Guymon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Guymon clear sky chart from 2005-11-06 to 2026-07-31.

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	6% 4 2 4 3 3 3 3 5% 7% 61%	146912
	Night	6% 4 2 4 3 3 4 3 5% 7% 59%	143521
Transparency	Day	24% 4 9% 23% 28% 12%	141915
	Night	25% 4 9% 23% 27% 13%	139542
Seeing	Day	8% 7% 28% 34% 20% 4	17824
	Night	7% 8% 36% 38% 10%	27705

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	7% 8% 2 5% 3 3 3 3 4 6% 56%	4720
	11th to 20th	Day	2 5% 2 5% 3 2 3 2 3 5% 66%	4945
	21st to end	Day	6% 5% 2 4 3 3 3 2 4 6% 61%	6245
February	1st to 10th	Day	6% 7% 2 6% 3 3 3 3 4 5% 58%	2100
	11th to 20th	Day	5% 7% 3 6% 4 3 3 3 4 6% 56%	2049
	21st to end	Day	4 4 2 3 3 3 3 3 4 5% 66%	1730
March	1st to 10th	Day	6% 6% 2 4 3 2 3 2 3 5% 64%	4600
	11th to 20th	Day	5% 4 2 6% 3 3 3 3 5% 7% 58%	4905
	21st to end	Day	5% 4 1 4 3 3 3 4 5% 7% 61%	5809
April	1st to 10th	Day	7% 4 1 3 2 3 4 2 4 5% 65%	2520
	11th to 20th	Day	10% 4 1 4 3 2 3 3 4 6% 61%	2491
	21st to end	Day	10% 5% 1 4 3 3 3 3 5% 6% 58%	2599
May	1st to 10th	Day	12% 5% 2 4 3 3 3 3 4 6% 55%	7655
	11th to 20th	Day	4 3 1 3 2 3 3 2 4 6% 68%	7627
	21st to end	Day	11% 6% 2 5% 3 3 3 3 4 6% 53%	8404
June	1st to 10th	Day	4 3 2 4 3 4 4 4 6% 9% 56%	2753
	11th to 20th	Day	5% 3 1 3 2 3 4 3 5% 8% 63%	2940
	21st to end	Day	4 3 1 5% 3 3 4 4 6% 10% 58%	2940
July	1st to 10th	Day	5% 3 1 4 3 4 4 4 7% 10% 55%	6479
	11th to 20th	Day	4 2 1 3 2 2 2 3 5% 9% 67%	6356
	21st to end	Day	3 2 1 4 3 3 4 3 6% 9% 62%	6555
August	1st to 10th	Day	7% 4 1 5% 3 4 4 4 6% 9% 53%	5632
	11th to 20th	Day	2 3 1 3 3 3 4 3 7% 10% 61%	5366
	21st to end	Day	8% 3 1 5% 3 4 5% 4 7% 9% 50%	5984
September	1st to 10th	Day	9% 4 1 4 3 2 3 3 4 6% 59%	2379
	11th to 20th	Day	7% 3 1 3 3 3 4 3 4 6% 63%	2200
	21st to end	Day	6% 3 1 3 3 3 2 3 4 6% 66%	2200
October	1st to 10th	Day	7% 3 1 3 2 2 2 2 3 5% 71%	3590
	11th to 20th	Day	6% 4 1 4 2 3 3 3 4 5% 65%	3488
	21st to end	Day	5% 3 1 3 2 2 2 2 3 4 75%	3190
November	1st to 10th	Day	6% 3 1 3 2 2 3 2 3 6% 69%	1853
	11th to 20th	Day	4 4 1 3 2 2 2 2 4 5% 71%	1890
	21st to end	Day	6% 6% 2 3 2 3 3 2 3 6% 64%	1890
December	1st to 10th	Day	1 4 1 2 2 2 2 2 4 5% 74%	3030
	11th to 20th	Day	4 4 1 2 2 2 3 3 5% 7% 67%	3481
	21st to end	Day	6% 9% 3 6% 4 4 3 2 4 5% 53%	4317
January	1st to 10th	Night	6% 6% 2 6% 4 4 4 3 5% 5% 54%	8201
	11th to 20th	Night	2 4 2 4 3 3 3 3 4 5% 67%	8025
	21st to end	Night	7% 6% 2 5% 4 3 3 2 4 6% 57%	8027
February	1st to 10th	Night	4 7% 2 6% 3 2 3 2 5% 5% 60%	2520
	11th to 20th	Night	5% 6% 3 7% 5% 4 4 4 5% 6% 52%	2458
	21st to end	Night	5% 4 1 4 2 2 3 3 5% 6% 65%	2076
March	1st to 10th	Night	4 5% 2 4 3 2 2 2 3 5% 67%	5494
	11th to 20th	Night	5% 4 2 4 3 3 4 3 5% 7% 60%	5281
