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 2024-11-05.

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	9% 9% 4 9% 6% 6% 6% 5% 7% 7% 32%	106180
	Night	8% 12% 5% 12% 7% 7% 7% 5% 6% 6% 26%	101391
Transparency	Day	25% 48% 8% 14% 5%	105883
	Night	30% 48% 8% 11% 4	101334
Seeing	Day	15% 9% 28% 29% 15% 4	16967
	Night	14% 8% 30% 31% 15% 3	24933

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	5% 10% 5% 17% 14% 13% 12% 7% 6% 3 7%	1579
	11th to 20th	Day	4 11% 3 12% 9% 8% 13% 9% 10% 9% 12%	1638
	21st to end	Day	10% 21% 6% 13% 7% 7% 5% 5% 9% 6% 13%	2254
February	1st to 10th	Day	4 9% 7% 15% 10% 9% 9% 6% 8% 7% 16%	1339
	11th to 20th	Day	4 11% 4 13% 8% 6% 8% 6% 8% 9% 22%	1513
	21st to end	Day	3 10% 5% 14% 11% 10% 6% 7% 9% 7% 19%	1413
March	1st to 10th	Day	5% 9% 5% 11% 9% 8% 8% 6% 9% 8% 23%	2979
	11th to 20th	Day	4 10% 6% 16% 8% 7% 6% 6% 7% 7% 24%	3478
	21st to end	Day	3 6% 4 10% 6% 6% 5% 4 6% 7% 43%	3895
April	1st to 10th	Day	8% 13% 4 9% 7% 5% 5% 4 5% 6% 35%	2470
	11th to 20th	Day	5% 9% 3 9% 6% 5% 5% 4 7% 6% 40%	2445
	21st to end	Day	9% 9% 3 9% 6% 5% 5% 4 7% 8% 36%	2788
May	1st to 10th	Day	7% 7% 3 8% 5% 5% 5% 5% 7% 9% 39%	4740
	11th to 20th	Day	10% 11% 3 9% 5% 5% 5% 4 6% 7% 34%	4995
	21st to end	Day	15% 5% 2 5% 4 5% 5% 5% 6% 9% 41%	5857
June	1st to 10th	Day	13% 10% 3 9% 5% 5% 5% 4 6% 7% 33%	3230
	11th to 20th	Day	13% 7% 2 8% 6% 6% 5% 4 6% 8% 35%	3230
	21st to end	Day	7% 6% 2 7% 5% 6% 6% 5% 7% 8% 40%	3230
July	1st to 10th	Day	7% 5% 3 8% 6% 7% 7% 5% 9% 10% 33%	5380
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 4 6% 7% 46%	5380
	21st to end	Day	12% 6% 2 7% 5% 6% 7% 5% 8% 10% 34%	5551
August	1st to 10th	Day	7% 4 2 6% 5% 5% 5% 3 5% 7% 52%	4720
	11th to 20th	Day	13% 7% 3 8% 5% 5% 4 4 6% 6% 39%	4626
	21st to end	Day	15% 7% 3 8% 6% 6% 6% 5% 7% 9% 29%	4534
September	1st to 10th	Day	16% 9% 3 7% 5% 5% 5% 4 7% 8% 31%	2470
	11th to 20th	Day	15% 10% 4 9% 5% 5% 4 4 5% 7% 31%	2171
	21st to end	Day	16% 12% 4 9% 6% 5% 5% 4 6% 7% 29%	2085
October	1st to 10th	Day	11% 19% 5% 7% 5% 5% 3 3 6% 7% 30%	3149
	11th to 20th	Day	14% 16% 5% 10% 5% 4 4 3 6% 7% 27%	2811
	21st to end	Day	8% 19% 10% 15% 6% 5% 5% 4 5% 6% 18%	2754
November	1st to 10th	Day	15% 19% 7% 14% 5% 6% 5% 3 4 4 18%	1370
	11th to 20th	Day	10% 19% 7% 20% 10% 9% 4 3 3 3 12%	1155
	21st to end	Day	9% 20% 7% 17% 9% 8% 5% 3 4 4 13%	1064
December	1st to 10th	Day	5% 18% 6% 17% 11% 8% 6% 7% 5% 5% 11%	950
	11th to 20th	Day	7% 15% 7% 15% 11% 6% 9% 5% 7% 7% 12%	1199
	21st to end	Day	5% 11% 4 13% 8% 7% 7% 4 7% 8% 25%	1738
January	1st to 10th	Night	4 13% 7% 20% 13% 10% 11% 6% 5% 3 7%	5366
	11th to 20th	Night	5% 10% 4 12% 7% 7% 14% 9% 10% 6% 15%	5260
