Andrew Jackson State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Andrew Jackson State Park clear sky chart from 2005-11-06 to 2025-12-03.

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 5% 4 6% 8% 42%	127045
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 44%	123670
Transparency	Day	39% 6% 11% 20% 18% 6%	130691
	Night	38% 6% 10% 18% 21% 7%	128093
Seeing	Day	17% 10% 26% 25% 16% 6%	16779
	Night	17% 10% 25% 30% 17% 2	26844

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	15% 5% 2 5% 3 2 3 2 3 5% 56%	4056
	11th to 20th	Day	12% 6% 2 5% 3 3 3 2 3 4 58%	4060
	21st to end	Day	17% 8% 2 6% 4 3 4 3 4 4 44%	4466
February	1st to 10th	Day	15% 7% 3 6% 4 4 4 3 5% 6% 44%	1800
	11th to 20th	Day	22% 6% 2 4 3 3 3 3 4 4 45%	1918
	21st to end	Day	18% 7% 3 6% 4 4 3 3 4 5% 42%	1716
March	1st to 10th	Day	21% 7% 2 6% 4 3 4 3 4 4 41%	4935
	11th to 20th	Day	9% 5% 2 5% 4 3 4 3 4 6% 54%	4980
	21st to end	Day	17% 6% 3 6% 4 3 3 3 4 5% 47%	5465
April	1st to 10th	Day	12% 4 2 4 3 4 4 4 6% 7% 50%	2200
	11th to 20th	Day	12% 6% 2 5% 4 4 4 4 5% 6% 48%	2374
	21st to end	Day	11% 5% 2 5% 4 3 4 4 5% 8% 48%	2524
May	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 5% 8% 10% 36%	5862
	11th to 20th	Day	19% 7% 3 7% 4 5% 6% 4 6% 9% 31%	5861
	21st to end	Day	11% 6% 2 6% 4 4 5% 4 6% 8% 43%	6433
June	1st to 10th	Day	9% 4 3 7% 6% 5% 6% 5% 7% 11% 37%	2600
	11th to 20th	Day	7% 5% 2 5% 7% 5% 6% 5% 7% 10% 41%	2600
	21st to end	Day	7% 4 1 6% 6% 6% 6% 6% 8% 11% 39%	2600
July	1st to 10th	Day	8% 6% 3 8% 6% 6% 7% 5% 8% 10% 32%	5900
	11th to 20th	Day	6% 5% 2 7% 6% 6% 7% 6% 10% 13% 31%	5900
	21st to end	Day	9% 7% 3 8% 6% 6% 7% 5% 9% 11% 29%	6424
August	1st to 10th	Day	21% 8% 3 7% 5% 5% 5% 5% 8% 9% 23%	4234
	11th to 20th	Day	11% 6% 3 7% 5% 5% 6% 5% 8% 11% 34%	4174
	21st to end	Day	6% 4 2 5% 4 4 4 4 7% 9% 51%	4350
September	1st to 10th	Day	8% 4 2 5% 6% 6% 5% 5% 7% 10% 42%	2237
	11th to 20th	Day	13% 6% 3 7% 4 4 5% 4 7% 8% 39%	2200
	21st to end	Day	17% 6% 3 6% 5% 4 4 3 5% 6% 40%	2200
October	1st to 10th	Day	12% 6% 2 5% 4 3 3 3 4 6% 51%	2070
	11th to 20th	Day	13% 5% 1 4 3 3 2 2 3 5% 58%	2000
	21st to end	Day	13% 4 2 4 3 3 3 2 4 5% 57%	2200
November	1st to 10th	Day	13% 5% 2 5% 3 3 3 2 4 5% 55%	2057
	11th to 20th	Day	13% 5% 2 4 2 2 3 3 5% 6% 55%	1972
	21st to end	Day	14% 5% 2 5% 3 3 3 4 4 5% 51%	1890
December	1st to 10th	Day	13% 7% 2 5% 4 3 3 3 3 5% 52%	2948
	11th to 20th	Day	17% 7% 2 6% 4 4 3 3 4 6% 43%	3373
	21st to end	Day	21% 6% 2 4 3 3 3 3 4 6% 46%	4466
January	1st to 10th	Night	14% 4 2 5% 3 3 3 2 4 4 57%	5889
	11th to 20th	Night	12% 6% 2 5% 4 3 3 3 5% 5% 53%	5900
	21st to end	Night	17% 9% 2 5% 3 3 3 2 4 5% 47%	6490
February	1st to 10th	Night	15% 7% 2 6% 4 4 3 3 5% 5% 46%	2600
	11th to 20th	Night	21% 7% 2 5% 4 3 4 3 4 4 43%	2363
	21st to end	Night	16% 6% 2 5% 3 3 3 4 5% 6% 46%	1912
