Pearsall City Hall
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pearsall City Hall clear sky chart from 2005-11-06 to 2026-06-01.

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	12% 5% 2 5% 4 4 4 3 5% 7% 49%	132578
	Night	12% 5% 2 4 3 3 3 3 5% 7% 53%	130908
Transparency	Day	34% 5% 10% 22% 18% 11%	136410
	Night	31% 5% 11% 21% 19% 13%	135128
Seeing	Day	12% 4 19% 32% 25% 8%	16686
	Night	13% 5% 26% 40% 15% 1	26707

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	14% 5% 1 4 3 2 3 2 3 5% 57%	5289
	11th to 20th	Day	14% 5% 2 6% 3 2 2 2 4 4 55%	5507
	21st to end	Day	23% 8% 2 4 3 2 3 2 5% 7% 42%	6468
February	1st to 10th	Day	17% 8% 2 6% 4 3 3 2 4 5% 47%	2100
	11th to 20th	Day	17% 8% 2 5% 2 2 3 3 4 7% 47%	2049
	21st to end	Day	15% 5% 2 4 3 3 2 3 4 6% 53%	1730
March	1st to 10th	Day	12% 6% 2 4 3 3 3 3 5% 6% 52%	4865
	11th to 20th	Day	14% 6% 2 5% 4 3 3 3 3 5% 54%	5090
	21st to end	Day	16% 7% 2 5% 3 3 3 3 4 6% 49%	5583
April	1st to 10th	Day	13% 7% 2 5% 5% 4 3 3 4 7% 47%	2310
	11th to 20th	Day	15% 6% 2 6% 4 5% 4 3 5% 5% 45%	2370
	21st to end	Day	14% 6% 2 6% 4 4 3 3 5% 6% 45%	2562
May	1st to 10th	Day	17% 6% 3 7% 5% 4 4 4 6% 8% 37%	5992
	11th to 20th	Day	8% 4 1 5% 4 4 4 4 6% 8% 51%	5992
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 4 7% 10% 42%	6577
June	1st to 10th	Day	4 3 1 4 3 4 5% 4 8% 10% 53%	2601
	11th to 20th	Day	5% 3 2 5% 5% 5% 5% 5% 7% 9% 51%	2600
	21st to end	Day	7% 4 1 5% 6% 5% 6% 5% 8% 11% 42%	2600
July	1st to 10th	Day	12% 7% 3 7% 5% 5% 5% 4 5% 8% 40%	5900
	11th to 20th	Day	6% 4 2 6% 4 5% 5% 5% 6% 9% 46%	5900
	21st to end	Day	5% 4 2 6% 5% 5% 5% 4 7% 10% 47%	6408
August	1st to 10th	Day	1 1 1 2 3 3 3 3 5% 7% 72%	3905
	11th to 20th	Day	3 2 1 3 3 3 4 3 7% 10% 62%	3846
	21st to end	Day	5% 3 1 5% 4 5% 6% 5% 7% 10% 50%	4213
September	1st to 10th	Day	10% 5% 2 8% 6% 5% 5% 4 6% 9% 41%	2200
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 4 6% 8% 43%	2200
	21st to end	Day	7% 4 2 4 4 4 5% 4 7% 8% 50%	2200
October	1st to 10th	Day	6% 5% 2 5% 4 3 4 3 6% 6% 58%	2200
	11th to 20th	Day	12% 5% 2 4 3 4 3 3 5% 6% 53%	2157
	21st to end	Day	10% 4 2 4 3 3 3 3 3 5% 61%	2200
November	1st to 10th	Day	15% 7% 2 6% 3 3 3 2 4 6% 48%	2058
	11th to 20th	Day	13% 5% 2 5% 3 4 3 3 5% 6% 52%	1918
	21st to end	Day	18% 6% 2 5% 4 3 3 3 4 6% 46%	1890
December	1st to 10th	Day	31% 9% 4 6% 3 2 2 2 3 4 34%	3030
	11th to 20th	Day	16% 7% 2 7% 4 4 4 3 5% 6% 43%	3481
	21st to end	Day	11% 6% 2 5% 3 2 3 2 3 5% 58%	4587
January	1st to 10th	Night	15% 5% 2 4 3 2 3 2 4 6% 55%	7634
	11th to 20th	Night	13% 4 1 3 2 3 3 2 3 4 61%	7526
	21st to end	Night	27% 5% 2 5% 3 2 3 2 4 5% 43%	7746
February	1st to 10th	Night	13% 5% 2 4 3 3 3 3 5% 6% 53%	2520
	11th to 20th	Night	18% 5% 2 5% 3 2 3 2 3 5% 51%	2458
	21st to end	Night	13% 7% 2 5% 3 3 4 3 5% 6% 50%	2076
