Alibates Flint Quarries Visitor Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Alibates Flint Quarries Visitor Center clear sky chart from 2005-11-06 to 2026-06-16.

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	5% 4 2 4 3 3 3 3 5% 7% 61%	147045
	Night	5% 4 1 4 3 3 4 3 5% 7% 59%	142164
Transparency	Day	23% 5% 9% 22% 28% 14%	142087
	Night	22% 5% 9% 21% 27% 15%	138134
Seeing	Day	7% 7% 29% 33% 18% 4	17493
	Night	7% 8% 40% 36% 9%	27465

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	6% 8% 2 6% 4 4 3 3 4 5% 54%	5061
	11th to 20th	Day	3 5% 1 4 2 2 2 2 3 5% 72%	5310
	21st to end	Day	8% 4 2 5% 3 3 3 3 4 6% 59%	6426
February	1st to 10th	Day	5% 7% 1 5% 3 3 3 3 5% 5% 60%	2100
	11th to 20th	Day	5% 7% 2 6% 4 3 3 3 5% 6% 57%	2049
	21st to end	Day	4 4 1 3 3 3 3 3 5% 6% 65%	1730
March	1st to 10th	Day	7% 5% 1 3 2 3 3 3 4 6% 62%	4600
	11th to 20th	Day	5% 4 2 6% 4 3 3 3 5% 7% 59%	4896
	21st to end	Day	4 5% 2 5% 3 4 4 3 5% 7% 59%	5837
April	1st to 10th	Day	6% 2 1 3 3 3 3 3 4 7% 66%	2520
	11th to 20th	Day	7% 4 2 4 2 3 3 3 5% 6% 60%	2491
	21st to end	Day	7% 4 1 4 3 2 3 3 6% 8% 61%	2551
May	1st to 10th	Day	11% 5% 1 4 3 3 3 3 5% 7% 56%	7655
	11th to 20th	Day	5% 4 1 3 2 2 2 2 4 5% 69%	7627
	21st to end	Day	9% 6% 2 5% 3 3 4 3 5% 5% 56%	8404
June	1st to 10th	Day	5% 4 1 5% 4 4 4 4 7% 8% 54%	2730
	11th to 20th	Day	4 2 1 2 2 3 4 3 6% 7% 65%	2790
	21st to end	Day	3 3 1 3 3 4 4 5% 7% 9% 59%	2800
July	1st to 10th	Day	6% 4 2 5% 4 4 4 4 6% 9% 52%	6339
	11th to 20th	Day	3 2 1 3 3 3 4 4 6% 9% 62%	6042
	21st to end	Day	2 2 1 4 3 4 4 3 6% 9% 63%	6424
August	1st to 10th	Day	3 3 2 4 3 4 5% 4 6% 8% 59%	5467
	11th to 20th	Day	2 2 1 3 4 3 4 4 7% 10% 59%	5366
	21st to end	Day	7% 4 2 5% 4 4 4 3 7% 10% 51%	5984
September	1st to 10th	Day	6% 4 2 4 4 4 4 3 5% 7% 58%	2382
	11th to 20th	Day	7% 4 1 4 3 3 3 3 4 7% 59%	2200
	21st to end	Day	5% 3 1 3 2 3 3 2 4 6% 66%	2200
October	1st to 10th	Day	6% 3 1 2 2 1 2 1 3 4 74%	3590
	11th to 20th	Day	7% 5% 2 5% 2 3 3 2 4 4 63%	3521
	21st to end	Day	4 3 1 2 2 2 2 2 2 4 76%	3222
November	1st to 10th	Day	4 3 1 3 2 3 2 2 3 6% 70%	1853
	11th to 20th	Day	3 3 1 3 2 2 2 2 4 6% 70%	1890
	21st to end	Day	8% 5% 2 4 2 3 2 2 3 6% 63%	1890
December	1st to 10th	Day	2 2 1 3 2 2 3 3 5% 6% 71%	3030
	11th to 20th	Day	4 4 1 3 3 4 4 3 4 6% 64%	3481
	21st to end	Day	5% 7% 3 6% 4 3 3 3 3 5% 58%	4587
January	1st to 10th	Night	4 8% 3 6% 4 4 4 4 6% 7% 51%	7634
	11th to 20th	Night	2 3 1 4 3 3 3 3 4 5% 69%	7680
	21st to end	Night	7% 5% 2 6% 4 3 3 3 5% 6% 56%	7829
February	1st to 10th	Night	5% 5% 2 5% 4 3 3 3 4 6% 61%	2520
	11th to 20th	Night	6% 6% 2 5% 5% 4 3 3 4 6% 56%	2458
	21st to end	Night	5% 3 1 3 3 3 4 3 5% 7% 62%	2076
March	1st to 10th	Night	3 5% 2 4 3 3 3 3 3 5% 67%	5494
	11th to 20th	Night	5% 4 2 4 3 4 4 3 5% 7% 61%	5290
