Boerne
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Boerne clear sky chart from 2005-11-06 to 2025-02-06.

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	13% 6% 2 5% 4 4 4 3 5% 7% 46%	109063
	Night	15% 6% 2 5% 3 3 3 3 4 6% 50%	109444
Transparency	Day	36% 5% 9% 21% 19% 10%	112907
	Night	34% 5% 10% 19% 19% 13%	113727
Seeing	Day	16% 8% 25% 31% 17% 3	15064
	Night	17% 8% 27% 35% 13% 1	25140

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	15% 8% 3 6% 3 3 3 2 3 4 51%	4077
	11th to 20th	Day	15% 6% 2 4 3 2 3 2 5% 5% 54%	4080
	21st to end	Day	22% 8% 2 6% 2 2 2 2 4 7% 44%	4969
February	1st to 10th	Day	16% 8% 2 6% 4 4 3 2 4 5% 47%	1950
	11th to 20th	Day	17% 8% 2 5% 4 3 4 3 4 5% 45%	1849
	21st to end	Day	17% 6% 2 4 3 3 2 3 4 5% 50%	1570
March	1st to 10th	Day	17% 8% 2 6% 3 4 4 3 4 5% 44%	3337
	11th to 20th	Day	23% 9% 3 8% 4 4 4 3 4 4 33%	3480
	21st to end	Day	16% 7% 2 5% 3 3 4 3 5% 7% 45%	3814
April	1st to 10th	Day	15% 7% 3 6% 4 4 3 3 5% 6% 45%	2090
	11th to 20th	Day	21% 6% 2 5% 4 4 3 3 5% 5% 42%	2124
	21st to end	Day	17% 7% 2 6% 5% 4 4 3 3 6% 44%	2372
May	1st to 10th	Day	24% 8% 3 7% 4 4 4 4 4 5% 33%	4082
	11th to 20th	Day	16% 5% 2 6% 5% 4 4 3 5% 7% 43%	4082
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 4 7% 9% 39%	4477
June	1st to 10th	Day	7% 5% 2 4 5% 4 6% 5% 6% 10% 47%	2470
	11th to 20th	Day	9% 6% 2 5% 5% 5% 5% 4 6% 8% 46%	2470
	21st to end	Day	9% 5% 2 6% 6% 6% 6% 6% 6% 9% 38%	2470
July	1st to 10th	Day	8% 5% 2 6% 5% 5% 6% 4 6% 8% 45%	4120
	11th to 20th	Day	5% 4 2 5% 4 4 6% 4 7% 11% 48%	4120
	21st to end	Day	8% 6% 2 7% 6% 6% 6% 5% 8% 9% 37%	4465
August	1st to 10th	Day	1 2 1 2 2 3 3 3 5% 9% 68%	3946
	11th to 20th	Day	4 2 1 3 3 3 4 3 6% 12% 57%	3726
	21st to end	Day	5% 4 2 6% 5% 5% 6% 5% 7% 11% 45%	4062
September	1st to 10th	Day	13% 7% 3 6% 4 5% 5% 4 5% 6% 42%	2090
	11th to 20th	Day	13% 6% 2 6% 5% 4 5% 4 6% 8% 40%	2090
	21st to end	Day	9% 5% 2 6% 4 4 6% 4 5% 7% 48%	2090
October	1st to 10th	Day	7% 4 2 5% 5% 4 4 3 5% 7% 54%	2090
	11th to 20th	Day	14% 5% 1 4 3 3 4 3 4 6% 51%	2009
	21st to end	Day	12% 4 2 5% 3 3 3 3 3 5% 57%	2090
November	1st to 10th	Day	16% 8% 3 5% 4 3 3 4 4 6% 44%	1958
	11th to 20th	Day	13% 6% 2 5% 4 3 4 4 5% 6% 49%	1825
	21st to end	Day	17% 7% 3 5% 4 3 3 3 4 6% 46%	1800
December	1st to 10th	Day	27% 8% 3 6% 3 2 2 2 3 6% 38%	2940
	11th to 20th	Day	15% 8% 2 6% 5% 3 4 3 4 5% 44%	3391
	21st to end	Day	13% 6% 2 4 3 2 3 2 3 4 59%	4488
January	1st to 10th	Night	17% 6% 3 5% 2 2 3 2 3 5% 52%	5888
	11th to 20th	Night	11% 4 1 2 2 2 3 3 4 5% 63%	5900
	21st to end	Night	28% 7% 2 5% 3 2 2 2 3 4 41%	6052
February	1st to 10th	Night	16% 7% 3 4 3 3 3 3 4 5% 50%	2340
	11th to 20th	Night	17% 8% 2 5% 3 3 3 2 3 5% 50%	2218
	21st to end	Night	18% 7% 2 5% 3 3 3 2 4 6% 47%	1884
