Glendo State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Glendo State Park clear sky chart from 2005-11-06 to 2026-08-15.

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 5% 4 4 4 4 6% 8% 53%	152977
	Night	5% 5% 2 6% 4 4 4 4 6% 8% 52%	146456
Transparency	Day	26% 6% 12% 25% 21% 9%	147841
	Night	29% 7% 13% 27% 19% 6%	142628
Seeing	Day	9% 11% 28% 30% 18% 5%	18279
	Night	8% 9% 34% 38% 11% 1	28206

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	1 7% 4 10% 6% 5% 5% 3 6% 7% 47%	4720
	11th to 20th	Day	1 6% 3 8% 6% 5% 5% 5% 6% 8% 47%	4740
	21st to end	Day	1 3 2 6% 5% 4 5% 4 6% 7% 56%	5620
February	1st to 10th	Day	2 10% 4 7% 5% 3 5% 3 7% 10% 44%	1890
	11th to 20th	Day	3 8% 3 8% 6% 4 7% 5% 6% 9% 44%	1962
	21st to end	Day	4 7% 2 6% 4 3 4 4 5% 7% 54%	1730
March	1st to 10th	Day	5% 10% 3 6% 3 3 3 2 4 8% 52%	4600
	11th to 20th	Day	5% 6% 2 6% 4 3 4 4 4 7% 54%	4985
	21st to end	Day	7% 7% 3 8% 5% 4 4 4 7% 9% 43%	5979
April	1st to 10th	Day	7% 8% 2 6% 4 4 4 4 6% 9% 48%	2520
	11th to 20th	Day	10% 9% 3 6% 5% 4 5% 4 6% 7% 41%	2491
	21st to end	Day	9% 8% 3 7% 4 4 5% 4 6% 8% 43%	2541
May	1st to 10th	Day	10% 7% 2 6% 4 4 4 3 5% 7% 47%	7953
	11th to 20th	Day	9% 5% 2 5% 3 4 5% 4 7% 8% 48%	8191
	21st to end	Day	10% 5% 2 6% 4 4 5% 4 7% 9% 46%	9026
June	1st to 10th	Day	5% 4 2 4 4 4 5% 5% 8% 10% 49%	2940
	11th to 20th	Day	7% 5% 1 3 3 4 4 5% 8% 8% 52%	2940
	21st to end	Day	5% 2 1 3 3 4 5% 4 7% 9% 56%	2940
July	1st to 10th	Day	3 2 1 3 3 4 5% 5% 8% 9% 58%	8249
	11th to 20th	Day	2 2 1 3 3 3 4 4 6% 8% 64%	8250
	21st to end	Day	5% 3 1 4 4 4 5% 5% 8% 10% 49%	8957
August	1st to 10th	Day	6% 3 1 4 3 4 5% 4 8% 10% 53%	6110
	11th to 20th	Day	2 3 1 4 4 4 4 4 6% 8% 60%	5559
	21st to end	Day	6% 4 2 5% 4 4 5% 4 7% 8% 53%	5984
September	1st to 10th	Day	6% 4 1 3 2 3 3 3 5% 7% 62%	2400
	11th to 20th	Day	7% 3 1 3 3 3 3 3 4 8% 61%	2377
	21st to end	Day	6% 4 1 3 2 2 3 3 5% 7% 64%	2200
October	1st to 10th	Day	5% 3 1 2 2 2 2 1 3 5% 73%	3275
	11th to 20th	Day	8% 5% 2 4 3 3 3 3 4 6% 60%	3250
	21st to end	Day	7% 6% 2 4 3 3 3 4 5% 8% 57%	3302
November	1st to 10th	Day	3 4 2 5% 3 3 4 4 6% 8% 56%	1853
	11th to 20th	Day	3 4 2 4 3 3 4 4 7% 8% 58%	1865
	21st to end	Day	2 6% 3 6% 4 4 4 4 6% 8% 53%	1680
December	1st to 10th	Day	1 4 3 4 3 3 4 2 5% 7% 64%	2700
	11th to 20th	Day	2 4 2 5% 3 3 4 4 6% 9% 58%	3106
	21st to end	Day	2 7% 3 7% 5% 5% 5% 4 6% 8% 48%	4092
January	1st to 10th	Night	1 6% 3 9% 5% 5% 6% 5% 7% 8% 43%	8201
	11th to 20th	Night	2 6% 4 10% 5% 4 4 4 5% 7% 49%	8250
	21st to end	Night	1 5% 3 9% 5% 5% 4 4 5% 9% 51%	8651
February	1st to 10th	Night	3 7% 3 8% 6% 5% 5% 4 6% 8% 45%	2730
	11th to 20th	Night	2 8% 3 8% 5% 5% 6% 4 7% 8% 44%	2544
	21st to end	Night	2 7% 3 7% 5% 5% 4 4 6% 7% 51%	2076
March	1st to 10th	Night	5% 9% 3 6% 4 4 4 4 5% 7% 51%	5494
