Hill Country State Natural Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hill Country State Natural Area clear sky chart from 2005-11-06 to 2025-02-21.

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% 6% 2 5% 4 4 4 3 5% 7% 47%	109202
	Night	15% 5% 2 4 3 3 3 3 4 6% 51%	109608
Transparency	Day	36% 5% 9% 20% 19% 10%	113072
	Night	33% 5% 10% 19% 19% 13%	113865
Seeing	Day	15% 8% 23% 30% 20% 4	15078
	Night	16% 7% 24% 37% 15% 1	25178

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	16% 8% 2 4 2 2 3 2 3 5% 53%	4077
	11th to 20th	Day	16% 5% 2 4 3 2 2 3 4 5% 54%	4154
	21st to end	Day	24% 8% 2 3 2 2 2 2 4 7% 44%	4994
February	1st to 10th	Day	17% 7% 2 6% 3 3 3 3 4 4 47%	2000
	11th to 20th	Day	19% 7% 2 5% 3 3 3 3 5% 5% 45%	1949
	21st to end	Day	18% 5% 2 4 2 2 3 2 4 6% 51%	1570
March	1st to 10th	Day	18% 9% 2 5% 3 3 3 3 3 5% 46%	3298
	11th to 20th	Day	24% 9% 3 8% 4 4 4 3 4 4 34%	3480
	21st to end	Day	18% 5% 2 4 2 3 3 3 4 7% 47%	3814
April	1st to 10th	Day	16% 7% 2 6% 4 3 4 3 5% 6% 45%	2090
	11th to 20th	Day	20% 5% 2 5% 3 4 4 4 5% 6% 44%	2173
	21st to end	Day	18% 7% 2 5% 4 4 4 3 4 5% 44%	2332
May	1st to 10th	Day	25% 7% 2 6% 4 4 4 3 4 6% 34%	4082
	11th to 20th	Day	16% 5% 2 5% 4 4 4 3 5% 7% 44%	4082
	21st to end	Day	14% 6% 2 6% 5% 5% 5% 4 6% 9% 39%	4477
June	1st to 10th	Day	8% 5% 2 5% 4 4 5% 4 6% 9% 47%	2470
	11th to 20th	Day	9% 5% 2 6% 5% 4 5% 4 6% 9% 45%	2470
	21st to end	Day	10% 6% 2 6% 6% 6% 6% 5% 6% 8% 39%	2470
July	1st to 10th	Day	9% 5% 2 5% 5% 5% 5% 4 5% 8% 47%	4120
	11th to 20th	Day	6% 4 2 6% 5% 5% 5% 4 7% 9% 48%	4120
	21st to end	Day	8% 6% 2 6% 4 5% 6% 5% 7% 10% 40%	4465
August	1st to 10th	Day	2 2 1 3 3 3 3 4 5% 9% 68%	3828
	11th to 20th	Day	4 3 1 4 3 4 4 3 6% 10% 59%	3726
	21st to end	Day	5% 4 1 5% 5% 5% 5% 4 6% 10% 49%	4101
September	1st to 10th	Day	12% 6% 3 7% 5% 6% 5% 4 6% 7% 40%	2090
	11th to 20th	Day	11% 7% 2 6% 5% 5% 5% 5% 6% 6% 42%	2090
	21st to end	Day	9% 4 3 5% 5% 4 5% 4 6% 7% 47%	2090
October	1st to 10th	Day	7% 5% 2 4 3 4 4 3 5% 7% 54%	2090
	11th to 20th	Day	16% 4 2 4 3 3 4 3 4 5% 51%	2043
	21st to end	Day	13% 4 2 4 3 3 2 2 3 4 57%	2090
November	1st to 10th	Day	19% 8% 2 5% 3 3 3 3 4 6% 45%	1948
	11th to 20th	Day	15% 7% 2 4 3 3 4 3 5% 5% 50%	1800
	21st to end	Day	18% 6% 3 5% 3 2 4 3 3 4 48%	1800
December	1st to 10th	Day	26% 9% 3 6% 3 3 2 2 3 5% 38%	2940
	11th to 20th	Day	18% 8% 2 5% 3 4 4 3 4 5% 44%	3391
	21st to end	Day	15% 6% 2 3 2 2 2 2 3 4 59%	4488
January	1st to 10th	Night	17% 5% 2 4 2 2 2 2 4 6% 54%	5888
	11th to 20th	Night	12% 4 1 2 2 2 2 3 4 5% 63%	5854
	21st to end	Night	29% 5% 2 4 2 2 2 2 4 4 42%	5984
February	1st to 10th	Night	17% 6% 1 4 3 2 2 2 4 5% 53%	2400
	11th to 20th	Night	20% 6% 1 4 3 2 2 2 3 4 51%	2338
	21st to end	Night	17% 6% 2 5% 3 3 4 2 4 7% 48%	1884
