Laredo
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Laredo clear sky chart from 2005-11-06 to 2026-05-02.

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 5% 4 4 4 3 5% 7% 52%	132083
	Night	11% 5% 2 4 3 3 3 3 5% 7% 54%	130769
Transparency	Day	21% 37% 7% 16% 12% 7%	135973
	Night	21% 36% 8% 15% 12% 8%	134941
Seeing	Day	9% 4 18% 35% 26% 8%	16316
	Night	12% 4 27% 44% 13% 1	26440

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	15% 7% 2 6% 4 3 3 2 3 5% 50%	5289
	11th to 20th	Day	16% 4 1 4 3 3 3 2 4 6% 53%	5828
	21st to end	Day	20% 6% 2 5% 3 3 3 3 5% 6% 45%	6468
February	1st to 10th	Day	12% 8% 3 6% 5% 3 3 3 3 5% 49%	2100
	11th to 20th	Day	14% 6% 3 5% 3 3 3 3 4 5% 50%	2049
	21st to end	Day	12% 6% 2 3 3 3 3 3 5% 6% 54%	1730
March	1st to 10th	Day	10% 5% 2 5% 3 3 4 3 6% 7% 52%	4821
	11th to 20th	Day	16% 5% 2 3 3 2 2 2 4 4 56%	5090
	21st to end	Day	11% 5% 2 4 2 2 3 3 4 6% 58%	5583
April	1st to 10th	Day	12% 5% 2 5% 4 4 4 3 5% 6% 51%	2310
	11th to 20th	Day	11% 7% 2 6% 4 3 4 4 5% 8% 47%	2384
	21st to end	Day	10% 7% 2 5% 4 4 4 4 6% 8% 47%	2520
May	1st to 10th	Day	17% 6% 2 6% 4 4 3 3 5% 8% 42%	5775
	11th to 20th	Day	7% 5% 2 5% 3 3 3 3 5% 8% 57%	5862
	21st to end	Day	7% 4 2 5% 5% 4 5% 4 7% 10% 47%	6434
June	1st to 10th	Day	2 3 1 4 3 4 4 4 7% 10% 58%	2600
	11th to 20th	Day	3 3 1 4 3 4 4 3 5% 9% 62%	2600
	21st to end	Day	5% 4 1 5% 5% 5% 5% 5% 6% 10% 49%	2600
July	1st to 10th	Day	8% 5% 2 7% 6% 5% 5% 4 6% 9% 43%	5900
	11th to 20th	Day	5% 5% 2 6% 4 5% 5% 4 6% 10% 49%	5900
	21st to end	Day	3 3 1 5% 3 4 5% 4 7% 10% 54%	6063
August	1st to 10th	Day	1 1 2 2 2 2 2 3 6% 80%	3905
	11th to 20th	Day	2 1 1 3 2 3 4 4 7% 10% 63%	3846
	21st to end	Day	4 2 1 4 3 4 4 4 6% 10% 58%	4223
September	1st to 10th	Day	10% 7% 2 8% 5% 5% 6% 4 5% 8% 42%	2200
	11th to 20th	Day	10% 5% 2 6% 5% 6% 5% 5% 7% 9% 41%	2200
	21st to end	Day	7% 5% 1 5% 5% 5% 4 4 7% 8% 50%	2200
October	1st to 10th	Day	6% 4 2 5% 4 4 4 4 5% 5% 59%	2200
	11th to 20th	Day	11% 5% 2 5% 3 4 4 3 4 7% 53%	2200
	21st to end	Day	9% 4 2 4 3 3 3 2 4 5% 62%	2220
November	1st to 10th	Day	11% 6% 2 6% 4 3 3 3 4 5% 51%	2058
	11th to 20th	Day	13% 6% 2 6% 3 3 2 3 4 4 54%	1937
	21st to end	Day	16% 8% 2 5% 3 4 3 3 4 5% 47%	1890
December	1st to 10th	Day	32% 7% 2 4 3 3 3 3 4 5% 34%	3030
	11th to 20th	Day	14% 8% 2 6% 4 4 4 4 4 6% 45%	3481
	21st to end	Day	10% 6% 2 5% 3 3 4 3 4 6% 55%	4587
January	1st to 10th	Night	16% 6% 2 4 2 2 2 2 3 5% 55%	7634
	11th to 20th	Night	14% 4 2 4 3 3 3 2 4 7% 55%	7218
	21st to end	Night	22% 5% 2 5% 3 3 3 3 4 5% 45%	7746
February	1st to 10th	Night	10% 7% 2 4 3 3 4 3 5% 6% 55%	2520
	11th to 20th	Night	16% 6% 1 5% 2 3 3 2 4 6% 52%	2458
	21st to end	Night	12% 5% 2 4 2 3 3 3 4 6% 56%	2076
March	1st to 10th	Night	11% 5% 1 4 3 3 4 3 5% 6% 54%	5260
