Bentsen-Rio Grande Valley State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bentsen-Rio Grande Valley State Park clear sky chart from 2005-11-06 to 2024-01-12.

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
Transparency	Day	33% 7% 13% 22% 17% 7%	74512
	Night	32% 7% 16% 23% 15% 7%	74746
Seeing	Day	10% 4 19% 35% 25% 9%	13174
	Night	12% 4 24% 39% 18% 1	23314

By Month

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	39% 5% 10% 15% 21% 11%	1708
	11th to 20th	Day	40% 5% 8% 17% 16% 14%	1746
	21st to end	Day	41% 6% 10% 16% 17% 10%	1980
February	1st to 10th	Day	42% 4 8% 15% 18% 12%	1800
	11th to 20th	Day	36% 5% 10% 21% 19% 10%	1759
	21st to end	Day	37% 4 10% 19% 19% 11%	1481
March	1st to 10th	Day	38% 5% 12% 21% 14% 10%	1980
	11th to 20th	Day	40% 7% 11% 15% 16% 11%	1980
	21st to end	Day	32% 6% 13% 22% 16% 11%	2178
April	1st to 10th	Day	35% 6% 12% 21% 17% 9%	1980
	11th to 20th	Day	36% 7% 12% 20% 17% 8%	1956
	21st to end	Day	33% 7% 12% 19% 19% 11%	2058
May	1st to 10th	Day	31% 9% 13% 22% 16% 8%	2340
	11th to 20th	Day	35% 7% 13% 23% 17% 5%	2306
	21st to end	Day	31% 9% 12% 23% 22% 4	2531
June	1st to 10th	Day	23% 8% 14% 30% 22% 4	2340
	11th to 20th	Day	24% 6% 15% 25% 24% 5%	2340
	21st to end	Day	31% 10% 18% 27% 12% 2	2340
July	1st to 10th	Day	38% 10% 16% 24% 10%	2276
	11th to 20th	Day	22% 9% 21% 30% 17% 1	2271
	21st to end	Day	21% 8% 22% 35% 13%	2344
August	1st to 10th	Day	18% 7% 20% 39% 15% 1	2136
	11th to 20th	Day	22% 8% 21% 37% 11% 1	2123
	21st to end	Day	33% 11% 21% 24% 9% 2	2228
September	1st to 10th	Day	41% 10% 15% 18% 13% 2	1980
	11th to 20th	Day	44% 12% 16% 16% 9% 4	1980
	21st to end	Day	36% 9% 15% 21% 13% 7%	1980
October	1st to 10th	Day	29% 8% 11% 20% 25% 7%	1980
	11th to 20th	Day	29% 8% 11% 21% 20% 11%	1935
	21st to end	Day	26% 5% 7% 20% 26% 17%	1980
November	1st to 10th	Day	32% 7% 13% 21% 20% 7%	1858
	11th to 20th	Day	41% 5% 9% 18% 18% 9%	1900
	21st to end	Day	34% 6% 12% 19% 18% 11%	1734
December	1st to 10th	Day	39% 5% 9% 23% 16% 8%	1710
	11th to 20th	Day	38% 8% 12% 14% 16% 13%	2159
	21st to end	Day	40% 6% 7% 21% 20% 7%	3135
January	1st to 10th	Night	38% 4 10% 16% 21% 11%	2458
	11th to 20th	Night	39% 4 10% 16% 14% 16%	2267
	21st to end	Night	42% 6% 10% 17% 16% 9%	2376
February	1st to 10th	Night	40% 5% 10% 17% 13% 14%	2160
	11th to 20th	Night	38% 7% 11% 18% 17% 9%	2098
	21st to end	Night	36% 7% 10% 18% 19% 10%	1772
March	1st to 10th	Night	35% 6% 14% 21% 15% 8%	1980
	11th to 20th	Night	38% 8% 14% 15% 15% 10%	1980
	21st to end	Night	33% 7% 15% 20% 16% 9%	2178
April	1st to 10th	Night	36% 8% 16% 20% 13% 6%	1980
	11th to 20th	Night	38% 8% 14% 19% 14% 8%	1953
	21st to end	Night	40% 8% 11% 18% 15% 8%	1891
May	1st to 10th	Night	34% 11% 16% 18% 14% 6%	1620
	11th to 20th	Night	35% 9% 17% 23% 13% 2	1594
	21st to end	Night	26% 10% 20% 28% 15% 1	1746
June	1st to 10th	Night	19% 7% 20% 31% 21% 2	1620
	11th to 20th	Night	20% 8% 13% 36% 21% 3	1620
	21st to end	Night	25% 10% 23% 28% 12% 1	1620
July	1st to 10th	Night	31% 10% 24% 28% 6%	1575
	11th to 20th	Night	17% 8% 29% 35% 11%	1566
	21st to end	Night	14% 7% 32% 37% 10%	1728
August	1st to 10th	Night	11% 7% 31% 43% 9%	1779
	11th to 20th	Night	17% 9% 31% 37% 6%	1778
	21st to end	Night	24% 11% 26% 31% 7% 2	2125
September	1st to 10th	Night	29% 12% 22% 25% 11% 1	1980
	11th to 20th	Night	33% 11% 21% 24% 10% 2	1980
	21st to end	Night	28% 9% 18% 26% 14% 5%	1980
October	1st to 10th	Night	21% 7% 15% 28% 22% 7%	1980
	11th to 20th	Night	29% 8% 13% 22% 16% 12%	2006
	21st to end	Night	24% 5% 8% 23% 24% 15%	2376
