Siloam Springs
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Siloam Springs clear sky chart from 2005-11-06 to 2025-04-11.

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	12% 7% 2 6% 4 4 4 3 5% 7% 47%	113915
	Night	12% 7% 2 5% 3 3 3 3 4 6% 51%	114463
Transparency	Day	37% 3 11% 26% 19% 5%	117568
	Night	34% 3 10% 26% 21% 6%	118952
Seeing	Day	15% 9% 26% 27% 18% 5%	15939
	Night	15% 8% 28% 33% 15% 1	25947

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% 12% 4 6% 4 3 3 2 3 5% 44%	4077
	11th to 20th	Day	7% 6% 3 8% 4 4 3 3 4 6% 53%	4080
	21st to end	Day	21% 9% 2 5% 3 2 2 3 4 4 47%	4488
February	1st to 10th	Day	18% 10% 3 7% 5% 3 4 3 4 4 39%	1800
	11th to 20th	Day	16% 10% 3 6% 4 3 4 2 5% 6% 42%	1786
	21st to end	Day	17% 8% 2 5% 4 4 3 4 4 5% 43%	1778
March	1st to 10th	Day	13% 7% 2 5% 3 3 4 3 4 5% 48%	4936
	11th to 20th	Day	9% 6% 2 5% 3 4 4 4 5% 5% 54%	4980
	21st to end	Day	14% 8% 3 7% 5% 5% 5% 4 5% 7% 37%	5462
April	1st to 10th	Day	14% 7% 2 6% 4 5% 4 3 5% 7% 44%	2290
	11th to 20th	Day	16% 7% 2 6% 4 5% 4 4 4 5% 42%	2254
	21st to end	Day	18% 9% 3 7% 3 4 4 4 5% 5% 39%	2308
May	1st to 10th	Day	20% 7% 3 7% 5% 4 4 3 5% 5% 36%	4082
	11th to 20th	Day	13% 7% 3 8% 4 4 5% 4 6% 7% 41%	4082
	21st to end	Day	15% 6% 2 7% 6% 5% 5% 4 6% 8% 37%	4477
June	1st to 10th	Day	8% 5% 2 7% 4 5% 5% 4 8% 9% 45%	2470
	11th to 20th	Day	7% 5% 2 4 4 4 5% 4 7% 8% 49%	2470
	21st to end	Day	4 3 1 4 4 4 4 5% 6% 8% 56%	2470
July	1st to 10th	Day	9% 5% 2 5% 4 5% 5% 5% 8% 10% 43%	4120
	11th to 20th	Day	4 4 2 5% 4 4 5% 4 6% 10% 52%	4120
	21st to end	Day	7% 4 2 5% 4 5% 6% 5% 7% 11% 45%	4465
August	1st to 10th	Day	5% 3 2 4 3 3 4 3 6% 9% 58%	4104
	11th to 20th	Day	9% 5% 2 5% 4 5% 4 4 5% 8% 47%	4021
	21st to end	Day	4 4 2 5% 4 4 5% 4 5% 8% 56%	4180
September	1st to 10th	Day	12% 5% 2 4 3 3 3 3 5% 7% 53%	2277
	11th to 20th	Day	12% 5% 1 5% 3 5% 5% 4 6% 8% 46%	2090
	21st to end	Day	7% 4 2 5% 4 4 4 3 7% 7% 53%	2081
October	1st to 10th	Day	10% 4 2 5% 3 3 3 3 5% 6% 57%	1900
	11th to 20th	Day	13% 5% 1 4 2 2 2 2 3 6% 59%	1900
	21st to end	Day	17% 6% 2 6% 4 3 3 2 3 4 51%	2090
November	1st to 10th	Day	11% 6% 2 4 4 3 2 3 4 6% 56%	1958
	11th to 20th	Day	11% 7% 2 5% 3 3 3 3 4 5% 53%	1922
	21st to end	Day	16% 7% 3 5% 2 3 4 3 4 7% 48%	1800
December	1st to 10th	Day	12% 9% 3 5% 3 3 3 2 4 4 52%	2718
	11th to 20th	Day	12% 9% 2 7% 4 3 3 2 4 4 49%	3391
	21st to end	Day	20% 16% 6% 6% 3 3 4 3 4 4 31%	4488
January	1st to 10th	Night	14% 7% 4 8% 5% 3 3 3 4 6% 43%	5888
	11th to 20th	Night	8% 6% 2 6% 4 3 4 3 4 5% 54%	5900
	21st to end	Night	19% 9% 3 6% 2 2 2 2 3 4 46%	6490
February	1st to 10th	Night	16% 10% 2 6% 3 3 3 3 5% 5% 44%	2600
	11th to 20th	Night	15% 9% 2 6% 4 3 3 3 4 6% 46%	2518
	21st to end	Night	14% 8% 2 5% 4 3 4 3 5% 5% 46%	1850
