Davis Mountains State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Davis Mountains State Park clear sky chart from 2005-11-06 to 2026-10-29.

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	3 3 1 4 3 4 4 4 6% 7% 61%	156510
	Night	3 3 1 3 3 3 3 3 5% 8% 64%	153117
Transparency	Day	20% 5% 8% 18% 26% 23%	151624
	Night	19% 4 9% 19% 25% 24%	149010
Seeing	Day	6% 9% 24% 30% 23% 8%	17224
	Night	5% 5% 22% 40% 25% 2	27291

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	2 3 1 3 2 2 3 3 5% 6% 71%	5885
	11th to 20th	Day	2 2 1 2 2 2 2 2 4 6% 75%	5910
	21st to end	Day	3 4 2 4 3 3 4 3 5% 6% 63%	6468
February	1st to 10th	Day	3 3 2 3 3 4 4 4 6% 6% 64%	2100
	11th to 20th	Day	3 4 1 4 2 3 3 3 4 6% 65%	2049
	21st to end	Day	2 2 1 3 2 2 4 3 5% 7% 69%	1730
March	1st to 10th	Day	2 3 2 4 3 3 3 3 5% 8% 64%	4600
	11th to 20th	Day	5% 4 1 3 2 2 3 3 5% 7% 65%	4941
	21st to end	Day	1 3 2 4 3 4 4 3 5% 7% 64%	6052
April	1st to 10th	Day	3 4 1 3 3 3 4 3 6% 7% 64%	2520
	11th to 20th	Day	2 4 1 4 3 3 4 4 5% 6% 64%	2491
	21st to end	Day	2 3 1 3 3 2 2 2 5% 6% 70%	2520
May	1st to 10th	Day	3 3 1 4 3 2 3 3 4 6% 67%	7057
	11th to 20th	Day	3 3 1 3 2 3 4 3 4 7% 66%	7032
	21st to end	Day	3 2 1 3 3 3 5% 5% 7% 8% 61%	8303
June	1st to 10th	Day	2 1 1 3 3 4 5% 5% 8% 9% 60%	2730
	11th to 20th	Day	2 2 1 4 4 5% 5% 5% 7% 8% 57%	2730
	21st to end	Day	5% 5% 1 5% 5% 4 5% 5% 8% 9% 47%	2730
July	1st to 10th	Day	5% 3 1 4 4 4 6% 5% 7% 8% 52%	7122
	11th to 20th	Day	5% 4 1 6% 5% 6% 7% 5% 8% 9% 43%	7080
	21st to end	Day	3 3 1 4 4 5% 6% 5% 7% 9% 54%	7686
August	1st to 10th	Day	1 1 1 2 3 3 5% 4 7% 11% 60%	6988
	11th to 20th	Day	3 2 1 6% 5% 7% 7% 6% 9% 10% 43%	7003
	21st to end	Day	3 2 1 4 3 4 5% 4 6% 8% 61%	7751
September	1st to 10th	Day	9% 5% 2 6% 5% 6% 6% 5% 7% 8% 42%	2520
	11th to 20th	Day	9% 5% 2 6% 5% 6% 6% 5% 8% 8% 39%	2394
	21st to end	Day	7% 5% 2 5% 4 4 4 4 5% 7% 51%	2310
October	1st to 10th	Day	3 2 1 3 2 2 3 3 4 4 73%	3700
	11th to 20th	Day	4 2 1 4 2 2 3 2 4 5% 70%	3453
	21st to end	Day	2 2 1 2 2 1 2 1 3 6% 79%	3628
November	1st to 10th	Day	4 4 1 2 2 2 2 2 4 4 74%	1990
	11th to 20th	Day	2 3 1 4 3 3 3 3 4 4 69%	1890
	21st to end	Day	5% 4 1 4 3 3 2 2 5% 6% 65%	1890
December	1st to 10th	Day	5% 10% 2 4 2 3 3 2 5% 6% 59%	3030
	11th to 20th	Day	1 2 1 3 2 3 4 3 5% 6% 69%	3481
	21st to end	Day	2 2 1 2 2 2 2 2 4 5% 77%	4746
January	1st to 10th	Night	2 3 1 4 3 3 3 3 4 6% 69%	7038
	11th to 20th	Night	3 3 1 2 2 2 3 2 4 5% 73%	7080
	21st to end	Night	3 4 2 4 3 3 4 4 5% 8% 59%	7746
February	1st to 10th	Night	3 4 1 3 3 2 3 3 5% 7% 65%	2520
	11th to 20th	Night	3 3 1 4 3 4 4 3 5% 6% 61%	2458
	21st to end	Night	3 3 1 3 2 3 3 4 4 7% 67%	2076
March	1st to 10th	Night	2 3 1 3 3 3 3 3 6% 8% 65%	5494
	11th to 20th	Night	4 8% 2 3 2 2 2 2 4 5% 66%	5255
