Russellville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Russellville clear sky chart from 2005-11-06 to 2025-09-04.

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 3 5% 7% 46%	125103
	Night	14% 5% 2 5% 3 3 3 3 5% 7% 49%	123852
Transparency	Day	37% 4 10% 25% 19% 5%	128710
	Night	34% 4 10% 24% 21% 6%	128321
Seeing	Day	15% 5% 18% 25% 25% 11%	16556
	Night	16% 5% 19% 36% 21% 2	26278

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% 7% 2 7% 3 2 2 2 3 4 49%	4077
	11th to 20th	Day	10% 7% 2 6% 4 4 4 3 5% 5% 51%	4080
	21st to end	Day	22% 7% 2 4 3 3 3 2 3 4 48%	4488
February	1st to 10th	Day	24% 8% 3 5% 4 2 3 2 3 5% 43%	1800
	11th to 20th	Day	20% 7% 2 6% 3 3 3 3 4 5% 44%	1833
	21st to end	Day	21% 8% 3 5% 4 4 3 3 4 5% 40%	1749
March	1st to 10th	Day	20% 8% 2 6% 4 3 4 3 4 5% 41%	4936
	11th to 20th	Day	12% 4 2 5% 3 4 4 3 5% 6% 53%	4980
	21st to end	Day	15% 8% 3 6% 4 3 4 3 5% 6% 43%	5462
April	1st to 10th	Day	17% 6% 2 6% 4 3 4 4 5% 6% 43%	2365
	11th to 20th	Day	17% 6% 2 5% 4 3 4 3 5% 6% 44%	2374
	21st to end	Day	17% 7% 3 6% 5% 4 4 4 5% 6% 40%	2400
May	1st to 10th	Day	19% 8% 3 7% 4 4 4 4 5% 6% 36%	5537
	11th to 20th	Day	14% 6% 2 7% 5% 5% 4 4 6% 7% 38%	5862
	21st to end	Day	17% 7% 3 7% 5% 5% 5% 4 5% 7% 34%	6434
June	1st to 10th	Day	10% 5% 2 6% 5% 5% 5% 4 6% 9% 43%	2600
	11th to 20th	Day	6% 4 2 6% 6% 6% 6% 4 8% 10% 44%	2600
	21st to end	Day	5% 3 1 4 5% 5% 5% 5% 8% 9% 50%	2600
July	1st to 10th	Day	8% 4 2 6% 5% 5% 6% 5% 8% 12% 39%	5900
	11th to 20th	Day	5% 4 1 5% 3 4 5% 3 6% 9% 55%	5900
	21st to end	Day	7% 5% 2 7% 5% 5% 5% 4 7% 10% 42%	6422
August	1st to 10th	Day	4 3 1 4 3 4 3 3 6% 8% 61%	4234
	11th to 20th	Day	10% 5% 2 6% 4 4 4 4 6% 11% 44%	3957
	21st to end	Day	5% 4 1 4 4 4 5% 4 6% 8% 55%	4312
September	1st to 10th	Day	10% 5% 2 5% 4 5% 4 4 5% 7% 48%	2316
	11th to 20th	Day	12% 5% 1 5% 5% 4 4 3 6% 7% 48%	2224
	21st to end	Day	9% 4 1 5% 3 4 4 3 5% 6% 54%	2009
October	1st to 10th	Day	8% 4 1 5% 3 3 3 3 5% 6% 58%	1900
	11th to 20th	Day	14% 5% 1 4 2 3 3 2 4 6% 56%	1900
	21st to end	Day	20% 4 2 5% 3 3 3 3 4 4 49%	2090
November	1st to 10th	Day	14% 5% 2 4 3 3 3 2 4 6% 53%	1958
	11th to 20th	Day	14% 5% 1 4 2 2 3 3 4 6% 54%	1995
	21st to end	Day	19% 7% 2 5% 3 2 3 2 3 5% 47%	1680
December	1st to 10th	Day	17% 6% 2 6% 3 3 3 2 4 5% 50%	2610
	11th to 20th	Day	19% 8% 3 6% 3 4 4 3 4 5% 43%	3031
	21st to end	Day	23% 9% 3 7% 4 4 3 2 4 5% 37%	4488
January	1st to 10th	Night	17% 6% 2 5% 3 3 3 3 4 7% 48%	5888
	11th to 20th	Night	11% 4 2 4 3 3 3 3 4 6% 59%	5900
	21st to end	Night	21% 8% 2 5% 3 2 2 2 3 5% 46%	6490
February	1st to 10th	Night	20% 8% 2 5% 4 3 3 3 5% 5% 42%	2600
	11th to 20th	Night	18% 8% 2 6% 3 3 3 3 4 5% 45%	2453
	21st to end	Night	19% 5% 3 4 3 2 3 3 4 5% 48%	1898
March	1st to 10th	Night	21% 7% 2 6% 3 3 3 3 4 4 44%	4919
