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 2024-01-17.

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 4 3 4 4 5% 7% 52%	74836
	Night	10% 4 2 4 4 2 4 4 5% 7% 55%	75014
Transparency	Day	32% 6% 11% 22% 20% 10%	74569
	Night	29% 6% 13% 23% 19% 11%	74801
Seeing	Day	10% 3 18% 35% 26% 8%	13357
	Night	12% 4 27% 44% 13% 1	23497

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% 6% 3 4 3 2 3 4 4 6% 50%	1707
	11th to 20th	Day	17% 6% 2 4 4 2 3 3 4 6% 50%	1832
	21st to end	Day	15% 7% 2 6% 4 2 3 4 5% 8% 44%	1980
February	1st to 10th	Day	13% 7% 3 6% 6% 3 4 3 4 5% 46%	1800
	11th to 20th	Day	14% 5% 3 5% 4 3 3 4 4 5% 51%	1749
	21st to end	Day	13% 6% 2 3 4 2 3 3 4 7% 53%	1480
March	1st to 10th	Day	13% 5% 2 4 4 3 4 4 5% 8% 47%	1886
	11th to 20th	Day	12% 6% 2 5% 4 2 3 5% 5% 7% 49%	1980
	21st to end	Day	10% 4 2 3 3 2 3 4 5% 8% 55%	2178
April	1st to 10th	Day	12% 4 2 5% 4 3 4 4 4 6% 51%	1980
	11th to 20th	Day	11% 6% 2 5% 4 2 4 4 4 8% 49%	2039
	21st to end	Day	9% 6% 2 4 4 3 4 4 5% 8% 50%	2160
May	1st to 10th	Day	10% 5% 2 5% 5% 3 4 5% 5% 7% 50%	2295
	11th to 20th	Day	10% 5% 2 6% 5% 3 4 5% 5% 7% 47%	2302
	21st to end	Day	7% 4 2 5% 5% 3 6% 5% 6% 8% 48%	2531
June	1st to 10th	Day	2 2 1 3 4 3 5% 5% 6% 10% 58%	2340
	11th to 20th	Day	2 3 1 3 4 3 4 4 5% 10% 62%	2340
	21st to end	Day	5% 3 2 4 6% 4 5% 6% 6% 10% 50%	2340
July	1st to 10th	Day	7% 5% 2 6% 7% 4 5% 5% 6% 9% 44%	2340
	11th to 20th	Day	4 2 1 3 4 2 4 6% 5% 8% 61%	2340
	21st to end	Day	3 2 2 4 4 3 4 5% 5% 10% 58%	2408
August	1st to 10th	Day	1 1 1 2 3 2 4 4 5% 7% 71%	2149
	11th to 20th	Day	4 1 1 3 3 2 3 5% 6% 9% 64%	2123
	21st to end	Day	6% 4 1 4 5% 4 5% 5% 6% 7% 53%	2332
September	1st to 10th	Day	10% 6% 3 7% 6% 4 6% 5% 4 7% 42%	1980
	11th to 20th	Day	10% 4 2 5% 6% 4 6% 6% 7% 8% 41%	1980
	21st to end	Day	7% 5% 1 5% 6% 4 4 5% 6% 8% 48%	1980
October	1st to 10th	Day	6% 4 2 4 5% 3 4 5% 5% 5% 57%	1980
	11th to 20th	Day	12% 5% 2 4 3 3 4 4 5% 7% 51%	1980
	21st to end	Day	10% 4 2 3 3 2 3 3 4 5% 60%	1998
November	1st to 10th	Day	11% 6% 3 5% 5% 2 3 4 4 6% 50%	1858
	11th to 20th	Day	14% 7% 3 6% 4 2 3 3 3 4 52%	1753
	21st to end	Day	16% 7% 2 4 4 3 3 3 4 5% 48%	1710
December	1st to 10th	Day	17% 6% 3 4 3 3 4 4 5% 7% 45%	1710
	11th to 20th	Day	16% 7% 2 5% 4 2 4 4 4 6% 45%	2161
	21st to end	Day	12% 6% 2 5% 4 2 3 4 5% 7% 50%	3135
January	1st to 10th	Night	16% 5% 2 3 3 2 3 4 4 6% 53%	2458
	11th to 20th	Night	16% 5% 2 4 3 2 3 3 3 6% 53%	2287
	21st to end	Night	16% 4 2 5% 4 2 4 4 4 6% 48%	2376
February	1st to 10th	Night	11% 6% 2 4 4 2 4 3 5% 6% 53%	2160
	11th to 20th	Night	16% 6% 1 4 3 2 3 3 4 6% 52%	2098
	21st to end	Night	12% 5% 2 3 3 2 4 4 4 6% 55%	1776
March	1st to 10th	Night	11% 5% 2 3 4 1 4 4 5% 7% 53%	2071
	11th to 20th	Night	10% 5% 2 5% 4 3 4 4 5% 7% 50%	1980
