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 2024-01-12.

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	10% 10% 4 8% 8% 4 6% 6% 6% 7% 31%	74414
	Night	9% 11% 5% 10% 9% 5% 7% 6% 6% 7% 25%	75305
Transparency	Day	51% 8% 14% 20% 7%	74057
	Night	56% 7% 14% 17% 5%	75180
Seeing	Day	15% 9% 28% 29% 15% 4	15713
	Night	14% 8% 30% 31% 15% 3	23965

By Month

Percentage Cloud Cover NW (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	9% 13% 7% 12% 13% 7% 8% 9% 7% 6% 11%	949
	11th to 20th	Day	8% 16% 4 13% 9% 5% 10% 10% 7% 6% 12%	950
	21st to end	Day	5% 15% 8% 13% 10% 7% 8% 7% 7% 6% 13%	1282
February	1st to 10th	Day	4 8% 7% 13% 12% 7% 11% 7% 8% 7% 16%	1269
	11th to 20th	Day	5% 10% 4 11% 10% 5% 8% 8% 8% 10% 21%	1432
	21st to end	Day	3 9% 6% 13% 12% 7% 7% 6% 8% 7% 20%	1332
March	1st to 10th	Day	5% 9% 5% 9% 8% 5% 6% 7% 6% 7% 34%	1705
	11th to 20th	Day	5% 11% 7% 10% 9% 5% 6% 7% 5% 6% 29%	1968
	21st to end	Day	6% 9% 4 9% 9% 6% 7% 7% 6% 7% 32%	2211
April	1st to 10th	Day	8% 12% 5% 8% 7% 4 5% 5% 5% 6% 35%	2340
	11th to 20th	Day	5% 8% 4 9% 6% 4 5% 5% 6% 7% 40%	2314
	21st to end	Day	9% 8% 4 8% 7% 3 5% 5% 7% 8% 36%	2641
May	1st to 10th	Day	10% 9% 4 7% 6% 3 5% 5% 6% 8% 38%	2700
	11th to 20th	Day	9% 7% 3 7% 7% 4 6% 5% 6% 9% 40%	2815
	21st to end	Day	10% 5% 3 5% 6% 3 6% 5% 5% 7% 45%	3305
June	1st to 10th	Day	13% 9% 4 8% 6% 4 5% 5% 6% 7% 33%	3060
	11th to 20th	Day	13% 6% 3 6% 7% 4 6% 5% 6% 8% 35%	3060
	21st to end	Day	8% 6% 2 6% 6% 4 7% 6% 7% 9% 40%	3060
July	1st to 10th	Day	10% 7% 4 8% 7% 5% 7% 6% 7% 8% 32%	3060
	11th to 20th	Day	11% 6% 3 7% 6% 5% 6% 6% 7% 9% 34%	3060
	21st to end	Day	9% 5% 3 6% 7% 5% 7% 7% 7% 9% 34%	3183
August	1st to 10th	Day	11% 5% 3 7% 6% 4 5% 5% 6% 7% 42%	2686
	11th to 20th	Day	17% 8% 4 7% 6% 4 5% 5% 6% 6% 32%	2648
	21st to end	Day	18% 7% 3 6% 6% 4 5% 6% 6% 9% 31%	2587
September	1st to 10th	Day	16% 9% 3 6% 6% 4 5% 6% 6% 8% 33%	2340
	11th to 20th	Day	16% 10% 4 8% 7% 3 5% 5% 5% 6% 31%	2057
	21st to end	Day	16% 11% 4 7% 7% 3 5% 5% 6% 7% 28%	1976
October	1st to 10th	Day	15% 16% 5% 6% 6% 3 4 4 5% 6% 29%	1792
	11th to 20th	Day	14% 18% 7% 10% 6% 3 5% 4 6% 7% 22%	1602
	21st to end	Day	13% 23% 10% 11% 8% 4 4 4 4 5% 13%	1584
November	1st to 10th	Day	16% 17% 7% 13% 7% 5% 5% 4 4 4 18%	1340
	11th to 20th	Day	10% 17% 8% 17% 13% 6% 6% 4 3 3 12%	1155
	21st to end	Day	9% 18% 8% 14% 11% 6% 7% 4 4 4 13%	1064
December	1st to 10th	Day	5% 16% 7% 16% 13% 6% 6% 9% 5% 5% 11%	950
	11th to 20th	Day	8% 14% 8% 13% 13% 4 8% 8% 6% 7% 12%	1199
	21st to end	Day	6% 10% 5% 11% 10% 6% 7% 6% 6% 8% 25%	1738
January	1st to 10th	Night	7% 14% 7% 14% 13% 5% 8% 8% 7% 5% 12%	3216
	11th to 20th	Night	9% 13% 6% 13% 11% 6% 9% 9% 6% 6% 13%	3039
	21st to end	Night	9% 16% 7% 13% 8% 5% 7% 8% 7% 6% 16%	3074
February	1st to 10th	Night	3 7% 4 12% 11% 8% 10% 10% 7% 7% 19%	2700
