Lake Bob Sandlin State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Bob Sandlin State Park clear sky chart from 2005-11-06 to 2026-05-17.

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% 6% 2 5% 4 4 4 3 5% 7% 48%	132270
	Night	11% 6% 2 5% 3 3 3 3 5% 7% 52%	130826
Transparency	Day	36% 4 10% 24% 20% 7%	135895
	Night	32% 3 9% 22% 23% 10%	135251
Seeing	Day	13% 6% 20% 26% 24% 10%	17167
	Night	14% 6% 24% 34% 20% 2	27084

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% 8% 3 5% 3 3 3 3 4 6% 49%	5289
	11th to 20th	Day	9% 4 1 3 2 3 3 3 5% 7% 59%	5310
	21st to end	Day	24% 9% 2 6% 3 3 3 2 3 4 41%	5812
February	1st to 10th	Day	19% 9% 2 7% 4 4 3 2 4 4 42%	1890
	11th to 20th	Day	19% 9% 3 6% 4 3 3 3 4 5% 42%	2012
	21st to end	Day	19% 8% 3 5% 2 2 3 2 3 4 49%	1883
March	1st to 10th	Day	16% 10% 3 6% 4 3 3 3 4 5% 44%	5046
	11th to 20th	Day	13% 5% 2 4 3 3 4 3 5% 5% 53%	5090
	21st to end	Day	14% 8% 3 6% 4 3 3 3 5% 6% 44%	5583
April	1st to 10th	Day	13% 7% 3 7% 5% 4 4 3 5% 6% 44%	2331
	11th to 20th	Day	15% 7% 2 5% 3 4 5% 3 6% 7% 43%	2494
	21st to end	Day	13% 6% 2 6% 5% 4 5% 4 7% 6% 42%	2520
May	1st to 10th	Day	17% 8% 3 7% 5% 4 4 3 5% 6% 38%	5898
	11th to 20th	Day	14% 8% 3 7% 4 4 4 4 5% 6% 42%	5941
	21st to end	Day	13% 7% 3 7% 5% 5% 5% 4 6% 9% 37%	6434
June	1st to 10th	Day	6% 5% 1 6% 5% 4 5% 5% 7% 10% 46%	2600
	11th to 20th	Day	5% 4 2 5% 4 5% 6% 5% 7% 10% 47%	2600
	21st to end	Day	4 3 1 4 4 4 6% 5% 7% 10% 51%	2600
July	1st to 10th	Day	8% 6% 2 7% 6% 6% 6% 5% 8% 10% 37%	5900
	11th to 20th	Day	3 3 1 4 3 3 4 3 6% 11% 60%	5900
	21st to end	Day	6% 6% 2 7% 5% 4 5% 4 7% 9% 45%	6422
August	1st to 10th	Day	2 1 1 2 3 3 4 3 6% 8% 68%	4234
	11th to 20th	Day	4 3 1 3 4 4 4 5% 7% 10% 55%	4089
	21st to end	Day	4 4 2 6% 5% 6% 6% 5% 8% 12% 43%	4312
September	1st to 10th	Day	9% 5% 2 6% 4 4 5% 3 5% 6% 50%	2280
	11th to 20th	Day	10% 5% 2 7% 4 5% 4 3 6% 8% 46%	2200
	21st to end	Day	7% 4 1 4 3 3 4 3 5% 7% 58%	2200
October	1st to 10th	Day	6% 3 1 3 3 3 3 3 5% 7% 61%	2038
	11th to 20th	Day	13% 4 1 4 3 3 3 3 4 6% 58%	2000
	21st to end	Day	14% 5% 2 5% 3 2 3 2 3 4 57%	2200
November	1st to 10th	Day	12% 6% 2 5% 3 3 3 3 4 6% 53%	2058
	11th to 20th	Day	9% 4 2 5% 4 3 3 3 4 6% 56%	2100
	21st to end	Day	17% 7% 2 4 4 3 3 2 3 5% 51%	1906
December	1st to 10th	Day	18% 6% 2 5% 3 3 2 2 4 6% 50%	3030
	11th to 20th	Day	15% 10% 3 7% 4 4 4 3 5% 5% 42%	3481
	21st to end	Day	17% 10% 4 5% 3 3 3 3 3 5% 45%	4587
January	1st to 10th	Night	14% 6% 2 5% 3 3 3 3 4 5% 51%	7634
	11th to 20th	Night	8% 3 1 3 2 2 2 2 4 5% 67%	7680
	21st to end	Night	26% 8% 2 6% 3 3 3 2 3 4 40%	8402
February	1st to 10th	Night	15% 7% 3 5% 4 3 3 2 4 5% 49%	2730
	11th to 20th	Night	18% 7% 3 6% 4 3 3 2 3 4 46%	2513
	21st to end	Night	17% 6% 2 4 4 2 2 3 3 4 52%	1921
