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 2025-04-11.

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%	117441
	Night	5% 6% 2 6% 4 4 4 4 6% 8% 52%	119737
Transparency	Day	27% 6% 12% 25% 21% 8%	117183
	Night	28% 7% 13% 26% 19% 6%	119585
Seeing	Day	9% 10% 28% 30% 18% 5%	16295
	Night	8% 9% 33% 38% 12% 1	26469

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 11% 6% 5% 5% 3 6% 7% 46%	3638
	11th to 20th	Day	2 8% 3 10% 7% 6% 5% 5% 6% 8% 41%	3640
	21st to end	Day	2 3 2 6% 4 4 4 3 5% 7% 61%	4341
February	1st to 10th	Day	2 10% 4 7% 5% 3 5% 3 7% 9% 44%	1800
	11th to 20th	Day	3 8% 3 7% 5% 4 7% 4 5% 8% 44%	1866
	21st to end	Day	4 7% 2 6% 4 3 4 4 5% 7% 53%	1650
March	1st to 10th	Day	5% 10% 3 7% 3 3 3 2 4 8% 52%	4500
	11th to 20th	Day	5% 6% 2 6% 4 3 4 4 4 7% 54%	4878
	21st to end	Day	7% 7% 3 8% 5% 4 4 4 7% 9% 42%	5850
April	1st to 10th	Day	7% 8% 2 6% 4 4 4 4 6% 9% 47%	2400
	11th to 20th	Day	11% 9% 3 6% 5% 4 5% 4 6% 7% 39%	2252
	21st to end	Day	9% 7% 3 7% 4 4 5% 4 6% 7% 43%	2299
May	1st to 10th	Day	13% 10% 3 8% 5% 5% 5% 3 6% 7% 33%	4289
	11th to 20th	Day	9% 5% 2 5% 4 5% 5% 5% 7% 10% 44%	4388
	21st to end	Day	9% 6% 2 5% 4 4 5% 4 7% 8% 45%	4825
June	1st to 10th	Day	5% 4 2 5% 4 4 5% 5% 8% 10% 49%	2660
	11th to 20th	Day	7% 5% 1 3 3 4 4 5% 8% 8% 51%	2660
	21st to end	Day	4 2 1 3 3 4 5% 4 8% 9% 58%	2660
July	1st to 10th	Day	3 2 1 3 3 4 4 4 7% 8% 63%	4430
	11th to 20th	Day	2 2 1 3 4 4 5% 5% 7% 10% 58%	4430
	21st to end	Day	3 3 1 3 3 4 5% 4 7% 9% 59%	4802
August	1st to 10th	Day	7% 3 1 4 3 3 5% 4 7% 9% 52%	4234
	11th to 20th	Day	3 3 2 4 4 4 5% 5% 7% 8% 57%	3827
	21st to end	Day	3 3 1 4 3 3 4 3 6% 8% 63%	4180
September	1st to 10th	Day	6% 4 1 3 2 3 4 3 5% 7% 62%	2280
	11th to 20th	Day	6% 3 1 3 3 3 3 3 4 8% 63%	2258
	21st to end	Day	6% 4 1 3 2 2 3 3 4 7% 65%	2090
October	1st to 10th	Day	5% 3 1 2 2 2 2 1 3 4 74%	3175
	11th to 20th	Day	8% 5% 2 4 2 3 3 3 4 6% 60%	3150
	21st to end	Day	7% 6% 2 4 3 3 3 4 5% 8% 56%	3200
November	1st to 10th	Day	3 5% 2 5% 3 4 4 4 6% 8% 56%	1763
	11th to 20th	Day	3 4 2 4 3 3 4 4 7% 8% 58%	1776
	21st to end	Day	2 7% 3 6% 4 4 4 4 6% 8% 54%	1600
December	1st to 10th	Day	1 4 3 4 3 3 4 2 4 7% 64%	2620
	11th to 20th	Day	2 4 2 5% 3 3 4 4 6% 9% 58%	3026
	21st to end	Day	2 7% 3 7% 5% 5% 5% 4 6% 8% 48%	4004
January	1st to 10th	Night	2 7% 4 10% 5% 5% 6% 5% 7% 8% 42%	6327
	11th to 20th	Night	1 7% 4 11% 6% 5% 5% 4 5% 7% 46%	6340
	21st to end	Night	2 4 3 8% 5% 4 4 3 4 9% 54%	6680
February	1st to 10th	Night	3 7% 3 8% 6% 5% 5% 4 7% 9% 44%	2600
	11th to 20th	Night	2 8% 4 8% 5% 5% 6% 4 6% 8% 44%	2420
	21st to end	Night	2 7% 3 7% 5% 5% 4 4 6% 7% 50%	1980
March	1st to 10th	Night	5% 9% 3 6% 3 4 4 4 5% 7% 51%	5374
	11th to 20th	Night	4 7% 2 5% 3 4 4 3 5% 7% 56%	5101
	21st to end	Night	8% 9% 4 8% 4 4 4 4 6% 8% 40%	5107
