Balmorhea State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Balmorhea State Park clear sky chart from 2005-11-06 to 2025-09-19.

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 5% 7% 65%	134175
	Night	4 3 1 3 2 3 3 3 5% 7% 66%	132343
Transparency	Day	19% 4 8% 16% 26% 27%	129287
	Night	18% 4 7% 17% 25% 29%	128234
Seeing	Day	6% 7% 22% 32% 24% 8%	15876
	Night	6% 5% 24% 42% 22% 2	25907

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	3 3 1 3 3 3 3 3 5% 6% 68%	4537
	11th to 20th	Day	2 4 1 3 1 2 2 2 4 6% 73%	4540
	21st to end	Day	2 3 2 5% 3 3 3 3 4 6% 68%	4994
February	1st to 10th	Day	3 4 2 4 2 3 4 2 5% 6% 66%	2000
	11th to 20th	Day	4 5% 1 4 3 3 4 3 4 7% 63%	1949
	21st to end	Day	3 5% 1 3 2 3 3 2 5% 5% 69%	1650
March	1st to 10th	Day	3 3 1 4 3 4 3 3 5% 6% 65%	4500
	11th to 20th	Day	9% 5% 1 3 2 3 3 2 5% 5% 62%	4803
	21st to end	Day	2 3 1 4 3 4 4 4 5% 7% 65%	5955
April	1st to 10th	Day	3 3 1 3 3 3 3 3 5% 8% 66%	2400
	11th to 20th	Day	4 2 1 3 3 3 3 3 5% 6% 68%	2371
	21st to end	Day	4 3 1 2 2 2 2 2 4 5% 73%	2400
May	1st to 10th	Day	4 2 1 2 2 2 2 2 4 4 76%	5440
	11th to 20th	Day	4 3 1 3 2 2 4 3 5% 6% 67%	5446
	21st to end	Day	4 2 1 2 2 2 4 4 7% 7% 65%	6446
June	1st to 10th	Day	2 1 1 3 2 3 4 4 6% 10% 65%	2600
	11th to 20th	Day	2 2 1 3 3 3 4 5% 6% 8% 64%	2600
	21st to end	Day	5% 3 1 3 4 4 5% 5% 6% 9% 55%	2600
July	1st to 10th	Day	6% 3 1 4 4 3 4 4 7% 8% 56%	5625
	11th to 20th	Day	2 2 1 3 3 3 4 4 7% 10% 61%	5440
	21st to end	Day	4 3 1 4 4 4 5% 5% 9% 10% 51%	5922
August	1st to 10th	Day	1 1 1 2 2 3 3 4 5% 10% 67%	5348
	11th to 20th	Day	2 2 1 5% 5% 5% 6% 5% 8% 10% 49%	5366
	21st to end	Day	4 2 1 4 3 4 4 4 6% 8% 59%	5984
September	1st to 10th	Day	11% 4 1 5% 4 4 5% 4 7% 8% 45%	2400
	11th to 20th	Day	11% 4 2 5% 5% 4 4 5% 7% 9% 44%	2253
	21st to end	Day	9% 3 1 3 3 4 4 4 6% 6% 57%	2090
October	1st to 10th	Day	3 1 1 2 2 2 2 2 4 5% 77%	3480
	11th to 20th	Day	4 2 1 2 2 2 2 2 2 4 77%	3254
	21st to end	Day	3 2 1 1 1 1 1 1 3 5% 81%	3438
November	1st to 10th	Day	7% 2 1 2 1 2 2 2 4 4 74%	1861
	11th to 20th	Day	3 4 1 3 3 2 3 3 3 4 72%	1800
	21st to end	Day	6% 4 1 3 2 3 3 3 5% 6% 65%	1800
December	1st to 10th	Day	7% 11% 2 4 2 2 3 2 4 5% 57%	2940
	11th to 20th	Day	1 2 1 3 2 3 4 4 5% 5% 71%	3391
	21st to end	Day	3 3 1 2 1 1 2 2 3 5% 77%	4552
January	1st to 10th	Night	3 5% 1 3 2 3 2 2 3 5% 68%	5428
	11th to 20th	Night	2 3 1 2 2 2 2 2 4 6% 73%	5440
	21st to end	Night	4 4 2 5% 3 3 3 2 5% 7% 62%	5984
February	1st to 10th	Night	4 5% 1 4 2 2 3 3 4 6% 67%	2400
	11th to 20th	Night	5% 5% 1 4 3 2 4 3 4 6% 62%	2338
	21st to end	Night	4 4 1 2 3 2 3 4 4 6% 66%	1980
March	1st to 10th	Night	3 4 1 4 3 3 3 3 5% 6% 65%	5374
	11th to 20th	Night	9% 4 1 3 2 2 3 3 4 5% 66%	5185
