Lincoln
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lincoln clear sky chart from 2005-11-06 to 2025-08-05.

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 3 5% 7% 46%	125261
	Night	10% 7% 2 6% 4 3 4 3 5% 6% 49%	123061
Transparency	Day	37% 5% 13% 25% 17% 3	128911
	Night	34% 5% 12% 26% 20% 3	127474
Seeing	Day	14% 10% 31% 29% 14% 3	16833
	Night	13% 9% 34% 33% 10%	26668

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% 13% 8% 6% 5% 3 4 5% 28%	4077
	11th to 20th	Day	7% 9% 4 8% 4 6% 6% 4 5% 4 43%	4080
	21st to end	Day	5% 10% 5% 11% 5% 5% 4 3 4 6% 42%	4488
February	1st to 10th	Day	10% 12% 5% 8% 6% 4 4 4 6% 6% 36%	1800
	11th to 20th	Day	9% 11% 3 8% 4 4 4 3 6% 6% 42%	1829
	21st to end	Day	9% 7% 4 6% 5% 4 4 3 5% 7% 48%	1650
March	1st to 10th	Day	13% 9% 2 5% 3 2 2 2 2 4 54%	4824
	11th to 20th	Day	11% 7% 2 5% 3 3 3 3 5% 6% 52%	4980
	21st to end	Day	17% 11% 3 7% 4 4 4 4 6% 7% 33%	5462
April	1st to 10th	Day	15% 7% 2 5% 4 4 3 3 5% 6% 46%	2229
	11th to 20th	Day	15% 8% 2 6% 4 4 4 3 5% 7% 42%	2520
	21st to end	Day	19% 8% 3 6% 3 4 4 3 5% 7% 38%	2600
May	1st to 10th	Day	13% 7% 2 6% 4 3 4 3 5% 7% 46%	5862
	11th to 20th	Day	13% 6% 2 5% 4 3 3 2 4 5% 52%	5862
	21st to end	Day	18% 7% 2 7% 4 4 5% 4 6% 7% 37%	6434
June	1st to 10th	Day	7% 5% 2 5% 4 4 4 4 6% 8% 51%	2740
	11th to 20th	Day	8% 6% 2 4 4 4 4 5% 6% 9% 47%	2800
	21st to end	Day	7% 5% 1 5% 5% 5% 5% 4 6% 9% 48%	2682
July	1st to 10th	Day	9% 5% 2 5% 4 4 4 4 6% 9% 47%	5900
	11th to 20th	Day	7% 5% 2 7% 5% 4 5% 4 6% 9% 47%	5900
	21st to end	Day	6% 4 2 5% 4 4 4 4 7% 9% 51%	6422
August	1st to 10th	Day	7% 5% 2 5% 4 5% 6% 5% 7% 10% 45%	4157
	11th to 20th	Day	11% 6% 2 7% 4 4 5% 4 7% 7% 43%	4041
	21st to end	Day	6% 4 2 5% 4 4 5% 4 6% 8% 52%	4482
September	1st to 10th	Day	13% 4 2 4 2 3 3 4 5% 6% 54%	2161
	11th to 20th	Day	9% 5% 1 5% 3 4 4 3 4 6% 55%	2090
	21st to end	Day	10% 4 1 5% 3 3 3 2 5% 6% 58%	2090
October	1st to 10th	Day	13% 7% 2 4 3 3 3 3 3 5% 54%	1971
	11th to 20th	Day	11% 5% 2 5% 3 2 3 3 3 4 58%	1900
	21st to end	Day	13% 8% 2 5% 3 4 3 2 4 7% 49%	2090
November	1st to 10th	Day	9% 6% 2 5% 3 3 3 3 5% 6% 54%	1763
	11th to 20th	Day	10% 6% 2 6% 4 3 4 3 5% 6% 51%	1800
	21st to end	Day	12% 9% 3 5% 3 3 4 3 5% 8% 45%	1625
December	1st to 10th	Day	5% 5% 3 6% 5% 4 4 3 5% 6% 55%	2610
	11th to 20th	Day	8% 9% 4 8% 5% 4 4 3 5% 6% 45%	3008
	21st to end	Day	16% 11% 4 13% 4 4 3 3 4 5% 32%	4332
January	1st to 10th	Night	10% 10% 4 16% 6% 5% 4 3 6% 5% 29%	5888
	11th to 20th	Night	6% 7% 3 7% 4 5% 7% 4 6% 6% 45%	5900
	21st to end	Night	9% 10% 5% 10% 4 3 3 2 4 5% 45%	6490
February	1st to 10th	Night	11% 11% 4 7% 5% 5% 4 4 5% 6% 40%	2600
	11th to 20th	Night	9% 9% 2 7% 6% 5% 4 4 5% 7% 42%	2473
	21st to end	Night	9% 8% 3 6% 4 3 4 3 4 7% 51%	1980
March	1st to 10th	Night	13% 5% 2 5% 3 3 3 3 4 5% 54%	5035
