Lake Amistad
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Amistad 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	10% 5% 2 4 3 3 3 3 5% 7% 54%	137443
	Night	10% 4 1 4 3 3 3 3 5% 7% 57%	134918
Transparency	Day	21% 35% 6% 15% 14% 10%	141374
	Night	19% 35% 7% 14% 14% 11%	139038
Seeing	Day	12% 4 19% 35% 25% 6%	16781
	Night	11% 3 24% 45% 16% 1	26802

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	9% 6% 1 3 2 2 2 2 3 5% 64%	5331
	11th to 20th	Day	8% 5% 2 3 2 2 3 2 3 6% 63%	5910
	21st to end	Day	15% 7% 2 4 3 3 2 3 4 6% 51%	6468
February	1st to 10th	Day	12% 7% 2 5% 3 3 3 2 4 5% 54%	2100
	11th to 20th	Day	12% 5% 2 5% 3 3 3 3 5% 6% 53%	2049
	21st to end	Day	9% 5% 2 4 3 3 3 3 4 6% 58%	1730
March	1st to 10th	Day	11% 6% 2 4 3 3 3 2 4 5% 57%	4600
	11th to 20th	Day	15% 5% 1 3 2 2 3 2 3 5% 58%	5045
	21st to end	Day	12% 6% 2 4 3 3 3 3 6% 7% 51%	5583
April	1st to 10th	Day	11% 6% 2 5% 4 3 3 3 5% 7% 51%	2462
	11th to 20th	Day	14% 5% 2 4 2 3 3 3 5% 6% 53%	2494
	21st to end	Day	14% 5% 2 5% 3 3 3 3 4 6% 51%	2520
May	1st to 10th	Day	16% 6% 2 5% 3 3 4 4 6% 8% 42%	7260
	11th to 20th	Day	10% 4 2 5% 4 4 4 3 5% 9% 50%	7627
	21st to end	Day	11% 6% 3 6% 4 4 4 4 8% 10% 40%	8392
June	1st to 10th	Day	5% 3 1 4 3 4 4 4 7% 10% 55%	2730
	11th to 20th	Day	7% 4 2 3 3 4 5% 4 6% 8% 55%	2666
	21st to end	Day	6% 4 2 4 4 5% 4 5% 7% 9% 50%	2600
July	1st to 10th	Day	11% 5% 2 5% 4 4 4 4 6% 8% 48%	5900
	11th to 20th	Day	4 4 2 5% 3 4 4 4 6% 9% 55%	5868
	21st to end	Day	5% 4 2 4 3 4 3 3 5% 8% 59%	5920
August	1st to 10th	Day	1 1 2 2 2 2 3 4 7% 75%	3905
	11th to 20th	Day	2 1 1 2 2 2 3 4 5% 9% 69%	3846
	21st to end	Day	5% 3 1 4 4 4 4 4 6% 9% 57%	4312
September	1st to 10th	Day	11% 5% 2 6% 5% 5% 5% 4 5% 7% 45%	2275
	11th to 20th	Day	11% 5% 2 6% 4 5% 4 4 7% 8% 45%	2200
	21st to end	Day	7% 4 2 4 4 4 4 3 6% 8% 54%	2200
October	1st to 10th	Day	7% 4 1 4 3 3 4 3 5% 6% 58%	2200
	11th to 20th	Day	13% 4 2 5% 3 3 3 3 5% 5% 54%	2200
	21st to end	Day	13% 3 2 3 3 2 2 2 3 5% 63%	2298
November	1st to 10th	Day	15% 4 2 3 3 3 3 3 4 6% 56%	1874
	11th to 20th	Day	11% 6% 2 4 2 3 2 2 3 6% 59%	1890
	21st to end	Day	13% 6% 2 6% 3 2 3 3 4 5% 52%	1890
December	1st to 10th	Day	23% 9% 3 6% 5% 3 3 3 4 4 39%	3030
	11th to 20th	Day	14% 7% 2 5% 3 3 3 3 4 6% 49%	3481
	21st to end	Day	13% 6% 2 3 2 2 2 2 2 3 63%	4587
January	1st to 10th	Night	8% 4 1 3 2 2 2 2 4 6% 66%	7634
	11th to 20th	Night	9% 4 1 3 2 2 2 2 4 5% 67%	7080
	21st to end	Night	18% 7% 2 5% 3 3 3 2 4 6% 48%	7746
February	1st to 10th	Night	8% 5% 2 4 3 2 2 3 5% 6% 60%	2520
	11th to 20th	Night	12% 6% 1 4 3 2 3 2 3 6% 57%	2458
	21st to end	Night	9% 3 1 4 3 4 3 3 5% 6% 58%	2076
March	1st to 10th	Night	7% 4 2 4 3 3 3 3 6% 7% 59%	5494
	11th to 20th	Night	13% 4 2 4 2 2 3 2 4 4 60%	5121
