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 2024-02-15.

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% 5% 2 5% 5% 3 4 4 5% 7% 46%	78807
	Night	13% 5% 2 4 4 2 4 4 5% 6% 51%	80330
Transparency	Day	37% 6% 10% 23% 19% 4	78531
	Night	34% 5% 10% 23% 22% 6%	80126
Seeing	Day	13% 7% 20% 26% 25% 9%	14339
	Night	14% 5% 22% 37% 20% 2	24361

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% 4 5% 5% 3 4 4 3 4 46%	2847
	11th to 20th	Day	11% 7% 2 5% 5% 2 3 3 4 5% 54%	2850
	21st to end	Day	24% 7% 2 4 3 2 3 3 3 4 44%	3135
February	1st to 10th	Day	21% 8% 3 4 5% 2 3 3 4 4 43%	1710
	11th to 20th	Day	19% 7% 3 6% 4 2 4 4 4 6% 42%	1646
	21st to end	Day	21% 7% 3 5% 5% 2 4 4 4 6% 40%	1614
March	1st to 10th	Day	18% 6% 2 5% 4 2 3 4 5% 6% 48%	1980
	11th to 20th	Day	21% 7% 3 5% 5% 3 3 3 4 5% 41%	1980
	21st to end	Day	20% 7% 3 6% 5% 3 3 4 4 6% 38%	2178
April	1st to 10th	Day	14% 5% 3 4 5% 3 6% 4 5% 6% 45%	2060
	11th to 20th	Day	17% 6% 3 6% 5% 2 4 4 4 5% 44%	2134
	21st to end	Day	19% 7% 4 6% 5% 3 4 4 3 6% 40%	2160
May	1st to 10th	Day	18% 7% 3 6% 4 2 4 4 5% 6% 41%	2326
	11th to 20th	Day	12% 6% 3 6% 6% 4 5% 5% 5% 8% 41%	2302
	21st to end	Day	12% 4 3 6% 6% 4 5% 6% 6% 8% 40%	2531
June	1st to 10th	Day	9% 5% 2 5% 6% 4 5% 5% 6% 10% 44%	2340
	11th to 20th	Day	7% 4 2 5% 6% 3 6% 6% 7% 9% 46%	2340
	21st to end	Day	5% 2 2 3 4 3 6% 5% 6% 9% 54%	2340
July	1st to 10th	Day	9% 4 2 5% 6% 4 6% 5% 9% 11% 40%	2340
	11th to 20th	Day	4 2 1 4 4 3 6% 5% 7% 9% 53%	2340
	21st to end	Day	6% 4 2 5% 6% 3 6% 6% 7% 10% 45%	2546
August	1st to 10th	Day	6% 4 2 5% 6% 4 5% 7% 7% 9% 45%	2328
	11th to 20th	Day	9% 5% 2 4 5% 3 4 6% 6% 9% 46%	2270
	21st to end	Day	7% 3 2 5% 5% 3 6% 6% 6% 8% 51%	2376
September	1st to 10th	Day	11% 4 1 4 3 3 4 4 5% 7% 54%	2160
	11th to 20th	Day	12% 4 2 4 5% 2 4 4 5% 8% 49%	1981
	21st to end	Day	7% 3 2 4 4 3 5% 4 5% 6% 57%	1967
October	1st to 10th	Day	9% 4 2 5% 4 2 4 4 5% 6% 56%	1800
	11th to 20th	Day	14% 3 2 4 3 3 2 3 4 5% 58%	1800
	21st to end	Day	19% 5% 2 4 3 2 3 3 4 5% 50%	1980
November	1st to 10th	Day	11% 4 2 4 3 2 3 3 5% 6% 57%	1858
	11th to 20th	Day	12% 4 2 4 4 2 3 3 4 6% 57%	1872
	21st to end	Day	19% 5% 3 3 3 2 3 3 3 7% 49%	1710
December	1st to 10th	Day	17% 6% 2 5% 4 1 3 4 5% 6% 48%	1710
	11th to 20th	Day	16% 6% 3 7% 5% 3 3 3 5% 5% 43%	2161
	21st to end	Day	19% 12% 3 6% 4 2 4 4 5% 6% 34%	3135
January	1st to 10th	Night	14% 8% 3 6% 5% 3 4 5% 4 4 43%	4108
	11th to 20th	Night	12% 6% 2 3 3 2 3 2 4 6% 57%	4120
	21st to end	Night	24% 7% 2 3 3 2 2 4 3 4 45%	4532
February	1st to 10th	Night	18% 8% 2 5% 4 2 4 4 4 6% 43%	2470
	11th to 20th	Night	18% 7% 2 5% 3 2 2 4 4 6% 47%	2310
	21st to end	Night	19% 5% 3 5% 3 3 3 4 3 5% 46%	1640
March	1st to 10th	Night	17% 5% 2 6% 4 2 4 4 4 6% 48%	1980
