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 2025-03-27.

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%	109656
	Night	14% 5% 2 5% 3 3 3 3 5% 6% 50%	109900
Transparency	Day	36% 5% 10% 24% 20% 5%	113307
	Night	33% 5% 10% 24% 22% 7%	114389
Seeing	Day	13% 7% 20% 27% 25% 8%	15825
	Night	14% 5% 23% 37% 19% 2	25825

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% 8% 3 6% 4 4 3 3 3 4 46%	4077
	11th to 20th	Day	8% 6% 2 6% 4 4 4 3 4 5% 55%	4080
	21st to end	Day	22% 6% 2 4 3 2 3 2 4 5% 46%	4488
February	1st to 10th	Day	22% 9% 3 5% 4 3 3 2 3 4 43%	1800
	11th to 20th	Day	19% 7% 2 6% 4 3 3 3 4 6% 43%	1794
	21st to end	Day	19% 7% 2 5% 4 3 4 3 5% 5% 42%	1800
March	1st to 10th	Day	18% 7% 3 5% 3 3 3 2 4 5% 47%	3546
	11th to 20th	Day	13% 5% 2 6% 4 4 3 3 5% 6% 48%	3590
	21st to end	Day	18% 8% 3 7% 4 4 4 3 4 6% 40%	3880
April	1st to 10th	Day	14% 5% 3 5% 4 4 5% 3 4 6% 46%	2175
	11th to 20th	Day	17% 7% 3 6% 4 4 3 3 5% 5% 44%	2254
	21st to end	Day	19% 8% 3 6% 4 5% 4 3 4 5% 40%	2280
May	1st to 10th	Day	21% 8% 2 6% 4 4 4 4 5% 5% 37%	4068
	11th to 20th	Day	12% 6% 3 8% 4 4 4 4 6% 8% 42%	4082
	21st to end	Day	17% 6% 2 7% 5% 5% 5% 4 5% 7% 37%	4477
June	1st to 10th	Day	9% 5% 2 7% 5% 4 5% 4 7% 10% 43%	2470
	11th to 20th	Day	6% 4 2 6% 5% 5% 6% 4 7% 9% 47%	2470
	21st to end	Day	5% 3 2 3 4 4 6% 4 7% 9% 53%	2470
July	1st to 10th	Day	9% 4 2 6% 5% 4 5% 4 7% 10% 45%	4120
	11th to 20th	Day	4 3 2 5% 4 4 4 4 6% 9% 56%	4120
	21st to end	Day	7% 4 2 7% 5% 5% 6% 5% 8% 10% 40%	4465
August	1st to 10th	Day	3 3 1 5% 3 4 4 4 6% 8% 59%	4104
	11th to 20th	Day	10% 4 2 5% 4 4 5% 4 6% 9% 48%	3982
	21st to end	Day	4 3 1 5% 4 4 5% 4 6% 8% 56%	4180
September	1st to 10th	Day	11% 4 1 5% 3 4 4 3 5% 6% 54%	2280
	11th to 20th	Day	12% 4 1 5% 4 4 4 3 6% 8% 49%	2091
	21st to end	Day	7% 3 2 5% 3 4 5% 3 5% 7% 56%	2076
October	1st to 10th	Day	8% 4 2 5% 3 3 3 3 4 6% 58%	1900
	11th to 20th	Day	13% 3 1 4 3 3 2 2 3 5% 60%	1900
	21st to end	Day	18% 6% 2 5% 3 3 3 2 4 5% 50%	2090
November	1st to 10th	Day	13% 5% 2 4 3 2 3 3 5% 6% 55%	1958
	11th to 20th	Day	12% 4 2 4 3 2 2 2 4 6% 57%	1970
	21st to end	Day	18% 6% 2 4 3 3 3 2 4 6% 50%	1800
December	1st to 10th	Day	17% 6% 2 5% 3 2 3 3 4 5% 50%	2940
	11th to 20th	Day	19% 7% 2 6% 4 4 3 2 5% 5% 44%	3391
	21st to end	Day	23% 11% 3 7% 4 3 3 3 4 5% 35%	4488
January	1st to 10th	Night	15% 7% 2 7% 4 4 3 3 4 5% 45%	5888
	11th to 20th	Night	9% 6% 2 4 3 2 3 3 4 6% 58%	5900
	21st to end	Night	22% 7% 2 4 3 2 2 3 3 5% 46%	6490
February	1st to 10th	Night	19% 8% 2 6% 3 3 3 3 4 6% 44%	2600
	11th to 20th	Night	18% 7% 2 5% 2 3 2 3 5% 6% 46%	2508
	21st to end	Night	17% 6% 2 5% 3 4 3 3 3 6% 48%	1828
March	1st to 10th	Night	21% 6% 2 6% 3 3 3 3 3 5% 45%	3529
	11th to 20th	Night	16% 6% 2 4 3 3 3 3 4 6% 50%	3590