	21st to end	Night	9% 5% 2 4 3 3 3 3 4 6% 60%	5588
April	1st to 10th	Night	8% 4 2 4 2 3 4 3 6% 7% 57%	2152
	11th to 20th	Night	12% 5% 1 4 3 4 3 3 5% 6% 54%	2077
	21st to end	Night	12% 6% 2 4 3 3 2 3 4 6% 55%	2100
May	1st to 10th	Night	16% 6% 2 5% 4 3 3 3 4 6% 46%	5605
	11th to 20th	Night	7% 3 1 5% 4 3 4 4 6% 8% 54%	5265
	21st to end	Night	11% 5% 2 5% 3 4 4 4 6% 11% 44%	5793
June	1st to 10th	Night	3 2 1 3 3 2 4 4 6% 13% 59%	1890
	11th to 20th	Night	3 2 1 3 3 4 4 4 6% 8% 63%	1845
	21st to end	Night	6% 3 1 3 3 4 4 4 6% 9% 57%	1800
July	1st to 10th	Night	9% 4 2 5% 4 4 5% 4 7% 11% 46%	4078
	11th to 20th	Night	3 3 2 4 3 3 3 4 6% 9% 58%	4077
	21st to end	Night	6% 4 2 4 2 3 3 4 6% 9% 59%	4951
August	1st to 10th	Night	1 1 1 2 2 2 2 2 4 7% 76%	3255
	11th to 20th	Night	2 2 1 3 2 4 3 3 6% 10% 64%	3213
	21st to end	Night	5% 3 2 4 4 4 4 3 6% 11% 54%	3597
September	1st to 10th	Night	7% 5% 2 5% 4 4 4 4 6% 8% 51%	2125
	11th to 20th	Night	9% 4 2 6% 4 4 3 4 7% 8% 50%	2200
	21st to end	Night	7% 4 2 5% 3 3 4 4 5% 8% 57%	2200
October	1st to 10th	Night	7% 4 1 4 3 2 4 3 5% 6% 62%	2200
	11th to 20th	Night	11% 4 1 4 3 3 3 3 5% 5% 59%	2200
	21st to end	Night	8% 3 1 3 2 2 2 2 3 3 71%	2520
November	1st to 10th	Night	12% 4 2 3 3 2 2 2 3 5% 63%	2639
	11th to 20th	Night	9% 4 2 3 3 2 2 3 5% 6% 62%	2730
	21st to end	Night	12% 4 2 4 3 3 3 3 5% 5% 56%	2730
December	1st to 10th	Night	25% 6% 2 4 2 3 3 3 4 6% 41%	4380
	11th to 20th	Night	12% 6% 2 5% 3 3 3 3 3 5% 55%	4946
	21st to end	Night	9% 4 1 3 2 2 3 2 4 7% 63%	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	20% 20% 4 20% 20% 16%	5332
	11th to 20th	Day	20% 20% 3 15% 22% 20%	5910
	21st to end	Day	30% 22% 4 12% 23% 10%	6468
February	1st to 10th	Day	16% 59% 3 5% 8% 9%	2100
	11th to 20th	Day	12% 58% 4 12% 8% 6%	2059
	21st to end	Day	16% 59% 3 6% 9% 7%	1730
March	1st to 10th	Day	23% 28% 4 12% 10% 23%	4600
	11th to 20th	Day	22% 28% 3 5% 12% 30%	5045
	21st to end	Day	24% 29% 5% 12% 14% 16%	5585
April	1st to 10th	Day	15% 59% 3 8% 6% 9%	2462
	11th to 20th	Day	18% 60% 4 6% 7% 6%	2494
	21st to end	Day	14% 59% 5% 9% 5% 7%	2520
May	1st to 10th	Day	31% 25% 6% 16% 13% 9%	7295
	11th to 20th	Day	25% 23% 8% 16% 16% 12%	7631
	21st to end	Day	30% 24% 10% 19% 12% 4	8405
June	1st to 10th	Day	10% 60% 7% 15% 8% 1	2730
	11th to 20th	Day	14% 61% 4 9% 9% 2	2666
	21st to end	Day	11% 61% 8% 12% 7% 1	2600
July	1st to 10th	Day	25% 27% 15% 23% 10%	5836
	11th to 20th	Day	21% 27% 16% 28% 9% 1	5799
	21st to end	Day	18% 26% 12% 21% 20% 3	5752
August	1st to 10th	Day	6% 36% 5% 24% 28% 3	3892
	11th to 20th	Day	7% 36% 14% 31% 11% 1	3882
	21st to end	Day	12% 37% 11% 20% 17% 2	4311
September	1st to 10th	Day	15% 58% 4 10% 8% 5%	2275
	11th to 20th	Day	15% 58% 7% 10% 8% 2	2200
