Huntsville State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Huntsville State Park clear sky chart from 2005-11-06 to 2025-05-11.

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	13% 6% 2 6% 4 4 4 4 6% 7% 42%	114366
	Night	14% 7% 2 5% 3 3 3 3 5% 7% 47%	114774
Transparency	Day	39% 6% 10% 19% 18% 8%	118069
	Night	36% 5% 10% 19% 20% 10%	119200
Seeing	Day	14% 9% 22% 27% 22% 7%	15521
	Night	15% 9% 26% 32% 16% 2	25500

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	18% 9% 3 5% 3 3 3 2 4 6% 44%	4077
	11th to 20th	Day	15% 7% 2 5% 3 3 3 3 4 5% 50%	4080
	21st to end	Day	29% 9% 3 5% 3 2 2 2 4 5% 37%	4488
February	1st to 10th	Day	21% 8% 3 7% 3 3 4 3 4 6% 38%	1880
	11th to 20th	Day	22% 8% 2 7% 5% 3 3 3 3 5% 40%	1949
	21st to end	Day	19% 8% 2 6% 4 3 4 3 4 6% 40%	1810
March	1st to 10th	Day	16% 10% 3 8% 5% 4 4 3 4 6% 37%	4936
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 5% 6% 47%	4980
	21st to end	Day	17% 8% 2 6% 4 4 4 3 5% 6% 40%	5462
April	1st to 10th	Day	16% 8% 3 7% 5% 5% 3 3 4 6% 39%	2200
	11th to 20th	Day	16% 6% 3 7% 5% 5% 4 4 6% 6% 39%	2332
	21st to end	Day	12% 6% 3 6% 5% 5% 5% 4 5% 8% 42%	2400
May	1st to 10th	Day	19% 9% 3 8% 5% 5% 5% 4 6% 6% 29%	4045
	11th to 20th	Day	14% 6% 2 6% 4 4 4 4 6% 7% 43%	4083
	21st to end	Day	9% 6% 2 7% 6% 6% 6% 5% 8% 11% 33%	4477
June	1st to 10th	Day	6% 5% 2 6% 6% 7% 6% 6% 8% 9% 40%	2470
	11th to 20th	Day	6% 4 1 6% 6% 6% 6% 5% 7% 9% 44%	2470
	21st to end	Day	6% 6% 2 7% 7% 7% 7% 6% 8% 9% 34%	2470
July	1st to 10th	Day	9% 5% 1 5% 5% 5% 6% 6% 8% 11% 38%	4120
	11th to 20th	Day	7% 6% 3 7% 7% 6% 6% 5% 8% 10% 35%	4120
	21st to end	Day	14% 8% 3 7% 6% 5% 5% 5% 7% 10% 29%	4465
August	1st to 10th	Day	2 1 1 2 3 3 4 4 6% 9% 65%	4104
	11th to 20th	Day	3 2 1 4 3 5% 6% 5% 7% 13% 51%	3923
	21st to end	Day	6% 5% 2 7% 5% 6% 6% 5% 8% 9% 41%	4116
September	1st to 10th	Day	7% 5% 2 7% 5% 7% 6% 5% 7% 8% 41%	2090
	11th to 20th	Day	13% 7% 2 7% 6% 5% 5% 4 7% 6% 39%	2090
	21st to end	Day	7% 4 1 7% 5% 5% 4 3 5% 7% 52%	2090
October	1st to 10th	Day	7% 4 2 4 3 3 4 3 4 6% 59%	1977
	11th to 20th	Day	11% 5% 1 5% 3 3 4 3 4 5% 55%	1900
	21st to end	Day	14% 6% 2 4 2 2 3 2 4 4 56%	2090
November	1st to 10th	Day	11% 6% 2 4 4 5% 4 4 5% 7% 46%	1958
	11th to 20th	Day	11% 6% 2 6% 3 3 4 3 5% 7% 50%	2000
	21st to end	Day	16% 8% 2 6% 4 4 3 3 5% 5% 45%	1895
December	1st to 10th	Day	22% 6% 2 5% 3 3 3 3 4 5% 43%	2940
	11th to 20th	Day	16% 9% 3 6% 4 4 4 2 5% 6% 42%	3391
	21st to end	Day	17% 8% 2 6% 4 3 3 3 4 5% 46%	4488
January	1st to 10th	Night	18% 6% 2 5% 2 3 3 3 4 6% 49%	5888
	11th to 20th	Night	15% 7% 2 5% 2 2 3 2 3 5% 55%	5900
	21st to end	Night	29% 10% 2 4 3 3 3 2 3 5% 37%	6490
February	1st to 10th	Night	19% 9% 3 6% 4 3 3 2 4 5% 41%	2535
	11th to 20th	Night	22% 9% 2 5% 2 3 3 2 4 5% 42%	2338
	21st to end	Night	21% 9% 2 6% 3 3 3 3 4 5% 41%	1818
