Corpus Christi
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Corpus Christi clear sky chart from 2005-11-06 to 2024-01-16.

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	11% 5% 2 5% 5% 3 5% 5% 6% 9% 45%	74892
	Night	12% 5% 2 5% 4 3 4 4 5% 8% 47%	74925
Transparency	Day	2 93% 1 2 1 1	74617
	Night	3 92% 1 1 1 1	74720
Seeing	Day	12% 3 12% 30% 34% 9%	13439
	Night	14% 4 15% 33% 29% 5%	23507

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	18% 6% 3 6% 4 3 3 3 4 6% 43%	1707
	11th to 20th	Day	19% 6% 3 5% 5% 2 3 5% 4 6% 43%	1665
	21st to end	Day	16% 7% 3 6% 5% 2 4 4 5% 7% 41%	1935
February	1st to 10th	Day	21% 6% 3 6% 4 3 4 4 5% 5% 39%	1800
	11th to 20th	Day	18% 7% 3 5% 5% 3 3 3 4 7% 41%	1749
	21st to end	Day	18% 7% 3 4 5% 3 3 3 5% 5% 43%	1534
March	1st to 10th	Day	18% 7% 3 5% 5% 2 4 4 5% 8% 39%	1980
	11th to 20th	Day	18% 7% 3 5% 5% 2 5% 4 4 7% 39%	1980
	21st to end	Day	12% 4 2 4 5% 3 4 5% 5% 7% 48%	2178
April	1st to 10th	Day	13% 7% 2 5% 5% 3 5% 5% 6% 8% 41%	1980
	11th to 20th	Day	17% 6% 3 6% 6% 3 3 4 5% 7% 41%	1956
	21st to end	Day	12% 5% 3 5% 5% 3 4 4 7% 8% 44%	2124
May	1st to 10th	Day	9% 6% 3 5% 5% 3 5% 6% 6% 9% 43%	2340
	11th to 20th	Day	8% 6% 2 6% 5% 4 5% 6% 6% 9% 43%	2302
	21st to end	Day	7% 4 2 4 5% 3 6% 6% 8% 11% 44%	2531
June	1st to 10th	Day	4 2 1 3 4 3 4 5% 7% 12% 55%	2340
	11th to 20th	Day	4 3 2 4 5% 3 5% 5% 7% 13% 49%	2340
	21st to end	Day	6% 4 2 4 5% 4 6% 7% 8% 13% 41%	2340
July	1st to 10th	Day	8% 6% 3 6% 5% 4 7% 6% 6% 10% 40%	2340
	11th to 20th	Day	3 2 2 3 5% 4 5% 5% 7% 12% 52%	2340
	21st to end	Day	3 3 2 4 4 3 4 6% 6% 13% 52%	2546
August	1st to 10th	Day	2 1 1 2 4 2 4 4 6% 11% 62%	2314
	11th to 20th	Day	4 3 1 3 4 2 4 4 8% 13% 53%	2123
	21st to end	Day	7% 4 2 4 5% 3 5% 6% 8% 14% 43%	2188
September	1st to 10th	Day	8% 4 2 6% 6% 4 6% 7% 8% 12% 37%	1980
	11th to 20th	Day	10% 6% 3 6% 6% 4 5% 5% 6% 9% 40%	1980
	21st to end	Day	9% 5% 2 5% 4 3 5% 5% 8% 11% 45%	1980
October	1st to 10th	Day	6% 3 2 5% 4 3 6% 5% 5% 9% 52%	1980
	11th to 20th	Day	10% 5% 2 5% 4 3 4 4 5% 8% 51%	1838
	21st to end	Day	9% 4 2 4 3 2 4 4 4 8% 57%	1980
November	1st to 10th	Day	9% 4 2 5% 5% 3 5% 5% 6% 9% 46%	1858
	11th to 20th	Day	14% 6% 2 6% 4 3 3 4 4 7% 46%	1900
	21st to end	Day	16% 6% 2 5% 5% 3 5% 5% 5% 6% 41%	1758
December	1st to 10th	Day	18% 6% 3 5% 4 2 4 4 5% 5% 43%	1710
	11th to 20th	Day	15% 7% 3 6% 5% 4 4 5% 5% 7% 39%	2161
	21st to end	Day	17% 6% 2 5% 5% 3 4 4 5% 7% 42%	3135
January	1st to 10th	Night	19% 6% 2 5% 4 2 3 3 4 6% 45%	2458
	11th to 20th	Night	19% 7% 2 5% 3 3 2 3 3 6% 47%	2406
	21st to end	Night	18% 6% 3 5% 5% 3 4 4 4 6% 42%	2434
