Bentonville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bentonville clear sky chart from 2005-11-06 to 2026-03-03.

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	12% 7% 3 6% 4 4 4 3 5% 7% 46%	130782
	Night	11% 7% 2 6% 3 3 4 3 5% 6% 50%	130664
Transparency	Day	37% 5% 10% 26% 19% 4	134394
	Night	34% 4 10% 26% 21% 5%	135129
Seeing	Day	16% 10% 28% 26% 16% 4	17201
	Night	15% 10% 30% 29% 14% 1	27174

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	14% 9% 4 6% 4 3 3 2 4 5% 45%	5289
	11th to 20th	Day	6% 7% 3 7% 4 3 3 2 3 4 55%	5310
	21st to end	Day	17% 10% 3 5% 3 2 2 3 4 4 48%	5812
February	1st to 10th	Day	17% 10% 3 6% 4 4 3 3 3 5% 40%	1890
	11th to 20th	Day	15% 10% 3 5% 4 3 3 3 4 7% 42%	1845
	21st to end	Day	15% 8% 2 6% 4 3 4 4 4 6% 43%	1882
March	1st to 10th	Day	13% 8% 2 6% 4 3 4 3 4 5% 47%	4958
	11th to 20th	Day	9% 6% 2 5% 3 4 4 3 4 7% 53%	4980
	21st to end	Day	14% 8% 4 7% 5% 5% 5% 3 5% 7% 36%	5462
April	1st to 10th	Day	14% 7% 2 6% 4 4 3 3 6% 7% 43%	2310
	11th to 20th	Day	16% 8% 3 6% 4 4 4 3 5% 6% 41%	2374
	21st to end	Day	18% 10% 3 7% 5% 3 4 3 5% 4 38%	2408
May	1st to 10th	Day	18% 8% 3 7% 5% 5% 5% 4 5% 6% 35%	5862
	11th to 20th	Day	11% 7% 3 7% 6% 5% 5% 4 6% 7% 40%	5862
	21st to end	Day	19% 7% 2 7% 5% 4 4 4 5% 7% 36%	6434
June	1st to 10th	Day	8% 5% 1 6% 4 4 4 5% 7% 11% 44%	2600
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 4 6% 8% 46%	2600
	21st to end	Day	4 3 1 4 4 4 4 5% 8% 9% 54%	2600
July	1st to 10th	Day	7% 5% 2 6% 5% 5% 6% 5% 7% 10% 41%	5900
	11th to 20th	Day	6% 5% 2 6% 4 4 5% 4 6% 10% 48%	5900
	21st to end	Day	5% 3 2 5% 4 4 5% 5% 7% 11% 49%	6422
August	1st to 10th	Day	5% 3 2 4 4 4 4 3 6% 9% 57%	4234
	11th to 20th	Day	8% 5% 2 6% 4 5% 5% 4 6% 8% 47%	4120
	21st to end	Day	5% 4 2 5% 4 4 5% 4 5% 8% 54%	4312
September	1st to 10th	Day	10% 6% 2 4 4 4 3 3 4 7% 53%	2400
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 4 6% 7% 45%	2234
	21st to end	Day	7% 5% 2 6% 3 4 4 3 5% 8% 54%	2170
October	1st to 10th	Day	9% 4 2 5% 4 3 3 3 6% 6% 55%	2000
	11th to 20th	Day	13% 4 2 4 2 3 3 2 4 6% 58%	2000
	21st to end	Day	19% 6% 2 6% 3 2 2 2 3 4 50%	2200
November	1st to 10th	Day	12% 6% 1 4 3 3 3 3 3 6% 56%	2058
	11th to 20th	Day	12% 7% 2 5% 4 3 3 3 4 5% 51%	2037
	21st to end	Day	17% 8% 3 4 2 2 4 3 3 6% 47%	1769
December	1st to 10th	Day	12% 9% 3 4 3 3 3 3 3 4 53%	2690
	11th to 20th	Day	13% 9% 3 6% 4 3 3 2 4 5% 49%	3271
	21st to end	Day	20% 16% 6% 6% 3 3 3 3 4 5% 31%	4587
January	1st to 10th	Night	13% 8% 3 8% 5% 3 3 3 4 6% 44%	7634
	11th to 20th	Night	7% 6% 2 6% 4 3 4 3 4 6% 56%	7680
	21st to end	Night	17% 9% 3 6% 4 4 3 3 3 5% 43%	8402
February	1st to 10th	Night	15% 9% 3 6% 3 4 4 3 6% 6% 43%	2730
	11th to 20th	Night	15% 9% 3 7% 4 3 3 3 4 5% 45%	2663
	21st to end	Night	14% 8% 2 6% 3 4 3 3 5% 4 48%	1938