	21st to end	Night	8% 16% 5% 14% 8% 7% 7% 6% 8% 5% 14%	5402
February	1st to 10th	Night	4 8% 4 14% 10% 10% 10% 8% 7% 7% 19%	2850
	11th to 20th	Night	4 10% 5% 13% 7% 7% 6% 6% 7% 8% 25%	2559
	21st to end	Night	3 10% 5% 14% 9% 8% 8% 4 8% 6% 25%	2041
March	1st to 10th	Night	3 8% 6% 15% 7% 7% 6% 5% 8% 6% 28%	3887
	11th to 20th	Night	6% 10% 4 14% 7% 6% 7% 4 8% 7% 27%	3501
	21st to end	Night	2 7% 3 7% 4 5% 4 5% 6% 8% 48%	3756
April	1st to 10th	Night	8% 14% 4 9% 4 4 5% 5% 5% 7% 36%	1710
	11th to 20th	Night	4 9% 3 7% 6% 4 4 4 6% 10% 43%	1686
	21st to end	Night	6% 8% 3 8% 6% 6% 5% 5% 8% 9% 36%	1389
May	1st to 10th	Night	10% 8% 3 7% 5% 4 5% 5% 6% 8% 39%	2220
	11th to 20th	Night	8% 9% 3 9% 6% 5% 6% 4 6% 7% 35%	1898
	21st to end	Night	15% 6% 2 6% 5% 4 3 3 7% 8% 42%	1718
June	1st to 10th	Night	15% 7% 3 8% 6% 4 5% 5% 6% 9% 31%	950
	11th to 20th	Night	11% 6% 4 9% 4 5% 6% 5% 7% 7% 39%	950
	21st to end	Night	5% 4 2 7% 5% 6% 6% 6% 10% 7% 42%	950
July	1st to 10th	Night	8% 6% 2 7% 5% 6% 6% 7% 7% 10% 36%	1580
	11th to 20th	Night	8% 4 2 4 5% 5% 5% 5% 7% 9% 47%	1580
	21st to end	Night	10% 7% 2 5% 5% 5% 6% 5% 10% 11% 33%	1986
August	1st to 10th	Night	9% 6% 2 6% 3 4 4 3 5% 6% 52%	2210
	11th to 20th	Night	11% 5% 2 7% 5% 6% 5% 4 6% 8% 41%	2200
	21st to end	Night	16% 7% 3 8% 6% 5% 5% 4 6% 7% 32%	3133
September	1st to 10th	Night	14% 9% 3 7% 5% 5% 5% 4 7% 9% 33%	1710
	11th to 20th	Night	17% 9% 2 7% 5% 4 4 3 6% 7% 35%	2007
	21st to end	Night	13% 11% 3 7% 4 5% 5% 4 6% 8% 33%	2095
October	1st to 10th	Night	11% 17% 4 9% 5% 5% 5% 4 6% 7% 28%	3820
	11th to 20th	Night	13% 16% 6% 9% 5% 5% 5% 4 5% 7% 25%	4086
	21st to end	Night	12% 21% 8% 15% 7% 6% 5% 3 4 5% 14%	4804
November	1st to 10th	Night	12% 18% 7% 17% 8% 6% 4 3 4 5% 16%	2805
	11th to 20th	Night	10% 17% 7% 17% 11% 8% 5% 4 4 4 12%	3025
	21st to end	Night	9% 18% 7% 17% 11% 9% 6% 5% 4 4 10%	3116
December	1st to 10th	Night	8% 17% 8% 17% 9% 8% 8% 6% 6% 5% 11%	3230
	11th to 20th	Night	6% 14% 6% 17% 10% 10% 10% 6% 6% 5% 10%	3993
	21st to end	Night	5% 11% 4 12% 8% 8% 7% 5% 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	52% 40% 4 3 1	1579
	11th to 20th	Day	36% 41% 9% 10% 4	1653
	21st to end	Day	43% 41% 8% 5% 3	2254
February	1st to 10th	Day	23% 66% 3 5% 3	1339
	11th to 20th	Day	21% 66% 5% 7% 1	1521
	21st to end	Day	21% 65% 2 7% 4	1413
March	1st to 10th	Day	33% 43% 9% 14% 1	2979
	11th to 20th	Day	34% 42% 6% 14% 4	3479
	21st to end	Day	19% 41% 5% 18% 17%	3895
April	1st to 10th	Day	15% 65% 4 9% 7%	2470
	11th to 20th	Day	13% 66% 4 9% 7%	2445
	21st to end	Day	14% 66% 4 13% 3	2788
May	1st to 10th	Day	22% 43% 7% 15% 12% 1	4740
	11th to 20th	Day	28% 42% 6% 14% 10%	4999
	21st to end	Day	22% 42% 8% 18% 9%	5858
June	1st to 10th	Day	20% 66% 4 7% 3	3230