	11th to 20th	Night	4 7% 2 5% 3 4 4 3 5% 7% 56%	5214
	21st to end	Night	8% 10% 4 8% 4 4 4 4 6% 8% 40%	5220
April	1st to 10th	Night	9% 6% 2 6% 5% 4 4 3 7% 7% 48%	2100
	11th to 20th	Night	10% 7% 3 7% 5% 4 4 4 5% 7% 44%	2077
	21st to end	Night	11% 8% 3 7% 5% 4 4 3 5% 7% 43%	2079
May	1st to 10th	Night	11% 7% 2 6% 4 4 3 3 4 6% 48%	4991
	11th to 20th	Night	9% 6% 2 5% 3 3 4 4 6% 7% 50%	4701
	21st to end	Night	11% 5% 2 7% 4 4 4 4 6% 9% 45%	5181
June	1st to 10th	Night	5% 3 1 4 4 4 4 4 8% 9% 53%	1680
	11th to 20th	Night	7% 4 1 4 2 3 3 4 6% 10% 57%	1680
	21st to end	Night	4 2 1 4 2 3 4 4 5% 8% 63%	1680
July	1st to 10th	Night	4 3 2 5% 4 5% 5% 5% 8% 9% 50%	4740
	11th to 20th	Night	3 2 1 3 3 3 4 3 7% 8% 63%	4740
	21st to end	Night	5% 3 2 7% 5% 6% 7% 6% 8% 9% 44%	5152
August	1st to 10th	Night	8% 3 2 4 3 4 4 3 6% 9% 53%	3906
	11th to 20th	Night	2 2 1 5% 5% 5% 6% 5% 7% 9% 53%	4366
	21st to end	Night	6% 4 2 6% 4 4 4 4 6% 8% 51%	4993
September	1st to 10th	Night	6% 4 2 4 3 3 3 3 4 7% 64%	2000
	11th to 20th	Night	5% 4 2 5% 3 3 3 3 4 7% 60%	2022
	21st to end	Night	8% 4 1 3 3 3 3 2 3 5% 65%	2200
October	1st to 10th	Night	5% 4 1 2 2 2 2 2 3 4 73%	3910
	11th to 20th	Night	8% 4 1 4 4 3 4 3 5% 7% 57%	3898
	21st to end	Night	6% 5% 2 4 3 3 4 3 6% 9% 56%	4465
November	1st to 10th	Night	4 6% 2 5% 4 3 4 4 6% 8% 53%	2665
	11th to 20th	Night	3 5% 2 5% 4 4 4 4 7% 9% 52%	2751
	21st to end	Night	3 7% 2 5% 4 4 3 3 7% 7% 56%	2940
December	1st to 10th	Night	2 5% 2 5% 3 4 4 3 4 7% 62%	4710
	11th to 20th	Night	2 6% 2 6% 4 4 4 4 6% 9% 53%	5321
	21st to end	Night	3 7% 3 8% 5% 5% 5% 4 7% 9% 45%	7128

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	33% 7% 15% 26% 18% 1	4723
	11th to 20th	Day	32% 8% 17% 23% 16% 4	4740
	21st to end	Day	25% 5% 14% 30% 21% 5%	5620
February	1st to 10th	Day	35% 6% 17% 25% 15% 2	1890
	11th to 20th	Day	36% 7% 12% 24% 15% 5%	1971
	21st to end	Day	29% 5% 15% 25% 20% 6%	1730
March	1st to 10th	Day	30% 4 8% 28% 23% 6%	4600
	11th to 20th	Day	27% 7% 15% 27% 21% 2	4985
	21st to end	Day	34% 9% 15% 29% 12% 1	5979
April	1st to 10th	Day	32% 6% 17% 26% 15% 4	2520
	11th to 20th	Day	39% 7% 12% 20% 18% 5%	2494
	21st to end	Day	37% 7% 12% 27% 15% 1	2541
May	1st to 10th	Day	34% 6% 12% 29% 16% 3	7953
	11th to 20th	Day	30% 7% 10% 24% 22% 6%	8195
	21st to end	Day	31% 8% 14% 28% 18% 3	9027
June	1st to 10th	Day	25% 9% 17% 25% 17% 6%	2940
	11th to 20th	Day	25% 7% 14% 22% 20% 12%	2940
	21st to end	Day	21% 7% 11% 23% 25% 13%	2940
July	1st to 10th	Day	17% 7% 9% 22% 28% 17%	8181
	11th to 20th	Day	15% 6% 8% 24% 23% 23%	8175
	21st to end	Day	24% 9% 13% 15% 20% 18%	8759
August	1st to 10th	Day	23% 7% 11% 23% 23% 13%	4488
	11th to 20th	Day	22% 7% 9% 20% 25% 17%	4041
	21st to end	Day	19% 5% 9% 17% 27% 22%	4311
September	1st to 10th	Day	21% 4 9% 20% 28% 17%	2400
	11th to 20th	Day	21% 5% 9% 22% 27% 15%	2377
