Monahans Sandhills State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Monahans Sandhills State Park clear sky chart from 2005-11-06 to 2025-06-10.

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	4 3 1 3 3 3 3 3 4 6% 66%	123733
	Night	5% 3 1 3 2 3 3 3 5% 7% 66%	123338
Transparency	Day	19% 4 7% 18% 27% 25%	123511
	Night	19% 4 8% 19% 26% 25%	123149
Seeing	Day	6% 5% 20% 35% 26% 8%	15637
	Night	6% 5% 31% 43% 14% 1	25722

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	4 4 1 4 3 3 3 2 4 6% 64%	4259
	11th to 20th	Day	3 2 1 2 2 2 2 2 4 6% 75%	4540
	21st to end	Day	5% 6% 2 5% 3 3 3 3 4 6% 62%	4994
February	1st to 10th	Day	4 5% 1 4 2 2 3 3 5% 7% 65%	2000
	11th to 20th	Day	5% 4 2 5% 4 3 3 3 5% 7% 60%	1949
	21st to end	Day	5% 5% 1 4 2 2 2 3 5% 5% 64%	1650
March	1st to 10th	Day	3 3 1 3 3 3 3 3 4 6% 66%	4500
	11th to 20th	Day	9% 4 2 4 3 3 3 3 4 6% 59%	4659
	21st to end	Day	2 3 1 4 3 3 4 3 5% 7% 64%	5959
April	1st to 10th	Day	4 2 1 3 3 3 3 3 4 7% 66%	2400
	11th to 20th	Day	5% 3 1 3 3 2 3 2 4 6% 68%	2371
	21st to end	Day	3 3 1 2 2 2 3 3 4 6% 72%	2400
May	1st to 10th	Day	5% 3 1 3 2 2 2 2 4 5% 69%	5440
	11th to 20th	Day	4 3 1 4 3 3 3 3 5% 6% 67%	5816
	21st to end	Day	5% 3 1 3 2 2 3 3 5% 8% 66%	6446
June	1st to 10th	Day	2 2 1 3 3 3 3 3 6% 8% 68%	2588
	11th to 20th	Day	2 2 1 2 2 3 4 3 5% 7% 69%	2470
	21st to end	Day	4 3 1 3 3 3 4 3 5% 7% 64%	2470
July	1st to 10th	Day	4 2 1 3 3 3 4 3 6% 10% 60%	4120
	11th to 20th	Day	2 2 1 3 2 3 3 3 5% 7% 69%	3942
	21st to end	Day	5% 3 1 3 3 3 4 4 5% 8% 61%	4118
August	1st to 10th	Day	1 1 1 2 2 2 2 2 4 7% 75%	3784
	11th to 20th	Day	2 2 1 3 3 3 4 3 5% 9% 64%	3726
	21st to end	Day	4 3 1 4 3 4 4 4 7% 10% 56%	4180
September	1st to 10th	Day	8% 4 1 4 4 4 4 4 6% 7% 53%	2280
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 50%	2109
	21st to end	Day	7% 4 2 4 3 3 4 3 5% 6% 60%	2090
October	1st to 10th	Day	2 2 1 2 2 2 2 1 3 3 79%	3480
	11th to 20th	Day	6% 3 1 2 2 2 3 2 3 4 71%	3400
	21st to end	Day	3 2 1 2 1 1 1 1 2 3 83%	3411
November	1st to 10th	Day	6% 4 1 2 2 1 1 2 3 6% 71%	1763
	11th to 20th	Day	4 3 1 4 3 2 3 3 5% 5% 67%	1800
	21st to end	Day	7% 4 1 4 3 3 3 2 4 6% 63%	1800
December	1st to 10th	Day	14% 8% 2 6% 3 2 3 2 4 5% 49%	2940
	11th to 20th	Day	2 3 2 4 3 3 4 3 4 6% 66%	3391
	21st to end	Day	4 3 1 3 2 2 3 2 2 5% 74%	4488
January	1st to 10th	Night	4 4 2 4 3 2 2 2 4 6% 66%	5735
	11th to 20th	Night	3 2 1 3 2 2 3 3 4 6% 72%	5440
	21st to end	Night	6% 6% 2 5% 3 2 3 3 4 7% 61%	5984
February	1st to 10th	Night	5% 4 1 3 3 2 3 3 4 6% 66%	2400
	11th to 20th	Night	6% 4 2 5% 3 3 3 4 6% 6% 58%	2338
	21st to end	Night	5% 4 1 3 3 3 3 2 4 5% 66%	1980
March	1st to 10th	Night	4 4 1 3 2 3 3 3 5% 6% 66%	5374
	11th to 20th	Night	7% 4 1 3 3 2 3 3 5% 6% 63%	5313
