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 2026-09-14.

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	12% 6% 2 6% 4 4 4 4 6% 8% 43%	148605
	Night	13% 7% 2 5% 3 3 4 3 5% 7% 47%	142836
Transparency	Day	38% 6% 12% 21% 17% 7%	152267
	Night	36% 5% 12% 20% 18% 9%	147241
Seeing	Day	14% 9% 22% 27% 22% 7%	17445
	Night	15% 9% 26% 32% 16% 2	27183

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	17% 8% 3 6% 3 3 3 2 4 6% 45%	5289
	11th to 20th	Day	13% 6% 2 6% 3 3 3 3 4 5% 52%	5310
	21st to end	Day	28% 8% 2 7% 4 2 2 2 4 5% 35%	5812
February	1st to 10th	Day	20% 8% 3 7% 3 3 4 3 4 6% 39%	1974
	11th to 20th	Day	21% 8% 2 7% 5% 3 3 3 4 5% 39%	2049
	21st to end	Day	18% 8% 2 6% 4 3 4 3 4 6% 42%	1898
March	1st to 10th	Day	17% 10% 3 8% 5% 4 4 3 5% 6% 37%	5046
	11th to 20th	Day	13% 7% 2 5% 4 4 4 3 5% 6% 48%	5090
	21st to end	Day	17% 8% 2 6% 4 4 4 3 5% 6% 40%	5583
April	1st to 10th	Day	16% 8% 3 7% 5% 5% 4 4 4 6% 38%	2310
	11th to 20th	Day	16% 7% 3 7% 5% 5% 4 4 6% 7% 38%	2450
	21st to end	Day	13% 7% 3 6% 5% 5% 5% 4 5% 8% 40%	2520
May	1st to 10th	Day	21% 8% 3 7% 4 5% 5% 3 5% 6% 33%	7315
	11th to 20th	Day	12% 6% 3 6% 5% 5% 5% 4 6% 8% 40%	7627
	21st to end	Day	12% 7% 2 8% 5% 6% 6% 5% 7% 10% 32%	8392
June	1st to 10th	Day	7% 5% 2 6% 6% 7% 6% 6% 8% 9% 38%	2730
	11th to 20th	Day	7% 4 1 6% 6% 6% 6% 5% 7% 9% 43%	2730
	21st to end	Day	6% 5% 2 7% 6% 7% 7% 6% 8% 9% 36%	2730
July	1st to 10th	Day	7% 4 2 6% 5% 5% 6% 5% 8% 13% 41%	7680
	11th to 20th	Day	8% 6% 2 6% 6% 6% 6% 5% 8% 12% 35%	7680
	21st to end	Day	8% 5% 2 5% 4 4 4 4 6% 10% 47%	8337
August	1st to 10th	Day	2 1 1 2 3 3 4 4 6% 9% 65%	6014
	11th to 20th	Day	2 2 1 3 3 4 5% 4 7% 13% 56%	5784
	21st to end	Day	5% 4 1 6% 4 5% 5% 5% 7% 10% 47%	5986
September	1st to 10th	Day	7% 5% 2 7% 5% 6% 6% 5% 7% 8% 41%	2310
	11th to 20th	Day	12% 6% 2 7% 5% 5% 5% 4 6% 7% 40%	2233
	21st to end	Day	7% 4 1 6% 4 5% 5% 3 5% 7% 52%	2200
October	1st to 10th	Day	6% 4 2 4 3 3 4 3 4 6% 60%	2081
	11th to 20th	Day	11% 5% 1 5% 3 3 4 3 5% 5% 56%	2000
	21st to end	Day	14% 6% 2 4 3 3 3 3 5% 5% 56%	2200
November	1st to 10th	Day	11% 5% 2 4 4 5% 4 3 5% 7% 48%	2058
	11th to 20th	Day	11% 6% 2 6% 3 3 4 3 5% 7% 51%	2100
	21st to end	Day	16% 8% 2 6% 4 4 3 3 5% 5% 44%	1989
December	1st to 10th	Day	22% 6% 2 5% 3 3 3 3 4 5% 43%	3030
	11th to 20th	Day	16% 9% 3 6% 4 4 4 2 5% 6% 42%	3481
	21st to end	Day	17% 8% 2 6% 4 3 3 3 4 5% 46%	4587
January	1st to 10th	Night	18% 7% 2 5% 3 3 3 2 3 6% 49%	7634
	11th to 20th	Night	11% 6% 2 5% 3 3 4 2 4 5% 55%	7680
	21st to end	Night	29% 9% 2 6% 3 3 3 2 3 5% 35%	8402
February	1st to 10th	Night	19% 9% 3 6% 3 3 3 2 4 5% 42%	2662
	11th to 20th	Night	22% 9% 2 5% 2 3 3 2 4 5% 42%	2458
	21st to end	Night	20% 8% 2 6% 3 3 3 3 4 5% 43%	1906
March	1st to 10th	Night	21% 11% 2 5% 4 3 3 3 4 6% 39%	5029