	21st to end	Night	9% 4 3 3 4 2 3 4 6% 7% 55%	2178
April	1st to 10th	Night	11% 3 2 4 3 3 5% 4 6% 9% 51%	1980
	11th to 20th	Night	12% 4 2 3 3 2 4 3 5% 7% 53%	1866
	21st to end	Night	11% 6% 2 4 4 3 4 4 5% 8% 51%	1800
May	1st to 10th	Night	8% 4 2 4 4 3 4 5% 6% 9% 52%	1661
	11th to 20th	Night	9% 5% 2 4 4 3 5% 5% 7% 9% 48%	1593
	21st to end	Night	5% 4 2 4 5% 3 4 4 7% 10% 51%	1745
June	1st to 10th	Night	2 2 1 3 4 1 3 4 5% 10% 65%	1620
	11th to 20th	Night	1 3 1 3 3 2 4 4 5% 9% 67%	1620
	21st to end	Night	4 2 2 4 4 3 6% 5% 7% 11% 54%	1620
July	1st to 10th	Night	7% 5% 3 4 5% 2 4 5% 6% 10% 49%	1620
	11th to 20th	Night	2 1 1 2 3 2 4 5% 7% 10% 64%	1620
	21st to end	Night	3 3 1 3 3 1 3 4 5% 8% 66%	1904
August	1st to 10th	Night	2 1 1 1 2 1 2 2 4 7% 76%	1790
	11th to 20th	Night	2 2 1 2 4 3 4 4 5% 10% 63%	1778
	21st to end	Night	4 3 1 4 5% 3 4 4 5% 9% 57%	2024
September	1st to 10th	Night	8% 6% 2 5% 5% 3 5% 5% 7% 9% 44%	1980
	11th to 20th	Night	8% 5% 2 4 5% 3 5% 5% 7% 10% 46%	1980
	21st to end	Night	8% 3 2 4 3 3 3 5% 5% 9% 55%	1980
October	1st to 10th	Night	5% 3 1 4 4 2 3 4 4 7% 62%	1980
	11th to 20th	Night	12% 4 2 3 3 2 3 3 4 6% 57%	1980
	21st to end	Night	9% 4 1 2 3 2 3 2 2 4 67%	2339
November	1st to 10th	Night	11% 4 1 3 3 2 3 4 4 6% 58%	2220
	11th to 20th	Night	13% 5% 2 4 4 2 3 3 4 6% 54%	2422
	21st to end	Night	16% 5% 2 3 4 3 2 4 4 5% 51%	2470
December	1st to 10th	Night	16% 5% 3 4 3 1 4 3 4 6% 51%	2470
	11th to 20th	Night	16% 6% 2 4 4 2 3 4 4 6% 50%	3036
	21st to end	Night	10% 6% 2 4 4 2 4 5% 5% 8% 50%	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	37% 4 6% 14% 24% 15%	1708
	11th to 20th	Day	38% 4 6% 17% 17% 19%	1832
	21st to end	Day	40% 4 7% 16% 20% 13%	1980
February	1st to 10th	Day	42% 4 7% 12% 18% 16%	1800
	11th to 20th	Day	36% 4 7% 20% 18% 15%	1759
	21st to end	Day	34% 4 9% 16% 23% 14%	1480
March	1st to 10th	Day	36% 5% 11% 20% 16% 12%	1886
	11th to 20th	Day	36% 6% 10% 14% 16% 18%	1980
	21st to end	Day	28% 6% 13% 18% 21% 15%	2178
April	1st to 10th	Day	34% 5% 11% 19% 20% 12%	1980
	11th to 20th	Day	34% 6% 10% 16% 19% 15%	2039
	21st to end	Day	32% 5% 9% 20% 19% 16%	2160
May	1st to 10th	Day	33% 6% 10% 23% 19% 10%	2295
	11th to 20th	Day	36% 5% 10% 22% 23% 5%	2306
	21st to end	Day	31% 8% 9% 25% 22% 5%	2531
June	1st to 10th	Day	21% 6% 13% 28% 27% 5%	2340
	11th to 20th	Day	20% 5% 11% 29% 27% 8%	2340
	21st to end	Day	29% 9% 14% 25% 19% 4	2340
July	1st to 10th	Day	36% 7% 16% 25% 14% 2	2276
	11th to 20th	Day	22% 7% 15% 31% 21% 5%	2271
	21st to end	Day	18% 8% 17% 36% 17% 2	2274
August	1st to 10th	Day	14% 5% 15% 36% 26% 2	2136
	11th to 20th	Day	17% 7% 17% 38% 20% 2	2123
	21st to end	Day	29% 7% 16% 29% 16% 3	2332
September	1st to 10th	Day	41% 8% 13% 18% 14% 6%	1980
