Brazos Bend State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brazos Bend State Park clear sky chart from 2005-11-06 to 2026-08-15.

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	12% 6% 2 7% 5% 5% 5% 4 6% 8% 39%	143204
	Night	14% 7% 2 6% 4 4 4 3 5% 7% 45%	138990
Transparency	Day	41% 5% 13% 21% 14% 6%	146866
	Night	38% 4 13% 21% 16% 8%	143395
Seeing	Day	13% 7% 20% 27% 22% 11%	17175
	Night	15% 5% 20% 33% 24% 4	26945

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% 11% 3 6% 4 3 3 3 3 5% 41%	5289
	11th to 20th	Day	14% 6% 2 6% 3 3 3 2 4 6% 51%	5310
	21st to end	Day	26% 9% 3 8% 3 3 2 2 5% 6% 32%	5812
February	1st to 10th	Day	18% 9% 3 7% 4 4 4 3 5% 4 37%	2027
	11th to 20th	Day	21% 9% 3 6% 4 4 4 3 4 5% 36%	2065
	21st to end	Day	20% 9% 3 5% 4 4 4 3 4 5% 40%	1903
March	1st to 10th	Day	14% 7% 3 7% 5% 4 5% 4 6% 7% 38%	5046
	11th to 20th	Day	13% 6% 2 7% 5% 5% 4 3 4 5% 46%	5090
	21st to end	Day	16% 7% 3 7% 5% 4 4 3 5% 6% 41%	5583
April	1st to 10th	Day	14% 9% 2 7% 5% 4 5% 4 4 6% 38%	2310
	11th to 20th	Day	17% 8% 3 6% 5% 5% 5% 3 5% 8% 36%	2424
	21st to end	Day	10% 7% 3 8% 6% 6% 5% 4 5% 6% 40%	2520
May	1st to 10th	Day	19% 8% 3 8% 5% 5% 5% 4 6% 7% 31%	7140
	11th to 20th	Day	11% 6% 3 7% 5% 5% 5% 4 6% 7% 42%	7627
	21st to end	Day	10% 6% 3 8% 6% 6% 6% 5% 8% 10% 33%	8392
June	1st to 10th	Day	6% 4 2 7% 6% 7% 7% 6% 8% 9% 39%	2730
	11th to 20th	Day	6% 4 2 7% 6% 8% 6% 5% 9% 11% 37%	2730
	21st to end	Day	6% 5% 3 7% 7% 7% 9% 7% 9% 9% 31%	2730
July	1st to 10th	Day	6% 4 2 7% 6% 7% 7% 6% 9% 12% 34%	7680
	11th to 20th	Day	8% 7% 3 9% 7% 6% 7% 5% 8% 12% 29%	7680
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 4 7% 10% 42%	8337
August	1st to 10th	Day	2 2 1 4 4 5% 6% 5% 8% 11% 53%	4364
	11th to 20th	Day	3 2 1 5% 5% 6% 7% 6% 10% 13% 43%	4061
	21st to end	Day	7% 5% 2 8% 7% 6% 6% 6% 8% 10% 35%	4156
September	1st to 10th	Day	8% 6% 3 9% 7% 7% 7% 5% 7% 7% 34%	2200
	11th to 20th	Day	12% 7% 3 8% 6% 6% 6% 5% 6% 9% 33%	2200
	21st to end	Day	9% 6% 2 5% 5% 5% 5% 4 6% 9% 44%	2200
October	1st to 10th	Day	6% 5% 2 4 4 4 4 4 7% 6% 55%	2095
	11th to 20th	Day	9% 6% 2 5% 3 4 4 4 6% 6% 51%	2000
	21st to end	Day	11% 4 2 5% 4 4 3 4 4 6% 52%	2200
November	1st to 10th	Day	9% 7% 2 7% 5% 4 5% 4 6% 8% 43%	2058
	11th to 20th	Day	12% 6% 2 6% 5% 5% 3 3 5% 6% 46%	2100
	21st to end	Day	15% 8% 3 7% 5% 4 4 4 5% 6% 39%	2047
December	1st to 10th	Day	25% 9% 3 6% 4 3 3 3 4 7% 34%	3030
	11th to 20th	Day	12% 7% 2 7% 4 4 4 4 5% 8% 43%	3481
	21st to end	Day	14% 6% 2 7% 3 4 4 4 5% 6% 45%	4587
January	1st to 10th	Night	18% 7% 2 6% 4 4 4 2 4 5% 43%	7634
	11th to 20th	Night	13% 8% 3 6% 4 3 3 3 4 5% 49%	7680
	21st to end	Night	29% 9% 3 7% 4 3 3 2 4 6% 32%	8402
February	1st to 10th	Night	18% 9% 3 7% 4 3 4 3 4 6% 40%	2609
	11th to 20th	Night	20% 8% 3 6% 4 2 3 2 3 6% 43%	2440