	11th to 20th	Night	10% 6% 2 4 3 3 2 3 4 6% 58%	4980
	21st to end	Night	15% 10% 2 7% 5% 4 5% 4 6% 7% 37%	5467
April	1st to 10th	Night	12% 8% 2 5% 4 3 3 3 5% 7% 47%	2170
	11th to 20th	Night	10% 7% 2 6% 4 3 3 3 5% 8% 47%	1828
	21st to end	Night	16% 7% 2 6% 3 4 4 3 4 7% 44%	1800
May	1st to 10th	Night	14% 6% 2 5% 3 3 4 3 4 6% 50%	4053
	11th to 20th	Night	12% 5% 1 4 3 2 3 2 4 6% 56%	4053
	21st to end	Night	17% 6% 2 6% 3 3 4 3 5% 7% 45%	4443
June	1st to 10th	Night	5% 3 2 4 5% 4 4 3 7% 9% 54%	1655
	11th to 20th	Night	6% 4 2 4 4 3 4 4 7% 10% 52%	1600
	21st to end	Night	5% 3 1 4 3 3 4 4 7% 8% 59%	1708
July	1st to 10th	Night	7% 5% 2 6% 3 4 4 3 6% 7% 54%	4078
	11th to 20th	Night	6% 4 2 5% 3 4 4 4 7% 9% 51%	4077
	21st to end	Night	5% 4 2 4 4 3 4 4 7% 9% 55%	4449
August	1st to 10th	Night	3 3 2 4 4 3 4 3 6% 10% 59%	2872
	11th to 20th	Night	11% 5% 2 5% 3 3 4 4 5% 8% 50%	2798
	21st to end	Night	6% 5% 1 4 3 4 3 3 6% 8% 57%	3183
September	1st to 10th	Night	8% 4 2 4 2 2 3 2 5% 7% 61%	2015
	11th to 20th	Night	8% 3 1 4 3 2 4 3 4 7% 59%	2090
	21st to end	Night	9% 4 2 4 2 3 3 3 4 5% 60%	2090
October	1st to 10th	Night	12% 6% 2 4 3 4 3 3 4 6% 52%	2190
	11th to 20th	Night	12% 5% 2 4 3 2 2 2 4 4 59%	2280
	21st to end	Night	13% 6% 2 5% 2 2 3 3 4 5% 54%	2508
November	1st to 10th	Night	8% 4 2 4 3 3 3 3 5% 6% 58%	2530
	11th to 20th	Night	9% 6% 2 5% 4 3 3 3 5% 5% 54%	2600
	21st to end	Night	11% 8% 2 4 3 2 3 3 4 6% 53%	2771
December	1st to 10th	Night	5% 5% 2 5% 4 3 3 3 5% 6% 58%	4580
	11th to 20th	Night	9% 7% 3 9% 3 3 3 3 5% 6% 48%	5199
	21st to end	Night	16% 13% 4 10% 4 3 3 3 4 5% 36%	6628

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% 10% 20% 8% 1	4078
	11th to 20th	Day	42% 5% 12% 21% 18% 2	4080
	21st to end	Day	44% 5% 12% 23% 15% 1	4488
February	1st to 10th	Day	47% 6% 16% 20% 10% 1	1800
	11th to 20th	Day	43% 5% 12% 22% 15% 3	1838
	21st to end	Day	36% 6% 13% 25% 17% 3	1650
March	1st to 10th	Day	36% 3 8% 25% 20% 7%	4824
	11th to 20th	Day	33% 5% 8% 25% 25% 5%	4980
	21st to end	Day	48% 7% 21% 17% 5% 2	5464
April	1st to 10th	Day	38% 5% 13% 26% 16% 3	2229
	11th to 20th	Day	41% 5% 13% 24% 14% 3	2520
	21st to end	Day	45% 7% 10% 25% 13% 1	2600
May	1st to 10th	Day	36% 6% 12% 27% 18% 2	5900
	11th to 20th	Day	35% 5% 9% 22% 24% 5%	5866
	21st to end	Day	44% 7% 10% 25% 13% 1	6447
June	1st to 10th	Day	29% 7% 17% 31% 13% 2	2740
	11th to 20th	Day	31% 8% 14% 29% 16% 2	2800
	21st to end	Day	31% 9% 14% 28% 14% 4	2682
July	1st to 10th	Day	33% 5% 14% 31% 17% 1	5836
	11th to 20th	Day	34% 5% 15% 28% 16% 2	5831
	21st to end	Day	29% 5% 17% 29% 17% 2	6240
August	1st to 10th	Day	32% 8% 16% 26% 16% 3	4143
	11th to 20th	Day	38% 6% 16% 23% 17% 1	4080
	21st to end	Day	30% 5% 16% 25% 19% 6%	4481
September	1st to 10th	Day	30% 5% 11% 28% 20% 5%	2161