	21st to end	Night	4 4 1 4 3 3 4 3 5% 8% 60%	5369
April	1st to 10th	Night	6% 5% 1 4 3 3 3 2 4 6% 62%	2100
	11th to 20th	Night	7% 5% 2 4 3 3 3 3 5% 7% 58%	2077
	21st to end	Night	12% 4 1 4 3 3 3 2 6% 8% 55%	2019
May	1st to 10th	Night	14% 5% 2 5% 3 3 3 3 4 6% 50%	5292
	11th to 20th	Night	5% 3 1 3 2 2 3 3 5% 7% 66%	5265
	21st to end	Night	13% 6% 2 5% 3 3 4 3 5% 7% 49%	5803
June	1st to 10th	Night	4 3 1 4 3 5% 4 3 7% 11% 54%	1860
	11th to 20th	Night	4 2 1 4 4 3 4 4 7% 8% 59%	1680
	21st to end	Night	3 4 1 4 4 4 6% 4 8% 9% 54%	1680
July	1st to 10th	Night	6% 4 1 4 4 4 5% 5% 7% 10% 52%	3720
	11th to 20th	Night	3 3 2 6% 5% 4 5% 4 7% 13% 49%	3827
	21st to end	Night	4 3 2 5% 4 4 5% 5% 9% 12% 47%	4539
August	1st to 10th	Night	8% 4 2 5% 4 5% 5% 5% 8% 10% 42%	4163
	11th to 20th	Night	3 3 2 5% 4 5% 6% 5% 9% 14% 44%	4483
	21st to end	Night	12% 6% 2 6% 4 5% 5% 5% 7% 10% 39%	4993
September	1st to 10th	Night	7% 4 1 3 2 3 3 3 5% 7% 61%	2020
	11th to 20th	Night	7% 3 1 4 3 3 3 4 5% 7% 60%	2200
	21st to end	Night	6% 2 1 3 3 3 3 3 4 6% 67%	2200
October	1st to 10th	Night	6% 2 1 2 1 1 2 2 4 5% 73%	3590
	11th to 20th	Night	7% 3 2 3 3 3 4 2 5% 6% 63%	3623
	21st to end	Night	6% 3 1 3 2 2 2 2 4 4 70%	4604
November	1st to 10th	Night	5% 3 1 3 2 2 2 2 5% 6% 70%	2665
	11th to 20th	Night	2 2 1 3 2 2 3 2 4 5% 74%	2730
	21st to end	Night	7% 4 2 2 2 2 3 3 4 6% 64%	2730
December	1st to 10th	Night	3 4 1 3 2 2 2 2 4 6% 71%	4380
	11th to 20th	Night	4 3 1 3 2 2 2 2 4 6% 71%	4946
	21st to end	Night	6% 6% 2 5% 3 3 4 3 5% 7% 56%	6881

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	31% 2 6% 27% 27% 7%	4723
	11th to 20th	Day	23% 2 9% 18% 33% 16%	4945
	21st to end	Day	26% 2 7% 20% 37% 8%	6245
February	1st to 10th	Day	29% 3 9% 23% 24% 12%	2100
	11th to 20th	Day	31% 3 7% 25% 22% 11%	2059
	21st to end	Day	21% 3 4 21% 33% 18%	1730
March	1st to 10th	Day	25% 1 5% 14% 27% 27%	4600
	11th to 20th	Day	26% 3 7% 16% 30% 18%	4905
	21st to end	Day	23% 4 10% 32% 25% 6%	5809
April	1st to 10th	Day	22% 3 8% 23% 28% 16%	2520
	11th to 20th	Day	26% 4 9% 21% 24% 17%	2494
	21st to end	Day	27% 4 8% 25% 26% 9%	2599
May	1st to 10th	Day	30% 4 9% 20% 25% 11%	7655
	11th to 20th	Day	19% 3 8% 20% 26% 25%	7631
	21st to end	Day	32% 6% 10% 18% 18% 15%	8405
June	1st to 10th	Day	23% 8% 15% 25% 20% 9%	2753
	11th to 20th	Day	20% 6% 9% 21% 27% 18%	2940
	21st to end	Day	21% 5% 13% 25% 24% 12%	2940
July	1st to 10th	Day	24% 6% 14% 21% 30% 6%	6411
	11th to 20th	Day	16% 4 12% 30% 31% 7%	6281
	21st to end	Day	19% 6% 13% 33% 23% 6%	6371
August	1st to 10th	Day	26% 7% 16% 23% 24% 4	4100
	11th to 20th	Day	18% 5% 12% 24% 32% 9%	3882
	21st to end	Day	22% 5% 12% 29% 26% 7%	4311
September	1st to 10th	Day	27% 5% 9% 21% 24% 14%	2379
	11th to 20th	Day	22% 5% 8% 23% 29% 13%	2200
