Big Spring State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Big Spring State Park clear sky chart from 2005-11-06 to 2026-10-14.

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	6% 4 1 4 3 3 3 3 5% 7% 63%	157446
	Night	5% 3 1 3 3 3 3 3 5% 7% 64%	151789
Transparency	Day	22% 4 8% 22% 28% 17%	152543
	Night	21% 4 8% 22% 27% 19%	147702
Seeing	Day	7% 5% 24% 33% 24% 7%	17620
	Night	7% 6% 33% 40% 14% 1	27493

By Month

Percentage Cloud Cover SW (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	6% 4 1 4 3 3 3 3 4 6% 63%	5287
	11th to 20th	Day	3 2 1 3 2 2 2 2 3 6% 75%	5686
	21st to end	Day	9% 6% 2 5% 3 3 4 3 5% 7% 53%	6468
February	1st to 10th	Day	7% 5% 2 4 2 3 3 3 5% 6% 62%	2100
	11th to 20th	Day	7% 5% 2 5% 3 3 3 2 5% 7% 58%	2049
	21st to end	Day	7% 6% 2 3 2 3 2 2 3 5% 64%	1730
March	1st to 10th	Day	4 4 1 4 3 3 4 3 5% 6% 65%	4600
	11th to 20th	Day	11% 5% 1 4 3 3 3 3 5% 5% 58%	4944
	21st to end	Day	3 4 1 4 3 3 4 3 5% 6% 63%	5721
April	1st to 10th	Day	6% 3 1 4 2 2 3 3 5% 6% 63%	2520
	11th to 20th	Day	8% 4 2 4 3 3 3 3 4 6% 60%	2491
	21st to end	Day	6% 3 1 3 3 2 3 3 4 6% 66%	2520
May	1st to 10th	Day	10% 5% 2 5% 3 3 3 3 5% 7% 54%	7471
	11th to 20th	Day	8% 4 2 4 3 3 3 3 5% 6% 60%	7627
	21st to end	Day	8% 5% 2 5% 4 4 4 3 5% 7% 53%	8404
June	1st to 10th	Day	2 3 1 4 3 3 4 3 5% 8% 64%	2730
	11th to 20th	Day	3 3 1 3 3 4 4 3 5% 7% 65%	2730
	21st to end	Day	3 3 1 4 3 4 3 3 5% 8% 63%	2730
July	1st to 10th	Day	5% 4 2 5% 3 4 4 3 6% 9% 55%	7679
	11th to 20th	Day	5% 3 2 5% 4 4 4 4 6% 8% 55%	7680
	21st to end	Day	2 1 1 2 2 2 3 3 4 8% 71%	7992
August	1st to 10th	Day	1 1 2 2 2 2 2 4 7% 76%	6988
	11th to 20th	Day	2 2 1 3 3 3 4 4 6% 10% 63%	7003
	21st to end	Day	2 2 1 4 3 3 4 3 5% 8% 64%	7751
September	1st to 10th	Day	9% 4 2 5% 3 3 3 4 5% 9% 54%	2457
	11th to 20th	Day	9% 5% 2 5% 4 5% 4 3 5% 8% 50%	2310
	21st to end	Day	8% 4 2 4 3 4 3 3 4 5% 60%	2310
October	1st to 10th	Day	3 2 1 2 2 2 2 2 3 4 77%	3700
	11th to 20th	Day	10% 4 1 3 2 2 2 2 3 3 67%	3601
	21st to end	Day	6% 3 1 2 1 1 1 1 2 3 79%	3436
November	1st to 10th	Day	7% 4 1 4 2 2 2 2 4 5% 68%	1853
	11th to 20th	Day	4 4 1 4 2 3 3 2 4 5% 68%	1890
	21st to end	Day	10% 4 2 3 3 2 3 2 4 6% 60%	1890
December	1st to 10th	Day	11% 8% 2 6% 2 3 3 3 4 6% 53%	3030
	11th to 20th	Day	4 4 1 5% 3 4 3 3 4 5% 65%	3481
	21st to end	Day	7% 3 1 3 2 2 2 2 2 4 72%	4587
January	1st to 10th	Night	4 5% 2 5% 3 2 3 3 4 6% 63%	7634
	11th to 20th	Night	3 2 1 2 2 2 3 2 4 6% 73%	7348
	21st to end	Night	10% 5% 1 5% 4 4 4 3 5% 8% 52%	7746
February	1st to 10th	Night	7% 4 1 4 3 3 3 3 3 5% 63%	2520
	11th to 20th	Night	8% 4 2 5% 4 3 3 4 4 7% 56%	2458
	21st to end	Night	5% 4 2 4 3 3 4 2 5% 5% 63%	2076
March	1st to 10th	Night	4 4 1 4 2 2 2 2 5% 6% 67%	5494
