Lane
Clear Sky Chart
History

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

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	10% 6% 3 7% 5% 4 4 4 5% 7% 45%	135850
	Night	9% 7% 3 7% 4 4 4 4 5% 7% 47%	133486
Transparency	Day	39% 5% 14% 26% 15% 2	130519
	Night	37% 5% 14% 26% 16% 2	129824
Seeing	Day	13% 10% 32% 30% 13% 2	17619
	Night	12% 9% 35% 34% 10% 1	27652

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	8% 12% 6% 15% 9% 6% 6% 3 4 5% 26%	3718
	11th to 20th	Day	4 8% 4 12% 8% 7% 8% 3 6% 8% 33%	3720
	21st to end	Day	4 8% 5% 10% 6% 5% 4 4 5% 6% 42%	4293
February	1st to 10th	Day	9% 13% 4 10% 7% 5% 6% 4 5% 6% 33%	1800
	11th to 20th	Day	7% 9% 4 11% 6% 5% 5% 3 6% 6% 37%	1858
	21st to end	Day	8% 10% 4 8% 5% 5% 5% 5% 6% 7% 38%	1650
March	1st to 10th	Day	9% 9% 3 7% 4 3 3 3 5% 6% 48%	4581
	11th to 20th	Day	6% 6% 3 5% 4 3 4 4 6% 9% 50%	4980
	21st to end	Day	19% 12% 3 10% 5% 5% 4 3 5% 6% 25%	5464
April	1st to 10th	Day	15% 6% 2 5% 4 4 4 4 6% 8% 41%	2330
	11th to 20th	Day	17% 8% 3 7% 5% 4 4 3 4 6% 38%	2554
	21st to end	Day	18% 9% 2 6% 4 4 4 3 5% 6% 39%	2600
May	1st to 10th	Day	11% 5% 2 4 4 3 4 4 5% 7% 52%	5900
	11th to 20th	Day	17% 5% 2 5% 3 3 3 3 4 6% 48%	5862
	21st to end	Day	17% 7% 2 6% 4 4 4 3 6% 7% 40%	6881
June	1st to 10th	Day	10% 6% 2 6% 4 4 5% 3 5% 8% 48%	3000
	11th to 20th	Day	12% 4 2 5% 4 4 4 4 6% 8% 47%	3000
	21st to end	Day	9% 4 1 4 4 3 5% 4 6% 7% 52%	3000
July	1st to 10th	Day	9% 4 2 5% 4 4 5% 4 6% 9% 48%	6481
	11th to 20th	Day	8% 4 2 5% 4 4 4 3 6% 7% 54%	6340
	21st to end	Day	7% 4 2 5% 4 4 5% 5% 7% 11% 47%	6732
August	1st to 10th	Day	8% 6% 2 7% 4 5% 5% 4 6% 9% 44%	5801
	11th to 20th	Day	11% 6% 2 5% 4 5% 5% 4 6% 8% 43%	5821
	21st to end	Day	7% 4 2 6% 4 3 3 3 4 7% 56%	6490
September	1st to 10th	Day	10% 5% 1 4 3 3 3 3 4 7% 56%	2302
	11th to 20th	Day	9% 5% 2 5% 3 3 2 3 4 7% 57%	2200
	21st to end	Day	10% 4 2 5% 3 2 3 2 4 6% 58%	2200
October	1st to 10th	Day	8% 3 1 3 2 2 2 3 4 6% 65%	3468
	11th to 20th	Day	9% 5% 2 5% 4 3 4 3 4 6% 56%	3240
	21st to end	Day	11% 7% 2 6% 5% 4 5% 4 5% 7% 44%	3208
November	1st to 10th	Day	9% 7% 3 5% 4 4 5% 4 5% 7% 47%	1853
	11th to 20th	Day	6% 8% 2 8% 5% 3 4 4 5% 7% 48%	1854
	21st to end	Day	8% 8% 4 7% 5% 4 4 3 6% 7% 44%	1680