	11th to 20th	Night	20% 5% 2 4 4 3 3 4 4 6% 44%	1980
	21st to end	Night	19% 5% 3 4 4 3 4 3 4 5% 45%	2178
April	1st to 10th	Night	15% 5% 1 4 4 2 4 4 5% 7% 50%	1900
	11th to 20th	Night	15% 5% 2 4 4 2 3 4 5% 7% 49%	1775
	21st to end	Night	15% 4 3 5% 5% 3 4 4 4 6% 47%	1800
May	1st to 10th	Night	11% 5% 3 5% 5% 3 4 3 5% 7% 48%	1630
	11th to 20th	Night	14% 5% 2 4 4 3 4 4 7% 7% 46%	1593
	21st to end	Night	9% 4 3 5% 4 4 4 5% 7% 11% 45%	1745
June	1st to 10th	Night	4 4 1 4 4 3 4 5% 5% 11% 56%	1620
	11th to 20th	Night	4 3 1 4 4 3 4 4 5% 11% 59%	1620
	21st to end	Night	4 2 1 3 3 2 3 4 6% 8% 64%	1620
July	1st to 10th	Night	4 3 2 4 5% 3 6% 6% 8% 12% 48%	1620
	11th to 20th	Night	3 2 1 3 4 2 4 4 8% 9% 60%	1620
	21st to end	Night	4 3 2 4 4 3 5% 5% 6% 10% 55%	1772
August	1st to 10th	Night	3 2 1 3 4 3 6% 7% 8% 10% 54%	1611
	11th to 20th	Night	7% 4 2 4 5% 4 4 6% 6% 9% 50%	1630
	21st to end	Night	5% 3 2 4 4 3 5% 5% 6% 8% 55%	1980
September	1st to 10th	Night	7% 4 2 4 4 2 4 3 5% 7% 59%	1800
	11th to 20th	Night	10% 3 2 5% 5% 2 4 5% 6% 6% 51%	1974
	21st to end	Night	7% 4 1 3 4 2 3 4 4 5% 60%	1980
October	1st to 10th	Night	7% 2 1 3 5% 2 4 4 5% 7% 60%	2153
	11th to 20th	Night	13% 3 2 3 3 2 3 3 4 4 59%	2160
	21st to end	Night	19% 4 1 4 4 2 2 3 3 4 54%	2376
November	1st to 10th	Night	11% 3 3 4 4 2 3 3 3 5% 60%	2220
	11th to 20th	Night	11% 4 2 4 3 2 3 3 4 6% 57%	2305
	21st to end	Night	19% 5% 2 3 3 2 3 3 3 6% 51%	2470
December	1st to 10th	Night	16% 6% 2 4 3 2 4 4 4 5% 50%	2470
	11th to 20th	Night	16% 6% 3 5% 4 3 4 4 4 4 47%	3036
	21st to end	Night	19% 9% 4 6% 4 3 3 4 5% 5% 38%	4532

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 6% 23% 23% 3	2848
	11th to 20th	Day	34% 4 13% 26% 20% 3	2850
	21st to end	Day	45% 3 6% 19% 22% 5%	3135
February	1st to 10th	Day	46% 4 10% 20% 17% 3	1710
	11th to 20th	Day	44% 4 7% 22% 18% 4	1655
	21st to end	Day	48% 3 6% 17% 18% 7%	1614
March	1st to 10th	Day	39% 4 8% 21% 18% 10%	1980
	11th to 20th	Day	47% 4 8% 22% 14% 5%	1980
	21st to end	Day	48% 5% 8% 24% 13% 2	2178
April	1st to 10th	Day	39% 5% 10% 21% 19% 5%	2060
	11th to 20th	Day	41% 5% 9% 23% 17% 5%	2134
	21st to end	Day	46% 6% 7% 21% 18% 2	2160
May	1st to 10th	Day	44% 6% 8% 21% 18% 2	2326
	11th to 20th	Day	39% 9% 12% 24% 14% 1	2306
	21st to end	Day	40% 8% 13% 23% 14% 1	2531
June	1st to 10th	Day	35% 8% 14% 25% 16% 2	2340
	11th to 20th	Day	33% 7% 15% 24% 19% 2	2340
	21st to end	Day	25% 8% 14% 28% 21% 5%	2340
July	1st to 10th	Day	35% 10% 16% 25% 13% 1	2276
	11th to 20th	Day	25% 8% 14% 29% 21% 3	2271
	21st to end	Day	31% 10% 15% 30% 13% 1	2405
August	1st to 10th	Day	32% 8% 14% 28% 15% 2	2314
	11th to 20th	Day	33% 8% 13% 25% 19% 2	2270
	21st to end	Day	30% 9% 14% 26% 17% 4	2376
September	1st to 10th	Day	29% 6% 10% 26% 19% 9%	2160