March	1st to 10th	Night	19% 8% 3 5% 4 3 3 2 4 6% 43%	5029
	11th to 20th	Night	11% 5% 2 5% 4 4 4 3 5% 7% 52%	5090
	21st to end	Night	12% 6% 2 5% 4 4 4 3 5% 6% 48%	5588
April	1st to 10th	Night	11% 6% 2 5% 4 4 3 4 6% 7% 49%	2287
	11th to 20th	Night	11% 6% 2 5% 4 3 3 5% 5% 7% 49%	2075
	21st to end	Night	11% 6% 1 5% 4 3 4 3 5% 7% 51%	2100
May	1st to 10th	Night	15% 8% 3 7% 4 4 4 3 6% 7% 38%	4217
	11th to 20th	Night	11% 7% 3 7% 5% 4 4 3 6% 8% 43%	4107
	21st to end	Night	11% 6% 2 6% 3 4 4 3 6% 9% 45%	4443
June	1st to 10th	Night	4 5% 2 4 3 3 4 4 6% 10% 56%	1800
	11th to 20th	Night	4 4 2 4 3 2 4 3 5% 8% 62%	1800
	21st to end	Night	4 3 1 2 4 4 4 4 7% 10% 58%	1800
July	1st to 10th	Night	5% 4 2 7% 5% 4 5% 4 8% 12% 44%	4078
	11th to 20th	Night	3 3 1 3 2 2 2 3 5% 12% 64%	4077
	21st to end	Night	4 4 2 5% 4 4 5% 4 7% 9% 53%	4449
August	1st to 10th	Night	2 1 1 1 1 2 2 2 5% 8% 74%	2926
	11th to 20th	Night	3 2 1 3 3 3 3 3 6% 10% 62%	2952
	21st to end	Night	3 2 1 4 4 4 5% 5% 7% 9% 55%	3586
September	1st to 10th	Night	7% 5% 1 4 4 4 4 3 5% 8% 56%	2114
	11th to 20th	Night	10% 5% 2 5% 3 3 3 3 5% 8% 54%	2200
	21st to end	Night	6% 3 1 4 3 3 4 3 4 7% 62%	2200
October	1st to 10th	Night	5% 3 1 4 3 3 3 3 4 6% 66%	2340
	11th to 20th	Night	11% 4 1 3 3 2 2 2 4 6% 63%	2400
	21st to end	Night	14% 4 2 4 3 2 2 2 3 4 60%	2640
November	1st to 10th	Night	11% 4 2 4 3 3 3 2 4 6% 58%	2460
	11th to 20th	Night	8% 5% 2 5% 4 3 3 3 4 6% 58%	2520
	21st to end	Night	15% 6% 2 5% 3 3 3 3 3 6% 51%	2709
December	1st to 10th	Night	16% 7% 2 4 3 3 3 2 4 5% 51%	4380
	11th to 20th	Night	15% 7% 3 7% 4 4 3 2 4 4 48%	4946
	21st to end	Night	14% 10% 3 6% 3 3 3 2 3 4 49%	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	38% 2 8% 27% 22% 3	5290
	11th to 20th	Day	27% 2 5% 27% 32% 6%	5310
	21st to end	Day	49% 1 3 15% 22% 9%	5812
February	1st to 10th	Day	47% 3 4 18% 20% 8%	1890
	11th to 20th	Day	47% 3 6% 20% 18% 7%	2022
	21st to end	Day	42% 2 5% 16% 26% 10%	1883
March	1st to 10th	Day	43% 3 5% 14% 21% 14%	5046
	11th to 20th	Day	34% 2 5% 19% 19% 20%	5090
	21st to end	Day	43% 3 8% 22% 20% 4	5585
April	1st to 10th	Day	41% 3 8% 22% 18% 8%	2331
	11th to 20th	Day	41% 4 10% 18% 20% 7%	2494
	21st to end	Day	42% 5% 8% 21% 19% 4	2520
May	1st to 10th	Day	47% 4 10% 25% 11% 2	5935
	11th to 20th	Day	44% 4 9% 21% 20% 2	5945
	21st to end	Day	44% 5% 12% 21% 15% 3	6447
June	1st to 10th	Day	32% 6% 16% 28% 16% 2	2600
	11th to 20th	Day	32% 5% 15% 26% 19% 3	2600
	21st to end	Day	26% 7% 13% 31% 20% 3	2600
July	1st to 10th	Day	38% 8% 22% 24% 8%	5836
	11th to 20th	Day	19% 5% 17% 40% 19% 1	5831
	21st to end	Day	34% 5% 14% 34% 12% 1	6240
August	1st to 10th	Day	16% 4 13% 34% 29% 5%	4220
	11th to 20th	Day	24% 5% 18% 40% 12% 1	4128
	21st to end	Day	31% 8% 17% 28% 13% 2	4311
September	1st to 10th	Day	34% 5% 10% 22% 20% 10%	2280