March	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 4 6% 49%	5217
	11th to 20th	Night	13% 5% 3 5% 3 2 2 2 4 5% 56%	5090
	21st to end	Night	15% 6% 2 5% 3 3 3 3 5% 5% 52%	5588
April	1st to 10th	Night	10% 5% 2 5% 4 3 4 4 6% 9% 49%	2310
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 5% 7% 49%	2194
	21st to end	Night	15% 7% 2 5% 3 4 3 3 4 6% 47%	2056
May	1st to 10th	Night	19% 7% 3 6% 3 4 4 3 4 6% 41%	4143
	11th to 20th	Night	8% 4 2 5% 3 3 5% 3 6% 9% 52%	4143
	21st to end	Night	9% 4 2 6% 4 4 5% 4 7% 11% 43%	4542
June	1st to 10th	Night	3 2 1 3 4 3 4 4 6% 10% 62%	1800
	11th to 20th	Night	3 2 1 4 3 5% 3 4 5% 10% 61%	1800
	21st to end	Night	5% 4 1 4 4 4 5% 4 7% 8% 54%	1800
July	1st to 10th	Night	8% 5% 2 6% 4 5% 4 5% 7% 10% 44%	4078
	11th to 20th	Night	4 4 2 4 4 4 4 4 6% 10% 55%	4077
	21st to end	Night	5% 4 2 5% 3 4 4 4 7% 9% 53%	4449
August	1st to 10th	Night	1 1 2 2 2 2 3 4 7% 77%	3251
	11th to 20th	Night	3 2 1 3 3 3 4 3 7% 12% 61%	3213
	21st to end	Night	4 3 1 4 3 3 4 4 7% 11% 56%	3690
September	1st to 10th	Night	7% 4 2 7% 5% 5% 5% 5% 6% 9% 45%	2200
	11th to 20th	Night	9% 5% 3 6% 4 4 5% 4 5% 9% 47%	2200
	21st to end	Night	7% 4 1 4 3 4 4 4 6% 9% 54%	2200
October	1st to 10th	Night	4 3 1 4 3 3 3 3 4 7% 66%	2200
	11th to 20th	Night	10% 4 1 4 2 2 4 2 4 6% 60%	2220
	21st to end	Night	12% 3 1 3 2 2 2 2 3 4 65%	2640
November	1st to 10th	Night	13% 4 2 5% 4 3 3 2 4 5% 56%	2460
	11th to 20th	Night	10% 4 2 5% 3 3 3 3 5% 6% 57%	2698
	21st to end	Night	15% 6% 2 4 4 4 3 3 5% 6% 48%	2730
December	1st to 10th	Night	32% 8% 3 5% 2 2 2 2 3 4 36%	4380
	11th to 20th	Night	15% 7% 2 6% 4 3 3 3 4 5% 48%	4946
	21st to end	Night	12% 5% 2 4 3 2 3 3 4 6% 57%	6633

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	32% 3 7% 20% 24% 14%	5290
	11th to 20th	Day	35% 2 3 14% 25% 22%	5507
	21st to end	Day	44% 3 5% 15% 24% 10%	6468
February	1st to 10th	Day	41% 3 6% 12% 20% 18%	2100
	11th to 20th	Day	39% 3 7% 17% 20% 13%	2059
	21st to end	Day	34% 3 8% 17% 22% 16%	1730
March	1st to 10th	Day	33% 3 6% 19% 15% 23%	4865
	11th to 20th	Day	35% 4 5% 8% 16% 32%	5090
	21st to end	Day	37% 4 7% 21% 18% 14%	5585
April	1st to 10th	Day	38% 5% 9% 17% 17% 15%	2310
	11th to 20th	Day	40% 5% 8% 17% 16% 13%	2370
	21st to end	Day	40% 6% 7% 19% 16% 12%	2562
May	1st to 10th	Day	45% 6% 10% 20% 14% 6%	6030
	11th to 20th	Day	30% 6% 12% 24% 18% 10%	5996
	21st to end	Day	36% 6% 10% 31% 16% 1	6590
June	1st to 10th	Day	22% 9% 15% 30% 20% 4	2601
	11th to 20th	Day	27% 7% 13% 26% 21% 5%	2600
	21st to end	Day	33% 10% 14% 26% 14% 3	2600
July	1st to 10th	Day	42% 7% 14% 30% 6% 1	5836
	11th to 20th	Day	33% 7% 17% 29% 13% 1	5831
	21st to end	Day	30% 7% 17% 28% 16% 2	6226
August	1st to 10th	Day	12% 4 12% 44% 26% 2	3892
	11th to 20th	Day	17% 6% 22% 41% 12% 2	3882
	21st to end	Day	27% 9% 18% 25% 19% 2	4212