April	1st to 10th	Night	10% 6% 2 5% 5% 4 4 3 7% 7% 47%	2000
	11th to 20th	Night	10% 8% 3 7% 5% 4 4 4 5% 7% 44%	1882
	21st to end	Night	12% 7% 3 7% 5% 4 4 3 5% 7% 43%	1881
May	1st to 10th	Night	11% 9% 3 7% 5% 4 4 4 5% 6% 42%	2678
	11th to 20th	Night	8% 5% 2 5% 3 3 4 4 6% 8% 52%	2517
	21st to end	Night	12% 4 1 5% 4 4 4 4 6% 9% 47%	2762
June	1st to 10th	Night	4 3 1 4 4 4 4 4 8% 9% 53%	1520
	11th to 20th	Night	8% 4 1 4 2 3 3 4 6% 10% 56%	1520
	21st to end	Night	3 2 1 4 2 3 4 3 5% 9% 65%	1520
July	1st to 10th	Night	5% 4 2 4 4 4 4 4 7% 8% 55%	2540
	11th to 20th	Night	2 2 1 3 3 3 5% 4 8% 11% 58%	2540
	21st to end	Night	4 2 1 5% 3 5% 5% 5% 6% 8% 56%	2761
August	1st to 10th	Night	10% 4 2 5% 3 3 4 3 6% 9% 50%	2702
	11th to 20th	Night	2 2 1 6% 5% 6% 6% 5% 7% 8% 51%	3012
	21st to end	Night	3 3 1 4 2 4 3 4 6% 9% 61%	3487
September	1st to 10th	Night	6% 4 1 4 3 3 3 2 4 7% 63%	1900
	11th to 20th	Night	5% 4 2 4 3 3 3 3 4 7% 61%	1921
	21st to end	Night	8% 4 1 3 3 3 3 2 3 5% 65%	2090
October	1st to 10th	Night	5% 4 1 2 2 2 2 2 3 4 73%	3790
	11th to 20th	Night	7% 4 1 4 4 3 4 4 5% 7% 57%	3778
	21st to end	Night	6% 6% 2 4 3 3 4 3 6% 9% 55%	4327
November	1st to 10th	Night	4 6% 2 5% 4 3 4 4 6% 8% 53%	2535
	11th to 20th	Night	3 5% 2 5% 4 4 4 4 7% 9% 52%	2620
	21st to end	Night	3 7% 2 5% 4 3 3 3 7% 7% 56%	2800
December	1st to 10th	Night	2 5% 2 5% 3 3 4 3 4 6% 63%	4570
	11th to 20th	Night	2 7% 2 6% 4 4 4 4 6% 9% 53%	5181
	21st to end	Night	3 7% 3 8% 5% 5% 5% 4 7% 9% 44%	6974

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	34% 8% 15% 26% 17% 1	3639
	11th to 20th	Day	37% 8% 17% 20% 16% 1	3640
	21st to end	Day	22% 5% 16% 30% 21% 6%	4341
February	1st to 10th	Day	36% 6% 17% 24% 15% 2	1800
	11th to 20th	Day	37% 7% 12% 24% 15% 5%	1875
	21st to end	Day	30% 5% 15% 25% 18% 6%	1650
March	1st to 10th	Day	30% 4 8% 28% 23% 6%	4500
	11th to 20th	Day	28% 7% 15% 27% 22% 2	4878
	21st to end	Day	34% 9% 15% 29% 12% 1	5850
April	1st to 10th	Day	32% 6% 17% 25% 15% 4	2400
	11th to 20th	Day	41% 7% 12% 20% 16% 4	2255
	21st to end	Day	37% 6% 13% 27% 16% 1	2299
May	1st to 10th	Day	44% 7% 12% 21% 12% 3	4289
	11th to 20th	Day	32% 9% 13% 28% 14% 4	4392
	21st to end	Day	31% 8% 16% 28% 13% 3	4825
June	1st to 10th	Day	25% 9% 18% 26% 17% 5%	2660
	11th to 20th	Day	26% 7% 14% 22% 20% 11%	2660
	21st to end	Day	20% 7% 11% 24% 27% 13%	2660
July	1st to 10th	Day	17% 6% 8% 20% 30% 19%	4361
	11th to 20th	Day	18% 6% 9% 23% 25% 19%	4355
	21st to end	Day	18% 7% 10% 18% 23% 24%	4651
August	1st to 10th	Day	24% 8% 11% 23% 22% 12%	4219
	11th to 20th	Day	22% 7% 9% 20% 25% 16%	3865
	21st to end	Day	18% 5% 9% 17% 28% 23%	4179
September	1st to 10th	Day	22% 4 9% 19% 28% 18%	2280
	11th to 20th	Day	20% 5% 9% 22% 29% 16%	2258
	21st to end	Day	20% 4 7% 28% 31% 9%	2090