	21st to end	Night	2 4 1 4 3 3 3 3 5% 6% 66%	4996
April	1st to 10th	Night	6% 3 1 3 3 3 3 3 5% 6% 65%	2000
	11th to 20th	Night	3 2 1 3 2 3 4 3 6% 8% 66%	1977
	21st to end	Night	4 1 1 2 3 2 3 2 4 5% 74%	2000
May	1st to 10th	Night	5% 2 1 2 2 2 2 3 4 77%	4540
	11th to 20th	Night	5% 3 1 3 2 3 3 4 6% 7% 64%	4465
	21st to end	Night	2 2 1 3 3 3 4 4 6% 7% 65%	4451
June	1st to 10th	Night	2 1 1 3 3 3 4 4 7% 11% 62%	1800
	11th to 20th	Night	2 2 1 3 2 4 4 4 7% 10% 60%	1800
	21st to end	Night	4 2 1 4 3 3 3 5% 8% 10% 57%	1800
July	1st to 10th	Night	4 3 1 4 3 3 4 4 7% 12% 54%	4347
	11th to 20th	Night	2 1 1 2 2 2 2 3 7% 13% 65%	4540
	21st to end	Night	3 2 1 4 3 4 4 4 9% 13% 51%	4951
August	1st to 10th	Night	1 1 1 2 2 3 3 3 6% 11% 68%	4464
	11th to 20th	Night	2 2 1 4 3 4 5% 5% 9% 15% 51%	4483
	21st to end	Night	4 2 1 3 3 3 5% 3 6% 10% 61%	4993
September	1st to 10th	Night	9% 3 2 5% 4 3 4 4 7% 8% 52%	2000
	11th to 20th	Night	6% 4 1 5% 3 4 5% 4 7% 10% 49%	2103
	21st to end	Night	8% 2 1 3 3 3 5% 4 6% 9% 56%	2090
October	1st to 10th	Night	3 1 1 2 2 2 2 2 3 5% 77%	3480
	11th to 20th	Night	5% 2 2 2 2 2 2 4 5% 74%	3666
	21st to end	Night	2 2 1 1 1 1 1 1 3 3 83%	4120
November	1st to 10th	Night	7% 3 1 2 1 2 2 1 3 5% 73%	2415
	11th to 20th	Night	3 4 1 3 2 2 3 2 4 6% 70%	2600
	21st to end	Night	6% 3 2 3 3 3 3 3 4 5% 64%	2600
December	1st to 10th	Night	9% 5% 1 3 2 3 4 4 5% 5% 59%	4250
	11th to 20th	Night	2 3 1 3 2 2 2 2 4 7% 71%	4816
	21st to end	Night	2 3 1 2 2 2 2 2 2 5% 78%	6467

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	18% 2 6% 13% 29% 32%	4538
	11th to 20th	Day	15% 2 5% 18% 35% 26%	4540
	21st to end	Day	19% 3 5% 19% 26% 27%	4994
February	1st to 10th	Day	21% 2 7% 12% 25% 33%	2000
	11th to 20th	Day	22% 3 7% 13% 25% 30%	1959
	21st to end	Day	18% 3 4 11% 27% 37%	1650
March	1st to 10th	Day	20% 2 5% 7% 20% 45%	4500
	11th to 20th	Day	24% 3 5% 7% 20% 41%	4803
	21st to end	Day	19% 2 6% 6% 25% 42%	5955
April	1st to 10th	Day	17% 3 6% 11% 26% 36%	2400
	11th to 20th	Day	17% 4 7% 9% 26% 36%	2374
	21st to end	Day	15% 2 5% 12% 29% 38%	2400
May	1st to 10th	Day	13% 3 5% 14% 23% 43%	5440
	11th to 20th	Day	17% 3 6% 9% 26% 37%	5449
	21st to end	Day	14% 6% 8% 16% 18% 39%	6447
June	1st to 10th	Day	15% 5% 12% 20% 27% 21%	2600
	11th to 20th	Day	16% 4 10% 15% 25% 31%	2600
	21st to end	Day	25% 6% 10% 18% 24% 17%	2600
July	1st to 10th	Day	25% 7% 12% 25% 25% 6%	5567
	11th to 20th	Day	17% 6% 13% 33% 24% 7%	5377
	21st to end	Day	24% 7% 15% 26% 23% 5%	5752
August	1st to 10th	Day	16% 6% 11% 27% 33% 7%	3892
	11th to 20th	Day	23% 8% 11% 23% 29% 6%	3882
	21st to end	Day	26% 8% 12% 23% 26% 5%	4311
September	1st to 10th	Day	34% 8% 11% 16% 17% 14%	2400
	11th to 20th	Day	34% 10% 12% 15% 19% 10%	2253
	21st to end	Day	27% 7% 9% 17% 24% 16%	2090