	11th to 20th	Night	12% 6% 2 5% 4 3 3 3 4 6% 52%	4980
	21st to end	Night	15% 6% 2 6% 4 4 4 3 4 8% 45%	5467
April	1st to 10th	Night	16% 5% 2 5% 4 3 3 3 5% 6% 49%	2035
	11th to 20th	Night	13% 5% 2 5% 4 4 3 3 4 5% 50%	1975
	21st to end	Night	17% 5% 2 5% 4 4 4 3 5% 7% 44%	2000
May	1st to 10th	Night	18% 7% 2 6% 4 4 4 4 5% 6% 39%	4360
	11th to 20th	Night	16% 8% 3 8% 3 4 5% 3 6% 7% 37%	4053
	21st to end	Night	18% 7% 3 6% 4 4 4 3 5% 7% 38%	4443
June	1st to 10th	Night	6% 4 2 5% 4 3 4 4 6% 9% 52%	1800
	11th to 20th	Night	5% 4 2 4 4 3 3 3 5% 10% 57%	1800
	21st to end	Night	4 2 1 3 3 3 4 4 5% 10% 61%	1800
July	1st to 10th	Night	8% 5% 2 6% 5% 5% 5% 5% 8% 10% 41%	4078
	11th to 20th	Night	5% 3 1 4 3 3 4 3 6% 9% 59%	4077
	21st to end	Night	5% 5% 2 5% 4 4 5% 5% 7% 10% 48%	4449
August	1st to 10th	Night	3 2 1 3 3 3 3 3 6% 8% 64%	2926
	11th to 20th	Night	5% 4 2 5% 4 4 4 3 6% 8% 56%	3095
	21st to end	Night	4 3 1 5% 4 4 4 3 6% 9% 57%	3586
September	1st to 10th	Night	8% 4 2 4 4 3 4 4 5% 7% 56%	1930
	11th to 20th	Night	10% 5% 2 4 4 4 4 4 6% 7% 51%	1951
	21st to end	Night	9% 4 1 4 3 3 3 3 5% 7% 59%	2152
October	1st to 10th	Night	9% 3 1 3 2 3 3 3 5% 6% 61%	2280
	11th to 20th	Night	13% 3 2 4 3 2 3 2 3 5% 61%	2280
	21st to end	Night	18% 5% 2 5% 2 3 2 2 3 4 54%	2508
November	1st to 10th	Night	13% 5% 2 5% 3 3 3 2 4 6% 55%	2340
	11th to 20th	Night	14% 3 2 4 2 2 3 3 4 6% 57%	2400
	21st to end	Night	16% 6% 2 4 3 3 3 2 4 6% 51%	2715
December	1st to 10th	Night	16% 6% 2 5% 3 3 3 2 3 4 51%	4580
	11th to 20th	Night	22% 6% 2 5% 3 3 2 2 3 4 47%	5154
	21st to end	Night	22% 8% 2 6% 3 4 3 3 4 5% 40%	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	41% 2 10% 25% 20% 2	4078
	11th to 20th	Day	35% 3 9% 25% 24% 5%	4080
	21st to end	Day	42% 3 5% 18% 25% 8%	4488
February	1st to 10th	Day	46% 3 10% 21% 16% 4	1800
	11th to 20th	Day	44% 4 7% 22% 19% 4	1842
	21st to end	Day	47% 3 7% 16% 18% 9%	1749
March	1st to 10th	Day	46% 3 6% 17% 15% 14%	4936
	11th to 20th	Day	33% 4 7% 19% 25% 13%	4980
	21st to end	Day	43% 3 9% 28% 16% 1	5464
April	1st to 10th	Day	41% 5% 9% 20% 21% 4	2365
	11th to 20th	Day	40% 5% 9% 22% 18% 6%	2374
	21st to end	Day	44% 6% 9% 22% 17% 2	2400
May	1st to 10th	Day	48% 6% 9% 21% 15% 1	5572
	11th to 20th	Day	43% 7% 12% 24% 13% 1	5866
	21st to end	Day	47% 6% 12% 17% 16% 2	6447
June	1st to 10th	Day	37% 7% 14% 26% 15% 1	2600
	11th to 20th	Day	34% 7% 15% 25% 18% 2	2600
	21st to end	Day	26% 9% 14% 29% 19% 4	2600
July	1st to 10th	Day	36% 5% 17% 31% 10% 1	5836
	11th to 20th	Day	26% 4 13% 38% 17% 2	5831
	21st to end	Day	37% 4 16% 30% 12%	6240
August	1st to 10th	Day	21% 5% 15% 32% 21% 6%	4220
	11th to 20th	Day	36% 5% 16% 30% 13% 1	3995
	21st to end	Day	26% 6% 14% 34% 17% 3	4311
September	1st to 10th	Day	35% 6% 10% 23% 18% 8%	2316