March	1st to 10th	Night	15% 10% 3 6% 3 4 3 2 4 4 46%	4941
	11th to 20th	Night	9% 7% 2 5% 3 3 4 3 5% 6% 53%	4980
	21st to end	Night	11% 7% 3 7% 4 5% 4 4 5% 8% 44%	5467
April	1st to 10th	Night	14% 6% 1 4 4 3 3 3 4 6% 50%	2089
	11th to 20th	Night	13% 6% 3 5% 3 3 3 4 4 7% 48%	1975
	21st to end	Night	16% 7% 2 6% 4 4 3 3 4 5% 44%	1989
May	1st to 10th	Night	14% 9% 3 6% 4 4 4 3 4 6% 44%	4053
	11th to 20th	Night	12% 6% 2 6% 5% 4 5% 4 6% 8% 43%	4053
	21st to end	Night	17% 8% 3 6% 4 4 4 3 6% 6% 41%	4443
June	1st to 10th	Night	7% 4 1 4 4 3 4 4 6% 9% 54%	1800
	11th to 20th	Night	5% 4 1 4 4 4 3 3 7% 11% 55%	1800
	21st to end	Night	2 2 1 4 3 3 4 4 6% 6% 64%	1800
July	1st to 10th	Night	7% 4 2 6% 4 4 4 4 7% 10% 47%	4078
	11th to 20th	Night	3 3 1 4 3 3 4 4 5% 8% 61%	4077
	21st to end	Night	4 3 1 4 3 4 4 4 6% 10% 57%	4449
August	1st to 10th	Night	2 2 1 3 3 4 5% 4 7% 10% 60%	2926
	11th to 20th	Night	8% 4 2 5% 4 4 4 4 5% 8% 52%	2935
	21st to end	Night	3 3 1 3 2 3 4 4 5% 9% 62%	3586
September	1st to 10th	Night	8% 4 2 5% 3 3 4 3 5% 8% 56%	2000
	11th to 20th	Night	8% 5% 2 5% 4 4 4 3 6% 8% 52%	2162
	21st to end	Night	8% 5% 2 5% 3 4 3 2 5% 6% 57%	2208
October	1st to 10th	Night	6% 3 1 4 3 3 3 3 5% 7% 62%	2400
	11th to 20th	Night	11% 4 2 4 3 3 4 3 4 5% 58%	2400
	21st to end	Night	17% 7% 2 5% 3 3 3 2 4 4 51%	2640
November	1st to 10th	Night	12% 4 2 4 3 3 3 2 3 5% 60%	2460
	11th to 20th	Night	10% 7% 2 4 3 3 3 2 5% 5% 57%	2578
	21st to end	Night	15% 8% 2 5% 3 2 3 3 4 5% 51%	2843
December	1st to 10th	Night	10% 9% 3 5% 3 3 3 2 4 6% 52%	4720
	11th to 20th	Night	17% 8% 3 6% 3 3 3 2 3 3 50%	5132
	21st to end	Night	19% 14% 6% 7% 4 4 3 2 3 4 35%	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	43% 3 6% 26% 19% 2	5290
	11th to 20th	Day	34% 3 8% 28% 23% 5%	5310
	21st to end	Day	41% 2 6% 22% 22% 6%	5812
February	1st to 10th	Day	48% 3 9% 23% 13% 3	1890
	11th to 20th	Day	44% 3 10% 23% 17% 3	1854
	21st to end	Day	43% 3 6% 20% 19% 8%	1882
March	1st to 10th	Day	39% 3 6% 21% 16% 15%	4958
	11th to 20th	Day	32% 4 8% 19% 24% 13%	4980
	21st to end	Day	46% 5% 9% 29% 10% 1	5464
April	1st to 10th	Day	40% 4 11% 23% 18% 4	2310
	11th to 20th	Day	45% 4 10% 20% 18% 3	2374
	21st to end	Day	49% 5% 9% 22% 14% 1	2408
May	1st to 10th	Day	47% 7% 9% 21% 15% 1	5900
	11th to 20th	Day	42% 8% 10% 23% 16% 2	5866
	21st to end	Day	46% 7% 12% 19% 16% 1	6447
June	1st to 10th	Day	33% 7% 17% 27% 15% 1	2600
	11th to 20th	Day	33% 7% 13% 28% 16% 2	2600
	21st to end	Day	24% 7% 16% 31% 19% 4	2600
July	1st to 10th	Day	34% 7% 16% 27% 14% 2	5836
	11th to 20th	Day	30% 6% 15% 33% 15% 1	5831
	21st to end	Day	26% 7% 19% 35% 12%	6240
August	1st to 10th	Day	24% 5% 15% 30% 21% 5%	4220
	11th to 20th	Day	35% 6% 16% 28% 15% 1	4159
	21st to end	Day	28% 5% 13% 37% 14% 3	4311
