Martin Dies, Jr. State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Martin Dies, Jr. State Park clear sky chart from 2005-11-06 to 2025-07-21.

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	14% 7% 2 7% 5% 5% 5% 4 6% 7% 41%	120147
	Night	15% 7% 2 5% 4 3 4 3 5% 7% 45%	119169
Transparency	Day	41% 5% 10% 18% 18% 7%	123796
	Night	38% 5% 11% 18% 19% 9%	123663
Seeing	Day	15% 8% 21% 25% 21% 9%	15911
	Night	17% 7% 23% 32% 19% 3	25703

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	20% 9% 2 5% 3 3 3 3 4 5% 43%	4077
	11th to 20th	Day	16% 6% 2 6% 3 3 3 2 3 5% 50%	4080
	21st to end	Day	27% 9% 2 6% 3 3 2 2 4 6% 37%	4488
February	1st to 10th	Day	19% 9% 3 7% 5% 5% 4 3 4 5% 37%	1800
	11th to 20th	Day	23% 10% 3 5% 4 3 2 3 3 4 40%	1996
	21st to end	Day	20% 9% 3 8% 4 4 3 3 4 6% 36%	1815
March	1st to 10th	Day	20% 10% 3 8% 5% 4 3 2 4 5% 36%	4936
	11th to 20th	Day	14% 6% 2 7% 5% 4 4 3 4 6% 47%	4980
	21st to end	Day	17% 9% 3 7% 4 4 4 3 4 6% 40%	5462
April	1st to 10th	Day	14% 7% 3 8% 6% 5% 5% 4 5% 5% 39%	2254
	11th to 20th	Day	15% 7% 3 7% 5% 4 4 4 6% 6% 38%	2374
	21st to end	Day	12% 6% 3 6% 5% 5% 4 4 7% 7% 41%	2400
May	1st to 10th	Day	19% 8% 3 8% 5% 5% 5% 4 6% 7% 31%	5405
	11th to 20th	Day	12% 6% 3 7% 4 5% 5% 4 6% 7% 41%	5741
	21st to end	Day	11% 6% 2 7% 5% 6% 6% 5% 8% 10% 34%	6434
June	1st to 10th	Day	8% 5% 2 7% 6% 6% 7% 6% 8% 10% 36%	2600
	11th to 20th	Day	6% 4 2 7% 6% 7% 7% 5% 8% 11% 37%	2600
	21st to end	Day	8% 6% 3 6% 6% 7% 7% 6% 9% 11% 32%	2600
July	1st to 10th	Day	8% 6% 2 7% 7% 7% 7% 5% 9% 11% 31%	4250
	11th to 20th	Day	7% 7% 3 9% 7% 7% 7% 6% 8% 10% 29%	4250
	21st to end	Day	17% 9% 3 8% 6% 5% 6% 5% 6% 8% 27%	4466
August	1st to 10th	Day	2 2 1 3 3 4 4 4 6% 8% 61%	4104
	11th to 20th	Day	3 2 1 4 3 5% 6% 5% 8% 12% 52%	3764
	21st to end	Day	9% 4 2 7% 6% 6% 7% 5% 7% 9% 39%	4180
September	1st to 10th	Day	9% 6% 3 7% 5% 6% 6% 5% 6% 8% 40%	2239
	11th to 20th	Day	14% 6% 2 7% 6% 5% 5% 4 6% 7% 39%	2090
	21st to end	Day	9% 3 2 5% 4 5% 4 4 5% 7% 50%	2082
October	1st to 10th	Day	8% 3 2 5% 4 3 4 2 4 6% 58%	1900
	11th to 20th	Day	11% 4 2 4 4 3 3 3 4 7% 54%	1900
	21st to end	Day	15% 5% 2 5% 3 3 4 2 4 5% 53%	2090
November	1st to 10th	Day	12% 6% 2 6% 5% 3 5% 3 5% 6% 47%	1958
	11th to 20th	Day	11% 7% 2 6% 4 3 4 3 4 6% 51%	2000
	21st to end	Day	16% 7% 3 7% 4 3 4 3 4 4 45%	2000
December	1st to 10th	Day	21% 8% 2 5% 3 3 3 3 3 5% 44%	2953
	11th to 20th	Day	16% 11% 3 7% 4 4 3 3 4 6% 40%	3391
	21st to end	Day	16% 7% 3 5% 4 3 3 3 4 5% 46%	4488
January	1st to 10th	Night	18% 6% 2 4 3 3 2 3 3 6% 50%	5888
	11th to 20th	Night	17% 9% 2 5% 2 3 3 2 3 4 50%	5900
	21st to end	Night	27% 11% 3 6% 3 3 3 2 3 5% 35%	6490
February	1st to 10th	Night	19% 9% 3 5% 4 4 3 3 5% 6% 40%	2600
	11th to 20th	Night	23% 9% 3 4 3 3 2 2 4 5% 41%	2304
	21st to end	Night	20% 9% 3 6% 4 4 3 3 4 4 40%	1815