	11th to 20th	Night	15% 6% 2 4 3 3 3 2 3 5% 55%	5090
	21st to end	Night	12% 4 1 3 2 2 2 3 5% 5% 60%	5588
April	1st to 10th	Night	11% 4 2 4 3 4 4 3 6% 8% 52%	2310
	11th to 20th	Night	12% 5% 2 4 3 3 4 3 5% 8% 51%	2180
	21st to end	Night	12% 6% 2 5% 4 3 3 3 5% 8% 47%	2100
May	1st to 10th	Night	16% 6% 2 5% 3 3 4 3 5% 7% 46%	4159
	11th to 20th	Night	6% 4 1 4 3 3 3 3 6% 8% 59%	4053
	21st to end	Night	8% 5% 2 6% 4 4 4 3 7% 10% 46%	4443
June	1st to 10th	Night	2 2 1 3 3 2 3 3 6% 10% 65%	1800
	11th to 20th	Night	2 2 1 3 2 3 4 3 5% 9% 66%	1800
	21st to end	Night	3 3 1 4 4 4 5% 4 7% 11% 53%	1800
July	1st to 10th	Night	7% 5% 2 6% 5% 5% 5% 4 7% 9% 45%	4078
	11th to 20th	Night	5% 3 2 5% 4 3 4 3 7% 10% 53%	4077
	21st to end	Night	5% 3 1 5% 3 3 4 4 6% 8% 57%	4802
August	1st to 10th	Night	1 1 1 1 1 1 1 3 5% 84%	3255
	11th to 20th	Night	1 2 1 3 3 4 5% 4 7% 11% 59%	3213
	21st to end	Night	3 2 1 4 3 3 3 3 5% 11% 62%	3683
September	1st to 10th	Night	8% 7% 2 6% 4 5% 5% 4 7% 9% 43%	2200
	11th to 20th	Night	8% 5% 2 5% 4 4 5% 4 8% 9% 46%	2200
	21st to end	Night	7% 3 1 5% 3 3 3 4 6% 9% 56%	2200
October	1st to 10th	Night	5% 3 1 4 3 3 3 4 4 6% 63%	2200
	11th to 20th	Night	11% 4 2 4 3 3 3 2 4 6% 58%	2200
	21st to end	Night	9% 4 1 3 2 2 3 2 3 4 68%	2599
November	1st to 10th	Night	11% 4 1 4 2 3 2 3 4 6% 59%	2460
	11th to 20th	Night	12% 5% 2 4 3 3 3 3 4 5% 56%	2678
	21st to end	Night	16% 6% 2 4 4 3 3 3 4 5% 51%	2730
December	1st to 10th	Night	34% 7% 2 4 3 2 3 2 4 4 34%	4380
	11th to 20th	Night	16% 6% 2 5% 3 3 3 3 4 6% 51%	4946
	21st to end	Night	9% 5% 2 4 3 3 3 3 4 6% 57%	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	33% 21% 6% 15% 18% 8%	5290
	11th to 20th	Day	28% 20% 3 14% 24% 12%	5828
	21st to end	Day	33% 23% 6% 15% 18% 5%	6468
February	1st to 10th	Day	18% 59% 4 5% 7% 8%	2100
	11th to 20th	Day	16% 58% 4 8% 9% 5%	2059
	21st to end	Day	16% 59% 3 7% 8% 5%	1730
March	1st to 10th	Day	25% 29% 8% 14% 8% 17%	4821
	11th to 20th	Day	25% 28% 3 5% 13% 26%	5090
	21st to end	Day	21% 28% 5% 20% 16% 10%	5585
April	1st to 10th	Day	14% 60% 4 7% 7% 9%	2310
	11th to 20th	Day	18% 60% 4 7% 7% 5%	2384
	21st to end	Day	15% 60% 5% 8% 7% 5%	2520
May	1st to 10th	Day	32% 30% 7% 15% 11% 4	5812
	11th to 20th	Day	17% 30% 11% 16% 15% 11%	5866
	21st to end	Day	23% 30% 7% 31% 8% 1	6447
June	1st to 10th	Day	7% 63% 6% 15% 9% 1	2600
	11th to 20th	Day	12% 62% 3 9% 11% 2	2600
	21st to end	Day	13% 62% 8% 9% 7% 1	2600
July	1st to 10th	Day	27% 28% 14% 27% 4	5836
	11th to 20th	Day	24% 29% 17% 24% 5% 1	5831
	21st to end	Day	19% 28% 15% 24% 13% 1	5891
August	1st to 10th	Day	4 36% 7% 32% 21% 1	3892
	11th to 20th	Day	10% 38% 16% 30% 6% 1	3882
	21st to end	Day	10% 38% 15% 23% 14% 1	4222
September	1st to 10th	Day	17% 58% 7% 8% 8% 3	2200