	11th to 20th	Night	15% 7% 2 6% 4 3 3 3 4 6% 47%	5090
	21st to end	Night	19% 10% 3 6% 4 4 3 3 3 4 41%	5588
April	1st to 10th	Night	14% 7% 3 6% 5% 4 4 3 5% 6% 42%	2310
	11th to 20th	Night	13% 7% 2 6% 4 4 4 3 5% 8% 44%	2117
	21st to end	Night	17% 6% 2 5% 3 4 4 3 5% 7% 43%	2100
May	1st to 10th	Night	22% 11% 3 7% 4 3 4 3 5% 8% 30%	5535
	11th to 20th	Night	15% 8% 3 7% 4 4 4 3 5% 7% 40%	5265
	21st to end	Night	13% 9% 3 7% 4 4 5% 4 7% 10% 34%	5793
June	1st to 10th	Night	7% 4 1 5% 3 4 4 3 6% 10% 51%	1890
	11th to 20th	Night	5% 3 1 4 3 3 4 5% 7% 11% 55%	1890
	21st to end	Night	4 5% 2 4 4 4 5% 5% 9% 11% 47%	1890
July	1st to 10th	Night	5% 4 2 5% 4 4 5% 4 8% 15% 45%	5308
	11th to 20th	Night	6% 5% 2 5% 5% 4 5% 4 7% 11% 45%	5307
	21st to end	Night	8% 5% 2 5% 4 4 4 4 5% 10% 51%	5770
August	1st to 10th	Night	1 1 1 2 2 1 2 2 4 10% 74%	4156
	11th to 20th	Night	2 2 1 2 2 3 3 3 6% 12% 64%	4275
	21st to end	Night	4 3 1 4 4 4 5% 5% 7% 12% 52%	5134
September	1st to 10th	Night	6% 5% 2 6% 4 4 5% 4 6% 8% 50%	2310
	11th to 20th	Night	8% 7% 2 7% 4 4 4 5% 7% 8% 44%	2233
	21st to end	Night	8% 4 1 4 3 3 3 3 6% 7% 57%	2200
October	1st to 10th	Night	5% 3 1 4 3 3 3 4 5% 7% 63%	2297
	11th to 20th	Night	9% 5% 2 4 2 3 3 2 4 5% 62%	2400
	21st to end	Night	13% 5% 2 4 3 2 3 2 3 5% 60%	2640
November	1st to 10th	Night	11% 6% 2 4 3 3 3 2 5% 6% 54%	2460
	11th to 20th	Night	10% 6% 3 5% 4 4 4 3 4 5% 53%	2520
	21st to end	Night	16% 7% 2 6% 3 3 4 3 4 6% 45%	2628
December	1st to 10th	Night	21% 9% 3 7% 4 3 3 3 4 5% 39%	4380
	11th to 20th	Night	18% 10% 3 6% 3 3 3 2 3 5% 44%	4946
	21st to end	Night	15% 8% 2 5% 3 3 2 2 4 4 52%	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	42% 3 6% 23% 20% 6%	5290
	11th to 20th	Day	36% 2 4 17% 28% 12%	5310
	21st to end	Day	54% 2 3 13% 16% 12%	5812
February	1st to 10th	Day	48% 3 6% 14% 18% 12%	1974
	11th to 20th	Day	50% 3 7% 15% 16% 10%	2059
	21st to end	Day	45% 4 8% 15% 17% 11%	1898
March	1st to 10th	Day	48% 4 8% 11% 19% 10%	5046
	11th to 20th	Day	37% 5% 7% 12% 21% 19%	5090
	21st to end	Day	44% 4 9% 21% 17% 5%	5585
April	1st to 10th	Day	48% 6% 5% 16% 16% 9%	2310
	11th to 20th	Day	45% 6% 9% 15% 17% 9%	2450
	21st to end	Day	43% 5% 8% 19% 20% 5%	2520
May	1st to 10th	Day	51% 6% 9% 21% 11% 2	7350
	11th to 20th	Day	40% 6% 14% 18% 20% 2	7631
	21st to end	Day	43% 8% 14% 23% 10% 1	8405
June	1st to 10th	Day	37% 9% 16% 23% 15% 1	2730
	11th to 20th	Day	35% 8% 15% 24% 15% 3	2730
	21st to end	Day	41% 9% 15% 22% 12% 1	2730
July	1st to 10th	Day	33% 9% 30% 26% 3	7616
	11th to 20th	Day	39% 9% 23% 21% 8%	7611
	21st to end	Day	32% 7% 15% 35% 12% 1	8155
August	1st to 10th	Day	15% 6% 18% 32% 23% 6%	6000
	11th to 20th	Day	18% 6% 29% 36% 9% 1	5823
	21st to end	Day	30% 9% 14% 30% 15% 2	5985
September	1st to 10th	Day	37% 9% 14% 18% 16% 7%	2310