	21st to end	Day	21% 3 8% 25% 28% 15%	2200
October	1st to 10th	Day	18% 3 6% 15% 40% 18%	3590
	11th to 20th	Day	23% 2 7% 22% 33% 13%	3488
	21st to end	Day	16% 2 4 19% 40% 20%	3190
November	1st to 10th	Day	18% 2 8% 22% 35% 16%	1853
	11th to 20th	Day	18% 2 5% 28% 33% 13%	1890
	21st to end	Day	24% 2 7% 21% 30% 16%	1890
December	1st to 10th	Day	14% 3 8% 33% 33% 9%	3030
	11th to 20th	Day	18% 2 5% 24% 42% 9%	3479
	21st to end	Day	35% 4 7% 20% 25% 10%	4317
January	1st to 10th	Night	32% 3 6% 29% 23% 7%	8202
	11th to 20th	Night	20% 2 11% 19% 33% 14%	8025
	21st to end	Night	30% 3 8% 16% 33% 9%	8027
February	1st to 10th	Night	27% 3 8% 21% 28% 12%	2520
	11th to 20th	Night	32% 4 9% 21% 24% 11%	2458
	21st to end	Night	21% 2 4 20% 33% 20%	2076
March	1st to 10th	Night	21% 2 4 17% 26% 30%	5494
	11th to 20th	Night	23% 3 7% 15% 25% 27%	5281
	21st to end	Night	22% 4 9% 32% 25% 8%	5369
April	1st to 10th	Night	24% 3 9% 21% 26% 18%	2100
	11th to 20th	Night	26% 4 10% 22% 24% 14%	2077
	21st to end	Night	28% 5% 12% 24% 22% 9%	2019
May	1st to 10th	Night	35% 5% 10% 21% 17% 12%	5293
	11th to 20th	Night	18% 5% 9% 20% 24% 24%	5266
	21st to end	Night	35% 6% 14% 16% 12% 17%	5805
June	1st to 10th	Night	24% 7% 19% 27% 16% 7%	1860
	11th to 20th	Night	20% 8% 14% 23% 23% 13%	1680
	21st to end	Night	23% 7% 13% 26% 19% 12%	1680
July	1st to 10th	Night	26% 7% 16% 28% 20% 3	3680
	11th to 20th	Night	26% 6% 13% 26% 24% 5%	3779
	21st to end	Night	27% 6% 11% 33% 17% 6%	4410
August	1st to 10th	Night	35% 7% 13% 19% 21% 5%	3031
	11th to 20th	Night	25% 6% 13% 28% 22% 7%	3243
	21st to end	Night	29% 6% 13% 24% 24% 5%	3597
September	1st to 10th	Night	23% 6% 13% 21% 25% 13%	2020
	11th to 20th	Night	23% 5% 11% 20% 27% 13%	2200
	21st to end	Night	20% 6% 7% 23% 28% 16%	2200
October	1st to 10th	Night	15% 3 6% 15% 40% 21%	3590
	11th to 20th	Night	24% 3 7% 23% 26% 18%	3623
	21st to end	Night	20% 2 4 19% 40% 16%	4604
November	1st to 10th	Night	16% 3 9% 22% 31% 20%	2665
	11th to 20th	Night	14% 2 6% 25% 37% 16%	2730
	21st to end	Night	22% 3 7% 23% 27% 18%	2730
December	1st to 10th	Night	16% 3 7% 33% 36% 6%	4380
	11th to 20th	Night	17% 2 5% 24% 40% 13%	4947
	21st to end	Night	28% 4 8% 24% 26% 9%	6881

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	7% 7% 35% 36% 14% 1	330
	11th to 20th	Day	10% 13% 32% 29% 13% 2	330
	21st to end	Day	5% 7% 40% 29% 15% 3	363
February	1st to 10th	Day	7% 12% 42% 29% 9%	330
	11th to 20th	Day	10% 9% 43% 25% 10% 2	330
	21st to end	Day	6% 8% 49% 30% 6% 1	273
March	1st to 10th	Day	8% 8% 41% 33% 9% 1	330
	11th to 20th	Day	13% 11% 38% 26% 11% 1	330
	21st to end	Day	12% 13% 36% 27% 11% 1	458
April	1st to 10th	Day	11% 14% 39% 25% 9% 2	540
	11th to 20th	Day	10% 17% 40% 27% 6%	532
	21st to end	Day	13% 15% 40% 24% 8% 1	619