	21st to end	Night	17% 6% 2 5% 4 4 4 3 5% 5% 45%	3889
April	1st to 10th	Night	15% 5% 1 4 4 3 3 3 5% 7% 49%	2005
	11th to 20th	Night	15% 5% 2 4 4 3 3 3 5% 7% 49%	1875
	21st to end	Night	15% 5% 3 6% 4 4 3 4 5% 6% 46%	1900
May	1st to 10th	Night	16% 7% 3 6% 4 4 4 3 5% 7% 43%	2833
	11th to 20th	Night	14% 6% 2 6% 4 4 4 4 6% 8% 42%	2823
	21st to end	Night	16% 6% 2 5% 4 4 4 4 6% 8% 42%	3090
June	1st to 10th	Night	5% 4 1 4 4 4 4 4 5% 11% 55%	1710
	11th to 20th	Night	4 3 1 4 4 4 4 3 5% 10% 58%	1710
	21st to end	Night	4 2 1 3 3 3 3 3 6% 8% 63%	1710
July	1st to 10th	Night	8% 5% 2 5% 4 5% 4 4 6% 8% 49%	2850
	11th to 20th	Night	4 2 1 4 3 3 4 4 6% 8% 61%	2850
	21st to end	Night	5% 5% 2 6% 5% 5% 5% 5% 7% 9% 48%	3098
August	1st to 10th	Night	5% 2 1 4 3 4 4 4 6% 8% 58%	2836
	11th to 20th	Night	6% 3 1 4 3 4 4 4 6% 8% 56%	2854
	21st to end	Night	4 3 1 4 3 4 4 4 6% 8% 60%	3476
September	1st to 10th	Night	7% 4 2 4 3 3 3 2 5% 7% 59%	1900
	11th to 20th	Night	10% 4 2 6% 4 3 4 4 6% 6% 52%	2084
	21st to end	Night	7% 4 1 4 4 3 4 3 4 6% 59%	2090
October	1st to 10th	Night	7% 3 1 4 4 3 3 3 4 7% 61%	2273
	11th to 20th	Night	13% 3 2 3 2 3 3 3 4 4 60%	2280
	21st to end	Night	19% 4 2 4 3 2 3 2 3 4 54%	2508
November	1st to 10th	Night	12% 4 2 4 3 3 3 3 3 5% 58%	2340
	11th to 20th	Night	10% 5% 2 4 2 3 2 3 5% 6% 58%	2427
	21st to end	Night	18% 5% 1 4 3 3 3 3 4 6% 52%	2600
December	1st to 10th	Night	15% 7% 2 5% 3 3 3 3 4 5% 51%	4250
	11th to 20th	Night	19% 6% 2 5% 3 3 3 2 4 4 48%	4816
	21st to end	Night	23% 10% 3 6% 4 3 3 2 4 4 38%	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	42% 3 9% 24% 20% 2	4078
	11th to 20th	Day	32% 3 10% 26% 25% 4	4080
	21st to end	Day	42% 3 4 20% 23% 7%	4488
February	1st to 10th	Day	46% 4 9% 20% 18% 3	1800
	11th to 20th	Day	44% 4 8% 22% 19% 4	1803
	21st to end	Day	45% 4 6% 19% 20% 7%	1800
March	1st to 10th	Day	40% 4 7% 19% 19% 11%	3546
	11th to 20th	Day	37% 5% 11% 22% 19% 5%	3590
	21st to end	Day	45% 4 9% 27% 14% 1	3880
April	1st to 10th	Day	39% 5% 10% 20% 20% 6%	2175
	11th to 20th	Day	41% 5% 9% 22% 18% 5%	2254
	21st to end	Day	46% 6% 7% 21% 18% 2	2280
May	1st to 10th	Day	46% 7% 8% 22% 15% 1	4106
	11th to 20th	Day	38% 8% 11% 25% 17% 1	4086
	21st to end	Day	44% 7% 12% 20% 16% 1	4489
June	1st to 10th	Day	35% 9% 14% 25% 16% 2	2470
	11th to 20th	Day	33% 7% 14% 25% 19% 2	2470
	21st to end	Day	25% 8% 14% 29% 20% 4	2470
July	1st to 10th	Day	33% 7% 17% 29% 13% 2	4056
	11th to 20th	Day	23% 6% 11% 35% 22% 2	4051
	21st to end	Day	36% 8% 16% 27% 13% 1	4325
August	1st to 10th	Day	23% 6% 12% 29% 24% 6%	4090
	11th to 20th	Day	33% 6% 15% 30% 15% 1	4021
	21st to end	Day	25% 8% 15% 36% 15% 2	4179
September	1st to 10th	Day	30% 6% 10% 25% 19% 10%	2280
	11th to 20th	Day	33% 6% 10% 23% 22% 5%	2091