	11th to 20th	Day	42% 6% 13% 19% 16% 5%	2233
	21st to end	Day	32% 6% 11% 21% 18% 13%	2200
October	1st to 10th	Day	17% 3 6% 13% 24% 38%	3393
	11th to 20th	Day	21% 3 5% 18% 34% 20%	3240
	21st to end	Day	25% 3 5% 15% 37% 14%	3538
November	1st to 10th	Day	35% 6% 9% 17% 23% 11%	2058
	11th to 20th	Day	34% 4 9% 17% 23% 13%	2100
	21st to end	Day	42% 5% 6% 18% 20% 10%	1989
December	1st to 10th	Day	44% 3 7% 16% 24% 5%	3030
	11th to 20th	Day	43% 4 7% 12% 22% 11%	3479
	21st to end	Day	41% 3 5% 14% 27% 9%	4587
January	1st to 10th	Night	39% 3 8% 21% 20% 9%	7635
	11th to 20th	Night	33% 2 5% 18% 29% 13%	7680
	21st to end	Night	55% 2 4 13% 16% 11%	8402
February	1st to 10th	Night	46% 3 6% 13% 18% 14%	2662
	11th to 20th	Night	46% 3 7% 16% 18% 11%	2458
	21st to end	Night	45% 4 7% 13% 17% 14%	1906
March	1st to 10th	Night	47% 4 7% 12% 20% 10%	5029
	11th to 20th	Night	39% 5% 7% 15% 15% 19%	5090
	21st to end	Night	47% 4 7% 14% 19% 8%	5588
April	1st to 10th	Night	42% 5% 9% 16% 17% 11%	2310
	11th to 20th	Night	40% 5% 10% 18% 16% 11%	2117
	21st to end	Night	40% 5% 10% 18% 21% 6%	2100
May	1st to 10th	Night	53% 6% 9% 20% 10% 2	5565
	11th to 20th	Night	44% 5% 10% 19% 19% 3	5266
	21st to end	Night	44% 7% 17% 23% 8% 1	5805
June	1st to 10th	Night	27% 8% 17% 30% 17% 1	1890
	11th to 20th	Night	22% 7% 19% 30% 18% 4	1890
	21st to end	Night	26% 10% 20% 28% 14% 1	1890
July	1st to 10th	Night	27% 8% 36% 27% 3	5265
	11th to 20th	Night	33% 7% 28% 25% 8%	5256
	21st to end	Night	29% 7% 16% 35% 13%	5641
August	1st to 10th	Night	9% 4 22% 38% 23% 5%	4146
	11th to 20th	Night	14% 6% 31% 39% 10% 1	4302
	21st to end	Night	24% 9% 19% 32% 14% 2	5134
September	1st to 10th	Night	31% 8% 21% 20% 13% 8%	2310
	11th to 20th	Night	37% 8% 16% 18% 16% 6%	2233
	21st to end	Night	26% 6% 13% 23% 20% 12%	2200
October	1st to 10th	Night	14% 3 7% 16% 19% 40%	3752
	11th to 20th	Night	16% 2 4 24% 30% 24%	3899
	21st to end	Night	23% 3 5% 15% 38% 16%	4252
November	1st to 10th	Night	31% 5% 11% 19% 23% 11%	2460
	11th to 20th	Night	34% 3 9% 18% 22% 14%	2520
	21st to end	Night	40% 4 8% 16% 20% 11%	2628
December	1st to 10th	Night	49% 3 5% 16% 21% 6%	4380
	11th to 20th	Night	44% 3 7% 9% 22% 14%	4947
	21st to end	Night	37% 4 5% 14% 30% 10%	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	26% 17% 35% 17% 4 1	330
	11th to 20th	Day	26% 15% 33% 19% 5% 1	330
	21st to end	Day	29% 19% 33% 16% 3	363
February	1st to 10th	Day	25% 17% 38% 17% 2	330
	11th to 20th	Day	32% 17% 35% 15% 2	330
	21st to end	Day	25% 26% 35% 10% 3	273
March	1st to 10th	Day	27% 23% 29% 18% 2	330
	11th to 20th	Day	19% 22% 41% 15% 3	330
	21st to end	Day	20% 16% 39% 19% 6% 1	363
April	1st to 10th	Day	21% 22% 35% 19% 4	330
	11th to 20th	Day	21% 20% 31% 19% 8% 1	488
	21st to end	Day	19% 14% 36% 23% 7% 1	540