March	1st to 10th	Night	22% 10% 2 5% 4 3 3 3 4 5% 38%	4919
	11th to 20th	Night	18% 7% 3 6% 4 3 3 3 4 5% 45%	4980
	21st to end	Night	18% 8% 3 6% 4 4 4 3 4 5% 41%	5467
April	1st to 10th	Night	15% 6% 2 6% 4 4 5% 3 5% 7% 42%	2145
	11th to 20th	Night	16% 6% 2 5% 4 3 4 3 6% 6% 45%	1975
	21st to end	Night	14% 5% 2 6% 4 4 4 3 5% 7% 46%	2000
May	1st to 10th	Night	21% 10% 3 7% 5% 4 4 3 5% 8% 30%	4490
	11th to 20th	Night	15% 6% 3 7% 5% 4 5% 4 5% 7% 40%	4151
	21st to end	Night	13% 7% 2 7% 5% 5% 5% 4 8% 10% 35%	4443
June	1st to 10th	Night	5% 5% 2 6% 4 4 5% 4 6% 10% 50%	1800
	11th to 20th	Night	4 4 1 3 3 3 5% 3 7% 10% 56%	1800
	21st to end	Night	7% 4 2 5% 4 4 5% 5% 9% 10% 46%	1800
July	1st to 10th	Night	6% 6% 2 6% 5% 5% 5% 5% 8% 12% 40%	2940
	11th to 20th	Night	6% 4 2 6% 5% 4 5% 5% 9% 12% 42%	2940
	21st to end	Night	13% 7% 3 7% 5% 4 4 4 6% 10% 35%	3098
August	1st to 10th	Night	2 2 1 2 2 2 3 2 5% 9% 70%	2836
	11th to 20th	Night	2 2 1 3 2 3 3 4 8% 12% 60%	3063
	21st to end	Night	8% 4 2 5% 5% 5% 5% 4 9% 11% 42%	3476
September	1st to 10th	Night	7% 4 2 6% 4 4 5% 4 7% 10% 47%	1935
	11th to 20th	Night	12% 6% 3 6% 4 5% 4 3 7% 7% 45%	2090
	21st to end	Night	9% 5% 2 4 3 3 3 3 5% 6% 55%	2090
October	1st to 10th	Night	5% 3 2 4 4 3 4 4 4 6% 62%	2266
	11th to 20th	Night	10% 4 2 4 3 3 3 3 5% 6% 58%	2280
	21st to end	Night	12% 5% 1 4 3 3 3 2 4 4 58%	2508
November	1st to 10th	Night	13% 6% 2 5% 3 4 3 3 4 6% 52%	2340
	11th to 20th	Night	11% 6% 1 5% 4 4 3 2 5% 6% 53%	2400
	21st to end	Night	15% 7% 2 5% 3 3 3 3 5% 6% 47%	2400
December	1st to 10th	Night	20% 9% 3 7% 4 3 3 2 4 5% 40%	4234
	11th to 20th	Night	16% 10% 2 6% 4 4 4 3 4 4 43%	4816
	21st to end	Night	16% 8% 2 5% 3 3 3 3 4 5% 49%	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	45% 3 5% 23% 19% 5%	4078
	11th to 20th	Day	39% 2 4 15% 29% 10%	4080
	21st to end	Day	51% 2 3 13% 17% 13%	4488
February	1st to 10th	Day	51% 4 5% 12% 18% 10%	1800
	11th to 20th	Day	50% 3 6% 16% 16% 10%	2006
	21st to end	Day	50% 4 7% 13% 16% 10%	1815
March	1st to 10th	Day	51% 4 6% 10% 19% 11%	4936
	11th to 20th	Day	39% 4 6% 13% 21% 16%	4980
	21st to end	Day	46% 4 8% 20% 17% 5%	5464
April	1st to 10th	Day	48% 5% 7% 16% 17% 8%	2254
	11th to 20th	Day	45% 5% 9% 14% 17% 10%	2374
	21st to end	Day	40% 6% 9% 18% 22% 5%	2400
May	1st to 10th	Day	51% 6% 9% 21% 10% 3	5440
	11th to 20th	Day	41% 5% 15% 18% 19% 2	5745
	21st to end	Day	42% 8% 12% 23% 13% 2	6447
June	1st to 10th	Day	40% 9% 14% 21% 15% 1	2600
	11th to 20th	Day	38% 9% 14% 23% 14% 2	2600
	21st to end	Day	42% 9% 18% 20% 10% 1	2600
July	1st to 10th	Day	45% 8% 25% 19% 4	4186
	11th to 20th	Day	47% 7% 18% 20% 7%	4181
	21st to end	Day	53% 8% 15% 18% 5% 1	4326
August	1st to 10th	Day	20% 6% 15% 34% 25% 1	4090
	11th to 20th	Day	24% 8% 26% 35% 7% 1	3800
	21st to end	Day	41% 8% 16% 18% 16% 1	4179