	11th to 20th	Day	35% 5% 12% 21% 22% 5%	2224
	21st to end	Day	31% 5% 9% 21% 28% 6%	2009
October	1st to 10th	Day	16% 3 5% 14% 39% 24%	3160
	11th to 20th	Day	20% 2 3 20% 38% 17%	3140
	21st to end	Day	33% 3 5% 30% 24% 6%	3428
November	1st to 10th	Day	32% 5% 8% 25% 22% 8%	1958
	11th to 20th	Day	30% 4 7% 24% 26% 9%	1995
	21st to end	Day	41% 3 8% 20% 24% 5%	1680
December	1st to 10th	Day	39% 2 7% 30% 19% 3	2610
	11th to 20th	Day	44% 3 6% 21% 22% 3	3028
	21st to end	Day	49% 5% 7% 23% 12% 4	4488
January	1st to 10th	Night	37% 3 9% 28% 21% 3	5888
	11th to 20th	Night	28% 3 9% 22% 32% 6%	5900
	21st to end	Night	43% 2 8% 16% 26% 5%	6490
February	1st to 10th	Night	44% 4 8% 22% 17% 4	2600
	11th to 20th	Night	42% 4 7% 22% 20% 6%	2454
	21st to end	Night	39% 3 7% 19% 23% 9%	1898
March	1st to 10th	Night	43% 4 6% 15% 18% 13%	4919
	11th to 20th	Night	34% 4 5% 24% 20% 13%	4980
	21st to end	Night	39% 4 10% 25% 19% 3	5467
April	1st to 10th	Night	36% 4 10% 23% 19% 8%	2035
	11th to 20th	Night	35% 5% 7% 24% 20% 9%	1975
	21st to end	Night	39% 6% 10% 23% 20% 3	2000
May	1st to 10th	Night	44% 6% 13% 21% 13% 2	4390
	11th to 20th	Night	45% 6% 13% 23% 12% 1	4054
	21st to end	Night	46% 5% 12% 20% 13% 4	4452
June	1st to 10th	Night	26% 7% 15% 30% 20% 3	1800
	11th to 20th	Night	23% 5% 12% 34% 23% 2	1800
	21st to end	Night	19% 6% 14% 31% 24% 7%	1800
July	1st to 10th	Night	36% 6% 16% 27% 14% 1	4035
	11th to 20th	Night	22% 4 14% 39% 19% 2	4026
	21st to end	Night	32% 5% 16% 30% 17% 1	4320
August	1st to 10th	Night	18% 4 15% 35% 24% 4	2916
	11th to 20th	Night	26% 4 19% 33% 15% 2	3123
	21st to end	Night	24% 5% 12% 31% 25% 3	3586
September	1st to 10th	Night	27% 6% 10% 27% 21% 9%	1930
	11th to 20th	Night	31% 6% 11% 21% 25% 6%	1951
	21st to end	Night	26% 5% 9% 22% 30% 8%	2152
October	1st to 10th	Night	15% 3 7% 14% 32% 30%	3800
	11th to 20th	Night	18% 2 3 16% 39% 22%	3779
	21st to end	Night	30% 2 4 24% 28% 11%	4120
November	1st to 10th	Night	31% 4 8% 23% 25% 9%	2340
	11th to 20th	Night	29% 4 6% 24% 27% 10%	2400
	21st to end	Night	36% 3 7% 22% 26% 5%	2715
December	1st to 10th	Night	39% 2 6% 32% 19% 3	4580
	11th to 20th	Night	43% 2 5% 22% 21% 7%	5156
	21st to end	Night	46% 4 9% 25% 13% 4	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	27% 5% 29% 26% 12% 2	300
	11th to 20th	Day	23% 10% 38% 22% 6%	300
	21st to end	Day	19% 10% 36% 25% 8% 2	330
February	1st to 10th	Day	29% 9% 28% 23% 10% 1	300
	11th to 20th	Day	25% 10% 35% 24% 5%	300
	21st to end	Day	30% 10% 33% 18% 8%	249
March	1st to 10th	Day	23% 11% 28% 26% 10% 1	300
	11th to 20th	Day	22% 18% 33% 19% 8%	300
	21st to end	Day	20% 14% 36% 21% 7% 2	330
April	1st to 10th	Day	22% 10% 31% 24% 10% 3	465
	11th to 20th	Day	22% 9% 27% 30% 10% 1	492
	21st to end	Day	20% 7% 27% 29% 13% 2	500
