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 2024-11-05.

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	32% 7% 14% 23% 16% 7%	104720
	Night	32% 7% 16% 22% 15% 8%	102550
Seeing	Day	9% 4 19% 34% 24% 9%	14273
	Night	12% 4 24% 39% 18% 1	24276

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	35% 6% 8% 17% 21% 14%	2848
	11th to 20th	Day	36% 5% 7% 20% 20% 12%	3046
	21st to end	Day	45% 6% 9% 15% 18% 7%	3487
February	1st to 10th	Day	41% 4 8% 16% 18% 13%	1900
	11th to 20th	Day	36% 5% 9% 20% 19% 10%	1859
	21st to end	Day	36% 4 10% 20% 19% 10%	1572
March	1st to 10th	Day	41% 9% 12% 21% 11% 6%	3436
	11th to 20th	Day	52% 7% 9% 13% 13% 6%	3480
	21st to end	Day	23% 6% 11% 25% 19% 17%	3814
April	1st to 10th	Day	34% 6% 12% 21% 17% 10%	2090
	11th to 20th	Day	36% 8% 12% 20% 16% 8%	2066
	21st to end	Day	33% 7% 12% 19% 19% 10%	2173
May	1st to 10th	Day	31% 10% 18% 24% 11% 6%	4120
	11th to 20th	Day	30% 10% 16% 22% 15% 7%	4086
	21st to end	Day	22% 7% 11% 39% 19% 2	4489
June	1st to 10th	Day	22% 8% 13% 31% 22% 4	2470
	11th to 20th	Day	24% 7% 15% 24% 25% 5%	2470
	21st to end	Day	31% 10% 18% 28% 12% 2	2470
July	1st to 10th	Day	32% 9% 20% 32% 7%	4056
	11th to 20th	Day	36% 9% 25% 19% 10% 1	4051
	21st to end	Day	34% 8% 22% 28% 7%	4211
August	1st to 10th	Day	11% 5% 19% 47% 18% 1	3772
	11th to 20th	Day	21% 9% 34% 29% 6%	3762
	21st to end	Day	25% 9% 22% 31% 11% 1	3905
September	1st to 10th	Day	43% 10% 14% 18% 13% 2	2090
	11th to 20th	Day	43% 11% 16% 18% 9% 4	2090
	21st to end	Day	35% 9% 14% 22% 13% 7%	2090
October	1st to 10th	Day	24% 6% 7% 13% 27% 23%	3480
	11th to 20th	Day	25% 7% 9% 18% 22% 19%	3373
	21st to end	Day	22% 5% 7% 22% 31% 13%	3428
November	1st to 10th	Day	32% 7% 12% 21% 20% 7%	1898
	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	36% 5% 9% 16% 19% 16%	4108
	11th to 20th	Night	34% 5% 10% 18% 19% 14%	3951
	21st to end	Night	50% 6% 9% 12% 15% 8%	4180
February	1st to 10th	Night	39% 5% 10% 17% 13% 15%	2280
	11th to 20th	Night	39% 7% 10% 18% 17% 9%	2218
	21st to end	Night	35% 7% 11% 18% 20% 10%	1879
March	1st to 10th	Night	43% 7% 12% 21% 12% 5%	3419
	11th to 20th	Night	53% 10% 12% 11% 9% 6%	3480
	21st to end	Night	25% 5% 12% 25% 22% 12%	3817
April	1st to 10th	Night	36% 8% 16% 20% 13% 7%	2090
	11th to 20th	Night	39% 8% 14% 18% 14% 8%	2063
	21st to end	Night	41% 8% 12% 17% 14% 8%	1995
May	1st to 10th	Night	37% 12% 17% 20% 10% 4	2850
	11th to 20th	Night	39% 11% 16% 21% 10% 3	2824
	21st to end	Night	28% 10% 17% 34% 9% 1	3099
June	1st to 10th	Night	19% 7% 20% 32% 20% 2	1710
	11th to 20th	Night	20% 8% 12% 35% 23% 3	1710
	21st to end	Night	25% 10% 24% 28% 12% 1	1710
July	1st to 10th	Night	29% 9% 28% 30% 4	2805
	11th to 20th	Night	35% 9% 30% 21% 6%	2796
	21st to end	Night	29% 8% 30% 28% 6%	3107
August	1st to 10th	Night	6% 5% 25% 54% 10%	3144
	11th to 20th	Night	20% 9% 40% 28% 4	3143
	21st to end	Night	16% 9% 31% 33% 10% 1	3749
September	1st to 10th	Night	31% 12% 21% 24% 10% 2	2090
	11th to 20th	Night	33% 10% 20% 25% 10% 2	2090
	21st to end	Night	27% 9% 17% 28% 14% 6%	2090
