College Station
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the College Station clear sky chart from 2005-11-06 to 2026-08-30.

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 6% 4 4 4 4 6% 8% 44%	143697
	Night	13% 6% 2 5% 3 3 4 3 5% 7% 48%	138881
Transparency	Day	36% 6% 12% 21% 17% 7%	147388
	Night	34% 5% 11% 20% 19% 10%	143257
Seeing	Day	13% 7% 20% 26% 25% 10%	17388
	Night	14% 7% 25% 35% 18% 2	27154

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% 9% 3 5% 3 3 3 3 4 6% 46%	5289
	11th to 20th	Day	12% 5% 2 5% 3 3 3 3 5% 6% 52%	5310
	21st to end	Day	27% 9% 3 7% 5% 3 2 2 3 5% 34%	5812
February	1st to 10th	Day	21% 9% 3 7% 4 3 3 3 4 5% 40%	2053
	11th to 20th	Day	21% 9% 2 5% 5% 4 3 2 4 6% 39%	2049
	21st to end	Day	19% 7% 2 5% 3 3 3 3 3 5% 45%	1832
March	1st to 10th	Day	15% 9% 3 7% 5% 4 4 3 5% 6% 40%	5046
	11th to 20th	Day	13% 6% 2 5% 4 4 4 3 4 6% 48%	5090
	21st to end	Day	16% 9% 2 7% 4 4 4 3 5% 6% 40%	5583
April	1st to 10th	Day	13% 10% 2 7% 5% 4 6% 3 5% 6% 38%	2310
	11th to 20th	Day	15% 8% 2 7% 5% 4 4 4 6% 6% 39%	2389
	21st to end	Day	13% 6% 3 7% 4 3 4 4 5% 7% 42%	2520
May	1st to 10th	Day	20% 8% 3 7% 4 4 4 4 5% 7% 34%	7611
	11th to 20th	Day	10% 6% 2 7% 5% 5% 5% 4 7% 7% 40%	7627
	21st to end	Day	11% 7% 3 8% 6% 6% 6% 5% 8% 9% 32%	8392
June	1st to 10th	Day	6% 5% 2 5% 5% 5% 6% 5% 9% 10% 42%	2730
	11th to 20th	Day	5% 4 2 5% 5% 6% 5% 5% 7% 10% 46%	2730
	21st to end	Day	5% 5% 2 6% 6% 6% 7% 5% 9% 11% 39%	2730
July	1st to 10th	Day	7% 4 2 5% 4 4 5% 4 7% 12% 46%	7680
	11th to 20th	Day	7% 5% 2 7% 5% 5% 5% 5% 8% 12% 38%	7680
	21st to end	Day	7% 4 2 5% 4 4 4 4 6% 10% 50%	8337
August	1st to 10th	Day	2 2 2 2 3 3 3 5% 8% 69%	4364
	11th to 20th	Day	3 1 1 3 3 4 4 4 7% 12% 57%	4278
	21st to end	Day	5% 4 2 5% 4 6% 6% 5% 8% 10% 45%	4158
September	1st to 10th	Day	5% 5% 2 7% 5% 6% 6% 5% 7% 8% 45%	2200
	11th to 20th	Day	10% 5% 2 7% 5% 6% 4 4 6% 7% 43%	2200
	21st to end	Day	6% 3 2 4 5% 5% 5% 5% 6% 7% 52%	2200
October	1st to 10th	Day	5% 3 2 5% 3 3 4 2 5% 7% 61%	2135
	11th to 20th	Day	12% 5% 2 4 3 3 3 4 4 5% 56%	2000
	21st to end	Day	13% 5% 2 4 3 3 3 3 4 4 58%	2200
November	1st to 10th	Day	11% 6% 2 5% 3 4 4 3 6% 7% 48%	2058
	11th to 20th	Day	10% 6% 2 6% 4 3 4 2 4 6% 53%	2100
	21st to end	Day	18% 7% 3 6% 5% 3 3 3 5% 5% 43%	1906
December	1st to 10th	Day	22% 7% 2 5% 3 4 3 2 4 5% 42%	3030
	11th to 20th	Day	20% 7% 2 6% 4 3 3 3 4 7% 40%	3481
	21st to end	Day	14% 8% 3 7% 3 4 4 2 3 5% 47%	4587
January	1st to 10th	Night	17% 7% 2 5% 3 3 3 2 4 5% 51%	7634
	11th to 20th	Night	12% 4 1 4 2 3 4 3 4 5% 58%	7680
	21st to end	Night	28% 7% 2 6% 4 3 3 3 4 5% 34%	8402
February	1st to 10th	Night	19% 7% 2 6% 3 4 3 2 4 5% 46%	2583
	11th to 20th	Night	21% 8% 2 5% 3 3 3 2 3 5% 45%	2458
	21st to end	Night	21% 6% 2 4 4 2 4 2 4 6% 45%	1972