	21st to end	Night	20% 8% 3 5% 4 4 3 3 4 5% 41%	1903
March	1st to 10th	Night	21% 10% 3 6% 3 4 3 3 4 6% 36%	5029
	11th to 20th	Night	17% 8% 3 5% 4 4 3 3 4 5% 46%	5090
	21st to end	Night	18% 10% 2 5% 4 3 3 3 4 5% 43%	5588
April	1st to 10th	Night	15% 7% 3 7% 5% 4 4 4 5% 7% 40%	2310
	11th to 20th	Night	18% 6% 2 6% 5% 3 3 2 5% 6% 44%	2143
	21st to end	Night	14% 7% 2 7% 5% 5% 5% 3 5% 7% 40%	2100
May	1st to 10th	Night	26% 11% 3 7% 4 5% 4 3 5% 6% 27%	5689
	11th to 20th	Night	15% 8% 3 7% 4 3 4 3 6% 8% 40%	5265
	21st to end	Night	15% 8% 3 8% 4 5% 5% 4 8% 10% 31%	5793
June	1st to 10th	Night	5% 3 2 5% 3 3 4 2 7% 11% 55%	1890
	11th to 20th	Night	6% 3 2 3 3 3 3 4 7% 11% 54%	1890
	21st to end	Night	5% 3 2 5% 4 5% 5% 6% 7% 11% 47%	1890
July	1st to 10th	Night	4 4 2 5% 4 4 4 4 7% 12% 51%	5308
	11th to 20th	Night	5% 5% 2 7% 5% 5% 5% 5% 7% 10% 44%	5307
	21st to end	Night	6% 4 2 5% 4 4 5% 4 6% 10% 51%	5770
August	1st to 10th	Night	1 1 1 1 2 2 3 4 9% 76%	3016
	11th to 20th	Night	2 2 1 2 2 3 3 3 6% 15% 60%	3078
	21st to end	Night	4 3 2 5% 4 4 4 5% 7% 11% 51%	3736
September	1st to 10th	Night	5% 4 2 6% 5% 5% 6% 4 7% 9% 47%	2200
	11th to 20th	Night	10% 6% 3 7% 4 4 4 3 5% 8% 46%	2200
	21st to end	Night	7% 4 2 5% 4 4 3 4 6% 8% 55%	2200
October	1st to 10th	Night	5% 4 1 4 3 3 3 3 5% 8% 61%	2284
	11th to 20th	Night	9% 3 1 3 2 2 3 2 5% 6% 63%	2400
	21st to end	Night	10% 5% 1 4 3 3 3 3 4 4 61%	2640
November	1st to 10th	Night	9% 4 1 6% 3 3 4 4 6% 6% 54%	2460
	11th to 20th	Night	12% 5% 2 5% 3 3 4 4 4 6% 51%	2520
	21st to end	Night	15% 7% 2 6% 4 4 4 3 5% 5% 45%	2567
December	1st to 10th	Night	24% 11% 3 7% 4 3 3 2 4 6% 31%	4380
	11th to 20th	Night	14% 7% 3 6% 4 4 4 4 4 5% 45%	4946
	21st to end	Night	15% 6% 2 6% 3 3 3 3 4 6% 48%	6633

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	48% 2 7% 20% 16% 7%	5290
	11th to 20th	Day	36% 2 5% 23% 20% 13%	5310
	21st to end	Day	56% 2 4 13% 16% 10%	5812
February	1st to 10th	Day	49% 4 6% 13% 15% 12%	2027
	11th to 20th	Day	51% 3 9% 14% 15% 8%	2075
	21st to end	Day	46% 4 8% 17% 17% 8%	1903
March	1st to 10th	Day	44% 5% 10% 18% 11% 13%	5046
	11th to 20th	Day	40% 5% 7% 9% 22% 17%	5090
	21st to end	Day	45% 3 8% 19% 20% 5%	5585
April	1st to 10th	Day	46% 6% 9% 17% 14% 9%	2310
	11th to 20th	Day	46% 4 10% 17% 14% 9%	2424
	21st to end	Day	44% 6% 9% 19% 17% 6%	2520
May	1st to 10th	Day	54% 4 9% 20% 11% 2	7175
	11th to 20th	Day	41% 4 12% 23% 17% 3	7631
	21st to end	Day	44% 5% 15% 29% 7% 1	8405
June	1st to 10th	Day	35% 9% 17% 24% 14% 1	2730
	11th to 20th	Day	36% 9% 14% 26% 14% 1	2730
	21st to end	Day	41% 10% 17% 23% 9%	2730
July	1st to 10th	Day	39% 4 36% 20% 2	7616
	11th to 20th	Day	47% 5% 29% 16% 4	7611
	21st to end	Day	36% 6% 18% 34% 6%	8155
August	1st to 10th	Day	23% 7% 15% 43% 12%	4350
	11th to 20th	Day	28% 8% 32% 28% 4	4100
	21st to end	Day	43% 8% 16% 22% 11% 1	4155
