Fort Smith
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Smith clear sky chart from 2005-11-06 to 2026-07-31.

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% 47%	138379
	Night	13% 5% 2 5% 3 3 3 3 5% 6% 50%	134970
Transparency	Day	36% 5% 10% 25% 20% 5%	141991
	Night	34% 4 10% 24% 22% 7%	139438
Seeing	Day	13% 7% 21% 27% 24% 8%	17772
	Night	14% 5% 23% 37% 19% 2	27532

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% 8% 3 6% 4 4 4 3 4 5% 47%	5289
	11th to 20th	Day	7% 6% 2 5% 4 4 3 3 4 4 59%	5310
	21st to end	Day	20% 7% 2 5% 3 3 3 2 4 5% 47%	5812
February	1st to 10th	Day	22% 9% 2 4 4 2 3 2 3 4 44%	1890
	11th to 20th	Day	18% 7% 2 6% 3 3 4 3 4 6% 43%	1886
	21st to end	Day	18% 6% 2 5% 4 3 4 3 5% 5% 43%	1888
March	1st to 10th	Day	19% 7% 3 5% 3 3 3 3 4 5% 46%	5046
	11th to 20th	Day	10% 4 2 5% 4 4 3 3 5% 6% 54%	5090
	21st to end	Day	16% 7% 3 6% 4 4 4 3 5% 7% 42%	5583
April	1st to 10th	Day	16% 5% 3 5% 4 4 5% 3 4 6% 45%	2404
	11th to 20th	Day	17% 7% 2 6% 4 4 3 3 4 5% 44%	2494
	21st to end	Day	19% 8% 3 7% 4 5% 4 3 4 5% 38%	2520
May	1st to 10th	Day	17% 8% 3 7% 4 4 4 3 5% 5% 40%	7589
	11th to 20th	Day	12% 6% 3 8% 5% 5% 5% 4 6% 8% 39%	7627
	21st to end	Day	18% 8% 3 7% 5% 5% 5% 4 5% 7% 32%	8392
June	1st to 10th	Day	9% 5% 2 7% 5% 4 5% 4 7% 9% 43%	2730
	11th to 20th	Day	7% 4 2 6% 5% 5% 6% 4 7% 9% 45%	2730
	21st to end	Day	5% 3 2 4 4 4 6% 4 7% 9% 53%	2730
July	1st to 10th	Day	7% 4 2 6% 5% 5% 6% 5% 8% 12% 40%	6030
	11th to 20th	Day	5% 3 2 5% 4 4 4 4 6% 9% 55%	6030
	21st to end	Day	5% 3 2 6% 5% 5% 5% 5% 8% 10% 48%	6553
August	1st to 10th	Day	3 3 1 4 3 4 4 4 6% 8% 59%	4234
	11th to 20th	Day	9% 4 2 5% 4 4 5% 4 6% 9% 48%	4110
	21st to end	Day	5% 3 1 5% 4 4 5% 4 6% 8% 55%	4312
September	1st to 10th	Day	10% 4 1 5% 3 4 4 3 5% 6% 54%	2400
	11th to 20th	Day	11% 4 1 5% 4 4 4 3 6% 9% 49%	2201
	21st to end	Day	7% 3 2 5% 3 4 5% 3 5% 7% 55%	2185
October	1st to 10th	Day	8% 4 2 5% 3 4 3 3 4 6% 59%	2000
	11th to 20th	Day	13% 3 2 4 3 3 2 2 4 5% 60%	2000
	21st to end	Day	19% 6% 2 5% 3 3 3 2 4 5% 50%	2200
November	1st to 10th	Day	12% 5% 2 4 3 2 3 3 4 6% 56%	2058
	11th to 20th	Day	12% 4 2 4 3 2 3 2 4 6% 57%	2068
	21st to end	Day	18% 6% 2 4 3 2 3 2 4 6% 49%	1890
December	1st to 10th	Day	17% 7% 2 5% 3 2 3 3 4 5% 50%	3030
	11th to 20th	Day	18% 7% 2 6% 4 4 3 2 5% 5% 44%	3481
	21st to end	Day	23% 11% 3 7% 4 3 3 3 4 5% 35%	4587
January	1st to 10th	Night	13% 7% 2 7% 3 3 3 3 4 6% 47%	7634
	11th to 20th	Night	7% 5% 1 3 3 2 3 2 4 6% 64%	7680
	21st to end	Night	22% 7% 2 5% 3 2 3 3 4 5% 43%	8402
February	1st to 10th	Night	18% 8% 2 6% 3 3 3 3 4 6% 44%	2730
	11th to 20th	Night	18% 7% 2 5% 2 2 3 3 5% 6% 47%	2637
	21st to end	Night	17% 5% 2 5% 3 4 3 3 3 6% 50%	1916
March	1st to 10th	Night	21% 7% 2 6% 3 3 3 3 3 4 46%	5029