	11th to 20th	Night	4 10% 6% 11% 9% 5% 7% 8% 7% 8% 24%	2419
	21st to end	Night	3 9% 6% 12% 11% 6% 8% 5% 7% 6% 26%	1924
March	1st to 10th	Night	3 8% 4 10% 8% 6% 6% 6% 7% 7% 34%	2252
	11th to 20th	Night	6% 10% 5% 10% 8% 4 6% 5% 5% 6% 33%	1991
	21st to end	Night	4 7% 5% 6% 6% 5% 6% 7% 7% 8% 39%	2144
April	1st to 10th	Night	8% 13% 4 8% 5% 3 5% 6% 5% 8% 36%	1620
	11th to 20th	Night	4 8% 4 7% 7% 3 4 5% 5% 11% 42%	1597
	21st to end	Night	7% 8% 3 8% 7% 3 6% 6% 8% 9% 36%	1316
May	1st to 10th	Night	8% 7% 4 7% 6% 4 5% 5% 5% 8% 40%	1260
	11th to 20th	Night	7% 7% 2 7% 7% 3 7% 6% 6% 8% 40%	1078
	21st to end	Night	11% 5% 2 5% 7% 2 5% 4 6% 7% 47%	970
June	1st to 10th	Night	15% 7% 4 7% 6% 3 6% 7% 6% 10% 31%	900
	11th to 20th	Night	12% 5% 4 8% 5% 3 6% 6% 7% 7% 39%	900
	21st to end	Night	5% 4 2 6% 5% 5% 6% 7% 9% 8% 42%	900
July	1st to 10th	Night	11% 6% 3 5% 5% 5% 4 8% 7% 10% 35%	900
	11th to 20th	Night	9% 4 3 4 7% 4 6% 8% 6% 9% 39%	900
	21st to end	Night	6% 5% 3 5% 6% 4 7% 6% 10% 11% 37%	1133
August	1st to 10th	Night	10% 7% 3 6% 5% 3 4 5% 6% 7% 43%	1253
	11th to 20th	Night	13% 6% 3 7% 9% 3 5% 6% 6% 10% 32%	1250
	21st to end	Night	14% 8% 3 6% 7% 4 5% 6% 7% 7% 34%	1769
September	1st to 10th	Night	14% 8% 3 6% 6% 4 5% 4 7% 9% 34%	1620
	11th to 20th	Night	19% 8% 2 5% 6% 3 4 4 6% 7% 35%	1901
	21st to end	Night	14% 11% 4 6% 5% 3 6% 5% 6% 8% 32%	1984
October	1st to 10th	Night	13% 14% 5% 6% 6% 3 4 4 5% 7% 32%	2167
	11th to 20th	Night	13% 16% 7% 9% 6% 4 4 5% 5% 7% 25%	2340
	21st to end	Night	11% 22% 9% 11% 8% 4 4 5% 4 5% 16%	2772
November	1st to 10th	Night	12% 16% 8% 15% 10% 5% 4 4 4 5% 16%	2734
	11th to 20th	Night	11% 16% 8% 16% 12% 6% 6% 5% 4 4 13%	3025
	21st to end	Night	9% 16% 8% 15% 12% 7% 7% 7% 5% 4 10%	3116
December	1st to 10th	Night	8% 15% 9% 15% 11% 6% 8% 7% 6% 5% 11%	3230
	11th to 20th	Night	6% 13% 7% 15% 12% 7% 11% 8% 6% 6% 10%	3993
	21st to end	Night	6% 10% 5% 10% 9% 6% 7% 7% 6% 6% 28%	5918

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	70% 6% 13% 8% 2	949
	11th to 20th	Day	70% 7% 9% 11% 3 1	950
	21st to end	Day	68% 5% 9% 13% 5%	1282
February	1st to 10th	Day	62% 5% 9% 17% 7%	1269
	11th to 20th	Day	55% 7% 16% 16% 5%	1440
	21st to end	Day	59% 5% 12% 19% 5%	1332
March	1st to 10th	Day	49% 6% 15% 23% 6% 1	1705
	11th to 20th	Day	54% 7% 11% 22% 6%	1969
	21st to end	Day	51% 8% 13% 22% 6%	2211
April	1st to 10th	Day	49% 6% 12% 23% 9%	2340
	11th to 20th	Day	42% 7% 13% 28% 11%	2314
	21st to end	Day	44% 6% 13% 31% 6%	2641
May	1st to 10th	Day	44% 6% 11% 23% 14% 1	2700
	11th to 20th	Day	41% 7% 13% 23% 15%	2819
	21st to end	Day	36% 7% 10% 25% 20% 2	3306
June	1st to 10th	Day	49% 7% 10% 23% 11% 1	3060
	11th to 20th	Day	46% 8% 14% 21% 10%	3060
	21st to end	Day	38% 10% 16% 26% 9%	3060
July	1st to 10th	Day	47% 9% 14% 23% 6%	2976
	11th to 20th	Day	44% 9% 20% 23% 4	2967
	21st to end	Day	42% 11% 18% 26% 3	3006