	11th to 20th	Night	7% 4 1 4 2 3 3 3 5% 6% 62%	5241
	21st to end	Night	3 4 1 4 3 3 4 3 5% 8% 63%	5440
April	1st to 10th	Night	6% 4 2 4 3 2 3 3 5% 7% 61%	2100
	11th to 20th	Night	6% 4 1 4 3 3 3 3 5% 6% 62%	2077
	21st to end	Night	6% 4 1 3 3 2 3 3 4 5% 67%	2100
May	1st to 10th	Night	10% 5% 1 4 3 3 3 3 4 6% 57%	5472
	11th to 20th	Night	5% 2 1 3 3 3 4 3 5% 7% 65%	5265
	21st to end	Night	6% 4 2 4 3 3 5% 4 7% 9% 54%	5803
June	1st to 10th	Night	2 2 1 2 3 3 5% 3 7% 9% 63%	1890
	11th to 20th	Night	1 1 3 3 3 4 5% 7% 10% 62%	1890
	21st to end	Night	2 2 1 3 2 3 4 4 6% 8% 66%	1890
July	1st to 10th	Night	4 4 2 5% 4 4 4 4 7% 12% 50%	5310
	11th to 20th	Night	3 3 1 4 3 3 4 4 5% 9% 60%	5310
	21st to end	Night	2 2 1 2 2 2 3 2 4 7% 73%	6085
August	1st to 10th	Night	1 1 1 2 2 2 3 2 3 7% 76%	5834
	11th to 20th	Night	2 1 1 3 2 3 3 3 6% 12% 64%	5853
	21st to end	Night	1 2 1 3 2 2 3 3 6% 8% 68%	6465
September	1st to 10th	Night	7% 4 1 4 3 4 4 3 5% 7% 58%	2160
	11th to 20th	Night	7% 3 1 3 4 3 3 4 6% 8% 56%	2310
	21st to end	Night	8% 4 2 4 4 3 3 2 5% 8% 57%	2310
October	1st to 10th	Night	2 1 1 2 1 2 2 2 3 6% 77%	3700
	11th to 20th	Night	8% 3 1 3 2 2 2 2 2 4 71%	3603
	21st to end	Night	4 2 2 1 1 1 2 2 3 80%	4321
November	1st to 10th	Night	7% 3 1 3 2 2 2 3 3 5% 70%	2665
	11th to 20th	Night	4 2 1 3 3 2 3 3 5% 7% 66%	2730
	21st to end	Night	8% 5% 1 3 3 3 4 3 5% 6% 59%	2730
December	1st to 10th	Night	12% 5% 2 5% 3 3 3 2 4 5% 57%	4380
	11th to 20th	Night	4 4 1 4 3 3 3 3 4 6% 65%	4946
	21st to end	Night	5% 5% 2 5% 3 3 3 3 4 4 65%	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	23% 3 4 21% 35% 14%	5290
	11th to 20th	Day	13% 2 6% 24% 37% 18%	5686
	21st to end	Day	31% 3 5% 19% 26% 16%	6468
February	1st to 10th	Day	24% 3 5% 16% 27% 25%	2100
	11th to 20th	Day	27% 3 6% 21% 24% 19%	2059
	21st to end	Day	25% 2 3 13% 32% 25%	1730
March	1st to 10th	Day	21% 3 3 12% 26% 36%	4600
	11th to 20th	Day	29% 2 5% 10% 21% 33%	4944
	21st to end	Day	22% 4 5% 14% 28% 27%	5721
April	1st to 10th	Day	22% 3 6% 17% 24% 28%	2520
	11th to 20th	Day	26% 3 6% 14% 27% 23%	2494
	21st to end	Day	21% 3 7% 21% 26% 23%	2520
May	1st to 10th	Day	29% 4 7% 18% 22% 20%	7471
	11th to 20th	Day	25% 4 5% 13% 28% 25%	7631
	21st to end	Day	29% 5% 9% 26% 15% 17%	8405
June	1st to 10th	Day	18% 5% 13% 31% 23% 10%	2730
	11th to 20th	Day	19% 5% 8% 23% 30% 15%	2730
	21st to end	Day	20% 6% 11% 24% 26% 13%	2730
July	1st to 10th	Day	25% 6% 12% 28% 24% 5%	7616
	11th to 20th	Day	25% 7% 15% 31% 19% 3	7611
	21st to end	Day	11% 4 11% 33% 36% 5%	7815
August	1st to 10th	Day	10% 3 8% 31% 35% 12%	5532
	11th to 20th	Day	13% 4 12% 37% 30% 4	5519
	21st to end	Day	19% 6% 12% 24% 31% 8%	6078
September	1st to 10th	Day	28% 5% 8% 22% 26% 11%	2457
	11th to 20th	Day	33% 5% 10% 24% 22% 6%	2310