February	1st to 10th	Night	19% 7% 3 5% 4 3 4 4 4 6% 41%	2160
	11th to 20th	Night	19% 7% 2 4 3 2 3 4 4 7% 44%	2098
	21st to end	Night	20% 8% 3 5% 5% 2 3 3 3 6% 41%	1721
March	1st to 10th	Night	17% 7% 2 4 4 2 4 4 5% 8% 43%	1980
	11th to 20th	Night	17% 9% 3 6% 5% 2 4 4 4 7% 39%	1980
	21st to end	Night	14% 7% 3 4 4 2 3 2 4 8% 49%	2178
April	1st to 10th	Night	15% 8% 3 6% 6% 3 4 5% 6% 8% 38%	1980
	11th to 20th	Night	19% 6% 3 5% 4 2 4 3 4 8% 42%	1953
	21st to end	Night	16% 7% 3 7% 5% 3 4 4 5% 7% 40%	1831
May	1st to 10th	Night	13% 7% 2 5% 4 3 5% 5% 5% 9% 40%	1620
	11th to 20th	Night	12% 5% 2 5% 5% 4 5% 5% 8% 10% 40%	1593
	21st to end	Night	7% 5% 2 6% 5% 4 5% 6% 8% 13% 39%	1745
June	1st to 10th	Night	4 2 2 3 4 3 4 5% 8% 10% 54%	1620
	11th to 20th	Night	4 3 1 4 5% 3 5% 6% 7% 13% 49%	1620
	21st to end	Night	5% 3 2 4 4 4 5% 6% 8% 11% 47%	1620
July	1st to 10th	Night	6% 4 2 6% 4 4 5% 6% 8% 13% 42%	1620
	11th to 20th	Night	2 2 2 3 4 3 4 5% 7% 14% 56%	1620
	21st to end	Night	3 2 1 3 4 2 4 4 6% 13% 59%	1772
August	1st to 10th	Night	1 1 1 3 2 3 3 5% 10% 71%	1619
	11th to 20th	Night	3 2 1 3 3 2 3 4 7% 12% 60%	1778
	21st to end	Night	3 4 1 4 5% 2 5% 5% 6% 12% 53%	2167
September	1st to 10th	Night	6% 5% 2 6% 5% 3 5% 6% 7% 10% 46%	1980
	11th to 20th	Night	9% 5% 3 5% 4 3 4 5% 7% 10% 44%	1980
	21st to end	Night	6% 4 2 5% 4 3 5% 4 5% 9% 53%	1980
October	1st to 10th	Night	4 2 1 3 4 3 5% 5% 5% 9% 60%	1980
	11th to 20th	Night	10% 4 2 4 4 2 3 3 5% 8% 57%	2101
	21st to end	Night	9% 3 2 3 3 2 3 2 4 7% 62%	2376
November	1st to 10th	Night	11% 4 2 4 3 2 4 3 6% 7% 55%	2220
	11th to 20th	Night	15% 5% 3 5% 4 2 3 4 3 6% 51%	2280
	21st to end	Night	16% 6% 2 5% 4 3 4 4 5% 6% 44%	2417
December	1st to 10th	Night	17% 6% 3 5% 5% 2 3 3 3 6% 45%	2470
	11th to 20th	Night	18% 7% 4 6% 5% 2 4 4 5% 7% 38%	3036
	21st to end	Night	14% 8% 3 5% 4 2 5% 4 6% 6% 43%	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	3 90% 1 2 2 3	1708
	11th to 20th	Day	2 92% 1 2 1 2	1665
	21st to end	Day	4 94% 1	1935
February	1st to 10th	Day	2 95% 1 2 1	1800
	11th to 20th	Day	2 94% 1 1 2	1759
	21st to end	Day	3 95% 1 1	1534
March	1st to 10th	Day	2 95% 1 1 1	1980
	11th to 20th	Day	100%	1980
	21st to end	Day	100%	2178
April	1st to 10th	Day	100%	1980
	11th to 20th	Day	100%	1956
	21st to end	Day	100%	2124
May	1st to 10th	Day	100%	2340
	11th to 20th	Day	100%	2306
	21st to end	Day	100%	2531
June	1st to 10th	Day	100%	2340
	11th to 20th	Day	100%	2340
	21st to end	Day	98% 1	2340
July	1st to 10th	Day	1 94% 2 1 1	2276
	11th to 20th	Day	94% 1 3 2	2271
	21st to end	Day	1 94% 2 3	2405
