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 2025-02-21.

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 4 3 3 3 3 5% 7% 55%	109111
	Night	10% 4 1 4 3 3 3 3 5% 7% 58%	109683
Transparency	Day	17% 43% 5% 13% 13% 8%	113078
	Night	17% 42% 5% 13% 13% 9%	113830
Seeing	Day	12% 3 18% 35% 26% 6%	14999
	Night	11% 3 23% 45% 16% 1	25137

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	12% 7% 2 3 2 2 2 2 3 5% 62%	4105
	11th to 20th	Day	8% 5% 1 3 2 2 2 2 4 8% 62%	4540
	21st to end	Day	16% 6% 2 5% 3 2 3 2 4 6% 51%	4994
February	1st to 10th	Day	12% 7% 2 5% 3 3 3 2 4 5% 54%	2000
	11th to 20th	Day	13% 6% 2 5% 3 3 3 3 5% 6% 54%	1949
	21st to end	Day	9% 4 2 4 3 3 3 3 5% 6% 57%	1570
March	1st to 10th	Day	13% 7% 2 4 3 3 3 3 4 5% 51%	3130
	11th to 20th	Day	22% 8% 2 5% 3 3 3 3 4 5% 42%	3449
	21st to end	Day	10% 5% 1 4 3 3 4 4 7% 7% 51%	3814
April	1st to 10th	Day	11% 6% 2 4 4 3 3 3 5% 8% 52%	2228
	11th to 20th	Day	13% 5% 2 4 2 3 3 3 5% 6% 54%	2254
	21st to end	Day	14% 5% 2 5% 3 3 3 2 4 6% 53%	2280
May	1st to 10th	Day	17% 6% 2 4 3 3 4 3 6% 7% 46%	3893
	11th to 20th	Day	14% 5% 2 5% 3 3 4 3 4 7% 50%	4082
	21st to end	Day	10% 5% 2 5% 3 4 4 3 7% 10% 46%	4477
June	1st to 10th	Day	5% 3 1 3 3 4 4 4 7% 10% 57%	2470
	11th to 20th	Day	7% 3 2 3 3 3 5% 4 6% 9% 55%	2470
	21st to end	Day	6% 4 2 5% 4 5% 4 5% 7% 9% 50%	2470
July	1st to 10th	Day	7% 4 2 4 4 3 4 3 5% 7% 59%	4120
	11th to 20th	Day	4 4 2 4 3 3 4 4 6% 9% 58%	4102
	21st to end	Day	6% 4 2 4 4 3 3 3 5% 9% 58%	4117
August	1st to 10th	Day	1 1 2 2 2 2 3 4 7% 75%	3785
	11th to 20th	Day	2 1 1 2 2 2 3 4 5% 9% 69%	3726
	21st to end	Day	5% 3 1 4 4 4 4 4 6% 10% 57%	4180
September	1st to 10th	Day	11% 5% 2 6% 4 5% 5% 4 6% 6% 46%	2161
	11th to 20th	Day	11% 5% 2 6% 4 5% 4 4 7% 8% 45%	2090
	21st to end	Day	7% 4 2 4 4 4 4 3 6% 8% 54%	2090
October	1st to 10th	Day	8% 4 1 4 3 3 4 3 5% 6% 58%	2090
	11th to 20th	Day	14% 5% 2 5% 3 3 3 4 5% 5% 52%	2090
	21st to end	Day	13% 3 2 3 3 2 2 2 3 5% 62%	2183
November	1st to 10th	Day	15% 5% 2 3 3 3 3 3 4 6% 54%	1783
	11th to 20th	Day	11% 6% 2 4 2 3 2 2 3 6% 59%	1800
	21st to end	Day	12% 6% 2 6% 3 2 3 3 4 5% 53%	1800
December	1st to 10th	Day	23% 9% 3 6% 5% 3 3 3 4 4 38%	2940
	11th to 20th	Day	14% 7% 2 5% 3 3 3 3 4 6% 49%	3391
	21st to end	Day	13% 6% 2 3 2 2 2 2 2 4 64%	4488
January	1st to 10th	Night	10% 5% 2 4 2 2 2 2 4 7% 62%	5888
	11th to 20th	Night	8% 4 1 2 2 2 2 2 4 6% 67%	5440
	21st to end	Night	19% 6% 2 5% 3 3 3 2 4 6% 48%	5984
February	1st to 10th	Night	9% 5% 2 4 3 2 2 3 5% 6% 60%	2400
	11th to 20th	Night	13% 7% 2 4 3 2 3 2 3 5% 57%	2338
	21st to end	Night	9% 3 1 4 3 4 3 3 5% 7% 56%	1884
March	1st to 10th	Night	8% 4 2 4 3 3 4 3 6% 8% 56%	3734
	11th to 20th	Night	19% 6% 2 5% 3 3 4 3 5% 5% 44%	3496
