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 2024-10-24.

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% 52%	101421
	Night	5% 6% 2 6% 4 4 4 4 6% 8% 52%	97591
Transparency	Day	27% 7% 13% 25% 20% 9%	101163
	Night	29% 7% 14% 26% 18% 6%	97439
Seeing	Day	9% 10% 28% 30% 18% 5%	15759
	Night	8% 9% 33% 38% 12% 1	25717

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 6% 3 8% 6% 4 4 3 6% 7% 51%	2538
	11th to 20th	Day	2 6% 3 8% 5% 6% 5% 5% 7% 8% 44%	2540
	21st to end	Day	2 5% 2 5% 3 3 4 3 5% 8% 61%	3019
February	1st to 10th	Day	2 10% 4 7% 5% 3 5% 3 7% 9% 43%	1710
	11th to 20th	Day	3 8% 3 6% 5% 4 7% 4 5% 8% 46%	1770
	21st to end	Day	4 8% 2 6% 4 3 4 4 5% 7% 52%	1570
March	1st to 10th	Day	3 8% 3 7% 4 4 3 3 5% 7% 54%	3130
	11th to 20th	Day	5% 6% 2 6% 4 3 4 4 4 7% 56%	3410
	21st to end	Day	7% 8% 3 9% 6% 4 5% 4 7% 9% 39%	4085
April	1st to 10th	Day	8% 8% 2 5% 4 4 4 4 6% 9% 47%	2280
	11th to 20th	Day	11% 9% 3 6% 5% 4 5% 4 6% 7% 39%	2251
	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	8% 5% 2 4 3 3 3 2 5% 7% 57%	1905
	11th to 20th	Day	6% 5% 1 5% 3 3 4 3 4 7% 59%	1900
	21st to end	Day	5% 6% 2 5% 3 2 3 4 5% 8% 57%	1880
November	1st to 10th	Day	3 5% 2 5% 3 3 5% 4 6% 8% 56%	1673
	11th to 20th	Day	3 4 2 4 3 4 4 4 7% 8% 57%	1688
	21st to end	Day	2 7% 3 6% 4 4 4 4 5% 8% 54%	1520
December	1st to 10th	Day	2 7% 3 5% 4 4 5% 4 6% 10% 50%	1520
	11th to 20th	Day	3 5% 2 5% 3 3 5% 4 6% 8% 56%	1926
	21st to end	Day	2 8% 3 7% 5% 4 5% 4 6% 7% 51%	2794
January	1st to 10th	Night	2 5% 3 9% 5% 4 5% 5% 6% 8% 49%	4417
	11th to 20th	Night	1 6% 4 9% 5% 4 4 4 6% 8% 51%	4430
	21st to end	Night	2 5% 2 6% 4 4 5% 4 5% 11% 52%	4677
February	1st to 10th	Night	3 7% 3 8% 6% 5% 6% 4 6% 9% 44%	2470
	11th to 20th	Night	3 8% 3 7% 5% 4 6% 4 7% 8% 45%	2296
	21st to end	Night	2 7% 3 7% 5% 6% 4 4 6% 7% 49%	1884
March	1st to 10th	Night	3 8% 3 6% 4 4 4 3 6% 7% 53%	3734
	11th to 20th	Night	5% 8% 3 5% 4 4 4 3 5% 7% 54%	3565
	21st to end	Night	7% 9% 4 10% 5% 4 4 4 6% 7% 40%	3558
April	1st to 10th	Night	10% 7% 2 5% 5% 4 4 3 7% 7% 47%	1900
	11th to 20th	Night	10% 8% 3 7% 5% 4 4 4 5% 7% 43%	1877
	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	9% 6% 2 4 3 3 4 3 5% 6% 57%	2270
	11th to 20th	Night	7% 5% 2 4 4 3 3 3 5% 6% 57%	2280
	21st to end	Night	6% 6% 2 5% 3 3 4 3 5% 7% 55%	2524
November	1st to 10th	Night	4 5% 1 5% 4 3 4 4 6% 8% 53%	2405
	11th to 20th	Night	3 5% 2 5% 4 4 4 4 7% 9% 52%	2489
	21st to end	Night	3 7% 2 5% 4 3 3 3 7% 7% 56%	2660
December	1st to 10th	Night	3 6% 2 7% 4 4 4 3 6% 8% 52%	2660
	11th to 20th	Night	3 6% 2 5% 4 3 4 4 6% 10% 55%	3271
	21st to end	Night	3 8% 3 8% 5% 5% 4 4 6% 8% 47%	4873