March	1st to 10th	Night	18% 9% 2 6% 4 3 4 3 4 5% 42%	3517
	11th to 20th	Night	22% 11% 2 7% 5% 4 3 3 3 5% 35%	3480
	21st to end	Night	19% 6% 2 5% 3 3 3 3 4 6% 46%	3817
April	1st to 10th	Night	13% 6% 2 6% 4 3 4 2 5% 7% 47%	2090
	11th to 20th	Night	20% 7% 3 6% 3 2 3 3 4 5% 46%	2001
	21st to end	Night	20% 6% 2 5% 3 3 3 2 4 5% 46%	1805
May	1st to 10th	Night	26% 9% 2 5% 2 2 3 3 4 5% 38%	2823
	11th to 20th	Night	14% 6% 2 5% 4 3 4 3 4 6% 50%	2823
	21st to end	Night	16% 6% 2 4 4 3 4 4 5% 8% 45%	3090
June	1st to 10th	Night	7% 4 2 4 2 3 3 3 6% 8% 59%	1710
	11th to 20th	Night	6% 4 2 4 4 4 3 3 5% 9% 57%	1710
	21st to end	Night	8% 5% 1 4 4 5% 4 3 6% 10% 49%	1710
July	1st to 10th	Night	7% 4 1 4 3 4 4 4 7% 9% 52%	2850
	11th to 20th	Night	3 4 2 5% 4 4 4 5% 8% 9% 53%	2850
	21st to end	Night	9% 9% 2 7% 4 4 5% 5% 6% 9% 40%	3098
August	1st to 10th	Night	1 2 2 2 2 3 3 5% 8% 73%	2988
	11th to 20th	Night	3 2 1 3 2 3 4 3 6% 12% 59%	3113
	21st to end	Night	5% 5% 2 4 3 3 4 4 6% 10% 53%	3601
September	1st to 10th	Night	9% 6% 2 6% 5% 4 5% 3 6% 7% 48%	2090
	11th to 20th	Night	11% 7% 2 5% 4 4 4 5% 6% 8% 45%	2090
	21st to end	Night	9% 5% 2 6% 3 3 4 4 6% 7% 51%	2090
October	1st to 10th	Night	7% 4 1 4 3 2 3 3 5% 6% 61%	2090
	11th to 20th	Night	13% 5% 2 4 3 3 3 3 4 5% 54%	2152
	21st to end	Night	15% 5% 1 3 2 2 2 2 3 3 61%	2508
November	1st to 10th	Night	14% 7% 2 5% 3 3 2 3 2 5% 52%	2340
	11th to 20th	Night	11% 6% 2 4 3 4 3 2 4 6% 54%	2570
	21st to end	Night	18% 6% 1 3 3 3 3 3 4 7% 48%	2600
December	1st to 10th	Night	23% 10% 2 6% 3 3 3 3 4 5% 38%	4250
	11th to 20th	Night	19% 9% 2 6% 3 2 2 2 2 4 47%	4816
	21st to end	Night	16% 6% 2 4 2 2 2 2 2 4 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	36% 3 5% 18% 23% 13%	4078
	11th to 20th	Day	34% 1 5% 15% 25% 20%	4080
	21st to end	Day	44% 2 4 11% 25% 14%	4969
February	1st to 10th	Day	42% 3 6% 12% 22% 16%	1950
	11th to 20th	Day	41% 4 6% 17% 18% 14%	1859
	21st to end	Day	38% 3 7% 17% 19% 16%	1570
March	1st to 10th	Day	43% 4 7% 13% 22% 12%	3337
	11th to 20th	Day	54% 5% 5% 10% 15% 10%	3480
	21st to end	Day	38% 4 10% 15% 19% 13%	3814
April	1st to 10th	Day	41% 4 9% 17% 17% 12%	2090
	11th to 20th	Day	43% 5% 6% 17% 17% 12%	2124
	21st to end	Day	43% 4 6% 19% 18% 10%	2372
May	1st to 10th	Day	52% 5% 9% 14% 14% 6%	4120
	11th to 20th	Day	39% 6% 9% 18% 20% 7%	4086
	21st to end	Day	39% 8% 11% 29% 11% 2	4489
June	1st to 10th	Day	31% 8% 12% 26% 20% 3	2470
	11th to 20th	Day	35% 6% 11% 25% 19% 4	2470
	21st to end	Day	41% 7% 11% 24% 14% 4	2470
July	1st to 10th	Day	33% 8% 15% 37% 6% 1	4056
	11th to 20th	Day	28% 8% 18% 30% 15% 1	4051
	21st to end	Day	37% 9% 17% 29% 9%	4325
August	1st to 10th	Day	14% 4 12% 45% 26%	3932
	11th to 20th	Day	20% 6% 23% 38% 11% 2	3762
	21st to end	Day	31% 9% 17% 24% 18% 2	4061
September	1st to 10th	Day	41% 6% 10% 19% 16% 8%	2090