November	1st to 10th	Night	28% 5% 13% 21% 25% 7%	2220
	11th to 20th	Night	38% 6% 11% 19% 17% 9%	2280
	21st to end	Night	38% 4 12% 20% 16% 10%	2441
December	1st to 10th	Night	39% 6% 11% 20% 17% 8%	2470
	11th to 20th	Night	39% 6% 9% 18% 13% 16%	3037
	21st to end	Night	40% 7% 10% 15% 18% 11%	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	18% 9% 27% 29% 14% 4	270
	11th to 20th	Day	19% 6% 27% 35% 11% 3	245
	21st to end	Day	20% 5% 39% 24% 11% 2	264
February	1st to 10th	Day	19% 6% 28% 29% 18% 1	240
	11th to 20th	Day	18% 6% 36% 30% 9% 1	240
	21st to end	Day	16% 6% 37% 34% 7% 1	198
March	1st to 10th	Day	15% 7% 32% 33% 13%	240
	11th to 20th	Day	17% 5% 37% 31% 10%	240
	21st to end	Day	11% 9% 35% 40% 5%	264
April	1st to 10th	Day	15% 5% 34% 33% 11% 1	240
	11th to 20th	Day	9% 8% 31% 34% 16% 3	234
	21st to end	Day	9% 8% 38% 34% 10% 1	318
May	1st to 10th	Day	9% 6% 39% 32% 13% 1	603
	11th to 20th	Day	10% 5% 37% 36% 11% 1	625
	21st to end	Day	4 3 32% 42% 17% 2	679
June	1st to 10th	Day	2 2 15% 42% 33% 7%	630
	11th to 20th	Day	3 1 12% 51% 27% 6%	630
	21st to end	Day	8% 1 10% 42% 27% 12%	630
July	1st to 10th	Day	7% 2 9% 38% 35% 9%	621
	11th to 20th	Day	3 1 5% 39% 42% 10%	618
	21st to end	Day	4 1 4 44% 37% 10%	620
August	1st to 10th	Day	1 5% 48% 34% 12%	447
	11th to 20th	Day	3 4 43% 35% 15%	437
	21st to end	Day	3 1 3 25% 37% 29%	347
September	1st to 10th	Day	10% 2 3 19% 45% 20%	270
	11th to 20th	Day	4 1 4 19% 33% 38%	270
	21st to end	Day	5% 1 8% 17% 43% 27%	270
October	1st to 10th	Day	6% 3 6% 20% 37% 27%	270
	11th to 20th	Day	11% 2 9% 21% 39% 17%	270
	21st to end	Day	14% 4 16% 35% 24% 8%	297
November	1st to 10th	Day	13% 3 10% 33% 33% 7%	270
	11th to 20th	Day	24% 4 13% 20% 28% 10%	270
	21st to end	Day	23% 7% 25% 20% 15% 10%	270
December	1st to 10th	Day	21% 3 21% 23% 24% 9%	270
	11th to 20th	Day	19% 7% 23% 29% 17% 6%	270
	21st to end	Day	21% 6% 20% 36% 14% 4	297
January	1st to 10th	Night	21% 6% 26% 34% 13%	950
	11th to 20th	Night	20% 6% 26% 39% 9%	811
	21st to end	Night	20% 5% 28% 38% 9% 1	792
February	1st to 10th	Night	21% 4 35% 33% 7%	720
	11th to 20th	Night	20% 6% 37% 32% 5%	704
	21st to end	Night	19% 6% 46% 23% 7%	588
March	1st to 10th	Night	17% 8% 37% 33% 4	540
	11th to 20th	Night	13% 8% 44% 30% 5%	540
	21st to end	Night	12% 8% 49% 28% 3	594
April	1st to 10th	Night	13% 6% 46% 31% 4	540
	11th to 20th	Night	13% 7% 43% 33% 4	533
	21st to end	Night	13% 8% 44% 31% 3	540
May	1st to 10th	Night	9% 8% 51% 29% 4	540
	11th to 20th	Night	9% 5% 40% 41% 4	531
	21st to end	Night	5% 4 34% 46% 11% 1	584
June	1st to 10th	Night	3 2 15% 56% 23% 1	540
	11th to 20th	Night	4 1 18% 60% 16% 1	540
	21st to end	Night	5% 2 14% 49% 28% 1	540
July	1st to 10th	Night	8% 2 11% 53% 25% 1	525
	11th to 20th	Night	3 1 8% 56% 31% 1	522
	21st to end	Night	4 1 6% 59% 30% 2	591
August	1st to 10th	Night	1 6% 58% 34% 1	537
	11th to 20th	Night	2 6% 53% 35% 3	534
	21st to end	Night	6% 6% 38% 46% 5%	594
September	1st to 10th	Night	9% 1 3 36% 45% 6%	540
	11th to 20th	Night	12% 1 5% 30% 47% 6%	540
	21st to end	Night	8% 1 7% 35% 42% 6%	540
October	1st to 10th	Night	3 2 8% 39% 42% 6%	540
	11th to 20th	Night	11% 2 13% 43% 29% 2	566
	21st to end	Night	9% 3 21% 43% 22% 1	792
November	1st to 10th	Night	10% 4 17% 44% 23% 2	740
	11th to 20th	Night	17% 3 20% 38% 21% 1	760
	21st to end	Night	19% 4 23% 37% 15% 1	921
December	1st to 10th	Night	17% 5% 24% 37% 16% 1	950
	11th to 20th	Night	21% 6% 26% 33% 14%	950
	21st to end	Night	18% 6% 26% 38% 12%	1045

Page generated at 2024-01-09 15:24:24. Version ac07

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