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 2025-03-27.

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 6% 4 4 5% 4 6% 9% 40%	109370
	Night	13% 6% 2 6% 4 4 4 4 5% 8% 44%	110172
Transparency	Day	37% 8% 16% 21% 12% 6%	113097
	Night	36% 7% 14% 20% 15% 8%	114572
Seeing	Day	11% 4 12% 27% 33% 13%	15093
	Night	13% 4 16% 30% 30% 7%	25138

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	21% 10% 3 7% 5% 4 4 3 4 5% 33%	4077
	11th to 20th	Day	17% 7% 3 5% 4 4 4 3 5% 6% 43%	4080
	21st to end	Day	26% 9% 3 7% 3 4 4 3 5% 5% 31%	4488
February	1st to 10th	Day	19% 9% 4 8% 5% 5% 3 3 4 5% 36%	2000
	11th to 20th	Day	20% 8% 4 6% 4 3 4 2 4 5% 37%	1949
	21st to end	Day	19% 9% 3 6% 4 3 3 3 5% 6% 40%	1815
March	1st to 10th	Day	18% 10% 4 9% 5% 4 6% 4 7% 7% 27%	3546
	11th to 20th	Day	18% 10% 3 9% 5% 4 5% 4 5% 6% 31%	3590
	21st to end	Day	13% 5% 2 5% 5% 3 4 3 5% 7% 48%	3880
April	1st to 10th	Day	14% 9% 2 6% 4 4 5% 4 5% 8% 39%	2090
	11th to 20th	Day	14% 7% 2 7% 5% 3 4 5% 6% 7% 38%	2149
	21st to end	Day	11% 6% 2 5% 5% 4 4 5% 5% 6% 47%	2280
May	1st to 10th	Day	16% 7% 3 8% 5% 5% 6% 4 5% 8% 32%	3850
	11th to 20th	Day	12% 7% 3 8% 4 5% 5% 4 7% 8% 39%	4082
	21st to end	Day	6% 5% 2 6% 5% 5% 7% 6% 9% 11% 38%	4477
June	1st to 10th	Day	4 3 1 4 3 4 5% 5% 8% 12% 51%	2470
	11th to 20th	Day	6% 3 1 4 5% 5% 5% 5% 8% 13% 45%	2470
	21st to end	Day	6% 5% 2 5% 4 6% 5% 7% 11% 12% 37%	2470
July	1st to 10th	Day	8% 6% 2 5% 5% 4 5% 5% 7% 11% 41%	4120
	11th to 20th	Day	5% 6% 3 11% 7% 7% 7% 6% 9% 11% 28%	4120
	21st to end	Day	10% 7% 2 6% 6% 5% 6% 5% 9% 13% 32%	4465
August	1st to 10th	Day	2 1 1 2 2 2 4 3 6% 10% 66%	4104
	11th to 20th	Day	3 2 1 3 3 4 5% 6% 10% 15% 47%	3893
	21st to end	Day	5% 3 2 6% 5% 6% 7% 5% 8% 13% 40%	3892
September	1st to 10th	Day	8% 5% 2 7% 5% 6% 7% 6% 8% 11% 33%	2090
	11th to 20th	Day	12% 5% 2 6% 5% 5% 5% 5% 6% 9% 39%	2090
	21st to end	Day	8% 5% 3 7% 4 4 4 4 8% 9% 45%	2090
October	1st to 10th	Day	5% 3 2 5% 4 4 4 4 6% 9% 56%	2024
	11th to 20th	Day	10% 5% 2 5% 4 3 4 3 4 6% 54%	1900
	21st to end	Day	11% 5% 2 5% 3 4 3 3 4 5% 55%	2090
November	1st to 10th	Day	10% 6% 2 7% 4 5% 6% 5% 6% 8% 42%	1958
	11th to 20th	Day	15% 5% 2 5% 4 4 4 4 4 6% 47%	2000
	21st to end	Day	17% 8% 2 7% 4 4 4 3 4 6% 40%	1952
December	1st to 10th	Day	26% 10% 3 8% 5% 3 4 2 4 5% 31%	2940
	11th to 20th	Day	10% 6% 2 7% 5% 5% 5% 4 6% 8% 43%	3391
	21st to end	Day	15% 6% 3 7% 4 3 4 3 5% 6% 43%	4488
January	1st to 10th	Night	20% 9% 3 8% 4 4 4 3 4 5% 36%	5888
	11th to 20th	Night	16% 8% 3 6% 4 3 3 3 4 6% 45%	5900
	21st to end	Night	25% 9% 3 7% 4 4 3 3 5% 7% 30%	6490
February	1st to 10th	Night	16% 8% 3 7% 4 4 3 3 4 5% 41%	2416
	11th to 20th	Night	19% 8% 2 4 4 3 4 3 4 6% 43%	2337
	21st to end	Night	17% 9% 3 6% 4 3 4 3 4 5% 41%	1815
March	1st to 10th	Night	22% 9% 3 6% 3 4 4 3 6% 7% 33%	3529