	11th to 20th	Day	30% 5% 12% 29% 22% 2	2090
	21st to end	Day	28% 4 9% 32% 25% 2	2090
October	1st to 10th	Day	21% 4 6% 19% 46% 4	3270
	11th to 20th	Day	21% 3 11% 30% 27% 8%	3140
	21st to end	Day	33% 3 11% 28% 22% 3	3428
November	1st to 10th	Day	31% 4 14% 27% 21% 3	1763
	11th to 20th	Day	34% 5% 12% 26% 21% 2	1800
	21st to end	Day	39% 4 12% 29% 15% 2	1625
December	1st to 10th	Day	30% 4 16% 30% 18% 1	2610
	11th to 20th	Day	40% 4 18% 28% 10% 1	3005
	21st to end	Day	55% 5% 10% 22% 8% 1	4332
January	1st to 10th	Night	54% 5% 11% 17% 12%	5888
	11th to 20th	Night	38% 5% 14% 24% 18% 2	5900
	21st to end	Night	43% 3 11% 20% 20% 2	6490
February	1st to 10th	Night	45% 5% 13% 20% 14% 3	2600
	11th to 20th	Night	41% 5% 13% 23% 15% 3	2474
	21st to end	Night	33% 5% 10% 24% 22% 6%	1980
March	1st to 10th	Night	33% 4 8% 27% 26% 3	5035
	11th to 20th	Night	29% 4 6% 23% 30% 8%	4980
	21st to end	Night	44% 6% 19% 23% 6% 1	5467
April	1st to 10th	Night	36% 5% 11% 26% 18% 4	2170
	11th to 20th	Night	35% 5% 13% 26% 17% 3	1828
	21st to end	Night	40% 6% 11% 25% 17% 1	1800
May	1st to 10th	Night	35% 5% 11% 26% 22% 2	4080
	11th to 20th	Night	30% 5% 12% 21% 26% 6%	4054
	21st to end	Night	39% 6% 13% 22% 19% 1	4452
June	1st to 10th	Night	25% 8% 16% 31% 18% 2	1655
	11th to 20th	Night	26% 7% 15% 29% 19% 5%	1600
	21st to end	Night	22% 7% 14% 33% 22% 3	1708
July	1st to 10th	Night	30% 5% 12% 31% 18% 3	4035
	11th to 20th	Night	30% 5% 14% 28% 21% 2	4026
	21st to end	Night	24% 6% 18% 26% 24% 2	4320
August	1st to 10th	Night	22% 6% 18% 31% 21% 3	2862
	11th to 20th	Night	33% 4 16% 29% 16% 1	2825
	21st to end	Night	26% 4 16% 28% 17% 9%	3183
September	1st to 10th	Night	24% 4 12% 28% 23% 8%	2015
	11th to 20th	Night	24% 5% 11% 33% 23% 4	2090
	21st to end	Night	26% 4 8% 28% 30% 4	2090
October	1st to 10th	Night	21% 4 7% 16% 46% 7%	3658
	11th to 20th	Night	22% 2 8% 31% 28% 9%	3779
	21st to end	Night	31% 3 9% 31% 24% 2	4120
November	1st to 10th	Night	26% 5% 13% 26% 25% 5%	2530
	11th to 20th	Night	32% 4 11% 30% 20% 4	2600
	21st to end	Night	34% 4 13% 27% 21% 3	2771
December	1st to 10th	Night	27% 4 15% 34% 18% 1	4580
	11th to 20th	Night	37% 4 15% 29% 14% 1	5201
	21st to end	Night	52% 4 10% 24% 8% 1	6628

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	18% 15% 39% 20% 7% 1	300
	11th to 20th	Day	19% 15% 38% 21% 6%	300
	21st to end	Day	13% 14% 42% 22% 8%	330
February	1st to 10th	Day	15% 20% 43% 19% 3	300
	11th to 20th	Day	18% 15% 37% 23% 7%	300
	21st to end	Day	12% 19% 43% 21% 5%	249
March	1st to 10th	Day	18% 13% 42% 22% 4 1	300
	11th to 20th	Day	24% 13% 36% 19% 6% 1	300
	21st to end	Day	30% 16% 37% 14% 3	330
April	1st to 10th	Day	22% 20% 37% 17% 4	329
	11th to 20th	Day	20% 16% 37% 20% 7%	638
	21st to end	Day	24% 15% 32% 19% 8% 2	700