	11th to 20th	Day	36% 5% 11% 21% 20% 7%	2200
	21st to end	Day	26% 4 9% 23% 27% 11%	2200
October	1st to 10th	Day	15% 2 7% 12% 28% 36%	3311
	11th to 20th	Day	20% 2 3 19% 33% 23%	3240
	21st to end	Day	27% 3 4 26% 33% 8%	3538
November	1st to 10th	Day	34% 3 8% 21% 26% 9%	2058
	11th to 20th	Day	31% 2 8% 21% 28% 11%	2100
	21st to end	Day	39% 2 5% 19% 26% 8%	1906
December	1st to 10th	Day	39% 2 5% 27% 23% 5%	3030
	11th to 20th	Day	45% 2 4 16% 25% 7%	3479
	21st to end	Day	45% 3 4 20% 24% 5%	4587
January	1st to 10th	Night	37% 2 7% 22% 27% 4	7635
	11th to 20th	Night	23% 1 5% 20% 36% 15%	7680
	21st to end	Night	50% 2 4 15% 19% 10%	8402
February	1st to 10th	Night	39% 3 6% 20% 20% 11%	2730
	11th to 20th	Night	45% 2 5% 18% 22% 8%	2513
	21st to end	Night	38% 2 7% 16% 23% 14%	1921
March	1st to 10th	Night	45% 2 5% 12% 20% 16%	5029
	11th to 20th	Night	34% 2 6% 16% 19% 23%	5090
	21st to end	Night	38% 3 9% 20% 23% 6%	5588
April	1st to 10th	Night	34% 3 11% 21% 19% 12%	2287
	11th to 20th	Night	35% 4 9% 20% 22% 10%	2075
	21st to end	Night	34% 4 10% 23% 24% 5%	2100
May	1st to 10th	Night	46% 5% 10% 23% 12% 4	4244
	11th to 20th	Night	41% 4 13% 18% 22% 2	4108
	21st to end	Night	36% 4 15% 24% 13% 8%	4452
June	1st to 10th	Night	24% 6% 16% 29% 22% 3	1800
	11th to 20th	Night	21% 5% 14% 33% 22% 5%	1800
	21st to end	Night	20% 6% 14% 31% 26% 3	1800
July	1st to 10th	Night	32% 6% 20% 32% 10%	4035
	11th to 20th	Night	15% 4 18% 40% 20% 3	4026
	21st to end	Night	27% 7% 16% 33% 15% 3	4320
August	1st to 10th	Night	11% 3 13% 31% 36% 6%	2916
	11th to 20th	Night	18% 3 16% 42% 18% 4	2979
	21st to end	Night	23% 7% 16% 29% 23% 2	3586
September	1st to 10th	Night	27% 5% 11% 23% 24% 9%	2114
	11th to 20th	Night	31% 4 9% 26% 20% 10%	2200
	21st to end	Night	22% 3 9% 22% 30% 15%	2200
October	1st to 10th	Night	13% 2 5% 15% 22% 43%	3821
	11th to 20th	Night	16% 2 4 16% 35% 27%	3899
	21st to end	Night	25% 2 4 22% 29% 16%	4252
November	1st to 10th	Night	30% 2 8% 18% 28% 13%	2460
	11th to 20th	Night	29% 3 6% 21% 26% 15%	2520
	21st to end	Night	37% 2 6% 18% 26% 10%	2709
December	1st to 10th	Night	38% 2 6% 21% 26% 6%	4380
	11th to 20th	Night	43% 2 6% 15% 24% 11%	4947
	21st to end	Night	40% 3 5% 19% 26% 7%	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	23% 11% 37% 20% 8% 1	330
	11th to 20th	Day	18% 16% 38% 20% 7%	330
	21st to end	Day	21% 16% 37% 19% 6%	363
February	1st to 10th	Day	24% 9% 44% 17% 5% 1	330
	11th to 20th	Day	29% 13% 38% 15% 4	330
	21st to end	Day	27% 18% 38% 13% 5%	273
March	1st to 10th	Day	22% 14% 35% 21% 8%	330
	11th to 20th	Day	23% 15% 40% 17% 4 1	330
	21st to end	Day	17% 15% 36% 25% 7% 1	363
April	1st to 10th	Day	21% 14% 34% 22% 8% 1	351
	11th to 20th	Day	23% 11% 31% 23% 10% 1	532
	21st to end	Day	21% 9% 29% 26% 12% 3	540