March	1st to 10th	Night	18% 9% 3 6% 4 4 3 3 4 7% 40%	5029
	11th to 20th	Night	16% 6% 2 6% 4 3 4 2 5% 5% 48%	5090
	21st to end	Night	18% 10% 2 6% 3 3 3 2 4 5% 44%	5588
April	1st to 10th	Night	13% 6% 2 6% 4 4 5% 3 5% 7% 45%	2310
	11th to 20th	Night	13% 6% 2 6% 4 4 4 3 6% 8% 44%	2178
	21st to end	Night	15% 7% 2 5% 4 4 3 3 5% 7% 44%	2100
May	1st to 10th	Night	21% 9% 3 7% 4 4 4 3 5% 7% 32%	5267
	11th to 20th	Night	11% 7% 3 8% 5% 5% 5% 4 6% 7% 41%	5265
	21st to end	Night	12% 7% 2 7% 5% 5% 5% 5% 7% 10% 35%	5793
June	1st to 10th	Night	6% 3 2 4 3 3 3 3 8% 11% 53%	1890
	11th to 20th	Night	4 3 1 4 3 3 4 4 6% 10% 59%	1890
	21st to end	Night	4 3 2 4 5% 4 5% 4 8% 11% 50%	1890
July	1st to 10th	Night	5% 4 2 5% 4 5% 4 4 7% 12% 49%	5308
	11th to 20th	Night	5% 5% 2 6% 4 4 4 4 7% 12% 49%	5307
	21st to end	Night	6% 4 2 4 3 3 4 4 6% 9% 54%	5770
August	1st to 10th	Night	1 1 1 2 2 2 2 5% 10% 74%	3016
	11th to 20th	Night	2 2 1 3 2 3 3 4 7% 12% 60%	2996
	21st to end	Night	3 3 1 5% 3 4 4 4 8% 12% 51%	3932
September	1st to 10th	Night	5% 5% 2 5% 4 5% 4 4 5% 9% 51%	2200
	11th to 20th	Night	8% 5% 2 6% 5% 5% 5% 4 5% 7% 47%	2200
	21st to end	Night	6% 3 2 4 3 3 4 3 5% 8% 58%	2200
October	1st to 10th	Night	3 3 1 4 3 3 3 3 4 7% 64%	2245
	11th to 20th	Night	11% 4 1 4 2 3 2 2 4 5% 62%	2400
	21st to end	Night	12% 5% 1 4 3 2 2 3 3 4 61%	2640
November	1st to 10th	Night	11% 5% 2 5% 3 2 3 3 4 6% 56%	2460
	11th to 20th	Night	9% 6% 2 4 3 3 4 3 5% 6% 54%	2520
	21st to end	Night	16% 6% 2 4 4 3 3 3 4 6% 47%	2709
December	1st to 10th	Night	21% 9% 3 6% 3 3 3 2 4 5% 40%	4380
	11th to 20th	Night	18% 9% 3 6% 3 3 3 2 4 4 45%	4946
	21st to end	Night	16% 6% 2 5% 3 3 3 2 3 5% 54%	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	40% 4 7% 24% 18% 7%	5290
	11th to 20th	Day	34% 3 5% 19% 27% 12%	5310
	21st to end	Day	54% 3 4 12% 17% 11%	5812
February	1st to 10th	Day	47% 5% 6% 12% 19% 12%	2053
	11th to 20th	Day	47% 3 8% 16% 17% 9%	2059
	21st to end	Day	42% 5% 7% 16% 18% 12%	1832
March	1st to 10th	Day	42% 7% 7% 14% 19% 11%	5046
	11th to 20th	Day	36% 6% 7% 10% 19% 22%	5090
	21st to end	Day	43% 5% 9% 19% 17% 6%	5585
April	1st to 10th	Day	45% 7% 7% 16% 14% 11%	2310
	11th to 20th	Day	44% 6% 9% 14% 17% 9%	2389
	21st to end	Day	40% 6% 10% 18% 20% 6%	2520
May	1st to 10th	Day	48% 7% 10% 21% 11% 3	7649
	11th to 20th	Day	39% 6% 13% 18% 20% 3	7631
	21st to end	Day	43% 9% 14% 23% 10% 1	8405
June	1st to 10th	Day	32% 10% 15% 26% 15% 2	2730
	11th to 20th	Day	30% 9% 17% 24% 17% 4	2730
	21st to end	Day	36% 10% 15% 24% 13% 1	2730
July	1st to 10th	Day	31% 5% 29% 31% 4	7616
	11th to 20th	Day	37% 7% 24% 22% 10%	7611
	21st to end	Day	29% 7% 15% 35% 14% 1	8155
August	1st to 10th	Day	14% 5% 14% 40% 25% 2	4350
	11th to 20th	Day	18% 7% 30% 34% 9% 2	4317
	21st to end	Day	31% 10% 20% 24% 13% 1	4157
September	1st to 10th	Day	34% 9% 12% 21% 16% 8%	2200