October	1st to 10th	Day	13% 3 5% 10% 22% 46%	3480
	11th to 20th	Day	14% 3 5% 21% 20% 37%	3254
	21st to end	Day	10% 1 3 14% 41% 31%	3438
November	1st to 10th	Day	16% 2 6% 18% 28% 30%	1861
	11th to 20th	Day	18% 4 7% 18% 25% 28%	1800
	21st to end	Day	22% 3 6% 16% 27% 26%	1800
December	1st to 10th	Day	30% 3 6% 18% 23% 20%	2940
	11th to 20th	Day	15% 3 5% 17% 35% 25%	3389
	21st to end	Day	11% 2 3 12% 35% 36%	4552
January	1st to 10th	Night	19% 2 5% 11% 32% 32%	5428
	11th to 20th	Night	14% 2 5% 16% 31% 32%	5440
	21st to end	Night	22% 3 5% 17% 26% 26%	5984
February	1st to 10th	Night	19% 3 6% 11% 24% 38%	2400
	11th to 20th	Night	24% 3 7% 12% 22% 32%	2338
	21st to end	Night	19% 3 6% 9% 23% 42%	1980
March	1st to 10th	Night	20% 2 4 7% 20% 47%	5374
	11th to 20th	Night	22% 3 5% 7% 18% 45%	5185
	21st to end	Night	18% 3 7% 7% 22% 44%	4996
April	1st to 10th	Night	21% 3 6% 9% 23% 38%	2000
	11th to 20th	Night	16% 4 9% 12% 21% 38%	1977
	21st to end	Night	14% 2 7% 13% 25% 40%	2000
May	1st to 10th	Night	13% 2 4 15% 20% 46%	4537
	11th to 20th	Night	19% 4 6% 11% 26% 34%	4466
	21st to end	Night	17% 5% 10% 13% 16% 40%	4452
June	1st to 10th	Night	16% 6% 10% 23% 26% 18%	1800
	11th to 20th	Night	19% 4 9% 17% 27% 26%	1800
	21st to end	Night	21% 6% 13% 20% 22% 18%	1800
July	1st to 10th	Night	24% 7% 12% 33% 21% 4	4297
	11th to 20th	Night	12% 4 13% 37% 28% 6%	4480
	21st to end	Night	21% 7% 14% 31% 23% 4	4808
August	1st to 10th	Night	13% 4 10% 29% 35% 8%	3244
	11th to 20th	Night	17% 8% 12% 29% 28% 5%	3243
	21st to end	Night	20% 6% 14% 30% 25% 6%	3597
September	1st to 10th	Night	29% 6% 13% 21% 16% 14%	2000
	11th to 20th	Night	29% 8% 15% 20% 16% 12%	2103
	21st to end	Night	24% 6% 11% 18% 23% 17%	2090
October	1st to 10th	Night	11% 4 8% 12% 14% 51%	3480
	11th to 20th	Night	14% 3 8% 19% 16% 40%	3666
	21st to end	Night	10% 1 3 12% 35% 38%	4120
November	1st to 10th	Night	17% 2 5% 13% 33% 31%	2415
	11th to 20th	Night	17% 3 5% 18% 26% 30%	2600
	21st to end	Night	23% 2 6% 13% 29% 27%	2600
December	1st to 10th	Night	27% 4 6% 17% 24% 22%	4250
	11th to 20th	Night	16% 2 4 12% 34% 31%	4817
	21st to end	Night	12% 2 3 11% 39% 33%	6467

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% 13% 34% 30% 14% 1	300
	11th to 20th	Day	10% 11% 32% 29% 16% 2	300
	21st to end	Day	5% 14% 35% 32% 12% 2	330
February	1st to 10th	Day	8% 13% 29% 30% 17% 3	300
	11th to 20th	Day	11% 15% 32% 31% 11%	300
	21st to end	Day	6% 15% 43% 26% 8% 1	249
March	1st to 10th	Day	7% 13% 41% 29% 10%	300
	11th to 20th	Day	12% 16% 39% 23% 8% 2	407
	21st to end	Day	7% 17% 42% 27% 6% 1	550
April	1st to 10th	Day	7% 14% 42% 29% 6% 2	500
	11th to 20th	Day	6% 15% 45% 27% 6% 1	492
	21st to end	Day	7% 14% 39% 32% 8%	500