May	1st to 10th	Day	15% 8% 32% 33% 12% 1	710
	11th to 20th	Day	14% 5% 25% 33% 18% 4	756
	21st to end	Day	14% 3 19% 38% 20% 6%	789
June	1st to 10th	Day	8% 4 12% 29% 35% 12%	730
	11th to 20th	Day	6% 2 12% 38% 32% 10%	730
	21st to end	Day	4 2 9% 29% 40% 16%	730
July	1st to 10th	Day	7% 2 7% 28% 39% 17%	721
	11th to 20th	Day	3 2 4 27% 44% 20%	718
	21st to end	Day	6% 2 3 26% 42% 22%	794
August	1st to 10th	Day	4 1 4 22% 47% 22%	726
	11th to 20th	Day	10% 1 2 25% 44% 18%	672
	21st to end	Day	10% 2 4 19% 38% 27%	583
September	1st to 10th	Day	9% 1 7% 21% 38% 24%	410
	11th to 20th	Day	4 2 8% 22% 32% 32%	330
	21st to end	Day	10% 3 9% 28% 30% 20%	330
October	1st to 10th	Day	3 2 12% 40% 30% 13%	330
	11th to 20th	Day	11% 5% 27% 29% 20% 8%	330
	21st to end	Day	22% 7% 22% 29% 15% 5%	363
November	1st to 10th	Day	16% 5% 29% 28% 18% 3	330
	11th to 20th	Day	13% 8% 29% 36% 12% 2	330
	21st to end	Day	20% 12% 31% 24% 12% 1	330
December	1st to 10th	Day	21% 13% 31% 24% 10% 2	330
	11th to 20th	Day	19% 10% 38% 22% 9% 2	330
	21st to end	Day	21% 13% 37% 22% 5% 1	363
January	1st to 10th	Night	19% 11% 30% 32% 7%	1050
	11th to 20th	Night	19% 13% 34% 27% 7% 1	1050
	21st to end	Night	21% 9% 36% 29% 5%	1155
February	1st to 10th	Night	20% 9% 36% 28% 6%	1050
	11th to 20th	Night	26% 11% 34% 26% 3	878
	21st to end	Night	22% 14% 38% 23% 4	537
March	1st to 10th	Night	21% 10% 33% 29% 7%	630
	11th to 20th	Night	18% 8% 34% 34% 6%	630
	21st to end	Night	15% 8% 34% 36% 7%	693
April	1st to 10th	Night	14% 7% 40% 30% 8%	630
	11th to 20th	Night	14% 10% 36% 28% 11%	623
	21st to end	Night	14% 7% 34% 32% 11% 1	630
May	1st to 10th	Night	12% 5% 33% 40% 10% 1	630
	11th to 20th	Night	12% 6% 24% 38% 19% 2	609
	21st to end	Night	9% 3 20% 43% 21% 3	650
June	1st to 10th	Night	5% 2 11% 38% 41% 3	600
	11th to 20th	Night	6% 1 12% 44% 35% 3	600
	21st to end	Night	5% 1 8% 33% 45% 8%	600
July	1st to 10th	Night	4 2 2 38% 50% 4	585
	11th to 20th	Night	3 3 35% 51% 7%	582
	21st to end	Night	3 1 4 34% 49% 9%	657
August	1st to 10th	Night	3 1 3 33% 53% 7%	597
	11th to 20th	Night	8% 1 3 30% 51% 8%	594
	21st to end	Night	5% 1 3 31% 50% 8%	660
September	1st to 10th	Night	11% 2 6% 33% 41% 8%	600
	11th to 20th	Night	12% 2 6% 31% 46% 5%	600
	21st to end	Night	8% 2 11% 37% 38% 4	600
October	1st to 10th	Night	6% 1 11% 45% 34% 4	740
	11th to 20th	Night	12% 4 22% 39% 21% 2	800
	21st to end	Night	18% 5% 24% 34% 17% 2	880
November	1st to 10th	Night	13% 4 23% 43% 16% 2	820
	11th to 20th	Night	11% 7% 29% 41% 11% 1	840
	21st to end	Night	18% 10% 28% 31% 13%	1029
December	1st to 10th	Night	17% 10% 30% 37% 6%	1050
	11th to 20th	Night	20% 9% 28% 35% 7%	1050
	21st to end	Night	19% 10% 30% 33% 7%	1155

Page generated at 2026-05-14 00:58:57. Version ac07

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