	21st to end	Night	2 3 1 2 2 3 4 3 6% 7% 66%	4988
April	1st to 10th	Night	5% 4 1 4 3 3 3 3 5% 7% 62%	2000
	11th to 20th	Night	5% 3 2 3 2 3 4 3 6% 6% 63%	1977
	21st to end	Night	4 3 1 2 2 2 2 3 3 5% 72%	2000
May	1st to 10th	Night	8% 3 1 3 2 2 3 3 4 6% 66%	4540
	11th to 20th	Night	5% 4 1 4 2 4 3 3 5% 6% 64%	4081
	21st to end	Night	4 3 1 4 3 3 4 3 5% 8% 63%	4451
June	1st to 10th	Night	2 2 1 2 2 3 3 4 6% 11% 64%	1796
	11th to 20th	Night	2 2 1 2 3 4 4 4 7% 9% 62%	1710
	21st to end	Night	3 1 1 3 3 3 2 4 5% 11% 64%	1710
July	1st to 10th	Night	3 2 1 3 3 2 4 4 7% 11% 60%	2850
	11th to 20th	Night	2 1 1 2 2 2 2 3 5% 11% 69%	3009
	21st to end	Night	4 2 1 3 3 3 3 3 6% 11% 61%	3445
August	1st to 10th	Night	1 2 2 2 2 2 3 5% 9% 72%	3155
	11th to 20th	Night	2 2 1 3 3 3 3 4 7% 10% 64%	3113
	21st to end	Night	4 2 1 3 3 2 3 3 6% 13% 60%	3487
September	1st to 10th	Night	8% 4 1 4 3 4 4 4 6% 9% 53%	1900
	11th to 20th	Night	6% 4 1 4 3 3 5% 4 6% 9% 54%	2071
	21st to end	Night	6% 3 1 4 3 3 4 3 7% 9% 56%	2090
October	1st to 10th	Night	3 1 1 2 2 3 2 2 3 5% 77%	3480
	11th to 20th	Night	10% 3 1 2 2 2 1 1 2 4 72%	3515
	21st to end	Night	4 2 1 2 1 1 2 1 2 3 81%	4120
November	1st to 10th	Night	6% 2 1 3 2 2 2 2 3 5% 71%	2530
	11th to 20th	Night	3 3 1 4 3 3 3 3 4 6% 67%	2600
	21st to end	Night	7% 4 2 3 3 3 3 3 4 6% 64%	2600
December	1st to 10th	Night	12% 4 2 4 3 3 4 3 4 5% 56%	4250
	11th to 20th	Night	3 3 1 4 3 2 3 3 4 6% 68%	4816
	21st to end	Night	3 3 1 3 2 2 2 2 3 5% 72%	6490

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	22% 2 4 20% 32% 20%	4260
	11th to 20th	Day	13% 2 4 23% 35% 23%	4540
	21st to end	Day	25% 4 5% 17% 27% 22%	4994
February	1st to 10th	Day	19% 3 7% 15% 23% 32%	2000
	11th to 20th	Day	25% 3 7% 18% 22% 25%	1959
	21st to end	Day	22% 3 4 11% 27% 33%	1650
March	1st to 10th	Day	19% 4 3 8% 26% 40%	4500
	11th to 20th	Day	27% 3 4 7% 21% 37%	4659
	21st to end	Day	18% 3 5% 11% 23% 40%	5959
April	1st to 10th	Day	18% 4 6% 12% 26% 34%	2400
	11th to 20th	Day	19% 3 5% 11% 27% 33%	2374
	21st to end	Day	15% 3 7% 16% 27% 33%	2400
May	1st to 10th	Day	19% 2 6% 15% 22% 36%	5440
	11th to 20th	Day	19% 4 5% 12% 26% 35%	5820
	21st to end	Day	17% 4 7% 22% 17% 33%	6447
June	1st to 10th	Day	14% 6% 11% 23% 30% 17%	2588
	11th to 20th	Day	14% 4 9% 18% 30% 25%	2470
	21st to end	Day	19% 6% 9% 21% 25% 19%	2470
July	1st to 10th	Day	20% 5% 14% 31% 23% 7%	4056
	11th to 20th	Day	14% 4 11% 28% 33% 9%	3874
	21st to end	Day	20% 5% 11% 28% 27% 8%	3988
August	1st to 10th	Day	10% 4 8% 31% 36% 11%	3772
	11th to 20th	Day	17% 5% 11% 27% 33% 7%	3762
	21st to end	Day	23% 7% 16% 24% 26% 6%	4179
September	1st to 10th	Day	27% 7% 13% 18% 22% 13%	2280
	11th to 20th	Day	30% 7% 11% 20% 23% 9%	2109