March	1st to 10th	Night	18% 8% 2 5% 3 3 3 3 4 5% 44%	3557
	11th to 20th	Night	22% 10% 3 7% 4 3 3 2 4 4 37%	3480
	21st to end	Night	18% 6% 2 4 3 3 4 3 4 5% 48%	3817
April	1st to 10th	Night	15% 6% 1 4 4 3 3 4 4 6% 49%	2090
	11th to 20th	Night	21% 6% 2 5% 3 2 3 3 3 5% 47%	1951
	21st to end	Night	21% 5% 2 4 3 3 3 3 3 5% 48%	1846
May	1st to 10th	Night	27% 7% 2 4 3 3 3 2 4 6% 39%	2823
	11th to 20th	Night	14% 5% 2 5% 3 3 3 3 4 6% 51%	2823
	21st to end	Night	16% 6% 2 4 4 3 4 2 5% 8% 47%	3090
June	1st to 10th	Night	6% 3 1 2 3 3 4 4 6% 9% 59%	1710
	11th to 20th	Night	7% 3 2 4 4 3 4 4 5% 8% 58%	1710
	21st to end	Night	9% 5% 1 4 3 4 3 4 5% 11% 52%	1710
July	1st to 10th	Night	6% 4 1 4 4 4 4 3 6% 10% 52%	2850
	11th to 20th	Night	5% 4 1 5% 4 4 4 4 7% 10% 52%	2850
	21st to end	Night	12% 7% 2 6% 3 4 4 4 6% 9% 43%	3098
August	1st to 10th	Night	2 2 1 3 2 2 2 2 4 7% 71%	3107
	11th to 20th	Night	4 2 1 3 3 3 4 3 6% 9% 61%	3113
	21st to end	Night	6% 5% 1 4 3 4 4 3 6% 10% 54%	3549
September	1st to 10th	Night	10% 6% 2 6% 4 5% 4 3 5% 8% 47%	2090
	11th to 20th	Night	11% 7% 2 6% 3 4 4 3 6% 7% 45%	2090
	21st to end	Night	8% 5% 2 6% 3 4 4 3 5% 8% 51%	2090
October	1st to 10th	Night	8% 4 1 5% 3 3 3 3 5% 5% 61%	2090
	11th to 20th	Night	15% 4 1 4 3 3 3 2 4 6% 54%	2116
	21st to end	Night	15% 4 2 3 2 2 2 1 3 4 63%	2508
November	1st to 10th	Night	16% 6% 2 4 3 3 2 2 3 6% 52%	2346
	11th to 20th	Night	12% 5% 2 4 3 3 3 2 5% 6% 56%	2600
	21st to end	Night	19% 5% 1 4 3 3 3 3 5% 7% 49%	2600
December	1st to 10th	Night	27% 8% 2 4 3 3 3 2 4 5% 39%	4250
	11th to 20th	Night	23% 7% 2 4 3 2 2 2 3 4 48%	4816
	21st to end	Night	18% 5% 2 3 2 2 2 2 3 5% 57%	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	34% 4 4 18% 25% 15%	4078
	11th to 20th	Day	33% 2 4 15% 24% 21%	4154
	21st to end	Day	43% 3 4 11% 25% 13%	4994
February	1st to 10th	Day	41% 3 5% 12% 21% 17%	2000
	11th to 20th	Day	42% 4 6% 16% 19% 14%	1959
	21st to end	Day	37% 3 7% 17% 19% 17%	1570
March	1st to 10th	Day	42% 4 6% 13% 22% 13%	3298
	11th to 20th	Day	54% 5% 5% 10% 16% 10%	3480
	21st to end	Day	36% 6% 10% 16% 18% 15%	3814
April	1st to 10th	Day	40% 4 8% 15% 18% 14%	2090
	11th to 20th	Day	41% 6% 6% 17% 17% 13%	2173
	21st to end	Day	42% 4 7% 18% 17% 12%	2332
May	1st to 10th	Day	49% 7% 9% 15% 13% 7%	4120
	11th to 20th	Day	38% 7% 10% 19% 19% 8%	4086
	21st to end	Day	38% 9% 12% 27% 11% 2	4489
June	1st to 10th	Day	30% 8% 14% 25% 19% 3	2470
	11th to 20th	Day	35% 6% 12% 25% 17% 6%	2470
	21st to end	Day	40% 8% 11% 24% 14% 4	2470
July	1st to 10th	Day	32% 7% 16% 37% 7% 1	4056
	11th to 20th	Day	29% 7% 18% 28% 16% 1	4051
	21st to end	Day	34% 8% 19% 28% 11% 1	4325
August	1st to 10th	Day	14% 5% 11% 43% 25% 1	3814
	11th to 20th	Day	20% 7% 22% 38% 12% 2	3762
	21st to end	Day	29% 9% 18% 24% 19% 2	4100
September	1st to 10th	Day	42% 7% 10% 17% 16% 7%	2090
