Sioux City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sioux City clear sky chart from 2005-11-06 to 2026-01-02.

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% 3 7% 5% 4 4 3 5% 7% 43%	127886
	Night	10% 7% 3 7% 4 4 4 3 5% 7% 45%	123715
Transparency	Day	40% 6% 13% 25% 15% 2	131493
	Night	37% 5% 13% 26% 16% 2	128173
Seeing	Day	15% 10% 31% 28% 12% 2	17448
	Night	14% 10% 34% 33% 10% 1	27389

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	10% 12% 5% 16% 9% 7% 5% 4 4 5% 23%	4021
	11th to 20th	Day	6% 11% 4 10% 7% 6% 6% 3 6% 8% 32%	4080
	21st to end	Day	6% 11% 5% 13% 6% 5% 5% 3 6% 6% 35%	4488
February	1st to 10th	Day	10% 11% 4 12% 8% 6% 6% 3 6% 6% 27%	1800
	11th to 20th	Day	9% 12% 4 8% 5% 4 4 4 5% 6% 40%	1774
	21st to end	Day	12% 9% 3 8% 6% 5% 5% 3 6% 6% 37%	1650
March	1st to 10th	Day	12% 9% 3 7% 4 3 3 2 4 5% 49%	4808
	11th to 20th	Day	11% 8% 2 5% 3 3 3 2 4 7% 50%	4980
	21st to end	Day	22% 11% 5% 10% 5% 5% 4 3 5% 6% 25%	5462
April	1st to 10th	Day	15% 8% 3 7% 4 4 4 4 5% 6% 38%	2261
	11th to 20th	Day	18% 9% 3 6% 4 3 3 3 5% 6% 39%	2537
	21st to end	Day	21% 8% 3 6% 4 4 4 4 4 5% 37%	2600
May	1st to 10th	Day	13% 6% 2 6% 4 4 4 4 5% 7% 44%	5862
	11th to 20th	Day	15% 6% 2 5% 3 3 3 2 4 6% 52%	5862
	21st to end	Day	18% 8% 3 7% 5% 4 4 4 5% 7% 36%	6833
June	1st to 10th	Day	10% 5% 2 5% 4 4 4 3 6% 9% 48%	2800
	11th to 20th	Day	11% 5% 2 5% 4 4 5% 4 6% 8% 46%	2930
	21st to end	Day	9% 5% 2 6% 4 4 4 4 5% 9% 48%	3000
July	1st to 10th	Day	9% 5% 2 6% 4 4 5% 4 6% 9% 46%	6668
	11th to 20th	Day	9% 5% 2 6% 3 4 4 3 5% 7% 53%	5910
	21st to end	Day	6% 4 2 5% 4 4 5% 4 7% 10% 49%	6422
August	1st to 10th	Day	9% 6% 2 6% 4 4 5% 4 7% 8% 46%	4234
	11th to 20th	Day	17% 7% 2 6% 4 4 4 4 5% 7% 41%	4171
	21st to end	Day	9% 5% 2 6% 4 3 4 3 5% 7% 51%	4647
September	1st to 10th	Day	14% 5% 2 4 3 3 3 3 4 6% 53%	2325
	11th to 20th	Day	10% 5% 2 5% 3 3 4 3 5% 7% 53%	2200
	21st to end	Day	10% 4 1 5% 3 3 3 4 5% 5% 56%	2200
October	1st to 10th	Day	14% 6% 2 5% 4 3 4 3 4 6% 51%	2050
	11th to 20th	Day	14% 6% 2 4 3 2 3 3 4 5% 55%	2000
	21st to end	Day	15% 7% 2 6% 4 3 4 2 4 5% 47%	2167
November	1st to 10th	Day	11% 7% 3 5% 3 3 3 4 5% 7% 49%	1853
	11th to 20th	Day	9% 9% 2 9% 5% 4 3 3 5% 7% 45%	1763
	21st to end	Day	13% 10% 3 6% 4 3 4 3 5% 7% 42%	1680
December	1st to 10th	Day	5% 6% 4 9% 6% 5% 4 3 5% 7% 45%	2690
	11th to 20th	Day	9% 12% 4 9% 6% 6% 5% 4 6% 5% 33%	3088
	21st to end	Day	16% 10% 4 15% 6% 4 4 3 4 6% 28%	4070
January	1st to 10th	Night	10% 12% 3 16% 9% 6% 5% 4 5% 6% 24%	5949
	11th to 20th	Night	5% 9% 3 9% 6% 5% 6% 5% 8% 5% 37%	5900
	21st to end	Night	5% 11% 5% 11% 5% 4 4 5% 6% 7% 37%	6490
February	1st to 10th	Night	10% 10% 3 10% 6% 4 5% 3 4 6% 38%	2600
	11th to 20th	Night	9% 11% 5% 7% 5% 4 4 3 5% 6% 41%	2531
	21st to end	Night	9% 8% 3 7% 4 4 4 4 5% 5% 46%	1980
