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 2024-07-31.

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% 51%	90148
	Night	11% 5% 2 4 3 3 3 3 5% 7% 54%	89730
Transparency	Day	17% 54% 5% 11% 9% 5%	89930
	Night	16% 53% 5% 11% 9% 5%	89553
Seeing	Day	9% 4 18% 35% 26% 8%	14134
	Night	12% 4 27% 44% 13% 1	24133

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	13% 5% 2 6% 4 3 3 3 3 5% 53%	2847
	11th to 20th	Day	12% 4 1 3 3 3 2 2 4 6% 58%	3116
	21st to end	Day	16% 7% 2 6% 4 4 3 4 6% 8% 40%	3487
February	1st to 10th	Day	12% 8% 3 7% 5% 4 3 3 4 5% 47%	1900
	11th to 20th	Day	15% 6% 2 5% 3 3 3 3 4 5% 52%	1849
	21st to end	Day	12% 6% 2 4 3 4 3 3 5% 6% 53%	1570
March	1st to 10th	Day	14% 6% 2 6% 4 4 5% 4 7% 8% 41%	3281
	11th to 20th	Day	23% 7% 3 5% 4 3 4 3 5% 5% 38%	3480
	21st to end	Day	8% 4 1 3 2 3 3 3 5% 7% 60%	3814
April	1st to 10th	Day	12% 5% 2 5% 4 4 4 3 5% 6% 51%	2090
	11th to 20th	Day	10% 7% 2 6% 4 3 4 4 5% 8% 48%	2154
	21st to end	Day	10% 7% 2 5% 4 4 4 4 5% 7% 49%	2280
May	1st to 10th	Day	12% 6% 2 6% 4 4 3 4 6% 9% 45%	4010
	11th to 20th	Day	9% 6% 2 7% 4 4 4 4 5% 7% 48%	4082
	21st to end	Day	5% 4 2 5% 4 4 4 4 5% 9% 55%	4477
June	1st to 10th	Day	2 2 1 4 3 4 4 4 7% 10% 58%	2470
	11th to 20th	Day	3 3 1 3 3 4 3 3 5% 9% 62%	2470
	21st to end	Day	5% 4 1 4 5% 5% 5% 5% 6% 10% 49%	2470
July	1st to 10th	Day	6% 6% 2 7% 6% 5% 5% 4 6% 9% 45%	2470
	11th to 20th	Day	4 3 1 4 4 3 5% 4 5% 8% 58%	2470
	21st to end	Day	3 3 1 4 4 4 4 4 6% 9% 57%	2532
August	1st to 10th	Day	1 2 1 2 3 3 3 3 5% 7% 71%	2149
	11th to 20th	Day	4 1 1 3 3 3 4 4 6% 9% 64%	2123
	21st to end	Day	6% 4 1 5% 5% 5% 5% 4 6% 7% 53%	2332
September	1st to 10th	Day	10% 7% 2 8% 5% 6% 6% 4 4 7% 42%	1980
	11th to 20th	Day	10% 5% 2 6% 5% 6% 5% 5% 7% 8% 41%	1980
	21st to end	Day	7% 5% 1 5% 5% 5% 4 4 6% 8% 48%	1980
October	1st to 10th	Day	6% 4 2 5% 4 4 4 4 5% 5% 57%	1980
	11th to 20th	Day	12% 5% 2 5% 3 4 4 3 4 7% 51%	1980
	21st to end	Day	10% 4 2 4 3 3 3 2 4 5% 60%	1998
November	1st to 10th	Day	11% 6% 2 6% 4 3 4 3 4 6% 50%	1858
	11th to 20th	Day	14% 7% 2 6% 4 3 2 3 4 4 51%	1753
	21st to end	Day	16% 7% 2 5% 3 4 3 3 4 5% 48%	1710
December	1st to 10th	Day	16% 7% 2 5% 3 3 4 3 6% 6% 45%	1710
	11th to 20th	Day	16% 8% 2 6% 3 4 3 4 4 6% 45%	2161
	21st to end	Day	12% 6% 2 5% 3 3 4 3 5% 7% 50%	3135
January	1st to 10th	Night	14% 5% 2 3 3 2 3 3 5% 6% 54%	4108
