Lady Bird Johnson Municipal Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lady Bird Johnson Municipal Park clear sky chart from 2005-11-06 to 2024-11-04.

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 5% 4 4 4 4 5% 7% 49%	100990
	Night	11% 6% 2 5% 3 3 3 3 5% 7% 53%	98146
Transparency	Day	34% 5% 10% 21% 20% 10%	104847
	Night	31% 5% 10% 21% 20% 13%	102416
Seeing	Day	13% 8% 22% 30% 21% 6%	14835
	Night	13% 8% 26% 36% 15% 1	24740

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% 8% 2 5% 3 2 3 3 4 5% 56%	2847
	11th to 20th	Day	12% 8% 2 3 2 2 2 3 4 5% 57%	2850
	21st to end	Day	15% 7% 2 5% 3 3 3 3 4 8% 49%	3459
February	1st to 10th	Day	15% 7% 2 6% 3 3 3 3 4 5% 49%	1900
	11th to 20th	Day	14% 7% 2 5% 4 3 4 3 5% 5% 48%	1849
	21st to end	Day	14% 6% 2 5% 2 3 3 3 4 6% 52%	1570
March	1st to 10th	Day	15% 7% 2 5% 4 3 4 3 5% 6% 45%	3310
	11th to 20th	Day	17% 10% 3 8% 4 4 5% 3 4 5% 36%	3480
	21st to end	Day	12% 6% 2 6% 4 4 3 3 5% 7% 48%	3814
April	1st to 10th	Day	13% 7% 3 6% 4 4 3 3 5% 6% 46%	2090
	11th to 20th	Day	17% 6% 2 5% 4 4 3 3 4 6% 45%	2159
	21st to end	Day	12% 7% 2 6% 5% 4 4 3 4 5% 48%	2370
May	1st to 10th	Day	19% 8% 2 6% 4 4 4 3 5% 6% 36%	4082
	11th to 20th	Day	16% 6% 2 6% 4 4 4 3 4 6% 45%	4082
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 4 7% 9% 39%	4477
June	1st to 10th	Day	6% 4 1 5% 4 4 5% 4 6% 9% 50%	2470
	11th to 20th	Day	6% 5% 2 4 5% 4 4 4 7% 9% 49%	2470
	21st to end	Day	7% 4 2 6% 5% 6% 6% 6% 7% 9% 43%	2470
July	1st to 10th	Day	6% 4 2 6% 4 5% 6% 4 7% 9% 47%	4120
	11th to 20th	Day	4 3 1 4 3 4 5% 4 7% 10% 54%	4120
	21st to end	Day	8% 4 2 5% 4 5% 7% 5% 8% 10% 42%	4465
August	1st to 10th	Day	1 1 1 3 3 3 3 3 5% 9% 68%	3947
	11th to 20th	Day	4 3 1 3 3 3 3 4 6% 10% 60%	3726
	21st to end	Day	4 3 2 5% 5% 5% 7% 5% 8% 10% 46%	4094
September	1st to 10th	Day	10% 7% 2 7% 5% 4 4 3 4 6% 46%	2090
	11th to 20th	Day	10% 6% 2 7% 6% 4 5% 4 6% 8% 42%	2090
	21st to end	Day	9% 4 1 5% 5% 4 4 4 7% 7% 50%	2090
October	1st to 10th	Day	6% 4 1 5% 3 3 4 3 5% 7% 57%	2090
	11th to 20th	Day	12% 5% 2 4 3 3 4 3 4 5% 53%	2014
	21st to end	Day	11% 4 2 4 3 2 3 3 3 5% 59%	2090
November	1st to 10th	Day	14% 8% 2 6% 3 3 3 3 5% 5% 48%	1879
	11th to 20th	Day	9% 5% 2 5% 4 4 4 3 5% 6% 52%	1710
	21st to end	Day	16% 6% 2 5% 4 3 3 3 4 5% 49%	1710
December	1st to 10th	Day	14% 7% 3 5% 2 3 2 2 5% 6% 51%	1710
	11th to 20th	Day	14% 7% 2 6% 4 3 3 3 4 7% 47%	2161
	21st to end	Day	12% 7% 2 5% 3 2 2 2 3 4 58%	3135
January	1st to 10th	Night	14% 6% 3 5% 2 2 2 2 4 5% 56%	4108
	11th to 20th	Night	11% 4 1 3 2 2 2 2 2 4 67%	4120
	21st to end	Night	17% 7% 2 6% 4 3 3 2 4 6% 45%	4235
February	1st to 10th	Night	13% 7% 2 6% 4 3 3 2 3 5% 51%	2280
	11th to 20th	Night	14% 7% 3 5% 3 3 3 2 4 5% 51%	2218
	21st to end	Night	14% 8% 2 4 4 3 3 2 5% 5% 50%	1884