May	1st to 10th	Day	11% 10% 33% 33% 11% 1	753
	11th to 20th	Day	10% 7% 31% 34% 15% 3	775
	21st to end	Day	10% 8% 36% 31% 15% 1	844
June	1st to 10th	Day	5% 4 26% 38% 21% 6%	780
	11th to 20th	Day	6% 4 32% 36% 20% 3	780
	21st to end	Day	5% 3 26% 41% 22% 3	780
July	1st to 10th	Day	4 2 18% 38% 30% 8%	771
	11th to 20th	Day	2 1 12% 38% 36% 10%	768
	21st to end	Day	4 1 10% 39% 35% 10%	845
August	1st to 10th	Day	4 1 12% 40% 36% 7%	658
	11th to 20th	Day	3 14% 41% 34% 8%	517
	21st to end	Day	5% 1 14% 40% 29% 11%	583
September	1st to 10th	Day	10% 2 16% 37% 28% 7%	509
	11th to 20th	Day	5% 3 17% 39% 27% 9%	330
	21st to end	Day	8% 4 22% 30% 28% 7%	330
October	1st to 10th	Day	11% 6% 25% 29% 22% 7%	330
	11th to 20th	Day	6% 5% 33% 33% 17% 5%	330
	21st to end	Day	15% 9% 26% 29% 17% 5%	363
November	1st to 10th	Day	8% 8% 30% 32% 19% 3	330
	11th to 20th	Day	7% 10% 29% 35% 15% 5%	330
	21st to end	Day	11% 12% 28% 28% 15% 5%	330
December	1st to 10th	Day	4 5% 35% 38% 16% 2	330
	11th to 20th	Day	8% 8% 34% 32% 16% 2	330
	21st to end	Day	12% 14% 35% 27% 12% 1	363
January	1st to 10th	Night	6% 8% 37% 41% 8% 1	1050
	11th to 20th	Night	8% 8% 35% 37% 11% 1	1050
	21st to end	Night	7% 7% 40% 38% 8%	1024
February	1st to 10th	Night	7% 10% 37% 39% 6%	840
	11th to 20th	Night	8% 11% 48% 28% 4	824
	21st to end	Night	8% 11% 47% 31% 3	692
March	1st to 10th	Night	7% 13% 43% 33% 4	840
	11th to 20th	Night	11% 10% 40% 31% 8%	717
	21st to end	Night	10% 13% 50% 25% 2	693
April	1st to 10th	Night	9% 14% 44% 29% 3	630
	11th to 20th	Night	10% 16% 50% 22% 2	623
	21st to end	Night	13% 12% 42% 27% 6%	630
May	1st to 10th	Night	11% 10% 43% 31% 5%	630
	11th to 20th	Night	8% 8% 39% 34% 10%	621
	21st to end	Night	11% 7% 46% 30% 7%	683
June	1st to 10th	Night	4 6% 40% 39% 11%	630
	11th to 20th	Night	4 7% 48% 36% 5%	630
	21st to end	Night	3 5% 39% 42% 10%	630
July	1st to 10th	Night	5% 3 27% 46% 18% 1	615
	11th to 20th	Night	4 1 21% 49% 24%	612
	21st to end	Night	6% 1 19% 52% 21% 1	687
August	1st to 10th	Night	5% 3 19% 48% 25% 1	597
	11th to 20th	Night	7% 2 21% 50% 19% 1	594
	21st to end	Night	6% 2 22% 45% 24% 1	660
September	1st to 10th	Night	8% 1 27% 51% 13%	600
	11th to 20th	Night	8% 2 37% 43% 9% 1	600
	21st to end	Night	6% 5% 28% 47% 14%	600
October	1st to 10th	Night	10% 5% 31% 42% 12%	600
	11th to 20th	Night	7% 8% 38% 37% 10%	629
	21st to end	Night	10% 9% 32% 33% 16% 1	1094
November	1st to 10th	Night	6% 5% 33% 45% 10%	1025
	11th to 20th	Night	4 7% 39% 40% 10%	1050
	21st to end	Night	9% 9% 30% 38% 13% 1	1050
December	1st to 10th	Night	7% 6% 34% 44% 9%	1050
	11th to 20th	Night	9% 8% 38% 37% 7%	1050
	21st to end	Night	9% 11% 37% 36% 6% 1	1155

Page generated at 2026-07-28 02:25:19. Version ac07

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