Lyndon B. Johnson State Park & Historic Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lyndon B. Johnson State Park & Historic Site clear sky chart from 2005-11-06 to 2024-08-15.

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	11% 6% 2 6% 4 4 4 4 5% 7% 47%	95415
	Night	11% 6% 2 5% 4 3 3 3 5% 7% 52%	93384
Transparency	Day	35% 6% 10% 21% 19% 9%	95191
	Night	32% 6% 11% 20% 19% 12%	93214
Seeing	Day	12% 9% 24% 31% 20% 5%	14584
	Night	12% 8% 29% 35% 14% 1	24484

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	11% 9% 2 4 2 3 3 2 4 5% 54%	2847
	11th to 20th	Day	14% 6% 1 4 2 2 2 2 4 5% 57%	2850
	21st to end	Day	15% 7% 2 6% 4 3 2 3 4 7% 47%	3423
February	1st to 10th	Day	14% 8% 2 5% 4 4 3 2 4 6% 47%	1900
	11th to 20th	Day	14% 8% 2 5% 3 3 4 2 5% 6% 47%	1849
	21st to end	Day	15% 6% 1 4 3 2 3 3 5% 5% 51%	1570
March	1st to 10th	Day	14% 8% 3 8% 4 4 3 3 5% 6% 44%	3342
	11th to 20th	Day	17% 10% 3 9% 5% 4 4 4 5% 5% 35%	3480
	21st to end	Day	11% 6% 2 6% 4 4 4 4 5% 7% 46%	3814
April	1st to 10th	Day	11% 7% 3 7% 4 3 3 3 5% 7% 46%	2090
	11th to 20th	Day	17% 7% 2 5% 4 4 4 3 5% 5% 44%	2125
	21st to end	Day	13% 6% 2 6% 4 4 4 3 4 6% 47%	2392
May	1st to 10th	Day	18% 8% 3 7% 5% 5% 4 5% 5% 7% 34%	4082
	11th to 20th	Day	14% 7% 2 6% 5% 4 4 3 4 6% 45%	4082
	21st to end	Day	11% 5% 2 7% 5% 5% 6% 5% 7% 9% 38%	4477
June	1st to 10th	Day	5% 4 2 5% 5% 4 5% 6% 7% 8% 49%	2470
	11th to 20th	Day	7% 4 1 5% 4 4 5% 4 6% 9% 50%	2470
	21st to end	Day	7% 5% 2 7% 6% 5% 5% 5% 8% 9% 43%	2470
July	1st to 10th	Day	6% 4 2 5% 5% 4 5% 4 7% 10% 49%	4120
	11th to 20th	Day	4 3 1 4 3 4 5% 4 7% 11% 54%	4120
	21st to end	Day	8% 4 1 6% 4 5% 6% 5% 8% 10% 42%	4465
August	1st to 10th	Day	2 2 1 3 3 4 3 3 6% 8% 65%	2401
	11th to 20th	Day	6% 4 2 5% 4 5% 5% 4 6% 9% 51%	2172
	21st to end	Day	5% 4 1 7% 6% 5% 6% 5% 7% 10% 44%	2314
September	1st to 10th	Day	10% 6% 3 7% 5% 4 4 4 5% 6% 46%	1980
	11th to 20th	Day	10% 6% 2 7% 6% 5% 6% 4 6% 7% 40%	1980
	21st to end	Day	9% 4 1 5% 5% 4 4 4 6% 7% 50%	1980
October	1st to 10th	Day	7% 4 1 4 4 4 5% 4 6% 8% 55%	1980
	11th to 20th	Day	12% 5% 2 5% 3 4 4 4 4 5% 53%	1890
	21st to end	Day	11% 4 2 4 3 3 3 3 4 5% 58%	1980
November	1st to 10th	Day	13% 5% 2 6% 4 4 3 3 5% 6% 47%	1858
	11th to 20th	Day	9% 6% 2 6% 4 4 5% 3 5% 7% 51%	1726
	21st to end	Day	15% 6% 2 5% 4 3 3 3 3 5% 49%	1710
December	1st to 10th	Day	13% 6% 3 6% 3 3 3 3 5% 6% 50%	1710
	11th to 20th	Day	12% 7% 2 6% 4 3 3 4 5% 6% 46%	2161
	21st to end	Day	13% 6% 2 4 3 3 2 2 3 4 57%	3135
January	1st to 10th	Night	15% 6% 3 4 2 2 2 2 4 5% 54%	4108
	11th to 20th	Night	12% 3 1 3 2 2 2 2 3 4 66%	4120
	21st to end	Night	17% 7% 2 6% 4 4 3 3 4 6% 44%	4274
February	1st to 10th	Night	14% 5% 3 6% 4 2 3 3 5% 5% 50%	2280
	11th to 20th	Night	15% 6% 2 4 4 3 3 3 4 5% 51%	2218
	21st to end	Night	13% 7% 1 6% 5% 3 3 3 4 5% 49%	1884
