Leadville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leadville clear sky chart from 2005-11-06 to 2026-09-14.

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	3 6% 3 9% 6% 5% 5% 4 6% 7% 45%	157855
	Night	1 4 3 8% 5% 5% 5% 4 6% 8% 52%	150850
Transparency	Day	33% 9% 12% 21% 18% 7%	152782
	Night	25% 9% 15% 25% 20% 6%	146932
Seeing	Day	16% 24% 29% 19% 9% 2	18073
	Night	8% 19% 31% 28% 13% 1	28044

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	3 5% 15% 9% 7% 5% 3 5% 7% 41%	4720
	11th to 20th	Day	1 2 11% 7% 8% 6% 2 4 5% 54%	5236
	21st to end	Day	3 4 12% 5% 8% 5% 3 4 6% 51%	5844
February	1st to 10th	Day	3 4 16% 8% 7% 6% 3 6% 5% 42%	1890
	11th to 20th	Day	5% 5% 12% 8% 7% 6% 3 6% 6% 42%	1958
	21st to end	Day	4 3 15% 8% 7% 5% 4 4 6% 46%	1730
March	1st to 10th	Day	4 4 18% 6% 5% 3 3 4 5% 47%	4777
	11th to 20th	Day	6% 7% 18% 7% 4 4 3 5% 7% 37%	5110
	21st to end	Day	1 10% 8% 14% 6% 5% 4 3 5% 6% 38%	5816
April	1st to 10th	Day	1 8% 4 9% 6% 6% 5% 4 6% 7% 45%	2520
	11th to 20th	Day	1 10% 5% 12% 7% 7% 5% 4 6% 5% 38%	2491
	21st to end	Day	2 11% 5% 10% 8% 6% 6% 5% 6% 6% 36%	2520
May	1st to 10th	Day	1 11% 6% 10% 6% 6% 6% 5% 8% 8% 33%	7315
	11th to 20th	Day	2 11% 3 8% 5% 5% 6% 4 6% 7% 43%	8191
	21st to end	Day	2 6% 3 6% 5% 5% 6% 5% 7% 8% 45%	9026
June	1st to 10th	Day	4 5% 2 6% 5% 5% 5% 5% 7% 9% 46%	2940
	11th to 20th	Day	4 5% 2 6% 4 4 5% 3 5% 6% 55%	2940
	21st to end	Day	4 5% 2 6% 5% 5% 6% 5% 6% 7% 51%	2940
July	1st to 10th	Day	4 4 2 5% 4 5% 5% 4 6% 7% 54%	8249
	11th to 20th	Day	5% 5% 2 7% 6% 7% 7% 6% 8% 9% 37%	8250
	21st to end	Day	8% 6% 2 9% 7% 7% 6% 5% 6% 7% 37%	8370
August	1st to 10th	Day	6% 5% 2 6% 5% 5% 6% 5% 7% 10% 42%	7549
	11th to 20th	Day	7% 6% 3 8% 6% 6% 6% 5% 6% 8% 39%	7173
	21st to end	Day	7% 9% 3 10% 7% 6% 6% 5% 6% 8% 32%	7751
September	1st to 10th	Day	8% 6% 2 6% 5% 5% 4 4 5% 6% 49%	2520
	11th to 20th	Day	7% 7% 2 7% 5% 4 5% 3 4 6% 48%	2437
	21st to end	Day	5% 8% 2 6% 5% 3 4 3 4 5% 56%	2152
October	1st to 10th	Day	3 5% 2 4 3 3 2 2 4 5% 67%	3270
	11th to 20th	Day	3 8% 2 6% 4 4 5% 4 6% 8% 49%	3250
	21st to end	Day	1 4 3 7% 3 3 3 2 4 6% 63%	3548
November	1st to 10th	Day	5% 3 5% 4 3 4 3 5% 6% 62%	1873
	11th to 20th	Day	5% 2 7% 3 4 3 2 5% 7% 63%	1890
	21st to end	Day	5% 3 8% 6% 4 3 3 5% 7% 56%	1711
December	1st to 10th	Day	2 3 7% 6% 7% 4 3 4 6% 60%	2700
	11th to 20th	Day	4 3 9% 4 3 3 3 5% 8% 58%	3106
	21st to end	Day	3 4 14% 7% 5% 4 3 6% 9% 44%	4092
January	1st to 10th	Night	2 4 14% 10% 6% 4 4 5% 8% 43%	8201
	11th to 20th	Night	1 2 11% 9% 7% 6% 2 4 5% 53%	7812
	21st to end	Night	2 3 11% 7% 6% 6% 4 6% 7% 49%	8370
February	1st to 10th	Night	3 3 10% 8% 6% 6% 4 6% 8% 48%	2730
	11th to 20th	Night	3 2 10% 8% 7% 7% 5% 6% 7% 43%	2548
	21st to end	Night	4 3 9% 7% 6% 5% 5% 6% 7% 48%	2076
March	1st to 10th	Night	4 6% 14% 6% 5% 4 3 5% 7% 45%	5322