	21st to end	Night	9% 5% 2 4 3 3 3 4 4 6% 58%	3817
April	1st to 10th	Night	8% 4 1 4 3 3 4 3 6% 7% 57%	1948
	11th to 20th	Night	12% 5% 1 4 3 4 3 3 5% 5% 54%	1877
	21st to end	Night	11% 6% 2 4 3 3 2 3 4 5% 57%	1900
May	1st to 10th	Night	15% 6% 2 4 4 3 3 3 4 5% 52%	2994
	11th to 20th	Night	10% 5% 2 4 4 3 4 3 5% 6% 55%	2823
	21st to end	Night	7% 4 2 5% 3 3 4 4 5% 9% 54%	3090
June	1st to 10th	Night	3 2 1 3 2 2 3 4 5% 13% 61%	1710
	11th to 20th	Night	3 2 1 3 3 3 4 4 6% 8% 63%	1710
	21st to end	Night	6% 3 1 3 3 4 4 4 6% 9% 57%	1710
July	1st to 10th	Night	5% 3 1 4 3 3 3 4 6% 9% 58%	2850
	11th to 20th	Night	3 3 1 4 3 3 4 4 6% 9% 59%	2850
	21st to end	Night	7% 4 1 3 2 2 3 4 6% 9% 58%	3446
August	1st to 10th	Night	1 1 1 2 2 2 2 2 4 7% 76%	3155
	11th to 20th	Night	3 2 3 2 4 3 3 6% 9% 64%	3113
	21st to end	Night	5% 3 1 4 4 4 4 3 6% 11% 54%	3487
September	1st to 10th	Night	7% 5% 2 5% 4 4 4 4 6% 8% 52%	2019
	11th to 20th	Night	9% 4 2 6% 4 4 3 4 6% 7% 50%	2090
	21st to end	Night	7% 4 1 4 3 3 4 4 4 8% 58%	2090
October	1st to 10th	Night	7% 4 1 4 3 2 4 3 4 6% 62%	2090
	11th to 20th	Night	11% 4 1 4 3 3 3 3 5% 5% 58%	2090
	21st to end	Night	8% 3 1 3 2 2 2 2 3 3 71%	2394
November	1st to 10th	Night	13% 5% 2 3 3 2 2 2 3 5% 61%	2510
	11th to 20th	Night	9% 4 2 3 3 2 2 3 5% 6% 61%	2600
	21st to end	Night	11% 4 1 4 3 3 3 3 5% 5% 57%	2600
December	1st to 10th	Night	26% 6% 2 4 2 3 3 3 4 6% 41%	4250
	11th to 20th	Night	12% 6% 2 5% 3 3 3 3 4 5% 55%	4816
	21st to end	Night	9% 4 1 3 2 2 3 2 4 7% 63%	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	22% 25% 2 17% 18% 16%	4106
	11th to 20th	Day	17% 26% 3 17% 19% 18%	4540
	21st to end	Day	28% 28% 3 11% 20% 10%	4994
February	1st to 10th	Day	16% 62% 3 5% 7% 9%	2000
	11th to 20th	Day	11% 61% 3 12% 8% 5%	1959
	21st to end	Day	14% 65% 3 6% 7% 5%	1570
March	1st to 10th	Day	26% 40% 4 9% 11% 10%	3130
	11th to 20th	Day	31% 41% 5% 6% 11% 6%	3449
	21st to end	Day	18% 42% 7% 8% 10% 15%	3814
April	1st to 10th	Day	12% 65% 3 7% 6% 8%	2228
	11th to 20th	Day	14% 66% 3 6% 7% 5%	2254
	21st to end	Day	10% 64% 3 9% 6% 7%	2280
May	1st to 10th	Day	23% 42% 4 10% 10% 12%	3928
	11th to 20th	Day	21% 40% 5% 13% 11% 10%	4086
	21st to end	Day	18% 41% 8% 16% 10% 6%	4489
June	1st to 10th	Day	7% 66% 6% 12% 8% 1	2470
	11th to 20th	Day	12% 66% 4 8% 8% 2	2470
	21st to end	Day	10% 64% 6% 10% 7% 1	2470
July	1st to 10th	Day	11% 36% 13% 27% 13%	4056
	11th to 20th	Day	15% 36% 14% 24% 10% 1	4033
	21st to end	Day	15% 36% 7% 19% 20% 3	3988
August	1st to 10th	Day	6% 37% 5% 23% 27% 3	3772
	11th to 20th	Day	7% 37% 14% 30% 11% 1	3762
	21st to end	Day	12% 38% 11% 20% 16% 2	4179
September	1st to 10th	Day	13% 61% 4 9% 7% 5%	2161
	11th to 20th	Day	14% 61% 6% 9% 8% 2	2090
