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 2024-10-20.

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	6% 4 1 4 3 3 3 3 5% 7% 61%	101086
	Night	6% 4 2 4 3 3 4 3 5% 7% 58%	97774
Transparency	Day	23% 5% 10% 23% 27% 12%	100839
	Night	25% 5% 10% 23% 25% 12%	97611
Seeing	Day	8% 7% 28% 34% 20% 4	15386
	Night	7% 7% 36% 38% 11%	25274

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% 9% 3 5% 2 3 3 2 4 6% 56%	2538
	11th to 20th	Day	3 5% 2 5% 4 3 4 3 4 7% 61%	2641
	21st to end	Day	7% 7% 2 5% 3 3 3 3 4 6% 56%	3361
February	1st to 10th	Day	6% 7% 2 6% 3 3 3 3 4 6% 57%	1900
	11th to 20th	Day	4 7% 3 6% 4 3 3 3 4 6% 57%	1849
	21st to end	Day	5% 4 2 3 3 4 3 3 4 6% 64%	1570
March	1st to 10th	Day	5% 5% 1 4 2 2 2 2 3 6% 67%	3130
	11th to 20th	Day	7% 5% 2 4 3 3 3 3 5% 7% 60%	3351
	21st to end	Day	7% 6% 2 5% 4 3 4 4 5% 7% 53%	3963
April	1st to 10th	Day	6% 4 1 3 2 3 4 2 5% 5% 65%	2280
	11th to 20th	Day	10% 4 1 4 3 2 2 3 4 6% 60%	2251
	21st to end	Day	9% 5% 1 4 3 3 3 3 5% 6% 58%	2351
May	1st to 10th	Day	9% 4 2 4 3 3 3 3 4 7% 59%	4120
	11th to 20th	Day	7% 4 2 4 3 3 4 3 5% 7% 58%	4082
	21st to end	Day	6% 4 1 3 3 3 3 3 4 7% 63%	4489
June	1st to 10th	Day	4 3 2 4 3 4 4 4 6% 9% 57%	2491
	11th to 20th	Day	5% 3 1 3 2 3 4 3 5% 8% 63%	2660
	21st to end	Day	3 2 1 4 3 3 4 4 6% 10% 59%	2660
July	1st to 10th	Day	5% 3 1 4 3 4 4 4 6% 8% 57%	4430
	11th to 20th	Day	2 2 1 3 2 3 3 3 6% 9% 65%	4347
	21st to end	Day	3 2 1 4 3 3 4 4 6% 9% 61%	4466
August	1st to 10th	Day	7% 4 1 4 3 4 4 4 6% 8% 54%	3987
	11th to 20th	Day	3 3 1 3 3 3 3 3 6% 8% 63%	3726
	21st to end	Day	4 3 1 4 2 3 4 4 7% 9% 59%	4180
September	1st to 10th	Day	9% 5% 1 4 3 2 3 3 4 6% 59%	2260
	11th to 20th	Day	7% 3 1 3 3 3 4 3 4 6% 63%	2090
	21st to end	Day	6% 3 1 3 3 3 2 3 3 6% 67%	2090
October	1st to 10th	Day	11% 4 1 4 2 3 3 2 3 6% 61%	2090
	11th to 20th	Day	7% 3 1 3 2 2 2 2 3 4 72%	2038
	21st to end	Day	8% 5% 1 4 2 2 2 2 3 4 68%	1782
November	1st to 10th	Day	5% 2 1 3 2 2 3 2 4 7% 70%	1673
	11th to 20th	Day	4 4 1 3 2 2 2 2 4 5% 71%	1710
	21st to end	Day	7% 5% 2 3 2 3 2 2 3 5% 65%	1710
December	1st to 10th	Day	2 6% 2 4 3 3 3 3 6% 7% 62%	1710
	11th to 20th	Day	6% 5% 1 3 3 2 3 3 5% 7% 62%	2161
	21st to end	Day	5% 9% 3 6% 4 4 4 3 4 6% 52%	2949
January	1st to 10th	Night	5% 6% 2 5% 4 4 4 3 4 6% 56%	4417
	11th to 20th	Night	4 6% 2 5% 3 2 4 4 4 6% 61%	4309
	21st to end	Night	7% 7% 2 5% 4 3 3 2 4 7% 56%	4336
February	1st to 10th	Night	5% 8% 2 6% 4 3 3 2 5% 5% 58%	2280
	11th to 20th	Night	5% 6% 2 7% 5% 4 3 3 5% 6% 53%	2218
	21st to end	Night	6% 4 1 4 2 2 3 3 5% 6% 63%	1884
March	1st to 10th	Night	4 5% 2 4 3 3 2 2 4 5% 67%	3734
	11th to 20th	Night	7% 4 2 5% 3 3 4 3 5% 7% 57%	3611
	21st to end	Night	6% 5% 1 4 2 4 4 4 5% 7% 59%	3668