	11th to 20th	Day	38% 9% 13% 18% 17% 5%	2200
	21st to end	Day	29% 8% 11% 21% 17% 14%	2200
October	1st to 10th	Day	15% 4 7% 13% 22% 40%	3473
	11th to 20th	Day	20% 4 6% 17% 34% 19%	3240
	21st to end	Day	25% 5% 5% 20% 31% 15%	3538
November	1st to 10th	Day	34% 7% 9% 17% 23% 11%	2058
	11th to 20th	Day	33% 5% 9% 17% 22% 13%	2100
	21st to end	Day	43% 5% 8% 15% 19% 10%	1906
December	1st to 10th	Day	45% 4 7% 16% 21% 7%	3030
	11th to 20th	Day	43% 5% 8% 12% 23% 10%	3479
	21st to end	Day	40% 4 6% 13% 28% 9%	4587
January	1st to 10th	Night	37% 4 8% 21% 20% 10%	7635
	11th to 20th	Night	29% 3 5% 18% 29% 16%	7680
	21st to end	Night	53% 3 4 12% 17% 12%	8402
February	1st to 10th	Night	42% 4 6% 12% 20% 15%	2583
	11th to 20th	Night	43% 4 6% 16% 18% 12%	2458
	21st to end	Night	43% 4 7% 14% 17% 15%	1972
March	1st to 10th	Night	43% 6% 8% 13% 21% 10%	5029
	11th to 20th	Night	38% 5% 7% 14% 14% 21%	5090
	21st to end	Night	44% 5% 7% 16% 19% 9%	5588
April	1st to 10th	Night	38% 7% 10% 18% 16% 12%	2310
	11th to 20th	Night	38% 6% 11% 16% 16% 13%	2178
	21st to end	Night	39% 6% 11% 18% 20% 6%	2100
May	1st to 10th	Night	50% 7% 11% 19% 11% 3	5294
	11th to 20th	Night	41% 6% 12% 18% 19% 4	5266
	21st to end	Night	41% 8% 18% 23% 9% 1	5805
June	1st to 10th	Night	23% 8% 20% 28% 20% 2	1890
	11th to 20th	Night	20% 8% 19% 31% 18% 5%	1890
	21st to end	Night	26% 8% 19% 29% 16% 2	1890
July	1st to 10th	Night	28% 7% 31% 31% 3	5265
	11th to 20th	Night	30% 6% 25% 28% 10%	5256
	21st to end	Night	26% 7% 17% 34% 15% 1	5641
August	1st to 10th	Night	8% 5% 17% 41% 27% 2	3006
	11th to 20th	Night	17% 7% 30% 35% 11% 1	3023
	21st to end	Night	24% 11% 22% 29% 13% 1	3932
September	1st to 10th	Night	27% 10% 18% 22% 15% 8%	2200
	11th to 20th	Night	34% 8% 15% 21% 16% 7%	2200
	21st to end	Night	24% 6% 15% 22% 19% 14%	2200
October	1st to 10th	Night	13% 4 7% 16% 19% 41%	3674
	11th to 20th	Night	16% 3 4 21% 32% 24%	3899
	21st to end	Night	21% 3 5% 21% 32% 18%	4252
November	1st to 10th	Night	30% 5% 9% 20% 23% 13%	2460
	11th to 20th	Night	32% 5% 9% 19% 20% 15%	2520
	21st to end	Night	39% 4 9% 16% 19% 13%	2709
December	1st to 10th	Night	47% 3 5% 16% 21% 7%	4380
	11th to 20th	Night	44% 4 8% 8% 23% 14%	4947
	21st to end	Night	35% 4 5% 15% 29% 11%	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	22% 14% 31% 24% 8% 2	330
	11th to 20th	Day	23% 13% 30% 24% 8% 2	330
	21st to end	Day	23% 14% 35% 19% 8%	363
February	1st to 10th	Day	24% 15% 32% 21% 8% 1	330
	11th to 20th	Day	28% 17% 30% 18% 6%	330
	21st to end	Day	26% 17% 37% 14% 6%	273
March	1st to 10th	Day	22% 16% 35% 19% 7%	330
	11th to 20th	Day	16% 18% 39% 19% 6% 1	330
	21st to end	Day	18% 12% 37% 21% 10% 1	363
April	1st to 10th	Day	20% 15% 36% 23% 5%	330
	11th to 20th	Day	22% 14% 31% 22% 10% 1	427
	21st to end	Day	20% 11% 33% 25% 10% 1	540