	11th to 20th	Night	6% 5% 14% 7% 4 4 3 5% 7% 44%	5110
	21st to end	Night	1 7% 6% 14% 7% 5% 5% 4 6% 7% 39%	5389
April	1st to 10th	Night	1 4 2 6% 6% 4 5% 5% 6% 9% 52%	2100
	11th to 20th	Night	1 7% 3 7% 6% 5% 4 4 6% 8% 48%	2077
	21st to end	Night	2 7% 3 6% 4 5% 5% 4 6% 8% 51%	2100
May	1st to 10th	Night	1 9% 4 9% 5% 4 5% 5% 8% 10% 42%	5612
	11th to 20th	Night	1 8% 4 9% 4 4 5% 4 6% 8% 47%	4701
	21st to end	Night	2 5% 2 6% 3 4 3 3 6% 9% 56%	5181
June	1st to 10th	Night	2 4 1 4 3 3 3 4 5% 9% 62%	1680
	11th to 20th	Night	3 4 1 3 3 3 3 4 4 7% 65%	1680
	21st to end	Night	3 4 1 3 3 3 3 4 6% 9% 61%	1680
July	1st to 10th	Night	2 3 1 4 3 3 4 4 6% 8% 62%	4740
	11th to 20th	Night	1 2 1 3 4 4 5% 5% 9% 12% 53%	4740
	21st to end	Night	3 4 2 5% 4 5% 6% 5% 10% 12% 44%	5722
August	1st to 10th	Night	2 3 1 4 3 3 4 4 7% 10% 58%	5273
	11th to 20th	Night	3 3 1 4 3 4 5% 4 8% 13% 52%	5683
	21st to end	Night	3 5% 2 7% 5% 6% 7% 6% 9% 12% 39%	6465
September	1st to 10th	Night	4 3 2 6% 4 4 3 4 6% 9% 56%	2100
	11th to 20th	Night	4 5% 2 5% 4 4 3 3 5% 7% 60%	2030
	21st to end	Night	2 4 2 4 4 3 4 3 6% 6% 62%	2243
October	1st to 10th	Night	2 4 1 3 2 3 2 2 4 4 74%	3920
	11th to 20th	Night	1 6% 2 5% 3 3 3 3 6% 6% 60%	3898
	21st to end	Night	1 4 2 6% 3 2 3 2 3 6% 68%	4252
November	1st to 10th	Night	3 2 5% 3 3 3 3 5% 6% 66%	2623
	11th to 20th	Night	2 1 6% 5% 4 4 3 5% 8% 62%	2730
	21st to end	Night	4 3 7% 4 5% 5% 4 5% 8% 55%	2903
December	1st to 10th	Night	2 2 6% 5% 5% 4 3 3 6% 66%	4710
	11th to 20th	Night	3 2 8% 5% 5% 4 4 5% 8% 57%	5321
	21st to end	Night	5% 6% 14% 6% 6% 5% 4 6% 8% 41%	7128

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	34% 12% 10% 25% 14% 5%	4723
	11th to 20th	Day	22% 16% 14% 21% 20% 7%	5236
	21st to end	Day	30% 8% 8% 23% 21% 10%	5844
February	1st to 10th	Day	38% 8% 15% 18% 14% 6%	1890
	11th to 20th	Day	35% 10% 11% 21% 17% 6%	1967
	21st to end	Day	35% 8% 11% 19% 20% 8%	1730
March	1st to 10th	Day	32% 8% 7% 20% 21% 11%	4777
	11th to 20th	Day	38% 12% 10% 25% 13% 2	5110
	21st to end	Day	38% 13% 14% 25% 10% 1	5816
April	1st to 10th	Day	35% 8% 13% 21% 17% 6%	2520
	11th to 20th	Day	42% 8% 13% 18% 16% 3	2494
	21st to end	Day	42% 9% 13% 23% 11% 2	2520
May	1st to 10th	Day	39% 11% 13% 21% 15% 1	7315
	11th to 20th	Day	34% 9% 11% 24% 20% 2	8195
	21st to end	Day	30% 8% 13% 25% 21% 3	9027
June	1st to 10th	Day	30% 9% 13% 23% 20% 5%	2940
	11th to 20th	Day	27% 7% 9% 19% 25% 14%	2940
	21st to end	Day	30% 7% 10% 18% 23% 13%	2940
July	1st to 10th	Day	26% 7% 5% 14% 23% 26%	8181
	11th to 20th	Day	37% 9% 12% 20% 15% 7%	8175
	21st to end	Day	44% 7% 15% 13% 12% 9%	8184
August	1st to 10th	Day	40% 7% 13% 15% 14% 11%	5978
	11th to 20th	Day	44% 8% 16% 14% 13% 5%	5655
	21st to end	Day	46% 7% 16% 15% 13% 4	6078
September	1st to 10th	Day	34% 6% 10% 17% 22% 10%	2520