	21st to end	Day	27% 4 6% 20% 29% 15%	2310
October	1st to 10th	Day	13% 2 6% 14% 27% 38%	3700
	11th to 20th	Day	25% 3 5% 16% 23% 29%	3601
	21st to end	Day	14% 1 2 25% 40% 17%	3436
November	1st to 10th	Day	20% 2 5% 20% 30% 23%	1853
	11th to 20th	Day	20% 2 7% 19% 31% 20%	1890
	21st to end	Day	26% 3 5% 19% 29% 18%	1890
December	1st to 10th	Day	33% 3 5% 18% 27% 14%	3030
	11th to 20th	Day	23% 2 6% 18% 30% 21%	3479
	21st to end	Day	20% 2 3 19% 38% 19%	4587
January	1st to 10th	Night	23% 3 3 21% 36% 14%	7635
	11th to 20th	Night	15% 2 5% 20% 35% 23%	7348
	21st to end	Night	31% 3 4 19% 25% 17%	7746
February	1st to 10th	Night	25% 2 5% 15% 26% 26%	2520
	11th to 20th	Night	29% 4 6% 20% 21% 21%	2458
	21st to end	Night	24% 3 4 11% 27% 31%	2076
March	1st to 10th	Night	19% 2 3 11% 27% 37%	5494
	11th to 20th	Night	25% 2 7% 12% 16% 38%	5241
	21st to end	Night	20% 4 8% 15% 27% 26%	5440
April	1st to 10th	Night	23% 4 8% 18% 21% 26%	2100
	11th to 20th	Night	24% 3 8% 17% 25% 23%	2077
	21st to end	Night	21% 4 9% 21% 27% 19%	2100
May	1st to 10th	Night	27% 4 10% 23% 17% 19%	5470
	11th to 20th	Night	19% 4 8% 15% 31% 23%	5266
	21st to end	Night	25% 7% 15% 20% 14% 19%	5805
June	1st to 10th	Night	17% 5% 16% 32% 20% 9%	1890
	11th to 20th	Night	15% 6% 13% 25% 28% 13%	1890
	21st to end	Night	15% 5% 14% 28% 24% 14%	1890
July	1st to 10th	Night	25% 6% 13% 33% 20% 3	5265
	11th to 20th	Night	20% 6% 14% 34% 22% 4	5256
	21st to end	Night	12% 4 13% 31% 34% 6%	5950
August	1st to 10th	Night	10% 3 7% 29% 38% 13%	4614
	11th to 20th	Night	11% 3 11% 39% 32% 4	4613
	21st to end	Night	13% 5% 14% 26% 35% 7%	5069
September	1st to 10th	Night	25% 4 11% 23% 23% 14%	2160
	11th to 20th	Night	25% 5% 12% 26% 24% 7%	2310
	21st to end	Night	26% 4 7% 21% 24% 18%	2310
October	1st to 10th	Night	11% 3 7% 15% 25% 39%	3700
	11th to 20th	Night	19% 3 6% 17% 23% 32%	3603
	21st to end	Night	12% 2 3 25% 37% 21%	4321
November	1st to 10th	Night	18% 3 6% 22% 27% 24%	2665
	11th to 20th	Night	18% 4 6% 18% 31% 23%	2730
	21st to end	Night	26% 3 5% 15% 29% 21%	2730
December	1st to 10th	Night	30% 3 5% 18% 29% 15%	4380
	11th to 20th	Night	21% 3 4 18% 32% 21%	4947
	21st to end	Night	23% 3 4 21% 30% 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	9% 11% 37% 34% 9%	330
	11th to 20th	Day	9% 11% 37% 28% 14% 2	330
	21st to end	Day	10% 8% 36% 33% 12% 2	363
February	1st to 10th	Day	12% 5% 34% 35% 13% 1	330
	11th to 20th	Day	10% 9% 46% 26% 9% 1	330
	21st to end	Day	10% 11% 42% 31% 6%	273
March	1st to 10th	Day	12% 11% 37% 32% 8%	330
	11th to 20th	Day	13% 13% 32% 30% 10% 2	330
	21st to end	Day	3 13% 40% 35% 8% 1	422
April	1st to 10th	Day	7% 12% 44% 26% 9% 1	540
	11th to 20th	Day	11% 16% 45% 22% 6%	532
	21st to end	Day	6% 13% 40% 30% 9% 2	540