	21st to end	Day	14% 61% 6% 11% 5% 3	2090
October	1st to 10th	Day	9% 37% 3 6% 12% 32%	3480
	11th to 20th	Day	22% 37% 2 7% 10% 22%	3458
	21st to end	Day	19% 37% 2 11% 27% 5%	3572
November	1st to 10th	Day	20% 57% 6% 7% 5% 5%	1783
	11th to 20th	Day	17% 57% 4 7% 8% 7%	1800
	21st to end	Day	16% 56% 3 10% 9% 5%	1800
December	1st to 10th	Day	38% 35% 3 10% 8% 6%	2940
	11th to 20th	Day	27% 32% 6% 12% 13% 9%	3389
	21st to end	Day	21% 26% 2 13% 17% 21%	4488
January	1st to 10th	Night	18% 27% 4 16% 22% 13%	5888
	11th to 20th	Night	14% 26% 3 14% 20% 24%	5440
	21st to end	Night	30% 28% 3 9% 18% 11%	5984
February	1st to 10th	Night	11% 61% 3 6% 7% 11%	2400
	11th to 20th	Night	12% 60% 3 9% 11% 4	2338
	21st to end	Night	14% 65% 2 6% 8% 5%	1884
March	1st to 10th	Night	19% 42% 6% 12% 13% 8%	3734
	11th to 20th	Night	30% 40% 5% 9% 9% 6%	3496
	21st to end	Night	16% 42% 7% 12% 10% 13%	3817
April	1st to 10th	Night	10% 65% 4 7% 7% 7%	1948
	11th to 20th	Night	14% 66% 4 5% 6% 5%	1877
	21st to end	Night	10% 64% 4 8% 8% 5%	1900
May	1st to 10th	Night	21% 43% 5% 10% 11% 10%	3024
	11th to 20th	Night	17% 40% 5% 14% 14% 10%	2824
	21st to end	Night	16% 42% 7% 17% 8% 9%	3099
June	1st to 10th	Night	4 66% 6% 14% 9% 1	1710
	11th to 20th	Night	7% 66% 5% 10% 10% 2	1710
	21st to end	Night	7% 64% 6% 13% 8% 2	1710
July	1st to 10th	Night	9% 36% 12% 30% 12% 1	2805
	11th to 20th	Night	15% 37% 13% 21% 11% 3	2796
	21st to end	Night	15% 36% 8% 22% 17% 1	3336
August	1st to 10th	Night	6% 36% 6% 25% 25% 2	3144
	11th to 20th	Night	10% 38% 12% 30% 8% 2	3143
	21st to end	Night	14% 38% 11% 18% 17% 2	3487
September	1st to 10th	Night	11% 61% 5% 10% 8% 5%	2019
	11th to 20th	Night	12% 60% 7% 10% 8% 2	2090
	21st to end	Night	13% 61% 6% 10% 6% 3	2090
October	1st to 10th	Night	12% 37% 3 7% 10% 31%	3480
	11th to 20th	Night	19% 36% 3 5% 13% 24%	3460
	21st to end	Night	13% 36% 3 10% 32% 6%	3930
November	1st to 10th	Night	20% 56% 6% 6% 7% 6%	2510
	11th to 20th	Night	16% 57% 5% 9% 7% 7%	2600
	21st to end	Night	15% 56% 4 8% 10% 7%	2600
December	1st to 10th	Night	36% 35% 5% 9% 5% 9%	4250
	11th to 20th	Night	23% 32% 5% 13% 16% 10%	4817
	21st to end	Night	19% 26% 4 17% 19% 16%	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	16% 7% 24% 38% 15% 1	300
	11th to 20th	Day	16% 8% 23% 37% 14% 2	300
	21st to end	Day	14% 5% 33% 32% 16% 1	330
February	1st to 10th	Day	19% 7% 23% 28% 17% 6%	300
	11th to 20th	Day	17% 8% 30% 30% 13% 1	300
	21st to end	Day	15% 8% 32% 38% 8%	225
March	1st to 10th	Day	17% 6% 36% 31% 10%	270
	11th to 20th	Day	20% 4 33% 30% 12% 1	270
	21st to end	Day	13% 10% 36% 31% 9% 1	297
April	1st to 10th	Day	13% 9% 34% 34% 11%	408
	11th to 20th	Day	11% 9% 36% 35% 9%	452
	21st to end	Day	12% 6% 39% 32% 9% 1	460