	11th to 20th	Day	34% 7% 11% 18% 23% 8%	2437
	21st to end	Day	30% 5% 9% 23% 27% 6%	2152
October	1st to 10th	Day	19% 5% 6% 23% 36% 11%	3270
	11th to 20th	Day	31% 5% 10% 29% 19% 5%	3250
	21st to end	Day	22% 5% 8% 32% 30% 4	3548
November	1st to 10th	Day	22% 5% 14% 24% 31% 5%	1873
	11th to 20th	Day	19% 6% 14% 30% 22% 7%	1890
	21st to end	Day	27% 6% 11% 27% 19% 10%	1711
December	1st to 10th	Day	23% 8% 10% 36% 17% 6%	2700
	11th to 20th	Day	22% 7% 15% 32% 21% 2	3104
	21st to end	Day	30% 11% 13% 16% 23% 6%	4092
January	1st to 10th	Night	32% 11% 11% 28% 15% 5%	8202
	11th to 20th	Night	21% 16% 13% 24% 19% 8%	7812
	21st to end	Night	26% 9% 9% 21% 24% 10%	8370
February	1st to 10th	Night	29% 8% 16% 24% 17% 5%	2730
	11th to 20th	Night	31% 10% 15% 22% 19% 5%	2549
	21st to end	Night	28% 9% 13% 22% 21% 7%	2076
March	1st to 10th	Night	29% 12% 10% 18% 24% 8%	5322
	11th to 20th	Night	32% 10% 11% 21% 23% 3	5110
	21st to end	Night	33% 14% 19% 26% 7% 1	5389
April	1st to 10th	Night	22% 10% 18% 26% 20% 4	2100
	11th to 20th	Night	29% 9% 15% 28% 17% 2	2077
	21st to end	Night	27% 9% 18% 29% 16% 1	2100
May	1st to 10th	Night	29% 10% 18% 28% 13% 1	5610
	11th to 20th	Night	30% 8% 14% 30% 17%	4702
	21st to end	Night	21% 8% 17% 30% 23% 2	5182
June	1st to 10th	Night	17% 9% 15% 31% 22% 6%	1680
	11th to 20th	Night	18% 7% 12% 20% 31% 13%	1680
	21st to end	Night	17% 7% 12% 23% 26% 15%	1680
July	1st to 10th	Night	19% 6% 7% 16% 31% 21%	4700
	11th to 20th	Night	20% 7% 22% 29% 17% 5%	4692
	21st to end	Night	27% 11% 26% 18% 10% 7%	5596
August	1st to 10th	Night	23% 8% 20% 23% 16% 9%	4168
	11th to 20th	Night	25% 11% 29% 16% 13% 6%	4477
	21st to end	Night	32% 9% 29% 14% 14% 2	5069
September	1st to 10th	Night	24% 8% 14% 22% 24% 8%	2100
	11th to 20th	Night	23% 6% 15% 24% 24% 9%	2030
	21st to end	Night	21% 6% 12% 30% 26% 5%	2243
October	1st to 10th	Night	14% 5% 8% 30% 35% 9%	3920
	11th to 20th	Night	22% 5% 13% 35% 19% 5%	3898
	21st to end	Night	18% 5% 8% 33% 30% 6%	4252
November	1st to 10th	Night	18% 7% 13% 27% 29% 6%	2623
	11th to 20th	Night	17% 9% 14% 30% 24% 7%	2730
	21st to end	Night	25% 7% 12% 27% 21% 9%	2903
December	1st to 10th	Night	17% 8% 12% 37% 21% 5%	4710
	11th to 20th	Night	20% 9% 13% 31% 25% 3	5322
	21st to end	Night	34% 12% 11% 18% 18% 7%	7128

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	21% 29% 26% 18% 5% 1	330
	11th to 20th	Day	24% 35% 22% 15% 4	330
	21st to end	Day	17% 34% 31% 13% 5% 1	363
February	1st to 10th	Day	29% 39% 22% 8% 2 1	330
	11th to 20th	Day	32% 32% 24% 9% 2	330
	21st to end	Day	34% 33% 24% 9%	273
March	1st to 10th	Day	22% 35% 24% 16% 4	403
	11th to 20th	Day	24% 31% 29% 12% 4	540
	21st to end	Day	21% 39% 29% 9% 1	594
April	1st to 10th	Day	18% 39% 30% 9% 3 1	540
	11th to 20th	Day	26% 36% 27% 10% 1	532
	21st to end	Day	16% 41% 30% 9% 3 1	540