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 5% 6% 53%	5090
	21st to end	Night	15% 6% 2 5% 3 3 4 3 5% 7% 46%	5588
April	1st to 10th	Night	16% 5% 1 4 4 3 3 3 5% 7% 49%	2215
	11th to 20th	Night	16% 5% 2 4 4 3 4 3 5% 7% 48%	2075
	21st to end	Night	15% 5% 3 6% 4 4 3 3 4 6% 46%	2100
May	1st to 10th	Night	15% 7% 3 6% 4 4 4 3 5% 7% 43%	5289
	11th to 20th	Night	14% 6% 2 7% 4 4 4 4 6% 8% 41%	5265
	21st to end	Night	18% 7% 3 7% 4 4 4 4 6% 8% 35%	5793
June	1st to 10th	Night	6% 4 2 5% 4 4 3 4 5% 10% 53%	1890
	11th to 20th	Night	5% 4 1 5% 4 4 4 3 5% 10% 55%	1890
	21st to end	Night	4 2 1 3 3 3 3 3 6% 8% 63%	1890
July	1st to 10th	Night	6% 4 2 6% 5% 5% 5% 4 8% 10% 44%	4168
	11th to 20th	Night	5% 3 1 4 3 3 4 4 6% 8% 58%	4167
	21st to end	Night	4 4 2 5% 4 4 5% 4 6% 9% 54%	4539
August	1st to 10th	Night	5% 3 1 4 3 4 4 4 6% 8% 58%	2926
	11th to 20th	Night	6% 3 1 4 3 4 4 4 6% 9% 56%	2946
	21st to end	Night	4 3 1 4 3 4 4 4 6% 8% 59%	3586
September	1st to 10th	Night	7% 4 2 4 3 3 4 3 5% 7% 58%	2000
	11th to 20th	Night	10% 4 2 6% 4 3 4 4 6% 6% 52%	2194
	21st to end	Night	8% 4 1 4 4 3 4 3 4 6% 58%	2200
October	1st to 10th	Night	7% 2 1 4 4 3 3 3 5% 7% 62%	2393
	11th to 20th	Night	12% 3 2 3 3 3 3 3 4 4 60%	2400
	21st to end	Night	19% 5% 2 4 3 2 3 2 3 4 53%	2640
November	1st to 10th	Night	12% 4 2 4 3 3 3 3 3 5% 58%	2460
	11th to 20th	Night	10% 5% 2 4 2 3 2 3 5% 6% 58%	2549
	21st to end	Night	19% 5% 2 4 3 3 3 2 3 6% 51%	2730
December	1st to 10th	Night	14% 7% 2 5% 3 3 3 3 4 5% 51%	4380
	11th to 20th	Night	19% 6% 2 5% 3 3 3 2 3 4 49%	4946
	21st to end	Night	23% 9% 3 6% 3 3 3 2 4 4 38%	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	41% 3 8% 26% 20% 2	5290
	11th to 20th	Day	30% 3 8% 25% 29% 6%	5310
	21st to end	Day	42% 3 4 23% 23% 6%	5812
February	1st to 10th	Day	45% 4 9% 21% 18% 3	1890
	11th to 20th	Day	43% 4 8% 21% 20% 4	1895
	21st to end	Day	43% 4 6% 19% 21% 7%	1888
March	1st to 10th	Day	41% 4 5% 19% 16% 15%	5046
	11th to 20th	Day	31% 5% 8% 19% 23% 15%	5090
	21st to end	Day	42% 4 9% 30% 14% 1	5585
April	1st to 10th	Day	40% 5% 10% 20% 20% 6%	2404
	11th to 20th	Day	42% 5% 9% 21% 18% 6%	2494
	21st to end	Day	48% 5% 7% 20% 17% 2	2520
May	1st to 10th	Day	45% 5% 8% 21% 19% 2	7627
	11th to 20th	Day	42% 6% 10% 21% 18% 2	7631
	21st to end	Day	50% 6% 12% 16% 14% 1	8405
June	1st to 10th	Day	35% 8% 14% 25% 17% 2	2730
	11th to 20th	Day	35% 7% 14% 24% 19% 2	2730
	21st to end	Day	26% 8% 15% 29% 19% 4	2730
July	1st to 10th	Day	34% 7% 18% 30% 9% 2	5966
	11th to 20th	Day	25% 6% 14% 36% 18% 1	5961
	21st to end	Day	30% 7% 14% 33% 15% 1	6371
August	1st to 10th	Day	22% 6% 12% 30% 23% 6%	4220
	11th to 20th	Day	32% 6% 15% 30% 15% 1	4149
	21st to end	Day	26% 7% 14% 36% 14% 3	4311
September	1st to 10th	Day	30% 6% 10% 26% 19% 9%	2400