	21st to end	Day	15% 58% 6% 12% 6% 3	2200
October	1st to 10th	Day	9% 36% 3 7% 13% 32%	3590
	11th to 20th	Day	21% 36% 3 8% 10% 21%	3568
	21st to end	Day	19% 35% 2 11% 27% 6%	3687
November	1st to 10th	Day	20% 54% 6% 6% 8% 6%	1874
	11th to 20th	Day	18% 54% 4 8% 9% 8%	1890
	21st to end	Day	18% 54% 3 10% 10% 5%	1890
December	1st to 10th	Day	38% 34% 3 10% 8% 7%	3030
	11th to 20th	Day	28% 31% 6% 12% 13% 10%	3479
	21st to end	Day	22% 25% 2 13% 18% 21%	4587
January	1st to 10th	Night	17% 21% 5% 18% 25% 14%	7635
	11th to 20th	Night	17% 20% 2 12% 24% 25%	7080
	21st to end	Night	32% 22% 4 11% 19% 12%	7746
February	1st to 10th	Night	11% 59% 3 8% 7% 12%	2520
	11th to 20th	Night	13% 57% 4 11% 11% 5%	2458
	21st to end	Night	14% 59% 2 7% 10% 7%	2076
March	1st to 10th	Night	19% 29% 6% 16% 13% 17%	5494
	11th to 20th	Night	21% 28% 3 7% 12% 29%	5121
	21st to end	Night	19% 29% 6% 16% 15% 14%	5588
April	1st to 10th	Night	12% 60% 6% 8% 6% 9%	2152
	11th to 20th	Night	17% 60% 5% 7% 6% 5%	2077
	21st to end	Night	14% 59% 6% 9% 8% 5%	2100
May	1st to 10th	Night	32% 24% 7% 16% 12% 9%	5632
	11th to 20th	Night	21% 23% 9% 17% 17% 13%	5266
	21st to end	Night	28% 24% 14% 19% 9% 5%	5805
June	1st to 10th	Night	7% 60% 8% 16% 9% 1	1890
	11th to 20th	Night	9% 61% 6% 11% 11% 2	1845
	21st to end	Night	8% 60% 7% 14% 8% 2	1800
July	1st to 10th	Night	22% 28% 15% 26% 9%	4035
	11th to 20th	Night	18% 27% 16% 27% 10% 2	4026
	21st to end	Night	17% 26% 12% 23% 19% 2	4808
August	1st to 10th	Night	6% 35% 6% 25% 26% 2	3244
	11th to 20th	Night	11% 37% 13% 30% 8% 1	3243
	21st to end	Night	14% 37% 11% 18% 18% 2	3597
September	1st to 10th	Night	13% 58% 5% 10% 9% 5%	2125
	11th to 20th	Night	12% 58% 8% 12% 8% 3	2200
	21st to end	Night	14% 58% 7% 12% 6% 3	2200
October	1st to 10th	Night	12% 36% 3 7% 11% 31%	3590
	11th to 20th	Night	18% 35% 3 7% 13% 24%	3570
	21st to end	Night	12% 35% 3 10% 32% 7%	4056
November	1st to 10th	Night	19% 53% 5% 6% 9% 8%	2639
	11th to 20th	Night	16% 54% 5% 10% 8% 8%	2730
	21st to end	Night	17% 54% 4 8% 11% 7%	2730
December	1st to 10th	Night	36% 34% 5% 9% 6% 10%	4380
	11th to 20th	Night	23% 31% 5% 13% 17% 11%	4947
	21st to end	Night	19% 26% 4 17% 19% 15%	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	15% 8% 24% 37% 15% 1	330
	11th to 20th	Day	15% 8% 24% 37% 14% 2	330
	21st to end	Day	15% 5% 33% 31% 15% 1	363
February	1st to 10th	Day	18% 7% 23% 28% 18% 6%	330
	11th to 20th	Day	17% 8% 31% 31% 12% 2	330
	21st to end	Day	13% 7% 31% 37% 11% 1	273
March	1st to 10th	Day	18% 8% 35% 29% 10%	330
	11th to 20th	Day	17% 5% 35% 29% 12% 2	330
	21st to end	Day	13% 9% 34% 31% 10% 3	363
April	1st to 10th	Day	13% 10% 33% 33% 11% 1	482
	11th to 20th	Day	13% 9% 36% 34% 8%	532
	21st to end	Day	13% 7% 39% 31% 9% 1	540
