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 2024-02-20.

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 4 4 3 5% 5% 6% 8% 52%	78375
	Night	5% 5% 2 5% 5% 3 4 5% 6% 8% 53%	80882
Transparency	Day	28% 7% 14% 25% 19% 7%	78078
	Night	29% 7% 14% 27% 18% 6%	80701
Seeing	Day	9% 10% 28% 30% 18% 5%	14731
	Night	8% 8% 33% 38% 12% 1	24923

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 7% 7% 3 5% 4 5% 7% 51%	2538
	11th to 20th	Day	2 6% 4 7% 6% 4 6% 7% 7% 8% 44%	2540
	21st to end	Day	2 4 2 4 3 2 4 4 5% 8% 61%	3019
February	1st to 10th	Day	2 10% 4 7% 6% 2 5% 4 6% 9% 44%	1710
	11th to 20th	Day	3 8% 4 6% 6% 3 6% 6% 5% 8% 46%	1760
	21st to end	Day	4 8% 3 5% 5% 3 4 5% 5% 7% 52%	1480
March	1st to 10th	Day	4 8% 3 5% 4 2 3 5% 5% 8% 53%	1800
	11th to 20th	Day	6% 6% 2 5% 6% 2 5% 5% 5% 8% 50%	1928
	21st to end	Day	8% 6% 3 5% 6% 3 4 5% 6% 9% 45%	2322
April	1st to 10th	Day	8% 7% 3 5% 4 2 4 5% 5% 10% 48%	2160
	11th to 20th	Day	11% 9% 3 6% 6% 3 5% 5% 6% 7% 39%	2131
	21st to end	Day	9% 7% 3 6% 5% 3 5% 5% 6% 7% 43%	2178
May	1st to 10th	Day	10% 7% 3 7% 6% 3 5% 5% 6% 9% 39%	2431
	11th to 20th	Day	12% 7% 2 5% 5% 3 7% 6% 7% 8% 37%	2478
	21st to end	Day	10% 5% 2 5% 6% 4 6% 6% 7% 8% 40%	2724
June	1st to 10th	Day	5% 3 2 4 4 3 5% 6% 8% 11% 50%	2520
	11th to 20th	Day	7% 5% 1 3 3 3 4 6% 8% 9% 52%	2520
	21st to end	Day	4 2 1 2 3 3 5% 5% 7% 9% 58%	2520
July	1st to 10th	Day	4 3 1 3 4 3 5% 6% 9% 9% 53%	2520
	11th to 20th	Day	3 2 2 3 4 3 5% 6% 7% 9% 58%	2520
	21st to end	Day	4 4 1 3 3 2 6% 6% 8% 11% 52%	2742
August	1st to 10th	Day	3 2 1 3 4 3 5% 7% 8% 10% 53%	2414
	11th to 20th	Day	4 3 2 3 4 2 5% 5% 6% 8% 59%	2188
	21st to end	Day	4 3 1 3 4 2 4 5% 6% 8% 60%	2376
September	1st to 10th	Day	6% 4 1 3 3 2 4 4 5% 6% 62%	2160
	11th to 20th	Day	6% 3 1 2 3 2 3 4 4 9% 62%	2140
	21st to end	Day	6% 4 2 2 3 2 3 3 5% 7% 64%	1980
October	1st to 10th	Day	9% 5% 2 3 4 3 4 3 5% 7% 55%	1805
	11th to 20th	Day	6% 4 2 4 4 2 4 4 4 8% 58%	1800
	21st to end	Day	5% 6% 2 4 4 2 3 5% 5% 8% 57%	1850
November	1st to 10th	Day	3 4 2 4 4 3 4 5% 6% 8% 57%	1673
	11th to 20th	Day	4 4 2 3 3 3 4 4 7% 8% 58%	1688
	21st to end	Day	3 6% 3 5% 4 3 3 6% 5% 8% 54%	1520
December	1st to 10th	Day	2 6% 4 4 5% 3 5% 5% 6% 10% 51%	1520
	11th to 20th	Day	3 5% 2 4 4 2 4 5% 6% 9% 57%	1926
	21st to end	Day	2 7% 3 6% 6% 3 5% 5% 5% 7% 51%	2794