March	1st to 10th	Night	14% 6% 3 4 3 3 3 3 4 6% 53%	5038
	11th to 20th	Night	11% 6% 2 5% 3 3 3 3 5% 8% 51%	4980
	21st to end	Night	18% 9% 3 8% 4 4 4 4 5% 7% 34%	5467
April	1st to 10th	Night	15% 7% 2 6% 4 4 4 4 5% 5% 43%	2138
	11th to 20th	Night	13% 7% 3 6% 4 4 3 3 5% 7% 44%	1811
	21st to end	Night	17% 7% 3 6% 5% 3 4 4 4 5% 41%	1800
May	1st to 10th	Night	13% 5% 2 4 3 3 4 3 4 6% 51%	4053
	11th to 20th	Night	13% 5% 2 4 3 3 3 3 5% 5% 55%	4053
	21st to end	Night	18% 7% 2 6% 3 3 3 3 4 7% 43%	4042
June	1st to 10th	Night	8% 3 2 4 4 3 4 4 6% 9% 54%	1600
	11th to 20th	Night	7% 5% 2 4 4 4 4 4 5% 9% 53%	1463
	21st to end	Night	7% 4 2 5% 4 4 3 3 5% 8% 57%	1400
July	1st to 10th	Night	8% 4 2 5% 4 4 4 3 5% 8% 53%	3306
	11th to 20th	Night	9% 4 1 4 3 3 3 3 5% 8% 57%	4050
	21st to end	Night	4 3 2 4 3 4 4 3 6% 11% 55%	4449
August	1st to 10th	Night	6% 4 2 5% 3 3 5% 4 6% 9% 53%	2926
	11th to 20th	Night	12% 6% 1 4 3 3 3 3 5% 7% 52%	2888
	21st to end	Night	7% 4 2 5% 3 4 4 4 5% 8% 54%	3261
September	1st to 10th	Night	9% 3 2 5% 3 3 3 2 5% 6% 60%	2071
	11th to 20th	Night	9% 4 1 4 3 3 5% 3 5% 6% 56%	2200
	21st to end	Night	9% 4 2 5% 2 3 3 3 4 6% 60%	2200
October	1st to 10th	Night	14% 5% 2 5% 3 3 3 3 5% 6% 52%	2329
	11th to 20th	Night	14% 6% 2 5% 3 3 3 2 3 5% 53%	2400
	21st to end	Night	15% 7% 2 6% 3 3 3 2 4 6% 49%	2670
November	1st to 10th	Night	8% 6% 2 5% 4 3 4 3 5% 8% 53%	2665
	11th to 20th	Night	10% 7% 2 7% 4 4 4 3 5% 7% 48%	2856
	21st to end	Night	10% 8% 3 6% 4 4 3 3 5% 6% 48%	2940
December	1st to 10th	Night	5% 7% 4 10% 6% 5% 4 4 5% 7% 45%	4720
	11th to 20th	Night	10% 9% 4 9% 5% 6% 5% 4 6% 6% 36%	5339
	21st to end	Night	16% 13% 4 11% 6% 4 4 3 4 5% 29%	7150

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	62% 6% 12% 16% 5%	4022
	11th to 20th	Day	49% 4 12% 19% 15% 1	4080
	21st to end	Day	48% 6% 14% 21% 9% 2	4488
February	1st to 10th	Day	56% 6% 14% 15% 10% 1	1800
	11th to 20th	Day	46% 4 13% 21% 13% 2	1783
	21st to end	Day	46% 7% 11% 21% 12% 2	1650
March	1st to 10th	Day	40% 3 9% 30% 16% 2	4808
	11th to 20th	Day	36% 4 8% 31% 19% 3	4980
	21st to end	Day	60% 6% 13% 16% 4 2	5464
April	1st to 10th	Day	44% 6% 13% 24% 12% 1	2261
	11th to 20th	Day	46% 5% 11% 22% 13% 2	2537
	21st to end	Day	48% 6% 10% 23% 13%	2600
May	1st to 10th	Day	38% 6% 11% 25% 19% 1	5900
	11th to 20th	Day	35% 5% 10% 24% 20% 6%	5866
	21st to end	Day	47% 6% 10% 22% 14% 1	6847
June	1st to 10th	Day	32% 7% 16% 29% 14% 2	2800
	11th to 20th	Day	35% 7% 13% 27% 16% 3	2930
	21st to end	Day	32% 7% 14% 29% 14% 3	3000
July	1st to 10th	Day	34% 6% 16% 31% 12% 1	6596
	11th to 20th	Day	30% 6% 13% 32% 17% 2	5840
	21st to end	Day	28% 8% 19% 27% 16% 2	6240
August	1st to 10th	Day	34% 7% 14% 29% 15% 1	4220
	11th to 20th	Day	42% 6% 12% 28% 11% 1	4210
	21st to end	Day	32% 6% 15% 25% 19% 3	4646