May	1st to 10th	Day	13% 5% 30% 38% 12% 1	627
	11th to 20th	Day	18% 3 28% 38% 10% 2	775
	21st to end	Day	16% 3 25% 42% 13% 2	844
June	1st to 10th	Day	8% 2 15% 49% 24% 3	780
	11th to 20th	Day	8% 1 16% 47% 24% 4	756
	21st to end	Day	5% 1 11% 40% 35% 8%	730
July	1st to 10th	Day	12% 1 5% 33% 39% 10%	721
	11th to 20th	Day	5% 1 4 38% 45% 7%	712
	21st to end	Day	2 1 5% 35% 45% 13%	575
August	1st to 10th	Day	1 1 2 36% 48% 12%	527
	11th to 20th	Day	3 3 30% 50% 13%	517
	21st to end	Day	3 2 3 29% 43% 20%	583
September	1st to 10th	Day	12% 1 3 25% 40% 19%	405
	11th to 20th	Day	6% 1 2 27% 44% 20%	330
	21st to end	Day	8% 1 2 29% 42% 18%	330
October	1st to 10th	Day	7% 1 11% 32% 39% 10%	330
	11th to 20th	Day	16% 1 10% 33% 34% 5%	330
	21st to end	Day	18% 4 21% 31% 21% 4	363
November	1st to 10th	Day	20% 3 17% 30% 22% 8%	330
	11th to 20th	Day	18% 5% 17% 26% 25% 10%	330
	21st to end	Day	18% 5% 31% 28% 14% 3	330
December	1st to 10th	Day	20% 5% 19% 29% 20% 5%	330
	11th to 20th	Day	16% 5% 30% 26% 18% 5%	330
	21st to end	Day	20% 4 20% 34% 20% 3	363
January	1st to 10th	Night	13% 3 24% 49% 10% 1	1050
	11th to 20th	Night	14% 5% 24% 49% 8%	840
	21st to end	Night	16% 5% 27% 44% 7%	924
February	1st to 10th	Night	13% 6% 28% 43% 10%	840
	11th to 20th	Night	15% 5% 36% 37% 7%	824
	21st to end	Night	11% 4 39% 44% 2	692
March	1st to 10th	Night	17% 7% 35% 36% 4	840
	11th to 20th	Night	13% 7% 36% 40% 5%	648
	21st to end	Night	11% 7% 43% 35% 4	693
April	1st to 10th	Night	9% 6% 44% 39% 3	630
	11th to 20th	Night	13% 7% 48% 30% 2	623
	21st to end	Night	13% 6% 46% 30% 4	630
May	1st to 10th	Night	12% 5% 41% 37% 4	630
	11th to 20th	Night	10% 3 38% 42% 7%	621
	21st to end	Night	11% 2 36% 43% 7%	683
June	1st to 10th	Night	5% 1 26% 57% 11%	630
	11th to 20th	Night	3 1 30% 54% 11%	615
	21st to end	Night	6% 2 20% 52% 20% 1	600
July	1st to 10th	Night	10% 1 11% 53% 24% 2	585
	11th to 20th	Night	3 10% 59% 26% 1	582
	21st to end	Night	4 1 8% 59% 27% 1	657
August	1st to 10th	Night	2 1 5% 54% 36% 3	597
	11th to 20th	Night	5% 5% 52% 35% 3	594
	21st to end	Night	5% 5% 50% 37% 3	660
September	1st to 10th	Night	7% 1 4 46% 38% 5%	600
	11th to 20th	Night	10% 1 6% 44% 37% 2	600
	21st to end	Night	9% 1 7% 47% 34% 2	600
October	1st to 10th	Night	8% 2 12% 49% 29% 1	600
	11th to 20th	Night	12% 1 17% 49% 21% 1	600
	21st to end	Night	9% 4 21% 44% 20% 2	760
November	1st to 10th	Night	15% 3 17% 41% 24% 1	999
	11th to 20th	Night	11% 3 20% 47% 18% 2	1050
	21st to end	Night	14% 4 23% 43% 15% 1	1050
December	1st to 10th	Night	16% 2 19% 46% 16% 1	1050
	11th to 20th	Night	17% 4 21% 43% 14%	1050
	21st to end	Night	14% 4 23% 45% 13%	1155

Page generated at 2026-06-13 01:31:39. Version ac07

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