March	1st to 10th	Night	20% 7% 2 7% 4 3 3 3 4 5% 41%	4918
	11th to 20th	Night	11% 4 1 4 3 3 4 3 5% 7% 54%	4980
	21st to end	Night	15% 4 2 5% 4 3 4 3 5% 6% 48%	5467
April	1st to 10th	Night	13% 5% 2 5% 4 3 3 4 6% 7% 48%	2200
	11th to 20th	Night	11% 5% 2 5% 4 3 3 3 5% 7% 52%	1975
	21st to end	Night	11% 4 2 5% 4 4 4 4 5% 7% 50%	1892
May	1st to 10th	Night	12% 7% 2 6% 4 4 4 4 5% 9% 42%	4033
	11th to 20th	Night	19% 7% 2 6% 4 4 5% 3 7% 9% 33%	4032
	21st to end	Night	13% 6% 2 6% 4 4 5% 4 7% 9% 40%	4421
June	1st to 10th	Night	10% 7% 3 7% 5% 5% 6% 6% 7% 9% 35%	1800
	11th to 20th	Night	10% 6% 3 7% 4 5% 6% 5% 8% 10% 36%	1800
	21st to end	Night	8% 5% 3 6% 5% 6% 5% 6% 8% 11% 37%	1800
July	1st to 10th	Night	11% 8% 3 9% 5% 6% 7% 5% 7% 11% 27%	4058
	11th to 20th	Night	8% 6% 2 9% 6% 6% 8% 6% 11% 14% 25%	4057
	21st to end	Night	11% 9% 4 10% 7% 7% 7% 5% 7% 9% 24%	4427
August	1st to 10th	Night	24% 8% 3 7% 5% 5% 5% 4 6% 9% 24%	2915
	11th to 20th	Night	11% 7% 3 8% 4 5% 6% 5% 8% 11% 32%	2875
	21st to end	Night	6% 4 2 5% 4 5% 5% 5% 7% 10% 48%	3513
September	1st to 10th	Night	9% 5% 2 7% 5% 5% 4 4 7% 9% 43%	2158
	11th to 20th	Night	13% 6% 3 6% 5% 5% 5% 4 6% 7% 41%	2200
	21st to end	Night	17% 7% 2 7% 4 4 4 3 6% 6% 40%	2200
October	1st to 10th	Night	13% 5% 2 5% 3 4 4 3 5% 6% 51%	2330
	11th to 20th	Night	13% 5% 2 5% 3 3 3 2 4 6% 55%	2400
	21st to end	Night	12% 6% 2 5% 3 3 2 2 4 5% 56%	2640
November	1st to 10th	Night	13% 6% 2 5% 3 3 3 3 3 5% 53%	2461
	11th to 20th	Night	12% 6% 2 5% 4 3 4 3 4 5% 53%	2645
	21st to end	Night	12% 5% 2 5% 4 3 4 3 6% 6% 50%	2730
December	1st to 10th	Night	15% 6% 2 5% 3 2 3 3 4 5% 52%	4277
	11th to 20th	Night	18% 7% 3 6% 4 3 3 3 4 6% 44%	4822
	21st to end	Night	20% 5% 2 6% 3 3 3 3 4 6% 46%	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	33% 2 5% 20% 33% 7%	4057
	11th to 20th	Day	32% 3 5% 14% 36% 10%	4060
	21st to end	Day	43% 3 4 18% 23% 10%	4466
February	1st to 10th	Day	41% 4 9% 22% 19% 5%	1800
	11th to 20th	Day	43% 3 6% 18% 24% 5%	1928
	21st to end	Day	45% 4 7% 15% 22% 7%	1716
March	1st to 10th	Day	46% 5% 6% 14% 19% 11%	4935
	11th to 20th	Day	31% 5% 7% 13% 26% 18%	4980
	21st to end	Day	42% 4 5% 21% 22% 7%	5465
April	1st to 10th	Day	33% 4 10% 21% 26% 6%	2200
	11th to 20th	Day	36% 5% 9% 20% 22% 9%	2374
	21st to end	Day	35% 6% 11% 22% 21% 4	2524
May	1st to 10th	Day	40% 8% 17% 22% 11% 1	5897
	11th to 20th	Day	50% 6% 14% 18% 12% 1	5865
	21st to end	Day	37% 8% 12% 21% 19% 3	6447
June	1st to 10th	Day	39% 10% 14% 24% 11% 2	2600
	11th to 20th	Day	35% 11% 17% 21% 14% 2	2600
	21st to end	Day	34% 12% 16% 22% 15% 2	2600
July	1st to 10th	Day	44% 9% 17% 22% 7% 1	5835
	11th to 20th	Day	40% 11% 31% 15% 3 1	5831
	21st to end	Day	46% 11% 16% 21% 6%	6240
August	1st to 10th	Day	55% 9% 17% 15% 4	4221
	11th to 20th	Day	41% 10% 16% 20% 11% 1	4213