May	1st to 10th	Day	21% 33% 28% 13% 4 1	559
	11th to 20th	Day	15% 21% 34% 20% 8% 2	775
	21st to end	Day	14% 21% 31% 24% 9% 1	844
June	1st to 10th	Day	9% 18% 31% 23% 17% 2	780
	11th to 20th	Day	11% 22% 33% 21% 12% 2	780
	21st to end	Day	9% 19% 32% 22% 16% 2	780
July	1st to 10th	Day	9% 11% 28% 29% 20% 3	771
	11th to 20th	Day	9% 7% 24% 31% 23% 5%	768
	21st to end	Day	15% 11% 25% 30% 16% 3	646
August	1st to 10th	Day	13% 15% 34% 23% 12% 3	567
	11th to 20th	Day	10% 12% 33% 26% 15% 4	557
	21st to end	Day	11% 13% 30% 30% 13% 3	627
September	1st to 10th	Day	12% 15% 31% 25% 12% 4	570
	11th to 20th	Day	11% 19% 39% 20% 9% 3	543
	21st to end	Day	12% 18% 31% 24% 11% 5%	365
October	1st to 10th	Day	13% 20% 24% 22% 18% 3	330
	11th to 20th	Day	23% 26% 27% 14% 8% 2	330
	21st to end	Day	18% 29% 29% 15% 7% 1	363
November	1st to 10th	Day	20% 32% 25% 14% 7% 1	330
	11th to 20th	Day	19% 27% 33% 15% 5% 1	330
	21st to end	Day	14% 31% 35% 17% 3	330
December	1st to 10th	Day	26% 32% 22% 12% 8% 1	330
	11th to 20th	Day	24% 35% 25% 10% 5% 1	330
	21st to end	Day	26% 32% 28% 10% 4 1	363
January	1st to 10th	Night	12% 28% 30% 20% 8% 1	1050
	11th to 20th	Night	14% 26% 33% 19% 7% 1	898
	21st to end	Night	6% 26% 41% 20% 6% 1	924
February	1st to 10th	Night	11% 29% 40% 16% 4	840
	11th to 20th	Night	11% 32% 36% 18% 4	824
	21st to end	Night	11% 30% 42% 15% 2	692
March	1st to 10th	Night	8% 26% 35% 25% 5%	840
	11th to 20th	Night	7% 21% 41% 23% 9%	840
	21st to end	Night	6% 27% 40% 22% 4	832
April	1st to 10th	Night	9% 26% 38% 23% 4	630
	11th to 20th	Night	8% 26% 38% 23% 6%	623
	21st to end	Night	8% 19% 38% 27% 7% 1	630
May	1st to 10th	Night	8% 13% 41% 26% 11%	630
	11th to 20th	Night	8% 10% 32% 35% 14% 1	621
	21st to end	Night	7% 13% 29% 34% 15% 2	683
June	1st to 10th	Night	5% 8% 27% 38% 21% 1	630
	11th to 20th	Night	6% 11% 30% 38% 13% 1	630
	21st to end	Night	4 6% 24% 40% 25% 2	630
July	1st to 10th	Night	6% 2 17% 40% 31% 4	615
	11th to 20th	Night	3 2 11% 40% 41% 3	612
	21st to end	Night	7% 2 10% 38% 40% 4	690
August	1st to 10th	Night	7% 1 13% 42% 34% 3	627
	11th to 20th	Night	6% 3 14% 41% 33% 3	624
	21st to end	Night	5% 2 14% 42% 32% 3	693
September	1st to 10th	Night	5% 3 17% 45% 25% 4	630
	11th to 20th	Night	6% 5% 21% 44% 21% 3	609
	21st to end	Night	4 10% 26% 34% 22% 4	679
October	1st to 10th	Night	5% 15% 29% 31% 16% 4	800
	11th to 20th	Night	8% 18% 33% 26% 13% 2	800
	21st to end	Night	7% 19% 35% 27% 10% 2	880
November	1st to 10th	Night	7% 23% 37% 24% 8% 1	983
	11th to 20th	Night	10% 26% 36% 21% 5% 1	1050
	21st to end	Night	8% 24% 33% 28% 7%	1050
December	1st to 10th	Night	9% 31% 34% 19% 6%	1050
	11th to 20th	Night	11% 29% 36% 18% 6%	1050
	21st to end	Night	13% 28% 36% 19% 4 1	1155

Page generated at 2026-09-11 02:11:56. Version ac07

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