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 2024-11-02.

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% 6% 62%	100863
	Night	5% 4 1 3 3 3 3 3 5% 7% 63%	98318
Transparency	Day	24% 4 8% 21% 27% 17%	100633
	Night	21% 4 8% 22% 27% 18%	98138
Seeing	Day	7% 5% 23% 33% 25% 7%	14995
	Night	7% 6% 32% 39% 14% 1	24938

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	8% 5% 1 4 2 3 3 2 4 6% 63%	2847
	11th to 20th	Day	5% 4 1 4 1 1 2 1 3 6% 72%	3044
	21st to end	Day	6% 7% 2 5% 3 3 4 3 4 7% 58%	3487
February	1st to 10th	Day	7% 5% 2 4 2 3 3 3 5% 6% 61%	1900
	11th to 20th	Day	7% 5% 2 5% 3 3 3 2 5% 7% 58%	1849
	21st to end	Day	8% 7% 2 3 2 3 3 2 3 4 62%	1570
March	1st to 10th	Day	5% 6% 2 5% 3 3 4 3 5% 6% 58%	3130
	11th to 20th	Day	16% 6% 2 6% 3 4 3 2 4 5% 49%	3377
	21st to end	Day	4 5% 2 4 4 4 5% 4 6% 6% 58%	3905
April	1st to 10th	Day	6% 3 1 4 2 3 3 3 5% 6% 64%	2280
	11th to 20th	Day	8% 4 2 4 2 3 3 3 4 6% 61%	2251
	21st to end	Day	5% 3 1 3 3 2 3 3 4 5% 68%	2280
May	1st to 10th	Day	8% 4 2 4 3 3 3 3 4 5% 62%	4020
	11th to 20th	Day	11% 4 2 4 3 3 3 3 5% 5% 58%	4082
	21st to end	Day	7% 3 1 4 3 3 4 3 5% 6% 61%	4489
June	1st to 10th	Day	2 3 1 3 3 3 4 3 4 8% 65%	2470
	11th to 20th	Day	3 2 1 3 3 4 4 3 5% 7% 66%	2470
	21st to end	Day	4 3 1 3 3 3 3 3 5% 7% 63%	2470
July	1st to 10th	Day	4 4 1 4 4 4 4 4 5% 8% 57%	4120
	11th to 20th	Day	2 2 1 3 3 3 4 3 5% 8% 67%	4120
	21st to end	Day	3 3 1 4 3 3 4 4 5% 9% 61%	4287
August	1st to 10th	Day	1 1 1 2 2 2 3 3 5% 8% 72%	3784
	11th to 20th	Day	3 2 1 3 3 3 4 4 5% 8% 65%	3726
	21st to end	Day	3 3 2 6% 4 4 5% 4 6% 9% 55%	4180
September	1st to 10th	Day	9% 4 2 5% 4 4 3 4 5% 9% 51%	2223
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 3 5% 7% 48%	2090
	21st to end	Day	9% 4 1 4 3 3 3 2 4 5% 62%	2090
October	1st to 10th	Day	5% 3 1 4 3 3 3 3 5% 6% 64%	2090
	11th to 20th	Day	8% 4 1 3 3 2 2 2 3 4 68%	2090
	21st to end	Day	9% 4 1 3 2 2 2 2 3 3 70%	2034
November	1st to 10th	Day	7% 4 1 4 2 2 3 2 4 6% 66%	1682
	11th to 20th	Day	4 4 1 4 2 3 3 2 4 5% 67%	1710
	21st to end	Day	10% 4 2 3 3 3 3 2 4 6% 60%	1710
December	1st to 10th	Day	10% 6% 1 4 2 2 3 3 5% 6% 58%	1710
	11th to 20th	Day	6% 4 1 5% 3 4 4 3 5% 5% 58%	2161
	21st to end	Day	9% 4 2 4 2 2 2 2 3 4 66%	3135
January	1st to 10th	Night	4 4 1 4 3 3 3 3 4 6% 64%	4108
	11th to 20th	Night	5% 4 1 2 2 2 2 2 4 6% 70%	3956
	21st to end	Night	7% 5% 1 5% 3 3 4 3 4 6% 58%	4180
February	1st to 10th	Night	8% 5% 1 4 3 3 3 3 4 6% 61%	2280
	11th to 20th	Night	8% 4 2 4 4 3 3 4 4 6% 57%	2218
	21st to end	Night	6% 5% 2 5% 3 3 4 2 5% 5% 61%	1884
March	1st to 10th	Night	6% 6% 2 4 2 2 2 2 4 6% 62%	3734
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 5% 6% 53%	3586