May	1st to 10th	Day	5% 12% 41% 31% 10% 1	503
	11th to 20th	Day	6% 8% 34% 37% 13% 2	543
	21st to end	Day	4 3 30% 44% 18% 1	789
June	1st to 10th	Day	3 2 15% 49% 28% 4	730
	11th to 20th	Day	2 2 14% 46% 31% 5%	730
	21st to end	Day	4 1 9% 36% 37% 12%	730
July	1st to 10th	Day	5% 7% 25% 44% 19%	608
	11th to 20th	Day	2 2 31% 42% 22%	524
	21st to end	Day	3 5% 28% 45% 19%	575
August	1st to 10th	Day	2 1 2 24% 48% 24%	527
	11th to 20th	Day	3 2 6% 29% 38% 22%	517
	21st to end	Day	5% 1 5% 23% 46% 20%	583
September	1st to 10th	Day	10% 1 8% 28% 41% 13%	530
	11th to 20th	Day	7% 2 7% 31% 37% 17%	399
	21st to end	Day	10% 1 8% 31% 32% 18%	300
October	1st to 10th	Day	8% 2 13% 35% 29% 13%	300
	11th to 20th	Day	8% 3 19% 37% 25% 7%	300
	21st to end	Day	8% 7% 21% 31% 22% 11%	330
November	1st to 10th	Day	11% 4 24% 34% 22% 4	300
	11th to 20th	Day	8% 9% 22% 30% 25% 6%	300
	21st to end	Day	9% 15% 29% 30% 13% 3	300
December	1st to 10th	Day	11% 12% 20% 36% 19% 2	300
	11th to 20th	Day	3 13% 29% 37% 16% 2	300
	21st to end	Day	5% 13% 31% 35% 15% 1	330
January	1st to 10th	Night	8% 7% 30% 40% 13% 2	800
	11th to 20th	Night	8% 7% 30% 39% 14% 2	800
	21st to end	Night	6% 9% 31% 40% 14% 1	880
February	1st to 10th	Night	6% 10% 27% 39% 17% 1	800
	11th to 20th	Night	8% 7% 36% 38% 11% 1	784
	21st to end	Night	7% 9% 43% 35% 6%	660
March	1st to 10th	Night	8% 9% 36% 36% 11% 1	800
	11th to 20th	Night	9% 11% 30% 36% 13% 1	800
	21st to end	Night	4 8% 43% 36% 8%	672
April	1st to 10th	Night	7% 9% 38% 38% 8%	600
	11th to 20th	Night	3 9% 42% 40% 6%	593
	21st to end	Night	4 7% 38% 41% 10%	600
May	1st to 10th	Night	6% 6% 37% 43% 9%	600
	11th to 20th	Night	8% 3 29% 47% 12% 1	591
	21st to end	Night	3 4 35% 45% 14%	650
June	1st to 10th	Night	2 2 26% 55% 16%	600
	11th to 20th	Night	2 1 23% 58% 16% 1	600
	21st to end	Night	4 2 17% 53% 24% 1	600
July	1st to 10th	Night	4 1 10% 44% 38% 3	585
	11th to 20th	Night	3 7% 48% 39% 3	582
	21st to end	Night	1 1 5% 50% 40% 2	657
August	1st to 10th	Night	3 3 39% 53% 2	597
	11th to 20th	Night	3 1 5% 31% 54% 5%	594
	21st to end	Night	4 1 4 35% 51% 5%	660
September	1st to 10th	Night	9% 1 5% 36% 43% 6%	600
	11th to 20th	Night	8% 1 6% 45% 38% 2	594
	21st to end	Night	9% 1 7% 43% 37% 4	570
October	1st to 10th	Night	6% 1 14% 49% 28% 3	570
	11th to 20th	Night	10% 2 15% 45% 24% 3	687
	21st to end	Night	5% 4 18% 40% 27% 7%	836
November	1st to 10th	Night	8% 2 20% 39% 26% 5%	855
	11th to 20th	Night	5% 4 22% 40% 26% 2	1000
	21st to end	Night	7% 7% 25% 41% 18% 2	1000
December	1st to 10th	Night	9% 5% 24% 41% 19% 2	1000
	11th to 20th	Night	4 7% 32% 43% 13% 1	1000
	21st to end	Night	6% 9% 31% 41% 11% 2	1090

Page generated at 2025-09-16 00:49:13. Version ac07

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