	21st to end	Night	3 3 1 4 3 4 4 3 6% 8% 62%	5330
April	1st to 10th	Night	6% 3 1 3 1 2 3 3 5% 8% 65%	2100
	11th to 20th	Night	8% 3 1 5% 3 3 3 4 5% 6% 59%	2077
	21st to end	Night	7% 4 1 3 3 3 3 3 5% 7% 60%	2069
May	1st to 10th	Night	10% 6% 2 4 3 3 3 3 5% 6% 56%	5292
	11th to 20th	Night	5% 3 1 3 3 3 3 3 4 6% 67%	5265
	21st to end	Night	9% 5% 2 6% 4 4 4 3 5% 7% 52%	5803
June	1st to 10th	Night	5% 3 1 4 3 3 4 4 8% 13% 52%	1890
	11th to 20th	Night	4 2 1 2 3 3 4 3 8% 9% 61%	1712
	21st to end	Night	4 2 2 4 3 5% 5% 4 6% 9% 57%	1600
July	1st to 10th	Night	5% 4 2 6% 5% 5% 5% 4 7% 8% 48%	3640
	11th to 20th	Night	3 3 2 5% 5% 5% 5% 6% 8% 12% 48%	3917
	21st to end	Night	3 3 1 4 4 4 6% 5% 9% 12% 49%	4449
August	1st to 10th	Night	4 3 1 4 4 4 5% 5% 8% 13% 49%	4327
	11th to 20th	Night	3 3 1 5% 4 5% 6% 6% 9% 12% 45%	4483
	21st to end	Night	8% 5% 2 5% 4 5% 5% 4 8% 11% 44%	4993
September	1st to 10th	Night	6% 3 1 4 3 3 4 3 6% 8% 59%	2016
	11th to 20th	Night	7% 4 2 4 4 4 4 3 5% 7% 57%	2200
	21st to end	Night	5% 2 1 4 2 2 3 2 5% 6% 67%	2200
October	1st to 10th	Night	4 2 1 3 1 2 2 2 3 5% 74%	3590
	11th to 20th	Night	5% 4 1 5% 3 3 3 3 4 4 65%	3602
	21st to end	Night	6% 3 1 3 2 2 2 2 3 4 73%	4544
November	1st to 10th	Night	5% 3 1 2 2 2 2 2 4 7% 71%	2665
	11th to 20th	Night	3 2 1 3 2 3 3 3 3 5% 72%	2730
	21st to end	Night	6% 4 1 3 2 3 3 2 4 7% 64%	2730
December	1st to 10th	Night	3 3 1 3 2 2 3 2 4 6% 70%	4380
	11th to 20th	Night	3 3 1 4 3 2 3 2 5% 7% 67%	4946
	21st to end	Night	5% 5% 1 4 3 3 4 3 5% 7% 59%	6633

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	32% 3 5% 23% 28% 8%	5064
	11th to 20th	Day	18% 3 7% 17% 39% 16%	5310
	21st to end	Day	27% 4 7% 17% 35% 10%	6426
February	1st to 10th	Day	25% 4 9% 22% 26% 14%	2100
	11th to 20th	Day	28% 3 7% 24% 24% 12%	2059
	21st to end	Day	20% 3 5% 19% 34% 19%	1730
March	1st to 10th	Day	23% 3 4 13% 24% 32%	4600
	11th to 20th	Day	25% 4 6% 17% 30% 18%	4896
	21st to end	Day	23% 6% 8% 27% 27% 9%	5837
April	1st to 10th	Day	21% 3 7% 19% 29% 20%	2520
	11th to 20th	Day	24% 5% 7% 19% 24% 20%	2494
	21st to end	Day	22% 5% 10% 24% 28% 11%	2551
May	1st to 10th	Day	28% 5% 10% 20% 24% 13%	7655
	11th to 20th	Day	18% 5% 6% 17% 27% 28%	7631
	21st to end	Day	30% 6% 10% 19% 15% 20%	8405
June	1st to 10th	Day	24% 9% 15% 27% 16% 10%	2730
	11th to 20th	Day	17% 6% 11% 21% 28% 17%	2790
	21st to end	Day	19% 7% 13% 27% 21% 13%	2800
July	1st to 10th	Day	28% 7% 11% 21% 27% 5%	6271
	11th to 20th	Day	18% 5% 13% 31% 27% 5%	5969
	21st to end	Day	18% 6% 16% 35% 20% 6%	6240
August	1st to 10th	Day	21% 7% 14% 28% 19% 10%	3972
	11th to 20th	Day	17% 6% 9% 23% 34% 11%	3882
	21st to end	Day	23% 6% 12% 28% 25% 6%	4311
September	1st to 10th	Day	26% 6% 11% 21% 25% 12%	2382
	11th to 20th	Day	26% 5% 9% 21% 30% 9%	2200
