Nebraska Nature and Visitor Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nebraska Nature and Visitor Center clear sky chart from 2005-11-06 to 2025-07-21.

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% 6% 2 6% 4 4 4 3 5% 7% 50%	124375
	Night	8% 6% 2 6% 4 3 4 3 5% 7% 52%	123519
Transparency	Day	34% 4 13% 26% 19% 4	124132
	Night	32% 4 13% 27% 21% 4	123353
Seeing	Day	13% 9% 31% 30% 14% 3	16747
	Night	12% 9% 36% 34% 9% 1	26633

By Month

Percentage Cloud Cover SW (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% 13% 4 10% 6% 4 4 3 4 5% 38%	3638
	11th to 20th	Day	4 9% 4 9% 5% 4 4 4 5% 7% 46%	3924
	21st to end	Day	5% 7% 4 11% 5% 4 4 3 4 5% 49%	4488
February	1st to 10th	Day	8% 11% 4 8% 6% 4 4 4 5% 6% 40%	1800
	11th to 20th	Day	6% 9% 3 8% 4 4 4 3 6% 7% 47%	1944
	21st to end	Day	8% 7% 2 5% 3 4 4 4 4 6% 52%	1650
March	1st to 10th	Day	11% 7% 2 5% 3 3 2 2 3 5% 56%	4624
	11th to 20th	Day	9% 7% 2 5% 3 3 3 2 4 7% 54%	4980
	21st to end	Day	13% 10% 3 6% 4 3 4 4 5% 8% 40%	5464
April	1st to 10th	Day	11% 7% 2 5% 4 5% 3 3 6% 7% 48%	2287
	11th to 20th	Day	13% 7% 2 6% 4 4 3 3 6% 7% 44%	2504
	21st to end	Day	17% 7% 2 6% 4 4 4 3 5% 7% 41%	2600
May	1st to 10th	Day	11% 6% 2 5% 4 3 4 3 6% 7% 49%	5900
	11th to 20th	Day	12% 5% 2 5% 3 3 3 3 5% 6% 53%	5862
	21st to end	Day	18% 7% 2 6% 4 4 4 3 5% 7% 40%	6446
June	1st to 10th	Day	6% 4 1 5% 4 3 4 4 6% 8% 56%	2634
	11th to 20th	Day	8% 5% 2 4 3 4 4 4 6% 8% 52%	2800
	21st to end	Day	6% 4 2 4 3 4 5% 4 6% 9% 54%	2800
July	1st to 10th	Day	10% 6% 2 5% 4 4 4 3 6% 7% 50%	4570
	11th to 20th	Day	6% 5% 2 6% 4 4 4 4 6% 8% 51%	4445
	21st to end	Day	4 4 2 5% 3 4 5% 4 6% 9% 55%	4467
August	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 4 7% 9% 46%	4103
	11th to 20th	Day	13% 7% 2 6% 4 4 4 3 5% 7% 44%	4041
	21st to end	Day	6% 4 2 5% 4 4 3 3 5% 6% 58%	4409
September	1st to 10th	Day	11% 6% 2 5% 3 3 4 3 5% 5% 56%	2152
	11th to 20th	Day	8% 4 2 5% 2 3 3 3 5% 6% 58%	2090
	21st to end	Day	10% 4 1 3 3 3 3 3 3 6% 61%	2090
October	1st to 10th	Day	8% 4 1 3 1 2 2 2 2 4 71%	3421
	11th to 20th	Day	6% 3 1 3 2 2 3 2 4 6% 66%	3140
	21st to end	Day	10% 5% 2 4 3 3 3 2 4 6% 57%	3228
November	1st to 10th	Day	7% 5% 2 5% 3 4 4 3 5% 7% 55%	1763
	11th to 20th	Day	7% 7% 2 5% 4 3 3 3 4 5% 58%	1800