	11th to 20th	Day	38% 9% 11% 19% 17% 5%	2090
	21st to end	Day	34% 6% 10% 22% 17% 11%	2090
October	1st to 10th	Day	19% 4 6% 12% 24% 35%	3480
	11th to 20th	Day	28% 4 8% 17% 22% 21%	3374
	21st to end	Day	28% 4 6% 15% 35% 13%	3428
November	1st to 10th	Day	41% 4 8% 19% 17% 12%	1948
	11th to 20th	Day	37% 4 6% 17% 19% 18%	1800
	21st to end	Day	41% 3 5% 16% 20% 14%	1800
December	1st to 10th	Day	51% 3 5% 16% 15% 10%	2940
	11th to 20th	Day	42% 5% 7% 14% 19% 14%	3389
	21st to end	Day	31% 3 4 16% 29% 18%	4488
January	1st to 10th	Night	31% 4 5% 18% 24% 17%	5888
	11th to 20th	Night	24% 3 4 18% 26% 25%	5854
	21st to end	Night	47% 3 3 10% 21% 16%	5984
February	1st to 10th	Night	35% 4 6% 13% 21% 21%	2400
	11th to 20th	Night	39% 3 5% 17% 20% 16%	2338
	21st to end	Night	38% 4 6% 16% 19% 17%	1884
March	1st to 10th	Night	41% 5% 7% 15% 20% 12%	3557
	11th to 20th	Night	48% 7% 7% 12% 13% 12%	3480
	21st to end	Night	37% 6% 10% 15% 18% 14%	3817
April	1st to 10th	Night	34% 5% 11% 17% 17% 16%	2090
	11th to 20th	Night	40% 4 9% 13% 17% 17%	1951
	21st to end	Night	41% 4 9% 19% 16% 12%	1846
May	1st to 10th	Night	44% 7% 10% 17% 12% 10%	2850
	11th to 20th	Night	33% 7% 10% 22% 19% 8%	2824
	21st to end	Night	36% 7% 13% 28% 12% 4	3099
June	1st to 10th	Night	21% 6% 19% 31% 20% 3	1710
	11th to 20th	Night	24% 6% 15% 28% 21% 5%	1710
	21st to end	Night	29% 7% 18% 28% 15% 3	1710
July	1st to 10th	Night	25% 7% 24% 37% 5% 1	2805
	11th to 20th	Night	25% 9% 21% 28% 16% 2	2796
	21st to end	Night	35% 8% 22% 26% 8% 1	2999
August	1st to 10th	Night	13% 5% 16% 44% 21%	3097
	11th to 20th	Night	19% 7% 29% 36% 8% 1	3143
	21st to end	Night	25% 11% 21% 25% 17% 2	3549
September	1st to 10th	Night	35% 6% 14% 21% 16% 7%	2090
	11th to 20th	Night	35% 8% 16% 21% 14% 5%	2090
	21st to end	Night	31% 6% 12% 22% 18% 12%	2090
October	1st to 10th	Night	17% 3 7% 15% 21% 36%	3480
	11th to 20th	Night	25% 3 9% 13% 30% 19%	3511
	21st to end	Night	26% 3 6% 17% 34% 15%	4120
November	1st to 10th	Night	34% 4 7% 19% 21% 14%	2346
	11th to 20th	Night	31% 4 9% 19% 21% 18%	2600
	21st to end	Night	36% 4 8% 16% 19% 16%	2600
December	1st to 10th	Night	49% 4 7% 14% 14% 13%	4250
	11th to 20th	Night	42% 3 5% 11% 20% 18%	4817
	21st to end	Night	32% 3 4 14% 28% 18%	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	24% 13% 32% 24% 6%	300
	11th to 20th	Day	24% 17% 27% 24% 8%	300
	21st to end	Day	22% 17% 32% 22% 8%	330
February	1st to 10th	Day	29% 13% 25% 24% 9%	300
	11th to 20th	Day	26% 20% 32% 16% 6%	300
	21st to end	Day	24% 19% 36% 17% 4	225
March	1st to 10th	Day	26% 14% 40% 17% 3	270
	11th to 20th	Day	19% 19% 41% 17% 4	270
	21st to end	Day	22% 18% 42% 16% 2	297
April	1st to 10th	Day	23% 17% 34% 23% 3	270
	11th to 20th	Day	18% 17% 38% 24% 4	371
	21st to end	Day	19% 13% 42% 22% 3	512
