	1st to 10th	Night	20% 6% 19% 32% 17% 6%	1890
	11th to 20th	Night	20% 6% 14% 29% 25% 7%	1890
	21st to end	Night	19% 4 12% 29% 25% 10%	1890
July	1st to 10th	Night	29% 6% 11% 32% 20% 3	5265
	11th to 20th	Night	18% 6% 15% 31% 24% 6%	5256
	21st to end	Night	14% 4 11% 34% 33% 4	5641
August	1st to 10th	Night	11% 3 8% 25% 35% 18%	4146
	11th to 20th	Night	15% 4 7% 29% 38% 7%	4355
	21st to end	Night	15% 5% 12% 32% 31% 5%	5069
September	1st to 10th	Night	24% 4 10% 21% 28% 13%	2290
	11th to 20th	Night	31% 4 9% 21% 25% 9%	2310
	21st to end	Night	24% 5% 7% 24% 28% 13%	2288
October	1st to 10th	Night	14% 3 6% 16% 38% 23%	3590
	11th to 20th	Night	20% 4 5% 18% 35% 19%	3767
	21st to end	Night	18% 2 5% 27% 34% 14%	4252
November	1st to 10th	Night	20% 3 7% 22% 31% 16%	2644
	11th to 20th	Night	19% 3 6% 25% 33% 14%	2730
	21st to end	Night	26% 3 6% 22% 29% 14%	2730
December	1st to 10th	Night	20% 3 6% 33% 31% 7%	4380
	11th to 20th	Night	24% 3 5% 22% 33% 14%	4947
	21st to end	Night	31% 5% 7% 24% 25% 8%	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	11% 12% 39% 27% 9% 2	330
	11th to 20th	Day	14% 19% 29% 28% 10% 1	330
	21st to end	Day	11% 14% 39% 28% 7%	363
February	1st to 10th	Day	13% 14% 39% 28% 6%	330
	11th to 20th	Day	13% 18% 43% 21% 5%	330
	21st to end	Day	14% 20% 38% 21% 7%	273
March	1st to 10th	Day	13% 20% 37% 25% 4 1	330
	11th to 20th	Day	17% 19% 38% 18% 7% 1	330
	21st to end	Day	12% 15% 42% 24% 6% 1	363
April	1st to 10th	Day	13% 18% 34% 26% 8%	351
	11th to 20th	Day	14% 18% 47% 18% 2	532
	21st to end	Day	14% 15% 39% 24% 7% 1	748
May	1st to 10th	Day	10% 12% 40% 31% 7% 1	753
	11th to 20th	Day	12% 11% 32% 27% 16% 2	775
	21st to end	Day	12% 7% 33% 30% 15% 3	844
June	1st to 10th	Day	7% 4 26% 37% 22% 4	780
	11th to 20th	Day	7% 3 25% 45% 18% 2	780
	21st to end	Day	4 2 22% 43% 24% 5%	780
July	1st to 10th	Day	6% 1 13% 35% 35% 10%	771
	11th to 20th	Day	2 2 11% 41% 37% 8%	768
	21st to end	Day	2 1 6% 37% 43% 11%	849
August	1st to 10th	Day	4 2 9% 43% 36% 6%	776
	11th to 20th	Day	6% 1 10% 40% 35% 7%	667
	21st to end	Day	6% 1 7% 37% 38% 11%	627
September	1st to 10th	Day	9% 2 7% 33% 39% 11%	378
	11th to 20th	Day	5% 1 11% 40% 35% 8%	360
	21st to end	Day	9% 4 13% 38% 26% 9%	354
October	1st to 10th	Day	5% 3 25% 36% 25% 5%	330
	11th to 20th	Day	8% 9% 30% 35% 16% 1	330
	21st to end	Day	20% 10% 26% 28% 15% 2	363
November	1st to 10th	Day	13% 7% 36% 29% 13% 2	330
	11th to 20th	Day	11% 11% 32% 31% 14% 2	330
	21st to end	Day	14% 11% 39% 24% 12% 1	330
December	1st to 10th	Day	9% 11% 42% 27% 11%	330
	11th to 20th	Day	12% 11% 38% 29% 9% 1	330
	21st to end	Day	15% 15% 39% 24% 6% 1	363
January	1st to 10th	Night	9% 11% 40% 32% 8% 1	1050
	11th to 20th	Night	9% 12% 35% 36% 7%	1050
	21st to end	Night	10% 10% 39% 33% 7%	1144
February	1st to 10th	Night	13% 10% 40% 31% 6%	840
	11th to 20th	Night	12% 14% 42% 26% 5%	824
	21st to end	Night	12% 14% 45% 27% 2	692
March	1st to 10th	Night	10% 14% 41% 31% 4	764
	11th to 20th	Night	16% 13% 40% 26% 5%	630
	21st to end	Night	8% 16% 46% 26% 4	693
April	1st to 10th	Night	10% 15% 46% 25% 5%	630
	11th to 20th	Night	14% 12% 52% 20% 2	623
	21st to end	Night	12% 13% 43% 26% 5%	630
May	1st to 10th	Night	10% 9% 49% 27% 5%	630
	11th to 20th	Night	11% 9% 39% 31% 10%	621
	21st to end	Night	8% 7% 38% 35% 11% 1	683
June	1st to 10th	Night	4 4 35% 40% 15% 1	630
	11th to 20th	Night	4 4 41% 44% 7%	630
	21st to end	Night	4 2 29% 48% 15% 1	630
July	1st to 10th	Night	6% 2 16% 46% 28% 2	615
	11th to 20th	Night	2 1 14% 55% 26% 2	612
	21st to end	Night	2 8% 59% 29% 2	690
August	1st to 10th	Night	2 1 13% 53% 30% 1	627
	11th to 20th	Night	4 1 14% 51% 28% 1	624
	21st to end	Night	4 1 11% 48% 34% 2	693
September	1st to 10th	Night	7% 2 17% 45% 27% 1	630
	11th to 20th	Night	10% 2 23% 41% 21% 2	630
	21st to end	Night	7% 3 24% 44% 20% 2	624
October	1st to 10th	Night	7% 3 30% 42% 17% 1	600
	11th to 20th	Night	9% 6% 36% 37% 12%	720
	21st to end	Night	10% 10% 34% 32% 13% 1	880
November	1st to 10th	Night	9% 7% 36% 36% 10% 1	1004
	11th to 20th	Night	7% 8% 37% 37% 10%	1050
	21st to end	Night	12% 11% 34% 33% 10%	1050
December	1st to 10th	Night	10% 10% 35% 36% 8%	1050
	11th to 20th	Night	12% 10% 39% 34% 6%	1050
	21st to end	Night	12% 11% 37% 33% 6%	1155

Page generated at 2026-09-26 03:18:42. Version ac07

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