April	1st to 10th	Night	6% 4 1 4 3 3 3 2 4 6% 63%	1900
	11th to 20th	Night	7% 5% 2 4 4 3 3 3 5% 7% 58%	1877
	21st to end	Night	11% 4 1 4 3 3 3 2 6% 8% 54%	1827
May	1st to 10th	Night	9% 5% 1 5% 4 3 4 3 5% 7% 55%	2850
	11th to 20th	Night	9% 5% 2 4 4 3 4 4 6% 8% 52%	2823
	21st to end	Night	8% 4 1 4 4 3 4 4 5% 7% 56%	3098
June	1st to 10th	Night	4 2 1 4 3 5% 4 3 7% 11% 56%	1683
	11th to 20th	Night	4 2 1 4 4 3 5% 4 7% 8% 58%	1520
	21st to end	Night	3 4 1 4 3 4 6% 4 8% 10% 55%	1520
July	1st to 10th	Night	5% 3 2 4 4 4 4 4 7% 10% 52%	2540
	11th to 20th	Night	3 3 1 5% 5% 4 5% 3 8% 11% 51%	2619
	21st to end	Night	3 3 2 5% 4 4 5% 4 8% 11% 49%	3097
August	1st to 10th	Night	9% 4 2 6% 5% 6% 5% 5% 8% 9% 41%	2948
	11th to 20th	Night	4 3 2 4 3 4 5% 5% 9% 14% 46%	3113
	21st to end	Night	4 3 2 5% 4 5% 6% 6% 9% 12% 45%	3487
September	1st to 10th	Night	7% 3 1 3 2 3 3 3 5% 7% 62%	1919
	11th to 20th	Night	7% 3 1 4 3 3 3 4 5% 7% 60%	2090
	21st to end	Night	6% 2 1 3 2 3 2 3 4 5% 68%	2090
October	1st to 10th	Night	10% 4 1 4 2 2 3 3 5% 5% 62%	2090
	11th to 20th	Night	7% 3 1 2 2 2 2 2 3 4 72%	2111
	21st to end	Night	7% 4 1 3 3 2 2 2 4 4 68%	2568
November	1st to 10th	Night	4 3 1 3 2 2 2 2 5% 6% 71%	2405
	11th to 20th	Night	2 2 1 3 2 2 3 2 4 5% 73%	2470
	21st to end	Night	7% 5% 2 2 2 2 3 3 4 6% 64%	2470
December	1st to 10th	Night	4 5% 1 5% 3 3 3 3 5% 7% 61%	2470
	11th to 20th	Night	6% 5% 1 4 3 2 3 2 5% 7% 62%	3036
	21st to end	Night	5% 5% 2 5% 3 3 4 4 5% 7% 56%	4696

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% 3 7% 26% 28% 5%	2539
	11th to 20th	Day	25% 3 13% 24% 26% 9%	2641
	21st to end	Day	30% 3 9% 26% 27% 5%	3361
February	1st to 10th	Day	30% 3 10% 23% 24% 11%	1900
	11th to 20th	Day	30% 3 7% 26% 22% 12%	1859
	21st to end	Day	23% 3 5% 22% 31% 17%	1570
March	1st to 10th	Day	20% 2 7% 19% 27% 26%	3130
	11th to 20th	Day	25% 4 9% 22% 31% 9%	3351
	21st to end	Day	29% 5% 11% 25% 22% 8%	3963
April	1st to 10th	Day	22% 3 8% 23% 27% 17%	2280
	11th to 20th	Day	26% 4 9% 21% 24% 15%	2254
	21st to end	Day	27% 4 9% 25% 26% 9%	2351
May	1st to 10th	Day	26% 5% 10% 21% 20% 19%	4120
	11th to 20th	Day	26% 6% 12% 24% 24% 8%	4086
	21st to end	Day	22% 7% 11% 17% 24% 20%	4489
June	1st to 10th	Day	22% 8% 15% 26% 20% 9%	2491
	11th to 20th	Day	19% 6% 9% 20% 27% 19%	2660
	21st to end	Day	20% 5% 12% 26% 25% 12%	2660
July	1st to 10th	Day	23% 6% 11% 23% 29% 7%	4361
	11th to 20th	Day	15% 5% 13% 25% 33% 9%	4272
	21st to end	Day	19% 6% 12% 27% 28% 9%	4325
August	1st to 10th	Day	27% 7% 15% 22% 24% 4	3974
	11th to 20th	Day	19% 5% 12% 24% 32% 9%	3762
	21st to end	Day	20% 5% 11% 29% 27% 7%	4179
September	1st to 10th	Day	27% 5% 8% 21% 24% 14%	2260
	11th to 20th	Day	23% 5% 8% 22% 29% 14%	2090