	11th to 20th	Day	39% 8% 11% 19% 18% 5%	2090
	21st to end	Day	33% 6% 10% 21% 17% 12%	2090
October	1st to 10th	Day	19% 3 6% 12% 25% 35%	3480
	11th to 20th	Day	27% 3 8% 18% 22% 22%	3314
	21st to end	Day	27% 4 5% 16% 34% 13%	3428
November	1st to 10th	Day	41% 4 7% 19% 17% 12%	1958
	11th to 20th	Day	36% 4 7% 16% 20% 16%	1825
	21st to end	Day	41% 4 6% 17% 20% 14%	1800
December	1st to 10th	Day	50% 3 5% 19% 13% 10%	2940
	11th to 20th	Day	41% 5% 7% 13% 20% 14%	3389
	21st to end	Day	31% 2 5% 15% 29% 18%	4488
January	1st to 10th	Night	34% 3 6% 17% 23% 15%	5888
	11th to 20th	Night	24% 3 4 19% 27% 23%	5900
	21st to end	Night	47% 3 3 10% 21% 16%	6052
February	1st to 10th	Night	37% 4 6% 13% 22% 19%	2340
	11th to 20th	Night	39% 2 6% 16% 20% 17%	2218
	21st to end	Night	39% 4 6% 16% 19% 16%	1884
March	1st to 10th	Night	44% 3 8% 15% 19% 11%	3517
	11th to 20th	Night	51% 6% 7% 11% 13% 11%	3480
	21st to end	Night	40% 4 10% 16% 19% 12%	3817
April	1st to 10th	Night	38% 4 9% 19% 15% 15%	2090
	11th to 20th	Night	42% 4 9% 13% 17% 16%	2001
	21st to end	Night	42% 4 8% 20% 17% 10%	1805
May	1st to 10th	Night	49% 5% 8% 17% 12% 9%	2850
	11th to 20th	Night	34% 7% 10% 22% 19% 8%	2824
	21st to end	Night	38% 6% 13% 28% 11% 4	3099
June	1st to 10th	Night	23% 6% 17% 31% 20% 3	1710
	11th to 20th	Night	25% 5% 15% 30% 21% 5%	1710
	21st to end	Night	30% 6% 17% 28% 15% 3	1710
July	1st to 10th	Night	25% 9% 24% 35% 5% 1	2805
	11th to 20th	Night	24% 9% 21% 29% 15% 1	2796
	21st to end	Night	37% 8% 22% 25% 7% 1	2999
August	1st to 10th	Night	12% 4 16% 46% 21%	2978
	11th to 20th	Night	18% 8% 31% 33% 8% 2	3143
	21st to end	Night	26% 11% 21% 25% 16% 2	3601
September	1st to 10th	Night	34% 6% 16% 20% 16% 8%	2090
	11th to 20th	Night	35% 8% 16% 21% 15% 5%	2090
	21st to end	Night	30% 7% 12% 22% 18% 12%	2090
October	1st to 10th	Night	16% 3 8% 15% 21% 37%	3480
	11th to 20th	Night	24% 3 9% 15% 30% 19%	3573
	21st to end	Night	26% 3 6% 17% 33% 15%	4120
November	1st to 10th	Night	36% 4 7% 18% 21% 14%	2340
	11th to 20th	Night	32% 4 9% 19% 20% 18%	2570
	21st to end	Night	38% 4 8% 16% 20% 15%	2600
December	1st to 10th	Night	49% 3 7% 15% 14% 12%	4250
	11th to 20th	Night	43% 3 5% 10% 20% 18%	4817
	21st to end	Night	33% 2 4 14% 28% 19%	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% 19% 36% 19% 3	300
	11th to 20th	Day	26% 17% 32% 19% 5%	300
	21st to end	Day	24% 17% 36% 18% 5%	330
February	1st to 10th	Day	27% 17% 29% 22% 4	285
	11th to 20th	Day	27% 21% 38% 11% 3	270
	21st to end	Day	27% 21% 41% 10% 1	225
March	1st to 10th	Day	23% 18% 44% 14%	270
	11th to 20th	Day	21% 21% 41% 14% 3	270
	21st to end	Day	23% 18% 42% 15% 2 1	297
April	1st to 10th	Day	24% 17% 42% 14% 1	270
	11th to 20th	Day	24% 19% 34% 20% 3	322
	21st to end	Day	20% 16% 42% 20% 3	552