October	1st to 10th	Day	17% 3 7% 18% 30% 25%	3175
	11th to 20th	Day	25% 4 11% 28% 25% 7%	3150
	21st to end	Day	26% 5% 10% 34% 22% 4	3200
November	1st to 10th	Day	24% 7% 14% 26% 22% 7%	1763
	11th to 20th	Day	21% 5% 15% 30% 24% 5%	1776
	21st to end	Day	28% 6% 14% 25% 24% 4	1600
December	1st to 10th	Day	20% 5% 15% 34% 24% 2	2620
	11th to 20th	Day	22% 5% 16% 39% 16% 2	3024
	21st to end	Day	32% 7% 13% 33% 14% 2	4004
January	1st to 10th	Night	34% 10% 12% 27% 14% 3	6327
	11th to 20th	Night	34% 8% 17% 20% 18% 3	6340
	21st to end	Night	28% 7% 16% 30% 17% 3	6680
February	1st to 10th	Night	34% 7% 18% 25% 13% 3	2600
	11th to 20th	Night	36% 7% 15% 23% 14% 4	2421
	21st to end	Night	31% 5% 14% 26% 20% 4	1980
March	1st to 10th	Night	30% 5% 8% 27% 23% 6%	5374
	11th to 20th	Night	26% 6% 15% 24% 27% 2	5101
	21st to end	Night	39% 9% 19% 21% 11% 1	5107
April	1st to 10th	Night	34% 8% 13% 25% 16% 5%	2000
	11th to 20th	Night	39% 7% 12% 22% 16% 4	1882
	21st to end	Night	39% 8% 11% 25% 16% 1	1881
May	1st to 10th	Night	38% 7% 13% 22% 17% 2	2678
	11th to 20th	Night	28% 9% 14% 33% 12% 4	2518
	21st to end	Night	31% 8% 19% 26% 13% 3	2762
June	1st to 10th	Night	24% 9% 23% 25% 14% 4	1520
	11th to 20th	Night	23% 6% 16% 25% 21% 8%	1520
	21st to end	Night	17% 6% 14% 28% 24% 11%	1520
July	1st to 10th	Night	24% 8% 10% 24% 20% 14%	2500
	11th to 20th	Night	17% 8% 17% 25% 23% 11%	2492
	21st to end	Night	22% 8% 12% 20% 25% 13%	2674
August	1st to 10th	Night	29% 7% 13% 25% 17% 8%	2694
	11th to 20th	Night	26% 8% 13% 23% 18% 12%	3040
	21st to end	Night	19% 5% 12% 19% 28% 17%	3487
September	1st to 10th	Night	23% 3 7% 23% 29% 15%	1900
	11th to 20th	Night	22% 5% 8% 24% 26% 15%	1921
	21st to end	Night	23% 3 8% 25% 27% 14%	2090
October	1st to 10th	Night	16% 4 7% 19% 30% 24%	3790
	11th to 20th	Night	26% 5% 12% 26% 25% 6%	3778
	21st to end	Night	25% 4 13% 28% 21% 9%	4327
November	1st to 10th	Night	27% 6% 14% 24% 23% 5%	2535
	11th to 20th	Night	26% 6% 12% 29% 21% 5%	2620
	21st to end	Night	26% 5% 12% 31% 22% 5%	2800
December	1st to 10th	Night	23% 5% 15% 35% 19% 3	4570
	11th to 20th	Night	27% 5% 14% 40% 13% 1	5182
	21st to end	Night	33% 8% 13% 32% 13% 2	6974

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% 9% 28% 31% 17% 7%	300
	11th to 20th	Day	9% 16% 30% 31% 13% 2	300
	21st to end	Day	7% 9% 39% 33% 8% 4	330
February	1st to 10th	Day	9% 15% 44% 23% 9%	300
	11th to 20th	Day	7% 16% 36% 33% 8%	300
	21st to end	Day	8% 17% 36% 29% 9% 1	249
March	1st to 10th	Day	9% 18% 25% 32% 15% 1	300
	11th to 20th	Day	12% 14% 40% 22% 11% 2	443
	21st to end	Day	14% 17% 31% 27% 9% 2	550
April	1st to 10th	Day	14% 19% 34% 21% 10% 2	500
	11th to 20th	Day	17% 21% 34% 21% 8% 1	453
	21st to end	Day	14% 11% 30% 29% 13% 3	479
May	1st to 10th	Day	14% 13% 29% 28% 13% 3	653