	21st to end	Day	10% 8% 2 6% 3 3 3 3 4 6% 51%	1800
December	1st to 10th	Day	4 5% 3 5% 4 4 4 4 5% 6% 58%	2940
	11th to 20th	Day	6% 8% 3 6% 5% 4 4 3 5% 7% 50%	3391
	21st to end	Day	13% 9% 4 12% 4 4 4 3 4 6% 38%	4180
January	1st to 10th	Night	8% 12% 4 11% 5% 4 4 3 6% 6% 36%	6327
	11th to 20th	Night	4 7% 2 7% 5% 4 5% 4 6% 7% 50%	6036
	21st to end	Night	6% 8% 4 11% 4 4 4 3 4 5% 48%	6490
February	1st to 10th	Night	8% 11% 4 8% 5% 4 4 3 5% 6% 43%	2600
	11th to 20th	Night	5% 9% 3 7% 5% 4 5% 4 5% 7% 45%	2358
	21st to end	Night	6% 7% 2 5% 4 4 3 3 5% 7% 54%	1980
March	1st to 10th	Night	9% 5% 2 5% 3 3 3 3 4 5% 56%	5242
	11th to 20th	Night	10% 5% 1 4 3 3 3 3 4 6% 59%	4980
	21st to end	Night	12% 9% 3 6% 4 5% 5% 4 6% 7% 40%	5467
April	1st to 10th	Night	11% 7% 2 5% 4 4 4 4 5% 7% 48%	2110
	11th to 20th	Night	13% 6% 2 5% 4 4 5% 4 5% 7% 45%	1844
	21st to end	Night	14% 5% 2 5% 3 4 4 3 6% 8% 49%	1800
May	1st to 10th	Night	16% 6% 2 4 3 3 3 3 5% 6% 48%	4080
	11th to 20th	Night	10% 5% 2 4 3 3 3 3 5% 7% 53%	4053
	21st to end	Night	17% 6% 2 5% 4 3 4 4 5% 8% 43%	4451
June	1st to 10th	Night	6% 4 1 4 3 4 4 4 5% 10% 54%	1760
	11th to 20th	Night	8% 4 2 4 4 3 3 3 4 10% 54%	1600
	21st to end	Night	4 4 2 4 3 4 4 3 6% 9% 58%	1600
July	1st to 10th	Night	8% 5% 2 5% 4 4 3 4 5% 7% 54%	2620
	11th to 20th	Night	5% 3 1 5% 3 5% 4 4 7% 10% 52%	2742
	21st to end	Night	3 3 1 3 3 3 4 3 5% 9% 63%	3097
August	1st to 10th	Night	5% 4 2 4 4 4 4 4 8% 10% 52%	2836
	11th to 20th	Night	10% 5% 2 5% 4 4 4 3 6% 9% 48%	2798
	21st to end	Night	4 4 1 5% 3 4 4 4 6% 9% 57%	3254
September	1st to 10th	Night	8% 3 1 3 3 3 3 3 4 7% 64%	2028
	11th to 20th	Night	8% 3 2 4 3 3 3 3 5% 6% 60%	2090
	21st to end	Night	8% 3 2 4 3 2 4 3 5% 5% 61%	2090
October	1st to 10th	Night	8% 3 1 2 2 2 2 2 3 4 71%	3507
	11th to 20th	Night	6% 3 1 4 3 2 3 2 4 6% 66%	3779
	21st to end	Night	9% 4 1 4 3 3 3 2 5% 7% 59%	4323
November	1st to 10th	Night	6% 4 1 4 2 3 3 3 6% 7% 61%	2535
	11th to 20th	Night	7% 5% 2 4 3 3 3 3 5% 6% 58%	2600
	21st to end	Night	8% 6% 2 4 3 3 3 3 5% 6% 56%	2600
December	1st to 10th	Night	3 5% 1 4 3 3 3 3 5% 7% 63%	4250
	11th to 20th	Night	7% 4 2 5% 4 4 4 4 6% 9% 52%	4816
	21st to end	Night	13% 12% 3 8% 4 4 3 3 5% 5% 39%	6776

