Eagle Pass
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eagle Pass 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	11% 5% 2 5% 3 3 3 3 5% 7% 52%	125892
	Night	10% 4 2 4 3 3 3 3 5% 7% 56%	123485
Transparency	Day	31% 5% 9% 21% 20% 14%	129809
	Night	28% 5% 10% 21% 20% 16%	127615
Seeing	Day	11% 5% 19% 34% 25% 6%	15777
	Night	11% 4 23% 44% 17% 1	25716

By Month

Percentage Cloud Cover SE (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	14% 7% 2 3 3 2 2 2 3 5% 59%	4097
	11th to 20th	Day	10% 6% 2 4 2 2 3 3 5% 6% 57%	4540
	21st to end	Day	18% 6% 2 5% 3 3 3 3 5% 6% 46%	4994
February	1st to 10th	Day	12% 7% 2 6% 3 3 4 3 4 6% 50%	2000
	11th to 20th	Day	13% 8% 2 3 3 3 3 3 4 7% 52%	1949
	21st to end	Day	10% 5% 1 4 3 3 3 3 6% 6% 56%	1650
March	1st to 10th	Day	10% 5% 2 4 3 3 3 3 5% 6% 55%	4539
	11th to 20th	Day	14% 6% 2 4 3 2 2 2 3 5% 57%	4980
	21st to end	Day	12% 6% 2 5% 3 3 3 3 5% 7% 52%	5462
April	1st to 10th	Day	10% 5% 2 4 4 3 4 3 5% 7% 51%	2273
	11th to 20th	Day	12% 5% 2 4 3 4 3 3 5% 7% 52%	2374
	21st to end	Day	12% 6% 2 5% 4 3 3 3 5% 7% 49%	2400
May	1st to 10th	Day	18% 6% 2 6% 4 4 3 3 5% 8% 41%	5633
	11th to 20th	Day	8% 4 2 5% 3 3 4 4 6% 9% 53%	5862
	21st to end	Day	11% 6% 2 6% 4 4 4 4 7% 10% 40%	6434
June	1st to 10th	Day	4 3 2 4 3 3 4 4 7% 10% 56%	2600
	11th to 20th	Day	4 3 1 5% 3 3 4 4 6% 9% 58%	2600
	21st to end	Day	5% 4 2 5% 6% 5% 5% 5% 6% 9% 49%	2600
July	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 4 5% 7% 45%	5900
	11th to 20th	Day	5% 5% 1 4 3 5% 4 4 6% 10% 53%	5900
	21st to end	Day	5% 4 2 5% 4 4 5% 4 6% 9% 53%	5927
August	1st to 10th	Day	1 1 1 1 2 2 2 2 4 6% 78%	3905
	11th to 20th	Day	2 2 1 2 2 3 3 3 5% 8% 69%	3846
	21st to end	Day	4 3 1 4 3 3 4 4 7% 10% 57%	4312
September	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 4 7% 7% 43%	2236
	11th to 20th	Day	11% 6% 2 6% 4 5% 5% 5% 7% 8% 42%	2178
	21st to end	Day	8% 4 2 5% 3 4 4 4 6% 8% 52%	2090
October	1st to 10th	Day	8% 4 2 4 3 3 4 3 4 7% 58%	2090
	11th to 20th	Day	13% 6% 2 5% 4 4 3 3 4 7% 50%	2090
	21st to end	Day	13% 5% 1 4 2 2 2 2 3 4 62%	2163
November	1st to 10th	Day	14% 6% 2 6% 3 3 3 2 4 6% 50%	1849
	11th to 20th	Day	12% 5% 2 4 3 4 3 3 4 6% 53%	1800
	21st to end	Day	14% 7% 2 5% 3 3 3 3 4 5% 51%	1800
December	1st to 10th	Day	30% 8% 2 5% 3 3 3 2 4 4 36%	2940
	11th to 20th	Day	14% 7% 3 6% 3 4 3 3 4 6% 47%	3391
	21st to end	Day	10% 7% 2 4 3 2 2 2 3 4 60%	4488
January	1st to 10th	Night	13% 5% 2 4 2 2 2 2 5% 6% 58%	5888
	11th to 20th	Night	11% 4 1 3 2 2 2 3 4 5% 64%	5462
	21st to end	Night	23% 6% 2 5% 3 3 2 2 4 5% 46%	5984
February	1st to 10th	Night	10% 5% 2 4 3 3 3 3 5% 5% 58%	2400
	11th to 20th	Night	13% 6% 2 5% 2 2 3 2 4 6% 56%	2338
	21st to end	Night	10% 5% 2 4 3 4 3 3 5% 6% 55%	1980
March	1st to 10th	Night	9% 4 1 4 3 4 4 4 5% 7% 56%	5332