December	1st to 10th	Day	5% 8% 4 11% 8% 7% 5% 4 5% 7% 36%	2607
	11th to 20th	Day	7% 11% 5% 9% 6% 6% 6% 4 7% 8% 33%	2713
	21st to end	Day	15% 8% 4 12% 6% 4 5% 3 5% 6% 32%	3669
January	1st to 10th	Night	5% 11% 5% 12% 9% 7% 6% 5% 6% 6% 28%	6467
	11th to 20th	Night	2 7% 4 11% 6% 6% 7% 4 8% 7% 37%	6480
	21st to end	Night	4 7% 5% 10% 5% 4 4 3 5% 5% 46%	6925
February	1st to 10th	Night	8% 12% 4 8% 6% 5% 6% 4 5% 7% 35%	2601
	11th to 20th	Night	6% 9% 4 8% 5% 6% 5% 4 5% 6% 41%	2448
	21st to end	Night	8% 8% 2 7% 4 4 5% 5% 6% 8% 43%	1980
March	1st to 10th	Night	9% 8% 3 6% 4 3 3 3 5% 7% 48%	5287
	11th to 20th	Night	9% 6% 2 5% 4 3 4 3 6% 8% 51%	4980
	21st to end	Night	16% 12% 2 6% 4 4 5% 3 5% 6% 36%	5467
April	1st to 10th	Night	14% 7% 2 6% 4 4 4 3 6% 7% 42%	2068
	11th to 20th	Night	15% 8% 2 5% 4 3 3 4 6% 7% 43%	1792
	21st to end	Night	15% 8% 3 6% 4 3 4 4 4 6% 41%	1800
May	1st to 10th	Night	12% 5% 1 5% 3 4 3 3 5% 7% 52%	4080
	11th to 20th	Night	15% 6% 2 4 3 2 3 2 4 6% 53%	4053
	21st to end	Night	17% 6% 2 6% 4 3 4 3 4 8% 41%	3998
June	1st to 10th	Night	7% 4 2 4 3 3 4 4 5% 8% 55%	1400
	11th to 20th	Night	9% 5% 2 4 5% 4 4 3 6% 9% 49%	1400
	21st to end	Night	7% 2 2 3 3 3 4 4 6% 9% 56%	1400
July	1st to 10th	Night	6% 4 1 4 4 3 4 4 7% 10% 53%	3492
	11th to 20th	Night	7% 4 1 4 4 3 3 3 5% 7% 59%	3640
	21st to end	Night	6% 4 1 5% 4 4 4 4 8% 11% 51%	4138
August	1st to 10th	Night	9% 4 2 6% 4 4 5% 5% 8% 10% 44%	4011
	11th to 20th	Night	8% 4 2 5% 3 4 4 4 6% 8% 52%	4028
	21st to end	Night	6% 3 2 6% 4 4 4 3 5% 8% 55%	4487
September	1st to 10th	Night	9% 4 1 3 3 3 4 3 3 6% 61%	2094
	11th to 20th	Night	7% 4 2 4 4 3 4 3 5% 7% 58%	2200
	21st to end	Night	10% 4 2 4 4 3 3 2 4 5% 60%	2200
October	1st to 10th	Night	8% 3 1 3 2 2 2 2 4 5% 68%	3677
	11th to 20th	Night	9% 4 1 4 3 3 3 3 5% 7% 58%	3899
	21st to end	Night	9% 6% 2 6% 5% 4 4 4 5% 8% 48%	4578
November	1st to 10th	Night	7% 6% 2 5% 4 4 5% 4 5% 7% 51%	2665
	11th to 20th	Night	8% 7% 2 7% 5% 4 4 4 5% 6% 48%	2762
	21st to end	Night	7% 8% 2 5% 4 4 4 4 6% 8% 48%	2940
December	1st to 10th	Night	4 6% 4 9% 5% 5% 4 3 5% 6% 48%	4801
	11th to 20th	Night	7% 10% 4 9% 5% 5% 5% 4 6% 8% 39%	5714
	21st to end	Night	14% 10% 4 10% 5% 4 4 4 4 6% 34%	7534