March	1st to 10th	Night	12% 9% 3 5% 4 3 3 3 5% 7% 45%	3547
	11th to 20th	Night	17% 11% 2 6% 4 4 4 4 5% 5% 37%	3480
	21st to end	Night	13% 8% 2 5% 4 3 3 3 5% 6% 48%	3817
April	1st to 10th	Night	9% 7% 3 6% 3 4 3 3 6% 6% 50%	2090
	11th to 20th	Night	15% 8% 2 5% 4 3 3 3 4 6% 48%	1966
	21st to end	Night	15% 7% 2 5% 3 3 3 3 4 6% 50%	1809
May	1st to 10th	Night	23% 10% 2 5% 3 2 3 3 3 6% 40%	2823
	11th to 20th	Night	11% 6% 2 6% 4 3 4 3 5% 6% 51%	2823
	21st to end	Night	14% 5% 2 5% 3 4 4 3 6% 9% 47%	3090
June	1st to 10th	Night	4 3 1 3 3 3 4 4 5% 10% 60%	1710
	11th to 20th	Night	5% 3 1 4 2 3 3 3 5% 8% 62%	1710
	21st to end	Night	6% 4 1 3 4 4 4 4 6% 8% 56%	1710
July	1st to 10th	Night	5% 3 1 4 3 4 4 4 6% 10% 55%	2850
	11th to 20th	Night	3 3 1 4 3 3 3 4 6% 9% 61%	2850
	21st to end	Night	5% 7% 2 6% 4 4 4 4 6% 10% 47%	3098
August	1st to 10th	Night	1 2 1 2 2 2 3 3 4 6% 75%	2987
	11th to 20th	Night	3 2 1 3 2 3 4 4 6% 11% 62%	3113
	21st to end	Night	4 5% 2 4 3 3 4 4 7% 11% 54%	3570
September	1st to 10th	Night	9% 4 2 6% 3 4 5% 3 5% 8% 51%	2090
	11th to 20th	Night	9% 6% 3 5% 4 4 5% 3 5% 8% 47%	2090
	21st to end	Night	7% 5% 3 5% 4 4 4 3 5% 8% 54%	2090
October	1st to 10th	Night	5% 4 1 4 3 2 3 2 5% 6% 64%	2090
	11th to 20th	Night	12% 4 2 5% 3 3 4 2 5% 6% 56%	2145
	21st to end	Night	13% 5% 1 4 3 2 3 1 3 4 61%	2508
November	1st to 10th	Night	12% 6% 2 6% 3 3 3 2 3 6% 55%	2267
	11th to 20th	Night	9% 6% 2 4 3 3 3 3 4 6% 58%	2470
	21st to end	Night	16% 6% 2 5% 3 3 3 3 4 6% 49%	2470
December	1st to 10th	Night	12% 7% 2 4 3 3 3 3 5% 6% 53%	2470
	11th to 20th	Night	12% 9% 3 7% 3 3 3 2 4 5% 48%	3036
	21st to end	Night	16% 6% 2 4 2 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 16% 25% 19%	2848
	11th to 20th	Day	32% 3 5% 13% 31% 16%	2850
	21st to end	Day	37% 3 5% 13% 29% 13%	3459
February	1st to 10th	Day	39% 4 6% 12% 23% 18%	1900
	11th to 20th	Day	39% 4 6% 18% 19% 15%	1859
	21st to end	Day	35% 4 5% 18% 22% 17%	1570
March	1st to 10th	Day	41% 4 6% 13% 21% 15%	3310
	11th to 20th	Day	52% 5% 7% 10% 17% 10%	3480
	21st to end	Day	36% 5% 9% 16% 19% 15%	3814
April	1st to 10th	Day	39% 5% 8% 17% 18% 14%	2090
	11th to 20th	Day	41% 4 7% 17% 19% 12%	2159
	21st to end	Day	39% 5% 6% 21% 19% 11%	2370
May	1st to 10th	Day	48% 6% 10% 14% 16% 7%	4120
	11th to 20th	Day	40% 5% 9% 17% 20% 9%	4086
	21st to end	Day	38% 9% 11% 27% 11% 3	4489
June	1st to 10th	Day	29% 7% 13% 28% 20% 4	2470
	11th to 20th	Day	30% 7% 11% 27% 20% 6%	2470
	21st to end	Day	36% 7% 12% 23% 17% 4	2470
July	1st to 10th	Day	31% 6% 17% 38% 8% 1	4056
	11th to 20th	Day	25% 5% 15% 35% 17% 3	4051
	21st to end	Day	33% 6% 17% 31% 12% 1	4325
August	1st to 10th	Day	14% 4 11% 40% 30% 1	3933
	11th to 20th	Day	21% 4 22% 38% 13% 2	3762
	21st to end	Day	30% 7% 18% 24% 18% 2	4093
September	1st to 10th	Day	39% 7% 10% 18% 18% 9%	2090