August	1st to 10th	Day	94% 3 2	2300
	11th to 20th	Day	94% 2 2 1	2123
	21st to end	Day	1 94% 1 2 1 1	2188
September	1st to 10th	Day	95% 1 2 1	1980
	11th to 20th	Day	1 95% 2 1 2	1980
	21st to end	Day	1 95% 2 3	1980
October	1st to 10th	Day	4 94% 1	1980
	11th to 20th	Day	1 95% 1 2 1	1838
	21st to end	Day	2 95% 1 1	1980
November	1st to 10th	Day	3 92% 1 3 1 1	1858
	11th to 20th	Day	5% 90% 2 2	1900
	21st to end	Day	6% 90% 1 1 2	1758
December	1st to 10th	Day	6% 90% 1 1 1 1	1710
	11th to 20th	Day	11% 71% 3 3 7% 5%	2159
	21st to end	Day	18% 55% 2 12% 9% 4	3135
January	1st to 10th	Night	4 90% 1 1 1 3	2458
	11th to 20th	Night	2 92% 1 2 1 2	2406
	21st to end	Night	4 95% 1	2434
February	1st to 10th	Night	1 94% 1 1 1 2	2160
	11th to 20th	Night	2 94% 1 1 1 1	2098
	21st to end	Night	3 95% 1 1	1721
March	1st to 10th	Night	1 95% 2 1 1	1980
	11th to 20th	Night	100%	1980
	21st to end	Night	100%	2178
April	1st to 10th	Night	100%	1980
	11th to 20th	Night	100%	1953
	21st to end	Night	100%	1831
May	1st to 10th	Night	100%	1620
	11th to 20th	Night	100%	1594
	21st to end	Night	100%	1746
June	1st to 10th	Night	100%	1620
	11th to 20th	Night	100%	1620
	21st to end	Night	98% 1	1620
July	1st to 10th	Night	1 94% 2 1 1	1575
	11th to 20th	Night	1 94% 1 2 2	1566
	21st to end	Night	94% 2 4	1673
August	1st to 10th	Night	94% 4 1	1609
	11th to 20th	Night	1 95% 1 2 1	1778
	21st to end	Night	1 95% 2 1	2167
September	1st to 10th	Night	94% 4 2	1980
	11th to 20th	Night	1 95% 2 2 1	1980
	21st to end	Night	95% 1 3 1	1980
October	1st to 10th	Night	3 95% 2	1980
	11th to 20th	Night	1 95% 1 2 2	2101
	21st to end	Night	2 95% 1 1 1	2376
November	1st to 10th	Night	4 92% 1 2 2	2220
	11th to 20th	Night	5% 90% 2 3	2280
	21st to end	Night	5% 90% 1 1 1 3	2417
December	1st to 10th	Night	6% 90% 1 2 1	2470
	11th to 20th	Night	12% 74% 1 3 3 6%	3037
	21st to end	Night	19% 55% 6% 6% 9% 6%	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% 8% 24% 35% 13%	270
	11th to 20th	Day	20% 9% 18% 39% 12% 2	255
	21st to end	Day	20% 5% 31% 33% 11%	264
February	1st to 10th	Day	26% 4 23% 35% 12% 1	240
	11th to 20th	Day	24% 7% 23% 35% 11%	240
	21st to end	Day	24% 5% 33% 32% 5% 1	198
March	1st to 10th	Day	24% 4 24% 38% 10%	240
	11th to 20th	Day	25% 5% 28% 34% 8%	240
	21st to end	Day	17% 8% 30% 40% 6%	264
April	1st to 10th	Day	15% 4 32% 39% 9% 1	240
	11th to 20th	Day	19% 9% 26% 31% 14% 1	234
	21st to end	Day	15% 5% 27% 38% 14% 1	384
May	1st to 10th	Day	11% 4 27% 46% 12%	603
	11th to 20th	Day	10% 5% 18% 47% 18% 2	625
	21st to end	Day	7% 3 13% 46% 29% 2	679
June	1st to 10th	Day	5% 2 5% 35% 46% 8%	630