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	30% 7% 15% 26% 21% 1	2539
	11th to 20th	Day	34% 9% 21% 20% 15% 2	2540
	21st to end	Day	22% 5% 18% 35% 15% 4	3019
February	1st to 10th	Day	37% 6% 18% 24% 14% 2	1710
	11th to 20th	Day	35% 7% 13% 24% 16% 5%	1779
	21st to end	Day	31% 5% 15% 24% 18% 6%	1570
March	1st to 10th	Day	28% 4 11% 27% 24% 5%	3130
	11th to 20th	Day	27% 7% 20% 31% 13% 2	3410
	21st to end	Day	37% 10% 15% 28% 9% 1	4085
April	1st to 10th	Day	32% 6% 18% 25% 15% 4	2280
	11th to 20th	Day	41% 7% 12% 20% 16% 4	2254
	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	28% 5% 10% 26% 22% 10%	1905
	11th to 20th	Day	25% 5% 12% 27% 22% 8%	1900
	21st to end	Day	24% 5% 14% 32% 19% 6%	1880
November	1st to 10th	Day	24% 7% 14% 26% 22% 7%	1673
	11th to 20th	Day	22% 5% 15% 31% 22% 4	1688
	21st to end	Day	28% 5% 14% 25% 24% 4	1520
December	1st to 10th	Day	27% 8% 19% 25% 19% 3	1520
	11th to 20th	Day	25% 6% 14% 38% 16% 1	1924
	21st to end	Day	32% 6% 14% 31% 14% 3	2794
January	1st to 10th	Night	30% 9% 11% 34% 14% 2	4417
	11th to 20th	Night	30% 8% 20% 20% 18% 4	4430
	21st to end	Night	26% 8% 21% 31% 11% 2	4677
February	1st to 10th	Night	34% 7% 18% 25% 13% 2	2470
	11th to 20th	Night	34% 7% 15% 24% 15% 4	2297
	21st to end	Night	32% 6% 14% 25% 19% 4	1884
March	1st to 10th	Night	29% 5% 9% 29% 23% 5%	3734
	11th to 20th	Night	29% 6% 20% 26% 17% 2	3565
	21st to end	Night	40% 10% 18% 22% 9% 1	3558
April	1st to 10th	Night	35% 8% 14% 23% 15% 5%	1900
	11th to 20th	Night	39% 7% 12% 22% 16% 4	1877
	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	27% 6% 12% 21% 25% 8%	2270
	11th to 20th	Night	28% 4 11% 27% 22% 9%	2280
	21st to end	Night	28% 5% 14% 27% 19% 8%	2524
November	1st to 10th	Night	27% 6% 14% 24% 23% 6%	2405
	11th to 20th	Night	27% 6% 13% 30% 20% 5%	2489
	21st to end	Night	26% 5% 12% 30% 22% 5%	2660
December	1st to 10th	Night	29% 6% 16% 27% 18% 4	2660
	11th to 20th	Night	25% 5% 16% 38% 14% 1	3272
	21st to end	Night	34% 7% 13% 30% 14% 2	4873

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	9% 9% 28% 30% 18% 8%	270
	11th to 20th	Day	9% 15% 29% 31% 13% 2	270
	21st to end	Day	7% 9% 39% 32% 9% 4	297
February	1st to 10th	Day	8% 15% 43% 23% 10%	270
	11th to 20th	Day	7% 16% 36% 34% 8%	270
	21st to end	Day	8% 16% 36% 32% 8%	225
March	1st to 10th	Day	8% 19% 27% 33% 13%	270
	11th to 20th	Day	12% 12% 40% 23% 11% 1	406
	21st to end	Day	14% 16% 32% 27% 9% 2	506
April	1st to 10th	Day	14% 20% 33% 21% 10% 2	460
	11th to 20th	Day	17% 21% 34% 21% 7% 1	452
	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	9% 15% 29% 27% 16% 4	306
November	1st to 10th	Day	7% 11% 29% 32% 16% 6%	270
	11th to 20th	Day	9% 13% 34% 29% 13% 2	270
	21st to end	Day	8% 10% 36% 29% 12% 4	270
December	1st to 10th	Day	5% 14% 36% 29% 13% 2	270
	11th to 20th	Day	7% 13% 36% 33% 10%	270
	21st to end	Day	11% 15% 31% 28% 13% 2	297
January	1st to 10th	Night	5% 13% 34% 34% 13% 1	950
	11th to 20th	Night	5% 17% 38% 31% 8% 1	950
	21st to end	Night	8% 9% 38% 35% 9%	927
February	1st to 10th	Night	5% 10% 42% 35% 8%	760
	11th to 20th	Night	7% 10% 38% 36% 8% 1	744
	21st to end	Night	5% 10% 45% 33% 7%	628
March	1st to 10th	Night	8% 11% 38% 35% 8%	760
	11th to 20th	Night	9% 7% 35% 41% 9% 1	760
	21st to end	Night	11% 10% 34% 36% 7%	682
April	1st to 10th	Night	14% 14% 31% 36% 5%	570
	11th to 20th	Night	13% 11% 38% 32% 6%	563
	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	916
November	1st to 10th	Night	7% 6% 34% 38% 13% 1	925
	11th to 20th	Night	5% 13% 36% 37% 7% 1	950
	21st to end	Night	6% 9% 34% 41% 9% 1	950
December	1st to 10th	Night	6% 13% 40% 34% 7%	950
	11th to 20th	Night	6% 9% 40% 37% 7%	950
	21st to end	Night	11% 14% 35% 33% 7%	1045

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