Matagorda Bay Nature Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Matagorda Bay Nature Park clear sky chart from 2005-11-06 to 2026-07-31.

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	12% 6% 2 7% 4 4 5% 4 6% 9% 41%	137889
	Night	13% 6% 2 6% 4 4 4 3 5% 8% 44%	135417
Transparency	Day	38% 8% 16% 21% 12% 6%	141577
	Night	37% 6% 14% 20% 15% 8%	139796
Seeing	Day	11% 3 12% 26% 33% 14%	16984
	Night	13% 4 15% 30% 30% 7%	26810

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% 10% 2 7% 4 4 4 3 4 5% 39%	5289
	11th to 20th	Day	15% 8% 3 6% 4 4 4 3 4 5% 45%	5310
	21st to end	Day	24% 10% 3 9% 3 4 4 3 5% 5% 30%	5812
February	1st to 10th	Day	18% 9% 4 8% 4 5% 3 3 4 5% 38%	2100
	11th to 20th	Day	20% 8% 4 6% 4 3 4 2 4 5% 37%	2049
	21st to end	Day	18% 9% 2 6% 4 3 3 3 5% 6% 41%	1903
March	1st to 10th	Day	16% 8% 3 8% 5% 4 5% 4 6% 7% 34%	5046
	11th to 20th	Day	14% 8% 3 7% 4 3 4 3 4 5% 45%	5090
	21st to end	Day	16% 7% 2 6% 5% 3 4 3 5% 7% 42%	5583
April	1st to 10th	Day	13% 8% 2 6% 4 4 5% 4 5% 8% 39%	2310
	11th to 20th	Day	14% 7% 2 7% 5% 3 4 4 6% 8% 38%	2378
	21st to end	Day	11% 6% 2 6% 5% 5% 4 5% 6% 6% 44%	2520
May	1st to 10th	Day	20% 8% 3 8% 5% 5% 5% 4 6% 8% 28%	7175
	11th to 20th	Day	9% 6% 2 7% 4 5% 5% 4 7% 9% 42%	7627
	21st to end	Day	9% 6% 3 8% 6% 6% 7% 6% 9% 10% 31%	8392
June	1st to 10th	Day	4 3 2 4 3 4 5% 5% 8% 13% 50%	2730
	11th to 20th	Day	6% 4 1 4 5% 5% 5% 5% 8% 13% 44%	2730
	21st to end	Day	5% 5% 2 4 4 6% 5% 7% 10% 12% 39%	2730
July	1st to 10th	Day	7% 6% 2 7% 6% 5% 6% 5% 8% 11% 39%	6030
	11th to 20th	Day	4 5% 2 9% 6% 6% 7% 6% 9% 13% 33%	6030
	21st to end	Day	8% 5% 2 6% 5% 4 6% 5% 8% 12% 39%	6553
August	1st to 10th	Day	2 1 1 2 2 2 4 3 6% 10% 65%	4234
	11th to 20th	Day	3 2 1 3 3 4 5% 6% 10% 15% 48%	4018
	21st to end	Day	5% 3 2 6% 5% 6% 7% 5% 9% 13% 40%	4015
September	1st to 10th	Day	8% 5% 2 7% 5% 6% 7% 6% 8% 11% 34%	2200
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 5% 6% 9% 41%	2200
	21st to end	Day	8% 5% 2 6% 4 4 4 4 7% 9% 46%	2200
October	1st to 10th	Day	5% 3 2 4 3 4 4 4 6% 9% 57%	2130
	11th to 20th	Day	10% 5% 2 5% 4 3 4 3 4 7% 55%	2000
	21st to end	Day	10% 5% 2 5% 3 4 3 3 4 5% 56%	2200
November	1st to 10th	Day	10% 5% 2 6% 4 5% 5% 4 6% 8% 44%	2058
	11th to 20th	Day	14% 5% 2 5% 4 4 4 4 4 6% 48%	2100
	21st to end	Day	17% 8% 2 7% 4 4 4 3 4 6% 40%	2049
December	1st to 10th	Day	26% 10% 3 8% 5% 3 4 2 4 5% 31%	3030
	11th to 20th	Day	10% 6% 2 7% 5% 5% 5% 4 6% 7% 43%	3481
	21st to end	Day	15% 6% 3 7% 4 3 4 3 5% 6% 43%	4587
January	1st to 10th	Night	17% 8% 3 8% 4 4 4 3 4 5% 42%	7634
	11th to 20th	Night	14% 8% 3 7% 4 4 3 2 4 5% 46%	7680
	21st to end	Night	25% 8% 3 9% 4 4 3 2 5% 7% 30%	8402
February	1st to 10th	Night	16% 8% 3 7% 4 4 3 3 4 5% 42%	2537
	11th to 20th	Night	19% 8% 2 5% 4 3 4 2 4 6% 43%	2457
	21st to end	Night	17% 9% 3 6% 4 3 4 3 4 5% 42%	1903