	21st to end	Day	28% 8% 15% 31% 16% 2	4350
September	1st to 10th	Day	34% 9% 15% 19% 19% 4	2237
	11th to 20th	Day	40% 7% 12% 17% 20% 3	2200
	21st to end	Day	44% 7% 8% 20% 15% 5%	2200
October	1st to 10th	Day	31% 5% 6% 21% 28% 10%	3369
	11th to 20th	Day	20% 3 5% 18% 28% 26%	3240
	21st to end	Day	26% 3 5% 24% 26% 16%	3538
November	1st to 10th	Day	32% 4 7% 19% 29% 10%	2057
	11th to 20th	Day	30% 4 8% 22% 28% 9%	1972
	21st to end	Day	35% 5% 8% 21% 23% 8%	1890
December	1st to 10th	Day	37% 3 5% 18% 28% 9%	2948
	11th to 20th	Day	43% 4 7% 18% 21% 6%	3370
	21st to end	Day	40% 4 9% 24% 21% 2	4466
January	1st to 10th	Night	31% 3 5% 17% 36% 7%	5889
	11th to 20th	Night	33% 4 6% 15% 34% 8%	5900
	21st to end	Night	42% 3 3 16% 28% 8%	6490
February	1st to 10th	Night	41% 4 9% 20% 21% 7%	2600
	11th to 20th	Night	45% 4 6% 16% 23% 7%	2364
	21st to end	Night	37% 5% 9% 17% 22% 8%	1912
March	1st to 10th	Night	44% 5% 6% 12% 26% 7%	4918
	11th to 20th	Night	30% 4 7% 13% 29% 18%	4980
	21st to end	Night	38% 4 7% 22% 21% 9%	5467
April	1st to 10th	Night	34% 5% 10% 20% 24% 7%	2200
	11th to 20th	Night	32% 5% 9% 23% 22% 10%	1975
	21st to end	Night	33% 7% 11% 25% 20% 4	1892
May	1st to 10th	Night	39% 7% 16% 22% 14% 1	4060
	11th to 20th	Night	47% 7% 16% 19% 11%	4033
	21st to end	Night	36% 8% 14% 25% 14% 2	4429
June	1st to 10th	Night	42% 10% 14% 20% 11% 2	1800
	11th to 20th	Night	39% 11% 17% 20% 12% 1	1800
	21st to end	Night	36% 13% 18% 18% 12% 3	1800
July	1st to 10th	Night	49% 9% 19% 16% 6% 1	4015
	11th to 20th	Night	45% 15% 25% 10% 3 1	4006
	21st to end	Night	53% 9% 16% 16% 5%	4297
August	1st to 10th	Night	57% 7% 18% 15% 3 1	2904
	11th to 20th	Night	43% 9% 22% 17% 7% 1	2902
	21st to end	Night	30% 8% 13% 27% 19% 4	3513
September	1st to 10th	Night	35% 9% 14% 20% 16% 5%	2158
	11th to 20th	Night	41% 7% 14% 16% 20% 2	2200
	21st to end	Night	43% 7% 11% 17% 16% 5%	2200
October	1st to 10th	Night	34% 5% 8% 21% 26% 6%	3811
	11th to 20th	Night	22% 3 5% 18% 29% 24%	3899
	21st to end	Night	28% 2 5% 21% 26% 17%	4252
November	1st to 10th	Night	34% 4 7% 17% 27% 12%	2461
	11th to 20th	Night	34% 3 7% 17% 27% 12%	2645
	21st to end	Night	34% 4 6% 22% 26% 8%	2730
December	1st to 10th	Night	35% 4 6% 18% 29% 9%	4277
	11th to 20th	Night	43% 4 11% 15% 18% 9%	4824
	21st to end	Night	41% 3 9% 23% 22% 2	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	24% 27% 36% 12% 2	300
	11th to 20th	Day	29% 20% 33% 15% 4	300
	21st to end	Day	25% 23% 37% 13% 2	330
February	1st to 10th	Day	22% 21% 40% 13% 4	300
	11th to 20th	Day	40% 18% 34% 8% 1	300
	21st to end	Day	26% 20% 34% 17% 2	315
March	1st to 10th	Day	26% 18% 32% 18% 6%	500
	11th to 20th	Day	22% 20% 38% 16% 3 1	500
	21st to end	Day	24% 19% 35% 17% 5% 1	550
April	1st to 10th	Day	22% 17% 34% 18% 7% 1	500
	11th to 20th	Day	16% 17% 33% 21% 11% 3	492
