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 2024-09-29.

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	5% 4 2 4 3 3 3 3 5% 7% 61%	101196
	Night	5% 4 1 4 3 3 4 3 5% 7% 59%	97092
Transparency	Day	22% 6% 10% 23% 27% 13%	100951
	Night	22% 6% 10% 22% 26% 14%	96927
Seeing	Day	7% 7% 29% 33% 19% 5%	15225
	Night	7% 8% 39% 36% 10%	25118

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% 10% 2 6% 3 3 3 2 4 5% 55%	2712
	11th to 20th	Day	4 3 1 4 2 4 3 3 4 5% 68%	2850
	21st to end	Day	8% 6% 2 5% 3 3 3 4 5% 7% 54%	3459
February	1st to 10th	Day	6% 8% 2 5% 3 3 2 3 5% 5% 59%	1900
	11th to 20th	Day	5% 6% 2 6% 4 3 3 3 4 6% 58%	1849
	21st to end	Day	4 4 1 4 3 3 4 3 5% 6% 62%	1570
March	1st to 10th	Day	4 5% 1 3 2 2 3 3 4 7% 65%	3130
	11th to 20th	Day	7% 5% 2 6% 4 3 3 2 4 6% 59%	3343
	21st to end	Day	6% 6% 3 6% 4 4 4 3 6% 6% 52%	3991
April	1st to 10th	Day	6% 2 1 3 2 3 3 3 4 6% 66%	2280
	11th to 20th	Day	7% 5% 2 4 2 3 3 3 5% 6% 60%	2251
	21st to end	Day	7% 3 1 4 3 2 3 2 6% 7% 62%	2308
May	1st to 10th	Day	8% 4 1 3 3 3 4 3 4 6% 61%	4120
	11th to 20th	Day	7% 4 2 4 3 3 3 3 5% 6% 59%	4082
	21st to end	Day	6% 3 1 4 2 2 3 3 4 5% 66%	4489
June	1st to 10th	Day	5% 3 1 4 3 5% 4 4 7% 8% 55%	2470
	11th to 20th	Day	3 2 1 3 2 3 4 3 6% 7% 65%	2587
	21st to end	Day	2 3 1 3 3 3 4 4 7% 9% 60%	2660
July	1st to 10th	Day	7% 4 2 4 3 4 4 4 6% 8% 55%	4430
	11th to 20th	Day	3 2 1 4 3 4 4 4 6% 8% 61%	4223
	21st to end	Day	3 2 1 4 3 4 4 3 6% 9% 62%	4466
August	1st to 10th	Day	3 2 1 4 3 4 5% 4 6% 8% 57%	3862
	11th to 20th	Day	3 2 1 3 3 3 3 3 6% 9% 65%	3726
	21st to end	Day	5% 3 1 4 3 4 4 4 7% 10% 55%	4180
September	1st to 10th	Day	6% 4 2 4 4 4 4 3 6% 7% 58%	2263
	11th to 20th	Day	7% 4 1 4 3 3 3 3 4 7% 59%	2090
	21st to end	Day	6% 3 1 3 2 3 3 2 4 6% 67%	2068
October	1st to 10th	Day	10% 4 2 4 3 2 3 2 4 6% 60%	1980
	11th to 20th	Day	6% 4 1 3 1 2 3 2 3 3 72%	1958
	21st to end	Day	7% 5% 1 3 2 2 2 2 3 4 70%	1800
November	1st to 10th	Day	3 4 1 3 2 3 2 2 4 7% 70%	1673
	11th to 20th	Day	2 4 1 3 3 3 3 2 5% 6% 70%	1710
	21st to end	Day	8% 5% 2 4 2 3 2 3 3 5% 63%	1710
December	1st to 10th	Day	4 4 2 4 2 3 4 4 5% 6% 62%	1710
	11th to 20th	Day	6% 5% 1 4 3 4 4 3 5% 7% 59%	2161
	21st to end	Day	6% 7% 2 6% 4 3 3 4 4 5% 57%	3135
January	1st to 10th	Night	4 7% 3 6% 4 4 3 3 5% 7% 54%	4108
	11th to 20th	Night	3 4 1 4 3 3 4 3 5% 7% 61%	4120
	21st to end	Night	6% 6% 2 5% 4 3 3 3 5% 6% 57%	4235
February	1st to 10th	Night	5% 6% 2 5% 4 3 3 3 4 5% 60%	2280
	11th to 20th	Night	6% 6% 2 5% 5% 4 3 3 4 6% 57%	2218
	21st to end	Night	6% 3 1 4 3 4 4 3 5% 8% 60%	1884
March	1st to 10th	Night	3 6% 2 4 3 3 3 3 4 5% 66%	3734
	11th to 20th	Night	7% 4 2 5% 3 4 4 3 5% 7% 57%	3619
	21st to end	Night	4 4 2 4 4 4 4 3 5% 7% 58%	3642
