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 2024-02-15.

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 3 3 2 3 4 5% 7% 60%	78786
	Night	6% 4 2 4 4 2 4 4 5% 7% 59%	80314
Transparency	Day	24% 5% 10% 24% 26% 11%	78503
	Night	24% 5% 10% 23% 25% 12%	80120
Seeing	Day	8% 7% 28% 33% 20% 4	14374
	Night	7% 7% 36% 38% 11%	24500

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 4 3 2 3 3 4 6% 56%	2538
	11th to 20th	Day	3 4 2 5% 4 3 4 4 4 7% 61%	2641
	21st to end	Day	7% 6% 3 5% 4 3 3 3 4 6% 57%	3361
February	1st to 10th	Day	6% 7% 2 6% 4 2 3 4 4 6% 57%	1900
	11th to 20th	Day	5% 7% 3 6% 4 2 3 4 4 6% 57%	1789
	21st to end	Day	5% 4 2 3 3 3 3 3 4 6% 64%	1480
March	1st to 10th	Day	6% 5% 2 5% 4 2 3 3 5% 6% 59%	1800
	11th to 20th	Day	10% 4 2 4 2 2 3 3 4 6% 60%	1903
	21st to end	Day	7% 5% 2 3 4 2 4 3 4 7% 58%	2258
April	1st to 10th	Day	7% 3 1 3 2 2 4 3 4 5% 65%	2160
	11th to 20th	Day	11% 4 1 3 4 2 3 3 4 6% 60%	2131
	21st to end	Day	9% 5% 2 3 3 2 3 4 5% 7% 58%	2227
May	1st to 10th	Day	10% 4 2 3 3 2 3 4 4 7% 59%	2340
	11th to 20th	Day	8% 4 2 3 3 2 4 4 6% 7% 57%	2302
	21st to end	Day	6% 4 2 3 4 3 5% 4 6% 8% 56%	2531
June	1st to 10th	Day	4 3 2 3 4 3 4 5% 6% 9% 58%	2359
	11th to 20th	Day	5% 2 1 3 2 2 4 4 5% 8% 64%	2520
	21st to end	Day	3 2 1 4 3 2 4 5% 6% 10% 61%	2520
July	1st to 10th	Day	6% 3 2 3 4 3 5% 5% 7% 9% 54%	2520
	11th to 20th	Day	3 2 2 3 3 3 4 4 6% 9% 62%	2476
	21st to end	Day	5% 2 1 4 4 3 4 5% 6% 10% 56%	2546
August	1st to 10th	Day	4 2 1 3 3 3 5% 6% 7% 10% 56%	2268
	11th to 20th	Day	5% 4 2 4 4 3 4 5% 5% 8% 55%	2123
	21st to end	Day	5% 3 1 4 3 2 4 5% 6% 9% 58%	2376
September	1st to 10th	Day	10% 4 1 3 3 1 3 4 4 7% 58%	2142
	11th to 20th	Day	7% 3 1 3 3 3 4 4 4 7% 61%	1980
	21st to end	Day	6% 3 1 3 3 2 3 3 3 6% 67%	1980
October	1st to 10th	Day	12% 4 2 3 3 2 3 3 3 6% 60%	1980
	11th to 20th	Day	7% 2 1 2 2 1 2 2 3 4 73%	1940
	21st to end	Day	8% 5% 1 3 3 1 2 2 3 4 68%	1782
November	1st to 10th	Day	5% 2 1 2 2 1 3 3 3 7% 70%	1673
	11th to 20th	Day	4 4 1 2 3 2 1 3 4 5% 71%	1710
	21st to end	Day	7% 5% 2 3 2 2 4 2 3 6% 65%	1710
December	1st to 10th	Day	2 6% 2 3 4 2 3 4 6% 7% 62%	1710
	11th to 20th	Day	6% 4 2 2 3 2 3 4 5% 7% 62%	2161
	21st to end	Day	5% 9% 3 5% 5% 3 4 3 4 6% 52%	2949
January	1st to 10th	Night	5% 6% 2 5% 5% 3 4 4 4 6% 57%	4417
	11th to 20th	Night	4 5% 2 4 3 2 3 5% 4 6% 61%	4309
	21st to end	Night	7% 6% 2 4 4 2 3 3 4 7% 56%	4336
February	1st to 10th	Night	5% 6% 3 5% 4 2 3 3 5% 5% 59%	2280
	11th to 20th	Night	5% 6% 3 6% 5% 3 4 4 5% 6% 53%	2152
	21st to end	Night	6% 5% 1 4 3 1 3 3 5% 6% 62%	1776
March	1st to 10th	Night	5% 5% 2 3 4 2 3 4 5% 6% 59%	2160
	11th to 20th	Night	9% 4 2 3 3 2 3 3 4 7% 60%	2055
	21st to end	Night	8% 5% 2 3 3 3 4 5% 6% 7% 56%	2093
April	1st to 10th	Night	6% 4 2 4 3 2 3 3 4 6% 64%	1800
	11th to 20th	Night	8% 5% 2 4 4 2 3 4 5% 7% 57%	1777
	21st to end	Night	12% 4 2 3 3 2 4 3 6% 9% 55%	1731
May	1st to 10th	Night	8% 4 2 4 4 2 4 4 6% 7% 55%	1620
	11th to 20th	Night	8% 4 2 3 4 2 4 5% 6% 9% 55%	1593