September	1st to 10th	Day	39% 8% 14% 17% 15% 6%	2239
	11th to 20th	Day	44% 8% 12% 16% 14% 6%	2090
	21st to end	Day	33% 6% 10% 21% 18% 11%	2082
October	1st to 10th	Day	19% 3 6% 14% 21% 37%	3160
	11th to 20th	Day	21% 3 4 20% 32% 21%	3140
	21st to end	Day	28% 3 4 11% 42% 13%	3428
November	1st to 10th	Day	37% 6% 9% 18% 20% 10%	1958
	11th to 20th	Day	37% 3 6% 16% 25% 14%	2000
	21st to end	Day	43% 4 6% 18% 21% 9%	2000
December	1st to 10th	Day	45% 3 5% 16% 25% 5%	2953
	11th to 20th	Day	47% 3 6% 12% 22% 10%	3389
	21st to end	Day	41% 3 6% 15% 27% 7%	4488
January	1st to 10th	Night	38% 2 6% 24% 24% 6%	5888
	11th to 20th	Night	40% 2 4 16% 30% 8%	5900
	21st to end	Night	54% 2 3 13% 15% 12%	6490
February	1st to 10th	Night	46% 3 7% 14% 17% 13%	2600
	11th to 20th	Night	48% 3 6% 15% 19% 10%	2304
	21st to end	Night	48% 5% 6% 12% 16% 13%	1815
March	1st to 10th	Night	49% 4 5% 12% 19% 11%	4919
	11th to 20th	Night	42% 5% 6% 13% 16% 17%	4980
	21st to end	Night	46% 4 7% 15% 20% 7%	5467
April	1st to 10th	Night	42% 7% 8% 17% 16% 10%	2145
	11th to 20th	Night	39% 5% 10% 18% 16% 12%	1975
	21st to end	Night	38% 5% 9% 18% 23% 6%	2000
May	1st to 10th	Night	53% 6% 10% 18% 11% 3	4520
	11th to 20th	Night	43% 5% 13% 18% 19% 2	4152
	21st to end	Night	42% 8% 16% 23% 10% 1	4452
June	1st to 10th	Night	28% 9% 18% 28% 16% 1	1800
	11th to 20th	Night	23% 8% 18% 33% 15% 3	1800
	21st to end	Night	29% 9% 23% 26% 11% 1	1800
July	1st to 10th	Night	35% 9% 33% 19% 4	2895
	11th to 20th	Night	33% 10% 27% 23% 7%	2886
	21st to end	Night	44% 9% 22% 19% 5%	2999
August	1st to 10th	Night	13% 6% 18% 35% 28% 1	2826
	11th to 20th	Night	16% 7% 31% 38% 8% 1	3093
	21st to end	Night	34% 12% 18% 19% 15% 2	3476
September	1st to 10th	Night	31% 9% 19% 19% 15% 7%	1935
	11th to 20th	Night	38% 6% 14% 19% 16% 7%	2090
	21st to end	Night	29% 5% 12% 22% 19% 13%	2090
October	1st to 10th	Night	16% 4 6% 17% 18% 39%	3786
	11th to 20th	Night	17% 2 5% 21% 31% 24%	3779
	21st to end	Night	25% 3 4 13% 38% 18%	4120
November	1st to 10th	Night	34% 4 11% 18% 22% 11%	2340
	11th to 20th	Night	33% 4 9% 17% 25% 13%	2400
	21st to end	Night	39% 4 8% 16% 22% 10%	2400
December	1st to 10th	Night	48% 3 5% 17% 21% 6%	4234
	11th to 20th	Night	44% 3 7% 12% 22% 12%	4817
	21st to end	Night	39% 4 6% 15% 28% 8%	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	25% 18% 38% 13% 5% 1	300
	11th to 20th	Day	28% 16% 30% 21% 4 1	300
	21st to end	Day	29% 21% 30% 17% 3	330
February	1st to 10th	Day	25% 17% 37% 16% 4 1	300
	11th to 20th	Day	36% 16% 31% 15% 2	300
	21st to end	Day	27% 27% 33% 11% 2	249
March	1st to 10th	Day	29% 19% 31% 15% 5%	300
	11th to 20th	Day	21% 26% 36% 14% 3 1	300
	21st to end	Day	24% 13% 43% 15% 4 1	330
April	1st to 10th	Day	17% 19% 39% 20% 5% 1	354
	11th to 20th	Day	24% 17% 26% 23% 8% 1	492
	21st to end	Day	17% 13% 33% 25% 10% 2	500