September	1st to 10th	Day	40% 7% 13% 19% 15% 7%	2200
	11th to 20th	Day	37% 8% 11% 23% 17% 4	2200
	21st to end	Day	30% 7% 11% 24% 17% 12%	2200
October	1st to 10th	Day	17% 3 6% 14% 23% 37%	3590
	11th to 20th	Day	27% 4 9% 17% 20% 23%	3488
	21st to end	Day	24% 3 7% 17% 32% 17%	3538
November	1st to 10th	Day	38% 4 7% 17% 20% 13%	2058
	11th to 20th	Day	33% 4 8% 18% 20% 17%	1918
	21st to end	Day	41% 5% 5% 17% 19% 13%	1890
December	1st to 10th	Day	56% 2 5% 12% 15% 10%	3030
	11th to 20th	Day	42% 5% 7% 15% 17% 15%	3479
	21st to end	Day	31% 3 4 18% 27% 16%	4587
January	1st to 10th	Night	32% 3 8% 18% 22% 17%	7635
	11th to 20th	Night	29% 2 3 16% 27% 23%	7526
	21st to end	Night	46% 3 4 14% 21% 13%	7746
February	1st to 10th	Night	32% 4 8% 14% 18% 22%	2520
	11th to 20th	Night	37% 3 6% 19% 19% 16%	2458
	21st to end	Night	35% 4 7% 17% 21% 17%	2076
March	1st to 10th	Night	36% 5% 8% 18% 14% 18%	5217
	11th to 20th	Night	33% 4 7% 13% 14% 29%	5090
	21st to end	Night	34% 4 11% 21% 19% 12%	5588
April	1st to 10th	Night	31% 5% 13% 19% 16% 15%	2310
	11th to 20th	Night	35% 5% 12% 16% 15% 17%	2194
	21st to end	Night	38% 6% 11% 17% 16% 11%	2056
May	1st to 10th	Night	43% 5% 9% 18% 16% 8%	4170
	11th to 20th	Night	28% 6% 12% 19% 21% 13%	4144
	21st to end	Night	33% 8% 15% 30% 13% 1	4551
June	1st to 10th	Night	18% 6% 18% 34% 21% 2	1800
	11th to 20th	Night	19% 6% 13% 32% 26% 5%	1800
	21st to end	Night	26% 8% 22% 27% 15% 3	1800
July	1st to 10th	Night	35% 9% 24% 27% 5%	4035
	11th to 20th	Night	24% 7% 24% 31% 12% 1	4026
	21st to end	Night	25% 7% 22% 30% 13% 2	4320
August	1st to 10th	Night	9% 4 15% 48% 24% 1	3241
	11th to 20th	Night	16% 7% 31% 38% 8% 1	3243
	21st to end	Night	22% 10% 24% 28% 14% 2	3690
September	1st to 10th	Night	35% 9% 16% 18% 15% 7%	2200
	11th to 20th	Night	33% 8% 15% 23% 18% 3	2200
	21st to end	Night	25% 8% 13% 25% 18% 12%	2200
October	1st to 10th	Night	14% 3 8% 18% 20% 37%	3590
	11th to 20th	Night	20% 4 10% 18% 25% 23%	3602
	21st to end	Night	21% 3 9% 18% 32% 18%	4252
November	1st to 10th	Night	31% 4 7% 19% 23% 15%	2460
	11th to 20th	Night	29% 5% 10% 19% 20% 17%	2698
	21st to end	Night	37% 4 8% 18% 18% 15%	2730
December	1st to 10th	Night	54% 2 6% 13% 12% 13%	4380
	11th to 20th	Night	39% 5% 7% 15% 18% 17%	4947
	21st to end	Night	30% 4 6% 16% 25% 19%	6633

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% 7% 31% 28% 13% 1	330
	11th to 20th	Day	19% 8% 28% 32% 12% 2	330
	21st to end	Day	18% 7% 34% 29% 11% 1	363
February	1st to 10th	Day	22% 8% 23% 26% 18% 3	330
	11th to 20th	Day	21% 6% 37% 26% 8% 2	330
	21st to end	Day	19% 10% 37% 27% 7%	273
March	1st to 10th	Day	20% 12% 33% 28% 7%	330
	11th to 20th	Day	12% 8% 41% 28% 11% 1	330
	21st to end	Day	16% 7% 34% 34% 9% 1	363
April	1st to 10th	Day	17% 11% 34% 31% 8%	330
	11th to 20th	Day	13% 11% 35% 33% 8%	408