	21st to end	Night	8% 3 1 4 4 2 5% 5% 6% 9% 53%	1745
June	1st to 10th	Night	4 2 1 3 3 3 5% 4 6% 12% 57%	1595
	11th to 20th	Night	4 2 1 3 4 3 5% 5% 7% 8% 59%	1440
	21st to end	Night	3 3 1 3 4 2 5% 5% 7% 10% 56%	1440
July	1st to 10th	Night	6% 2 2 3 3 3 5% 5% 8% 11% 52%	1440
	11th to 20th	Night	3 3 1 3 4 2 4 4 8% 10% 58%	1480
	21st to end	Night	5% 3 2 5% 5% 3 5% 6% 8% 11% 47%	1772
August	1st to 10th	Night	5% 3 2 4 6% 3 6% 6% 9% 12% 45%	1667
	11th to 20th	Night	6% 4 3 3 4 3 5% 5% 6% 10% 50%	1778
	21st to end	Night	5% 3 2 4 3 2 4 4 6% 11% 56%	1980
September	1st to 10th	Night	7% 3 1 3 3 2 3 3 5% 7% 62%	1818
	11th to 20th	Night	7% 3 1 3 3 2 3 5% 5% 8% 60%	1980
	21st to end	Night	6% 2 1 3 3 2 3 3 4 5% 68%	1980
October	1st to 10th	Night	10% 4 2 3 3 2 3 3 5% 6% 61%	1980
	11th to 20th	Night	7% 3 1 2 2 1 2 2 3 4 73%	2005
	21st to end	Night	7% 4 1 2 3 2 2 2 4 5% 68%	2568
November	1st to 10th	Night	4 3 1 3 2 1 2 3 4 7% 71%	2405
	11th to 20th	Night	2 2 1 3 3 2 3 3 4 5% 73%	2470
	21st to end	Night	7% 4 2 3 2 2 3 4 4 6% 64%	2470
December	1st to 10th	Night	4 4 1 4 3 2 3 4 5% 8% 61%	2470
	11th to 20th	Night	6% 4 2 3 3 2 3 3 4 7% 63%	3036
	21st to end	Night	5% 5% 2 4 4 3 4 5% 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%	1799
	21st to end	Day	23% 3 5% 22% 31% 16%	1480
March	1st to 10th	Day	27% 2 9% 20% 25% 17%	1800
	11th to 20th	Day	26% 4 9% 22% 26% 13%	1903
	21st to end	Day	27% 4 11% 26% 22% 9%	2258
April	1st to 10th	Day	22% 3 8% 23% 28% 17%	2160
	11th to 20th	Day	27% 4 10% 22% 24% 14%	2134
	21st to end	Day	27% 4 9% 25% 26% 9%	2227
May	1st to 10th	Day	27% 5% 9% 24% 22% 13%	2340
	11th to 20th	Day	26% 6% 14% 26% 22% 6%	2306
	21st to end	Day	25% 8% 14% 22% 21% 11%	2531
June	1st to 10th	Day	22% 7% 15% 25% 21% 9%	2359
	11th to 20th	Day	19% 6% 9% 20% 27% 19%	2520
	21st to end	Day	18% 5% 12% 26% 26% 13%	2520
July	1st to 10th	Day	25% 8% 12% 24% 22% 8%	2451
	11th to 20th	Day	18% 6% 11% 24% 31% 10%	2401
	21st to end	Day	24% 7% 14% 29% 23% 2	2405
August	1st to 10th	Day	21% 9% 17% 29% 18% 6%	2254
	11th to 20th	Day	27% 6% 10% 27% 22% 9%	2123
	21st to end	Day	21% 7% 11% 25% 25% 10%	2376
September	1st to 10th	Day	27% 5% 8% 22% 24% 14%	2142
	11th to 20th	Day	23% 6% 8% 22% 27% 14%	1980
	21st to end	Day	20% 3 9% 25% 29% 14%	1980
October	1st to 10th	Day	28% 5% 9% 18% 27% 12%	1980
	11th to 20th	Day	17% 2 6% 20% 33% 22%	1940
	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% 22% 24% 11%	2152
	21st to end	Night	24% 3 5% 21% 31% 18%	1776
March	1st to 10th	Night	26% 3 7% 22% 28% 15%	2160
	11th to 20th	Night	26% 4 8% 23% 23% 16%	2055
	21st to end	Night	27% 6% 10% 25% 21% 11%	2093
April	1st to 10th	Night	24% 3 8% 22% 26% 18%	1800
	11th to 20th	Night	27% 4 11% 23% 23% 12%	1777
	21st to end	Night	28% 5% 12% 24% 22% 9%	1731
May	1st to 10th	Night	28% 6% 9% 22% 22% 14%	1620
	11th to 20th	Night	26% 8% 16% 19% 23% 8%	1594
	21st to end	Night	27% 8% 17% 21% 16% 12%	1746
June	1st to 10th	Night	21% 7% 19% 28% 17% 8%	1595