	21st to end	Day	27% 5% 13% 19% 28% 8%	2076
October	1st to 10th	Day	16% 3 6% 12% 39% 23%	3160
	11th to 20th	Day	19% 3 4 18% 40% 17%	3140
	21st to end	Day	31% 4 7% 28% 25% 6%	3428
November	1st to 10th	Day	30% 4 10% 25% 25% 7%	1958
	11th to 20th	Day	30% 3 6% 26% 25% 10%	1970
	21st to end	Day	37% 3 7% 21% 27% 5%	1800
December	1st to 10th	Day	38% 3 7% 30% 20% 2	2940
	11th to 20th	Day	43% 3 6% 22% 23% 3	3389
	21st to end	Day	52% 3 8% 21% 13% 3	4488
January	1st to 10th	Night	41% 3 10% 25% 18% 3	5888
	11th to 20th	Night	27% 4 10% 22% 33% 5%	5900
	21st to end	Night	42% 2 8% 16% 26% 5%	6490
February	1st to 10th	Night	43% 4 8% 24% 17% 5%	2600
	11th to 20th	Night	40% 4 7% 24% 20% 6%	2509
	21st to end	Night	39% 3 7% 19% 23% 9%	1828
March	1st to 10th	Night	42% 5% 8% 17% 18% 11%	3529
	11th to 20th	Night	36% 4 8% 27% 19% 7%	3590
	21st to end	Night	40% 5% 10% 26% 17% 3	3889
April	1st to 10th	Night	35% 5% 9% 20% 22% 9%	2005
	11th to 20th	Night	35% 5% 7% 22% 20% 10%	1875
	21st to end	Night	38% 6% 8% 23% 23% 2	1900
May	1st to 10th	Night	39% 7% 11% 22% 17% 4	2860
	11th to 20th	Night	38% 8% 12% 24% 17% 1	2824
	21st to end	Night	38% 8% 14% 24% 13% 3	3099
June	1st to 10th	Night	23% 8% 15% 32% 19% 4	1710
	11th to 20th	Night	22% 5% 13% 32% 25% 3	1710
	21st to end	Night	19% 5% 13% 31% 27% 6%	1710
July	1st to 10th	Night	31% 7% 16% 25% 18% 4	2805
	11th to 20th	Night	19% 5% 11% 36% 26% 2	2796
	21st to end	Night	30% 7% 18% 29% 15% 1	2999
August	1st to 10th	Night	22% 6% 13% 31% 23% 4	2826
	11th to 20th	Night	26% 5% 19% 31% 17% 2	2881
	21st to end	Night	22% 6% 12% 33% 25% 3	3476
September	1st to 10th	Night	25% 6% 10% 25% 23% 11%	1900
	11th to 20th	Night	31% 6% 11% 21% 25% 6%	2084
	21st to end	Night	26% 4 9% 23% 29% 8%	2090
October	1st to 10th	Night	14% 4 7% 13% 34% 29%	3793
	11th to 20th	Night	18% 3 4 15% 39% 22%	3779
	21st to end	Night	28% 3 5% 27% 28% 10%	4120
November	1st to 10th	Night	31% 4 7% 22% 26% 10%	2340
	11th to 20th	Night	28% 3 7% 24% 27% 11%	2427
	21st to end	Night	35% 4 8% 20% 27% 6%	2600
December	1st to 10th	Night	37% 4 7% 30% 19% 3	4250
	11th to 20th	Night	41% 3 5% 22% 21% 8%	4817
	21st to end	Night	49% 3 9% 20% 14% 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	21% 13% 33% 24% 8% 1	300
	11th to 20th	Day	20% 14% 39% 21% 7%	300
	21st to end	Day	20% 15% 35% 21% 8% 1	330
February	1st to 10th	Day	31% 9% 33% 19% 7%	300
	11th to 20th	Day	28% 13% 35% 18% 6%	300
	21st to end	Day	30% 15% 33% 15% 6%	249
March	1st to 10th	Day	22% 13% 33% 24% 8% 1	300
	11th to 20th	Day	25% 17% 35% 16% 6%	300
	21st to end	Day	22% 17% 35% 18% 7%	315
April	1st to 10th	Day	20% 14% 33% 22% 8% 3	355
	11th to 20th	Day	20% 12% 30% 28% 8% 1	452
	21st to end	Day	20% 13% 28% 29% 9% 2	460
May	1st to 10th	Day	16% 10% 26% 35% 12% 1	639