October	1st to 10th	Night	17% 5% 9% 18% 26% 25%	3480
	11th to 20th	Night	24% 6% 10% 19% 25% 17%	3513
	21st to end	Night	25% 5% 7% 22% 30% 11%	4120
November	1st to 10th	Night	28% 5% 13% 22% 24% 7%	2280
	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	17% 6% 29% 34% 10% 3	270
	21st to end	Day	20% 6% 37% 24% 12% 1	297
February	1st to 10th	Day	17% 9% 29% 28% 17% 1	270
	11th to 20th	Day	19% 7% 36% 29% 9% 1	270
	21st to end	Day	15% 6% 36% 36% 7% 1	225
March	1st to 10th	Day	14% 8% 33% 33% 12%	270
	11th to 20th	Day	19% 6% 36% 31% 9%	270
	21st to end	Day	10% 9% 37% 38% 5%	297
April	1st to 10th	Day	14% 7% 36% 31% 10% 1	270
	11th to 20th	Day	8% 10% 32% 33% 14% 2	264
	21st to end	Day	9% 8% 38% 34% 9% 1	353
May	1st to 10th	Day	9% 6% 40% 32% 12% 1	653
	11th to 20th	Day	10% 5% 37% 36% 12% 1	675
	21st to end	Day	4 3 32% 42% 17% 2	734
June	1st to 10th	Day	2 2 15% 41% 32% 7%	680
	11th to 20th	Day	3 2 12% 49% 27% 6%	680
	21st to end	Day	7% 1 10% 42% 28% 11%	680
July	1st to 10th	Day	6% 2 10% 37% 35% 9%	671
	11th to 20th	Day	4 1 5% 38% 42% 10%	668
	21st to end	Day	5% 1 5% 43% 37% 10%	671
August	1st to 10th	Day	1 5% 47% 33% 14%	487
	11th to 20th	Day	2 4 42% 36% 15%	477
	21st to end	Day	3 1 3 25% 37% 31%	382
September	1st to 10th	Day	12% 2 4 21% 41% 20%	300
	11th to 20th	Day	5% 1 4 18% 36% 36%	300
	21st to end	Day	4 1 7% 17% 41% 29%	300
October	1st to 10th	Day	6% 3 6% 20% 37% 27%	300
	11th to 20th	Day	11% 2 8% 23% 38% 18%	300
	21st to end	Day	13% 3 15% 33% 25% 10%	330
November	1st to 10th	Day	13% 3 11% 33% 32% 7%	282
	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	19% 7% 26% 39% 9%	846
	21st to end	Night	21% 5% 28% 37% 9%	836
February	1st to 10th	Night	20% 5% 36% 32% 6%	760
	11th to 20th	Night	20% 7% 37% 31% 5%	744
	21st to end	Night	18% 5% 46% 24% 7%	623
March	1st to 10th	Night	17% 9% 38% 32% 4	570
	11th to 20th	Night	13% 8% 45% 29% 5%	570
	21st to end	Night	11% 8% 50% 28% 3	627
April	1st to 10th	Night	12% 7% 47% 30% 3	570
	11th to 20th	Night	13% 7% 44% 31% 4	563
	21st to end	Night	14% 9% 44% 31% 3	570
May	1st to 10th	Night	9% 8% 51% 27% 4	570
	11th to 20th	Night	10% 6% 40% 40% 4	561
	21st to end	Night	5% 5% 35% 44% 11%	617
June	1st to 10th	Night	3 2 16% 56% 22% 1	570
	11th to 20th	Night	4 1 18% 60% 16% 1	570
	21st to end	Night	5% 2 14% 49% 28% 1	570
July	1st to 10th	Night	7% 2 11% 53% 26% 1	555
	11th to 20th	Night	4 1 7% 56% 31% 1	552
	21st to end	Night	5% 1 6% 58% 29% 2	624
August	1st to 10th	Night	1 5% 57% 35% 1	567
	11th to 20th	Night	2 1 6% 53% 35% 3	564
	21st to end	Night	5% 6% 37% 47% 5%	627
September	1st to 10th	Night	9% 1 3 36% 44% 6%	570
	11th to 20th	Night	11% 1 5% 30% 47% 6%	570
	21st to end	Night	8% 1 6% 35% 43% 6%	570
October	1st to 10th	Night	4 2 7% 39% 43% 5%	570
	11th to 20th	Night	11% 2 13% 43% 30% 2	598
	21st to end	Night	9% 3 21% 43% 23% 1	836
November	1st to 10th	Night	10% 4 18% 44% 22% 2	760
	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 2024-11-03 01:11:30. Version ac07

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