	11th to 20th	Night	17% 11% 3 8% 5% 5% 5% 4 5% 7% 30%	3590
	21st to end	Night	10% 6% 2 5% 4 3 4 3 5% 7% 52%	3889
April	1st to 10th	Night	13% 9% 3 6% 4 3 4 5% 6% 9% 39%	2090
	11th to 20th	Night	15% 7% 2 6% 4 4 4 3 4 7% 45%	1978
	21st to end	Night	13% 7% 2 6% 4 4 4 3 5% 8% 44%	1900
May	1st to 10th	Night	22% 7% 2 6% 4 3 4 3 5% 8% 35%	3043
	11th to 20th	Night	11% 7% 3 6% 4 4 4 4 6% 9% 42%	2823
	21st to end	Night	9% 6% 2 6% 4 4 6% 5% 8% 12% 39%	3090
June	1st to 10th	Night	5% 3 1 4 4 3 4 4 6% 11% 54%	1710
	11th to 20th	Night	5% 4 1 5% 4 4 5% 4 8% 12% 48%	1710
	21st to end	Night	6% 4 1 6% 4 4 7% 5% 8% 12% 43%	1710
July	1st to 10th	Night	7% 5% 2 5% 4 4 4 4 6% 10% 49%	2850
	11th to 20th	Night	2 3 2 6% 6% 6% 7% 6% 10% 14% 38%	2850
	21st to end	Night	7% 6% 2 6% 5% 5% 5% 5% 8% 14% 37%	3098
August	1st to 10th	Night	1 1 2 2 3 2 5% 8% 75%	2836
	11th to 20th	Night	2 2 1 4 3 4 4 4 8% 13% 55%	2938
	21st to end	Night	4 2 1 4 4 4 5% 4 7% 13% 53%	3757
September	1st to 10th	Night	6% 5% 2 7% 5% 5% 6% 4 8% 11% 41%	2090
	11th to 20th	Night	11% 7% 2 6% 4 4 4 4 7% 9% 42%	2090
	21st to end	Night	8% 5% 2 6% 4 4 4 4 6% 9% 49%	2090
October	1st to 10th	Night	4 4 2 5% 4 4 5% 4 6% 8% 55%	2137
	11th to 20th	Night	8% 4 2 4 3 3 3 3 4 6% 60%	2280
	21st to end	Night	9% 4 2 4 3 3 3 3 4 6% 60%	2508
November	1st to 10th	Night	9% 4 2 5% 4 4 5% 4 5% 7% 51%	2340
	11th to 20th	Night	14% 6% 2 5% 4 4 4 3 4 6% 49%	2400
	21st to end	Night	14% 6% 3 6% 4 4 4 3 5% 6% 45%	2444
December	1st to 10th	Night	27% 10% 3 8% 4 4 3 2 4 5% 29%	4250
	11th to 20th	Night	11% 7% 3 7% 5% 4 4 3 6% 7% 43%	4816
	21st to end	Night	13% 6% 3 7% 4 4 4 3 5% 6% 48%	6490

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	51% 7% 7% 18% 11% 6%	4078
	11th to 20th	Day	40% 7% 11% 17% 17% 8%	4080
	21st to end	Day	55% 4 5% 12% 15% 9%	4488
February	1st to 10th	Day	51% 5% 7% 12% 14% 11%	2000
	11th to 20th	Day	49% 6% 9% 14% 15% 7%	1959
	21st to end	Day	45% 7% 12% 16% 13% 7%	1815
March	1st to 10th	Day	50% 11% 13% 13% 8% 4	3546
	11th to 20th	Day	51% 10% 9% 12% 12% 5%	3590
	21st to end	Day	33% 7% 13% 21% 19% 6%	3880
April	1st to 10th	Day	42% 9% 12% 18% 13% 7%	2090
	11th to 20th	Day	42% 9% 13% 16% 13% 8%	2149
	21st to end	Day	35% 7% 13% 24% 14% 7%	2280
May	1st to 10th	Day	44% 11% 18% 16% 8% 3	3885
	11th to 20th	Day	38% 10% 13% 20% 14% 4	4086
	21st to end	Day	30% 13% 18% 32% 6%	4489
June	1st to 10th	Day	22% 9% 22% 33% 13%	2470
	11th to 20th	Day	27% 11% 19% 29% 13% 1	2470
	21st to end	Day	33% 13% 23% 27% 5%	2470
July	1st to 10th	Day	35% 8% 34% 21% 2	4056
	11th to 20th	Day	45% 11% 26% 15% 3	4051
	21st to end	Day	40% 11% 27% 19% 2	4325
August	1st to 10th	Day	14% 8% 22% 49% 8%	4090
	11th to 20th	Day	21% 10% 41% 26% 3	3932
	21st to end	Day	32% 12% 25% 23% 8% 1	3891
September	1st to 10th	Day	39% 13% 18% 16% 11% 2	2090
