Omaha
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Omaha clear sky chart from 2005-11-06 to 2025-09-04.

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	11% 7% 3 7% 4 4 4 4 5% 7% 43%	125883
	Night	10% 7% 3 7% 4 4 4 3 5% 7% 47%	123103
Transparency	Day	38% 6% 13% 25% 16% 2	129508
	Night	36% 6% 12% 25% 18% 3	127541
Seeing	Day	15% 10% 31% 29% 14% 3	17008
	Night	13% 9% 33% 34% 10% 1	26790

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	9% 11% 6% 16% 7% 5% 4 4 5% 6% 26%	4077
	11th to 20th	Day	7% 9% 4 10% 5% 5% 7% 4 5% 6% 37%	4080
	21st to end	Day	7% 12% 5% 12% 6% 5% 5% 4 5% 6% 34%	4488
February	1st to 10th	Day	9% 13% 4 10% 7% 6% 4 4 5% 7% 31%	1800
	11th to 20th	Day	9% 11% 4 9% 5% 4 4 4 5% 8% 37%	1770
	21st to end	Day	10% 8% 4 8% 4 4 4 4 6% 6% 42%	1650
March	1st to 10th	Day	14% 9% 3 5% 3 2 3 2 3 4 51%	4891
	11th to 20th	Day	12% 7% 2 5% 4 4 3 3 4 8% 49%	4980
	21st to end	Day	18% 12% 3 9% 5% 4 4 3 6% 7% 28%	5462
April	1st to 10th	Day	16% 8% 3 6% 4 3 3 3 4 7% 43%	2270
	11th to 20th	Day	16% 9% 2 6% 4 4 4 4 5% 6% 40%	2475
	21st to end	Day	20% 7% 2 7% 4 3 5% 4 5% 7% 37%	2600
May	1st to 10th	Day	12% 8% 3 7% 4 3 4 3 5% 7% 44%	5862
	11th to 20th	Day	15% 6% 2 5% 4 3 3 2 4 6% 50%	5862
	21st to end	Day	16% 7% 3 7% 4 4 4 4 6% 8% 36%	6703
June	1st to 10th	Day	8% 5% 2 5% 4 5% 5% 4 6% 9% 47%	2800
	11th to 20th	Day	9% 5% 2 5% 5% 3 4 4 7% 9% 47%	2800
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 8% 49%	2800
July	1st to 10th	Day	10% 5% 2 6% 4 4 4 4 7% 9% 45%	6066
	11th to 20th	Day	7% 5% 2 6% 5% 4 5% 4 6% 8% 48%	5900
	21st to end	Day	6% 4 2 5% 4 4 4 5% 7% 10% 50%	6422
August	1st to 10th	Day	6% 5% 2 6% 4 5% 6% 5% 7% 10% 45%	4234
	11th to 20th	Day	13% 6% 2 6% 5% 4 4 4 5% 8% 42%	4171
	21st to end	Day	7% 5% 2 6% 5% 4 5% 3 6% 8% 49%	4581
September	1st to 10th	Day	12% 5% 1 4 3 3 3 3 4 7% 54%	2261
	11th to 20th	Day	9% 6% 1 5% 3 3 3 3 5% 7% 53%	2090
	21st to end	Day	11% 4 2 5% 2 4 4 3 5% 5% 56%	2090
October	1st to 10th	Day	14% 5% 2 4 3 3 4 4 4 6% 52%	1933
	11th to 20th	Day	12% 6% 2 4 3 3 3 2 4 5% 56%	1900
	21st to end	Day	13% 7% 2 6% 4 4 3 3 5% 5% 47%	2090
November	1st to 10th	Day	11% 6% 2 5% 3 3 3 2 5% 6% 53%	1796
	11th to 20th	Day	10% 8% 2 8% 5% 4 4 4 3 6% 45%	1710
	21st to end	Day	13% 9% 4 5% 4 3 3 3 6% 8% 42%	1600
December	1st to 10th	Day	5% 6% 2 7% 5% 5% 5% 3 4 6% 51%	2610
	11th to 20th	Day	10% 10% 3 9% 5% 4 4 3 5% 6% 41%	3008
	21st to end	Day	17% 10% 5% 15% 5% 4 4 3 4 6% 28%	4051
January	1st to 10th	Night	9% 10% 5% 21% 9% 5% 4 3 5% 5% 24%	5888
	11th to 20th	Night	7% 9% 4 8% 5% 5% 7% 4 7% 6% 38%	5900
	21st to end	Night	9% 11% 5% 11% 5% 4 4 3 4 6% 38%	6490
February	1st to 10th	Night	11% 10% 4 10% 5% 5% 4 3 5% 7% 37%	2600
	11th to 20th	Night	9% 10% 4 7% 4 5% 4 4 6% 7% 41%	2533
	21st to end	Night	8% 7% 4 7% 4 4 4 3 5% 5% 49%	1980