	21st to end	Day	20% 4 7% 28% 31% 9%	2200
October	1st to 10th	Day	17% 3 7% 17% 30% 25%	3275
	11th to 20th	Day	26% 4 11% 28% 25% 7%	3250
	21st to end	Day	25% 5% 9% 34% 22% 4	3302
November	1st to 10th	Day	24% 6% 14% 27% 23% 7%	1853
	11th to 20th	Day	21% 5% 15% 32% 23% 4	1865
	21st to end	Day	28% 6% 14% 26% 23% 4	1680
December	1st to 10th	Day	20% 5% 16% 34% 23% 2	2700
	11th to 20th	Day	22% 5% 16% 38% 16% 3	3104
	21st to end	Day	31% 7% 13% 33% 14% 2	4092
January	1st to 10th	Night	33% 10% 12% 30% 13% 2	8202
	11th to 20th	Night	32% 8% 16% 25% 15% 4	8250
	21st to end	Night	31% 6% 14% 30% 16% 3	8651
February	1st to 10th	Night	33% 7% 17% 26% 14% 3	2730
	11th to 20th	Night	36% 7% 15% 24% 14% 4	2545
	21st to end	Night	30% 5% 14% 25% 21% 4	2076
March	1st to 10th	Night	30% 5% 8% 27% 23% 6%	5494
	11th to 20th	Night	26% 6% 15% 24% 27% 2	5214
	21st to end	Night	39% 9% 19% 21% 12% 1	5220
April	1st to 10th	Night	34% 8% 14% 25% 15% 4	2100
	11th to 20th	Night	38% 7% 12% 22% 17% 5%	2077
	21st to end	Night	40% 8% 11% 25% 16% 1	2079
May	1st to 10th	Night	35% 6% 11% 27% 19% 1	4992
	11th to 20th	Night	31% 7% 12% 30% 14% 5%	4702
	21st to end	Night	32% 8% 17% 29% 12% 2	5182
June	1st to 10th	Night	25% 9% 22% 24% 15% 5%	1680
	11th to 20th	Night	23% 6% 16% 26% 21% 9%	1680
	21st to end	Night	18% 7% 14% 27% 23% 11%	1680
July	1st to 10th	Night	25% 8% 13% 25% 18% 11%	4700
	11th to 20th	Night	17% 6% 12% 27% 22% 16%	4692
	21st to end	Night	32% 9% 14% 16% 18% 10%	5038
August	1st to 10th	Night	28% 7% 13% 25% 19% 8%	2864
	11th to 20th	Night	26% 8% 12% 23% 18% 12%	3172
	21st to end	Night	20% 5% 12% 19% 27% 17%	3597
September	1st to 10th	Night	22% 3 7% 25% 29% 14%	2000
	11th to 20th	Night	24% 5% 8% 24% 25% 14%	2022
	21st to end	Night	23% 3 8% 25% 27% 14%	2200
October	1st to 10th	Night	17% 4 7% 19% 30% 24%	3910
	11th to 20th	Night	27% 5% 12% 26% 25% 6%	3898
	21st to end	Night	24% 4 13% 29% 21% 8%	4465
November	1st to 10th	Night	27% 6% 14% 25% 23% 6%	2665
	11th to 20th	Night	26% 6% 12% 30% 21% 5%	2751
	21st to end	Night	26% 5% 12% 31% 21% 5%	2940
December	1st to 10th	Night	23% 5% 15% 35% 19% 3	4710
	11th to 20th	Night	27% 5% 14% 40% 13% 2	5322
	21st to end	Night	33% 8% 13% 32% 13% 2	7128

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	8% 14% 27% 29% 16% 6%	330
	11th to 20th	Day	11% 16% 28% 30% 12% 2	330
	21st to end	Day	7% 11% 38% 33% 8% 3	363
February	1st to 10th	Day	8% 15% 43% 23% 10% 1	330
	11th to 20th	Day	7% 15% 35% 34% 8%	330
	21st to end	Day	8% 17% 36% 29% 10% 1	273
March	1st to 10th	Day	10% 18% 25% 31% 15% 1	330
	11th to 20th	Day	13% 15% 39% 21% 10% 1	480
	21st to end	Day	14% 18% 30% 27% 9% 2	594
April	1st to 10th	Day	14% 19% 35% 21% 10% 2	540
	11th to 20th	Day	16% 21% 33% 21% 8% 1	532
	21st to end	Day	14% 14% 31% 28% 12% 2	561