March	1st to 10th	Night	16% 9% 2 6% 3 3 3 3 3 4 47%	4919
	11th to 20th	Night	10% 6% 2 5% 3 3 3 3 5% 6% 54%	4980
	21st to end	Night	11% 6% 2 6% 4 4 4 4 5% 8% 45%	5467
April	1st to 10th	Night	13% 6% 2 5% 3 4 3 3 4 6% 50%	2110
	11th to 20th	Night	13% 7% 2 5% 3 4 3 3 4 6% 49%	1881
	21st to end	Night	17% 7% 2 6% 3 4 4 3 5% 5% 46%	1867
May	1st to 10th	Night	13% 9% 2 6% 3 4 3 3 5% 7% 45%	2823
	11th to 20th	Night	13% 7% 2 6% 4 4 4 4 5% 7% 44%	2823
	21st to end	Night	14% 6% 2 5% 4 3 4 4 7% 9% 42%	3090
June	1st to 10th	Night	7% 4 1 5% 3 3 3 3 5% 9% 57%	1710
	11th to 20th	Night	4 3 1 3 4 3 3 4 7% 10% 57%	1710
	21st to end	Night	3 3 3 3 3 3 4 6% 8% 64%	1710
July	1st to 10th	Night	10% 4 2 4 4 3 4 4 5% 9% 52%	2850
	11th to 20th	Night	4 2 1 3 3 3 3 3 5% 8% 64%	2850
	21st to end	Night	5% 3 2 5% 4 3 4 4 7% 10% 53%	3098
August	1st to 10th	Night	3 2 1 3 3 3 4 3 6% 10% 61%	2836
	11th to 20th	Night	6% 4 2 5% 4 5% 4 4 5% 7% 54%	2815
	21st to end	Night	3 3 1 3 3 3 4 3 5% 8% 65%	3476
September	1st to 10th	Night	8% 4 1 4 3 4 3 3 5% 7% 58%	1900
	11th to 20th	Night	10% 4 2 6% 3 3 4 3 5% 6% 54%	2088
	21st to end	Night	8% 5% 1 4 3 3 3 2 5% 7% 58%	2090
October	1st to 10th	Night	7% 3 1 4 3 3 4 3 4 7% 62%	2270
	11th to 20th	Night	12% 4 1 3 3 3 3 2 4 5% 58%	2280
	21st to end	Night	17% 6% 2 4 3 3 3 2 3 5% 54%	2508
November	1st to 10th	Night	12% 6% 1 3 2 3 3 2 3 4 60%	2340
	11th to 20th	Night	10% 6% 2 4 2 3 3 3 4 5% 57%	2475
	21st to end	Night	14% 7% 2 4 3 2 2 3 4 5% 53%	2600
December	1st to 10th	Night	10% 10% 2 4 3 3 3 2 4 5% 54%	4345
	11th to 20th	Night	16% 8% 3 6% 3 3 3 2 3 4 50%	4816
	21st to end	Night	20% 12% 6% 7% 3 3 3 2 3 4 36%	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	46% 2 7% 26% 18% 2	4078
	11th to 20th	Day	35% 2 10% 26% 22% 5%	4080
	21st to end	Day	44% 1 6% 21% 21% 7%	4488
February	1st to 10th	Day	49% 3 8% 22% 14% 3	1800
	11th to 20th	Day	45% 2 9% 25% 17% 3	1795
	21st to end	Day	44% 2 6% 21% 18% 8%	1778
March	1st to 10th	Day	38% 3 6% 21% 16% 16%	4936
	11th to 20th	Day	32% 3 8% 20% 23% 14%	4980
	21st to end	Day	47% 3 10% 29% 10% 1	5464
April	1st to 10th	Day	40% 4 11% 23% 18% 4	2290
	11th to 20th	Day	44% 3 11% 21% 17% 3	2254
	21st to end	Day	48% 4 9% 23% 16% 1	2308
May	1st to 10th	Day	51% 3 8% 21% 15% 2	4120
	11th to 20th	Day	43% 3 13% 25% 16%	4086
	21st to end	Day	45% 4 14% 22% 14% 1	4489
June	1st to 10th	Day	34% 4 17% 28% 15% 2	2470
	11th to 20th	Day	31% 5% 15% 30% 17% 2	2470
	21st to end	Day	25% 5% 16% 31% 20% 4	2470
July	1st to 10th	Day	33% 6% 19% 27% 13% 2	4056
	11th to 20th	Day	26% 5% 12% 37% 18% 2	4051
	21st to end	Day	30% 7% 22% 30% 11%	4325
August	1st to 10th	Day	23% 4 16% 30% 22% 5%	4090
	11th to 20th	Day	34% 5% 16% 27% 16% 1	4060
	21st to end	Day	26% 5% 13% 40% 13% 3	4179
September	1st to 10th	Day	31% 4 10% 26% 20% 9%	2277