January	1st to 10th	Night	2 5% 3 7% 6% 3 5% 6% 6% 8% 49%	4417
	11th to 20th	Night	1 6% 4 8% 5% 3 4 4 6% 8% 51%	4430
	21st to end	Night	2 5% 3 6% 5% 3 4 5% 5% 11% 52%	4677
February	1st to 10th	Night	3 6% 3 7% 6% 3 6% 5% 6% 9% 45%	2470
	11th to 20th	Night	3 8% 3 6% 6% 3 6% 6% 6% 8% 46%	2290
	21st to end	Night	2 7% 3 6% 5% 4 4 5% 6% 7% 49%	1776
March	1st to 10th	Night	5% 7% 3 5% 4 3 5% 4 6% 7% 52%	2160
	11th to 20th	Night	6% 6% 3 4 4 3 5% 4 6% 8% 50%	2029
	21st to end	Night	6% 8% 4 7% 5% 3 5% 5% 6% 7% 44%	2033
April	1st to 10th	Night	11% 6% 3 5% 5% 3 4 4 6% 7% 48%	1800
	11th to 20th	Night	10% 7% 3 7% 6% 3 4 5% 5% 7% 43%	1777
	21st to end	Night	12% 6% 3 6% 5% 2 4 4 5% 7% 44%	1782
May	1st to 10th	Night	11% 6% 3 4 5% 3 5% 5% 5% 7% 46%	1526
	11th to 20th	Night	11% 6% 2 5% 4 2 4 5% 5% 8% 47%	1417
	21st to end	Night	11% 3 2 5% 4 3 5% 5% 6% 10% 46%	1552
June	1st to 10th	Night	4 3 1 4 4 3 5% 5% 8% 9% 53%	1440
	11th to 20th	Night	8% 4 1 4 2 2 3 4 6% 10% 56%	1440
	21st to end	Night	3 2 1 3 3 2 4 4 5% 8% 66%	1440
July	1st to 10th	Night	5% 3 2 3 3 2 4 5% 7% 10% 56%	1440
	11th to 20th	Night	3 2 1 2 3 2 4 4 6% 9% 65%	1440
	21st to end	Night	4 2 1 3 4 4 4 6% 7% 9% 58%	1576
August	1st to 10th	Night	3 3 2 4 4 3 5% 5% 8% 11% 54%	1522
	11th to 20th	Night	3 2 2 4 5% 2 4 4 5% 8% 61%	1713
	21st to end	Night	3 4 1 3 4 3 4 5% 6% 7% 60%	1980
September	1st to 10th	Night	6% 4 2 3 4 3 2 3 4 7% 63%	1800
	11th to 20th	Night	5% 4 2 4 3 3 3 3 4 7% 61%	1819
	21st to end	Night	8% 4 1 3 3 2 3 3 3 5% 65%	1980
October	1st to 10th	Night	9% 6% 2 3 3 2 3 4 5% 7% 55%	2150
	11th to 20th	Night	8% 5% 2 4 4 2 4 4 5% 6% 57%	2160
	21st to end	Night	6% 6% 2 5% 4 3 4 4 5% 7% 55%	2488
November	1st to 10th	Night	4 5% 2 4 5% 2 4 5% 6% 8% 53%	2405
	11th to 20th	Night	3 5% 2 4 5% 3 4 6% 6% 9% 52%	2489
	21st to end	Night	3 7% 2 4 4 2 4 3 7% 8% 56%	2660
December	1st to 10th	Night	3 6% 3 6% 4 3 4 4 5% 8% 52%	2660
	11th to 20th	Night	3 6% 2 4 4 3 4 5% 6% 10% 55%	3271
	21st to end	Night	3 7% 3 7% 6% 4 5% 5% 5% 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% 8% 13% 24% 15% 5%	1769
	21st to end	Day	32% 5% 16% 25% 16% 6%	1480
March	1st to 10th	Day	30% 5% 13% 30% 19% 3	1800
	11th to 20th	Day	31% 7% 14% 28% 17% 3	1928
	21st to end	Day	35% 8% 14% 28% 13% 2	2322
April	1st to 10th	Day	32% 6% 18% 25% 14% 5%	2160