September	1st to 10th	Day	33% 6% 10% 30% 19% 2	2325
	11th to 20th	Day	31% 6% 14% 31% 17% 2	2200
	21st to end	Day	29% 6% 11% 30% 22% 2	2200
October	1st to 10th	Day	22% 3 6% 27% 38% 3	3336
	11th to 20th	Day	25% 4 16% 27% 22% 5%	3240
	21st to end	Day	37% 4 11% 27% 17% 3	3483
November	1st to 10th	Day	35% 5% 16% 26% 17% 2	1853
	11th to 20th	Day	39% 6% 15% 25% 15% 1	1763
	21st to end	Day	42% 4 15% 25% 13% 1	1680
December	1st to 10th	Day	38% 5% 16% 29% 11% 1	2690
	11th to 20th	Day	50% 6% 16% 20% 8%	3085
	21st to end	Day	57% 5% 13% 19% 6%	4070
January	1st to 10th	Night	60% 6% 11% 14% 8%	5949
	11th to 20th	Night	44% 5% 15% 19% 16% 2	5900
	21st to end	Night	43% 7% 12% 23% 15%	6490
February	1st to 10th	Night	48% 5% 11% 24% 11% 1	2600
	11th to 20th	Night	43% 6% 13% 22% 13% 3	2532
	21st to end	Night	37% 5% 14% 24% 16% 3	1980
March	1st to 10th	Night	34% 3 8% 32% 21% 1	5038
	11th to 20th	Night	32% 3 8% 30% 22% 4	4980
	21st to end	Night	48% 9% 15% 21% 5% 2	5467
April	1st to 10th	Night	41% 7% 11% 24% 15% 1	2138
	11th to 20th	Night	41% 4 10% 25% 18% 2	1811
	21st to end	Night	44% 6% 12% 23% 13% 2	1800
May	1st to 10th	Night	32% 6% 11% 26% 24% 1	4080
	11th to 20th	Night	31% 5% 12% 19% 24% 9%	4054
	21st to end	Night	41% 5% 11% 26% 14% 2	4050
June	1st to 10th	Night	26% 7% 14% 33% 15% 4	1600
	11th to 20th	Night	29% 6% 14% 27% 21% 4	1463
	21st to end	Night	26% 6% 16% 30% 20% 3	1400
July	1st to 10th	Night	30% 6% 16% 32% 15% 2	3271
	11th to 20th	Night	26% 4 14% 36% 16% 3	4000
	21st to end	Night	23% 7% 21% 31% 16% 2	4320
August	1st to 10th	Night	28% 6% 16% 31% 16% 3	2916
	11th to 20th	Night	32% 6% 15% 30% 15% 2	2915
	21st to end	Night	28% 7% 15% 24% 22% 5%	3261
September	1st to 10th	Night	27% 5% 11% 30% 22% 5%	2071
	11th to 20th	Night	26% 7% 13% 33% 20% 2	2200
	21st to end	Night	26% 4 10% 33% 24% 4	2200
October	1st to 10th	Night	21% 3 6% 21% 46% 3	3810
	11th to 20th	Night	27% 3 10% 30% 26% 4	3899
	21st to end	Night	37% 3 10% 32% 17% 1	4306
November	1st to 10th	Night	30% 4 16% 26% 21% 3	2665
	11th to 20th	Night	36% 5% 14% 26% 17% 2	2856
	21st to end	Night	38% 5% 13% 29% 15% 1	2940
December	1st to 10th	Night	39% 5% 13% 32% 11%	4720
	11th to 20th	Night	47% 5% 16% 25% 7%	5341
	21st to end	Night	57% 5% 11% 21% 7%	7150

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	17% 15% 31% 26% 10%	303
	11th to 20th	Day	18% 13% 36% 28% 5% 1	300
	21st to end	Day	16% 9% 42% 23% 9% 1	330
February	1st to 10th	Day	15% 15% 41% 25% 4	300
	11th to 20th	Day	15% 14% 41% 24% 5% 1	300
	21st to end	Day	19% 12% 44% 20% 4	249
March	1st to 10th	Day	15% 16% 45% 20% 3 1	300
	11th to 20th	Day	25% 12% 37% 17% 8%	300
	21st to end	Day	31% 13% 37% 15% 3 1	330
April	1st to 10th	Day	22% 15% 39% 20% 3 1	361
	11th to 20th	Day	23% 17% 32% 21% 6%	655
	21st to end	Day	27% 13% 30% 21% 7% 2	700