	11th to 20th	Night	13% 4 2 4 3 2 2 2 3 6% 58%	4980
	21st to end	Night	9% 5% 1 4 3 2 3 3 5% 6% 59%	5467
April	1st to 10th	Night	8% 4 2 4 3 3 4 4 7% 7% 54%	2120
	11th to 20th	Night	12% 5% 2 5% 3 3 4 3 5% 6% 53%	1977
	21st to end	Night	12% 6% 1 4 3 4 3 3 5% 7% 53%	2000
May	1st to 10th	Night	18% 5% 2 6% 3 3 3 3 5% 6% 46%	4280
	11th to 20th	Night	8% 3 1 5% 3 3 4 3 6% 8% 55%	4053
	21st to end	Night	9% 5% 2 5% 3 4 4 4 8% 11% 45%	4443
June	1st to 10th	Night	3 2 1 4 3 2 4 3 6% 10% 62%	1800
	11th to 20th	Night	2 2 1 3 3 3 3 4 6% 9% 64%	1800
	21st to end	Night	4 3 2 3 4 4 5% 4 7% 12% 54%	1800
July	1st to 10th	Night	8% 4 2 5% 4 4 5% 4 6% 10% 48%	4078
	11th to 20th	Night	3 4 2 5% 4 4 5% 4 7% 8% 56%	4077
	21st to end	Night	5% 3 1 4 3 3 4 4 5% 9% 58%	4938
August	1st to 10th	Night	1 1 2 2 2 2 2 4 7% 78%	3255
	11th to 20th	Night	2 2 1 3 2 3 4 4 5% 9% 65%	3213
	21st to end	Night	4 3 1 4 4 4 4 4 6% 11% 55%	3597
September	1st to 10th	Night	7% 5% 2 6% 4 5% 4 4 7% 9% 46%	2161
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 6% 9% 47%	2178
	21st to end	Night	10% 3 2 4 3 3 3 3 5% 8% 54%	2090
October	1st to 10th	Night	7% 4 1 3 2 3 3 2 5% 7% 62%	2090
	11th to 20th	Night	12% 4 2 4 2 2 3 2 4 5% 59%	2090
	21st to end	Night	8% 3 1 3 2 2 2 2 3 4 69%	2413
November	1st to 10th	Night	12% 5% 2 4 3 2 2 2 3 5% 59%	2445
	11th to 20th	Night	10% 5% 2 4 3 2 3 3 4 5% 60%	2600
	21st to end	Night	13% 5% 1 5% 3 3 3 3 5% 5% 53%	2600
December	1st to 10th	Night	28% 6% 2 4 3 3 3 3 4 6% 38%	4250
	11th to 20th	Night	15% 6% 2 5% 3 3 3 2 4 5% 51%	4816
	21st to end	Night	10% 4 1 4 2 3 3 2 4 7% 61%	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	31% 2 4 19% 26% 19%	4098
	11th to 20th	Day	29% 3 3 18% 24% 23%	4540
	21st to end	Day	40% 3 6% 13% 24% 13%	4994
February	1st to 10th	Day	36% 4 6% 13% 19% 22%	2000
	11th to 20th	Day	33% 5% 6% 19% 20% 16%	1959
	21st to end	Day	29% 5% 8% 16% 24% 19%	1650
March	1st to 10th	Day	30% 4 7% 16% 14% 29%	4539
	11th to 20th	Day	33% 3 4 8% 14% 38%	4980
	21st to end	Day	32% 4 8% 18% 19% 19%	5464
April	1st to 10th	Day	32% 4 8% 17% 19% 19%	2273
	11th to 20th	Day	32% 5% 9% 18% 17% 19%	2374
	21st to end	Day	35% 5% 8% 18% 17% 17%	2400
May	1st to 10th	Day	41% 5% 7% 18% 16% 12%	5668
	11th to 20th	Day	27% 6% 12% 20% 19% 15%	5866
	21st to end	Day	37% 6% 10% 25% 18% 4	6447
June	1st to 10th	Day	21% 6% 13% 31% 22% 6%	2600
	11th to 20th	Day	22% 6% 12% 27% 24% 8%	2600
	21st to end	Day	30% 7% 15% 25% 18% 6%	2600
July	1st to 10th	Day	38% 6% 15% 29% 11% 1	5836
	11th to 20th	Day	27% 6% 17% 34% 13% 2	5831
	21st to end	Day	26% 7% 14% 29% 22% 3	5758
August	1st to 10th	Day	9% 3 10% 41% 34% 3	3892
	11th to 20th	Day	14% 5% 21% 42% 16% 2	3882
	21st to end	Day	22% 8% 17% 27% 24% 3	4311
September	1st to 10th	Day	38% 8% 12% 20% 15% 7%	2236