September	1st to 10th	Day	45% 10% 14% 15% 13% 4	2200
	11th to 20th	Day	46% 8% 12% 19% 13% 3	2200
	21st to end	Day	37% 6% 13% 18% 16% 10%	2200
October	1st to 10th	Day	23% 3 6% 16% 17% 36%	3407
	11th to 20th	Day	25% 3 6% 19% 35% 12%	3240
	21st to end	Day	29% 3 5% 18% 33% 12%	3538
November	1st to 10th	Day	37% 5% 10% 19% 20% 8%	2058
	11th to 20th	Day	40% 4 8% 16% 20% 13%	2100
	21st to end	Day	45% 6% 8% 15% 16% 10%	2047
December	1st to 10th	Day	53% 3 7% 17% 17% 4	3030
	11th to 20th	Day	40% 3 7% 20% 19% 10%	3479
	21st to end	Day	40% 4 5% 18% 20% 12%	4587
January	1st to 10th	Night	44% 3 9% 17% 17% 10%	7635
	11th to 20th	Night	40% 2 4 18% 22% 14%	7680
	21st to end	Night	56% 2 5% 13% 16% 9%	8402
February	1st to 10th	Night	47% 4 8% 10% 18% 13%	2609
	11th to 20th	Night	44% 4 8% 16% 17% 12%	2440
	21st to end	Night	46% 5% 7% 14% 19% 9%	1903
March	1st to 10th	Night	50% 4 7% 15% 14% 10%	5029
	11th to 20th	Night	43% 4 7% 13% 17% 16%	5090
	21st to end	Night	44% 4 8% 15% 21% 8%	5588
April	1st to 10th	Night	44% 5% 10% 18% 14% 9%	2310
	11th to 20th	Night	41% 4 10% 19% 14% 12%	2143
	21st to end	Night	44% 5% 11% 20% 14% 7%	2100
May	1st to 10th	Night	59% 4 8% 16% 10% 3	5719
	11th to 20th	Night	43% 4 10% 25% 14% 4	5266
	21st to end	Night	47% 6% 19% 22% 5%	5805
June	1st to 10th	Night	24% 7% 21% 30% 18%	1890
	11th to 20th	Night	24% 6% 19% 32% 17% 2	1890
	21st to end	Night	29% 10% 24% 26% 11%	1890
July	1st to 10th	Night	27% 3 40% 27% 2	5265
	11th to 20th	Night	36% 5% 32% 22% 5%	5256
	21st to end	Night	30% 5% 22% 35% 8%	5641
August	1st to 10th	Night	9% 3 20% 53% 14%	3006
	11th to 20th	Night	16% 6% 36% 37% 4 1	3105
	21st to end	Night	27% 11% 24% 27% 9% 1	3736
September	1st to 10th	Night	33% 9% 22% 20% 12% 4	2200
	11th to 20th	Night	36% 7% 14% 24% 16% 3	2200
	21st to end	Night	27% 6% 15% 24% 19% 9%	2200
October	1st to 10th	Night	18% 3 7% 18% 19% 35%	3739
	11th to 20th	Night	16% 3 7% 24% 34% 16%	3899
	21st to end	Night	21% 2 5% 19% 35% 17%	4252
November	1st to 10th	Night	30% 5% 12% 21% 22% 10%	2460
	11th to 20th	Night	33% 5% 10% 19% 19% 13%	2520
	21st to end	Night	41% 5% 9% 20% 17% 9%	2567
December	1st to 10th	Night	56% 3 6% 16% 14% 5%	4380
	11th to 20th	Night	42% 4 9% 14% 17% 14%	4947
	21st to end	Night	40% 3 6% 15% 26% 10%	6633

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	28% 11% 33% 21% 6% 2	330
	11th to 20th	Day	24% 12% 32% 24% 7% 1	330
	21st to end	Day	23% 19% 28% 22% 7%	363
February	1st to 10th	Day	21% 16% 33% 24% 6%	330
	11th to 20th	Day	28% 13% 32% 20% 7% 1	330
	21st to end	Day	26% 13% 41% 16% 4	273
March	1st to 10th	Day	23% 16% 37% 18% 5%	330
	11th to 20th	Day	16% 18% 41% 18% 5% 2	330
	21st to end	Day	17% 15% 32% 23% 10% 2	363
April	1st to 10th	Day	22% 18% 34% 20% 6%	330
	11th to 20th	Day	22% 14% 31% 23% 10% 1	462