March	1st to 10th	Night	19% 8% 3 6% 3 4 4 3 5% 6% 38%	5029
	11th to 20th	Night	13% 9% 2 6% 4 4 4 3 4 5% 47%	5090
	21st to end	Night	15% 7% 2 5% 4 3 3 3 4 6% 48%	5588
April	1st to 10th	Night	14% 9% 3 6% 4 3 4 4 5% 8% 39%	2310
	11th to 20th	Night	14% 7% 2 6% 4 4 3 3 5% 7% 46%	2188
	21st to end	Night	13% 7% 2 6% 4 4 4 4 6% 8% 42%	2100
May	1st to 10th	Night	23% 9% 3 7% 4 4 4 3 5% 7% 29%	5668
	11th to 20th	Night	12% 5% 2 5% 4 4 4 4 6% 10% 44%	5265
	21st to end	Night	10% 7% 2 7% 6% 5% 6% 5% 8% 11% 33%	5793
June	1st to 10th	Night	5% 3 1 4 5% 3 5% 4 7% 12% 52%	1890
	11th to 20th	Night	6% 4 1 5% 4 4 5% 4 8% 12% 48%	1890
	21st to end	Night	6% 4 2 5% 5% 4 7% 5% 8% 12% 43%	1890
July	1st to 10th	Night	6% 5% 2 7% 5% 5% 5% 4 6% 11% 44%	4168
	11th to 20th	Night	2 3 2 5% 5% 5% 6% 6% 9% 14% 44%	4167
	21st to end	Night	5% 5% 2 6% 4 5% 5% 5% 8% 12% 44%	4539
August	1st to 10th	Night	1 1 2 2 3 2 5% 8% 75%	2926
	11th to 20th	Night	2 2 1 3 3 3 4 4 8% 13% 56%	3032
	21st to end	Night	4 2 1 4 4 4 5% 4 8% 13% 53%	3876
September	1st to 10th	Night	6% 5% 3 7% 4 5% 6% 5% 8% 11% 41%	2200
	11th to 20th	Night	10% 7% 2 6% 4 4 4 5% 6% 9% 43%	2200
	21st to end	Night	7% 5% 2 5% 4 4 5% 4 6% 9% 49%	2200
October	1st to 10th	Night	4 4 2 5% 4 4 5% 4 5% 8% 56%	2250
	11th to 20th	Night	7% 4 2 4 3 3 3 3 4 6% 61%	2400
	21st to end	Night	9% 4 2 4 3 3 3 2 4 6% 61%	2640
November	1st to 10th	Night	8% 4 2 5% 4 4 4 4 5% 7% 53%	2460
	11th to 20th	Night	13% 6% 2 5% 4 4 3 3 4 6% 50%	2520
	21st to end	Night	14% 6% 2 6% 4 4 4 3 5% 6% 44%	2566
December	1st to 10th	Night	27% 10% 3 8% 3 4 3 2 4 5% 29%	4380
	11th to 20th	Night	11% 7% 3 6% 5% 4 4 3 6% 7% 44%	4946
	21st to end	Night	13% 6% 3 7% 4 4 4 3 5% 6% 47%	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	47% 6% 10% 20% 10% 7%	5290
	11th to 20th	Day	40% 6% 9% 17% 17% 11%	5310
	21st to end	Day	56% 5% 6% 11% 15% 7%	5812
February	1st to 10th	Day	50% 5% 8% 12% 15% 11%	2100
	11th to 20th	Day	48% 6% 9% 14% 15% 7%	2059
	21st to end	Day	43% 7% 12% 17% 15% 7%	1903
March	1st to 10th	Day	44% 10% 12% 15% 8% 11%	5046
	11th to 20th	Day	39% 9% 8% 14% 18% 13%	5090
	21st to end	Day	40% 7% 12% 20% 17% 5%	5585
April	1st to 10th	Day	41% 8% 12% 18% 12% 8%	2310
	11th to 20th	Day	42% 8% 13% 17% 13% 7%	2378
	21st to end	Day	37% 7% 14% 23% 13% 6%	2520
May	1st to 10th	Day	50% 8% 15% 16% 9% 2	7210
	11th to 20th	Day	35% 7% 18% 24% 12% 4	7631
	21st to end	Day	41% 10% 19% 26% 5%	8405
June	1st to 10th	Day	23% 9% 22% 33% 12%	2730
	11th to 20th	Day	28% 10% 19% 29% 13% 1	2730
	21st to end	Day	31% 12% 23% 28% 5%	2730
July	1st to 10th	Day	38% 7% 36% 17% 2	5966
	11th to 20th	Day	39% 8% 35% 15% 2	5961
	21st to end	Day	35% 9% 26% 24% 6%	6371
August	1st to 10th	Day	14% 7% 22% 49% 8%	4220
	11th to 20th	Day	21% 10% 40% 26% 3	4057
	21st to end	Day	32% 12% 25% 23% 8% 1	4014