	11th to 20th	Night	20% 9% 13% 21% 24% 14%	1440
	21st to end	Night	21% 8% 12% 27% 20% 13%	1440
July	1st to 10th	Night	24% 7% 16% 27% 21% 6%	1400
	11th to 20th	Night	18% 6% 15% 25% 25% 10%	1432
	21st to end	Night	28% 8% 14% 28% 19% 4	1673
August	1st to 10th	Night	27% 9% 17% 25% 15% 6%	1657
	11th to 20th	Night	29% 7% 12% 27% 16% 8%	1778
	21st to end	Night	23% 6% 12% 24% 26% 9%	1980
September	1st to 10th	Night	23% 5% 13% 21% 24% 14%	1818
	11th to 20th	Night	23% 6% 12% 18% 27% 14%	1980
	21st to end	Night	19% 6% 7% 23% 29% 16%	1980
October	1st to 10th	Night	25% 5% 9% 18% 27% 16%	1980
	11th to 20th	Night	18% 3 6% 16% 32% 24%	2005
	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% 9% 44% 26% 10% 3	252
	21st to end	Day	7% 9% 52% 27% 5% 1	198
March	1st to 10th	Day	7% 9% 41% 34% 9%	240
	11th to 20th	Day	14% 12% 36% 24% 13% 1	240
	21st to end	Day	15% 15% 33% 26% 10% 1	344
April	1st to 10th	Day	9% 14% 41% 25% 10% 1	420
	11th to 20th	Day	11% 17% 38% 28% 6%	412
	21st to end	Day	14% 15% 39% 23% 8% 2	487
May	1st to 10th	Day	10% 10% 34% 33% 11% 1	603
	11th to 20th	Day	12% 7% 29% 33% 16% 3	625
	21st to end	Day	9% 8% 36% 30% 16% 1	679
June	1st to 10th	Day	5% 4 26% 36% 22% 7%	630
	11th to 20th	Day	5% 3 31% 36% 21% 3	630
	21st to end	Day	4 2 24% 41% 25% 3	630
July	1st to 10th	Day	5% 1 16% 37% 32% 8%	621
	11th to 20th	Day	2 1 13% 40% 34% 10%	618
	21st to end	Day	5% 1 8% 39% 35% 11%	684
August	1st to 10th	Day	4 1 11% 40% 36% 7%	566
	11th to 20th	Day	3 15% 40% 34% 8%	437
	21st to end	Day	4 1 14% 41% 29% 11%	495
September	1st to 10th	Day	11% 2 16% 35% 29% 7%	432
	11th to 20th	Day	6% 3 15% 40% 27% 10%	270
	21st to end	Day	7% 5% 23% 32% 27% 6%	270
October	1st to 10th	Day	12% 7% 26% 27% 22% 6%	270
	11th to 20th	Day	6% 5% 31% 33% 20% 6%	270
	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	7% 10% 49% 29% 5%	722
	21st to end	Night	9% 11% 47% 30% 4	592
March	1st to 10th	Night	7% 11% 44% 33% 4	720
	11th to 20th	Night	11% 11% 38% 31% 9%	615
	21st to end	Night	11% 14% 49% 24% 2	594
April	1st to 10th	Night	9% 13% 46% 29% 4	540
	11th to 20th	Night	10% 15% 49% 23% 3	533
	21st to end	Night	13% 12% 41% 27% 6%	540
May	1st to 10th	Night	9% 10% 45% 31% 4	540
	11th to 20th	Night	9% 8% 38% 35% 10%	531
	21st to end	Night	9% 7% 47% 30% 8%	584
June	1st to 10th	Night	4 6% 39% 39% 12%	540
	11th to 20th	Night	3 6% 49% 35% 6%	540
	21st to end	Night	3 5% 37% 45% 11%	540
July	1st to 10th	Night	5% 3 24% 46% 20% 1	525
	11th to 20th	Night	4 1 21% 50% 23% 1	522
	21st to end	Night	6% 1 18% 53% 21% 1	591
August	1st to 10th	Night	4 2 18% 48% 27% 1	537
	11th to 20th	Night	7% 2 21% 50% 19% 1	534
	21st to end	Night	5% 2 23% 45% 24% 1	594
September	1st to 10th	Night	8% 1 26% 51% 14%	540
	11th to 20th	Night	7% 2 36% 44% 10% 1	540
	21st to end	Night	6% 5% 29% 45% 14%	540
October	1st to 10th	Night	11% 5% 31% 41% 12%	540
	11th to 20th	Night	7% 7% 37% 38% 11% 1	565
	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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