	11th to 20th	Day	6% 1 5% 39% 45% 6%	630
	21st to end	Day	7% 1 4 25% 49% 14%	630
July	1st to 10th	Day	7% 1 3 26% 49% 14%	621
	11th to 20th	Day	3 1 18% 59% 18%	618
	21st to end	Day	4 1 1 16% 57% 20%	684
August	1st to 10th	Day	1 1 1 16% 59% 23%	612
	11th to 20th	Day	3 1 1 15% 62% 17%	437
	21st to end	Day	7% 1 2 11% 46% 34%	307
September	1st to 10th	Day	9% 3 14% 52% 22%	270
	11th to 20th	Day	9% 1 1 13% 47% 30%	270
	21st to end	Day	8% 3 4 13% 50% 22%	270
October	1st to 10th	Day	9% 4 3 25% 47% 13%	270
	11th to 20th	Day	14% 2 4 29% 40% 11%	270
	21st to end	Day	13% 3 18% 34% 29% 3	297
November	1st to 10th	Day	13% 4 9% 32% 39% 3	270
	11th to 20th	Day	22% 4 11% 32% 26% 4	270
	21st to end	Day	28% 6% 18% 31% 14% 3	270
December	1st to 10th	Day	20% 6% 16% 33% 22% 3	270
	11th to 20th	Day	23% 7% 21% 33% 15% 1	270
	21st to end	Day	22% 8% 20% 34% 14% 2	297
January	1st to 10th	Night	21% 7% 23% 34% 14% 1	950
	11th to 20th	Night	21% 6% 22% 38% 13%	926
	21st to end	Night	21% 5% 25% 36% 12%	850
February	1st to 10th	Night	24% 6% 23% 38% 8%	720
	11th to 20th	Night	23% 7% 23% 36% 11%	704
	21st to end	Night	26% 6% 28% 31% 9%	537
March	1st to 10th	Night	19% 6% 22% 38% 15%	540
	11th to 20th	Night	21% 6% 20% 42% 10%	540
	21st to end	Night	15% 5% 23% 45% 12% 1	594
April	1st to 10th	Night	17% 4 26% 41% 11%	540
	11th to 20th	Night	22% 6% 21% 37% 14%	533
	21st to end	Night	18% 4 23% 41% 13%	540
May	1st to 10th	Night	14% 3 22% 46% 15%	540
	11th to 20th	Night	12% 2 18% 49% 18% 2	531
	21st to end	Night	7% 2 13% 43% 33% 1	584
June	1st to 10th	Night	5% 1 3 36% 51% 4	540
	11th to 20th	Night	5% 1 3 45% 45% 2	540
	21st to end	Night	5% 1 5% 29% 49% 11%	540
July	1st to 10th	Night	6% 2 2 29% 49% 11%	525
	11th to 20th	Night	3 1 1 18% 60% 16%	522
	21st to end	Night	4 1 1 19% 63% 12%	591
August	1st to 10th	Night	1 1 14% 67% 17%	537
	11th to 20th	Night	4 1 1 11% 70% 13%	534
	21st to end	Night	4 1 3 14% 52% 26%	594
September	1st to 10th	Night	6% 1 2 17% 55% 18%	540
	11th to 20th	Night	10% 2 2 14% 51% 20%	540
	21st to end	Night	8% 1 3 22% 54% 12%	540
October	1st to 10th	Night	4 1 5% 24% 55% 11%	540
	11th to 20th	Night	12% 2 8% 34% 39% 5%	661
	21st to end	Night	10% 4 13% 39% 32% 4	792
November	1st to 10th	Night	10% 3 10% 35% 37% 5%	740
	11th to 20th	Night	17% 3 16% 34% 27% 3	760
	21st to end	Night	21% 6% 18% 34% 19% 3	897
December	1st to 10th	Night	20% 5% 18% 31% 22% 4	950
	11th to 20th	Night	22% 6% 20% 35% 16% 1	950
	21st to end	Night	21% 7% 24% 33% 14% 1	1045

Page generated at 2024-01-13 00:38:12. Version ac07

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