	11th to 20th	Day	38% 8% 14% 21% 15% 3	1980
	21st to end	Day	32% 7% 13% 22% 16% 10%	1980
October	1st to 10th	Day	28% 6% 10% 18% 29% 8%	1980
	11th to 20th	Day	32% 7% 9% 21% 17% 14%	1980
	21st to end	Day	26% 4 6% 16% 29% 19%	1998
November	1st to 10th	Day	35% 4 10% 18% 23% 10%	1858
	11th to 20th	Day	38% 4 7% 20% 20% 12%	1753
	21st to end	Day	39% 5% 8% 19% 15% 15%	1710
December	1st to 10th	Day	39% 5% 10% 20% 17% 10%	1710
	11th to 20th	Day	40% 6% 8% 13% 14% 19%	2159
	21st to end	Day	34% 5% 7% 20% 25% 10%	3135
January	1st to 10th	Night	33% 4 8% 13% 23% 19%	2458
	11th to 20th	Night	36% 4 6% 17% 19% 19%	2287
	21st to end	Night	38% 4 8% 14% 21% 14%	2376
February	1st to 10th	Night	33% 5% 7% 19% 16% 20%	2160
	11th to 20th	Night	34% 4 9% 18% 19% 16%	2098
	21st to end	Night	30% 6% 11% 18% 20% 15%	1776
March	1st to 10th	Night	30% 6% 14% 20% 16% 13%	2071
	11th to 20th	Night	34% 7% 12% 14% 16% 17%	1980
	21st to end	Night	28% 5% 14% 21% 18% 15%	2178
April	1st to 10th	Night	29% 5% 13% 21% 19% 12%	1980
	11th to 20th	Night	31% 5% 13% 19% 17% 14%	1866
	21st to end	Night	33% 6% 11% 20% 17% 13%	1800
May	1st to 10th	Night	29% 7% 16% 21% 16% 11%	1661
	11th to 20th	Night	30% 7% 14% 26% 18% 5%	1594
	21st to end	Night	25% 8% 15% 31% 18% 3	1746
June	1st to 10th	Night	15% 6% 18% 32% 25% 4	1620
	11th to 20th	Night	16% 6% 13% 33% 27% 5%	1620
	21st to end	Night	23% 10% 18% 30% 16% 3	1620
July	1st to 10th	Night	28% 9% 22% 28% 10% 1	1575
	11th to 20th	Night	15% 8% 21% 33% 19% 3	1566
	21st to end	Night	15% 6% 26% 38% 13% 1	1798
August	1st to 10th	Night	9% 5% 21% 46% 18% 1	1779
	11th to 20th	Night	17% 8% 22% 35% 16% 2	1778
	21st to end	Night	23% 9% 21% 33% 12% 3	2024
September	1st to 10th	Night	34% 10% 18% 19% 15% 4	1980
	11th to 20th	Night	31% 9% 17% 27% 13% 2	1980
	21st to end	Night	26% 6% 16% 28% 16% 8%	1980
October	1st to 10th	Night	23% 6% 13% 25% 23% 10%	1980
	11th to 20th	Night	28% 4 13% 23% 17% 15%	1980
	21st to end	Night	24% 3 7% 18% 27% 22%	2339
November	1st to 10th	Night	26% 5% 10% 20% 27% 11%	2220
	11th to 20th	Night	33% 4 10% 20% 20% 14%	2422
	21st to end	Night	36% 4 8% 20% 18% 13%	2470
December	1st to 10th	Night	36% 4 9% 18% 21% 11%	2470
	11th to 20th	Night	37% 4 8% 18% 16% 18%	3037
	21st to end	Night	33% 6% 9% 16% 19% 16%	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	19% 7% 22% 36% 12% 3	270
	11th to 20th	Day	17% 8% 21% 33% 19% 3	258
	21st to end	Day	21% 6% 31% 25% 15% 2	264
February	1st to 10th	Day	16% 8% 26% 26% 19% 4	240
	11th to 20th	Day	17% 8% 33% 28% 13% 2	240
	21st to end	Day	19% 8% 30% 34% 9% 1	198
March	1st to 10th	Day	20% 3 33% 30% 13% 1	240
	11th to 20th	Day	14% 6% 33% 35% 10% 2	240
	21st to end	Day	11% 7% 36% 37% 8%	264
April	1st to 10th	Day	13% 7% 35% 34% 10%	240