	21st to end	Day	20% 3 8% 24% 29% 15%	2090
October	1st to 10th	Day	27% 5% 8% 18% 28% 13%	2090
	11th to 20th	Day	18% 2 6% 19% 33% 21%	2038
	21st to end	Day	22% 3 7% 20% 33% 15%	1782
November	1st to 10th	Day	17% 2 8% 21% 35% 16%	1673
	11th to 20th	Day	18% 2 6% 29% 33% 13%	1710
	21st to end	Day	24% 2 6% 20% 31% 18%	1710
December	1st to 10th	Day	22% 4 11% 29% 25% 8%	1710
	11th to 20th	Day	22% 4 7% 27% 31% 10%	2159
	21st to end	Day	33% 5% 8% 19% 25% 10%	2949
January	1st to 10th	Night	29% 4 9% 29% 24% 5%	4417
	11th to 20th	Night	24% 4 14% 24% 24% 9%	4309
	21st to end	Night	29% 5% 11% 21% 29% 6%	4336
February	1st to 10th	Night	28% 4 9% 21% 28% 11%	2280
	11th to 20th	Night	31% 4 8% 21% 24% 11%	2218
	21st to end	Night	23% 2 5% 21% 31% 19%	1884
March	1st to 10th	Night	21% 2 5% 21% 25% 27%	3734
	11th to 20th	Night	26% 4 9% 20% 26% 14%	3611
	21st to end	Night	24% 6% 9% 31% 20% 10%	3668
April	1st to 10th	Night	23% 3 8% 21% 26% 19%	1900
	11th to 20th	Night	27% 4 10% 22% 23% 13%	1877
	21st to end	Night	28% 5% 12% 23% 22% 9%	1827
May	1st to 10th	Night	29% 7% 12% 17% 15% 20%	2850
	11th to 20th	Night	29% 8% 13% 20% 20% 9%	2824
	21st to end	Night	27% 6% 13% 16% 17% 21%	3099
June	1st to 10th	Night	21% 7% 19% 28% 16% 8%	1683
	11th to 20th	Night	20% 9% 14% 21% 23% 13%	1520
	21st to end	Night	22% 7% 12% 26% 20% 13%	1520
July	1st to 10th	Night	25% 6% 12% 31% 22% 4	2500
	11th to 20th	Night	25% 5% 14% 22% 26% 7%	2571
	21st to end	Night	26% 6% 11% 27% 21% 9%	2999
August	1st to 10th	Night	36% 7% 12% 18% 22% 5%	2938
	11th to 20th	Night	25% 6% 13% 27% 22% 7%	3143
	21st to end	Night	28% 6% 13% 24% 24% 5%	3487
September	1st to 10th	Night	22% 5% 12% 21% 25% 14%	1919
	11th to 20th	Night	22% 6% 12% 18% 28% 14%	2090
	21st to end	Night	19% 5% 7% 23% 29% 17%	2090
October	1st to 10th	Night	24% 5% 9% 17% 28% 16%	2090
	11th to 20th	Night	19% 3 6% 17% 31% 23%	2111
	21st to end	Night	21% 2 6% 23% 30% 18%	2568
November	1st to 10th	Night	15% 2 9% 23% 29% 22%	2405
	11th to 20th	Night	14% 3 6% 26% 36% 15%	2470
	21st to end	Night	23% 3 6% 21% 29% 19%	2470
December	1st to 10th	Night	22% 4 10% 28% 27% 9%	2470
	11th to 20th	Night	23% 2 7% 25% 33% 9%	3037
	21st to end	Night	27% 5% 9% 25% 25% 9%	4696

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% 33% 38% 14% 1	270
	11th to 20th	Day	11% 12% 33% 30% 13% 1	270
	21st to end	Day	4 8% 41% 28% 15% 4	297
February	1st to 10th	Day	8% 14% 40% 30% 8%	270
	11th to 20th	Day	8% 8% 45% 26% 10% 3	270
	21st to end	Day	7% 10% 52% 27% 4	225
March	1st to 10th	Day	7% 9% 42% 34% 9%	270
	11th to 20th	Day	13% 11% 36% 26% 12% 1	270
	21st to end	Day	14% 15% 34% 26% 11% 1	382
April	1st to 10th	Day	10% 14% 41% 25% 9% 2	460
	11th to 20th	Day	11% 16% 38% 28% 6%	452