March	1st to 10th	Night	14% 7% 2 4 3 3 3 3 4 5% 51%	4965
	11th to 20th	Night	10% 7% 2 5% 2 3 3 3 5% 6% 56%	4980
	21st to end	Night	14% 10% 3 8% 4 4 4 4 5% 8% 35%	5467
April	1st to 10th	Night	13% 8% 2 6% 3 3 4 4 5% 6% 46%	2130
	11th to 20th	Night	11% 8% 2 6% 4 4 4 3 4 6% 47%	1872
	21st to end	Night	16% 8% 2 6% 3 4 3 3 4 7% 44%	1800
May	1st to 10th	Night	14% 6% 2 5% 3 3 4 3 5% 6% 49%	4053
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 5% 7% 52%	4053
	21st to end	Night	17% 8% 2 6% 4 3 4 3 5% 6% 42%	4169
June	1st to 10th	Night	5% 4 1 5% 3 3 5% 4 6% 8% 54%	1600
	11th to 20th	Night	7% 4 2 4 3 3 5% 5% 8% 10% 50%	1600
	21st to end	Night	5% 3 2 4 3 5% 5% 4 5% 8% 56%	1600
July	1st to 10th	Night	6% 5% 2 5% 4 4 4 4 6% 8% 52%	3893
	11th to 20th	Night	6% 4 2 5% 3 4 4 3 6% 9% 55%	4077
	21st to end	Night	5% 3 1 5% 4 4 5% 4 6% 9% 53%	4449
August	1st to 10th	Night	4 3 2 5% 3 3 4 3 7% 10% 57%	2926
	11th to 20th	Night	10% 5% 2 5% 4 4 4 3 5% 7% 51%	2888
	21st to end	Night	7% 4 1 4 3 3 4 4 6% 8% 56%	3325
September	1st to 10th	Night	9% 3 1 4 3 3 3 3 4 7% 59%	1982
	11th to 20th	Night	9% 4 1 3 3 3 3 3 6% 7% 58%	2090
	21st to end	Night	10% 5% 2 4 2 3 3 3 4 6% 60%	2090
October	1st to 10th	Night	13% 5% 1 4 3 3 4 3 4 7% 53%	2226
	11th to 20th	Night	13% 6% 2 4 4 2 3 3 4 5% 55%	2280
	21st to end	Night	13% 7% 2 5% 3 4 3 3 5% 5% 51%	2508
November	1st to 10th	Night	10% 5% 2 4 2 3 4 3 5% 6% 55%	2499
	11th to 20th	Night	10% 6% 2 6% 4 3 3 3 5% 6% 52%	2688
	21st to end	Night	11% 8% 3 5% 4 3 3 2 5% 6% 50%	2800
December	1st to 10th	Night	5% 7% 2 6% 4 4 5% 3 6% 7% 51%	4580
	11th to 20th	Night	10% 8% 3 8% 4 4 4 4 5% 7% 43%	5199
	21st to end	Night	18% 13% 5% 10% 4 4 3 3 4 5% 32%	6923

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	57% 5% 12% 19% 6%	4078
	11th to 20th	Day	46% 6% 12% 20% 15% 2	4080
	21st to end	Day	49% 6% 13% 21% 10%	4488
February	1st to 10th	Day	52% 7% 14% 17% 10% 1	1800
	11th to 20th	Day	45% 5% 11% 23% 13% 2	1779
	21st to end	Day	41% 7% 11% 23% 15% 3	1650
March	1st to 10th	Day	39% 4 7% 27% 18% 5%	4891
	11th to 20th	Day	35% 5% 9% 27% 22% 3	4980
	21st to end	Day	53% 8% 19% 14% 4 2	5464
April	1st to 10th	Day	42% 5% 12% 27% 13% 1	2270
	11th to 20th	Day	42% 7% 13% 22% 12% 3	2475
	21st to end	Day	46% 8% 11% 23% 12% 1	2600
May	1st to 10th	Day	38% 8% 12% 26% 15% 1	5900
	11th to 20th	Day	36% 5% 9% 24% 23% 3	5866
	21st to end	Day	43% 9% 11% 22% 14% 1	6717
June	1st to 10th	Day	31% 9% 16% 28% 13% 3	2800
	11th to 20th	Day	31% 8% 14% 30% 15% 1	2800
	21st to end	Day	32% 8% 15% 27% 14% 4	2800
July	1st to 10th	Day	34% 6% 14% 32% 13% 1	6002
	11th to 20th	Day	33% 7% 13% 29% 16% 2	5831
	21st to end	Day	27% 8% 20% 29% 15% 1	6240
August	1st to 10th	Day	31% 8% 15% 28% 16% 1	4220
	11th to 20th	Day	39% 7% 13% 26% 14% 1	4210
	21st to end	Day	32% 7% 15% 26% 16% 4	4580