	11th to 20th	Night	12% 4 1 3 2 2 2 2 4 7% 61%	3882
	21st to end	Night	19% 6% 2 6% 4 3 4 3 4 7% 42%	4180
February	1st to 10th	Night	11% 7% 2 5% 3 3 4 3 5% 6% 52%	2280
	11th to 20th	Night	16% 6% 1 5% 2 3 3 2 4 6% 51%	2218
	21st to end	Night	11% 5% 2 4 2 3 3 3 4 6% 55%	1884
March	1st to 10th	Night	14% 6% 2 5% 4 4 4 4 6% 7% 45%	3575
	11th to 20th	Night	22% 8% 3 6% 4 4 4 3 4 5% 36%	3480
	21st to end	Night	10% 3 1 3 2 2 2 3 5% 6% 62%	3817
April	1st to 10th	Night	10% 4 2 4 3 4 4 3 6% 9% 51%	2090
	11th to 20th	Night	12% 5% 2 4 3 3 4 3 5% 7% 52%	1970
	21st to end	Night	12% 6% 2 5% 4 3 3 3 5% 8% 49%	1900
May	1st to 10th	Night	10% 5% 2 5% 3 4 4 3 6% 8% 50%	2891
	11th to 20th	Night	8% 6% 2 5% 4 3 4 3 6% 7% 52%	2823
	21st to end	Night	5% 5% 2 5% 4 3 4 3 6% 9% 53%	3090
June	1st to 10th	Night	2 2 1 3 3 3 3 3 6% 10% 65%	1710
	11th to 20th	Night	1 2 1 3 2 3 3 3 5% 9% 67%	1710
	21st to end	Night	3 3 1 4 4 4 5% 4 7% 11% 54%	1710
July	1st to 10th	Night	7% 5% 2 4 4 4 4 4 6% 10% 50%	1710
	11th to 20th	Night	3 2 1 3 3 3 4 4 7% 10% 61%	1710
	21st to end	Night	4 4 1 3 3 2 3 3 5% 9% 64%	2011
August	1st to 10th	Night	1 2 1 1 2 2 2 2 4 7% 76%	1790
	11th to 20th	Night	2 2 1 3 3 3 4 3 5% 10% 63%	1778
	21st to end	Night	4 3 1 5% 4 4 4 3 6% 9% 57%	2024
September	1st to 10th	Night	8% 7% 2 6% 4 4 5% 4 7% 9% 44%	1980
	11th to 20th	Night	8% 5% 2 5% 5% 5% 4 4 8% 10% 46%	1980
	21st to end	Night	8% 3 2 5% 3 3 3 4 6% 9% 55%	1980
October	1st to 10th	Night	5% 3 1 4 4 3 3 4 4 7% 62%	1980
	11th to 20th	Night	12% 4 2 3 3 3 3 3 4 6% 57%	1980
	21st to end	Night	9% 4 1 3 2 2 3 2 3 4 67%	2339
November	1st to 10th	Night	11% 5% 1 4 2 3 3 3 5% 6% 58%	2220
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 4 5% 54%	2422
	21st to end	Night	16% 6% 2 4 4 3 3 3 4 6% 51%	2470
December	1st to 10th	Night	16% 7% 2 4 3 3 3 2 4 6% 50%	2470
	11th to 20th	Night	16% 6% 2 5% 3 2 2 3 4 6% 49%	3036
	21st to end	Night	10% 6% 2 5% 4 3 4 4 5% 8% 49%	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	23% 37% 4 5% 19% 11%	2848
	11th to 20th	Day	15% 36% 3 15% 19% 12%	3116
	21st to end	Day	27% 40% 5% 9% 16% 3	3487
February	1st to 10th	Day	17% 65% 3 3 5% 7%	1900
	11th to 20th	Day	13% 64% 3 7% 8% 5%	1859
	21st to end	Day	15% 65% 4 6% 7% 4	1570
March	1st to 10th	Day	29% 42% 7% 11% 8% 2	3281
	11th to 20th	Day	37% 41% 4 6% 8% 5%	3480
	21st to end	Day	14% 41% 6% 14% 11% 14%	3814