September	1st to 10th	Day	32% 4 10% 28% 17% 9%	2400
	11th to 20th	Day	36% 6% 11% 22% 23% 3	2234
	21st to end	Day	30% 4 9% 27% 27% 4	2170
October	1st to 10th	Day	18% 3 6% 17% 39% 17%	3260
	11th to 20th	Day	19% 2 5% 21% 38% 15%	3240
	21st to end	Day	30% 2 8% 31% 24% 5%	3538
November	1st to 10th	Day	31% 3 7% 28% 24% 7%	2058
	11th to 20th	Day	36% 3 7% 24% 21% 10%	2037
	21st to end	Day	40% 3 7% 23% 24% 3	1769
December	1st to 10th	Day	37% 2 7% 29% 23% 1	2690
	11th to 20th	Day	40% 2 5% 27% 23% 3	3269
	21st to end	Day	56% 4 6% 20% 12% 2	4587
January	1st to 10th	Night	42% 3 9% 27% 15% 3	7635
	11th to 20th	Night	30% 3 8% 21% 33% 5%	7680
	21st to end	Night	46% 2 8% 18% 23% 4	8402
February	1st to 10th	Night	43% 2 10% 25% 15% 4	2730
	11th to 20th	Night	43% 3 8% 25% 18% 4	2664
	21st to end	Night	40% 3 7% 19% 23% 8%	1938
March	1st to 10th	Night	43% 3 6% 18% 20% 10%	4941
	11th to 20th	Night	32% 4 7% 24% 22% 11%	4980
	21st to end	Night	39% 5% 11% 28% 15% 2	5467
April	1st to 10th	Night	36% 3 10% 25% 20% 6%	2089
	11th to 20th	Night	36% 4 9% 24% 22% 5%	1975
	21st to end	Night	42% 5% 10% 24% 17% 2	1989
May	1st to 10th	Night	40% 6% 11% 25% 14% 3	4080
	11th to 20th	Night	37% 7% 14% 24% 13% 4	4054
	21st to end	Night	42% 6% 13% 23% 13% 2	4452
June	1st to 10th	Night	26% 6% 15% 32% 18% 4	1800
	11th to 20th	Night	24% 6% 14% 32% 21% 3	1800
	21st to end	Night	19% 6% 15% 33% 22% 6%	1800
July	1st to 10th	Night	30% 7% 17% 27% 15% 3	4035
	11th to 20th	Night	20% 6% 15% 39% 19% 1	4026
	21st to end	Night	22% 6% 17% 37% 17% 1	4320
August	1st to 10th	Night	18% 7% 15% 35% 24% 1	2916
	11th to 20th	Night	30% 5% 18% 27% 17% 2	2962
	21st to end	Night	19% 5% 12% 38% 22% 4	3586
September	1st to 10th	Night	27% 5% 9% 29% 20% 9%	2000
	11th to 20th	Night	31% 4 10% 25% 25% 5%	2162
	21st to end	Night	29% 3 8% 24% 31% 5%	2208
October	1st to 10th	Night	13% 3 6% 16% 39% 23%	3920
	11th to 20th	Night	21% 2 4 19% 33% 20%	3899
	21st to end	Night	30% 3 6% 30% 24% 7%	4252
November	1st to 10th	Night	29% 3 8% 25% 27% 8%	2460
	11th to 20th	Night	31% 2 7% 26% 26% 9%	2578
	21st to end	Night	37% 3 7% 22% 25% 5%	2843
December	1st to 10th	Night	36% 3 8% 35% 17% 2	4720
	11th to 20th	Night	42% 2 5% 23% 24% 5%	5133
	21st to end	Night	54% 4 7% 21% 11% 3	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	25% 17% 39% 16% 3	330
	11th to 20th	Day	22% 24% 40% 13% 1	330
	21st to end	Day	21% 22% 42% 12% 4	363
February	1st to 10th	Day	27% 24% 36% 12% 2	330
	11th to 20th	Day	26% 26% 35% 12% 1	330
	21st to end	Day	29% 23% 36% 10% 2	273
March	1st to 10th	Day	25% 22% 32% 17% 3	306
	11th to 20th	Day	26% 22% 38% 12% 2	300
	21st to end	Day	27% 24% 38% 8% 2 1	330
April	1st to 10th	Day	25% 22% 34% 14% 5% 1	410
	11th to 20th	Day	24% 18% 38% 16% 4 1	492
	21st to end	Day	26% 16% 33% 18% 7%	508