September	1st to 10th	Day	30% 6% 12% 29% 18% 5%	2261
	11th to 20th	Day	30% 6% 12% 33% 18% 1	2090
	21st to end	Day	29% 5% 10% 31% 24% 1	2090
October	1st to 10th	Day	20% 3 7% 21% 46% 2	3206
	11th to 20th	Day	21% 3 12% 30% 26% 7%	3140
	21st to end	Day	36% 4 10% 27% 20% 3	3428
November	1st to 10th	Day	33% 4 15% 27% 19% 2	1796
	11th to 20th	Day	39% 6% 12% 24% 17% 1	1710
	21st to end	Day	41% 4 13% 29% 12% 1	1600
December	1st to 10th	Day	34% 5% 18% 28% 15% 1	2610
	11th to 20th	Day	44% 5% 18% 23% 9%	3005
	21st to end	Day	58% 5% 12% 19% 6%	4051
January	1st to 10th	Night	61% 6% 10% 14% 9%	5888
	11th to 20th	Night	43% 5% 14% 20% 15% 2	5900
	21st to end	Night	47% 6% 13% 18% 14% 2	6490
February	1st to 10th	Night	47% 6% 13% 20% 12% 2	2600
	11th to 20th	Night	41% 7% 13% 22% 15% 3	2534
	21st to end	Night	36% 5% 10% 24% 21% 4	1980
March	1st to 10th	Night	35% 5% 7% 29% 22% 3	4965
	11th to 20th	Night	30% 5% 6% 29% 24% 6%	4980
	21st to end	Night	46% 8% 18% 22% 5% 1	5467
April	1st to 10th	Night	37% 7% 10% 26% 17% 3	2130
	11th to 20th	Night	38% 5% 11% 25% 18% 3	1872
	21st to end	Night	40% 7% 13% 23% 15% 2	1800
May	1st to 10th	Night	35% 6% 11% 26% 21% 2	4080
	11th to 20th	Night	31% 7% 10% 21% 26% 5%	4054
	21st to end	Night	42% 7% 12% 22% 16% 2	4177
June	1st to 10th	Night	25% 9% 15% 33% 15% 4	1600
	11th to 20th	Night	26% 9% 15% 26% 20% 5%	1600
	21st to end	Night	25% 6% 14% 31% 20% 3	1600
July	1st to 10th	Night	29% 6% 13% 32% 17% 3	3850
	11th to 20th	Night	27% 6% 14% 30% 21% 2	4026
	21st to end	Night	25% 8% 17% 29% 19% 1	4320
August	1st to 10th	Night	22% 7% 15% 34% 20% 2	2916
	11th to 20th	Night	33% 6% 13% 28% 19% 1	2915
	21st to end	Night	27% 6% 16% 26% 17% 8%	3325
September	1st to 10th	Night	26% 6% 12% 29% 23% 6%	1982
	11th to 20th	Night	25% 5% 13% 35% 20% 3	2090
	21st to end	Night	26% 5% 9% 29% 27% 4	2090
October	1st to 10th	Night	20% 4 7% 17% 49% 4	3720
	11th to 20th	Night	23% 3 8% 28% 30% 8%	3779
	21st to end	Night	34% 3 10% 29% 22% 1	4120
November	1st to 10th	Night	28% 5% 16% 24% 23% 4	2499
	11th to 20th	Night	33% 5% 12% 30% 18% 3	2688
	21st to end	Night	36% 4 12% 29% 17% 2	2800
December	1st to 10th	Night	33% 5% 13% 35% 14% 1	4580
	11th to 20th	Night	40% 6% 16% 28% 11%	5201
	21st to end	Night	56% 5% 11% 21% 7% 1	6923

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	19% 13% 36% 23% 8% 2	300
	11th to 20th	Day	21% 13% 37% 22% 6% 1	300
	21st to end	Day	14% 14% 43% 20% 7% 2	330
February	1st to 10th	Day	18% 16% 45% 18% 3	300
	11th to 20th	Day	19% 17% 37% 20% 5% 1	300
	21st to end	Day	15% 19% 39% 22% 5%	249
March	1st to 10th	Day	19% 14% 43% 19% 5%	300
	11th to 20th	Day	27% 11% 35% 20% 7% 1	300
	21st to end	Day	32% 17% 34% 15% 2 1	330
April	1st to 10th	Day	24% 17% 37% 18% 3	370
	11th to 20th	Day	21% 16% 36% 20% 7%	593
	21st to end	Day	23% 17% 31% 20% 7% 2	700