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	61% 4 15% 14% 5%	3719
	11th to 20th	Day	50% 5% 14% 16% 15%	3720
	21st to end	Day	43% 7% 18% 20% 12%	4293
February	1st to 10th	Day	51% 8% 14% 16% 11%	1800
	11th to 20th	Day	47% 6% 14% 20% 11% 1	1867
	21st to end	Day	44% 8% 17% 18% 11% 2	1650
March	1st to 10th	Day	36% 5% 10% 30% 16% 2	4581
	11th to 20th	Day	30% 5% 10% 32% 20% 2	4980
	21st to end	Day	59% 7% 13% 17% 4 1	5464
April	1st to 10th	Day	41% 6% 14% 25% 12% 1	2330
	11th to 20th	Day	46% 7% 12% 22% 11% 3	2557
	21st to end	Day	44% 6% 13% 25% 11%	2600
May	1st to 10th	Day	30% 6% 10% 29% 25% 1	5900
	11th to 20th	Day	37% 6% 10% 21% 17% 8%	5866
	21st to end	Day	44% 6% 12% 26% 12% 1	6882
June	1st to 10th	Day	33% 7% 16% 31% 11% 2	3000
	11th to 20th	Day	35% 8% 16% 24% 16% 2	3000
	21st to end	Day	29% 8% 16% 30% 15% 3	3000
July	1st to 10th	Day	34% 3 18% 30% 13% 1	6413
	11th to 20th	Day	30% 3 12% 34% 18% 2	6265
	21st to end	Day	32% 5% 20% 26% 16% 2	6537
August	1st to 10th	Day	34% 5% 15% 29% 14% 3	4220
	11th to 20th	Day	44% 5% 15% 24% 11% 1	4210
	21st to end	Day	28% 5% 18% 29% 18% 2	4674
September	1st to 10th	Day	28% 5% 14% 31% 18% 3	2302
	11th to 20th	Day	29% 5% 16% 31% 18% 2	2200
	21st to end	Day	29% 5% 10% 32% 22% 3	2200
October	1st to 10th	Day	22% 3 9% 26% 35% 4	3468
	11th to 20th	Day	31% 4 12% 32% 19% 2	3240
	21st to end	Day	40% 3 14% 22% 20% 1	3208
November	1st to 10th	Day	35% 6% 17% 26% 13% 3	1853
	11th to 20th	Day	35% 6% 17% 26% 13% 2	1854
	21st to end	Day	40% 5% 16% 25% 12% 1	1680
December	1st to 10th	Day	49% 5% 16% 22% 7% 1	2607
	11th to 20th	Day	49% 5% 19% 19% 8%	2710
	21st to end	Day	54% 4 15% 22% 5%	3669
January	1st to 10th	Night	56% 7% 13% 17% 8%	6467
	11th to 20th	Night	43% 6% 17% 18% 16% 1	6480
	21st to end	Night	40% 7% 15% 23% 14%	6925
February	1st to 10th	Night	48% 6% 15% 19% 11% 1	2601
	11th to 20th	Night	43% 6% 13% 21% 13% 3	2449
	21st to end	Night	37% 8% 16% 24% 12% 4	1980
March	1st to 10th	Night	36% 5% 11% 28% 19% 2	5287
	11th to 20th	Night	31% 4 11% 32% 20% 1	4980
	21st to end	Night	49% 6% 12% 24% 8% 1	5467
April	1st to 10th	Night	41% 6% 14% 25% 13% 1	2068
	11th to 20th	Night	40% 7% 10% 23% 18% 3	1792
	21st to end	Night	43% 7% 11% 25% 13% 2	1800
May	1st to 10th	Night	31% 6% 13% 24% 23% 4	4080
	11th to 20th	Night	33% 5% 11% 20% 24% 7%	4054
	21st to end	Night	42% 7% 13% 26% 12% 1	3999
June	1st to 10th	Night	27% 7% 16% 28% 18% 4	1400
	11th to 20th	Night	31% 7% 17% 22% 20% 4	1400
	21st to end	Night	23% 7% 17% 31% 19% 3	1400
July	1st to 10th	Night	26% 4 21% 32% 15% 2	3452
	11th to 20th	Night	26% 3 12% 38% 19% 3	3592
	21st to end	Night	28% 4 24% 26% 16% 2	4020
August	1st to 10th	Night	32% 6% 18% 27% 13% 4	2916
	11th to 20th	Night	34% 5% 16% 31% 13% 1	2915
	21st to end	Night	28% 5% 17% 26% 20% 4	3234
September	1st to 10th	Night	25% 5% 14% 30% 22% 4	2094
	11th to 20th	Night	26% 5% 17% 31% 18% 3	2200
	21st to end	Night	28% 4 8% 30% 27% 3	2200
October	1st to 10th	Night	21% 3 7% 22% 42% 5%	3677
	11th to 20th	Night	26% 3 10% 34% 21% 6%	3899
	21st to end	Night	36% 4 15% 24% 20% 2	4578
November	1st to 10th	Night	32% 6% 14% 25% 19% 4	2665
	11th to 20th	Night	35% 6% 15% 24% 16% 3	2762
	21st to end	Night	35% 5% 17% 28% 15% 1	2940
December	1st to 10th	Night	38% 4 16% 31% 10% 1	4801
	11th to 20th	Night	45% 5% 18% 25% 7%	5716
	21st to end	Night	52% 4 15% 23% 7%	7534