	21st to end	Day	15% 11% 31% 26% 14% 3	500
May	1st to 10th	Day	13% 16% 34% 24% 10% 3	503
	11th to 20th	Day	19% 6% 25% 27% 17% 6%	527
	21st to end	Day	15% 8% 23% 24% 21% 9%	573
June	1st to 10th	Day	12% 4 21% 34% 23% 6%	530
	11th to 20th	Day	11% 3 21% 32% 23% 10%	530
	21st to end	Day	8% 4 16% 33% 32% 7%	530
July	1st to 10th	Day	9% 3 10% 27% 35% 16%	525
	11th to 20th	Day	9% 1 10% 32% 33% 14%	524
	21st to end	Day	7% 2 12% 35% 33% 11%	576
August	1st to 10th	Day	19% 5% 15% 27% 23% 11%	526
	11th to 20th	Day	15% 2 13% 30% 26% 15%	519
	21st to end	Day	11% 2 14% 35% 25% 14%	583
September	1st to 10th	Day	9% 3 17% 33% 27% 11%	530
	11th to 20th	Day	16% 5% 16% 28% 25% 10%	530
	21st to end	Day	18% 6% 22% 29% 19% 5%	530
October	1st to 10th	Day	15% 6% 26% 26% 21% 6%	530
	11th to 20th	Day	12% 11% 26% 27% 18% 6%	530
	21st to end	Day	17% 10% 27% 25% 18% 3	583
November	1st to 10th	Day	19% 7% 30% 28% 12% 3	535
	11th to 20th	Day	17% 17% 36% 22% 7% 1	412
	21st to end	Day	15% 15% 37% 23% 8% 2	330
December	1st to 10th	Day	27% 16% 38% 15% 4	306
	11th to 20th	Day	22% 13% 35% 20% 9% 1	300
	21st to end	Day	27% 17% 32% 16% 7% 1	330
January	1st to 10th	Night	23% 19% 28% 24% 5%	800
	11th to 20th	Night	21% 16% 31% 27% 5%	800
	21st to end	Night	21% 15% 35% 26% 3	880
February	1st to 10th	Night	20% 15% 34% 27% 4	800
	11th to 20th	Night	26% 15% 39% 18% 1	783
	21st to end	Night	20% 18% 34% 24% 3	660
March	1st to 10th	Night	20% 14% 33% 28% 5%	800
	11th to 20th	Night	20% 16% 35% 22% 7%	800
	21st to end	Night	20% 15% 35% 24% 6%	880
April	1st to 10th	Night	17% 15% 35% 24% 8%	800
	11th to 20th	Night	14% 14% 31% 28% 11% 1	791
	21st to end	Night	13% 9% 30% 36% 12%	692
May	1st to 10th	Night	13% 10% 30% 36% 12%	600
	11th to 20th	Night	16% 6% 28% 33% 17% 1	591
	21st to end	Night	14% 3 18% 34% 29% 2	650
June	1st to 10th	Night	12% 3 21% 39% 23% 4	600
	11th to 20th	Night	12% 4 19% 35% 25% 6%	600
	21st to end	Night	10% 3 16% 35% 32% 5%	600
July	1st to 10th	Night	9% 2 14% 35% 33% 7%	585
	11th to 20th	Night	8% 2 9% 36% 38% 7%	582
	21st to end	Night	8% 3 12% 34% 36% 6%	657
August	1st to 10th	Night	16% 3 11% 29% 35% 6%	597
	11th to 20th	Night	15% 2 10% 31% 35% 7%	594
	21st to end	Night	11% 2 12% 30% 39% 6%	833
September	1st to 10th	Night	11% 3 12% 33% 36% 5%	800
	11th to 20th	Night	15% 3 13% 32% 33% 5%	800
	21st to end	Night	20% 6% 17% 33% 23% 3	800
October	1st to 10th	Night	16% 5% 20% 29% 25% 5%	800
	11th to 20th	Night	17% 7% 26% 29% 20% 2	800
	21st to end	Night	15% 10% 23% 31% 19% 2	880
November	1st to 10th	Night	16% 9% 26% 31% 16% 3	820
	11th to 20th	Night	15% 14% 30% 30% 10% 1	840
	21st to end	Night	15% 13% 29% 30% 13% 1	840
December	1st to 10th	Night	22% 15% 24% 32% 7% 1	809
	11th to 20th	Night	20% 11% 25% 33% 11%	800
	21st to end	Night	27% 13% 23% 29% 8%	880

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