	11th to 20th	Day	34% 5% 10% 24% 23% 4	2090
	21st to end	Day	29% 4 10% 26% 27% 5%	2081
October	1st to 10th	Day	18% 2 6% 17% 39% 18%	3160
	11th to 20th	Day	18% 2 4 19% 41% 16%	3140
	21st to end	Day	28% 2 9% 30% 26% 6%	3428
November	1st to 10th	Day	30% 2 9% 28% 23% 8%	1958
	11th to 20th	Day	35% 2 6% 24% 21% 11%	1922
	21st to end	Day	38% 3 7% 23% 25% 4	1800
December	1st to 10th	Day	38% 2 7% 29% 23% 2	2718
	11th to 20th	Day	40% 2 4 27% 23% 3	3389
	21st to end	Day	58% 3 6% 20% 12% 2	4488
January	1st to 10th	Night	44% 2 10% 25% 15% 3	5888
	11th to 20th	Night	33% 2 11% 20% 31% 3	5900
	21st to end	Night	44% 2 7% 18% 25% 4	6490
February	1st to 10th	Night	43% 3 10% 24% 16% 4	2600
	11th to 20th	Night	42% 2 7% 26% 19% 4	2519
	21st to end	Night	41% 2 6% 20% 23% 7%	1850
March	1st to 10th	Night	43% 2 6% 19% 19% 11%	4919
	11th to 20th	Night	32% 2 8% 24% 22% 12%	4980
	21st to end	Night	39% 3 12% 30% 14% 2	5467
April	1st to 10th	Night	36% 2 10% 25% 19% 7%	2110
	11th to 20th	Night	37% 3 9% 24% 21% 7%	1881
	21st to end	Night	41% 3 10% 24% 19% 2	1867
May	1st to 10th	Night	40% 3 12% 24% 16% 4	2850
	11th to 20th	Night	41% 3 13% 27% 15% 1	2824
	21st to end	Night	38% 5% 16% 26% 15% 1	3099
June	1st to 10th	Night	25% 4 17% 32% 19% 3	1710
	11th to 20th	Night	21% 5% 15% 34% 23% 3	1710
	21st to end	Night	18% 5% 17% 31% 23% 6%	1710
July	1st to 10th	Night	30% 5% 19% 25% 16% 5%	2805
	11th to 20th	Night	17% 5% 11% 41% 24% 2	2796
	21st to end	Night	24% 6% 20% 35% 14% 1	2999
August	1st to 10th	Night	18% 5% 15% 34% 26% 2	2826
	11th to 20th	Night	29% 6% 18% 27% 18% 2	2842
	21st to end	Night	19% 3 11% 41% 22% 3	3476
September	1st to 10th	Night	26% 4 9% 30% 22% 10%	1900
	11th to 20th	Night	31% 3 10% 25% 26% 5%	2088
	21st to end	Night	27% 2 8% 26% 31% 6%	2090
October	1st to 10th	Night	14% 2 7% 14% 38% 25%	3790
	11th to 20th	Night	20% 2 4 19% 35% 20%	3779
	21st to end	Night	29% 3 7% 30% 24% 7%	4120
November	1st to 10th	Night	29% 2 8% 25% 27% 9%	2340
	11th to 20th	Night	30% 3 7% 25% 26% 9%	2475
	21st to end	Night	35% 2 8% 22% 26% 6%	2600
December	1st to 10th	Night	35% 2 8% 34% 19% 2	4345
	11th to 20th	Night	41% 2 4 24% 23% 6%	4817
	21st to end	Night	54% 2 7% 21% 12% 3	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	24% 14% 40% 17% 6%	300
	11th to 20th	Day	19% 22% 40% 17% 1 1	300
	21st to end	Day	18% 18% 42% 17% 5%	330
February	1st to 10th	Day	28% 16% 37% 16% 3	300
	11th to 20th	Day	26% 22% 36% 14% 2	300
	21st to end	Day	29% 20% 34% 14% 3	249
March	1st to 10th	Day	23% 18% 36% 20% 3	300
	11th to 20th	Day	26% 20% 34% 16% 4	300
	21st to end	Day	28% 16% 40% 11% 4 1	330
April	1st to 10th	Day	22% 20% 33% 18% 5% 2	390
	11th to 20th	Day	24% 15% 35% 19% 7% 1	452
	21st to end	Day	24% 14% 34% 18% 8% 1	488