	21st to end	Day	13% 10% 35% 35% 6% 1	582
May	1st to 10th	Day	17% 6% 33% 35% 8% 1	753
	11th to 20th	Day	13% 6% 30% 38% 11% 2	775
	21st to end	Day	12% 4 25% 39% 19% 1	844
June	1st to 10th	Day	5% 1 11% 44% 32% 6%	731
	11th to 20th	Day	5% 12% 44% 31% 6%	730
	21st to end	Day	7% 2 9% 33% 38% 11%	730
July	1st to 10th	Day	10% 2 8% 30% 38% 12%	721
	11th to 20th	Day	5% 6% 31% 48% 11%	718
	21st to end	Day	5% 1 4 29% 47% 14%	792
August	1st to 10th	Day	3 2 34% 43% 18%	527
	11th to 20th	Day	3 4 30% 43% 19%	517
	21st to end	Day	5% 1 3 24% 38% 28%	523
September	1st to 10th	Day	10% 1 5% 21% 39% 23%	330
	11th to 20th	Day	6% 4 17% 46% 27%	330
	21st to end	Day	8% 1 5% 22% 43% 22%	330
October	1st to 10th	Day	7% 1 11% 25% 38% 16%	330
	11th to 20th	Day	11% 9% 36% 33% 11%	330
	21st to end	Day	13% 6% 18% 32% 25% 6%	363
November	1st to 10th	Day	16% 4 20% 30% 24% 6%	330
	11th to 20th	Day	16% 5% 20% 28% 26% 5%	330
	21st to end	Day	20% 9% 28% 26% 13% 3	330
December	1st to 10th	Day	22% 4 23% 29% 18% 4	330
	11th to 20th	Day	20% 9% 21% 28% 19% 2	330
	21st to end	Day	13% 5% 28% 32% 20% 2	363
January	1st to 10th	Night	19% 5% 24% 39% 12% 1	1050
	11th to 20th	Night	19% 6% 28% 40% 8%	1000
	21st to end	Night	20% 7% 27% 38% 7%	924
February	1st to 10th	Night	17% 8% 29% 38% 8%	840
	11th to 20th	Night	22% 7% 35% 30% 6%	824
	21st to end	Night	18% 9% 37% 33% 3	692
March	1st to 10th	Night	19% 11% 39% 28% 3	719
	11th to 20th	Night	13% 10% 40% 33% 4	630
	21st to end	Night	13% 10% 42% 32% 3	693
April	1st to 10th	Night	10% 8% 50% 30% 2	630
	11th to 20th	Night	15% 11% 46% 27% 2	623
	21st to end	Night	15% 11% 45% 23% 5%	630
May	1st to 10th	Night	12% 8% 48% 29% 3	630
	11th to 20th	Night	12% 7% 41% 34% 5%	621
	21st to end	Night	8% 5% 42% 37% 8%	683
June	1st to 10th	Night	3 1 30% 52% 14% 1	600
	11th to 20th	Night	4 1 33% 50% 11% 1	600
	21st to end	Night	4 2 21% 52% 21% 1	600
July	1st to 10th	Night	6% 1 14% 54% 23% 1	585
	11th to 20th	Night	3 1 14% 57% 25% 2	582
	21st to end	Night	4 2 11% 58% 26% 1	657
August	1st to 10th	Night	2 12% 56% 29% 1	597
	11th to 20th	Night	5% 1 11% 53% 29% 2	594
	21st to end	Night	5% 10% 46% 37% 3	660
September	1st to 10th	Night	8% 1 10% 46% 32% 3	600
	11th to 20th	Night	10% 1 7% 42% 38% 3	600
	21st to end	Night	8% 1 12% 45% 32% 4	600
October	1st to 10th	Night	4 1 14% 49% 31% 1	600
	11th to 20th	Night	11% 2 20% 45% 21% 1	620
	21st to end	Night	12% 4 25% 37% 21% 1	880
November	1st to 10th	Night	12% 4 20% 40% 22% 1	820
	11th to 20th	Night	13% 3 21% 43% 19% 1	1018
	21st to end	Night	18% 5% 23% 39% 14% 1	1050
December	1st to 10th	Night	22% 4 21% 38% 15% 1	1050
	11th to 20th	Night	20% 6% 23% 37% 13%	1050
	21st to end	Night	16% 6% 22% 43% 12%	1155

Page generated at 2026-05-29 00:53:32. Version ac07

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