	21st to end	Night	2 3 1 3 3 3 4 3 5% 7% 67%	5143
April	1st to 10th	Night	5% 3 1 4 3 3 4 3 4 6% 64%	2100
	11th to 20th	Night	4 3 1 4 4 3 3 4 5% 7% 63%	2077
	21st to end	Night	2 3 1 2 2 3 3 2 4 6% 72%	2100
May	1st to 10th	Night	2 6% 1 3 3 2 3 3 3 5% 69%	5890
	11th to 20th	Night	4 4 1 3 2 3 3 3 5% 7% 63%	5860
	21st to end	Night	3 3 1 4 4 4 5% 4 6% 7% 59%	5885
June	1st to 10th	Night	2 2 1 3 4 3 4 5% 8% 10% 58%	1890
	11th to 20th	Night	3 2 1 5% 3 4 5% 6% 9% 8% 54%	1890
	21st to end	Night	5% 3 2 4 5% 4 4 4 7% 9% 52%	1890
July	1st to 10th	Night	5% 3 1 4 3 3 4 4 7% 12% 53%	5846
	11th to 20th	Night	3 4 1 3 3 3 4 3 7% 12% 56%	5910
	21st to end	Night	2 2 1 3 3 3 4 4 7% 12% 58%	6423
August	1st to 10th	Night	1 1 1 1 2 2 3 3 5% 10% 71%	5834
	11th to 20th	Night	1 2 1 3 3 4 5% 6% 11% 15% 49%	5853
	21st to end	Night	2 2 1 3 2 3 3 3 5% 9% 68%	6465
September	1st to 10th	Night	7% 5% 1 5% 3 4 5% 4 6% 9% 51%	2100
	11th to 20th	Night	6% 5% 1 5% 4 5% 6% 4 7% 11% 46%	2223
	21st to end	Night	6% 4 2 5% 4 3 5% 4 6% 8% 53%	2310
October	1st to 10th	Night	2 2 1 3 3 2 3 3 4 5% 74%	3700
	11th to 20th	Night	4 2 1 3 2 2 3 3 4 5% 70%	3907
	21st to end	Night	2 2 1 2 1 2 2 1 2 4 81%	4348
November	1st to 10th	Night	4 3 1 3 2 2 2 2 3 5% 73%	2505
	11th to 20th	Night	2 5% 1 3 2 2 3 3 4 5% 69%	2730
	21st to end	Night	4 3 1 4 3 3 3 2 5% 6% 65%	2730
December	1st to 10th	Night	6% 8% 2 4 4 4 4 3 4 5% 57%	4380
	11th to 20th	Night	1 4 1 3 3 2 3 2 4 6% 70%	4946
	21st to end	Night	2 3 1 2 2 2 2 2 3 5% 78%	6515

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	15% 3 5% 21% 28% 29%	5888
	11th to 20th	Day	13% 2 3 18% 38% 26%	5910
	21st to end	Day	22% 3 4 16% 31% 24%	6468
February	1st to 10th	Day	19% 4 6% 13% 25% 33%	2100
	11th to 20th	Day	21% 4 5% 14% 28% 28%	2059
	21st to end	Day	15% 3 5% 13% 32% 33%	1730
March	1st to 10th	Day	17% 3 4 8% 21% 47%	4600
	11th to 20th	Day	17% 4 5% 11% 23% 40%	4941
	21st to end	Day	18% 3 5% 8% 29% 36%	6052
April	1st to 10th	Day	18% 3 6% 13% 27% 32%	2520
	11th to 20th	Day	19% 5% 5% 11% 27% 32%	2494
	21st to end	Day	15% 3 5% 12% 33% 32%	2520
May	1st to 10th	Day	18% 3 6% 15% 23% 36%	7057
	11th to 20th	Day	18% 3 5% 10% 26% 39%	7035
	21st to end	Day	18% 5% 8% 20% 19% 31%	8304
June	1st to 10th	Day	16% 6% 14% 22% 26% 16%	2730
	11th to 20th	Day	19% 6% 9% 17% 27% 21%	2730
	21st to end	Day	28% 6% 12% 22% 19% 12%	2730
July	1st to 10th	Day	27% 7% 14% 25% 23% 4	7064
	11th to 20th	Day	33% 7% 16% 29% 13% 2	7017
	21st to end	Day	23% 6% 15% 27% 25% 4	7516
August	1st to 10th	Day	17% 6% 13% 32% 23% 9%	5532
	11th to 20th	Day	27% 7% 18% 25% 19% 3	5519
	21st to end	Day	21% 6% 12% 27% 29% 6%	6078
September	1st to 10th	Day	36% 9% 13% 19% 14% 10%	2520
	11th to 20th	Day	36% 9% 14% 17% 17% 7%	2394