	11th to 20th	Day	17% 66% 3 9% 5%	3230
	21st to end	Day	14% 66% 5% 10% 5%	3230
July	1st to 10th	Day	27% 39% 15% 15% 4	5296
	11th to 20th	Day	20% 37% 6% 29% 7% 1	5287
	21st to end	Day	28% 39% 11% 20% 1	5375
August	1st to 10th	Day	18% 38% 10% 24% 9% 1	4702
	11th to 20th	Day	25% 39% 7% 16% 13%	4671
	21st to end	Day	32% 40% 15% 12% 1	4533
September	1st to 10th	Day	21% 61% 9% 8% 1	2470
	11th to 20th	Day	20% 60% 8% 10% 1	2171
	21st to end	Day	21% 61% 7% 8% 3	2085
October	1st to 10th	Day	35% 38% 11% 14% 2	3149
	11th to 20th	Day	37% 38% 8% 15% 2	2811
	21st to end	Day	41% 39% 11% 9%	2754
November	1st to 10th	Day	30% 59% 6% 4 1	1370
	11th to 20th	Day	30% 61% 5% 4 1	1155
	21st to end	Day	29% 61% 5% 4 1	1064
December	1st to 10th	Day	29% 62% 6% 2 1	950
	11th to 20th	Day	37% 50% 5% 6% 2	1200
	21st to end	Day	30% 39% 9% 18% 4	1738
January	1st to 10th	Night	53% 39% 4 4 1	5366
	11th to 20th	Night	35% 40% 10% 11% 5%	5307
	21st to end	Night	42% 42% 7% 8% 2	5402
February	1st to 10th	Night	23% 66% 4 6% 2	2850
	11th to 20th	Night	20% 65% 6% 8% 1	2561
	21st to end	Night	19% 65% 4 6% 5% 1	2041
March	1st to 10th	Night	33% 42% 11% 12% 1	3887
	11th to 20th	Night	31% 43% 7% 13% 5%	3501
	21st to end	Night	14% 41% 5% 23% 16%	3756
April	1st to 10th	Night	14% 65% 3 11% 6%	1710
	11th to 20th	Night	13% 65% 4 10% 8%	1686
	21st to end	Night	12% 66% 4 14% 4	1389
May	1st to 10th	Night	25% 42% 8% 15% 10%	2220
	11th to 20th	Night	25% 44% 7% 15% 8% 1	1898
	21st to end	Night	25% 42% 5% 17% 11% 1	1718
June	1st to 10th	Night	20% 66% 4 7% 2	950
	11th to 20th	Night	14% 65% 5% 10% 7%	950
	21st to end	Night	14% 67% 5% 7% 7%	950
July	1st to 10th	Night	26% 39% 13% 21% 1	1555
	11th to 20th	Night	17% 38% 9% 27% 9%	1550
	21st to end	Night	28% 38% 13% 20% 1	1923
August	1st to 10th	Night	19% 38% 8% 24% 12%	2203
	11th to 20th	Night	22% 39% 8% 17% 14% 1	2221
	21st to end	Night	34% 39% 15% 11% 1	3133
September	1st to 10th	Night	20% 62% 7% 8% 2	1710
	11th to 20th	Night	16% 60% 9% 13% 2	2007
	21st to end	Night	17% 62% 10% 8% 3	2095
October	1st to 10th	Night	39% 38% 9% 15%	3820
	11th to 20th	Night	40% 39% 10% 10% 1	4086
	21st to end	Night	48% 39% 6% 6% 1	4804
November	1st to 10th	Night	31% 58% 5% 6%	2805
	11th to 20th	Night	30% 61% 4 4 1	3025
	21st to end	Night	30% 62% 4 4 1	3116
December	1st to 10th	Night	30% 61% 5% 2 2	3230
	11th to 20th	Night	40% 51% 4 3 3	3991
	21st to end	Night	27% 40% 16% 12% 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% 35% 29% 14% 1	180
	11th to 20th	Day	14% 9% 29% 29% 14% 3	180
	21st to end	Day	18% 13% 34% 21% 10% 4	198
February	1st to 10th	Day	11% 7% 37% 26% 14% 6%	180
	11th to 20th	Day	6% 8% 39% 28% 15% 3	195
	21st to end	Day	4 10% 30% 37% 16% 4	225