May	1st to 10th	Day	13% 4 29% 40% 13% 1	539
	11th to 20th	Day	19% 2 25% 39% 12% 2	675
	21st to end	Day	17% 2 23% 43% 13% 2	734
June	1st to 10th	Day	7% 1 13% 49% 26% 3	680
	11th to 20th	Day	8% 1 15% 47% 26% 4	680
	21st to end	Day	5% 1 9% 41% 36% 9%	680
July	1st to 10th	Day	11% 1 5% 33% 40% 11%	671
	11th to 20th	Day	5% 1 4 37% 46% 8%	663
	21st to end	Day	2 1 4 34% 46% 14%	531
August	1st to 10th	Day	1 1 2 34% 49% 13%	487
	11th to 20th	Day	4 3 30% 51% 13%	477
	21st to end	Day	3 2 3 29% 42% 21%	539
September	1st to 10th	Day	11% 1 3 25% 40% 19%	371
	11th to 20th	Day	7% 1 2 23% 44% 22%	300
	21st to end	Day	9% 1 3 28% 41% 19%	300
October	1st to 10th	Day	8% 1 11% 32% 37% 11%	300
	11th to 20th	Day	18% 1 10% 32% 33% 6%	300
	21st to end	Day	20% 4 20% 31% 21% 4	330
November	1st to 10th	Day	22% 2 18% 31% 21% 6%	300
	11th to 20th	Day	18% 5% 17% 27% 23% 9%	300
	21st to end	Day	17% 5% 33% 28% 14% 3	300
December	1st to 10th	Day	21% 5% 17% 29% 21% 6%	300
	11th to 20th	Day	16% 5% 31% 27% 17% 4	300
	21st to end	Day	19% 5% 22% 34% 19% 2	330
January	1st to 10th	Night	14% 3 24% 49% 10% 1	1000
	11th to 20th	Night	14% 5% 24% 49% 8%	800
	21st to end	Night	16% 5% 28% 44% 7%	880
February	1st to 10th	Night	13% 6% 28% 43% 10%	800
	11th to 20th	Night	16% 5% 36% 37% 6%	784
	21st to end	Night	11% 5% 40% 43% 2	628
March	1st to 10th	Night	17% 6% 34% 38% 5%	760
	11th to 20th	Night	14% 6% 35% 40% 5%	586
	21st to end	Night	11% 7% 43% 34% 5%	627
April	1st to 10th	Night	8% 4 44% 40% 3	570
	11th to 20th	Night	12% 6% 47% 32% 2	563
	21st to end	Night	13% 5% 47% 31% 5%	570
May	1st to 10th	Night	12% 5% 41% 38% 4	570
	11th to 20th	Night	11% 2 36% 43% 8%	561
	21st to end	Night	11% 2 35% 45% 8%	617
June	1st to 10th	Night	5% 1 24% 59% 12%	570
	11th to 20th	Night	3 1 28% 55% 12%	570
	21st to end	Night	6% 1 19% 52% 21% 1	570
July	1st to 10th	Night	9% 1 11% 53% 25% 2	555
	11th to 20th	Night	3 10% 58% 28% 1	552
	21st to end	Night	4 1 8% 59% 27%	624
August	1st to 10th	Night	2 1 4 54% 37% 3	567
	11th to 20th	Night	5% 4 51% 37% 2	564
	21st to end	Night	5% 5% 50% 37% 3	627
September	1st to 10th	Night	7% 1 4 46% 38% 5%	570
	11th to 20th	Night	11% 6% 43% 38% 2	570
	21st to end	Night	9% 1 7% 46% 35% 2	570
October	1st to 10th	Night	8% 2 12% 48% 29% 1	570
	11th to 20th	Night	13% 1 17% 47% 21% 1	570
	21st to end	Night	9% 4 20% 44% 21% 2	722
November	1st to 10th	Night	16% 3 17% 40% 23% 1	950
	11th to 20th	Night	11% 3 20% 46% 18% 2	1000
	21st to end	Night	14% 3 23% 44% 15% 1	1000
December	1st to 10th	Night	17% 2 18% 46% 16% 1	1000
	11th to 20th	Night	18% 4 21% 43% 14%	1000
	21st to end	Night	14% 4 24% 45% 12%	1100

Page generated at 2025-02-18 02:26:26. Version ac07

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