April	1st to 10th	Night	5% 3 1 3 2 2 3 3 5% 8% 65%	1900
	11th to 20th	Night	8% 3 1 4 3 3 3 4 5% 6% 59%	1877
	21st to end	Night	7% 4 1 3 3 3 3 3 4 8% 60%	1872
May	1st to 10th	Night	8% 4 1 4 2 3 3 3 5% 6% 61%	2850
	11th to 20th	Night	8% 4 1 5% 4 4 4 4 5% 7% 55%	2823
	21st to end	Night	6% 4 2 4 3 3 3 3 4 6% 62%	3098
June	1st to 10th	Night	5% 2 1 3 3 3 4 4 8% 13% 54%	1710
	11th to 20th	Night	3 2 1 2 3 3 4 3 8% 9% 61%	1586
	21st to end	Night	4 2 1 4 3 4 5% 4 6% 8% 59%	1520
July	1st to 10th	Night	5% 3 2 5% 5% 5% 5% 4 7% 9% 51%	2540
	11th to 20th	Night	3 3 2 5% 5% 5% 5% 5% 7% 9% 50%	2739
	21st to end	Night	3 3 1 4 3 4 5% 4 9% 12% 53%	3097
August	1st to 10th	Night	4 3 1 5% 4 5% 6% 5% 8% 12% 46%	3059
	11th to 20th	Night	4 3 1 5% 4 5% 5% 5% 7% 12% 49%	3113
	21st to end	Night	4 3 1 4 3 5% 5% 5% 9% 12% 49%	3487
September	1st to 10th	Night	5% 3 1 4 3 3 4 3 6% 8% 59%	1915
	11th to 20th	Night	7% 4 2 4 4 3 4 3 5% 7% 58%	2090
	21st to end	Night	5% 2 1 3 2 2 3 3 5% 6% 68%	2079
October	1st to 10th	Night	8% 4 2 5% 2 3 3 2 4 5% 61%	1980
	11th to 20th	Night	6% 4 1 2 2 2 2 2 3 4 72%	1998
	21st to end	Night	6% 4 1 3 2 2 3 2 4 5% 69%	2536
November	1st to 10th	Night	4 3 1 2 2 2 2 2 4 7% 71%	2405
	11th to 20th	Night	2 2 1 3 3 3 3 3 3 5% 73%	2470
	21st to end	Night	7% 4 1 3 2 3 3 2 4 7% 63%	2470
December	1st to 10th	Night	5% 5% 1 4 3 3 3 3 4 6% 62%	2470
	11th to 20th	Night	5% 4 2 4 4 3 3 2 6% 7% 60%	3036
	21st to end	Night	5% 4 1 5% 3 4 4 3 6% 7% 58%	4532

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	31% 4 6% 21% 31% 6%	2713
	11th to 20th	Day	19% 4 9% 28% 31% 8%	2850
	21st to end	Day	28% 5% 8% 24% 29% 6%	3459
February	1st to 10th	Day	27% 4 10% 23% 25% 12%	1900
	11th to 20th	Day	27% 4 7% 25% 24% 13%	1859
	21st to end	Day	22% 3 6% 19% 33% 17%	1570
March	1st to 10th	Day	20% 4 6% 17% 25% 29%	3130
	11th to 20th	Day	26% 5% 8% 23% 28% 10%	3343
	21st to end	Day	27% 9% 9% 20% 24% 11%	3991
April	1st to 10th	Day	20% 3 7% 19% 28% 22%	2280
	11th to 20th	Day	24% 5% 8% 19% 24% 19%	2254
	21st to end	Day	21% 5% 10% 24% 27% 11%	2308
May	1st to 10th	Day	22% 7% 9% 19% 22% 21%	4120
	11th to 20th	Day	23% 8% 10% 21% 26% 12%	4086
	21st to end	Day	20% 7% 10% 18% 21% 24%	4489
June	1st to 10th	Day	23% 9% 15% 27% 17% 10%	2470
	11th to 20th	Day	17% 6% 11% 20% 27% 18%	2587
	21st to end	Day	18% 7% 13% 28% 21% 13%	2660
July	1st to 10th	Day	26% 6% 11% 24% 26% 6%	4361
	11th to 20th	Day	19% 6% 12% 27% 29% 7%	4150
	21st to end	Day	19% 6% 12% 30% 26% 8%	4325
August	1st to 10th	Day	21% 7% 14% 28% 19% 11%	3849
	11th to 20th	Day	17% 6% 9% 23% 34% 11%	3762
	21st to end	Day	23% 6% 12% 29% 25% 6%	4179
September	1st to 10th	Day	26% 6% 11% 20% 24% 12%	2263
	11th to 20th	Day	26% 5% 9% 20% 31% 9%	2090