	11th to 20th	Day	33% 6% 10% 23% 23% 6%	1981
	21st to end	Day	27% 5% 12% 19% 29% 8%	1967
October	1st to 10th	Day	29% 6% 11% 20% 26% 9%	1800
	11th to 20th	Day	31% 4 6% 20% 29% 11%	1800
	21st to end	Day	38% 4 8% 23% 20% 8%	1980
November	1st to 10th	Day	28% 4 10% 25% 25% 7%	1858
	11th to 20th	Day	30% 3 6% 26% 25% 9%	1872
	21st to end	Day	38% 3 7% 19% 27% 5%	1710
December	1st to 10th	Day	37% 4 10% 25% 20% 4	1710
	11th to 20th	Day	44% 3 6% 21% 22% 5%	2159
	21st to end	Day	51% 4 9% 19% 13% 4	3135
January	1st to 10th	Night	43% 3 8% 19% 23% 3	4108
	11th to 20th	Night	30% 4 13% 24% 26% 3	4120
	21st to end	Night	43% 3 10% 18% 22% 4	4532
February	1st to 10th	Night	43% 4 8% 24% 17% 5%	2470
	11th to 20th	Night	39% 4 7% 24% 20% 5%	2311
	21st to end	Night	41% 3 7% 18% 22% 9%	1640
March	1st to 10th	Night	39% 4 8% 17% 21% 11%	1980
	11th to 20th	Night	42% 4 9% 21% 18% 7%	1980
	21st to end	Night	42% 4 8% 23% 18% 4	2178
April	1st to 10th	Night	34% 5% 10% 20% 22% 8%	1900
	11th to 20th	Night	35% 5% 8% 23% 20% 9%	1775
	21st to end	Night	38% 6% 8% 23% 24% 2	1800
May	1st to 10th	Night	35% 7% 11% 23% 19% 5%	1630
	11th to 20th	Night	36% 7% 12% 25% 18% 2	1594
	21st to end	Night	32% 9% 16% 27% 14% 1	1746
June	1st to 10th	Night	23% 8% 15% 32% 20% 3	1620
	11th to 20th	Night	21% 5% 14% 33% 24% 3	1620
	21st to end	Night	18% 5% 13% 30% 28% 7%	1620
July	1st to 10th	Night	25% 10% 17% 25% 21% 1	1575
	11th to 20th	Night	17% 7% 15% 30% 27% 3	1566
	21st to end	Night	22% 8% 16% 33% 18% 2	1673
August	1st to 10th	Night	22% 9% 17% 32% 18% 2	1601
	11th to 20th	Night	29% 7% 12% 25% 23% 3	1630
	21st to end	Night	26% 7% 14% 25% 23% 4	1980
September	1st to 10th	Night	25% 6% 10% 26% 23% 9%	1800
	11th to 20th	Night	31% 6% 11% 20% 24% 7%	1974
	21st to end	Night	25% 5% 9% 22% 30% 8%	1980
October	1st to 10th	Night	24% 6% 12% 22% 25% 11%	2153
	11th to 20th	Night	29% 5% 6% 16% 32% 13%	2160
	21st to end	Night	36% 3 6% 20% 23% 12%	2376
November	1st to 10th	Night	29% 4 7% 23% 27% 10%	2220
	11th to 20th	Night	28% 3 7% 24% 27% 10%	2305
	21st to end	Night	37% 4 8% 19% 27% 6%	2470
December	1st to 10th	Night	37% 4 9% 21% 22% 6%	2470
	11th to 20th	Night	42% 3 7% 21% 22% 6%	3037
	21st to end	Night	47% 4 10% 19% 16% 4	4532

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	20% 13% 32% 24% 9% 1	270
	11th to 20th	Day	22% 13% 38% 20% 7%	270
	21st to end	Day	20% 14% 35% 21% 9% 1	297
February	1st to 10th	Day	30% 9% 34% 20% 7%	270
	11th to 20th	Day	29% 12% 35% 18% 6%	252
	21st to end	Day	35% 14% 33% 13% 5%	198
March	1st to 10th	Day	22% 14% 32% 23% 9%	240
	11th to 20th	Day	29% 15% 33% 16% 7%	240
	21st to end	Day	23% 16% 37% 17% 7%	264
April	1st to 10th	Day	18% 13% 33% 25% 9% 3	320
	11th to 20th	Day	20% 12% 29% 29% 9% 1	412
	21st to end	Day	19% 12% 28% 29% 9% 2	420