March	1st to 10th	Night	11% 8% 2 8% 5% 4 4 3 5% 7% 44%	3515
	11th to 20th	Night	16% 10% 3 6% 5% 4 5% 4 6% 5% 36%	3480
	21st to end	Night	10% 8% 2 6% 5% 4 5% 4 5% 5% 46%	3817
April	1st to 10th	Night	9% 7% 2 5% 5% 3 4 3 6% 7% 49%	2090
	11th to 20th	Night	13% 7% 3 6% 4 4 4 3 4 6% 47%	2000
	21st to end	Night	14% 7% 2 5% 4 3 3 3 4 6% 49%	1786
May	1st to 10th	Night	19% 11% 3 5% 3 3 3 3 4 6% 40%	2823
	11th to 20th	Night	9% 7% 2 6% 4 4 4 3 5% 7% 51%	2823
	21st to end	Night	11% 5% 1 5% 3 4 5% 4 6% 9% 45%	3090
June	1st to 10th	Night	3 3 2 3 4 3 4 3 5% 8% 61%	1710
	11th to 20th	Night	4 3 1 4 3 3 4 3 6% 9% 61%	1710
	21st to end	Night	6% 4 1 4 3 3 3 5% 6% 9% 56%	1710
July	1st to 10th	Night	5% 4 1 3 3 3 4 4 6% 10% 57%	2850
	11th to 20th	Night	3 2 1 4 3 3 4 4 5% 9% 62%	2850
	21st to end	Night	4 5% 2 6% 4 5% 6% 5% 8% 10% 46%	3098
August	1st to 10th	Night	1 1 1 2 2 2 3 3 5% 9% 72%	1751
	11th to 20th	Night	5% 3 1 4 3 3 4 4 6% 10% 56%	1828
	21st to end	Night	6% 4 1 4 4 5% 4 4 6% 11% 51%	2042
September	1st to 10th	Night	7% 4 2 5% 4 4 5% 4 6% 8% 53%	1980
	11th to 20th	Night	8% 6% 2 7% 4 5% 4 4 6% 8% 46%	1980
	21st to end	Night	7% 4 1 5% 4 4 4 4 6% 8% 52%	1980
October	1st to 10th	Night	5% 3 1 3 3 3 4 3 5% 8% 62%	1980
	11th to 20th	Night	11% 4 2 4 3 4 4 3 5% 6% 54%	2052
	21st to end	Night	13% 4 2 4 3 3 2 2 3 4 61%	2376
November	1st to 10th	Night	11% 6% 2 5% 4 3 3 3 4 6% 55%	2220
	11th to 20th	Night	8% 6% 2 4 3 3 3 2 5% 6% 57%	2451
	21st to end	Night	15% 5% 2 5% 5% 4 3 3 5% 6% 48%	2470
December	1st to 10th	Night	13% 6% 2 4 3 2 3 3 5% 6% 54%	2470
	11th to 20th	Night	12% 9% 2 7% 4 3 3 2 4 5% 48%	3036
	21st to end	Night	14% 7% 2 4 3 2 2 2 3 5% 56%	4532

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	34% 3 3 17% 25% 18%	2848
	11th to 20th	Day	31% 3 6% 13% 31% 16%	2850
	21st to end	Day	38% 3 5% 12% 29% 12%	3423
February	1st to 10th	Day	40% 4 5% 13% 21% 17%	1900
	11th to 20th	Day	39% 4 7% 18% 19% 15%	1859
	21st to end	Day	36% 3 6% 17% 21% 17%	1570
March	1st to 10th	Day	41% 5% 6% 13% 21% 14%	3342
	11th to 20th	Day	50% 9% 6% 10% 16% 10%	3480
	21st to end	Day	35% 7% 9% 16% 19% 14%	3814
April	1st to 10th	Day	39% 5% 8% 17% 18% 13%	2090
	11th to 20th	Day	42% 5% 7% 16% 19% 11%	2125
	21st to end	Day	39% 5% 6% 21% 19% 10%	2392
May	1st to 10th	Day	48% 8% 8% 14% 16% 6%	4120
	11th to 20th	Day	40% 7% 8% 16% 21% 8%	4086
	21st to end	Day	39% 9% 11% 28% 11% 3	4489
June	1st to 10th	Day	29% 8% 13% 26% 20% 4	2470
	11th to 20th	Day	30% 8% 11% 27% 19% 5%	2470
	21st to end	Day	35% 9% 11% 23% 17% 4	2470
July	1st to 10th	Day	29% 7% 18% 37% 8% 1	4056
	11th to 20th	Day	23% 6% 17% 34% 17% 3	4051
	21st to end	Day	31% 9% 17% 31% 11% 1	4325
August	1st to 10th	Day	18% 5% 15% 40% 22% 1	2387
	11th to 20th	Day	28% 8% 17% 31% 12% 4	2172
	21st to end	Day	32% 10% 17% 25% 13% 4	2314