	21st to end	Day	25% 5% 7% 18% 28% 17%	2090
October	1st to 10th	Day	12% 3 6% 12% 20% 47%	3480
	11th to 20th	Day	20% 2 8% 15% 21% 34%	3400
	21st to end	Day	10% 1 2 17% 44% 24%	3411
November	1st to 10th	Day	17% 3 6% 19% 28% 26%	1763
	11th to 20th	Day	20% 3 8% 16% 30% 23%	1800
	21st to end	Day	24% 2 7% 17% 28% 22%	1800
December	1st to 10th	Day	38% 2 6% 13% 24% 16%	2940
	11th to 20th	Day	20% 3 5% 18% 32% 22%	3389
	21st to end	Day	16% 3 3 14% 43% 21%	4488
January	1st to 10th	Night	20% 2 4 17% 37% 20%	5735
	11th to 20th	Night	15% 2 6% 19% 31% 27%	5440
	21st to end	Night	25% 3 5% 18% 25% 23%	5984
February	1st to 10th	Night	20% 3 7% 12% 26% 32%	2400
	11th to 20th	Night	25% 5% 7% 15% 23% 25%	2338
	21st to end	Night	22% 3 5% 8% 25% 37%	1980
March	1st to 10th	Night	19% 3 4 10% 24% 41%	5374
	11th to 20th	Night	22% 4 6% 10% 16% 41%	5313
	21st to end	Night	15% 4 8% 13% 22% 37%	4988
April	1st to 10th	Night	22% 4 7% 13% 20% 33%	2000
	11th to 20th	Night	19% 5% 7% 16% 22% 31%	1977
	21st to end	Night	16% 4 8% 21% 23% 28%	2000
May	1st to 10th	Night	20% 3 10% 20% 18% 28%	4537
	11th to 20th	Night	22% 5% 6% 15% 22% 31%	4082
	21st to end	Night	20% 5% 10% 20% 17% 29%	4452
June	1st to 10th	Night	14% 6% 15% 27% 27% 11%	1796
	11th to 20th	Night	16% 6% 11% 20% 29% 18%	1710
	21st to end	Night	16% 5% 13% 23% 25% 18%	1710
July	1st to 10th	Night	18% 5% 16% 38% 18% 5%	2805
	11th to 20th	Night	12% 3 12% 36% 29% 8%	2955
	21st to end	Night	17% 5% 13% 30% 29% 6%	3336
August	1st to 10th	Night	10% 3 7% 29% 40% 11%	3144
	11th to 20th	Night	14% 4 13% 33% 29% 6%	3143
	21st to end	Night	17% 6% 17% 29% 26% 6%	3487
September	1st to 10th	Night	26% 7% 13% 21% 20% 14%	1900
	11th to 20th	Night	24% 8% 14% 23% 22% 9%	2071
	21st to end	Night	23% 5% 10% 21% 22% 19%	2090
October	1st to 10th	Night	12% 4 7% 12% 19% 46%	3480
	11th to 20th	Night	20% 1 8% 13% 18% 39%	3515
	21st to end	Night	12% 2 4 18% 38% 26%	4120
November	1st to 10th	Night	18% 3 5% 19% 29% 26%	2530
	11th to 20th	Night	19% 4 7% 17% 25% 28%	2600
	21st to end	Night	23% 3 6% 15% 26% 27%	2600
December	1st to 10th	Night	32% 2 4 17% 26% 18%	4250
	11th to 20th	Night	18% 3 3 16% 35% 24%	4817
	21st to end	Night	16% 3 4 15% 37% 26%	6490

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	8% 6% 32% 35% 18% 1	300
	11th to 20th	Day	10% 5% 28% 37% 15% 4	300
	21st to end	Day	8% 8% 30% 38% 13% 3	330
February	1st to 10th	Day	8% 6% 25% 40% 17% 3	300
	11th to 20th	Day	11% 9% 37% 29% 13% 1	300
	21st to end	Day	10% 10% 31% 37% 11%	249
March	1st to 10th	Day	9% 5% 35% 37% 12%	300
	11th to 20th	Day	11% 8% 31% 34% 12% 4	300
	21st to end	Day	5% 12% 31% 38% 12% 1	540
April	1st to 10th	Day	5% 11% 35% 35% 12% 1	500
	11th to 20th	Day	7% 12% 43% 28% 10%	492