March	1st to 10th	Night	20% 11% 2 5% 4 3 3 3 4 6% 39%	4919
	11th to 20th	Night	15% 7% 2 6% 4 3 3 3 4 6% 46%	4980
	21st to end	Night	19% 10% 3 6% 4 4 3 3 3 4 41%	5467
April	1st to 10th	Night	14% 7% 2 6% 4 4 5% 3 5% 6% 43%	2200
	11th to 20th	Night	12% 7% 2 6% 4 4 4 3 5% 8% 45%	2015
	21st to end	Night	15% 6% 2 5% 3 4 3 3 5% 7% 45%	2000
May	1st to 10th	Night	19% 10% 3 7% 5% 4 4 3 6% 8% 33%	3057
	11th to 20th	Night	14% 7% 3 7% 4 4 3 3 5% 6% 44%	2828
	21st to end	Night	10% 7% 2 6% 4 4 5% 5% 8% 10% 39%	3090
June	1st to 10th	Night	5% 4 1 4 3 4 5% 4 7% 11% 54%	1710
	11th to 20th	Night	3 2 1 3 3 3 4 5% 7% 11% 57%	1710
	21st to end	Night	5% 5% 1 4 5% 5% 5% 5% 9% 11% 46%	1710
July	1st to 10th	Night	6% 4 2 5% 4 4 5% 4 8% 14% 43%	2850
	11th to 20th	Night	3 5% 2 5% 5% 5% 5% 4 7% 11% 48%	2850
	21st to end	Night	13% 8% 3 7% 5% 4 4 4 7% 10% 36%	3098
August	1st to 10th	Night	1 1 1 2 2 2 3 2 4 9% 73%	2836
	11th to 20th	Night	3 2 1 3 2 3 3 4 7% 13% 60%	2912
	21st to end	Night	5% 4 2 5% 5% 4 5% 5% 8% 10% 48%	3534
September	1st to 10th	Night	6% 5% 2 6% 4 4 5% 4 7% 8% 50%	2090
	11th to 20th	Night	9% 7% 2 7% 5% 4 4 5% 7% 8% 43%	2090
	21st to end	Night	9% 4 1 4 3 3 4 3 6% 7% 57%	2090
October	1st to 10th	Night	5% 3 1 4 3 3 3 4 5% 7% 62%	2182
	11th to 20th	Night	9% 5% 2 4 2 3 2 2 4 6% 61%	2280
	21st to end	Night	13% 5% 2 4 3 2 3 2 3 5% 60%	2508
November	1st to 10th	Night	12% 6% 2 4 3 4 4 2 5% 7% 53%	2340
	11th to 20th	Night	10% 6% 3 5% 4 4 4 3 4 6% 52%	2400
	21st to end	Night	15% 6% 3 6% 3 3 4 3 4 6% 45%	2503
December	1st to 10th	Night	20% 9% 3 7% 4 4 3 3 4 5% 39%	4250
	11th to 20th	Night	18% 11% 3 6% 3 3 3 2 4 5% 44%	4816
	21st to end	Night	15% 7% 2 5% 3 3 2 2 4 4 52%	6490

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	44% 3 4 22% 20% 6%	4078
	11th to 20th	Day	38% 2 4 17% 28% 11%	4080
	21st to end	Day	52% 2 3 13% 16% 14%	4488
February	1st to 10th	Day	49% 3 5% 13% 18% 12%	1880
	11th to 20th	Day	50% 3 6% 14% 16% 10%	1959
	21st to end	Day	47% 4 8% 15% 16% 11%	1810
March	1st to 10th	Day	48% 4 7% 11% 19% 10%	4936
	11th to 20th	Day	37% 5% 7% 11% 20% 19%	4980
	21st to end	Day	44% 4 9% 20% 17% 5%	5464
April	1st to 10th	Day	48% 5% 5% 16% 16% 9%	2200
	11th to 20th	Day	45% 5% 8% 15% 18% 9%	2332
	21st to end	Day	41% 5% 8% 20% 21% 5%	2400
May	1st to 10th	Day	52% 7% 11% 16% 10% 4	4080
	11th to 20th	Day	39% 7% 10% 17% 24% 2	4087
	21st to end	Day	41% 10% 12% 26% 11% 1	4489
June	1st to 10th	Day	36% 9% 15% 24% 16% 1	2470
	11th to 20th	Day	33% 8% 14% 25% 16% 3	2470
	21st to end	Day	43% 9% 14% 22% 11% 1	2470
July	1st to 10th	Day	37% 10% 26% 23% 4	4056
	11th to 20th	Day	41% 9% 17% 21% 12% 1	4051
	21st to end	Day	49% 9% 15% 21% 6% 1	4325
August	1st to 10th	Day	16% 5% 15% 36% 27% 1	4090
	11th to 20th	Day	23% 7% 30% 30% 8% 1	3962
	21st to end	Day	37% 11% 16% 21% 13% 2	4115