May	1st to 10th	Day	18% 8% 25% 32% 16% 1	557
	11th to 20th	Day	17% 6% 19% 29% 22% 7%	725
	21st to end	Day	12% 4 18% 32% 23% 10%	789
June	1st to 10th	Day	11% 3 11% 25% 34% 15%	730
	11th to 20th	Day	7% 2 11% 27% 36% 17%	730
	21st to end	Day	5% 2 10% 31% 33% 19%	730
July	1st to 10th	Day	6% 2 7% 23% 38% 23%	721
	11th to 20th	Day	5% 1 5% 26% 36% 25%	718
	21st to end	Day	6% 2 5% 23% 39% 25%	794
August	1st to 10th	Day	7% 2 6% 24% 45% 16%	726
	11th to 20th	Day	13% 2 5% 19% 40% 20%	591
	21st to end	Day	12% 1 3 16% 39% 30%	583
September	1st to 10th	Day	10% 1 5% 20% 44% 20%	502
	11th to 20th	Day	11% 2 9% 20% 38% 20%	434
	21st to end	Day	13% 2 13% 26% 28% 17%	300
October	1st to 10th	Day	6% 2 19% 27% 29% 16%	300
	11th to 20th	Day	13% 3 25% 30% 23% 5%	300
	21st to end	Day	25% 8% 24% 23% 15% 5%	330
November	1st to 10th	Day	18% 5% 25% 23% 23% 6%	300
	11th to 20th	Day	14% 5% 32% 29% 18% 2	300
	21st to end	Day	22% 14% 20% 23% 17% 4	300
December	1st to 10th	Day	20% 7% 35% 20% 14% 4	300
	11th to 20th	Day	24% 10% 29% 24% 12%	300
	21st to end	Day	25% 13% 28% 27% 6% 1	330
January	1st to 10th	Night	23% 8% 29% 35% 6%	1000
	11th to 20th	Night	20% 9% 30% 34% 6%	1000
	21st to end	Night	20% 6% 33% 36% 5%	1100
February	1st to 10th	Night	25% 8% 26% 36% 5%	1000
	11th to 20th	Night	20% 9% 33% 34% 3	899
	21st to end	Night	21% 11% 34% 33% 2	578
March	1st to 10th	Night	22% 6% 28% 40% 5%	600
	11th to 20th	Night	20% 10% 26% 37% 6%	600
	21st to end	Night	20% 8% 29% 36% 8%	660
April	1st to 10th	Night	18% 7% 32% 34% 9%	600
	11th to 20th	Night	14% 8% 30% 37% 11%	593
	21st to end	Night	20% 5% 28% 34% 13%	600
May	1st to 10th	Night	15% 5% 18% 48% 15%	600
	11th to 20th	Night	16% 4 19% 35% 24% 1	591
	21st to end	Night	12% 3 12% 42% 26% 4	650
June	1st to 10th	Night	7% 3 9% 38% 40% 5%	600
	11th to 20th	Night	6% 1 7% 40% 43% 4	600
	21st to end	Night	3 1 7% 34% 49% 6%	600
July	1st to 10th	Night	6% 1 5% 30% 49% 9%	585
	11th to 20th	Night	5% 1 4 29% 50% 12%	582
	21st to end	Night	4 1 3 30% 51% 11%	657
August	1st to 10th	Night	6% 1 4 32% 51% 6%	597
	11th to 20th	Night	9% 1 3 36% 43% 8%	594
	21st to end	Night	7% 1 5% 28% 52% 7%	660
September	1st to 10th	Night	9% 2 5% 29% 50% 5%	579
	11th to 20th	Night	13% 1 6% 33% 44% 4	570
	21st to end	Night	10% 1 10% 35% 38% 4	632
October	1st to 10th	Night	10% 2 10% 38% 38% 3	760
	11th to 20th	Night	14% 3 20% 44% 19% 1	760
	21st to end	Night	20% 6% 19% 36% 17% 1	836
November	1st to 10th	Night	15% 5% 18% 43% 19% 1	780
	11th to 20th	Night	15% 7% 22% 43% 13% 1	800
	21st to end	Night	18% 9% 23% 37% 14%	915
December	1st to 10th	Night	22% 5% 26% 39% 7%	1000
	11th to 20th	Night	24% 7% 21% 41% 7%	1000
	21st to end	Night	24% 8% 25% 36% 7%	1100

Page generated at 2025-09-01 00:51:09. Version ac07

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