May	1st to 10th	Day	18% 12% 33% 25% 10% 2	703
	11th to 20th	Day	19% 10% 33% 24% 13% 2	725
	21st to end	Day	17% 9% 32% 28% 13% 2	789
June	1st to 10th	Day	6% 6% 23% 38% 22% 5%	730
	11th to 20th	Day	9% 6% 31% 34% 16% 4	730
	21st to end	Day	8% 6% 35% 36% 13% 2	730
July	1st to 10th	Day	9% 4 19% 35% 25% 7%	721
	11th to 20th	Day	6% 3 23% 40% 21% 8%	718
	21st to end	Day	8% 2 18% 41% 27% 4	794
August	1st to 10th	Day	7% 2 23% 40% 23% 4	697
	11th to 20th	Day	9% 4 19% 43% 22% 3	665
	21st to end	Day	10% 3 21% 34% 26% 5%	724
September	1st to 10th	Day	13% 4 24% 36% 20% 3	371
	11th to 20th	Day	6% 6% 27% 36% 21% 4	300
	21st to end	Day	12% 9% 31% 28% 16% 4	300
October	1st to 10th	Day	22% 7% 24% 27% 15% 6%	300
	11th to 20th	Day	10% 15% 41% 24% 9% 1	300
	21st to end	Day	16% 15% 39% 20% 9% 1	330
November	1st to 10th	Day	17% 14% 37% 23% 6% 2	300
	11th to 20th	Day	15% 16% 40% 23% 7%	300
	21st to end	Day	20% 13% 33% 24% 9% 1	300
December	1st to 10th	Day	8% 14% 42% 28% 6% 1	300
	11th to 20th	Day	17% 13% 38% 24% 7%	300
	21st to end	Day	19% 16% 42% 20% 3	330
January	1st to 10th	Night	13% 12% 38% 30% 7%	1000
	11th to 20th	Night	14% 12% 40% 28% 6%	1000
	21st to end	Night	14% 9% 42% 30% 5%	1100
February	1st to 10th	Night	16% 11% 42% 27% 4	1000
	11th to 20th	Night	13% 14% 41% 29% 4	919
	21st to end	Night	13% 14% 44% 24% 5%	660
March	1st to 10th	Night	13% 15% 39% 27% 6%	655
	11th to 20th	Night	18% 10% 39% 27% 5%	600
	21st to end	Night	21% 12% 39% 22% 5%	660
April	1st to 10th	Night	17% 14% 43% 22% 5%	600
	11th to 20th	Night	14% 16% 40% 26% 3 1	593
	21st to end	Night	19% 12% 34% 27% 7% 1	600
May	1st to 10th	Night	18% 8% 34% 30% 10%	600
	11th to 20th	Night	14% 10% 32% 35% 9% 1	591
	21st to end	Night	16% 9% 30% 32% 12% 1	650
June	1st to 10th	Night	5% 5% 27% 45% 18%	600
	11th to 20th	Night	7% 4 33% 43% 13%	600
	21st to end	Night	5% 5% 36% 41% 13%	600
July	1st to 10th	Night	7% 3 17% 43% 29% 1	585
	11th to 20th	Night	4 1 20% 50% 24% 1	582
	21st to end	Night	3 1 17% 54% 24% 1	657
August	1st to 10th	Night	5% 2 18% 51% 21% 2	579
	11th to 20th	Night	7% 2 20% 49% 21% 1	564
	21st to end	Night	9% 2 23% 40% 24% 3	627
September	1st to 10th	Night	9% 2 28% 41% 19% 1	570
	11th to 20th	Night	9% 2 30% 43% 15% 1	570
	21st to end	Night	11% 5% 34% 34% 16% 1	570
October	1st to 10th	Night	15% 7% 31% 33% 12% 2	670
	11th to 20th	Night	15% 9% 39% 30% 7%	760
	21st to end	Night	17% 12% 32% 30% 9%	836
November	1st to 10th	Night	10% 11% 35% 35% 9%	970
	11th to 20th	Night	13% 12% 40% 29% 6%	1000
	21st to end	Night	14% 13% 36% 28% 8% 1	1000
December	1st to 10th	Night	12% 12% 41% 29% 6% 1	1000
	11th to 20th	Night	16% 12% 35% 32% 6%	1000
	21st to end	Night	19% 11% 37% 28% 5%	1100

Page generated at 2025-08-02 00:32:23. Version ac07

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