September	1st to 10th	Day	38% 8% 13% 19% 15% 7%	2090
	11th to 20th	Day	44% 6% 12% 16% 17% 5%	2090
	21st to end	Day	32% 6% 11% 21% 18% 12%	2090
October	1st to 10th	Day	17% 3 6% 13% 22% 39%	3289
	11th to 20th	Day	21% 3 6% 17% 34% 20%	3140
	21st to end	Day	25% 3 4 15% 38% 14%	3428
November	1st to 10th	Day	36% 6% 9% 17% 22% 10%	1958
	11th to 20th	Day	34% 4 9% 16% 23% 14%	2000
	21st to end	Day	42% 4 6% 18% 19% 10%	1895
December	1st to 10th	Day	44% 3 7% 16% 24% 5%	2940
	11th to 20th	Day	43% 4 7% 13% 22% 11%	3389
	21st to end	Day	41% 3 5% 14% 28% 9%	4488
January	1st to 10th	Night	38% 3 6% 23% 22% 8%	5888
	11th to 20th	Night	35% 2 4 19% 30% 11%	5900
	21st to end	Night	53% 2 4 12% 17% 13%	6490
February	1st to 10th	Night	47% 3 5% 13% 17% 15%	2535
	11th to 20th	Night	46% 3 6% 15% 18% 12%	2338
	21st to end	Night	46% 4 6% 13% 16% 14%	1818
March	1st to 10th	Night	47% 4 7% 12% 20% 10%	4919
	11th to 20th	Night	39% 5% 7% 15% 15% 20%	4980
	21st to end	Night	48% 4 7% 14% 19% 9%	5467
April	1st to 10th	Night	41% 5% 9% 16% 17% 12%	2200
	11th to 20th	Night	39% 5% 9% 18% 17% 12%	2015
	21st to end	Night	39% 5% 10% 19% 22% 6%	2000
May	1st to 10th	Night	50% 7% 9% 20% 11% 4	3087
	11th to 20th	Night	40% 5% 9% 19% 22% 4	2829
	21st to end	Night	37% 9% 15% 27% 10% 1	3099
June	1st to 10th	Night	24% 8% 19% 31% 18% 1	1710
	11th to 20th	Night	20% 8% 19% 30% 18% 5%	1710
	21st to end	Night	27% 10% 19% 28% 14% 1	1710
July	1st to 10th	Night	30% 9% 32% 25% 4	2805
	11th to 20th	Night	29% 8% 24% 28% 11%	2796
	21st to end	Night	42% 9% 20% 22% 6%	2999
August	1st to 10th	Night	9% 4 17% 41% 27% 1	2826
	11th to 20th	Night	16% 6% 32% 35% 9% 1	2939
	21st to end	Night	29% 11% 21% 26% 11% 2	3534
September	1st to 10th	Night	30% 8% 21% 21% 13% 7%	2090
	11th to 20th	Night	38% 8% 16% 17% 16% 6%	2090
	21st to end	Night	27% 6% 13% 21% 21% 12%	2090
October	1st to 10th	Night	15% 3 7% 16% 18% 41%	3637
	11th to 20th	Night	16% 2 4 24% 30% 24%	3779
	21st to end	Night	23% 3 5% 15% 38% 16%	4120
November	1st to 10th	Night	32% 5% 11% 19% 21% 11%	2340
	11th to 20th	Night	35% 3 9% 17% 22% 14%	2400
	21st to end	Night	40% 4 8% 16% 20% 12%	2503
December	1st to 10th	Night	49% 3 5% 16% 21% 6%	4250
	11th to 20th	Night	45% 3 8% 9% 22% 14%	4817
	21st to end	Night	37% 4 5% 14% 31% 10%	6490

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	26% 17% 36% 16% 4 1	300
	11th to 20th	Day	26% 16% 33% 19% 5% 1	300
	21st to end	Day	27% 19% 34% 16% 4	330
February	1st to 10th	Day	28% 17% 36% 16% 3	300
	11th to 20th	Day	32% 16% 36% 14% 2	300
	21st to end	Day	27% 27% 33% 10% 3	249
March	1st to 10th	Day	28% 23% 30% 17% 3	300
	11th to 20th	Day	18% 23% 41% 14% 3	300
	21st to end	Day	22% 17% 41% 15% 4	330
April	1st to 10th	Day	21% 22% 35% 19% 3	300
	11th to 20th	Day	21% 20% 29% 20% 9% 1	450
	21st to end	Day	17% 14% 37% 24% 8% 1	500