May	1st to 10th	Day	16% 15% 37% 24% 7% 1	643
	11th to 20th	Day	14% 10% 32% 29% 12% 2	775
	21st to end	Day	10% 8% 31% 32% 15% 3	844
June	1st to 10th	Day	6% 5% 19% 35% 28% 7%	780
	11th to 20th	Day	9% 3 18% 38% 28% 5%	780
	21st to end	Day	8% 2 14% 33% 33% 10%	780
July	1st to 10th	Day	7% 1 9% 33% 35% 15%	771
	11th to 20th	Day	5% 2 6% 35% 38% 14%	768
	21st to end	Day	6% 1 6% 31% 44% 11%	849
August	1st to 10th	Day	3 1 5% 28% 48% 16%	776
	11th to 20th	Day	4 4 25% 50% 17%	692
	21st to end	Day	9% 3 6% 22% 38% 23%	585
September	1st to 10th	Day	6% 2 11% 30% 34% 16%	360
	11th to 20th	Day	9% 2 8% 29% 38% 15%	339
	21st to end	Day	8% 2 10% 36% 34% 9%	330
October	1st to 10th	Day	5% 4 18% 40% 28% 6%	330
	11th to 20th	Day	11% 7% 24% 31% 23% 5%	330
	21st to end	Day	23% 12% 24% 23% 15% 4	363
November	1st to 10th	Day	15% 7% 28% 34% 14% 3	330
	11th to 20th	Day	14% 14% 27% 35% 8% 2	330
	21st to end	Day	22% 18% 31% 20% 8% 1	330
December	1st to 10th	Day	21% 13% 38% 17% 8% 4	330
	11th to 20th	Day	24% 14% 34% 21% 6% 1	330
	21st to end	Day	24% 15% 34% 20% 7% 1	363
January	1st to 10th	Night	21% 15% 33% 25% 6%	1050
	11th to 20th	Night	22% 16% 31% 24% 6%	1050
	21st to end	Night	25% 13% 32% 26% 5%	1155
February	1st to 10th	Night	25% 14% 35% 22% 3	982
	11th to 20th	Night	27% 15% 33% 22% 3	824
	21st to end	Night	24% 18% 38% 18% 2	522
March	1st to 10th	Night	26% 14% 35% 22% 3	630
	11th to 20th	Night	20% 12% 39% 24% 5%	630
	21st to end	Night	16% 14% 40% 23% 6%	693
April	1st to 10th	Night	18% 15% 37% 25% 5%	630
	11th to 20th	Night	17% 15% 34% 28% 6%	623
	21st to end	Night	19% 11% 38% 24% 8%	630
May	1st to 10th	Night	17% 12% 40% 25% 6% 1	630
	11th to 20th	Night	15% 6% 33% 32% 12% 1	621
	21st to end	Night	9% 5% 33% 37% 15% 2	683
June	1st to 10th	Night	7% 3 17% 43% 27% 3	630
	11th to 20th	Night	5% 2 22% 49% 20% 1	630
	21st to end	Night	4 2 15% 45% 30% 4	630
July	1st to 10th	Night	5% 1 8% 45% 35% 5%	615
	11th to 20th	Night	4 9% 51% 32% 3	612
	21st to end	Night	6% 1 9% 47% 33% 4	690
August	1st to 10th	Night	2 1 7% 52% 33% 4	627
	11th to 20th	Night	5% 1 4 49% 37% 4	624
	21st to end	Night	6% 1 8% 39% 38% 7%	693
September	1st to 10th	Night	6% 2 11% 34% 40% 7%	630
	11th to 20th	Night	11% 2 9% 33% 40% 5%	609
	21st to end	Night	9% 2 13% 36% 35% 5%	600
October	1st to 10th	Night	5% 2 15% 42% 30% 5%	697
	11th to 20th	Night	11% 5% 26% 38% 19% 3	800
	21st to end	Night	15% 7% 29% 30% 17% 2	880
November	1st to 10th	Night	13% 5% 27% 34% 20% 1	820
	11th to 20th	Night	13% 10% 29% 35% 13%	840
	21st to end	Night	19% 12% 31% 26% 11% 1	948
December	1st to 10th	Night	23% 11% 31% 26% 9%	1050
	11th to 20th	Night	26% 11% 32% 26% 5% 1	1050
	21st to end	Night	23% 12% 31% 29% 5%	1155

Page generated at 2026-09-11 03:11:53. Version ac07

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