May	1st to 10th	Day	19% 11% 34% 24% 11% 1	503
	11th to 20th	Day	13% 8% 27% 33% 17% 3	669
	21st to end	Day	10% 6% 29% 33% 18% 5%	789
June	1st to 10th	Day	9% 3 17% 33% 28% 10%	730
	11th to 20th	Day	7% 2 17% 38% 28% 8%	730
	21st to end	Day	9% 2 12% 26% 33% 17%	730
July	1st to 10th	Day	8% 2 8% 28% 37% 17%	721
	11th to 20th	Day	7% 1 7% 25% 43% 17%	718
	21st to end	Day	9% 6% 27% 39% 19%	740
August	1st to 10th	Day	5% 1 5% 23% 43% 23%	676
	11th to 20th	Day	6% 2 1 16% 48% 28%	502
	21st to end	Day	12% 2 7% 18% 35% 26%	539
September	1st to 10th	Day	8% 2 8% 23% 38% 21%	449
	11th to 20th	Day	9% 2 12% 31% 29% 15%	300
	21st to end	Day	13% 2 11% 30% 29% 13%	300
October	1st to 10th	Day	7% 2 21% 37% 26% 7%	300
	11th to 20th	Day	9% 6% 22% 37% 18% 7%	300
	21st to end	Day	23% 8% 25% 23% 15% 6%	330
November	1st to 10th	Day	15% 7% 29% 28% 18% 3	300
	11th to 20th	Day	15% 12% 32% 31% 8% 1	300
	21st to end	Day	23% 16% 32% 21% 6% 2	300
December	1st to 10th	Day	23% 11% 33% 23% 6% 4	300
	11th to 20th	Day	25% 12% 35% 22% 5% 1	300
	21st to end	Day	27% 15% 33% 18% 4 2	330
January	1st to 10th	Night	24% 13% 30% 28% 6%	1000
	11th to 20th	Night	26% 12% 29% 26% 7%	1000
	21st to end	Night	25% 11% 31% 29% 3	1100
February	1st to 10th	Night	26% 12% 32% 26% 4	1000
	11th to 20th	Night	30% 12% 32% 22% 3	749
	21st to end	Night	27% 17% 31% 23% 2	495
March	1st to 10th	Night	28% 10% 31% 26% 5%	600
	11th to 20th	Night	21% 13% 34% 27% 5% 1	600
	21st to end	Night	18% 10% 37% 26% 8%	660
April	1st to 10th	Night	20% 9% 38% 27% 6%	600
	11th to 20th	Night	19% 10% 32% 29% 10%	593
	21st to end	Night	16% 7% 37% 29% 10% 1	600
May	1st to 10th	Night	19% 7% 31% 33% 10% 1	600
	11th to 20th	Night	16% 4 27% 37% 14% 1	591
	21st to end	Night	8% 5% 26% 36% 22% 3	650
June	1st to 10th	Night	7% 2 13% 39% 34% 5%	600
	11th to 20th	Night	4 2 19% 44% 27% 5%	600
	21st to end	Night	8% 1 10% 33% 40% 8%	600
July	1st to 10th	Night	5% 1 6% 38% 39% 11%	585
	11th to 20th	Night	5% 2 6% 36% 43% 8%	582
	21st to end	Night	5% 1 7% 35% 46% 6%	624
August	1st to 10th	Night	3 1 5% 38% 46% 7%	567
	11th to 20th	Night	4 1 4 37% 45% 10%	564
	21st to end	Night	10% 1 5% 29% 44% 11%	627
September	1st to 10th	Night	8% 1 6% 31% 43% 11%	570
	11th to 20th	Night	14% 1 9% 29% 41% 7%	570
	21st to end	Night	11% 3 11% 33% 34% 8%	570
October	1st to 10th	Night	6% 2 12% 38% 37% 5%	746
	11th to 20th	Night	12% 4 21% 41% 20% 2	760
	21st to end	Night	14% 7% 25% 32% 20% 2	836
November	1st to 10th	Night	14% 6% 23% 35% 20% 2	780
	11th to 20th	Night	15% 9% 25% 38% 13%	800
	21st to end	Night	19% 10% 30% 29% 12% 1	800
December	1st to 10th	Night	26% 9% 24% 30% 10% 1	984
	11th to 20th	Night	25% 10% 30% 29% 6%	1000
	21st to end	Night	23% 10% 32% 29% 6%	1100

Page generated at 2025-07-18 00:09:58. Version ac07

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