	11th to 20th	Day	38% 7% 12% 21% 18% 4	2178
	21st to end	Day	28% 7% 11% 23% 18% 13%	2090
October	1st to 10th	Day	17% 4 6% 14% 20% 39%	3480
	11th to 20th	Day	34% 3 6% 12% 17% 27%	3458
	21st to end	Day	26% 3 5% 14% 38% 15%	3539
November	1st to 10th	Day	36% 4 8% 19% 21% 13%	1849
	11th to 20th	Day	33% 4 7% 18% 21% 17%	1800
	21st to end	Day	36% 4 7% 19% 18% 17%	1800
December	1st to 10th	Day	53% 3 5% 14% 16% 10%	2940
	11th to 20th	Day	39% 4 8% 17% 17% 16%	3389
	21st to end	Day	30% 2 3 16% 28% 21%	4488
January	1st to 10th	Night	28% 2 6% 17% 27% 19%	5888
	11th to 20th	Night	25% 2 4 16% 24% 27%	5462
	21st to end	Night	42% 3 5% 13% 22% 15%	5984
February	1st to 10th	Night	28% 4 8% 16% 18% 26%	2400
	11th to 20th	Night	32% 4 7% 19% 20% 18%	2338
	21st to end	Night	31% 5% 7% 15% 21% 21%	1980
March	1st to 10th	Night	28% 5% 8% 21% 16% 23%	5332
	11th to 20th	Night	30% 4 5% 10% 16% 34%	4980
	21st to end	Night	27% 4 9% 22% 19% 18%	5467
April	1st to 10th	Night	26% 6% 11% 19% 18% 20%	2120
	11th to 20th	Night	32% 6% 9% 17% 16% 20%	1977
	21st to end	Night	32% 5% 10% 21% 18% 15%	2000
May	1st to 10th	Night	39% 5% 9% 19% 17% 12%	4307
	11th to 20th	Night	26% 7% 11% 19% 20% 17%	4054
	21st to end	Night	30% 7% 14% 26% 16% 5%	4452
June	1st to 10th	Night	17% 7% 17% 32% 22% 5%	1800
	11th to 20th	Night	17% 5% 13% 29% 28% 9%	1800
	21st to end	Night	23% 8% 17% 27% 20% 6%	1800
July	1st to 10th	Night	32% 7% 21% 29% 10% 1	4035
	11th to 20th	Night	26% 7% 17% 32% 15% 3	4026
	21st to end	Night	22% 6% 17% 30% 22% 2	4796
August	1st to 10th	Night	10% 3 10% 41% 34% 3	3244
	11th to 20th	Night	16% 6% 22% 40% 14% 2	3243
	21st to end	Night	24% 7% 19% 27% 21% 3	3597
September	1st to 10th	Night	33% 8% 14% 20% 16% 8%	2161
	11th to 20th	Night	32% 7% 16% 22% 18% 5%	2178
	21st to end	Night	28% 5% 11% 23% 17% 15%	2090
October	1st to 10th	Night	17% 4 7% 16% 19% 37%	3480
	11th to 20th	Night	29% 3 6% 14% 18% 30%	3460
	21st to end	Night	17% 2 7% 15% 42% 17%	3962
November	1st to 10th	Night	30% 2 7% 19% 26% 16%	2445
	11th to 20th	Night	27% 3 9% 20% 22% 18%	2600
	21st to end	Night	33% 5% 8% 18% 19% 18%	2600
December	1st to 10th	Night	49% 3 9% 13% 12% 14%	4250
	11th to 20th	Night	36% 3 8% 18% 18% 17%	4817
	21st to end	Night	26% 4 6% 19% 24% 21%	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	18% 4 25% 35% 16% 2	300
	11th to 20th	Day	18% 9% 25% 32% 16% 1	300
	21st to end	Day	15% 10% 29% 32% 13% 2	330
February	1st to 10th	Day	20% 8% 22% 25% 19% 6%	300
	11th to 20th	Day	19% 8% 34% 24% 12% 3	300
	21st to end	Day	15% 9% 34% 30% 12%	249
March	1st to 10th	Day	19% 11% 34% 31% 6% 1	300
	11th to 20th	Day	16% 10% 34% 27% 13%	300
	21st to end	Day	13% 11% 31% 35% 9% 1	330
April	1st to 10th	Day	11% 11% 36% 34% 8%	373
	11th to 20th	Day	9% 13% 40% 32% 7%	492