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	49% 3 11% 23% 12% 1	3639
	11th to 20th	Day	40% 4 13% 21% 20% 3	3924
	21st to end	Day	40% 3 13% 27% 15% 3	4488
February	1st to 10th	Day	45% 5% 15% 22% 11% 3	1800
	11th to 20th	Day	37% 4 16% 24% 15% 4	1954
	21st to end	Day	33% 4 12% 28% 18% 6%	1650
March	1st to 10th	Day	33% 3 8% 23% 26% 8%	4624
	11th to 20th	Day	32% 3 9% 25% 25% 7%	4980
	21st to end	Day	43% 3 23% 23% 7% 1	5464
April	1st to 10th	Day	36% 4 15% 27% 16% 2	2287
	11th to 20th	Day	40% 4 14% 24% 16% 3	2507
	21st to end	Day	43% 5% 11% 26% 14% 1	2600
May	1st to 10th	Day	32% 5% 13% 26% 20% 4	5900
	11th to 20th	Day	33% 4 12% 26% 20% 7%	5866
	21st to end	Day	43% 5% 10% 27% 14% 1	6447
June	1st to 10th	Day	26% 6% 18% 32% 15% 2	2634
	11th to 20th	Day	30% 5% 14% 30% 18% 3	2800
	21st to end	Day	26% 6% 14% 30% 20% 4	2800
July	1st to 10th	Day	33% 4 11% 28% 22% 2	4501
	11th to 20th	Day	30% 6% 14% 28% 20% 3	4370
	21st to end	Day	24% 6% 15% 25% 23% 7%	4326
August	1st to 10th	Day	33% 6% 16% 25% 16% 4	4090
	11th to 20th	Day	38% 6% 14% 23% 18% 1	4080
	21st to end	Day	27% 5% 13% 24% 22% 8%	4408
September	1st to 10th	Day	32% 4 10% 25% 22% 7%	2152
	11th to 20th	Day	28% 4 11% 31% 23% 3	2090
	21st to end	Day	25% 4 9% 34% 27% 2	2090
October	1st to 10th	Day	20% 2 5% 21% 43% 8%	3421
	11th to 20th	Day	21% 3 11% 36% 21% 9%	3140
	21st to end	Day	29% 2 10% 30% 25% 4	3228
November	1st to 10th	Day	28% 4 14% 29% 21% 3	1763
	11th to 20th	Day	30% 3 10% 27% 26% 4	1800
	21st to end	Day	35% 3 13% 26% 19% 4	1800
December	1st to 10th	Day	28% 4 12% 34% 20% 3	2940
	11th to 20th	Day	35% 4 19% 29% 13% 1	3389
	21st to end	Day	49% 3 9% 26% 11% 1	4180
January	1st to 10th	Night	47% 3 11% 23% 15% 1	6327
	11th to 20th	Night	34% 3 13% 26% 22% 2	6036
	21st to end	Night	40% 3 11% 22% 20% 5%	6490
February	1st to 10th	Night	42% 5% 13% 23% 14% 3	2600
	11th to 20th	Night	37% 5% 13% 26% 16% 3	2358
	21st to end	Night	31% 3 12% 22% 24% 8%	1980
March	1st to 10th	Night	30% 3 7% 26% 26% 7%	5242
	11th to 20th	Night	28% 3 7% 21% 31% 11%	4980
	21st to end	Night	43% 4 21% 24% 8% 1	5467
April	1st to 10th	Night	35% 5% 13% 25% 20% 3	2110
	11th to 20th	Night	36% 5% 15% 26% 16% 3	1844
	21st to end	Night	35% 5% 14% 27% 17% 2	1800
May	1st to 10th	Night	36% 5% 11% 28% 18% 2	4080
	11th to 20th	Night	31% 3 14% 24% 21% 7%	4054
	21st to end	Night	40% 6% 14% 23% 16% 1	4452
June	1st to 10th	Night	25% 6% 21% 29% 18% 2	1760
	11th to 20th	Night	28% 5% 15% 29% 18% 5%	1600
	21st to end	Night	23% 5% 17% 30% 22% 4	1600
July	1st to 10th	Night	30% 5% 13% 31% 18% 3	2580
	11th to 20th	Night	26% 6% 15% 32% 18% 4	2694
	21st to end	Night	17% 6% 17% 27% 24% 8%	2999
August	1st to 10th	Night	26% 5% 18% 27% 19% 5%	2826
	11th to 20th	Night	33% 5% 18% 27% 16% 2	2825
	21st to end	Night	24% 6% 16% 28% 18% 9%	3254
September	1st to 10th	Night	22% 4 10% 29% 26% 10%	2028
	11th to 20th	Night	26% 4 9% 32% 25% 5%	2090
	21st to end	Night	25% 4 9% 29% 29% 4	2090
October	1st to 10th	Night	19% 3 6% 18% 45% 9%	3507
	11th to 20th	Night	21% 2 10% 30% 26% 11%	3779
	21st to end	Night	26% 3 10% 29% 28% 4	4323
November	1st to 10th	Night	22% 4 12% 29% 26% 6%	2535
	11th to 20th	Night	27% 3 9% 30% 25% 6%	2600
	21st to end	Night	29% 3 13% 28% 24% 4	2600
December	1st to 10th	Night	22% 3 16% 37% 20% 2	4250
	11th to 20th	Night	29% 4 15% 34% 17% 1	4817
	21st to end	Night	47% 3 10% 27% 12% 1	6776