	11th to 20th	Day	33% 6% 10% 24% 21% 5%	2201
	21st to end	Day	28% 5% 12% 19% 28% 8%	2185
October	1st to 10th	Day	16% 3 6% 12% 39% 23%	3260
	11th to 20th	Day	19% 3 4 18% 40% 17%	3240
	21st to end	Day	31% 4 7% 28% 24% 6%	3538
November	1st to 10th	Day	29% 4 9% 26% 25% 7%	2058
	11th to 20th	Day	30% 3 6% 27% 24% 9%	2068
	21st to end	Day	37% 3 8% 22% 26% 5%	1890
December	1st to 10th	Day	38% 3 7% 30% 20% 2	3030
	11th to 20th	Day	43% 3 6% 23% 23% 3	3479
	21st to end	Day	52% 3 8% 21% 13% 3	4587
January	1st to 10th	Night	39% 3 10% 29% 18% 2	7635
	11th to 20th	Night	23% 4 8% 20% 38% 8%	7680
	21st to end	Night	44% 4 6% 16% 24% 6%	8402
February	1st to 10th	Night	42% 4 7% 25% 18% 5%	2730
	11th to 20th	Night	39% 4 8% 24% 20% 6%	2638
	21st to end	Night	38% 3 7% 19% 23% 10%	1916
March	1st to 10th	Night	42% 4 6% 16% 19% 12%	5029
	11th to 20th	Night	32% 4 6% 23% 20% 15%	5090
	21st to end	Night	38% 4 11% 26% 18% 3	5588
April	1st to 10th	Night	35% 5% 10% 20% 21% 9%	2215
	11th to 20th	Night	36% 5% 7% 22% 20% 10%	2075
	21st to end	Night	39% 5% 8% 23% 22% 2	2100
May	1st to 10th	Night	40% 6% 13% 20% 17% 4	5316
	11th to 20th	Night	40% 6% 11% 22% 18% 3	5266
	21st to end	Night	47% 7% 15% 17% 10% 3	5805
June	1st to 10th	Night	25% 7% 15% 30% 19% 3	1890
	11th to 20th	Night	25% 5% 13% 31% 23% 3	1890
	21st to end	Night	19% 4 14% 31% 26% 6%	1890
July	1st to 10th	Night	32% 7% 16% 28% 14% 2	4125
	11th to 20th	Night	22% 5% 13% 36% 22% 1	4116
	21st to end	Night	26% 6% 16% 33% 18% 2	4410
August	1st to 10th	Night	22% 6% 13% 31% 23% 4	2916
	11th to 20th	Night	25% 5% 20% 31% 16% 2	2973
	21st to end	Night	23% 6% 12% 32% 25% 3	3586
September	1st to 10th	Night	26% 6% 10% 25% 23% 10%	2000
	11th to 20th	Night	31% 6% 11% 22% 23% 6%	2194
	21st to end	Night	27% 5% 9% 23% 29% 8%	2200
October	1st to 10th	Night	14% 4 7% 13% 34% 28%	3913
	11th to 20th	Night	18% 3 4 15% 38% 21%	3899
	21st to end	Night	29% 3 5% 26% 28% 10%	4252
November	1st to 10th	Night	30% 4 7% 22% 27% 10%	2460
	11th to 20th	Night	28% 3 7% 26% 26% 10%	2549
	21st to end	Night	36% 3 8% 20% 26% 6%	2730
December	1st to 10th	Night	37% 4 7% 30% 19% 3	4380
	11th to 20th	Night	41% 3 5% 22% 21% 8%	4947
	21st to end	Night	48% 3 9% 21% 14% 4	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	21% 13% 33% 25% 8% 1	330
	11th to 20th	Day	19% 14% 39% 21% 7%	330
	21st to end	Day	20% 14% 37% 21% 8% 1	363
February	1st to 10th	Day	29% 9% 34% 20% 7%	330
	11th to 20th	Day	28% 12% 35% 19% 6%	330
	21st to end	Day	27% 15% 34% 16% 7%	273
March	1st to 10th	Day	22% 13% 33% 24% 7% 1	330
	11th to 20th	Day	25% 16% 35% 17% 7%	330
	21st to end	Day	21% 16% 35% 20% 8%	363
April	1st to 10th	Day	21% 13% 31% 23% 9% 2	424
	11th to 20th	Day	20% 13% 31% 27% 8% 1	532
	21st to end	Day	20% 12% 28% 29% 9% 1	540