May	1st to 10th	Day	15% 15% 37% 25% 7% 1	598
	11th to 20th	Day	14% 9% 30% 31% 14% 2	676
	21st to end	Day	10% 7% 31% 32% 16% 4	734
June	1st to 10th	Day	5% 4 16% 36% 31% 8%	680
	11th to 20th	Day	7% 2 18% 38% 30% 5%	680
	21st to end	Day	8% 2 13% 32% 34% 11%	680
July	1st to 10th	Day	8% 1 8% 32% 36% 15%	671
	11th to 20th	Day	4 1 6% 35% 39% 15%	668
	21st to end	Day	7% 1 6% 31% 43% 12%	739
August	1st to 10th	Day	3 1 4 29% 48% 15%	676
	11th to 20th	Day	5% 4 26% 49% 17%	599
	21st to end	Day	9% 2 6% 22% 37% 24%	501
September	1st to 10th	Day	6% 2 9% 30% 36% 17%	300
	11th to 20th	Day	10% 2 9% 30% 36% 13%	300
	21st to end	Day	9% 2 9% 34% 36% 9%	300
October	1st to 10th	Day	6% 4 18% 39% 27% 6%	300
	11th to 20th	Day	11% 7% 24% 32% 21% 5%	300
	21st to end	Day	24% 12% 23% 22% 15% 4	330
November	1st to 10th	Day	15% 7% 27% 35% 14% 2	300
	11th to 20th	Day	15% 15% 26% 34% 8% 2	300
	21st to end	Day	22% 19% 29% 20% 9% 1	300
December	1st to 10th	Day	19% 13% 38% 18% 8% 4	300
	11th to 20th	Day	24% 14% 35% 21% 4 1	300
	21st to end	Day	25% 15% 34% 19% 6% 1	330
January	1st to 10th	Night	21% 15% 32% 25% 6%	1000
	11th to 20th	Night	23% 15% 31% 25% 7%	1000
	21st to end	Night	24% 13% 33% 26% 5%	1100
February	1st to 10th	Night	26% 14% 36% 21% 3	935
	11th to 20th	Night	28% 14% 33% 22% 3	784
	21st to end	Night	25% 18% 38% 17% 2	498
March	1st to 10th	Night	25% 14% 36% 23% 3	600
	11th to 20th	Night	19% 12% 40% 24% 5%	600
	21st to end	Night	17% 15% 40% 23% 6%	660
April	1st to 10th	Night	17% 14% 38% 25% 6%	600
	11th to 20th	Night	16% 15% 34% 29% 6%	593
	21st to end	Night	18% 11% 39% 25% 8%	600
May	1st to 10th	Night	16% 12% 40% 26% 7% 1	600
	11th to 20th	Night	14% 5% 33% 34% 13% 1	563
	21st to end	Night	8% 4 33% 37% 16% 2	617
June	1st to 10th	Night	6% 2 16% 44% 29% 4	570
	11th to 20th	Night	4 2 21% 50% 22% 1	570
	21st to end	Night	5% 2 13% 44% 32% 4	570
July	1st to 10th	Night	5% 1 8% 45% 35% 5%	555
	11th to 20th	Night	3 9% 50% 34% 4	552
	21st to end	Night	6% 2 8% 47% 34% 4	624
August	1st to 10th	Night	2 1 8% 53% 33% 4	567
	11th to 20th	Night	5% 1 5% 47% 38% 4	564
	21st to end	Night	6% 1 7% 39% 40% 7%	627
September	1st to 10th	Night	7% 2 10% 34% 40% 8%	570
	11th to 20th	Night	11% 2 9% 33% 39% 6%	570
	21st to end	Night	9% 2 13% 35% 35% 6%	570
October	1st to 10th	Night	5% 2 15% 42% 30% 5%	662
	11th to 20th	Night	11% 5% 26% 38% 18% 2	760
	21st to end	Night	15% 7% 29% 31% 17% 2	836
November	1st to 10th	Night	13% 5% 28% 33% 20% 1	780
	11th to 20th	Night	13% 10% 29% 35% 13% 1	800
	21st to end	Night	19% 12% 31% 25% 12% 1	903
December	1st to 10th	Night	21% 11% 32% 26% 10%	1000
	11th to 20th	Night	26% 11% 32% 26% 5% 1	1000
	21st to end	Night	22% 12% 32% 29% 5%	1100

Page generated at 2025-05-08 08:33:54. Version ac07

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