May	1st to 10th	Day	23% 10% 38% 23% 5%	653
	11th to 20th	Day	20% 10% 31% 32% 6% 1	675
	21st to end	Day	20% 5% 34% 29% 11% 1	734
June	1st to 10th	Day	9% 3 22% 44% 19% 3	680
	11th to 20th	Day	10% 3 22% 46% 17% 2	680
	21st to end	Day	9% 4 17% 40% 26% 5%	680
July	1st to 10th	Day	11% 2 13% 38% 29% 8%	671
	11th to 20th	Day	7% 1 8% 42% 38% 4	668
	21st to end	Day	6% 2 8% 41% 36% 7%	739
August	1st to 10th	Day	3 1 5% 46% 38% 8%	583
	11th to 20th	Day	6% 2 6% 43% 36% 7%	477
	21st to end	Day	5% 3 5% 36% 38% 12%	473
September	1st to 10th	Day	14% 1 9% 32% 35% 9%	300
	11th to 20th	Day	9% 1 6% 36% 39% 9%	300
	21st to end	Day	8% 2 9% 39% 33% 8%	300
October	1st to 10th	Day	7% 2 17% 41% 27% 6%	300
	11th to 20th	Day	11% 3 27% 40% 17% 2	300
	21st to end	Day	20% 11% 28% 25% 14% 3	330
November	1st to 10th	Day	20% 6% 32% 29% 11% 2	300
	11th to 20th	Day	21% 10% 33% 23% 10% 3	300
	21st to end	Day	27% 17% 31% 15% 8% 1	300
December	1st to 10th	Day	20% 12% 35% 24% 8% 2	300
	11th to 20th	Day	22% 16% 35% 19% 6% 1	300
	21st to end	Day	21% 14% 35% 24% 6% 1	330
January	1st to 10th	Night	20% 11% 29% 32% 8%	1000
	11th to 20th	Night	22% 14% 30% 29% 6%	1000
	21st to end	Night	24% 11% 31% 28% 6%	909
February	1st to 10th	Night	23% 13% 31% 26% 6%	780
	11th to 20th	Night	27% 13% 33% 24% 3	744
	21st to end	Night	26% 14% 39% 19% 1	628
March	1st to 10th	Night	25% 10% 37% 25% 2	634
	11th to 20th	Night	24% 9% 39% 24% 4	570
	21st to end	Night	19% 13% 44% 22% 3	627
April	1st to 10th	Night	16% 14% 42% 25% 4	570
	11th to 20th	Night	24% 12% 39% 23% 2	563
	21st to end	Night	21% 10% 44% 19% 5% 1	570
May	1st to 10th	Night	20% 10% 42% 26% 3	570
	11th to 20th	Night	17% 8% 37% 31% 7% 1	561
	21st to end	Night	17% 7% 37% 30% 9%	617
June	1st to 10th	Night	8% 1 29% 43% 17% 1	570
	11th to 20th	Night	8% 2 36% 44% 10% 1	570
	21st to end	Night	8% 2 24% 45% 18% 3	570
July	1st to 10th	Night	11% 1 17% 46% 22% 2	555
	11th to 20th	Night	4 1 12% 58% 22% 3	552
	21st to end	Night	6% 1 12% 56% 22% 3	624
August	1st to 10th	Night	2 1 12% 54% 28% 2	567
	11th to 20th	Night	5% 2 9% 53% 27% 3	564
	21st to end	Night	8% 2 6% 47% 32% 5%	627
September	1st to 10th	Night	11% 2 10% 44% 29% 4	570
	11th to 20th	Night	14% 2 9% 40% 33% 3	570
	21st to end	Night	12% 2 10% 41% 30% 4	570
October	1st to 10th	Night	8% 1 14% 48% 25% 4	570
	11th to 20th	Night	15% 5% 21% 39% 19% 1	632
	21st to end	Night	16% 9% 26% 28% 19% 2	836
November	1st to 10th	Night	17% 6% 22% 38% 15% 2	780
	11th to 20th	Night	15% 7% 26% 37% 14% 1	970
	21st to end	Night	23% 11% 25% 29% 11% 1	1000
December	1st to 10th	Night	21% 9% 27% 33% 9% 1	1000
	11th to 20th	Night	25% 10% 27% 30% 7%	1000
	21st to end	Night	20% 10% 29% 33% 7%	1100

Page generated at 2025-02-03 02:05:49. Version ac07

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