	11th to 20th	Day	16% 12% 23% 28% 17% 5%	675
	21st to end	Day	12% 9% 27% 30% 17% 4	734
June	1st to 10th	Day	4 8% 26% 31% 21% 9%	680
	11th to 20th	Day	9% 9% 32% 33% 14% 2	680
	21st to end	Day	6% 4 29% 32% 24% 4	680
July	1st to 10th	Day	4 4 19% 36% 31% 6%	671
	11th to 20th	Day	3 3 22% 39% 27% 7%	668
	21st to end	Day	5% 2 19% 35% 32% 7%	739
August	1st to 10th	Day	6% 4 20% 35% 28% 7%	577
	11th to 20th	Day	5% 5% 21% 32% 27% 11%	477
	21st to end	Day	4 6% 24% 34% 24% 9%	539
September	1st to 10th	Day	8% 6% 23% 30% 26% 9%	490
	11th to 20th	Day	5% 7% 27% 26% 23% 11%	468
	21st to end	Day	6% 8% 26% 30% 17% 13%	300
October	1st to 10th	Day	8% 8% 22% 27% 22% 13%	300
	11th to 20th	Day	10% 11% 29% 26% 17% 6%	300
	21st to end	Day	10% 15% 29% 27% 15% 4	330
November	1st to 10th	Day	7% 12% 29% 32% 14% 5%	300
	11th to 20th	Day	9% 13% 36% 30% 11% 2	300
	21st to end	Day	7% 10% 36% 30% 13% 4	300
December	1st to 10th	Day	5% 15% 34% 29% 15% 2	300
	11th to 20th	Day	7% 14% 36% 33% 10%	300
	21st to end	Day	11% 15% 31% 27% 13% 2	330
January	1st to 10th	Night	5% 13% 35% 34% 13% 1	1000
	11th to 20th	Night	5% 17% 38% 31% 8% 1	1000
	21st to end	Night	8% 10% 38% 36% 9%	975
February	1st to 10th	Night	6% 11% 42% 34% 8%	800
	11th to 20th	Night	7% 10% 39% 35% 8% 1	784
	21st to end	Night	5% 10% 45% 33% 7%	660
March	1st to 10th	Night	8% 11% 37% 35% 8%	800
	11th to 20th	Night	9% 7% 35% 40% 8% 1	800
	21st to end	Night	11% 11% 35% 36% 7%	718
April	1st to 10th	Night	13% 14% 32% 37% 5%	600
	11th to 20th	Night	13% 11% 38% 32% 6%	565
	21st to end	Night	16% 9% 31% 31% 12%	570
May	1st to 10th	Night	15% 10% 29% 32% 13% 1	570
	11th to 20th	Night	14% 7% 29% 35% 14% 2	561
	21st to end	Night	12% 8% 31% 35% 14%	617
June	1st to 10th	Night	5% 6% 33% 38% 16% 1	570
	11th to 20th	Night	9% 7% 38% 38% 8%	570
	21st to end	Night	4 4 31% 46% 15%	570
July	1st to 10th	Night	7% 4 26% 43% 19% 1	555
	11th to 20th	Night	3 3 25% 51% 17% 1	552
	21st to end	Night	5% 1 22% 52% 20%	624
August	1st to 10th	Night	5% 2 21% 53% 19%	567
	11th to 20th	Night	3 2 26% 48% 20%	564
	21st to end	Night	4 4 23% 46% 23% 1	627
September	1st to 10th	Night	7% 3 22% 46% 21% 1	570
	11th to 20th	Night	6% 5% 28% 39% 21% 2	570
	21st to end	Night	9% 6% 28% 42% 14% 1	570
October	1st to 10th	Night	12% 5% 28% 34% 18% 2	750
	11th to 20th	Night	9% 6% 31% 40% 13%	760
	21st to end	Night	9% 8% 35% 36% 11% 1	955
November	1st to 10th	Night	8% 7% 34% 38% 12% 1	975
	11th to 20th	Night	5% 13% 37% 37% 7% 1	1000
	21st to end	Night	6% 9% 35% 41% 9% 1	1000
December	1st to 10th	Night	6% 12% 40% 34% 8%	1000
	11th to 20th	Night	7% 10% 41% 36% 7%	1000
	21st to end	Night	10% 14% 35% 34% 7%	1100

Page generated at 2025-04-08 07:17:24. Version ac07

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