September	1st to 10th	Day	37% 8% 10% 20% 17% 8%	1980
	11th to 20th	Day	40% 9% 11% 18% 17% 5%	1980
	21st to end	Day	32% 7% 9% 22% 19% 11%	1980
October	1st to 10th	Day	27% 7% 12% 20% 24% 10%	1980
	11th to 20th	Day	34% 5% 8% 16% 22% 17%	1890
	21st to end	Day	30% 4 5% 16% 25% 21%	1980
November	1st to 10th	Day	37% 5% 8% 19% 20% 11%	1858
	11th to 20th	Day	34% 4 7% 17% 21% 15%	1726
	21st to end	Day	39% 4 5% 16% 22% 14%	1710
December	1st to 10th	Day	37% 4 8% 18% 23% 10%	1710
	11th to 20th	Day	39% 5% 8% 10% 21% 17%	2159
	21st to end	Day	32% 3 5% 15% 28% 17%	3135
January	1st to 10th	Night	34% 3 4 14% 26% 20%	4108
	11th to 20th	Night	25% 2 4 17% 28% 24%	4120
	21st to end	Night	41% 5% 5% 12% 25% 13%	4274
February	1st to 10th	Night	38% 4 6% 13% 22% 18%	2280
	11th to 20th	Night	36% 4 6% 17% 20% 17%	2218
	21st to end	Night	38% 4 7% 13% 21% 18%	1884
March	1st to 10th	Night	39% 7% 7% 15% 21% 11%	3515
	11th to 20th	Night	47% 8% 9% 11% 14% 11%	3480
	21st to end	Night	37% 8% 9% 16% 18% 12%	3817
April	1st to 10th	Night	34% 6% 9% 19% 17% 15%	2090
	11th to 20th	Night	39% 6% 9% 14% 18% 16%	2000
	21st to end	Night	38% 6% 8% 20% 19% 10%	1786
May	1st to 10th	Night	46% 7% 9% 17% 13% 9%	2850
	11th to 20th	Night	32% 8% 11% 22% 18% 9%	2824
	21st to end	Night	33% 9% 14% 29% 11% 4	3099
June	1st to 10th	Night	20% 9% 15% 32% 21% 3	1710
	11th to 20th	Night	20% 6% 15% 30% 23% 6%	1710
	21st to end	Night	24% 8% 17% 30% 18% 4	1710
July	1st to 10th	Night	22% 8% 26% 37% 6% 1	2805
	11th to 20th	Night	20% 7% 21% 35% 17% 1	2796
	21st to end	Night	29% 8% 24% 31% 8%	2999
August	1st to 10th	Night	12% 5% 20% 41% 20% 1	1741
	11th to 20th	Night	22% 10% 22% 29% 12% 3	1828
	21st to end	Night	27% 9% 21% 27% 12% 3	2042
September	1st to 10th	Night	29% 8% 16% 22% 18% 7%	1980
	11th to 20th	Night	35% 9% 14% 22% 15% 5%	1980
	21st to end	Night	29% 7% 13% 20% 19% 12%	1980
October	1st to 10th	Night	22% 6% 14% 25% 22% 11%	1980
	11th to 20th	Night	31% 6% 9% 15% 21% 19%	2052
	21st to end	Night	30% 3 5% 17% 23% 22%	2376
November	1st to 10th	Night	31% 5% 8% 19% 23% 13%	2220
	11th to 20th	Night	29% 4 9% 21% 20% 17%	2451
	21st to end	Night	38% 4 8% 15% 20% 15%	2470
December	1st to 10th	Night	32% 5% 8% 20% 22% 13%	2470
	11th to 20th	Night	40% 4 5% 12% 21% 19%	3037
	21st to end	Night	34% 3 5% 14% 29% 15%	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	19% 15% 41% 20% 4 1	270
	11th to 20th	Day	20% 15% 36% 21% 6% 1	270
	21st to end	Day	16% 18% 39% 21% 5% 1	297
February	1st to 10th	Day	26% 15% 32% 24% 3	270
	11th to 20th	Day	24% 23% 36% 16% 1	270
	21st to end	Day	25% 23% 38% 14%	225
March	1st to 10th	Day	18% 20% 39% 20% 3	270
	11th to 20th	Day	19% 19% 36% 21% 5%	270
	21st to end	Day	17% 19% 45% 15% 4	297
April	1st to 10th	Day	18% 22% 40% 17% 4	270
	11th to 20th	Day	19% 22% 36% 20% 4	323