September	1st to 10th	Day	39% 13% 18% 17% 12% 2	2200
	11th to 20th	Day	37% 11% 16% 22% 13% 2	2200
	21st to end	Day	31% 10% 14% 21% 17% 7%	2200
October	1st to 10th	Day	19% 5% 9% 17% 22% 28%	3468
	11th to 20th	Day	23% 5% 8% 25% 29% 10%	3240
	21st to end	Day	25% 4 7% 23% 30% 11%	3538
November	1st to 10th	Day	34% 8% 11% 21% 18% 7%	2058
	11th to 20th	Day	38% 6% 11% 18% 15% 12%	2100
	21st to end	Day	44% 6% 11% 17% 14% 8%	2049
December	1st to 10th	Day	57% 4 8% 14% 13% 3	3030
	11th to 20th	Day	37% 8% 9% 21% 15% 10%	3479
	21st to end	Day	40% 5% 9% 17% 18% 11%	4587
January	1st to 10th	Night	45% 5% 9% 16% 16% 9%	7635
	11th to 20th	Night	41% 4 6% 16% 22% 12%	7680
	21st to end	Night	55% 4 7% 12% 15% 8%	8402
February	1st to 10th	Night	44% 4 10% 11% 16% 14%	2537
	11th to 20th	Night	42% 6% 9% 16% 17% 10%	2457
	21st to end	Night	43% 6% 8% 16% 19% 8%	1903
March	1st to 10th	Night	44% 6% 11% 17% 11% 10%	5029
	11th to 20th	Night	39% 7% 8% 14% 17% 16%	5090
	21st to end	Night	37% 5% 10% 19% 21% 7%	5588
April	1st to 10th	Night	42% 6% 12% 17% 15% 8%	2310
	11th to 20th	Night	37% 6% 12% 19% 13% 12%	2188
	21st to end	Night	39% 6% 14% 21% 14% 6%	2100
May	1st to 10th	Night	53% 6% 13% 15% 10% 3	5698
	11th to 20th	Night	35% 7% 15% 26% 14% 4	5266
	21st to end	Night	40% 9% 22% 24% 6%	5805
June	1st to 10th	Night	24% 8% 21% 32% 15% 1	1890
	11th to 20th	Night	27% 7% 16% 33% 15% 2	1890
	21st to end	Night	30% 11% 24% 28% 8% 1	1890
July	1st to 10th	Night	35% 5% 35% 23% 2	4125
	11th to 20th	Night	28% 8% 38% 22% 3	4116
	21st to end	Night	31% 9% 27% 25% 7%	4410
August	1st to 10th	Night	8% 6% 18% 56% 12%	2916
	11th to 20th	Night	19% 7% 38% 33% 3	3059
	21st to end	Night	23% 11% 29% 27% 9% 1	3876
September	1st to 10th	Night	34% 11% 22% 19% 12% 3	2200
	11th to 20th	Night	36% 10% 14% 22% 16% 2	2200
	21st to end	Night	31% 9% 12% 24% 17% 7%	2200
October	1st to 10th	Night	20% 5% 9% 16% 19% 31%	3679
	11th to 20th	Night	17% 4 9% 26% 30% 14%	3899
	21st to end	Night	19% 4 7% 24% 33% 13%	4252
November	1st to 10th	Night	31% 7% 13% 20% 21% 8%	2460
	11th to 20th	Night	35% 5% 11% 19% 19% 11%	2520
	21st to end	Night	41% 6% 11% 18% 17% 8%	2566
December	1st to 10th	Night	58% 5% 8% 14% 11% 4	4380
	11th to 20th	Night	39% 5% 10% 18% 15% 13%	4947
	21st to end	Night	37% 6% 7% 17% 22% 11%	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	22% 7% 25% 31% 15% 1	330
	11th to 20th	Day	20% 9% 21% 35% 14%	330
	21st to end	Day	21% 9% 28% 31% 12%	363
February	1st to 10th	Day	22% 6% 25% 32% 14% 1	330
	11th to 20th	Day	26% 9% 21% 29% 14% 1	330
	21st to end	Day	20% 7% 22% 42% 9%	273
March	1st to 10th	Day	21% 7% 26% 36% 10%	330
	11th to 20th	Day	18% 8% 28% 33% 11% 2	330
	21st to end	Day	14% 7% 23% 38% 16% 2	363
April	1st to 10th	Day	15% 6% 34% 33% 12%	330
	11th to 20th	Day	17% 5% 27% 33% 16% 1	416