August	1st to 10th	Day	40% 9% 19% 27% 4 1	2668
	11th to 20th	Day	51% 9% 18% 15% 6% 1	2648
	21st to end	Day	49% 9% 23% 18% 1	2587
September	1st to 10th	Day	48% 11% 22% 18% 2	2340
	11th to 20th	Day	53% 8% 18% 20% 2	2057
	21st to end	Day	54% 9% 19% 14% 3	1976
October	1st to 10th	Day	56% 8% 18% 16% 2	1792
	11th to 20th	Day	61% 8% 16% 14% 1	1602
	21st to end	Day	73% 8% 10% 8% 1	1584
November	1st to 10th	Day	69% 7% 11% 10% 2	1340
	11th to 20th	Day	77% 6% 8% 8% 1	1155
	21st to end	Day	74% 7% 8% 8% 3	1064
December	1st to 10th	Day	70% 8% 11% 8% 3	950
	11th to 20th	Day	68% 8% 9% 11% 4	1200
	21st to end	Day	54% 6% 13% 22% 4	1738
January	1st to 10th	Night	70% 7% 11% 11% 2	3216
	11th to 20th	Night	68% 7% 10% 13% 2	3039
	21st to end	Night	65% 7% 11% 12% 6%	3074
February	1st to 10th	Night	59% 6% 13% 17% 5%	2700
	11th to 20th	Night	54% 6% 17% 18% 4	2421
	21st to end	Night	57% 6% 13% 17% 8% 1	1924
March	1st to 10th	Night	45% 7% 16% 23% 7% 2	2252
	11th to 20th	Night	51% 6% 13% 21% 9%	1991
	21st to end	Night	40% 8% 17% 27% 7% 1	2144
April	1st to 10th	Night	47% 7% 12% 22% 12% 1	1620
	11th to 20th	Night	38% 6% 13% 29% 13%	1597
	21st to end	Night	40% 7% 12% 33% 8%	1316
May	1st to 10th	Night	42% 6% 11% 25% 15% 1	1260
	11th to 20th	Night	40% 8% 11% 24% 17%	1078
	21st to end	Night	35% 6% 9% 26% 23% 1	970
June	1st to 10th	Night	47% 8% 13% 23% 9% 1	900
	11th to 20th	Night	41% 7% 14% 28% 9%	900
	21st to end	Night	32% 11% 20% 24% 13%	900
July	1st to 10th	Night	41% 9% 16% 26% 7% 1	875
	11th to 20th	Night	37% 10% 20% 29% 4	870
	21st to end	Night	34% 12% 24% 29% 2	1070
August	1st to 10th	Night	39% 9% 18% 29% 6%	1246
	11th to 20th	Night	47% 11% 20% 16% 5% 2	1250
	21st to end	Night	47% 8% 21% 21% 3	1769
September	1st to 10th	Night	45% 11% 24% 15% 5%	1620
	11th to 20th	Night	47% 7% 19% 22% 4	1901
	21st to end	Night	49% 10% 21% 15% 5%	1984
October	1st to 10th	Night	52% 6% 18% 19% 3 1	2167
	11th to 20th	Night	59% 8% 17% 15% 2	2340
	21st to end	Night	70% 9% 11% 10% 1	2772
November	1st to 10th	Night	71% 6% 11% 11% 1	2734
	11th to 20th	Night	76% 7% 8% 7% 2	3025
	21st to end	Night	75% 7% 10% 7% 1	3116
December	1st to 10th	Night	73% 8% 10% 7% 2	3230
	11th to 20th	Night	72% 8% 9% 8% 4	3991
	21st to end	Night	52% 8% 20% 15% 5%	5918

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	8% 12% 34% 31% 14% 1	180
	11th to 20th	Day	16% 10% 29% 28% 13% 4	162
	21st to end	Day	14% 11% 36% 24% 11% 5%	176
February	1st to 10th	Day	7% 7% 41% 26% 15% 5%	160
	11th to 20th	Day	7% 9% 39% 28% 14% 3	174
	21st to end	Day	4 8% 28% 38% 18% 5%	198
March	1st to 10th	Day	8% 9% 36% 26% 14% 6%	325
	11th to 20th	Day	10% 12% 38% 31% 7% 1	420
	21st to end	Day	10% 13% 38% 25% 11% 3	462
April	1st to 10th	Day	15% 15% 35% 21% 11% 3	420
	11th to 20th	Day	10% 10% 36% 27% 11% 6%	416
	21st to end	Day	14% 10% 32% 29% 14% 2	600