	11th to 20th	Day	38% 7% 11% 20% 18% 5%	2090
	21st to end	Day	33% 6% 9% 21% 19% 13%	2090
October	1st to 10th	Day	17% 3 6% 11% 26% 36%	3480
	11th to 20th	Day	25% 3 7% 19% 24% 22%	3332
	21st to end	Day	27% 3 3 18% 36% 13%	3428
November	1st to 10th	Day	39% 5% 7% 19% 20% 11%	1879
	11th to 20th	Day	34% 5% 7% 17% 21% 17%	1710
	21st to end	Day	39% 4 5% 15% 22% 14%	1710
December	1st to 10th	Day	37% 3 8% 18% 24% 10%	1710
	11th to 20th	Day	39% 4 7% 11% 21% 17%	2159
	21st to end	Day	32% 2 4 15% 29% 17%	3135
January	1st to 10th	Night	34% 2 3 14% 26% 21%	4108
	11th to 20th	Night	25% 2 4 17% 27% 25%	4120
	21st to end	Night	42% 3 4 12% 26% 14%	4235
February	1st to 10th	Night	38% 3 6% 11% 23% 19%	2280
	11th to 20th	Night	36% 4 5% 17% 21% 17%	2218
	21st to end	Night	38% 4 6% 12% 21% 18%	1884
March	1st to 10th	Night	41% 4 6% 14% 22% 12%	3547
	11th to 20th	Night	49% 6% 8% 12% 14% 11%	3480
	21st to end	Night	37% 6% 9% 16% 18% 14%	3817
April	1st to 10th	Night	35% 5% 9% 18% 17% 16%	2090
	11th to 20th	Night	39% 4 9% 14% 18% 16%	1966
	21st to end	Night	39% 4 8% 20% 19% 10%	1809
May	1st to 10th	Night	47% 4 8% 18% 12% 10%	2850
	11th to 20th	Night	33% 6% 11% 22% 17% 10%	2824
	21st to end	Night	34% 7% 14% 29% 11% 5%	3099
June	1st to 10th	Night	20% 8% 16% 33% 20% 3	1710
	11th to 20th	Night	21% 7% 14% 30% 22% 6%	1710
	21st to end	Night	26% 6% 17% 29% 18% 4	1710
July	1st to 10th	Night	24% 7% 24% 38% 6% 1	2805
	11th to 20th	Night	20% 6% 20% 36% 17% 1	2796
	21st to end	Night	32% 5% 23% 31% 8%	2999
August	1st to 10th	Night	12% 3 14% 44% 26% 1	2977
	11th to 20th	Night	18% 5% 30% 35% 11% 2	3143
	21st to end	Night	25% 10% 21% 25% 19% 2	3570
September	1st to 10th	Night	32% 7% 13% 21% 19% 8%	2090
	11th to 20th	Night	34% 8% 15% 22% 16% 6%	2090
	21st to end	Night	30% 6% 12% 21% 18% 14%	2090
October	1st to 10th	Night	14% 3 8% 14% 22% 37%	3480
	11th to 20th	Night	22% 3 9% 17% 30% 19%	3553
	21st to end	Night	25% 2 4 20% 34% 15%	4120
November	1st to 10th	Night	33% 4 7% 20% 22% 13%	2267
	11th to 20th	Night	29% 4 8% 21% 21% 17%	2470
	21st to end	Night	38% 3 7% 15% 20% 16%	2470
December	1st to 10th	Night	32% 3 9% 20% 23% 13%	2470
	11th to 20th	Night	40% 3 5% 12% 20% 20%	3037
	21st to end	Night	34% 3 4 14% 29% 16%	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	20% 12% 38% 25% 5% 1	270
	11th to 20th	Day	20% 14% 31% 25% 8% 1	270
	21st to end	Day	15% 13% 39% 26% 7%	297
February	1st to 10th	Day	22% 15% 34% 21% 8%	270
	11th to 20th	Day	24% 13% 40% 20% 3	270
	21st to end	Day	24% 14% 41% 17% 4	225
March	1st to 10th	Day	18% 17% 40% 21% 4	270
	11th to 20th	Day	19% 16% 38% 20% 7% 1	270
	21st to end	Day	18% 15% 43% 18% 4 1	297
April	1st to 10th	Day	17% 19% 41% 20% 4	270
	11th to 20th	Day	21% 17% 36% 22% 4	357
	21st to end	Day	16% 15% 40% 23% 6%	550