	21st to end	Day	14% 5% 22% 39% 19%	540
May	1st to 10th	Day	15% 6% 22% 41% 16% 1	594
	11th to 20th	Day	9% 4 16% 42% 26% 3	775
	21st to end	Day	7% 2 10% 42% 35% 3	844
June	1st to 10th	Day	6% 1 4 31% 48% 10%	780
	11th to 20th	Day	7% 1 4 26% 52% 10%	780
	21st to end	Day	7% 1 3 20% 50% 19%	780
July	1st to 10th	Day	7% 1 4 14% 47% 27%	771
	11th to 20th	Day	5% 1 1 6% 55% 32%	768
	21st to end	Day	6% 1 2 9% 52% 30%	845
August	1st to 10th	Day	2 1 1 10% 47% 40%	726
	11th to 20th	Day	4 1 1 6% 44% 44%	627
	21st to end	Day	7% 2 3 8% 39% 40%	403
September	1st to 10th	Day	9% 2 3 15% 41% 29%	330
	11th to 20th	Day	8% 2 16% 44% 29%	330
	21st to end	Day	7% 4 15% 53% 21%	330
October	1st to 10th	Day	5% 2 4 26% 49% 15%	330
	11th to 20th	Day	10% 1 7% 27% 40% 16%	330
	21st to end	Day	13% 4 16% 28% 33% 6%	363
November	1st to 10th	Day	11% 3 15% 29% 32% 9%	330
	11th to 20th	Day	17% 2 11% 34% 31% 5%	330
	21st to end	Day	18% 9% 22% 31% 16% 5%	330
December	1st to 10th	Day	21% 4 20% 33% 18% 4	330
	11th to 20th	Day	20% 8% 18% 35% 17% 2	330
	21st to end	Day	18% 4 20% 35% 20% 3	363
January	1st to 10th	Night	20% 7% 27% 31% 14% 1	1050
	11th to 20th	Night	18% 8% 27% 34% 13%	1050
	21st to end	Night	23% 6% 24% 37% 10%	1155
February	1st to 10th	Night	21% 6% 23% 37% 13%	857
	11th to 20th	Night	22% 9% 20% 35% 13%	823
	21st to end	Night	19% 10% 24% 37% 9%	519
March	1st to 10th	Night	22% 6% 22% 35% 15%	630
	11th to 20th	Night	16% 6% 23% 39% 15% 1	630
	21st to end	Night	14% 4 23% 40% 18% 2	693
April	1st to 10th	Night	17% 5% 24% 39% 14%	630
	11th to 20th	Night	16% 7% 23% 36% 17%	623
	21st to end	Night	15% 4 24% 40% 16%	630
May	1st to 10th	Night	16% 4 20% 44% 16%	630
	11th to 20th	Night	11% 3 15% 45% 24% 2	621
	21st to end	Night	6% 3 12% 39% 38% 2	683
June	1st to 10th	Night	4 1 4 29% 56% 6%	630
	11th to 20th	Night	6% 3 31% 54% 5%	630
	21st to end	Night	6% 1 4 23% 47% 19%	630
July	1st to 10th	Night	5% 2 3 16% 52% 22%	615
	11th to 20th	Night	3 1 1 10% 56% 29%	612
	21st to end	Night	3 1 1 11% 58% 25%	687
August	1st to 10th	Night	1 1 8% 58% 32%	597
	11th to 20th	Night	4 2 7% 60% 27%	594
	21st to end	Night	6% 2 10% 52% 30%	660
September	1st to 10th	Night	6% 1 4 13% 53% 24%	600
	11th to 20th	Night	12% 1 3 16% 51% 17%	600
	21st to end	Night	8% 5% 22% 51% 13%	600
October	1st to 10th	Night	4 1 7% 25% 51% 12%	650
	11th to 20th	Night	8% 2 11% 31% 41% 7%	800
	21st to end	Night	10% 3 16% 32% 34% 5%	880
November	1st to 10th	Night	9% 3 11% 32% 38% 7%	820
	11th to 20th	Night	15% 3 16% 34% 30% 3	840
	21st to end	Night	15% 4 21% 37% 20% 3	886
December	1st to 10th	Night	22% 5% 19% 31% 20% 3	1050
	11th to 20th	Night	18% 6% 22% 34% 19% 1	1050
	21st to end	Night	20% 8% 22% 32% 16% 2	1155

Page generated at 2026-07-28 02:25:23. Version ac07

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