	21st to end	Night	4 5% 2 4 4 4 4 3 5% 7% 59%	3711
April	1st to 10th	Night	5% 4 2 3 3 2 3 3 6% 7% 62%	1900
	11th to 20th	Night	6% 4 1 4 3 3 3 3 5% 6% 62%	1877
	21st to end	Night	5% 4 1 2 3 1 3 3 4 5% 70%	1900
May	1st to 10th	Night	7% 4 1 3 3 2 3 3 4 6% 63%	2946
	11th to 20th	Night	7% 2 1 3 3 3 4 3 4 6% 64%	2823
	21st to end	Night	4 2 1 3 2 2 4 4 6% 8% 64%	3098
June	1st to 10th	Night	2 2 1 2 3 3 4 3 7% 9% 64%	1710
	11th to 20th	Night	1 1 3 3 3 4 4 7% 10% 63%	1710
	21st to end	Night	2 2 1 3 2 3 4 3 6% 7% 68%	1710
July	1st to 10th	Night	3 3 1 3 3 3 4 4 6% 11% 59%	2850
	11th to 20th	Night	1 2 1 2 3 3 3 4 6% 10% 65%	2850
	21st to end	Night	3 3 1 3 3 2 3 3 5% 8% 66%	3272
August	1st to 10th	Night	2 2 1 2 3 2 3 2 3 8% 73%	3155
	11th to 20th	Night	3 1 1 3 2 3 3 4 6% 10% 64%	3113
	21st to end	Night	1 2 1 3 3 3 3 3 6% 9% 64%	3487
September	1st to 10th	Night	7% 4 1 4 3 4 4 3 5% 7% 58%	1954
	11th to 20th	Night	8% 4 1 3 4 4 4 4 6% 8% 55%	2090
	21st to end	Night	8% 4 2 3 3 3 3 2 5% 7% 60%	2090
October	1st to 10th	Night	4 2 1 3 2 3 3 4 5% 9% 63%	2090
	11th to 20th	Night	8% 3 1 3 2 1 2 2 2 5% 71%	2090
	21st to end	Night	7% 3 1 3 2 2 2 2 3 4 71%	2537
November	1st to 10th	Night	7% 3 1 3 2 2 2 3 3 6% 69%	2431
	11th to 20th	Night	4 2 1 4 3 3 4 3 5% 7% 65%	2470
	21st to end	Night	9% 4 1 3 3 3 4 3 4 5% 59%	2470
December	1st to 10th	Night	10% 4 1 3 2 3 3 2 4 7% 60%	2470
	11th to 20th	Night	6% 4 1 5% 4 3 3 3 5% 6% 59%	3036
	21st to end	Night	6% 5% 2 5% 3 3 3 3 4 4 62%	4532

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	24% 3 3 17% 35% 17%	2848
	11th to 20th	Day	17% 2 9% 18% 39% 16%	3044
	21st to end	Day	28% 3 7% 22% 30% 11%	3487
February	1st to 10th	Day	25% 3 5% 17% 27% 23%	1900
	11th to 20th	Day	27% 3 5% 21% 24% 20%	1859
	21st to end	Day	28% 2 3 12% 30% 25%	1570
March	1st to 10th	Day	26% 3 3 11% 25% 31%	3130
	11th to 20th	Day	40% 2 7% 13% 24% 14%	3377
	21st to end	Day	26% 4 6% 15% 26% 23%	3905
April	1st to 10th	Day	21% 3 6% 16% 25% 29%	2280
	11th to 20th	Day	25% 3 7% 13% 27% 25%	2254
	21st to end	Day	20% 3 7% 21% 26% 23%	2280
May	1st to 10th	Day	26% 2 6% 14% 18% 33%	4020
	11th to 20th	Day	29% 4 7% 17% 23% 20%	4086
	21st to end	Day	23% 4 8% 21% 17% 26%	4489
June	1st to 10th	Day	18% 4 12% 32% 22% 11%	2470
	11th to 20th	Day	18% 5% 8% 24% 29% 15%	2470
	21st to end	Day	20% 6% 10% 24% 26% 15%	2470
July	1st to 10th	Day	24% 6% 12% 32% 19% 7%	4056
	11th to 20th	Day	16% 4 12% 35% 27% 6%	4051
	21st to end	Day	18% 4 11% 31% 29% 6%	4151
August	1st to 10th	Day	11% 4 10% 31% 37% 7%	3772
	11th to 20th	Day	17% 5% 13% 29% 31% 6%	3762
	21st to end	Day	24% 7% 14% 24% 26% 5%	4179
September	1st to 10th	Day	30% 5% 9% 20% 25% 11%	2223
	11th to 20th	Day	35% 5% 9% 21% 23% 7%	2090