May	1st to 10th	Day	18% 10% 28% 30% 13% 1	603
	11th to 20th	Day	12% 11% 26% 29% 17% 5%	654
	21st to end	Day	12% 10% 29% 33% 14% 3	874
June	1st to 10th	Day	21% 9% 27% 30% 10% 3	810
	11th to 20th	Day	17% 9% 29% 29% 13% 3	810
	21st to end	Day	9% 7% 23% 36% 20% 4	810
July	1st to 10th	Day	16% 8% 21% 35% 15% 6%	796
	11th to 20th	Day	13% 5% 19% 36% 22% 5%	792
	21st to end	Day	12% 5% 21% 30% 26% 6%	841
August	1st to 10th	Day	13% 6% 20% 29% 23% 9%	626
	11th to 20th	Day	21% 9% 23% 30% 14% 3	610
	21st to end	Day	19% 8% 19% 34% 17% 3	495
September	1st to 10th	Day	23% 11% 29% 21% 11% 4	450
	11th to 20th	Day	20% 10% 28% 27% 14% 2	450
	21st to end	Day	21% 12% 32% 28% 7% 1	446
October	1st to 10th	Day	29% 8% 28% 22% 9% 4	270
	11th to 20th	Day	24% 12% 36% 20% 6% 3	270
	21st to end	Day	22% 11% 35% 22% 8% 2	297
November	1st to 10th	Day	19% 11% 38% 18% 12% 2	198
	11th to 20th	Day	19% 10% 40% 19% 8% 3	180
	21st to end	Day	18% 9% 37% 22% 13% 1	180
December	1st to 10th	Day	12% 4 30% 36% 14% 3	180
	11th to 20th	Day	14% 8% 33% 27% 14% 5%	180
	21st to end	Day	6% 7% 29% 32% 14% 12%	198
January	1st to 10th	Night	12% 8% 31% 32% 14% 3	1040
	11th to 20th	Night	15% 8% 33% 32% 11% 1	989
	21st to end	Night	17% 11% 31% 28% 11% 3	1036
February	1st to 10th	Night	7% 8% 35% 31% 14% 5%	900
	11th to 20th	Night	8% 8% 35% 35% 13% 2	709
	21st to end	Night	6% 8% 33% 35% 17% 2	592
March	1st to 10th	Night	6% 8% 28% 34% 19% 4	720
	11th to 20th	Night	12% 9% 33% 33% 12% 1	720
	21st to end	Night	7% 7% 33% 34% 17% 2	784
April	1st to 10th	Night	14% 10% 30% 30% 13% 2	540
	11th to 20th	Night	8% 7% 34% 33% 17% 1	533
	21st to end	Night	11% 7% 33% 33% 14% 2	416
May	1st to 10th	Night	10% 9% 31% 35% 14% 1	360
	11th to 20th	Night	12% 7% 34% 31% 16% 1	354
	21st to end	Night	12% 5% 31% 34% 15% 2	389
June	1st to 10th	Night	17% 9% 28% 29% 14% 3	360
	11th to 20th	Night	13% 4 23% 40% 20% 1	360
	21st to end	Night	6% 3 24% 37% 27% 2	360
July	1st to 10th	Night	10% 8% 19% 37% 22% 4	350
	11th to 20th	Night	11% 2 18% 41% 25% 3	348
	21st to end	Night	8% 3 17% 36% 31% 5%	394
August	1st to 10th	Night	13% 4 16% 39% 22% 6%	358
	11th to 20th	Night	16% 4 22% 37% 18% 3	356
	21st to end	Night	18% 4 25% 33% 17% 3	581
September	1st to 10th	Night	18% 7% 24% 30% 18% 3	540
	11th to 20th	Night	23% 6% 23% 32% 14% 3	641
	21st to end	Night	20% 7% 30% 30% 11% 1	720
October	1st to 10th	Night	21% 11% 28% 27% 11% 3	720
	11th to 20th	Night	22% 7% 30% 28% 12% 2	720
	21st to end	Night	23% 11% 26% 26% 13% 2	990
November	1st to 10th	Night	17% 8% 30% 27% 15% 2	925
	11th to 20th	Night	19% 10% 31% 27% 11% 3	950
	21st to end	Night	18% 11% 32% 25% 13% 2	986
December	1st to 10th	Night	15% 7% 31% 34% 11% 2	1040
	11th to 20th	Night	13% 11% 35% 27% 12% 3	1040
	21st to end	Night	12% 8% 29% 26% 20% 5%	1144

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