April	1st to 10th	Day	12% 65% 4 6% 6% 7%	2090
	11th to 20th	Day	14% 66% 3 6% 6% 4	2154
	21st to end	Day	12% 65% 3 7% 7% 6%	2280
May	1st to 10th	Day	23% 42% 9% 14% 8% 5%	4047
	11th to 20th	Day	22% 42% 7% 12% 8% 9%	4086
	21st to end	Day	14% 41% 6% 31% 7% 1	4489
June	1st to 10th	Day	6% 66% 5% 13% 9% 1	2470
	11th to 20th	Day	11% 66% 3 8% 10% 2	2470
	21st to end	Day	12% 65% 6% 8% 8% 1	2470
July	1st to 10th	Day	10% 59% 8% 15% 7%	2406
	11th to 20th	Day	9% 59% 7% 14% 8% 3	2401
	21st to end	Day	7% 59% 7% 17% 9% 1	2398
August	1st to 10th	Day	6% 64% 6% 16% 8% 1	2136
	11th to 20th	Day	6% 65% 4 16% 8% 1	2123
	21st to end	Day	8% 63% 7% 14% 7% 2	2332
September	1st to 10th	Day	15% 64% 5% 7% 7% 3	1980
	11th to 20th	Day	13% 65% 5% 9% 6% 2	1980
	21st to end	Day	15% 65% 6% 10% 4	1980
October	1st to 10th	Day	12% 65% 5% 9% 8%	1980
	11th to 20th	Day	13% 63% 4 7% 6% 7%	1980
	21st to end	Day	14% 63% 3 6% 9% 5%	1998
November	1st to 10th	Day	21% 60% 5% 7% 5% 3	1858
	11th to 20th	Day	21% 60% 3 8% 5% 3	1753
	21st to end	Day	19% 59% 3 8% 6% 4	1710
December	1st to 10th	Day	18% 60% 3 9% 7% 3	1710
	11th to 20th	Day	20% 49% 5% 7% 8% 12%	2159
	21st to end	Day	25% 38% 4 13% 16% 5%	3135
January	1st to 10th	Night	21% 37% 4 8% 15% 14%	4108
	11th to 20th	Night	15% 36% 2 12% 18% 17%	3882
	21st to end	Night	28% 40% 4 9% 14% 5%	4180
February	1st to 10th	Night	15% 65% 3 4 6% 8%	2280
	11th to 20th	Night	12% 64% 3 8% 8% 5%	2218
	21st to end	Night	13% 65% 5% 7% 6% 4	1884
March	1st to 10th	Night	30% 42% 7% 13% 5% 3	3575
	11th to 20th	Night	38% 42% 5% 6% 6% 3	3480
	21st to end	Night	13% 40% 5% 17% 15% 10%	3817
April	1st to 10th	Night	11% 65% 3 9% 6% 6%	2090
	11th to 20th	Night	13% 66% 5% 4 6% 4	1970
	21st to end	Night	12% 64% 4 7% 8% 3	1900
May	1st to 10th	Night	19% 42% 9% 15% 9% 5%	2919
	11th to 20th	Night	17% 41% 10% 12% 12% 8%	2824
	21st to end	Night	18% 41% 6% 28% 6%	3099
June	1st to 10th	Night	3 65% 7% 15% 10% 1	1710
	11th to 20th	Night	8% 66% 3 10% 11% 1	1710
	21st to end	Night	9% 65% 8% 11% 6% 1	1710
July	1st to 10th	Night	5% 61% 10% 17% 6%	1665
	11th to 20th	Night	8% 59% 8% 15% 8% 1	1656
	21st to end	Night	6% 58% 8% 20% 7% 1	1905
August	1st to 10th	Night	5% 63% 6% 18% 7% 1	1779
	11th to 20th	Night	7% 65% 5% 15% 7% 1	1778
	21st to end	Night	5% 63% 9% 16% 5% 2	2024
September	1st to 10th	Night	11% 65% 6% 8% 7% 2	1980