	11th to 20th	Day	15% 59% 6% 11% 7% 2	2200
	21st to end	Day	14% 59% 7% 13% 5% 3	2200
October	1st to 10th	Day	10% 36% 3 6% 15% 29%	3590
	11th to 20th	Day	17% 37% 5% 11% 10% 20%	3568
	21st to end	Day	15% 36% 4 11% 26% 8%	3570
November	1st to 10th	Day	21% 54% 5% 7% 6% 7%	2058
	11th to 20th	Day	20% 54% 3 10% 6% 6%	1937
	21st to end	Day	22% 54% 3 9% 7% 4	1890
December	1st to 10th	Day	42% 35% 4 7% 8% 4	3030
	11th to 20th	Day	26% 32% 8% 15% 7% 11%	3479
	21st to end	Day	24% 27% 4 16% 19% 11%	4587
January	1st to 10th	Night	28% 21% 6% 16% 18% 11%	7635
	11th to 20th	Night	26% 20% 3 14% 19% 17%	7218
	21st to end	Night	34% 22% 5% 15% 16% 7%	7746
February	1st to 10th	Night	15% 59% 3 6% 7% 10%	2520
	11th to 20th	Night	14% 58% 4 10% 9% 5%	2458
	21st to end	Night	14% 59% 4 9% 8% 5%	2076
March	1st to 10th	Night	26% 29% 6% 17% 7% 14%	5260
	11th to 20th	Night	26% 29% 3 6% 13% 22%	5090
	21st to end	Night	20% 28% 5% 19% 19% 9%	5588
April	1st to 10th	Night	13% 59% 4 10% 6% 7%	2310
	11th to 20th	Night	16% 60% 6% 6% 7% 5%	2180
	21st to end	Night	16% 59% 6% 8% 8% 3	2100
May	1st to 10th	Night	29% 31% 8% 17% 11% 4	4185
	11th to 20th	Night	14% 29% 12% 15% 18% 12%	4054
	21st to end	Night	26% 30% 11% 26% 7%	4452
June	1st to 10th	Night	3 62% 8% 17% 9% 1	1800
	11th to 20th	Night	9% 63% 3 12% 12% 1	1800
	21st to end	Night	10% 62% 11% 11% 6% 1	1800
July	1st to 10th	Night	24% 30% 17% 25% 3	4035
	11th to 20th	Night	22% 27% 21% 25% 4	4026
	21st to end	Night	20% 27% 16% 25% 11% 1	4663
August	1st to 10th	Night	3 35% 9% 32% 20%	3244
	11th to 20th	Night	11% 38% 21% 24% 5%	3243
	21st to end	Night	7% 38% 19% 25% 10% 1	3683
September	1st to 10th	Night	14% 60% 8% 9% 8% 3	2200
	11th to 20th	Night	13% 58% 8% 13% 7% 1	2200
	21st to end	Night	13% 58% 7% 16% 4 2	2200
October	1st to 10th	Night	11% 37% 4 9% 12% 27%	3590
	11th to 20th	Night	12% 36% 7% 10% 17% 18%	3570
	21st to end	Night	15% 36% 5% 12% 21% 11%	4187
November	1st to 10th	Night	18% 54% 6% 9% 7% 6%	2460
	11th to 20th	Night	19% 54% 5% 9% 6% 7%	2678
	21st to end	Night	20% 54% 3 8% 10% 4	2730
December	1st to 10th	Night	44% 34% 4 5% 7% 5%	4380
	11th to 20th	Night	24% 32% 5% 17% 10% 11%	4947
	21st to end	Night	23% 28% 5% 14% 15% 16%	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	20% 6% 21% 34% 15% 5%	330
	11th to 20th	Day	18% 7% 24% 32% 17% 3	330
	21st to end	Day	22% 6% 30% 24% 16% 1	363
February	1st to 10th	Day	15% 7% 26% 26% 20% 5%	330
	11th to 20th	Day	18% 7% 29% 31% 13% 2	330
	21st to end	Day	16% 7% 27% 39% 11%	273
March	1st to 10th	Day	18% 6% 33% 30% 12% 1	330
	11th to 20th	Day	12% 6% 36% 35% 9% 2	330
	21st to end	Day	10% 6% 35% 36% 12% 1	363
April	1st to 10th	Day	11% 9% 34% 35% 10%	330
	11th to 20th	Day	12% 9% 34% 32% 13% 1	422