	21st to end	Day	30% 6% 10% 20% 22% 12%	2310
October	1st to 10th	Day	13% 5% 6% 13% 25% 37%	3700
	11th to 20th	Day	16% 3 9% 20% 21% 31%	3453
	21st to end	Day	10% 2 2 14% 45% 27%	3628
November	1st to 10th	Day	14% 3 7% 17% 29% 29%	1990
	11th to 20th	Day	18% 4 6% 20% 28% 24%	1890
	21st to end	Day	21% 3 6% 18% 30% 22%	1890
December	1st to 10th	Day	28% 3 4 17% 27% 20%	3030
	11th to 20th	Day	16% 3 4 17% 34% 25%	3479
	21st to end	Day	11% 2 3 12% 36% 35%	4746
January	1st to 10th	Night	17% 3 4 17% 31% 27%	7038
	11th to 20th	Night	15% 2 3 15% 29% 36%	7080
	21st to end	Night	24% 4 4 15% 29% 24%	7746
February	1st to 10th	Night	18% 3 6% 13% 26% 34%	2520
	11th to 20th	Night	23% 4 7% 13% 25% 28%	2458
	21st to end	Night	18% 3 5% 9% 29% 37%	2076
March	1st to 10th	Night	16% 3 4 8% 23% 46%	5494
	11th to 20th	Night	16% 9% 4 8% 22% 41%	5255
	21st to end	Night	18% 3 6% 9% 26% 39%	5143
April	1st to 10th	Night	22% 4 5% 13% 26% 30%	2100
	11th to 20th	Night	20% 4 7% 13% 24% 31%	2077
	21st to end	Night	14% 4 6% 16% 28% 33%	2100
May	1st to 10th	Night	18% 4 6% 15% 22% 35%	5888
	11th to 20th	Night	20% 4 5% 14% 24% 33%	5861
	21st to end	Night	22% 4 10% 19% 15% 29%	5887
June	1st to 10th	Night	17% 7% 14% 26% 23% 12%	1890
	11th to 20th	Night	21% 6% 11% 20% 26% 17%	1890
	21st to end	Night	25% 7% 13% 22% 21% 12%	1890
July	1st to 10th	Night	24% 7% 19% 31% 18% 2	5796
	11th to 20th	Night	21% 7% 22% 34% 15% 2	5850
	21st to end	Night	19% 6% 18% 32% 24% 1	6280
August	1st to 10th	Night	11% 4 13% 35% 30% 7%	4614
	11th to 20th	Night	20% 6% 27% 31% 15% 1	4613
	21st to end	Night	15% 5% 14% 31% 29% 5%	5069
September	1st to 10th	Night	28% 9% 16% 23% 16% 9%	2100
	11th to 20th	Night	29% 9% 19% 21% 15% 8%	2223
	21st to end	Night	26% 7% 13% 22% 20% 11%	2310
October	1st to 10th	Night	13% 5% 8% 13% 23% 38%	3700
	11th to 20th	Night	16% 4 11% 19% 19% 32%	3907
	21st to end	Night	11% 2 3 13% 41% 29%	4348
November	1st to 10th	Night	15% 3 5% 15% 33% 29%	2505
	11th to 20th	Night	16% 4 5% 19% 28% 27%	2730
	21st to end	Night	20% 3 6% 16% 31% 23%	2730
December	1st to 10th	Night	30% 3 5% 15% 27% 19%	4380
	11th to 20th	Night	16% 3 3 14% 35% 29%	4947
	21st to end	Night	13% 2 3 13% 37% 32%	6515

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% 22% 31% 27% 11% 2	330
	11th to 20th	Day	8% 14% 36% 28% 13% 1	330
	21st to end	Day	6% 18% 36% 28% 9% 3	363
February	1st to 10th	Day	8% 12% 32% 27% 19% 2	330
	11th to 20th	Day	10% 17% 39% 23% 9% 1	330
	21st to end	Day	7% 17% 43% 23% 9% 1	273
March	1st to 10th	Day	8% 16% 45% 21% 10% 1	330
	11th to 20th	Day	11% 17% 39% 22% 8% 3	462
	21st to end	Day	6% 18% 42% 23% 9% 1	594
April	1st to 10th	Day	6% 17% 43% 23% 9% 2	540
	11th to 20th	Day	6% 20% 45% 22% 6% 1	532
	21st to end	Day	5% 16% 45% 28% 6% 1	540