	21st to end	Day	26% 4 6% 19% 30% 16%	2090
October	1st to 10th	Day	22% 4 9% 22% 23% 19%	2090
	11th to 20th	Day	23% 3 5% 16% 28% 25%	2090
	21st to end	Day	22% 1 3 19% 35% 20%	2034
November	1st to 10th	Day	21% 2 6% 22% 29% 20%	1682
	11th to 20th	Day	21% 2 8% 20% 31% 18%	1710
	21st to end	Day	27% 3 5% 19% 28% 19%	1710
December	1st to 10th	Day	28% 2 6% 20% 30% 13%	1710
	11th to 20th	Day	28% 2 8% 19% 24% 19%	2159
	21st to end	Day	25% 2 2 19% 32% 20%	3135
January	1st to 10th	Night	21% 3 4 18% 36% 18%	4108
	11th to 20th	Night	17% 2 7% 22% 31% 21%	3956
	21st to end	Night	28% 3 5% 23% 26% 15%	4180
February	1st to 10th	Night	26% 2 6% 15% 25% 25%	2280
	11th to 20th	Night	29% 3 5% 18% 22% 23%	2218
	21st to end	Night	25% 3 5% 11% 26% 31%	1884
March	1st to 10th	Night	24% 3 3 11% 25% 33%	3734
	11th to 20th	Night	33% 3 9% 17% 20% 19%	3586
	21st to end	Night	24% 4 7% 18% 28% 19%	3711
April	1st to 10th	Night	21% 4 8% 19% 22% 26%	1900
	11th to 20th	Night	24% 3 7% 18% 24% 24%	1877
	21st to end	Night	19% 3 9% 22% 28% 20%	1900
May	1st to 10th	Night	23% 4 9% 19% 17% 29%	2946
	11th to 20th	Night	21% 4 11% 21% 19% 24%	2824
	21st to end	Night	17% 5% 11% 21% 19% 28%	3099
June	1st to 10th	Night	16% 5% 16% 32% 20% 10%	1710
	11th to 20th	Night	15% 6% 12% 25% 28% 13%	1710
	21st to end	Night	14% 5% 13% 28% 25% 15%	1710
July	1st to 10th	Night	19% 6% 14% 38% 18% 4	2805
	11th to 20th	Night	13% 4 10% 38% 29% 7%	2796
	21st to end	Night	17% 4 11% 27% 34% 7%	3169
August	1st to 10th	Night	13% 4 7% 26% 40% 10%	3144
	11th to 20th	Night	15% 4 12% 31% 32% 5%	3143
	21st to end	Night	17% 6% 17% 28% 26% 6%	3487
September	1st to 10th	Night	26% 4 12% 22% 22% 14%	1954
	11th to 20th	Night	27% 6% 11% 24% 25% 8%	2090
	21st to end	Night	25% 3 7% 22% 24% 19%	2090
October	1st to 10th	Night	18% 5% 12% 24% 21% 20%	2090
	11th to 20th	Night	20% 2 6% 18% 26% 28%	2090
	21st to end	Night	19% 2 4 18% 33% 24%	2537
November	1st to 10th	Night	19% 3 6% 23% 27% 22%	2431
	11th to 20th	Night	19% 4 6% 19% 31% 22%	2470
	21st to end	Night	27% 3 5% 14% 29% 22%	2470
December	1st to 10th	Night	25% 3 6% 19% 28% 19%	2470
	11th to 20th	Night	27% 3 5% 20% 27% 19%	3037
	21st to end	Night	25% 3 3 17% 31% 20%	4532

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	10% 10% 34% 37% 8%	270
	11th to 20th	Day	9% 10% 34% 31% 13% 2	270
	21st to end	Day	8% 8% 35% 33% 13% 2	297
February	1st to 10th	Day	13% 6% 36% 35% 11%	270
	11th to 20th	Day	11% 7% 44% 28% 9% 1	270
	21st to end	Day	12% 12% 44% 28% 4	225
March	1st to 10th	Day	12% 9% 38% 33% 8%	270
	11th to 20th	Day	13% 13% 30% 30% 11% 2	270
	21st to end	Day	4 15% 42% 31% 6% 1	350
April	1st to 10th	Day	7% 11% 46% 26% 9% 1	460
	11th to 20th	Day	11% 15% 44% 22% 7%	452