	21st to end	Day	13% 15% 39% 24% 8% 2	531
May	1st to 10th	Day	10% 11% 34% 34% 11% 1	653
	11th to 20th	Day	11% 7% 29% 34% 16% 3	675
	21st to end	Day	9% 8% 37% 30% 15% 1	734
June	1st to 10th	Day	5% 5% 26% 37% 22% 6%	680
	11th to 20th	Day	5% 4 31% 36% 20% 3	680
	21st to end	Day	4 2 24% 42% 24% 3	680
July	1st to 10th	Day	5% 2 17% 37% 31% 8%	671
	11th to 20th	Day	2 1 13% 40% 34% 9%	668
	21st to end	Day	5% 1 10% 39% 34% 11%	739
August	1st to 10th	Day	4 1 12% 40% 37% 7%	612
	11th to 20th	Day	3 15% 40% 34% 7%	477
	21st to end	Day	4 1 14% 41% 29% 11%	539
September	1st to 10th	Day	10% 2 16% 36% 29% 7%	470
	11th to 20th	Day	5% 3 17% 40% 26% 9%	300
	21st to end	Day	8% 5% 22% 31% 28% 7%	300
October	1st to 10th	Day	11% 6% 25% 28% 23% 7%	300
	11th to 20th	Day	7% 5% 31% 33% 19% 6%	297
	21st to end	Day	15% 9% 27% 28% 16% 4	297
November	1st to 10th	Day	7% 7% 30% 32% 20% 3	270
	11th to 20th	Day	7% 9% 30% 35% 16% 4	270
	21st to end	Day	12% 13% 26% 29% 15% 6%	270
December	1st to 10th	Day	4 6% 34% 38% 16% 2	270
	11th to 20th	Day	9% 9% 35% 32% 15% 1	270
	21st to end	Day	13% 15% 37% 25% 9%	297
January	1st to 10th	Night	6% 8% 36% 41% 8% 1	950
	11th to 20th	Night	9% 8% 33% 37% 11% 1	950
	21st to end	Night	6% 7% 38% 40% 9%	927
February	1st to 10th	Night	8% 11% 37% 39% 6%	760
	11th to 20th	Night	8% 10% 49% 28% 5%	744
	21st to end	Night	9% 11% 47% 29% 4	628
March	1st to 10th	Night	7% 12% 43% 34% 4	760
	11th to 20th	Night	11% 10% 38% 32% 8%	649
	21st to end	Night	10% 14% 49% 24% 2	627
April	1st to 10th	Night	8% 14% 45% 29% 3	570
	11th to 20th	Night	10% 15% 50% 23% 3	563
	21st to end	Night	12% 12% 42% 27% 6%	570
May	1st to 10th	Night	9% 11% 45% 31% 4	570
	11th to 20th	Night	9% 8% 38% 36% 10%	561
	21st to end	Night	9% 7% 47% 30% 8%	617
June	1st to 10th	Night	4 5% 39% 39% 12%	570
	11th to 20th	Night	4 7% 49% 35% 5%	570
	21st to end	Night	3 5% 38% 44% 11%	570
July	1st to 10th	Night	5% 3 25% 46% 19% 1	555
	11th to 20th	Night	4 1 22% 50% 22% 1	552
	21st to end	Night	6% 1 19% 52% 22% 1	624
August	1st to 10th	Night	5% 2 18% 48% 26% 1	567
	11th to 20th	Night	7% 2 20% 51% 20% 1	564
	21st to end	Night	5% 2 23% 46% 24% 1	627
September	1st to 10th	Night	8% 1 26% 51% 14%	570
	11th to 20th	Night	7% 2 37% 43% 9% 1	570
	21st to end	Night	6% 5% 28% 46% 14%	570
October	1st to 10th	Night	10% 5% 30% 43% 12%	570
	11th to 20th	Night	7% 7% 37% 38% 11% 1	595
	21st to end	Night	9% 8% 33% 32% 16% 1	984
November	1st to 10th	Night	5% 5% 32% 46% 11%	925
	11th to 20th	Night	4 7% 39% 39% 10%	950
	21st to end	Night	9% 9% 30% 37% 13% 1	950
December	1st to 10th	Night	7% 6% 34% 43% 10%	950
	11th to 20th	Night	10% 9% 37% 37% 7%	950
	21st to end	Night	10% 11% 37% 35% 7% 1	1045

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