May	1st to 10th	Day	15% 14% 38% 27% 6%	653
	11th to 20th	Day	19% 9% 29% 30% 11% 2	675
	21st to end	Day	18% 9% 26% 32% 14% 1	734
June	1st to 10th	Day	7% 4 16% 43% 25% 5%	680
	11th to 20th	Day	7% 3 16% 49% 20% 4	680
	21st to end	Day	7% 4 10% 37% 34% 8%	680
July	1st to 10th	Day	8% 4 8% 35% 33% 12%	671
	11th to 20th	Day	4 2 4 36% 43% 10%	668
	21st to end	Day	5% 1 4 35% 41% 13%	739
August	1st to 10th	Day	2 1 2 39% 41% 14%	584
	11th to 20th	Day	8% 2 3 32% 40% 14%	477
	21st to end	Day	7% 1 4 26% 42% 20%	492
September	1st to 10th	Day	10% 1 5% 29% 32% 23%	300
	11th to 20th	Day	6% 1 4 27% 43% 19%	300
	21st to end	Day	10% 3 4 28% 40% 15%	300
October	1st to 10th	Day	5% 3 12% 33% 37% 10%	300
	11th to 20th	Day	9% 4 22% 40% 22% 4	300
	21st to end	Day	18% 13% 25% 26% 15% 3	330
November	1st to 10th	Day	21% 8% 25% 33% 9% 5%	279
	11th to 20th	Day	18% 11% 25% 30% 12% 5%	270
	21st to end	Day	23% 14% 33% 19% 9% 2	270
December	1st to 10th	Day	14% 10% 32% 29% 13% 3	270
	11th to 20th	Day	16% 19% 34% 21% 10%	270
	21st to end	Day	15% 14% 34% 25% 11% 1	297
January	1st to 10th	Night	18% 9% 33% 32% 8% 1	950
	11th to 20th	Night	18% 10% 34% 32% 6%	950
	21st to end	Night	18% 11% 33% 30% 7%	865
February	1st to 10th	Night	20% 14% 32% 28% 6%	760
	11th to 20th	Night	20% 14% 36% 27% 3	744
	21st to end	Night	20% 13% 45% 21% 1	628
March	1st to 10th	Night	19% 13% 36% 30% 2	651
	11th to 20th	Night	20% 9% 37% 29% 5%	570
	21st to end	Night	14% 13% 44% 26% 4	627
April	1st to 10th	Night	11% 12% 47% 26% 3	570
	11th to 20th	Night	18% 12% 41% 26% 3	563
	21st to end	Night	16% 10% 44% 22% 6%	570
May	1st to 10th	Night	16% 11% 42% 28% 4	570
	11th to 20th	Night	12% 9% 34% 37% 8% 1	561
	21st to end	Night	13% 7% 33% 35% 12%	617
June	1st to 10th	Night	4 3 20% 50% 21% 1	570
	11th to 20th	Night	6% 2 26% 52% 14% 1	570
	21st to end	Night	6% 3 12% 49% 26% 2	570
July	1st to 10th	Night	9% 3 6% 50% 29% 3	555
	11th to 20th	Night	4 1 7% 52% 33% 3	552
	21st to end	Night	4 1 6% 53% 32% 4	624
August	1st to 10th	Night	2 1 4 51% 39% 3	567
	11th to 20th	Night	5% 2 4 48% 38% 3	564
	21st to end	Night	6% 3 6% 39% 39% 7%	627
September	1st to 10th	Night	10% 2 6% 42% 36% 5%	570
	11th to 20th	Night	12% 2 6% 41% 37% 3	570
	21st to end	Night	9% 2 11% 42% 33% 3	570
October	1st to 10th	Night	6% 3 9% 51% 28% 2	570
	11th to 20th	Night	12% 4 20% 46% 16% 2	625
	21st to end	Night	16% 8% 25% 30% 19% 2	836
November	1st to 10th	Night	14% 8% 20% 42% 16% 1	759
	11th to 20th	Night	12% 8% 27% 36% 15% 1	950
	21st to end	Night	19% 10% 29% 31% 10% 1	950
December	1st to 10th	Night	15% 10% 27% 37% 9% 1	950
	11th to 20th	Night	21% 11% 31% 31% 7%	950
	21st to end	Night	16% 11% 32% 34% 7%	1045

Page generated at 2024-11-01 21:47:49. Version ac07

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