	21st to end	Day	4 12% 35% 36% 13% 1	500
May	1st to 10th	Day	4 9% 36% 35% 14% 2	503
	11th to 20th	Day	7% 6% 28% 37% 19% 3	705
	21st to end	Day	5% 5% 31% 43% 15% 2	789
June	1st to 10th	Day	3 2 17% 46% 27% 5%	726
	11th to 20th	Day	2 1 17% 48% 26% 6%	680
	21st to end	Day	4 1 9% 41% 36% 8%	680
July	1st to 10th	Day	4 1 6% 32% 41% 16%	671
	11th to 20th	Day	2 4 38% 43% 14%	569
	21st to end	Day	2 3 35% 43% 17%	531
August	1st to 10th	Day	2 3 27% 48% 20%	487
	11th to 20th	Day	4 1 5% 26% 39% 23%	477
	21st to end	Day	5% 1 4 27% 42% 22%	539
September	1st to 10th	Day	9% 1 6% 27% 39% 19%	490
	11th to 20th	Day	4 6% 28% 46% 15%	319
	21st to end	Day	10% 2 9% 21% 40% 18%	300
October	1st to 10th	Day	6% 3 9% 30% 40% 13%	300
	11th to 20th	Day	10% 3 15% 30% 31% 11%	300
	21st to end	Day	8% 6% 16% 32% 25% 13%	330
November	1st to 10th	Day	11% 4 20% 34% 26% 5%	300
	11th to 20th	Day	9% 8% 19% 32% 24% 9%	300
	21st to end	Day	10% 7% 29% 32% 16% 6%	300
December	1st to 10th	Day	11% 7% 22% 35% 21% 3	300
	11th to 20th	Day	6% 5% 26% 44% 17% 3	300
	21st to end	Day	5% 7% 33% 39% 12% 3	330
January	1st to 10th	Night	8% 5% 35% 42% 10%	938
	11th to 20th	Night	9% 7% 30% 43% 11% 1	800
	21st to end	Night	8% 7% 36% 40% 9%	880
February	1st to 10th	Night	7% 7% 38% 37% 11% 1	800
	11th to 20th	Night	9% 8% 43% 36% 5%	784
	21st to end	Night	6% 11% 45% 34% 3	660
March	1st to 10th	Night	9% 9% 43% 35% 4	800
	11th to 20th	Night	8% 11% 40% 35% 6%	751
	21st to end	Night	4 10% 53% 28% 4	660
April	1st to 10th	Night	7% 9% 51% 29% 5%	600
	11th to 20th	Night	5% 12% 54% 26% 3	593
	21st to end	Night	4 10% 52% 31% 4	600
May	1st to 10th	Night	6% 7% 46% 38% 3	600
	11th to 20th	Night	6% 6% 39% 40% 9%	591
	21st to end	Night	4 4 49% 39% 5%	650
June	1st to 10th	Night	2 3 39% 48% 8%	599
	11th to 20th	Night	2 3 38% 49% 8%	570
	21st to end	Night	3 1 26% 54% 15% 1	570
July	1st to 10th	Night	3 1 12% 56% 27% 2	555
	11th to 20th	Night	3 1 9% 65% 22% 1	552
	21st to end	Night	1 1 9% 60% 29% 1	624
August	1st to 10th	Night	3 1 7% 56% 34% 1	567
	11th to 20th	Night	3 1 8% 45% 40% 3	564
	21st to end	Night	3 7% 49% 39% 1	627
September	1st to 10th	Night	9% 1 8% 50% 31% 1	570
	11th to 20th	Night	6% 1 15% 50% 27% 1	570
	21st to end	Night	7% 2 17% 51% 23%	570
October	1st to 10th	Night	6% 2 25% 51% 16% 1	570
	11th to 20th	Night	9% 4 28% 46% 12%	601
	21st to end	Night	8% 4 24% 44% 18% 2	836
November	1st to 10th	Night	6% 3 29% 42% 19% 1	970
	11th to 20th	Night	4 4 26% 48% 16% 1	1000
	21st to end	Night	8% 5% 31% 39% 16% 1	1000
December	1st to 10th	Night	10% 3 29% 44% 13%	1000
	11th to 20th	Night	7% 7% 33% 43% 10%	1000
	21st to end	Night	7% 6% 30% 43% 12% 1	1100

Page generated at 2025-06-07 09:28:20. Version ac07

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