May	1st to 10th	Day	16% 8% 27% 35% 12% 1	589
	11th to 20th	Day	13% 6% 23% 31% 23% 4	625
	21st to end	Day	11% 5% 21% 34% 23% 6%	679
June	1st to 10th	Day	9% 3 11% 27% 36% 13%	630
	11th to 20th	Day	7% 1 13% 32% 36% 12%	630
	21st to end	Day	4 1 13% 33% 35% 13%	630
July	1st to 10th	Day	7% 1 8% 23% 42% 19%	621
	11th to 20th	Day	4 1 7% 27% 39% 22%	618
	21st to end	Day	4 1 6% 24% 43% 23%	684
August	1st to 10th	Day	6% 2 8% 27% 45% 12%	626
	11th to 20th	Day	11% 1 8% 29% 39% 12%	584
	21st to end	Day	7% 5% 18% 48% 21%	495
September	1st to 10th	Day	10% 1 6% 20% 46% 17%	450
	11th to 20th	Day	5% 2 8% 30% 39% 17%	271
	21st to end	Day	11% 4 11% 28% 29% 17%	270
October	1st to 10th	Day	6% 2 25% 30% 30% 7%	270
	11th to 20th	Day	12% 12% 26% 30% 17% 3	270
	21st to end	Day	23% 16% 23% 24% 12% 3	297
November	1st to 10th	Day	15% 4 30% 26% 23% 2	270
	11th to 20th	Day	14% 11% 31% 28% 15% 1	270
	21st to end	Day	21% 12% 22% 29% 15% 1	270
December	1st to 10th	Day	16% 11% 39% 18% 12% 3	270
	11th to 20th	Day	21% 14% 29% 26% 10%	270
	21st to end	Day	21% 15% 33% 25% 5% 1	297
January	1st to 10th	Night	18% 7% 33% 36% 6%	950
	11th to 20th	Night	19% 8% 33% 34% 6%	950
	21st to end	Night	18% 5% 35% 38% 5%	1045
February	1st to 10th	Night	22% 8% 30% 35% 4	950
	11th to 20th	Night	21% 6% 35% 34% 4	880
	21st to end	Night	23% 8% 35% 32% 2	456
March	1st to 10th	Night	19% 7% 30% 40% 5%	540
	11th to 20th	Night	22% 6% 26% 37% 9%	540
	21st to end	Night	20% 8% 30% 35% 8%	594
April	1st to 10th	Night	16% 6% 32% 37% 9%	540
	11th to 20th	Night	13% 9% 29% 40% 9%	533
	21st to end	Night	16% 5% 33% 34% 11%	540
May	1st to 10th	Night	13% 4 26% 45% 13%	540
	11th to 20th	Night	15% 4 18% 44% 18% 1	531
	21st to end	Night	9% 3 16% 42% 28% 2	584
June	1st to 10th	Night	5% 2 7% 39% 44% 2	540
	11th to 20th	Night	6% 8% 48% 36% 3	540
	21st to end	Night	4 1 7% 39% 44% 5%	540
July	1st to 10th	Night	5% 1 5% 32% 51% 6%	525
	11th to 20th	Night	3 1 6% 32% 49% 9%	522
	21st to end	Night	4 4 30% 53% 8%	591
August	1st to 10th	Night	3 1 5% 36% 50% 5%	537
	11th to 20th	Night	8% 2 8% 36% 41% 5%	534
	21st to end	Night	5% 1 4 35% 49% 5%	594
September	1st to 10th	Night	9% 1 6% 34% 47% 3	540
	11th to 20th	Night	12% 1 7% 38% 39% 4	540
	21st to end	Night	10% 1 11% 39% 35% 4	540
October	1st to 10th	Night	7% 2 14% 41% 32% 3	713
	11th to 20th	Night	14% 4 24% 41% 17%	720
	21st to end	Night	21% 5% 22% 35% 17% 1	792
November	1st to 10th	Night	12% 5% 24% 43% 16% 1	740
	11th to 20th	Night	12% 6% 29% 40% 12% 1	785
	21st to end	Night	21% 7% 26% 34% 12%	950
December	1st to 10th	Night	19% 7% 28% 40% 7%	950
	11th to 20th	Night	21% 7% 26% 41% 5%	950
	21st to end	Night	18% 8% 32% 35% 6%	1045

Page generated at 2024-02-12 05:35:37. Version ac07

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