	21st to end	Day	20% 4 9% 22% 32% 14%	2200
October	1st to 10th	Day	16% 3 6% 13% 42% 20%	3590
	11th to 20th	Day	24% 4 8% 19% 29% 17%	3521
	21st to end	Day	15% 3 4 21% 38% 19%	3222
November	1st to 10th	Day	17% 2 7% 19% 36% 18%	1853
	11th to 20th	Day	17% 3 6% 26% 33% 15%	1890
	21st to end	Day	25% 3 6% 19% 31% 17%	1890
December	1st to 10th	Day	15% 4 7% 32% 31% 11%	3030
	11th to 20th	Day	21% 4 5% 18% 39% 13%	3479
	21st to end	Day	27% 6% 7% 23% 25% 13%	4587
January	1st to 10th	Night	31% 4 6% 26% 27% 6%	7635
	11th to 20th	Night	16% 4 9% 21% 34% 16%	7680
	21st to end	Night	28% 5% 8% 18% 31% 11%	7829
February	1st to 10th	Night	26% 3 7% 20% 28% 15%	2520
	11th to 20th	Night	30% 4 8% 19% 25% 15%	2458
	21st to end	Night	21% 3 5% 19% 30% 22%	2076
March	1st to 10th	Night	20% 4 4 14% 25% 33%	5494
	11th to 20th	Night	20% 6% 8% 15% 21% 29%	5290
	21st to end	Night	19% 6% 8% 24% 30% 12%	5330
April	1st to 10th	Night	18% 5% 9% 21% 26% 21%	2100
	11th to 20th	Night	25% 6% 9% 20% 23% 18%	2077
	21st to end	Night	22% 6% 11% 25% 23% 13%	2069
May	1st to 10th	Night	28% 6% 11% 21% 20% 14%	5293
	11th to 20th	Night	18% 6% 7% 15% 26% 28%	5266
	21st to end	Night	31% 7% 14% 14% 12% 23%	5805
June	1st to 10th	Night	21% 10% 20% 26% 15% 9%	1890
	11th to 20th	Night	17% 7% 14% 21% 23% 17%	1712
	21st to end	Night	21% 7% 15% 27% 18% 13%	1600
July	1st to 10th	Night	30% 9% 13% 28% 16% 3	3600
	11th to 20th	Night	26% 7% 14% 24% 24% 5%	3867
	21st to end	Night	23% 7% 12% 35% 19% 4	4320
August	1st to 10th	Night	27% 6% 14% 21% 21% 10%	3146
	11th to 20th	Night	25% 7% 12% 23% 25% 9%	3243
	21st to end	Night	25% 7% 14% 27% 22% 6%	3597
September	1st to 10th	Night	23% 6% 12% 24% 23% 12%	2016
	11th to 20th	Night	25% 6% 10% 23% 25% 10%	2200
	21st to end	Night	17% 5% 9% 23% 30% 16%	2200
October	1st to 10th	Night	15% 3 6% 11% 38% 27%	3590
	11th to 20th	Night	21% 5% 8% 18% 29% 20%	3602
	21st to end	Night	17% 2 4 19% 40% 18%	4544
November	1st to 10th	Night	15% 4 8% 20% 33% 21%	2665
	11th to 20th	Night	16% 3 4 24% 36% 17%	2730
	21st to end	Night	22% 3 5% 21% 31% 19%	2730
December	1st to 10th	Night	17% 3 7% 31% 35% 8%	4380
	11th to 20th	Night	18% 3 4 18% 41% 16%	4947
	21st to end	Night	23% 5% 8% 22% 30% 12%	6633

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	6% 13% 37% 33% 9% 1	330
	11th to 20th	Day	10% 15% 37% 27% 10% 1	330
	21st to end	Day	7% 9% 39% 31% 11% 2	363
February	1st to 10th	Day	7% 12% 37% 35% 8% 1	330
	11th to 20th	Day	11% 14% 42% 23% 8% 2	330
	21st to end	Day	10% 10% 50% 24% 7%	273
March	1st to 10th	Day	7% 10% 45% 31% 7% 1	330
	11th to 20th	Day	15% 13% 35% 25% 10% 1	330
	21st to end	Day	11% 14% 40% 23% 10% 1	473
April	1st to 10th	Day	10% 17% 41% 24% 7% 1	540
	11th to 20th	Day	9% 19% 44% 22% 7%	532
	21st to end	Day	10% 15% 40% 25% 9% 1	571