May	1st to 10th	Day	21% 10% 36% 27% 6%	653
	11th to 20th	Day	19% 8% 32% 31% 8% 2	675
	21st to end	Day	19% 6% 31% 32% 11% 1	734
June	1st to 10th	Day	8% 2 21% 43% 24% 3	680
	11th to 20th	Day	10% 2 19% 45% 22% 2	680
	21st to end	Day	10% 1 16% 39% 28% 6%	680
July	1st to 10th	Day	12% 2 11% 34% 33% 7%	671
	11th to 20th	Day	7% 1 6% 35% 44% 6%	668
	21st to end	Day	5% 2 8% 33% 42% 10%	739
August	1st to 10th	Day	3 3 37% 44% 13%	517
	11th to 20th	Day	5% 1 6% 37% 40% 11%	477
	21st to end	Day	6% 1 7% 30% 41% 15%	499
September	1st to 10th	Day	11% 2 9% 27% 36% 14%	300
	11th to 20th	Day	8% 4 29% 44% 14%	300
	21st to end	Day	7% 1 11% 30% 41% 10%	300
October	1st to 10th	Day	7% 2 16% 36% 33% 6%	300
	11th to 20th	Day	13% 4 21% 41% 18% 4	300
	21st to end	Day	16% 14% 25% 27% 15% 2	330
November	1st to 10th	Day	23% 7% 28% 25% 15% 3	300
	11th to 20th	Day	22% 9% 26% 27% 12% 3	300
	21st to end	Day	23% 16% 33% 18% 10% 1	300
December	1st to 10th	Day	20% 13% 27% 26% 11% 3	300
	11th to 20th	Day	23% 15% 27% 25% 9%	300
	21st to end	Day	22% 11% 32% 25% 9%	330
January	1st to 10th	Night	19% 8% 26% 36% 10%	1000
	11th to 20th	Night	20% 10% 29% 33% 8%	980
	21st to end	Night	24% 8% 26% 33% 8%	880
February	1st to 10th	Night	23% 12% 27% 31% 8%	800
	11th to 20th	Night	27% 10% 30% 27% 6%	784
	21st to end	Night	22% 11% 38% 28% 2	628
March	1st to 10th	Night	23% 11% 33% 28% 4 1	661
	11th to 20th	Night	20% 12% 33% 31% 4	570
	21st to end	Night	19% 12% 38% 26% 5%	627
April	1st to 10th	Night	14% 11% 41% 31% 3	570
	11th to 20th	Night	21% 10% 43% 24% 2	563
	21st to end	Night	21% 11% 40% 23% 5%	570
May	1st to 10th	Night	17% 10% 41% 27% 5%	570
	11th to 20th	Night	17% 7% 36% 33% 7% 1	561
	21st to end	Night	17% 7% 32% 35% 8%	617
June	1st to 10th	Night	6% 2 26% 46% 18% 1	570
	11th to 20th	Night	7% 2 32% 46% 14%	570
	21st to end	Night	8% 3 20% 46% 22% 1	570
July	1st to 10th	Night	9% 3 12% 47% 28% 1	555
	11th to 20th	Night	4 1 13% 52% 30% 1	552
	21st to end	Night	7% 2 9% 50% 31% 2	624
August	1st to 10th	Night	2 1 9% 48% 38% 2	567
	11th to 20th	Night	5% 8% 52% 32% 3	564
	21st to end	Night	6% 2 8% 39% 41% 4	627
September	1st to 10th	Night	11% 1 9% 42% 32% 5%	570
	11th to 20th	Night	11% 1 9% 42% 34% 2	570
	21st to end	Night	10% 2 12% 42% 30% 4	570
October	1st to 10th	Night	8% 2 12% 50% 27% 2	570
	11th to 20th	Night	15% 3 21% 40% 17% 3	596
	21st to end	Night	16% 7% 22% 30% 23% 2	836
November	1st to 10th	Night	15% 7% 20% 37% 20% 2	786
	11th to 20th	Night	15% 7% 20% 41% 16% 2	1000
	21st to end	Night	22% 10% 23% 33% 12% 1	1000
December	1st to 10th	Night	21% 7% 22% 37% 12% 1	1000
	11th to 20th	Night	25% 10% 24% 32% 10%	1000
	21st to end	Night	20% 8% 25% 37% 9% 1	1100

Page generated at 2025-02-18 02:26:29. Version ac07

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