	11th to 20th	Day	38% 12% 14% 20% 13% 2	2090
	21st to end	Day	32% 10% 14% 20% 17% 8%	2090
October	1st to 10th	Day	20% 5% 9% 16% 21% 29%	3362
	11th to 20th	Day	23% 5% 8% 25% 28% 10%	3140
	21st to end	Day	25% 4 7% 23% 31% 10%	3428
November	1st to 10th	Day	36% 9% 12% 20% 17% 6%	1958
	11th to 20th	Day	39% 6% 11% 17% 15% 12%	2000
	21st to end	Day	44% 6% 11% 16% 14% 9%	1952
December	1st to 10th	Day	57% 5% 8% 14% 13% 3	2940
	11th to 20th	Day	37% 8% 10% 21% 15% 11%	3389
	21st to end	Day	40% 5% 9% 17% 18% 11%	4488
January	1st to 10th	Night	49% 6% 7% 14% 15% 10%	5888
	11th to 20th	Night	40% 4 7% 17% 21% 10%	5900
	21st to end	Night	54% 4 7% 11% 15% 9%	6490
February	1st to 10th	Night	46% 4 10% 11% 16% 13%	2416
	11th to 20th	Night	42% 6% 9% 16% 17% 11%	2337
	21st to end	Night	44% 6% 8% 16% 18% 8%	1815
March	1st to 10th	Night	47% 8% 14% 16% 9% 5%	3529
	11th to 20th	Night	51% 9% 11% 13% 9% 6%	3590
	21st to end	Night	31% 7% 12% 18% 24% 8%	3889
April	1st to 10th	Night	41% 7% 11% 17% 16% 8%	2090
	11th to 20th	Night	38% 7% 11% 18% 13% 13%	1978
	21st to end	Night	37% 6% 12% 22% 15% 7%	1900
May	1st to 10th	Night	46% 9% 14% 17% 10% 5%	3073
	11th to 20th	Night	36% 8% 15% 21% 14% 6%	2824
	21st to end	Night	31% 12% 19% 29% 9% 1	3099
June	1st to 10th	Night	22% 8% 20% 33% 17% 1	1710
	11th to 20th	Night	26% 8% 15% 33% 16% 2	1710
	21st to end	Night	30% 11% 24% 28% 7% 1	1710
July	1st to 10th	Night	30% 6% 32% 28% 3	2805
	11th to 20th	Night	32% 11% 32% 21% 4	2796
	21st to end	Night	36% 12% 29% 21% 2	2999
August	1st to 10th	Night	8% 6% 18% 56% 12%	2826
	11th to 20th	Night	19% 7% 38% 32% 3	2965
	21st to end	Night	22% 12% 29% 27% 9% 1	3757
September	1st to 10th	Night	34% 11% 22% 18% 12% 3	2090
	11th to 20th	Night	37% 10% 14% 21% 15% 2	2090
	21st to end	Night	31% 9% 13% 23% 17% 7%	2090
October	1st to 10th	Night	20% 5% 10% 15% 18% 32%	3566
	11th to 20th	Night	17% 4 9% 26% 29% 14%	3779
	21st to end	Night	19% 4 7% 24% 34% 12%	4120
November	1st to 10th	Night	32% 7% 13% 21% 20% 7%	2340
	11th to 20th	Night	37% 5% 12% 18% 18% 11%	2400
	21st to end	Night	41% 6% 10% 18% 17% 8%	2444
December	1st to 10th	Night	58% 5% 8% 14% 11% 4	4250
	11th to 20th	Night	39% 5% 10% 18% 14% 13%	4817
	21st to end	Night	37% 6% 7% 17% 22% 11%	6490

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	23% 7% 26% 32% 11% 1	300
	11th to 20th	Day	20% 10% 21% 35% 14%	300
	21st to end	Day	20% 9% 28% 32% 12%	330
February	1st to 10th	Day	22% 7% 25% 31% 13% 1	300
	11th to 20th	Day	27% 9% 22% 29% 12% 1	300
	21st to end	Day	22% 8% 22% 40% 7%	249
March	1st to 10th	Day	20% 7% 28% 37% 8%	300
	11th to 20th	Day	19% 9% 28% 34% 9% 1	300
	21st to end	Day	14% 7% 26% 42% 11%	315
April	1st to 10th	Day	16% 6% 35% 34% 10%	270
	11th to 20th	Day	18% 6% 29% 31% 16% 1	347