	11th to 20th	Day	11% 9% 32% 32% 16% 1	317
	21st to end	Day	8% 7% 42% 33% 10% 1	420
May	1st to 10th	Day	9% 6% 34% 37% 13% 1	558
	11th to 20th	Day	13% 3 32% 40% 11% 2	625
	21st to end	Day	7% 3 25% 48% 15% 1	679
June	1st to 10th	Day	2 1 11% 50% 31% 4	630
	11th to 20th	Day	3 1 11% 55% 27% 3	630
	21st to end	Day	6% 1 10% 42% 32% 9%	630
July	1st to 10th	Day	7% 1 9% 38% 37% 9%	621
	11th to 20th	Day	3 5% 37% 48% 6%	618
	21st to end	Day	2 1 4 42% 39% 11%	546
August	1st to 10th	Day	1 4 37% 44% 14%	447
	11th to 20th	Day	3 1 2 32% 45% 18%	437
	21st to end	Day	5% 2 3 28% 34% 29%	451
September	1st to 10th	Day	10% 6% 16% 44% 24%	270
	11th to 20th	Day	4 1 6% 13% 37% 40%	270
	21st to end	Day	7% 6% 15% 45% 27%	270
October	1st to 10th	Day	10% 2 4 21% 39% 24%	270
	11th to 20th	Day	14% 1 7% 28% 34% 16%	270
	21st to end	Day	13% 7% 17% 29% 25% 9%	297
November	1st to 10th	Day	13% 4 11% 33% 28% 11%	270
	11th to 20th	Day	21% 4 14% 21% 32% 7%	270
	21st to end	Day	21% 6% 22% 26% 19% 5%	270
December	1st to 10th	Day	16% 3 23% 21% 28% 10%	270
	11th to 20th	Day	18% 9% 23% 26% 23% 3	270
	21st to end	Day	16% 5% 21% 32% 22% 5%	297
January	1st to 10th	Night	19% 4 22% 42% 12% 1	950
	11th to 20th	Night	20% 4 26% 42% 8%	791
	21st to end	Night	17% 6% 26% 42% 9%	792
February	1st to 10th	Night	14% 7% 32% 40% 7%	720
	11th to 20th	Night	21% 5% 35% 34% 5%	704
	21st to end	Night	16% 6% 41% 33% 4	592
March	1st to 10th	Night	15% 9% 40% 33% 4	631
	11th to 20th	Night	12% 8% 44% 32% 3	540
	21st to end	Night	10% 6% 53% 28% 2	594
April	1st to 10th	Night	10% 5% 49% 33% 2	540
	11th to 20th	Night	13% 7% 46% 33% 2	533
	21st to end	Night	9% 9% 52% 26% 3	540
May	1st to 10th	Night	8% 7% 50% 33% 3	540
	11th to 20th	Night	8% 5% 45% 38% 4	531
	21st to end	Night	6% 3 46% 40% 5%	584
June	1st to 10th	Night	2 1 28% 58% 10%	540
	11th to 20th	Night	3 1 34% 56% 6% 1	540
	21st to end	Night	4 1 25% 55% 14% 1	540
July	1st to 10th	Night	7% 1 16% 61% 13% 2	525
	11th to 20th	Night	2 12% 71% 15%	522
	21st to end	Night	3 1 13% 68% 14%	591
August	1st to 10th	Night	2 12% 68% 17% 1	537
	11th to 20th	Night	4 11% 67% 17% 1	534
	21st to end	Night	5% 1 7% 58% 27% 3	594
September	1st to 10th	Night	10% 1 11% 49% 25% 4	540
	11th to 20th	Night	9% 1 7% 43% 36% 4	540
	21st to end	Night	9% 11% 45% 31% 4	540
October	1st to 10th	Night	5% 1 12% 51% 28% 1	540
	11th to 20th	Night	12% 1 16% 47% 22% 1	540
	21st to end	Night	10% 5% 23% 41% 20% 1	755
November	1st to 10th	Night	11% 3 20% 43% 22% 1	740
	11th to 20th	Night	14% 3 18% 42% 21% 2	902
	21st to end	Night	18% 4 23% 38% 17% 1	950
December	1st to 10th	Night	18% 3 21% 43% 15% 1	950
	11th to 20th	Night	21% 5% 23% 40% 10% 1	950
	21st to end	Night	16% 4 25% 40% 14%	1045

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