	11th to 20th	Day	42% 7% 12% 20% 16% 3	2134
	21st to end	Day	38% 6% 12% 27% 16% 1	2178
May	1st to 10th	Day	40% 7% 13% 25% 13% 2	2431
	11th to 20th	Day	41% 10% 14% 22% 11% 1	2482
	21st to end	Day	37% 10% 17% 21% 13% 2	2724
June	1st to 10th	Day	25% 9% 18% 26% 17% 5%	2520
	11th to 20th	Day	27% 6% 14% 22% 20% 11%	2520
	21st to end	Day	20% 6% 11% 24% 27% 12%	2520
July	1st to 10th	Day	24% 7% 12% 22% 24% 11%	2451
	11th to 20th	Day	21% 6% 10% 22% 22% 19%	2445
	21st to end	Day	22% 8% 12% 24% 21% 13%	2590
August	1st to 10th	Day	22% 9% 13% 26% 20% 10%	2398
	11th to 20th	Day	21% 6% 11% 25% 23% 14%	2188
	21st to end	Day	19% 5% 9% 19% 30% 17%	2376
September	1st to 10th	Day	23% 4 9% 19% 27% 19%	2160
	11th to 20th	Day	20% 5% 9% 23% 28% 16%	2140
	21st to end	Day	21% 4 8% 28% 31% 8%	1980
October	1st to 10th	Day	29% 5% 10% 27% 21% 7%	1805
	11th to 20th	Day	25% 5% 13% 27% 22% 8%	1800
	21st to end	Day	24% 5% 14% 31% 19% 6%	1850
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% 16% 24% 15% 4	2291
	21st to end	Night	32% 6% 15% 25% 18% 4	1776
March	1st to 10th	Night	31% 5% 11% 28% 20% 4	2160
	11th to 20th	Night	30% 7% 15% 26% 18% 4	2029
	21st to end	Night	37% 7% 15% 25% 14% 2	2033
April	1st to 10th	Night	35% 8% 13% 24% 15% 5%	1800
	11th to 20th	Night	39% 7% 13% 22% 15% 4	1777
	21st to end	Night	40% 7% 10% 25% 16% 1	1782
May	1st to 10th	Night	37% 7% 14% 25% 16% 1	1526
	11th to 20th	Night	36% 9% 16% 27% 11% 2	1418
	21st to end	Night	33% 9% 17% 25% 14% 2	1552
June	1st to 10th	Night	25% 9% 23% 24% 14% 5%	1440
	11th to 20th	Night	23% 6% 15% 26% 21% 9%	1440
	21st to end	Night	16% 6% 14% 29% 25% 11%	1440
July	1st to 10th	Night	23% 7% 12% 29% 20% 9%	1400
	11th to 20th	Night	17% 6% 11% 25% 23% 17%	1392
	21st to end	Night	21% 7% 15% 25% 22% 10%	1488
August	1st to 10th	Night	21% 8% 16% 30% 16% 9%	1514
	11th to 20th	Night	22% 5% 12% 26% 22% 13%	1713
	21st to end	Night	22% 6% 9% 20% 28% 16%	1980
September	1st to 10th	Night	23% 3 7% 23% 28% 15%	1800
	11th to 20th	Night	23% 5% 8% 24% 25% 15%	1819
	21st to end	Night	24% 3 8% 27% 26% 12%	1980
October	1st to 10th	Night	29% 6% 12% 22% 25% 6%	2150
	11th to 20th	Night	28% 4 11% 26% 22% 9%	2160
	21st to end	Night	29% 5% 14% 27% 18% 8%	2488
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% 15% 34% 34% 8%	267
	21st to end	Day	8% 15% 37% 32% 8% 1	198