March	1st to 10th	Day	8% 9% 37% 26% 13% 5%	360
	11th to 20th	Day	11% 13% 37% 31% 7% 2	460
	21st to end	Day	10% 13% 37% 25% 12% 4	506
April	1st to 10th	Day	15% 15% 35% 21% 12% 3	460
	11th to 20th	Day	10% 10% 35% 29% 11% 5%	457
	21st to end	Day	14% 10% 30% 30% 14% 2	650
May	1st to 10th	Day	18% 10% 28% 29% 14% 1	653
	11th to 20th	Day	13% 11% 26% 29% 17% 4	706
	21st to end	Day	13% 9% 28% 33% 14% 3	940
June	1st to 10th	Day	22% 9% 28% 29% 10% 3	870
	11th to 20th	Day	17% 9% 29% 28% 14% 3	870
	21st to end	Day	8% 7% 24% 36% 20% 4	870
July	1st to 10th	Day	15% 8% 22% 35% 14% 6%	856
	11th to 20th	Day	12% 6% 19% 37% 22% 5%	852
	21st to end	Day	12% 5% 21% 30% 25% 6%	904
August	1st to 10th	Day	12% 6% 20% 29% 25% 8%	676
	11th to 20th	Day	21% 9% 24% 31% 14% 2	659
	21st to end	Day	19% 9% 21% 32% 16% 3	539
September	1st to 10th	Day	23% 11% 30% 20% 11% 4	490
	11th to 20th	Day	18% 10% 27% 28% 14% 2	490
	21st to end	Day	20% 13% 31% 28% 7% 1	485
October	1st to 10th	Day	28% 9% 29% 21% 9% 5%	300
	11th to 20th	Day	23% 13% 35% 20% 7% 2	300
	21st to end	Day	19% 13% 36% 22% 8% 2	330
November	1st to 10th	Day	20% 11% 38% 17% 13% 2	208
	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	14% 8% 32% 32% 12% 1	1040
	21st to end	Night	16% 11% 31% 28% 10% 3	1097
February	1st to 10th	Night	7% 9% 35% 31% 14% 5%	950
	11th to 20th	Night	8% 8% 35% 35% 13% 2	750
	21st to end	Night	6% 8% 34% 34% 17% 1	628
March	1st to 10th	Night	6% 8% 28% 35% 19% 4	760
	11th to 20th	Night	12% 9% 33% 33% 11% 1	760
	21st to end	Night	6% 7% 33% 34% 17% 2	827
April	1st to 10th	Night	15% 10% 31% 29% 13% 2	570
	11th to 20th	Night	7% 7% 34% 34% 17% 1	563
	21st to end	Night	10% 7% 32% 35% 14% 2	439
May	1st to 10th	Night	10% 9% 32% 35% 13% 1	380
	11th to 20th	Night	12% 7% 34% 31% 15% 1	374
	21st to end	Night	13% 6% 31% 35% 14% 2	411
June	1st to 10th	Night	18% 9% 28% 29% 13% 3	380
	11th to 20th	Night	13% 4 23% 39% 20% 1	380
	21st to end	Night	6% 3 25% 38% 26% 2	380
July	1st to 10th	Night	10% 8% 18% 37% 22% 4	370
	11th to 20th	Night	11% 2 18% 40% 25% 3	368
	21st to end	Night	8% 2 17% 37% 31% 5%	416
August	1st to 10th	Night	13% 4 16% 39% 22% 5%	378
	11th to 20th	Night	16% 5% 22% 37% 17% 2	376
	21st to end	Night	18% 4 26% 34% 16% 3	614
September	1st to 10th	Night	18% 7% 24% 30% 18% 3	570
	11th to 20th	Night	22% 6% 23% 33% 13% 3	677
	21st to end	Night	19% 7% 31% 29% 12% 1	760
October	1st to 10th	Night	22% 11% 28% 26% 11% 3	760
	11th to 20th	Night	22% 7% 31% 27% 11% 2	760
	21st to end	Night	22% 12% 26% 26% 12% 2	1045
November	1st to 10th	Night	17% 8% 30% 27% 15% 2	950
	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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