May	1st to 10th	Day	16% 10% 35% 29% 9% 1	747
	11th to 20th	Day	13% 9% 29% 31% 15% 4	775
	21st to end	Day	11% 5% 25% 35% 20% 4	844
June	1st to 10th	Day	7% 3 14% 36% 30% 10%	780
	11th to 20th	Day	8% 2 12% 40% 31% 7%	780
	21st to end	Day	7% 1 12% 29% 36% 15%	780
July	1st to 10th	Day	6% 3 8% 27% 40% 16%	771
	11th to 20th	Day	5% 1 3 29% 43% 19%	768
	21st to end	Day	5% 2 5% 23% 46% 19%	849
August	1st to 10th	Day	3 1 3 18% 51% 24%	776
	11th to 20th	Day	5% 1 2 19% 50% 22%	755
	21st to end	Day	7% 2 3 16% 39% 32%	461
September	1st to 10th	Day	5% 1 5% 25% 36% 28%	330
	11th to 20th	Day	8% 6% 21% 38% 27%	330
	21st to end	Day	7% 2 7% 27% 38% 20%	330
October	1st to 10th	Day	3 1 12% 32% 37% 15%	330
	11th to 20th	Day	11% 4 21% 29% 24% 12%	330
	21st to end	Day	22% 9% 20% 21% 20% 7%	363
November	1st to 10th	Day	13% 7% 21% 32% 20% 7%	330
	11th to 20th	Day	15% 9% 23% 33% 17% 3	330
	21st to end	Day	20% 13% 30% 22% 12% 3	330
December	1st to 10th	Day	22% 8% 31% 24% 12% 5%	330
	11th to 20th	Day	25% 12% 29% 23% 8% 3	330
	21st to end	Day	21% 11% 33% 22% 12% 1	363
January	1st to 10th	Night	20% 10% 31% 33% 7%	1050
	11th to 20th	Night	21% 11% 31% 29% 8%	1050
	21st to end	Night	22% 10% 31% 31% 6%	1155
February	1st to 10th	Night	22% 12% 34% 28% 4	903
	11th to 20th	Night	26% 11% 32% 28% 3	824
	21st to end	Night	25% 13% 38% 21% 3	588
March	1st to 10th	Night	22% 10% 40% 24% 4	630
	11th to 20th	Night	17% 12% 38% 26% 7%	630
	21st to end	Night	15% 9% 42% 28% 5%	693
April	1st to 10th	Night	16% 10% 40% 30% 4	630
	11th to 20th	Night	16% 11% 35% 32% 6%	623
	21st to end	Night	17% 11% 37% 27% 8%	630
May	1st to 10th	Night	13% 11% 40% 29% 6% 1	630
	11th to 20th	Night	14% 5% 32% 35% 13% 1	621
	21st to end	Night	8% 4 28% 43% 16% 2	683
June	1st to 10th	Night	7% 2 16% 47% 25% 3	630
	11th to 20th	Night	4 1 21% 50% 22% 2	630
	21st to end	Night	4 1 12% 45% 32% 5%	630
July	1st to 10th	Night	4 2 6% 45% 38% 5%	615
	11th to 20th	Night	4 1 7% 46% 38% 4	612
	21st to end	Night	3 2 6% 49% 37% 3	690
August	1st to 10th	Night	1 4 50% 41% 3	627
	11th to 20th	Night	5% 3 46% 41% 5%	624
	21st to end	Night	4 7% 35% 48% 7%	687
September	1st to 10th	Night	6% 1 9% 36% 42% 7%	600
	11th to 20th	Night	11% 1 6% 34% 43% 5%	600
	21st to end	Night	7% 2 11% 37% 38% 5%	600
October	1st to 10th	Night	4 2 12% 44% 31% 6%	645
	11th to 20th	Night	12% 3 21% 40% 22% 2	800
	21st to end	Night	14% 8% 26% 31% 19% 2	880
November	1st to 10th	Night	13% 4 24% 37% 20% 1	820
	11th to 20th	Night	11% 7% 26% 40% 15% 1	840
	21st to end	Night	19% 8% 28% 29% 14% 1	1029
December	1st to 10th	Night	22% 7% 29% 31% 11%	1050
	11th to 20th	Night	23% 11% 27% 32% 7%	1050
	21st to end	Night	21% 8% 29% 32% 9% 1	1155

Page generated at 2026-08-27 03:07:13. Version ac07

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