	21st to end	Day	20% 4 9% 22% 33% 13%	2068
October	1st to 10th	Day	27% 6% 10% 20% 25% 13%	1980
	11th to 20th	Day	19% 3 6% 14% 36% 22%	1958
	21st to end	Day	21% 4 6% 21% 33% 15%	1800
November	1st to 10th	Day	16% 2 8% 19% 36% 18%	1673
	11th to 20th	Day	17% 3 7% 27% 33% 14%	1710
	21st to end	Day	25% 3 5% 17% 32% 18%	1710
December	1st to 10th	Day	22% 5% 10% 26% 27% 10%	1710
	11th to 20th	Day	25% 5% 8% 20% 29% 13%	2159
	21st to end	Day	25% 7% 8% 21% 26% 12%	3135
January	1st to 10th	Night	27% 6% 9% 26% 26% 7%	4108
	11th to 20th	Night	19% 7% 12% 24% 28% 10%	4120
	21st to end	Night	26% 7% 11% 20% 29% 8%	4235
February	1st to 10th	Night	27% 4 8% 20% 28% 14%	2280
	11th to 20th	Night	28% 4 7% 19% 25% 16%	2218
	21st to end	Night	23% 3 5% 19% 29% 21%	1884
March	1st to 10th	Night	20% 5% 5% 16% 24% 30%	3734
	11th to 20th	Night	23% 8% 11% 21% 24% 14%	3619
	21st to end	Night	22% 8% 9% 25% 22% 14%	3642
April	1st to 10th	Night	17% 5% 9% 20% 25% 23%	1900
	11th to 20th	Night	24% 6% 9% 21% 23% 18%	1877
	21st to end	Night	22% 6% 11% 25% 22% 13%	1872
May	1st to 10th	Night	21% 8% 12% 17% 18% 24%	2850
	11th to 20th	Night	27% 10% 12% 17% 23% 12%	2824
	21st to end	Night	22% 8% 11% 15% 16% 28%	3099
June	1st to 10th	Night	20% 10% 18% 26% 16% 9%	1710
	11th to 20th	Night	16% 8% 14% 20% 24% 18%	1586
	21st to end	Night	20% 7% 15% 26% 19% 13%	1520
July	1st to 10th	Night	27% 8% 13% 30% 18% 4	2500
	11th to 20th	Night	27% 7% 13% 19% 28% 7%	2689
	21st to end	Night	21% 6% 12% 30% 25% 6%	2999
August	1st to 10th	Night	27% 6% 14% 21% 21% 10%	3049
	11th to 20th	Night	25% 7% 12% 22% 25% 9%	3143
	21st to end	Night	24% 7% 14% 28% 22% 6%	3487
September	1st to 10th	Night	22% 6% 12% 24% 23% 12%	1915
	11th to 20th	Night	26% 6% 10% 22% 26% 10%	2090
	21st to end	Night	16% 5% 9% 23% 30% 16%	2079
October	1st to 10th	Night	26% 5% 9% 17% 27% 16%	1980
	11th to 20th	Night	17% 4 6% 15% 34% 23%	1998
	21st to end	Night	19% 3 6% 22% 31% 19%	2536
November	1st to 10th	Night	14% 4 8% 20% 33% 21%	2405
	11th to 20th	Night	15% 3 5% 25% 35% 16%	2470
	21st to end	Night	23% 3 5% 19% 30% 20%	2470
December	1st to 10th	Night	23% 4 9% 24% 28% 12%	2470
	11th to 20th	Night	23% 4 7% 20% 35% 12%	3037
	21st to end	Night	22% 6% 10% 23% 27% 13%	4532

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% 34% 9% 1	270
	11th to 20th	Day	11% 15% 35% 29% 9% 1	270
	21st to end	Day	6% 8% 40% 31% 11% 3	297
February	1st to 10th	Day	9% 13% 34% 36% 8%	270
	11th to 20th	Day	10% 13% 43% 24% 8% 2	270
	21st to end	Day	12% 11% 53% 20% 5%	225
March	1st to 10th	Day	5% 10% 46% 31% 7% 1	270
	11th to 20th	Day	14% 14% 35% 24% 11% 1	270
	21st to end	Day	13% 16% 39% 22% 9% 1	397
April	1st to 10th	Day	10% 17% 42% 23% 7% 1	460
	11th to 20th	Day	10% 19% 41% 23% 7%	452