	21st to end	Day	6% 13% 38% 31% 10% 2	460
May	1st to 10th	Day	6% 10% 38% 33% 11% 2	592
	11th to 20th	Day	9% 6% 32% 34% 16% 3	675
	21st to end	Day	8% 3 33% 38% 16% 1	734
June	1st to 10th	Day	4 2 17% 48% 25% 5%	680
	11th to 20th	Day	3 1 21% 48% 24% 4	680
	21st to end	Day	4 1 12% 38% 36% 9%	680
July	1st to 10th	Day	5% 1 7% 35% 39% 12%	671
	11th to 20th	Day	2 4 37% 46% 12%	668
	21st to end	Day	2 3 29% 47% 19%	635
August	1st to 10th	Day	2 2 26% 49% 19%	487
	11th to 20th	Day	4 2 4 27% 44% 19%	477
	21st to end	Day	4 1 5% 27% 44% 19%	539
September	1st to 10th	Day	10% 4 24% 43% 18%	433
	11th to 20th	Day	5% 1 7% 23% 42% 22%	300
	21st to end	Day	11% 2 10% 24% 30% 22%	300
October	1st to 10th	Day	4 1 13% 36% 33% 13%	300
	11th to 20th	Day	9% 5% 23% 32% 27% 4	300
	21st to end	Day	13% 6% 20% 35% 19% 5%	330
November	1st to 10th	Day	14% 4 25% 32% 19% 5%	273
	11th to 20th	Day	9% 7% 29% 32% 19% 5%	270
	21st to end	Day	11% 12% 32% 27% 13% 4	270
December	1st to 10th	Day	14% 5% 28% 34% 17% 2	270
	11th to 20th	Day	7% 10% 34% 36% 13%	270
	21st to end	Day	11% 8% 38% 33% 9%	297
January	1st to 10th	Night	9% 6% 40% 36% 10%	950
	11th to 20th	Night	11% 8% 34% 37% 9% 1	851
	21st to end	Night	9% 8% 39% 36% 8%	836
February	1st to 10th	Night	11% 6% 43% 33% 8%	760
	11th to 20th	Night	10% 10% 45% 30% 5%	744
	21st to end	Night	10% 11% 52% 24% 3	628
March	1st to 10th	Night	10% 11% 44% 32% 3	760
	11th to 20th	Night	11% 13% 40% 31% 5%	637
	21st to end	Night	5% 15% 51% 26% 3	627
April	1st to 10th	Night	7% 11% 54% 26% 3	570
	11th to 20th	Night	5% 11% 57% 24% 2	563
	21st to end	Night	6% 10% 54% 27% 4	570
May	1st to 10th	Night	5% 9% 51% 32% 3	570
	11th to 20th	Night	5% 7% 41% 36% 11%	561
	21st to end	Night	4 5% 43% 39% 8%	617
June	1st to 10th	Night	2 2 33% 51% 12%	570
	11th to 20th	Night	2 1 37% 53% 7%	570
	21st to end	Night	3 1 23% 54% 19% 1	570
July	1st to 10th	Night	4 1 10% 54% 29% 2	555
	11th to 20th	Night	3 1 8% 57% 32% 1	552
	21st to end	Night	2 6% 56% 33% 2	624
August	1st to 10th	Night	1 7% 52% 39% 1	567
	11th to 20th	Night	5% 6% 48% 38% 3	564
	21st to end	Night	2 1 7% 42% 45% 3	627
September	1st to 10th	Night	8% 1 4 49% 35% 2	570
	11th to 20th	Night	8% 1 11% 47% 32% 1	570
	21st to end	Night	9% 1 14% 51% 23% 1	570
October	1st to 10th	Night	5% 2 29% 43% 20% 1	570
	11th to 20th	Night	8% 5% 28% 44% 14%	570
	21st to end	Night	7% 7% 30% 37% 17% 2	865
November	1st to 10th	Night	9% 4 29% 41% 16% 1	935
	11th to 20th	Night	4 6% 33% 43% 13% 1	950
	21st to end	Night	10% 7% 36% 33% 13% 1	950
December	1st to 10th	Night	12% 5% 34% 37% 11%	950
	11th to 20th	Night	11% 9% 35% 37% 7%	950
	21st to end	Night	9% 7% 37% 38% 8% 1	1045

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