May	1st to 10th	Day	14% 13% 29% 28% 13% 4	753
	11th to 20th	Day	15% 13% 23% 27% 17% 4	775
	21st to end	Day	13% 9% 28% 30% 16% 4	844
June	1st to 10th	Day	5% 9% 26% 31% 20% 8%	780
	11th to 20th	Day	9% 10% 32% 32% 15% 2	780
	21st to end	Day	7% 5% 30% 31% 23% 3	780
July	1st to 10th	Day	4 4 19% 37% 29% 6%	771
	11th to 20th	Day	2 3 21% 39% 27% 7%	768
	21st to end	Day	5% 3 20% 35% 31% 7%	849
August	1st to 10th	Day	6% 4 21% 36% 27% 6%	666
	11th to 20th	Day	5% 5% 21% 32% 26% 11%	534
	21st to end	Day	4 6% 25% 34% 22% 8%	583
September	1st to 10th	Day	7% 6% 24% 30% 26% 8%	530
	11th to 20th	Day	6% 8% 26% 27% 23% 10%	507
	21st to end	Day	6% 7% 25% 29% 18% 14%	330
October	1st to 10th	Day	8% 9% 22% 27% 21% 13%	330
	11th to 20th	Day	12% 14% 29% 24% 15% 6%	330
	21st to end	Day	9% 14% 30% 27% 16% 4	363
November	1st to 10th	Day	7% 13% 30% 31% 14% 5%	330
	11th to 20th	Day	8% 12% 35% 30% 12% 2	330
	21st to end	Day	7% 11% 34% 29% 15% 5%	330
December	1st to 10th	Day	6% 15% 36% 27% 14% 2	330
	11th to 20th	Day	8% 15% 36% 31% 10%	330
	21st to end	Day	10% 17% 32% 27% 12% 2	363
January	1st to 10th	Night	5% 13% 36% 34% 12% 1	1050
	11th to 20th	Night	6% 17% 38% 30% 8% 1	1050
	21st to end	Night	7% 10% 38% 37% 8%	1024
February	1st to 10th	Night	6% 11% 42% 34% 7%	840
	11th to 20th	Night	7% 10% 39% 36% 8% 1	824
	21st to end	Night	5% 10% 46% 33% 6%	692
March	1st to 10th	Night	9% 11% 38% 35% 8%	840
	11th to 20th	Night	9% 8% 36% 39% 8%	840
	21st to end	Night	11% 11% 35% 35% 7%	754
April	1st to 10th	Night	13% 13% 33% 37% 5%	630
	11th to 20th	Night	13% 11% 38% 32% 6%	623
	21st to end	Night	16% 10% 30% 32% 11%	630
May	1st to 10th	Night	15% 9% 29% 33% 13% 1	630
	11th to 20th	Night	14% 7% 30% 35% 13% 1	621
	21st to end	Night	12% 8% 31% 35% 14%	683
June	1st to 10th	Night	6% 7% 33% 38% 15% 1	630
	11th to 20th	Night	9% 7% 38% 38% 8%	630
	21st to end	Night	5% 5% 32% 43% 15%	630
July	1st to 10th	Night	6% 4 27% 44% 18% 1	615
	11th to 20th	Night	3 3 26% 50% 17%	612
	21st to end	Night	5% 1 23% 51% 20%	690
August	1st to 10th	Night	5% 2 24% 52% 17%	627
	11th to 20th	Night	4 2 25% 48% 21%	606
	21st to end	Night	4 4 24% 46% 22% 1	660
September	1st to 10th	Night	7% 3 22% 47% 21% 1	600
	11th to 20th	Night	6% 5% 28% 40% 20% 2	600
	21st to end	Night	9% 6% 28% 42% 16% 1	600
October	1st to 10th	Night	12% 5% 28% 35% 18% 2	790
	11th to 20th	Night	10% 6% 32% 39% 13%	800
	21st to end	Night	9% 8% 35% 36% 12% 1	1005
November	1st to 10th	Night	7% 7% 35% 38% 12% 1	1025
	11th to 20th	Night	5% 13% 37% 37% 7% 1	1050
	21st to end	Night	6% 9% 34% 41% 9% 1	1050
December	1st to 10th	Night	6% 12% 40% 34% 8%	1050
	11th to 20th	Night	7% 9% 41% 36% 6%	1050
	21st to end	Night	10% 14% 36% 33% 7%	1155

Page generated at 2026-08-12 01:37:14. Version ac07

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