May	1st to 10th	Day	20% 13% 38% 23% 5% 1	703
	11th to 20th	Day	18% 9% 33% 26% 12% 2	725
	21st to end	Day	15% 9% 33% 24% 14% 5%	789
June	1st to 10th	Day	10% 4 22% 35% 24% 6%	730
	11th to 20th	Day	10% 3 22% 37% 21% 7%	730
	21st to end	Day	4 2 28% 38% 23% 5%	730
July	1st to 10th	Day	9% 3 17% 29% 32% 10%	721
	11th to 20th	Day	6% 1 15% 37% 32% 9%	718
	21st to end	Day	7% 1 12% 33% 31% 15%	794
August	1st to 10th	Day	10% 1 13% 43% 27% 6%	726
	11th to 20th	Day	11% 1 11% 35% 34% 8%	690
	21st to end	Day	9% 2 11% 34% 32% 13%	583
September	1st to 10th	Day	12% 2 11% 36% 31% 8%	530
	11th to 20th	Day	10% 16% 42% 23% 8%	364
	21st to end	Day	10% 4 27% 31% 21% 6%	330
October	1st to 10th	Day	8% 8% 31% 32% 17% 4	330
	11th to 20th	Day	15% 11% 39% 26% 8% 2	330
	21st to end	Day	28% 14% 34% 19% 4	363
November	1st to 10th	Day	18% 13% 42% 19% 7% 2	330
	11th to 20th	Day	19% 15% 39% 18% 6% 2	330
	21st to end	Day	26% 18% 32% 18% 5%	330
December	1st to 10th	Day	21% 18% 41% 13% 6% 1	330
	11th to 20th	Day	23% 20% 38% 15% 4 1	330
	21st to end	Day	24% 21% 40% 12% 3	363
January	1st to 10th	Night	20% 18% 35% 22% 4	1050
	11th to 20th	Night	19% 21% 37% 19% 4	1050
	21st to end	Night	19% 18% 36% 23% 3	1155
February	1st to 10th	Night	22% 17% 37% 22% 3	1050
	11th to 20th	Night	21% 19% 40% 18% 2	1029
	21st to end	Night	23% 17% 37% 21% 2	554
March	1st to 10th	Night	21% 14% 37% 24% 4	606
	11th to 20th	Night	21% 15% 35% 24% 4	600
	21st to end	Night	21% 15% 40% 19% 5%	660
April	1st to 10th	Night	18% 16% 38% 24% 5%	600
	11th to 20th	Night	17% 13% 36% 26% 8%	593
	21st to end	Night	21% 10% 38% 21% 9%	600
May	1st to 10th	Night	16% 6% 37% 34% 8%	600
	11th to 20th	Night	16% 5% 30% 32% 15% 1	591
	21st to end	Night	12% 5% 32% 31% 17% 2	650
June	1st to 10th	Night	9% 2 19% 39% 31% 1	600
	11th to 20th	Night	6% 2 27% 40% 23% 2	600
	21st to end	Night	2 1 22% 47% 26% 3	600
July	1st to 10th	Night	6% 1 13% 38% 39% 3	585
	11th to 20th	Night	6% 1 10% 44% 34% 5%	582
	21st to end	Night	5% 1 9% 42% 37% 6%	657
August	1st to 10th	Night	5% 1 11% 46% 34% 4	597
	11th to 20th	Night	8% 1 13% 41% 32% 5%	594
	21st to end	Night	4 1 12% 40% 37% 5%	660
September	1st to 10th	Night	10% 1 13% 40% 33% 3	600
	11th to 20th	Night	10% 1 13% 41% 30% 5%	600
	21st to end	Night	9% 3 22% 37% 25% 4	608
October	1st to 10th	Night	7% 3 26% 38% 23% 4	800
	11th to 20th	Night	14% 8% 34% 33% 11%	800
	21st to end	Night	23% 11% 31% 26% 9% 1	880
November	1st to 10th	Night	14% 10% 38% 27% 10%	820
	11th to 20th	Night	15% 13% 36% 29% 7%	898
	21st to end	Night	21% 14% 35% 22% 8%	1050
December	1st to 10th	Night	19% 13% 38% 24% 5%	1050
	11th to 20th	Night	24% 14% 33% 24% 4	1050
	21st to end	Night	22% 18% 36% 21% 4	1155

Page generated at 2026-02-28 00:40:20. Version ac07

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