	11th to 20th	Day	13% 6% 24% 31% 23% 4	675
	21st to end	Day	11% 5% 23% 33% 22% 6%	734
June	1st to 10th	Day	9% 4 12% 29% 35% 12%	680
	11th to 20th	Day	6% 1 12% 33% 35% 12%	680
	21st to end	Day	4 1 13% 33% 35% 13%	680
July	1st to 10th	Day	7% 2 9% 24% 41% 17%	671
	11th to 20th	Day	4 1 7% 28% 39% 21%	668
	21st to end	Day	5% 1 6% 26% 41% 21%	739
August	1st to 10th	Day	6% 2 7% 28% 44% 13%	676
	11th to 20th	Day	11% 1 8% 29% 38% 12%	632
	21st to end	Day	7% 6% 18% 46% 24%	539
September	1st to 10th	Day	9% 1 6% 23% 45% 16%	490
	11th to 20th	Day	6% 2 10% 29% 38% 16%	301
	21st to end	Day	10% 4 12% 28% 28% 17%	300
October	1st to 10th	Day	5% 2 23% 31% 30% 8%	300
	11th to 20th	Day	11% 11% 24% 31% 20% 3	300
	21st to end	Day	22% 16% 22% 25% 13% 2	330
November	1st to 10th	Day	18% 5% 30% 25% 21% 2	300
	11th to 20th	Day	14% 10% 31% 29% 15% 1	300
	21st to end	Day	20% 12% 23% 29% 15% 1	300
December	1st to 10th	Day	17% 12% 37% 20% 11% 3	300
	11th to 20th	Day	22% 14% 31% 24% 10%	300
	21st to end	Day	22% 15% 32% 25% 5% 1	330
January	1st to 10th	Night	18% 7% 33% 36% 6%	1000
	11th to 20th	Night	18% 8% 34% 35% 6%	1000
	21st to end	Night	19% 5% 35% 38% 5%	1100
February	1st to 10th	Night	22% 8% 30% 35% 5%	1000
	11th to 20th	Night	22% 7% 35% 33% 4	954
	21st to end	Night	22% 8% 35% 34% 2	508
March	1st to 10th	Night	20% 8% 30% 38% 4	600
	11th to 20th	Night	21% 7% 28% 36% 8%	600
	21st to end	Night	19% 9% 30% 34% 7%	647
April	1st to 10th	Night	16% 7% 33% 35% 9%	570
	11th to 20th	Night	13% 10% 30% 38% 9%	563
	21st to end	Night	17% 6% 32% 33% 11%	570
May	1st to 10th	Night	13% 4 26% 46% 12%	570
	11th to 20th	Night	14% 4 18% 44% 18% 1	561
	21st to end	Night	10% 3 17% 41% 27% 2	617
June	1st to 10th	Night	5% 3 8% 40% 43% 2	570
	11th to 20th	Night	5% 8% 48% 36% 3	570
	21st to end	Night	3 1 7% 40% 43% 5%	570
July	1st to 10th	Night	6% 1 5% 33% 50% 6%	555
	11th to 20th	Night	3 1 6% 34% 48% 8%	552
	21st to end	Night	4 1 4 31% 52% 8%	624
August	1st to 10th	Night	3 1 6% 36% 49% 5%	567
	11th to 20th	Night	7% 2 8% 37% 41% 5%	564
	21st to end	Night	5% 1 4 35% 49% 6%	627
September	1st to 10th	Night	9% 1 6% 34% 47% 3	570
	11th to 20th	Night	12% 1 7% 38% 38% 3	570
	21st to end	Night	10% 1 12% 38% 34% 4	570
October	1st to 10th	Night	7% 2 14% 42% 33% 3	753
	11th to 20th	Night	13% 4 24% 42% 17%	760
	21st to end	Night	20% 5% 22% 35% 16% 1	836
November	1st to 10th	Night	13% 5% 24% 42% 15% 1	780
	11th to 20th	Night	11% 7% 30% 40% 12% 1	827
	21st to end	Night	20% 7% 27% 35% 12%	1000
December	1st to 10th	Night	19% 7% 28% 40% 7%	1000
	11th to 20th	Night	21% 7% 26% 40% 5%	1000
	21st to end	Night	19% 8% 32% 34% 6%	1100

Page generated at 2025-03-24 08:04:26. Version ac07

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