	21st to end	Day	8% 7% 41% 34% 9% 1	540
May	1st to 10th	Day	10% 7% 34% 36% 11% 1	659
	11th to 20th	Day	12% 3 33% 40% 10% 2	725
	21st to end	Day	7% 3 26% 48% 15% 1	789
June	1st to 10th	Day	2 1 11% 50% 30% 4	730
	11th to 20th	Day	4 1 11% 55% 26% 3	730
	21st to end	Day	5% 1 10% 42% 32% 9%	730
July	1st to 10th	Day	7% 1 10% 37% 36% 9%	721
	11th to 20th	Day	3 1 6% 38% 45% 6%	718
	21st to end	Day	3 1 5% 42% 38% 11%	640
August	1st to 10th	Day	1 4 35% 44% 15%	527
	11th to 20th	Day	3 1 2 32% 46% 17%	517
	21st to end	Day	4 2 3 26% 35% 30%	533
September	1st to 10th	Day	9% 5% 19% 43% 23%	330
	11th to 20th	Day	4 2 5% 14% 37% 38%	330
	21st to end	Day	5% 5% 16% 45% 28%	330
October	1st to 10th	Day	8% 2 4 20% 40% 26%	330
	11th to 20th	Day	12% 1 7% 29% 34% 17%	330
	21st to end	Day	11% 6% 16% 30% 27% 11%	363
November	1st to 10th	Day	11% 4 14% 33% 28% 10%	330
	11th to 20th	Day	17% 4 15% 25% 32% 7%	330
	21st to end	Day	21% 6% 21% 25% 21% 5%	330
December	1st to 10th	Day	19% 4 22% 24% 24% 8%	330
	11th to 20th	Day	18% 8% 20% 25% 24% 5%	330
	21st to end	Day	13% 6% 19% 31% 25% 6%	363
January	1st to 10th	Night	19% 4 22% 42% 12% 1	1050
	11th to 20th	Night	19% 4 28% 41% 8%	887
	21st to end	Night	19% 6% 26% 41% 8%	924
February	1st to 10th	Night	13% 7% 32% 41% 7%	840
	11th to 20th	Night	20% 6% 35% 34% 5%	824
	21st to end	Night	16% 6% 41% 34% 3	692
March	1st to 10th	Night	15% 10% 40% 31% 4	736
	11th to 20th	Night	12% 10% 45% 30% 3	630
	21st to end	Night	10% 7% 52% 29% 2	693
April	1st to 10th	Night	10% 8% 49% 31% 2	630
	11th to 20th	Night	12% 8% 48% 30% 1	623
	21st to end	Night	10% 9% 51% 27% 3	630
May	1st to 10th	Night	10% 7% 49% 32% 2	603
	11th to 20th	Night	8% 5% 47% 37% 3	591
	21st to end	Night	6% 4 47% 38% 5%	650
June	1st to 10th	Night	2 1 30% 57% 9%	600
	11th to 20th	Night	3 1 36% 54% 6% 1	600
	21st to end	Night	3 1 25% 56% 14% 1	600
July	1st to 10th	Night	7% 1 16% 62% 12% 1	585
	11th to 20th	Night	3 1 13% 69% 14%	582
	21st to end	Night	4 2 13% 68% 14%	657
August	1st to 10th	Night	2 1 12% 67% 17% 1	597
	11th to 20th	Night	3 12% 67% 16% 1	594
	21st to end	Night	4 1 7% 59% 27% 3	660
September	1st to 10th	Night	9% 1 10% 48% 27% 4	600
	11th to 20th	Night	9% 1 8% 43% 35% 4	600
	21st to end	Night	8% 10% 47% 31% 4	600
October	1st to 10th	Night	5% 1 11% 50% 31% 1	600
	11th to 20th	Night	11% 1 16% 49% 23% 1	600
	21st to end	Night	9% 4 24% 42% 20% 1	839
November	1st to 10th	Night	11% 3 21% 43% 21% 1	820
	11th to 20th	Night	14% 3 18% 43% 20% 2	998
	21st to end	Night	17% 4 23% 38% 16% 1	1050
December	1st to 10th	Night	20% 3 20% 42% 14% 1	1050
	11th to 20th	Night	21% 5% 22% 41% 11%	1050
	21st to end	Night	15% 4 25% 41% 15%	1155

Page generated at 2026-04-29 01:21:48. Version ac07

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