	21st to end	Day	17% 15% 41% 22% 5%	572
May	1st to 10th	Day	14% 16% 40% 24% 6%	653
	11th to 20th	Day	18% 11% 30% 30% 9% 2	675
	21st to end	Day	16% 7% 29% 34% 14% 1	734
June	1st to 10th	Day	6% 3 21% 42% 24% 4	680
	11th to 20th	Day	7% 2 19% 49% 19% 4	680
	21st to end	Day	6% 2 14% 41% 29% 7%	680
July	1st to 10th	Day	8% 2 13% 36% 33% 9%	671
	11th to 20th	Day	4 1 7% 40% 42% 7%	668
	21st to end	Day	3 1 8% 39% 39% 10%	739
August	1st to 10th	Day	2 4 41% 41% 11%	619
	11th to 20th	Day	6% 7% 36% 39% 12%	454
	21st to end	Day	4 1 6% 29% 43% 17%	433
September	1st to 10th	Day	10% 9% 23% 38% 20%	270
	11th to 20th	Day	6% 1 5% 30% 45% 13%	270
	21st to end	Day	11% 1 7% 31% 37% 13%	270
October	1st to 10th	Day	7% 14% 39% 30% 9%	270
	11th to 20th	Day	11% 5% 26% 35% 19% 4	270
	21st to end	Day	18% 16% 26% 26% 13% 1	297
November	1st to 10th	Day	19% 5% 29% 34% 9% 4	270
	11th to 20th	Day	19% 10% 31% 27% 11% 3	270
	21st to end	Day	22% 19% 32% 18% 7% 2	270
December	1st to 10th	Day	16% 11% 32% 30% 8% 3	270
	11th to 20th	Day	17% 20% 34% 23% 6%	270
	21st to end	Day	15% 14% 39% 26% 4 1	297
January	1st to 10th	Night	16% 11% 35% 31% 7%	950
	11th to 20th	Night	17% 12% 35% 31% 5%	950
	21st to end	Night	17% 12% 34% 30% 7%	891
February	1st to 10th	Night	19% 13% 37% 26% 5%	760
	11th to 20th	Night	19% 14% 40% 24% 2	744
	21st to end	Night	19% 17% 45% 17% 1	628
March	1st to 10th	Night	17% 14% 39% 28% 2	632
	11th to 20th	Night	18% 11% 36% 31% 4	570
	21st to end	Night	14% 15% 44% 24% 4	627
April	1st to 10th	Night	10% 15% 46% 27% 3	570
	11th to 20th	Night	15% 14% 42% 26% 2	563
	21st to end	Night	15% 12% 45% 22% 6%	570
May	1st to 10th	Night	12% 14% 43% 27% 4	570
	11th to 20th	Night	11% 8% 39% 32% 10% 1	561
	21st to end	Night	12% 7% 35% 35% 11% 1	617
June	1st to 10th	Night	3 2 26% 47% 21% 1	570
	11th to 20th	Night	5% 2 33% 46% 14% 1	570
	21st to end	Night	5% 2 19% 51% 21% 3	570
July	1st to 10th	Night	8% 3 11% 51% 25% 2	555
	11th to 20th	Night	4 1 12% 52% 29% 2	552
	21st to end	Night	3 1 11% 54% 28% 3	624
August	1st to 10th	Night	1 1 8% 56% 31% 3	567
	11th to 20th	Night	6% 1 5% 52% 32% 4	549
	21st to end	Night	5% 1 7% 44% 37% 5%	594
September	1st to 10th	Night	8% 9% 44% 32% 6%	540
	11th to 20th	Night	10% 1 10% 39% 35% 4	540
	21st to end	Night	9% 1 15% 42% 31% 2	540
October	1st to 10th	Night	6% 1 16% 47% 26% 3	540
	11th to 20th	Night	12% 5% 23% 42% 16% 2	612
	21st to end	Night	14% 9% 29% 27% 19% 2	792
November	1st to 10th	Night	11% 6% 25% 40% 17% 1	740
	11th to 20th	Night	11% 9% 28% 36% 15% 1	931
	21st to end	Night	17% 10% 34% 29% 10% 1	950
December	1st to 10th	Night	16% 9% 30% 36% 8% 1	950
	11th to 20th	Night	19% 11% 33% 32% 6%	950
	21st to end	Night	16% 11% 35% 30% 7%	1045

Page generated at 2024-08-12 08:52:53. Version ac07

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