May	1st to 10th	Day	10% 10% 38% 32% 9% 1	753
	11th to 20th	Day	9% 8% 31% 34% 16% 2	775
	21st to end	Day	7% 9% 36% 32% 14% 2	844
June	1st to 10th	Day	6% 5% 27% 37% 20% 4	780
	11th to 20th	Day	4 4 32% 38% 18% 4	756
	21st to end	Day	3 3 24% 44% 22% 4	730
July	1st to 10th	Day	6% 1 15% 38% 27% 12%	721
	11th to 20th	Day	3 1 10% 43% 33% 10%	718
	21st to end	Day	4 1 11% 36% 38% 11%	794
August	1st to 10th	Day	3 1 14% 39% 34% 8%	582
	11th to 20th	Day	3 1 16% 38% 32% 11%	517
	21st to end	Day	7% 2 13% 38% 31% 9%	583
September	1st to 10th	Day	7% 1 15% 40% 29% 8%	512
	11th to 20th	Day	2 2 16% 47% 24% 9%	330
	21st to end	Day	8% 5% 22% 32% 26% 6%	330
October	1st to 10th	Day	10% 3 29% 30% 25% 3	330
	11th to 20th	Day	7% 7% 35% 31% 17% 3	330
	21st to end	Day	13% 9% 32% 29% 12% 5%	363
November	1st to 10th	Day	9% 6% 33% 35% 15% 2	330
	11th to 20th	Day	6% 10% 35% 31% 14% 3	330
	21st to end	Day	13% 12% 34% 27% 12% 4	330
December	1st to 10th	Day	5% 7% 41% 32% 13% 2	330
	11th to 20th	Day	8% 6% 35% 40% 9% 1	330
	21st to end	Day	12% 13% 42% 21% 11% 1	363
January	1st to 10th	Night	5% 10% 43% 35% 7%	1050
	11th to 20th	Night	8% 9% 40% 34% 9% 1	1050
	21st to end	Night	7% 7% 44% 34% 8%	955
February	1st to 10th	Night	6% 10% 45% 33% 5%	840
	11th to 20th	Night	9% 14% 45% 27% 4	824
	21st to end	Night	7% 13% 50% 26% 3	692
March	1st to 10th	Night	8% 13% 48% 29% 3	840
	11th to 20th	Night	9% 14% 43% 29% 6%	726
	21st to end	Night	7% 17% 52% 21% 3	693
April	1st to 10th	Night	8% 12% 54% 23% 2	630
	11th to 20th	Night	9% 13% 54% 22% 1	623
	21st to end	Night	8% 13% 50% 25% 3	630
May	1st to 10th	Night	9% 10% 47% 30% 5%	630
	11th to 20th	Night	8% 8% 43% 34% 6% 1	621
	21st to end	Night	7% 7% 51% 29% 6%	683
June	1st to 10th	Night	5% 6% 45% 34% 10%	630
	11th to 20th	Night	4 6% 51% 34% 6%	615
	21st to end	Night	3 3 38% 44% 12%	600
July	1st to 10th	Night	4 2 27% 46% 21% 1	585
	11th to 20th	Night	3 1 20% 54% 21% 1	582
	21st to end	Night	4 19% 55% 21% 1	657
August	1st to 10th	Night	3 1 22% 50% 24% 1	597
	11th to 20th	Night	6% 2 21% 52% 19% 1	594
	21st to end	Night	5% 1 21% 46% 26% 1	660
September	1st to 10th	Night	7% 1 22% 54% 15% 1	600
	11th to 20th	Night	7% 2 35% 43% 13%	600
	21st to end	Night	5% 3 34% 42% 15% 1	600
October	1st to 10th	Night	9% 5% 37% 40% 9% 1	600
	11th to 20th	Night	7% 7% 43% 37% 6% 1	620
	21st to end	Night	8% 10% 34% 32% 15% 1	1058
November	1st to 10th	Night	6% 7% 39% 36% 11% 1	1025
	11th to 20th	Night	4 10% 39% 37% 10%	1050
	21st to end	Night	7% 10% 36% 37% 10%	1050
December	1st to 10th	Night	8% 7% 39% 37% 9%	1050
	11th to 20th	Night	7% 10% 45% 33% 5%	1050
	21st to end	Night	9% 12% 39% 34% 6%	1155

Page generated at 2026-06-13 01:31:41. Version ac07

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