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	14% 12% 29% 34% 9% 2	330
	11th to 20th	Day	12% 16% 36% 26% 8% 1	330
	21st to end	Day	14% 11% 39% 26% 8% 1	363
February	1st to 10th	Day	11% 17% 47% 23% 3	300
	11th to 20th	Day	12% 13% 41% 23% 9% 2	300
	21st to end	Day	15% 10% 42% 26% 6%	249
March	1st to 10th	Day	16% 13% 39% 27% 6%	300
	11th to 20th	Day	13% 10% 37% 26% 12% 1	300
	21st to end	Day	24% 12% 32% 20% 9% 3	330
April	1st to 10th	Day	22% 14% 36% 23% 5%	430
	11th to 20th	Day	22% 17% 32% 21% 8% 1	675
	21st to end	Day	21% 14% 30% 26% 8% 2	700
May	1st to 10th	Day	15% 12% 30% 29% 13% 1	703
	11th to 20th	Day	19% 9% 29% 26% 15% 2	725
	21st to end	Day	17% 9% 32% 27% 13% 3	789
June	1st to 10th	Day	9% 8% 26% 32% 19% 6%	730
	11th to 20th	Day	12% 9% 36% 28% 13% 2	730
	21st to end	Day	10% 8% 30% 37% 14% 1	730
July	1st to 10th	Day	7% 2 26% 39% 21% 5%	721
	11th to 20th	Day	6% 4 30% 40% 19% 2	718
	21st to end	Day	5% 3 25% 45% 19% 3	794
August	1st to 10th	Day	8% 4 24% 41% 21% 2	726
	11th to 20th	Day	11% 4 26% 38% 18% 3	715
	21st to end	Day	6% 5% 28% 35% 22% 2	803
September	1st to 10th	Day	10% 7% 30% 31% 18% 4	432
	11th to 20th	Day	11% 7% 34% 26% 19% 3	330
	21st to end	Day	13% 14% 29% 25% 14% 5%	330
October	1st to 10th	Day	15% 8% 30% 29% 14% 5%	330
	11th to 20th	Day	17% 13% 36% 24% 8% 1	330
	21st to end	Day	16% 20% 33% 20% 10% 1	363
November	1st to 10th	Day	18% 11% 31% 30% 8% 1	330
	11th to 20th	Day	10% 18% 42% 23% 8% 1	330
	21st to end	Day	14% 13% 36% 27% 8% 1	330
December	1st to 10th	Day	12% 14% 37% 28% 8% 1	330
	11th to 20th	Day	14% 14% 42% 24% 6%	330
	21st to end	Day	18% 13% 31% 30% 6% 1	363
January	1st to 10th	Night	11% 10% 38% 32% 8% 1	1050
	11th to 20th	Night	9% 14% 38% 32% 6% 1	1050
	21st to end	Night	10% 11% 41% 29% 8%	1155
February	1st to 10th	Night	14% 11% 40% 30% 5%	1001
	11th to 20th	Night	11% 10% 40% 31% 7% 1	894
	21st to end	Night	12% 10% 37% 31% 10% 1	660
March	1st to 10th	Night	11% 9% 43% 31% 5%	765
	11th to 20th	Night	14% 9% 38% 31% 7% 1	600
	21st to end	Night	18% 9% 33% 32% 8%	660
April	1st to 10th	Night	17% 11% 38% 30% 4	600
	11th to 20th	Night	19% 13% 34% 28% 6%	593
	21st to end	Night	18% 11% 33% 29% 8% 1	600
May	1st to 10th	Night	14% 8% 35% 31% 12%	600
	11th to 20th	Night	15% 8% 34% 33% 10% 1	591
	21st to end	Night	14% 7% 37% 30% 11% 1	650
June	1st to 10th	Night	10% 7% 27% 38% 18% 1	600
	11th to 20th	Night	9% 7% 36% 39% 10%	600
	21st to end	Night	7% 5% 29% 45% 13%	600
July	1st to 10th	Night	6% 3 25% 45% 21%	585
	11th to 20th	Night	4 2 28% 53% 12%	582
	21st to end	Night	4 2 27% 52% 14% 1	657
August	1st to 10th	Night	7% 4 25% 50% 14%	597
	11th to 20th	Night	8% 2 28% 40% 21% 1	594
	21st to end	Night	5% 3 29% 47% 15% 1	660
September	1st to 10th	Night	10% 6% 30% 38% 15% 2	600
	11th to 20th	Night	8% 4 35% 36% 15% 2	600
	21st to end	Night	10% 8% 33% 34% 15% 1	600
October	1st to 10th	Night	15% 8% 34% 33% 10% 1	648
	11th to 20th	Night	16% 10% 37% 27% 9%	800
	21st to end	Night	15% 12% 36% 30% 7%	1080
November	1st to 10th	Night	11% 8% 40% 32% 8% 1	1025
	11th to 20th	Night	10% 12% 37% 33% 8%	1050
	21st to end	Night	9% 10% 38% 34% 9%	1050
December	1st to 10th	Night	10% 12% 38% 32% 7%	1050
	11th to 20th	Night	12% 11% 37% 31% 8%	1050
	21st to end	Night	20% 10% 35% 29% 7%	1155

Page generated at 2026-01-29 00:21:43. Version ac07

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