March	1st to 10th	Day	9% 17% 26% 35% 13%	240
	11th to 20th	Day	13% 12% 40% 22% 11% 2	368
	21st to end	Day	15% 15% 33% 26% 9% 2	462
April	1st to 10th	Day	15% 20% 33% 20% 10% 2	420
	11th to 20th	Day	18% 21% 33% 21% 6% 1	412
	21st to end	Day	16% 12% 30% 28% 12% 3	438
May	1st to 10th	Day	14% 13% 28% 29% 13% 3	603
	11th to 20th	Day	17% 12% 22% 28% 17% 4	625
	21st to end	Day	13% 9% 27% 30% 17% 4	679
June	1st to 10th	Day	5% 7% 25% 31% 23% 9%	630
	11th to 20th	Day	9% 8% 32% 33% 15% 2	630
	21st to end	Day	6% 3 29% 33% 25% 4	630
July	1st to 10th	Day	4 4 18% 36% 32% 6%	621
	11th to 20th	Day	3 3 22% 39% 27% 6%	618
	21st to end	Day	5% 2 19% 36% 32% 6%	684
August	1st to 10th	Day	6% 4 20% 35% 29% 7%	533
	11th to 20th	Day	5% 5% 18% 33% 28% 11%	437
	21st to end	Day	4 6% 23% 34% 23% 10%	495
September	1st to 10th	Day	8% 6% 24% 29% 25% 8%	450
	11th to 20th	Day	6% 6% 28% 26% 24% 11%	430
	21st to end	Day	7% 7% 26% 30% 17% 13%	270
October	1st to 10th	Day	9% 9% 23% 26% 20% 14%	270
	11th to 20th	Day	10% 12% 30% 25% 16% 7%	270
	21st to end	Day	9% 15% 30% 26% 16% 4	297
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	742
	21st to end	Night	5% 10% 45% 33% 7%	592
March	1st to 10th	Night	8% 11% 38% 35% 8%	720
	11th to 20th	Night	9% 7% 35% 41% 8% 1	720
	21st to end	Night	11% 10% 35% 36% 8%	647
April	1st to 10th	Night	13% 14% 31% 37% 4	540
	11th to 20th	Night	13% 11% 39% 32% 6%	533
	21st to end	Night	16% 9% 30% 31% 13%	540
May	1st to 10th	Night	14% 9% 28% 33% 13% 1	540
	11th to 20th	Night	15% 6% 29% 35% 13% 2	531
	21st to end	Night	12% 7% 31% 35% 15%	584
June	1st to 10th	Night	6% 6% 31% 38% 17% 1	540
	11th to 20th	Night	9% 6% 37% 39% 8%	540
	21st to end	Night	4 3 32% 46% 16%	540
July	1st to 10th	Night	7% 3 25% 45% 20% 1	525
	11th to 20th	Night	3 3 26% 51% 17% 1	522
	21st to end	Night	5% 1 22% 51% 21% 1	591
August	1st to 10th	Night	4 2 21% 54% 19%	537
	11th to 20th	Night	4 2 25% 48% 21%	534
	21st to end	Night	4 4 22% 45% 24% 1	594
September	1st to 10th	Night	7% 3 23% 45% 21% 1	540
	11th to 20th	Night	6% 5% 27% 39% 21% 2	540
	21st to end	Night	9% 6% 29% 41% 14% 1	540
October	1st to 10th	Night	12% 6% 29% 33% 17% 2	710
	11th to 20th	Night	10% 6% 32% 39% 13%	720
	21st to end	Night	9% 8% 35% 36% 12% 1	904
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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