May	1st to 10th	Day	7% 10% 38% 33% 11% 1	686
	11th to 20th	Day	9% 7% 33% 33% 15% 3	775
	21st to end	Day	8% 3 32% 38% 17% 1	844
June	1st to 10th	Day	4 2 19% 48% 22% 4	780
	11th to 20th	Day	3 2 20% 47% 23% 4	780
	21st to end	Day	3 2 13% 39% 34% 8%	780
July	1st to 10th	Day	6% 1 8% 36% 37% 11%	771
	11th to 20th	Day	3 4 37% 45% 11%	768
	21st to end	Day	1 3 30% 46% 19%	733
August	1st to 10th	Day	3 2 28% 49% 18%	567
	11th to 20th	Day	4 2 4 27% 45% 18%	557
	21st to end	Day	3 1 5% 26% 45% 19%	627
September	1st to 10th	Day	9% 1 4 25% 44% 17%	507
	11th to 20th	Day	4 1 8% 27% 42% 19%	360
	21st to end	Day	10% 2 11% 26% 31% 19%	360
October	1st to 10th	Day	4 1 13% 35% 33% 15%	360
	11th to 20th	Day	8% 5% 22% 35% 27% 4	339
	21st to end	Day	13% 7% 20% 34% 20% 5%	363
November	1st to 10th	Day	12% 6% 27% 32% 19% 4	330
	11th to 20th	Day	9% 7% 27% 31% 20% 5%	330
	21st to end	Day	11% 11% 33% 27% 14% 4	330
December	1st to 10th	Day	12% 6% 34% 32% 15% 2	330
	11th to 20th	Day	7% 9% 31% 36% 15% 1	330
	21st to end	Day	10% 7% 38% 33% 10% 1	363
January	1st to 10th	Night	9% 7% 40% 36% 9%	1050
	11th to 20th	Night	10% 9% 35% 37% 9% 1	939
	21st to end	Night	9% 8% 40% 35% 8%	924
February	1st to 10th	Night	10% 6% 43% 33% 8%	840
	11th to 20th	Night	10% 12% 44% 29% 4	824
	21st to end	Night	9% 11% 51% 26% 3	692
March	1st to 10th	Night	9% 11% 45% 32% 3	840
	11th to 20th	Night	10% 13% 42% 30% 5%	703
	21st to end	Night	5% 14% 51% 28% 3	693
April	1st to 10th	Night	8% 11% 52% 27% 3	630
	11th to 20th	Night	5% 12% 57% 23% 2	623
	21st to end	Night	7% 11% 52% 27% 3	630
May	1st to 10th	Night	6% 9% 50% 32% 3	630
	11th to 20th	Night	5% 7% 43% 34% 10%	621
	21st to end	Night	5% 5% 42% 39% 8%	683
June	1st to 10th	Night	2 2 34% 50% 11%	630
	11th to 20th	Night	2 1 38% 52% 7%	630
	21st to end	Night	3 1 25% 53% 18% 1	630
July	1st to 10th	Night	5% 2 12% 53% 27% 1	615
	11th to 20th	Night	3 7% 58% 31% 1	612
	21st to end	Night	2 6% 58% 31% 2	690
August	1st to 10th	Night	1 7% 54% 37% 1	627
	11th to 20th	Night	4 7% 50% 36% 3	624
	21st to end	Night	2 1 7% 43% 44% 2	693
September	1st to 10th	Night	8% 1 5% 50% 35% 2	630
	11th to 20th	Night	8% 1 12% 49% 30% 1	630
	21st to end	Night	9% 2 15% 51% 21% 1	630
October	1st to 10th	Night	4 2 28% 45% 20% 1	630
	11th to 20th	Night	8% 5% 28% 45% 14%	609
	21st to end	Night	7% 7% 30% 38% 17% 2	911
November	1st to 10th	Night	8% 5% 30% 41% 15% 1	1025
	11th to 20th	Night	4 7% 32% 43% 13% 1	1050
	21st to end	Night	10% 7% 37% 33% 13% 1	1050
December	1st to 10th	Night	12% 6% 35% 37% 10%	1050
	11th to 20th	Night	10% 9% 35% 38% 8%	1050
	21st to end	Night	9% 7% 37% 38% 8% 1	1155

Page generated at 2026-10-11 04:06:33. Version ac07

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