	11th to 20th	Night	11% 64% 7% 12% 6% 1	1980
	21st to end	Night	12% 65% 7% 13% 3	1980
October	1st to 10th	Night	10% 64% 6% 13% 6% 1	1980
	11th to 20th	Night	11% 63% 4 9% 8% 6%	1980
	21st to end	Night	13% 62% 3 6% 9% 7%	2339
November	1st to 10th	Night	17% 60% 7% 8% 5% 3	2220
	11th to 20th	Night	19% 60% 5% 8% 4 4	2422
	21st to end	Night	18% 60% 3 7% 9% 3	2470
December	1st to 10th	Night	16% 59% 3 8% 9% 4	2470
	11th to 20th	Night	19% 49% 3 10% 9% 11%	3037
	21st to end	Night	26% 40% 6% 9% 10% 10%	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	16% 7% 21% 35% 18% 3	270
	21st to end	Day	21% 6% 30% 24% 17% 2	297
February	1st to 10th	Day	15% 9% 28% 26% 18% 4	270
	11th to 20th	Day	18% 9% 32% 27% 13% 2	270
	21st to end	Day	16% 8% 30% 37% 9%	225
March	1st to 10th	Day	19% 5% 33% 30% 13% 1	270
	11th to 20th	Day	14% 7% 33% 34% 10% 1	270
	21st to end	Day	10% 7% 38% 37% 8%	297
April	1st to 10th	Day	11% 9% 38% 33% 9%	270
	11th to 20th	Day	10% 9% 32% 33% 14% 1	352
	21st to end	Day	8% 7% 42% 33% 9% 1	460
May	1st to 10th	Day	9% 6% 34% 37% 12% 1	606
	11th to 20th	Day	12% 3 32% 40% 11% 2	675
	21st to end	Day	7% 3 26% 47% 15% 1	734
June	1st to 10th	Day	2 1 12% 50% 31% 4	680
	11th to 20th	Day	3 1 10% 55% 28% 3	680
	21st to end	Day	6% 1 10% 42% 32% 9%	680
July	1st to 10th	Day	6% 1 9% 37% 37% 9%	671
	11th to 20th	Day	3 1 5% 37% 47% 7%	668
	21st to end	Day	3 2 5% 41% 39% 11%	590
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 27% 42% 8%	803
	21st to end	Night	18% 7% 25% 42% 8%	836
February	1st to 10th	Night	14% 7% 33% 39% 6%	760
	11th to 20th	Night	21% 6% 35% 34% 5%	744
	21st to end	Night	15% 6% 42% 33% 4	628
March	1st to 10th	Night	14% 10% 40% 32% 4	666
	11th to 20th	Night	12% 9% 44% 31% 3	570
	21st to end	Night	10% 7% 54% 27% 2	627
April	1st to 10th	Night	10% 6% 50% 32% 2	570
	11th to 20th	Night	12% 7% 47% 32% 2	563
	21st to end	Night	10% 9% 51% 26% 3	570
May	1st to 10th	Night	9% 7% 50% 32% 2	570
	11th to 20th	Night	8% 5% 46% 37% 3	561
	21st to end	Night	6% 4 47% 38% 5%	617
June	1st to 10th	Night	2 1 30% 57% 9%	570
	11th to 20th	Night	3 1 35% 55% 6% 1	570
	21st to end	Night	4 1 25% 55% 15% 1	570
July	1st to 10th	Night	7% 1 15% 62% 13% 1	555
	11th to 20th	Night	3 1 12% 69% 15%	552
	21st to end	Night	4 1 13% 67% 14%	624
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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