	21st to end	Day	12% 8% 40% 32% 7% 1	500
May	1st to 10th	Day	14% 8% 34% 33% 9% 1	601
	11th to 20th	Day	12% 6% 32% 37% 11% 1	725
	21st to end	Day	15% 5% 24% 41% 13% 1	789
June	1st to 10th	Day	4 2 17% 50% 23% 4	730
	11th to 20th	Day	4 2 16% 50% 24% 4	730
	21st to end	Day	4 2 11% 40% 37% 6%	730
July	1st to 10th	Day	11% 1 6% 32% 42% 7%	721
	11th to 20th	Day	4 1 4 36% 47% 8%	718
	21st to end	Day	3 1 6% 35% 44% 10%	582
August	1st to 10th	Day	1 3 33% 48% 14%	527
	11th to 20th	Day	2 5% 30% 45% 17%	517
	21st to end	Day	4 1 4 31% 42% 18%	583
September	1st to 10th	Day	12% 1 2 24% 41% 20%	366
	11th to 20th	Day	6% 1 4 20% 40% 29%	324
	21st to end	Day	7% 1 5% 21% 44% 22%	300
October	1st to 10th	Day	9% 2 9% 27% 41% 13%	300
	11th to 20th	Day	13% 2 9% 38% 30% 8%	300
	21st to end	Day	17% 7% 19% 33% 19% 5%	330
November	1st to 10th	Day	20% 6% 20% 27% 22% 6%	300
	11th to 20th	Day	22% 7% 13% 25% 25% 9%	300
	21st to end	Day	18% 5% 27% 30% 16% 3	300
December	1st to 10th	Day	26% 6% 16% 26% 19% 7%	300
	11th to 20th	Day	16% 9% 25% 24% 23% 2	300
	21st to end	Day	16% 5% 26% 30% 21% 3	330
January	1st to 10th	Night	15% 4 20% 47% 14% 1	1000
	11th to 20th	Night	16% 4 21% 50% 10%	809
	21st to end	Night	18% 6% 24% 43% 9%	880
February	1st to 10th	Night	14% 6% 25% 43% 12%	800
	11th to 20th	Night	16% 7% 31% 40% 6%	784
	21st to end	Night	14% 6% 32% 44% 4	660
March	1st to 10th	Night	15% 8% 34% 36% 6%	784
	11th to 20th	Night	12% 11% 34% 39% 5%	600
	21st to end	Night	10% 7% 46% 31% 5%	660
April	1st to 10th	Night	9% 7% 43% 37% 3	600
	11th to 20th	Night	12% 8% 46% 31% 3	593
	21st to end	Night	13% 8% 46% 30% 3	600
May	1st to 10th	Night	9% 7% 45% 37% 3	600
	11th to 20th	Night	11% 6% 42% 36% 6%	591
	21st to end	Night	8% 6% 40% 38% 9%	650
June	1st to 10th	Night	3 2 29% 57% 10%	600
	11th to 20th	Night	3 1 31% 56% 9% 1	600
	21st to end	Night	4 1 19% 59% 16%	600
July	1st to 10th	Night	9% 2 12% 59% 18% 1	585
	11th to 20th	Night	3 1 11% 60% 24% 1	582
	21st to end	Night	4 1 11% 57% 26%	657
August	1st to 10th	Night	2 9% 61% 27% 2	597
	11th to 20th	Night	4 1 9% 52% 33% 1	594
	21st to end	Night	4 1 7% 53% 32% 3	660
September	1st to 10th	Night	9% 2 6% 43% 37% 4	600
	11th to 20th	Night	10% 2 5% 43% 37% 3	594
	21st to end	Night	10% 1 8% 41% 36% 4	570
October	1st to 10th	Night	7% 2 9% 47% 35% 2	570
	11th to 20th	Night	13% 2 17% 41% 26% 1	570
	21st to end	Night	9% 4 18% 44% 23% 2	741
November	1st to 10th	Night	15% 3 13% 40% 27% 1	885
	11th to 20th	Night	13% 3 17% 41% 24% 2	1000
	21st to end	Night	16% 5% 17% 44% 17% 1	1000
December	1st to 10th	Night	19% 3 16% 42% 20% 1	1000
	11th to 20th	Night	20% 5% 18% 41% 15%	1000
	21st to end	Night	14% 5% 21% 45% 14% 1	1100

Page generated at 2025-09-16 00:49:15. Version ac07

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