May	1st to 10th	Day	4 13% 44% 27% 10% 2	543
	11th to 20th	Day	5% 11% 35% 36% 11% 3	568
	21st to end	Day	4 4 33% 40% 17% 2	808
June	1st to 10th	Day	2 2 17% 44% 30% 4	780
	11th to 20th	Day	2 2 13% 44% 35% 5%	780
	21st to end	Day	6% 2 7% 33% 41% 12%	780
July	1st to 10th	Day	5% 2 5% 29% 39% 20%	583
	11th to 20th	Day	4 1 3 30% 42% 20%	564
	21st to end	Day	3 1 4 31% 42% 19%	619
August	1st to 10th	Day	3 1 3 21% 46% 26%	567
	11th to 20th	Day	5% 3 4 25% 40% 23%	557
	21st to end	Day	7% 2 3 25% 40% 23%	627
September	1st to 10th	Day	8% 3 5% 32% 35% 17%	570
	11th to 20th	Day	8% 2 7% 30% 37% 17%	444
	21st to end	Day	9% 2 11% 33% 31% 15%	360
October	1st to 10th	Day	7% 3 13% 33% 34% 11%	360
	11th to 20th	Day	6% 5% 23% 35% 24% 7%	360
	21st to end	Day	6% 9% 26% 31% 17% 10%	387
November	1st to 10th	Day	7% 8% 27% 31% 21% 5%	330
	11th to 20th	Day	7% 9% 26% 33% 17% 8%	330
	21st to end	Day	8% 17% 32% 27% 12% 4	330
December	1st to 10th	Day	10% 11% 31% 32% 14% 2	330
	11th to 20th	Day	5% 15% 35% 29% 14% 2	330
	21st to end	Day	5% 17% 36% 29% 11% 2	363
January	1st to 10th	Night	6% 8% 33% 39% 12% 2	840
	11th to 20th	Night	6% 8% 32% 38% 14% 1	840
	21st to end	Night	5% 9% 34% 39% 13% 1	924
February	1st to 10th	Night	5% 10% 29% 37% 18% 1	840
	11th to 20th	Night	7% 6% 36% 40% 11%	824
	21st to end	Night	5% 11% 40% 38% 6%	692
March	1st to 10th	Night	5% 10% 34% 40% 11% 1	840
	11th to 20th	Night	7% 11% 32% 34% 14% 1	840
	21st to end	Night	3 8% 40% 39% 9% 1	716
April	1st to 10th	Night	5% 10% 33% 40% 12%	630
	11th to 20th	Night	6% 8% 38% 41% 8%	623
	21st to end	Night	2 7% 38% 43% 9% 1	630
May	1st to 10th	Night	4 6% 34% 44% 12% 1	630
	11th to 20th	Night	6% 5% 27% 48% 13% 1	621
	21st to end	Night	3 4 24% 51% 18%	683
June	1st to 10th	Night	2 1 16% 56% 24% 1	630
	11th to 20th	Night	4 1 12% 53% 28% 2	630
	21st to end	Night	6% 2 7% 46% 38% 1	630
July	1st to 10th	Night	4 2 5% 37% 50% 3	615
	11th to 20th	Night	3 2 38% 52% 5%	612
	21st to end	Night	2 1 2 36% 55% 3	690
August	1st to 10th	Night	2 1 1 26% 64% 6%	627
	11th to 20th	Night	3 1 2 25% 62% 8%	624
	21st to end	Night	5% 1 1 28% 60% 5%	693
September	1st to 10th	Night	8% 3 3 26% 55% 5%	630
	11th to 20th	Night	8% 1 4 36% 47% 4	630
	21st to end	Night	8% 2 7% 38% 41% 5%	630
October	1st to 10th	Night	4 3 10% 44% 36% 3	630
	11th to 20th	Night	9% 3 14% 45% 26% 3	768
	21st to end	Night	5% 4 19% 40% 26% 6%	912
November	1st to 10th	Night	7% 2 20% 40% 26% 5%	865
	11th to 20th	Night	5% 5% 23% 42% 24% 2	1050
	21st to end	Night	6% 8% 26% 40% 17% 3	1050
December	1st to 10th	Night	8% 5% 28% 40% 15% 2	1050
	11th to 20th	Night	4 7% 33% 40% 14% 1	1050
	21st to end	Night	4 12% 31% 39% 13% 2	1102

Page generated at 2026-10-26 03:37:51. Version ac07

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