May	1st to 10th	Day	15% 10% 27% 35% 12% 1	738
	11th to 20th	Day	13% 7% 25% 30% 22% 3	775
	21st to end	Day	12% 5% 23% 34% 20% 6%	844
June	1st to 10th	Day	9% 4 14% 30% 32% 11%	780
	11th to 20th	Day	7% 1 14% 34% 34% 11%	780
	21st to end	Day	5% 1 13% 34% 34% 13%	780
July	1st to 10th	Day	6% 2 9% 24% 42% 17%	771
	11th to 20th	Day	4 2 6% 29% 39% 21%	768
	21st to end	Day	4 1 5% 26% 42% 21%	845
August	1st to 10th	Day	6% 2 7% 28% 44% 13%	726
	11th to 20th	Day	10% 1 8% 28% 38% 15%	680
	21st to end	Day	8% 1 6% 18% 44% 22%	583
September	1st to 10th	Day	9% 1 6% 24% 45% 15%	530
	11th to 20th	Day	5% 2 9% 27% 38% 18%	331
	21st to end	Day	11% 5% 12% 27% 28% 17%	330
October	1st to 10th	Day	5% 2 22% 33% 30% 8%	330
	11th to 20th	Day	10% 11% 24% 31% 21% 3	330
	21st to end	Day	24% 15% 21% 25% 12% 2	363
November	1st to 10th	Day	16% 6% 31% 25% 21% 2	330
	11th to 20th	Day	13% 10% 32% 30% 14% 2	330
	21st to end	Day	20% 11% 25% 27% 15% 1	330
December	1st to 10th	Day	17% 12% 37% 21% 11% 2	330
	11th to 20th	Day	21% 13% 30% 25% 10%	330
	21st to end	Day	21% 15% 31% 25% 6% 1	363
January	1st to 10th	Night	18% 7% 34% 36% 6%	1050
	11th to 20th	Night	17% 8% 35% 34% 6%	1050
	21st to end	Night	19% 5% 35% 37% 4	1155
February	1st to 10th	Night	22% 8% 31% 35% 5%	1050
	11th to 20th	Night	21% 7% 36% 32% 4	1003
	21st to end	Night	21% 8% 36% 33% 2	532
March	1st to 10th	Night	19% 7% 31% 38% 4	630
	11th to 20th	Night	21% 7% 29% 36% 7%	630
	21st to end	Night	19% 9% 30% 34% 7%	693
April	1st to 10th	Night	17% 7% 32% 36% 9%	630
	11th to 20th	Night	14% 10% 30% 37% 8%	623
	21st to end	Night	17% 6% 31% 35% 11%	630
May	1st to 10th	Night	13% 3 26% 46% 12%	630
	11th to 20th	Night	15% 5% 19% 44% 17% 1	621
	21st to end	Night	11% 4 17% 41% 26% 2	683
June	1st to 10th	Night	6% 3 8% 40% 41% 2	630
	11th to 20th	Night	7% 1 9% 47% 34% 3	630
	21st to end	Night	4 1 7% 40% 43% 5%	630
July	1st to 10th	Night	6% 1 5% 33% 50% 6%	615
	11th to 20th	Night	4 1 5% 33% 49% 8%	612
	21st to end	Night	4 1 4 31% 51% 9%	687
August	1st to 10th	Night	3 2 6% 36% 48% 5%	597
	11th to 20th	Night	7% 2 8% 35% 42% 5%	594
	21st to end	Night	5% 1 5% 34% 48% 6%	660
September	1st to 10th	Night	9% 2 6% 35% 46% 3	600
	11th to 20th	Night	12% 1 7% 38% 38% 4	600
	21st to end	Night	10% 1 11% 38% 35% 4	600
October	1st to 10th	Night	6% 2 13% 43% 32% 3	793
	11th to 20th	Night	13% 4 23% 42% 18%	800
	21st to end	Night	21% 6% 22% 35% 15% 1	880
November	1st to 10th	Night	13% 5% 24% 43% 15% 1	820
	11th to 20th	Night	12% 6% 29% 40% 12% 1	869
	21st to end	Night	20% 7% 27% 34% 11%	1050
December	1st to 10th	Night	19% 6% 28% 40% 7%	1050
	11th to 20th	Night	21% 7% 26% 40% 5%	1050
	21st to end	Night	19% 8% 32% 34% 6%	1155

Page generated at 2026-07-28 02:25:26. Version ac07

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