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	15% 10% 41% 24% 8% 1	300
	11th to 20th	Day	15% 16% 34% 27% 8%	300
	21st to end	Day	14% 8% 43% 24% 9% 1	330
February	1st to 10th	Day	14% 13% 44% 24% 4 1	300
	11th to 20th	Day	11% 11% 46% 24% 6% 1	300
	21st to end	Day	12% 18% 47% 20% 3	249
March	1st to 10th	Day	14% 13% 44% 24% 5% 1	300
	11th to 20th	Day	22% 10% 38% 20% 10% 1	300
	21st to end	Day	23% 16% 38% 18% 4 1	330
April	1st to 10th	Day	16% 21% 41% 19% 3	387
	11th to 20th	Day	19% 15% 37% 25% 4	625
	21st to end	Day	22% 16% 33% 20% 8% 2	700
May	1st to 10th	Day	16% 11% 30% 30% 11% 2	703
	11th to 20th	Day	19% 10% 32% 24% 13% 3	725
	21st to end	Day	17% 9% 32% 28% 12% 2	789
June	1st to 10th	Day	7% 6% 27% 35% 20% 5%	730
	11th to 20th	Day	9% 7% 35% 31% 16% 2	730
	21st to end	Day	8% 7% 32% 35% 17% 2	730
July	1st to 10th	Day	9% 2 20% 38% 24% 6%	721
	11th to 20th	Day	6% 4 19% 45% 21% 6%	718
	21st to end	Day	7% 2 19% 40% 27% 6%	740
August	1st to 10th	Day	9% 2 17% 45% 23% 4	676
	11th to 20th	Day	8% 3 22% 42% 24% 2	665
	21st to end	Day	9% 2 24% 38% 22% 5%	677
September	1st to 10th	Day	14% 4 24% 39% 15% 4	362
	11th to 20th	Day	7% 7% 27% 37% 17% 5%	300
	21st to end	Day	16% 8% 27% 27% 17% 5%	300
October	1st to 10th	Day	20% 8% 22% 32% 14% 4	300
	11th to 20th	Day	10% 13% 38% 26% 10% 2	300
	21st to end	Day	18% 15% 34% 24% 8% 1	330
November	1st to 10th	Day	12% 15% 38% 23% 9% 3	300
	11th to 20th	Day	13% 15% 43% 20% 9%	300
	21st to end	Day	19% 14% 35% 22% 9% 2	300
December	1st to 10th	Day	7% 9% 44% 31% 7% 1	300
	11th to 20th	Day	15% 8% 41% 27% 8%	300
	21st to end	Day	18% 11% 46% 22% 3	330
January	1st to 10th	Night	13% 10% 39% 33% 6% 1	1000
	11th to 20th	Night	11% 11% 41% 30% 6% 1	1000
	21st to end	Night	11% 9% 41% 31% 7%	1100
February	1st to 10th	Night	14% 11% 43% 27% 5%	1000
	11th to 20th	Night	11% 11% 44% 30% 4	804
	21st to end	Night	10% 12% 46% 27% 5%	660
March	1st to 10th	Night	13% 11% 43% 28% 4 1	746
	11th to 20th	Night	16% 9% 41% 28% 5% 1	600
	21st to end	Night	18% 12% 42% 24% 5%	660
April	1st to 10th	Night	16% 14% 42% 25% 3	600
	11th to 20th	Night	16% 13% 43% 25% 3	593
	21st to end	Night	17% 12% 33% 31% 7% 1	600
May	1st to 10th	Night	17% 9% 36% 30% 8%	600
	11th to 20th	Night	15% 7% 36% 34% 8%	591
	21st to end	Night	16% 8% 33% 31% 12% 1	650
June	1st to 10th	Night	8% 5% 26% 46% 13% 2	600
	11th to 20th	Night	9% 7% 37% 37% 11%	600
	21st to end	Night	6% 6% 36% 41% 13%	600
July	1st to 10th	Night	6% 4 21% 45% 23% 1	585
	11th to 20th	Night	4 2 21% 49% 22% 1	582
	21st to end	Night	4 2 19% 52% 23%	624
August	1st to 10th	Night	6% 2 19% 49% 20% 2	567
	11th to 20th	Night	8% 3 25% 47% 18%	564
	21st to end	Night	7% 3 23% 46% 19% 2	627
September	1st to 10th	Night	10% 2 27% 45% 15% 1	570
	11th to 20th	Night	10% 4 33% 39% 14% 1	570
	21st to end	Night	9% 5% 36% 35% 14% 1	570
October	1st to 10th	Night	17% 7% 31% 32% 13% 1	584
	11th to 20th	Night	13% 9% 38% 31% 8%	760
	21st to end	Night	15% 11% 32% 31% 9%	951
November	1st to 10th	Night	8% 11% 37% 37% 7%	975
	11th to 20th	Night	11% 11% 40% 31% 6% 1	1000
	21st to end	Night	10% 11% 36% 32% 10% 1	1000
December	1st to 10th	Night	9% 10% 45% 31% 4	1000
	11th to 20th	Night	12% 11% 40% 30% 6%	1000
	21st to end	Night	16% 11% 38% 29% 6%	1100

Page generated at 2025-07-18 00:10:02. Version ac07

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