	21st to end	Day	16% 10% 35% 27% 11% 1	540
May	1st to 10th	Day	20% 8% 34% 24% 12% 1	585
	11th to 20th	Day	14% 8% 30% 31% 13% 3	775
	21st to end	Day	11% 4 26% 38% 18% 3	844
June	1st to 10th	Day	8% 2 14% 34% 30% 11%	780
	11th to 20th	Day	7% 2 15% 38% 30% 9%	780
	21st to end	Day	8% 2 10% 32% 32% 15%	780
July	1st to 10th	Day	9% 1 7% 29% 32% 22%	771
	11th to 20th	Day	6% 1 2 30% 35% 26%	768
	21st to end	Day	8% 1 4 28% 36% 23%	849
August	1st to 10th	Day	3 1 3 26% 39% 29%	776
	11th to 20th	Day	4 1 2 18% 41% 33%	638
	21st to end	Day	9% 2 7% 17% 33% 32%	492
September	1st to 10th	Day	12% 1 8% 26% 32% 21%	330
	11th to 20th	Day	9% 2 9% 28% 30% 22%	330
	21st to end	Day	8% 1 8% 31% 35% 16%	330
October	1st to 10th	Day	8% 3 9% 40% 32% 8%	330
	11th to 20th	Day	10% 4 15% 38% 23% 10%	330
	21st to end	Day	18% 7% 25% 26% 19% 6%	363
November	1st to 10th	Day	15% 6% 22% 34% 19% 4	330
	11th to 20th	Day	15% 7% 25% 34% 14% 4	330
	21st to end	Day	17% 16% 33% 20% 11% 3	330
December	1st to 10th	Day	22% 7% 33% 24% 9% 6%	330
	11th to 20th	Day	18% 14% 33% 25% 8% 2	330
	21st to end	Day	17% 9% 38% 24% 10% 2	363
January	1st to 10th	Night	21% 9% 30% 31% 9%	1050
	11th to 20th	Night	20% 10% 28% 33% 8% 1	1050
	21st to end	Night	24% 8% 27% 33% 7%	1155
February	1st to 10th	Night	23% 10% 29% 32% 6%	929
	11th to 20th	Night	25% 10% 26% 32% 7%	806
	21st to end	Night	24% 11% 34% 26% 6%	519
March	1st to 10th	Night	24% 8% 30% 31% 7%	630
	11th to 20th	Night	19% 9% 30% 33% 9%	630
	21st to end	Night	18% 7% 28% 35% 11% 1	693
April	1st to 10th	Night	17% 9% 32% 36% 6%	630
	11th to 20th	Night	20% 10% 26% 34% 10%	623
	21st to end	Night	18% 8% 28% 36% 10%	630
May	1st to 10th	Night	18% 5% 30% 38% 9%	630
	11th to 20th	Night	13% 3 24% 44% 14% 1	621
	21st to end	Night	9% 4 21% 42% 23% 1	683
June	1st to 10th	Night	5% 2 9% 41% 41% 2	630
	11th to 20th	Night	6% 1 9% 47% 34% 4	630
	21st to end	Night	6% 1 9% 30% 46% 9%	630
July	1st to 10th	Night	7% 3 27% 52% 11%	615
	11th to 20th	Night	4 1 22% 60% 12%	612
	21st to end	Night	4 1 3 24% 57% 11%	690
August	1st to 10th	Night	1 1 1 22% 65% 11%	627
	11th to 20th	Night	3 1 18% 66% 11%	606
	21st to end	Night	6% 1 3 19% 55% 16%	660
September	1st to 10th	Night	6% 2 5% 22% 51% 15%	600
	11th to 20th	Night	12% 1 4 24% 48% 10%	600
	21st to end	Night	8% 1 6% 29% 49% 8%	600
October	1st to 10th	Night	5% 2 8% 35% 43% 7%	684
	11th to 20th	Night	9% 2 19% 40% 28% 3	800
	21st to end	Night	11% 6% 18% 38% 24% 3	880
November	1st to 10th	Night	11% 3 18% 39% 26% 3	820
	11th to 20th	Night	14% 4 21% 40% 20%	840
	21st to end	Night	18% 7% 26% 33% 15% 2	887
December	1st to 10th	Night	23% 5% 24% 30% 16% 1	1050
	11th to 20th	Night	19% 8% 26% 35% 11% 1	1050
	21st to end	Night	22% 7% 29% 32% 10% 1	1155

Page generated at 2026-08-12 02:37:19. Version ac07

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