May	1st to 10th	Day	19% 11% 36% 27% 7%	653
	11th to 20th	Day	16% 8% 30% 30% 13% 3	675
	21st to end	Day	12% 6% 32% 27% 16% 7%	734
June	1st to 10th	Day	10% 3 18% 34% 27% 8%	680
	11th to 20th	Day	8% 3 16% 39% 27% 7%	680
	21st to end	Day	4 2 21% 39% 28% 6%	680
July	1st to 10th	Day	9% 2 13% 30% 32% 13%	671
	11th to 20th	Day	6% 1 12% 35% 35% 10%	668
	21st to end	Day	8% 2 8% 31% 35% 16%	739
August	1st to 10th	Day	9% 1 10% 38% 33% 9%	676
	11th to 20th	Day	11% 2 10% 34% 35% 9%	658
	21st to end	Day	7% 2 7% 32% 41% 12%	539
September	1st to 10th	Day	11% 2 9% 33% 34% 11%	487
	11th to 20th	Day	7% 16% 43% 23% 11%	300
	21st to end	Day	9% 5% 22% 30% 23% 10%	300
October	1st to 10th	Day	10% 6% 29% 28% 21% 6%	300
	11th to 20th	Day	14% 11% 34% 29% 11% 1	300
	21st to end	Day	24% 15% 31% 22% 7% 2	330
November	1st to 10th	Day	15% 10% 42% 24% 7% 2	300
	11th to 20th	Day	18% 15% 36% 22% 8% 1	300
	21st to end	Day	22% 16% 33% 21% 7%	300
December	1st to 10th	Day	20% 13% 44% 16% 6% 2	300
	11th to 20th	Day	23% 14% 40% 17% 6% 1	300
	21st to end	Day	27% 18% 39% 13% 4	330
January	1st to 10th	Night	18% 14% 33% 30% 5%	1000
	11th to 20th	Night	19% 15% 38% 23% 5%	1000
	21st to end	Night	16% 12% 38% 29% 4	1100
February	1st to 10th	Night	21% 14% 38% 25% 4	1000
	11th to 20th	Night	21% 16% 39% 22% 3	964
	21st to end	Night	22% 14% 38% 25% 3	530
March	1st to 10th	Night	20% 11% 37% 28% 5%	600
	11th to 20th	Night	21% 10% 34% 31% 5%	600
	21st to end	Night	18% 12% 40% 24% 6%	660
April	1st to 10th	Night	18% 11% 39% 28% 5%	600
	11th to 20th	Night	17% 10% 35% 29% 8%	565
	21st to end	Night	22% 6% 40% 23% 9% 1	570
May	1st to 10th	Night	16% 6% 29% 39% 10%	570
	11th to 20th	Night	16% 3 23% 39% 17% 1	561
	21st to end	Night	13% 4 27% 32% 21% 2	617
June	1st to 10th	Night	8% 4 12% 41% 33% 1	570
	11th to 20th	Night	5% 1 20% 47% 26% 1	570
	21st to end	Night	3 1 17% 46% 30% 3	570
July	1st to 10th	Night	7% 2 8% 39% 38% 5%	555
	11th to 20th	Night	4 9% 41% 40% 6%	552
	21st to end	Night	5% 2 7% 39% 43% 5%	624
August	1st to 10th	Night	4 1 8% 45% 38% 4	567
	11th to 20th	Night	9% 1 7% 47% 32% 4	564
	21st to end	Night	4 1 7% 39% 43% 5%	627
September	1st to 10th	Night	10% 1 10% 41% 35% 2	570
	11th to 20th	Night	12% 1 11% 43% 30% 4	570
	21st to end	Night	11% 2 19% 38% 27% 3	570
October	1st to 10th	Night	8% 2 23% 38% 25% 4	750
	11th to 20th	Night	14% 6% 30% 38% 12%	760
	21st to end	Night	22% 7% 28% 33% 10% 1	836
November	1st to 10th	Night	14% 7% 36% 31% 12%	780
	11th to 20th	Night	15% 10% 36% 31% 8%	875
	21st to end	Night	19% 10% 34% 28% 9%	1000
December	1st to 10th	Night	18% 12% 34% 30% 5%	1000
	11th to 20th	Night	22% 11% 34% 28% 5%	1000
	21st to end	Night	21% 13% 35% 27% 4	1100

Page generated at 2025-04-08 08:17:27. Version ac07

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