May	1st to 10th	Day	19% 13% 32% 25% 9% 2	703
	11th to 20th	Day	19% 10% 31% 26% 12% 2	725
	21st to end	Day	20% 8% 31% 26% 14% 2	789
June	1st to 10th	Day	8% 6% 23% 36% 23% 4	730
	11th to 20th	Day	10% 6% 30% 35% 16% 3	730
	21st to end	Day	9% 8% 33% 34% 13% 2	730
July	1st to 10th	Day	11% 4 16% 32% 28% 9%	721
	11th to 20th	Day	6% 4 29% 34% 21% 6%	718
	21st to end	Day	7% 2 20% 43% 25% 4	794
August	1st to 10th	Day	8% 2 22% 43% 21% 4	726
	11th to 20th	Day	8% 5% 19% 39% 25% 4	715
	21st to end	Day	10% 2 23% 40% 21% 5%	748
September	1st to 10th	Day	13% 4 27% 34% 19% 4	447
	11th to 20th	Day	7% 4 32% 35% 18% 5%	300
	21st to end	Day	14% 10% 30% 29% 14% 2	300
October	1st to 10th	Day	20% 6% 29% 26% 13% 5%	300
	11th to 20th	Day	12% 16% 41% 20% 8% 1	300
	21st to end	Day	19% 15% 37% 19% 9% 2	330
November	1st to 10th	Day	19% 11% 35% 25% 9% 1	300
	11th to 20th	Day	18% 15% 41% 20% 7%	300
	21st to end	Day	21% 14% 35% 22% 8% 1	300
December	1st to 10th	Day	9% 13% 42% 29% 5% 2	300
	11th to 20th	Day	15% 18% 33% 25% 8% 1	300
	21st to end	Day	21% 16% 39% 21% 3 1	330
January	1st to 10th	Night	12% 12% 36% 32% 7% 1	1000
	11th to 20th	Night	14% 14% 35% 30% 7%	1000
	21st to end	Night	17% 9% 39% 29% 6%	1100
February	1st to 10th	Night	15% 12% 40% 29% 4	1000
	11th to 20th	Night	13% 11% 42% 29% 4	979
	21st to end	Night	14% 11% 44% 25% 5%	660
March	1st to 10th	Night	14% 14% 38% 27% 6%	622
	11th to 20th	Night	19% 10% 37% 29% 7%	600
	21st to end	Night	21% 14% 38% 22% 4	660
April	1st to 10th	Night	15% 17% 41% 23% 4	600
	11th to 20th	Night	15% 15% 39% 27% 3 1	593
	21st to end	Night	19% 12% 34% 28% 7% 1	600
May	1st to 10th	Night	18% 10% 30% 34% 8%	600
	11th to 20th	Night	16% 9% 29% 34% 10% 1	591
	21st to end	Night	17% 7% 30% 32% 13%	650
June	1st to 10th	Night	7% 4 26% 47% 16%	600
	11th to 20th	Night	9% 4 31% 42% 14% 1	600
	21st to end	Night	5% 4 33% 45% 13% 1	600
July	1st to 10th	Night	7% 2 18% 45% 27% 2	585
	11th to 20th	Night	4 2 20% 49% 23% 1	582
	21st to end	Night	4 2 17% 53% 24% 1	657
August	1st to 10th	Night	6% 3 19% 49% 22% 2	597
	11th to 20th	Night	7% 3 18% 47% 24% 1	594
	21st to end	Night	9% 3 21% 42% 22% 3	660
September	1st to 10th	Night	9% 4 24% 41% 21% 2	579
	11th to 20th	Night	10% 2 30% 39% 17% 1	570
	21st to end	Night	12% 5% 32% 34% 16% 1	570
October	1st to 10th	Night	14% 7% 33% 32% 12% 2	706
	11th to 20th	Night	15% 11% 34% 33% 7%	760
	21st to end	Night	18% 11% 31% 31% 9%	836
November	1st to 10th	Night	12% 11% 32% 37% 9% 1	939
	11th to 20th	Night	14% 13% 37% 29% 6%	1000
	21st to end	Night	16% 11% 35% 29% 9%	1000
December	1st to 10th	Night	13% 12% 39% 31% 6%	1000
	11th to 20th	Night	17% 9% 35% 32% 6% 1	1000
	21st to end	Night	21% 12% 33% 30% 4	1100

Page generated at 2025-09-01 00:51:07. Version ac07

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