	21st to end	Day	13% 5% 23% 39% 19%	460
May	1st to 10th	Day	13% 6% 20% 42% 19% 1	509
	11th to 20th	Day	9% 4 16% 40% 27% 3	675
	21st to end	Day	6% 2 11% 42% 35% 3	734
June	1st to 10th	Day	6% 1 4 32% 47% 10%	680
	11th to 20th	Day	6% 1 4 28% 51% 10%	680
	21st to end	Day	8% 1 3 21% 48% 19%	680
July	1st to 10th	Day	8% 1 4 14% 46% 26%	671
	11th to 20th	Day	4 1 1 6% 55% 32%	668
	21st to end	Day	6% 1 2 10% 54% 28%	739
August	1st to 10th	Day	1 1 10% 48% 39%	676
	11th to 20th	Day	4 1 2 6% 44% 44%	582
	21st to end	Day	7% 1 4 9% 41% 39%	368
September	1st to 10th	Day	10% 2 2 17% 39% 30%	300
	11th to 20th	Day	9% 2 17% 42% 30%	300
	21st to end	Day	8% 3 14% 54% 20%	300
October	1st to 10th	Day	5% 2 4 27% 47% 14%	300
	11th to 20th	Day	10% 1 7% 28% 38% 15%	300
	21st to end	Day	15% 5% 16% 29% 31% 5%	330
November	1st to 10th	Day	12% 4 15% 31% 31% 7%	300
	11th to 20th	Day	18% 3 12% 35% 28% 5%	300
	21st to end	Day	19% 9% 22% 30% 16% 4	300
December	1st to 10th	Day	20% 4 21% 32% 19% 4	300
	11th to 20th	Day	19% 8% 20% 36% 15% 2	300
	21st to end	Day	19% 5% 20% 37% 17% 2	330
January	1st to 10th	Night	20% 7% 28% 30% 14% 1	1000
	11th to 20th	Night	19% 7% 27% 34% 13%	1000
	21st to end	Night	22% 6% 24% 37% 10%	1100
February	1st to 10th	Night	21% 6% 24% 36% 13%	816
	11th to 20th	Night	23% 10% 20% 34% 13%	783
	21st to end	Night	20% 10% 24% 37% 9%	495
March	1st to 10th	Night	21% 6% 23% 36% 14%	600
	11th to 20th	Night	16% 6% 24% 41% 13% 1	600
	21st to end	Night	13% 4 24% 41% 16% 1	647
April	1st to 10th	Night	16% 4 24% 41% 14%	570
	11th to 20th	Night	17% 7% 23% 36% 17%	563
	21st to end	Night	14% 5% 25% 39% 16% 1	570
May	1st to 10th	Night	14% 3 21% 44% 17%	570
	11th to 20th	Night	10% 3 14% 45% 25% 3	561
	21st to end	Night	7% 3 11% 41% 37% 1	617
June	1st to 10th	Night	4 1 4 29% 55% 6%	570
	11th to 20th	Night	6% 3 31% 54% 6%	570
	21st to end	Night	5% 1 4 24% 48% 18%	570
July	1st to 10th	Night	5% 2 4 17% 51% 22%	555
	11th to 20th	Night	2 2 10% 55% 30%	552
	21st to end	Night	4 1 1 12% 57% 25%	624
August	1st to 10th	Night	1 1 8% 59% 31%	567
	11th to 20th	Night	4 2 7% 60% 27%	564
	21st to end	Night	6% 2 10% 53% 28%	627
September	1st to 10th	Night	6% 1 4 13% 52% 24%	570
	11th to 20th	Night	13% 1 3 16% 50% 18%	570
	21st to end	Night	8% 5% 22% 51% 13%	570
October	1st to 10th	Night	5% 1 7% 25% 50% 12%	617
	11th to 20th	Night	8% 2 12% 31% 41% 6%	760
	21st to end	Night	11% 3 15% 32% 34% 5%	836
November	1st to 10th	Night	9% 3 11% 33% 37% 6%	780
	11th to 20th	Night	15% 3 17% 35% 28% 3	800
	21st to end	Night	16% 4 21% 37% 20% 3	844
December	1st to 10th	Night	21% 6% 19% 30% 21% 3	1000
	11th to 20th	Night	18% 7% 22% 34% 18% 1	1000
	21st to end	Night	20% 8% 22% 33% 15% 2	1100

Page generated at 2025-03-24 08:04:26. Version ac07

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