	21st to end	Day	10% 15% 39% 25% 10% 2	488
May	1st to 10th	Day	8% 11% 39% 32% 9% 1	653
	11th to 20th	Day	10% 8% 30% 34% 17% 2	675
	21st to end	Day	6% 9% 38% 32% 14% 1	734
June	1st to 10th	Day	6% 5% 26% 36% 21% 5%	680
	11th to 20th	Day	4 3 33% 40% 17% 4	680
	21st to end	Day	3 2 23% 44% 23% 5%	680
July	1st to 10th	Day	7% 1 15% 37% 27% 13%	671
	11th to 20th	Day	3 10% 44% 33% 10%	668
	21st to end	Day	4 1 11% 35% 38% 11%	739
August	1st to 10th	Day	3 1 13% 39% 35% 9%	539
	11th to 20th	Day	3 1 16% 38% 32% 10%	477
	21st to end	Day	7% 1 12% 39% 31% 9%	539
September	1st to 10th	Day	7% 1 14% 40% 29% 9%	473
	11th to 20th	Day	2 2 15% 46% 25% 10%	300
	21st to end	Day	7% 5% 22% 32% 27% 6%	294
October	1st to 10th	Day	12% 3 31% 29% 23% 3	270
	11th to 20th	Day	5% 7% 34% 34% 18% 2	270
	21st to end	Day	14% 7% 34% 28% 12% 4	297
November	1st to 10th	Day	8% 7% 32% 33% 17% 3	270
	11th to 20th	Day	6% 11% 35% 31% 13% 3	270
	21st to end	Day	14% 12% 31% 28% 10% 4	270
December	1st to 10th	Day	6% 8% 39% 31% 14% 2	270
	11th to 20th	Day	10% 7% 36% 39% 7%	270
	21st to end	Day	14% 14% 45% 17% 9%	297
January	1st to 10th	Night	5% 9% 41% 38% 7%	950
	11th to 20th	Night	8% 9% 39% 34% 9% 1	950
	21st to end	Night	6% 6% 43% 36% 9%	865
February	1st to 10th	Night	7% 10% 43% 34% 5%	760
	11th to 20th	Night	8% 13% 46% 28% 5%	744
	21st to end	Night	8% 14% 50% 25% 3	628
March	1st to 10th	Night	8% 11% 47% 30% 3	760
	11th to 20th	Night	9% 14% 42% 29% 6%	657
	21st to end	Night	7% 18% 51% 21% 2	627
April	1st to 10th	Night	7% 12% 56% 22% 2	570
	11th to 20th	Night	9% 12% 54% 23% 1	563
	21st to end	Night	8% 13% 49% 26% 3	570
May	1st to 10th	Night	8% 10% 48% 29% 4	570
	11th to 20th	Night	9% 8% 41% 35% 6% 1	561
	21st to end	Night	7% 7% 51% 28% 6%	617
June	1st to 10th	Night	5% 5% 44% 35% 10%	570
	11th to 20th	Night	4 6% 51% 34% 6%	570
	21st to end	Night	3 3 38% 44% 12%	570
July	1st to 10th	Night	4 2 26% 46% 21% 1	555
	11th to 20th	Night	3 1 20% 54% 22% 1	552
	21st to end	Night	3 19% 54% 21% 1	624
August	1st to 10th	Night	3 1 20% 51% 25% 1	567
	11th to 20th	Night	6% 2 20% 53% 18% 1	564
	21st to end	Night	4 1 21% 47% 26% 1	627
September	1st to 10th	Night	7% 1 22% 54% 16% 1	570
	11th to 20th	Night	8% 2 34% 42% 14%	570
	21st to end	Night	5% 3 34% 41% 16% 1	567
October	1st to 10th	Night	10% 5% 38% 39% 9% 1	540
	11th to 20th	Night	7% 6% 41% 38% 7% 1	558
	21st to end	Night	9% 9% 34% 31% 16% 1	952
November	1st to 10th	Night	5% 7% 37% 38% 12% 1	925
	11th to 20th	Night	3 10% 39% 37% 10%	950
	21st to end	Night	8% 9% 36% 36% 11%	950
December	1st to 10th	Night	8% 8% 38% 37% 9%	950
	11th to 20th	Night	8% 10% 44% 33% 5%	950
	21st to end	Night	10% 12% 38% 34% 6%	1045

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