May	1st to 10th	Day	22% 12% 30% 23% 11% 2	703
	11th to 20th	Day	20% 11% 29% 25% 12% 3	725
	21st to end	Day	20% 8% 30% 26% 12% 3	789
June	1st to 10th	Day	8% 9% 24% 35% 19% 4	730
	11th to 20th	Day	11% 7% 35% 32% 14% 2	730
	21st to end	Day	11% 9% 33% 31% 15% 2	730
July	1st to 10th	Day	8% 3 21% 37% 24% 7%	721
	11th to 20th	Day	8% 5% 24% 39% 19% 5%	718
	21st to end	Day	5% 3 27% 40% 22% 4	794
August	1st to 10th	Day	11% 5% 22% 36% 23% 4	726
	11th to 20th	Day	11% 5% 24% 35% 21% 4	715
	21st to end	Day	9% 4 27% 37% 19% 4	788
September	1st to 10th	Day	17% 6% 25% 34% 15% 4	455
	11th to 20th	Day	8% 4 37% 32% 15% 4	330
	21st to end	Day	13% 10% 31% 28% 14% 4	330
October	1st to 10th	Day	17% 12% 30% 25% 12% 4	330
	11th to 20th	Day	16% 16% 39% 21% 7% 1	330
	21st to end	Day	19% 16% 37% 23% 5%	363
November	1st to 10th	Day	18% 16% 34% 23% 6% 2	330
	11th to 20th	Day	16% 20% 39% 22% 4	330
	21st to end	Day	23% 17% 27% 22% 11% 1	330
December	1st to 10th	Day	12% 13% 41% 25% 8% 1	330
	11th to 20th	Day	15% 18% 37% 25% 4	330
	21st to end	Day	23% 12% 39% 23% 3 1	363
January	1st to 10th	Night	13% 12% 37% 31% 7%	1006
	11th to 20th	Night	14% 13% 37% 29% 6% 1	1000
	21st to end	Night	15% 10% 41% 27% 7%	1100
February	1st to 10th	Night	15% 13% 39% 28% 5% 1	1000
	11th to 20th	Night	14% 12% 42% 25% 6% 1	977
	21st to end	Night	14% 9% 41% 29% 6%	660
March	1st to 10th	Night	15% 10% 39% 30% 6%	658
	11th to 20th	Night	19% 10% 37% 29% 5%	600
	21st to end	Night	21% 12% 37% 25% 5%	660
April	1st to 10th	Night	19% 15% 38% 26% 3	600
	11th to 20th	Night	19% 16% 37% 24% 4 1	593
	21st to end	Night	19% 13% 34% 27% 7% 1	600
May	1st to 10th	Night	17% 9% 32% 32% 9%	600
	11th to 20th	Night	16% 10% 29% 34% 10% 1	591
	21st to end	Night	18% 6% 30% 35% 10% 1	650
June	1st to 10th	Night	8% 5% 26% 47% 14%	600
	11th to 20th	Night	8% 5% 34% 40% 13%	600
	21st to end	Night	8% 4 30% 45% 13%	600
July	1st to 10th	Night	7% 3 19% 44% 27% 1	585
	11th to 20th	Night	5% 2 24% 48% 20% 2	582
	21st to end	Night	3 2 19% 55% 20% 1	657
August	1st to 10th	Night	7% 4 22% 46% 20% 1	597
	11th to 20th	Night	9% 4 21% 44% 22% 1	594
	21st to end	Night	7% 3 26% 43% 18% 2	660
September	1st to 10th	Night	10% 6% 24% 41% 18% 1	600
	11th to 20th	Night	10% 4 33% 40% 13% 2	600
	21st to end	Night	10% 8% 32% 35% 14% 2	600
October	1st to 10th	Night	16% 8% 31% 32% 12% 1	729
	11th to 20th	Night	17% 13% 36% 29% 5%	800
	21st to end	Night	19% 14% 29% 29% 10%	910
November	1st to 10th	Night	10% 12% 37% 32% 7% 1	1025
	11th to 20th	Night	13% 12% 40% 28% 6%	1050
	21st to end	Night	15% 12% 36% 29% 8%	1050
December	1st to 10th	Night	13% 11% 39% 30% 6%	1050
	11th to 20th	Night	17% 10% 36% 31% 6%	1050
	21st to end	Night	20% 12% 36% 26% 5%	1155

Page generated at 2025-12-30 00:14:06. Version ac07

Copyright © 2025 Attilla Danko.