Breckenridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Breckenridge clear sky chart from 2005-11-06 to 2025-07-06.

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 10% 6% 6% 5% 4 5% 7% 44%	123976
	Night	1 4 2 8% 6% 5% 5% 4 6% 8% 51%	123738
Transparency	Day	35% 7% 11% 21% 19% 7%	123726
	Night	26% 8% 14% 25% 20% 6%	123576
Seeing	Day	16% 24% 29% 20% 10% 2	16442
	Night	7% 19% 31% 29% 13% 1	26507

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	2 3 16% 13% 10% 5% 2 3 5% 40%	3638
	11th to 20th	Day	2 4 14% 9% 11% 8% 4 4 5% 39%	3939
	21st to end	Day	4 4 14% 6% 6% 5% 3 4 7% 47%	4510
February	1st to 10th	Day	4 5% 15% 8% 6% 5% 4 6% 6% 42%	1800
	11th to 20th	Day	4 4 14% 7% 6% 5% 4 5% 6% 45%	1872
	21st to end	Day	4 4 15% 9% 7% 5% 3 5% 6% 43%	1650
March	1st to 10th	Day	5% 5% 17% 6% 5% 3 2 4 5% 48%	4624
	11th to 20th	Day	7% 6% 16% 8% 6% 4 4 5% 7% 36%	5000
	21st to end	Day	9% 7% 16% 7% 6% 5% 4 5% 6% 35%	5705
April	1st to 10th	Day	1 8% 4 10% 6% 6% 5% 4 6% 5% 45%	2400
	11th to 20th	Day	2 11% 7% 14% 7% 6% 4 2 6% 6% 35%	2371
	21st to end	Day	2 13% 5% 12% 7% 5% 5% 4 6% 6% 34%	2400
May	1st to 10th	Day	3 14% 6% 14% 7% 6% 5% 4 6% 6% 30%	5682
	11th to 20th	Day	3 11% 3 9% 5% 6% 6% 5% 6% 8% 37%	6298
	21st to end	Day	3 7% 2 6% 5% 5% 5% 5% 7% 9% 45%	6925
June	1st to 10th	Day	5% 7% 3 7% 4 5% 6% 4 7% 9% 44%	2800
	11th to 20th	Day	6% 6% 2 6% 4 5% 5% 4 6% 6% 51%	2800
	21st to end	Day	5% 5% 2 7% 5% 5% 6% 5% 6% 7% 48%	2800
July	1st to 10th	Day	5% 5% 2 6% 5% 4 4 3 5% 5% 55%	4501
	11th to 20th	Day	5% 5% 2 6% 6% 6% 6% 6% 8% 10% 39%	4430
	21st to end	Day	8% 6% 2 7% 5% 5% 5% 4 6% 7% 44%	4554
August	1st to 10th	Day	10% 7% 3 9% 6% 7% 6% 6% 7% 9% 30%	4092
	11th to 20th	Day	7% 6% 3 8% 6% 6% 6% 5% 7% 8% 40%	3797
	21st to end	Day	7% 7% 2 8% 6% 6% 6% 5% 7% 7% 40%	4180
September	1st to 10th	Day	8% 6% 3 7% 4 5% 4 3 4 5% 51%	2280
	11th to 20th	Day	8% 6% 2 7% 4 4 4 3 5% 7% 50%	2280
	21st to end	Day	5% 7% 2 7% 4 4 3 2 4 6% 56%	2054
October	1st to 10th	Day	3 4 1 4 3 3 3 2 4 6% 67%	3170
	11th to 20th	Day	3 7% 2 6% 4 6% 6% 5% 7% 8% 47%	3150
	21st to end	Day	1 6% 2 9% 4 3 3 2 4 6% 60%	3421
November	1st to 10th	Day	5% 2 7% 4 3 3 4 5% 6% 60%	1763
	11th to 20th	Day	5% 2 7% 4 4 3 3 5% 8% 60%	1800
	21st to end	Day	4 4 9% 6% 4 4 4 4 7% 56%	1640
December	1st to 10th	Day	2 2 9% 6% 7% 5% 2 3 6% 58%	2620
	11th to 20th	Day	3 2 10% 5% 4 4 3 5% 8% 57%	3026
	21st to end	Day	4 3 14% 8% 6% 6% 4 6% 8% 42%	4004
January	1st to 10th	Night	1 2 14% 13% 7% 4 3 5% 6% 42%	6327
	11th to 20th	Night	1 2 11% 10% 10% 8% 3 4 7% 43%	6082
	21st to end	Night	2 3 12% 8% 7% 6% 4 5% 6% 47%	6468
February	1st to 10th	Night	1 2 11% 8% 6% 5% 6% 7% 8% 45%	2600
	11th to 20th	Night	3 2 10% 8% 6% 7% 5% 7% 8% 44%	2414
	21st to end	Night	3 3 10% 7% 7% 6% 4 7% 8% 46%	1980
March	1st to 10th	Night	4 6% 12% 7% 5% 5% 4 6% 6% 45%	5252
	11th to 20th	Night	5% 5% 13% 7% 4 4 3 5% 7% 47%	5000
	21st to end	Night	1 6% 4 16% 7% 6% 5% 4 6% 7% 38%	5260
April	1st to 10th	Night	4 2 7% 6% 5% 6% 4 6% 8% 52%	2000
	11th to 20th	Night	1 9% 3 9% 7% 5% 5% 4 5% 7% 45%	1977
	21st to end	Night	2 9% 3 8% 5% 3 4 3 5% 8% 49%	2000
May	1st to 10th	Night	1 10% 5% 8% 5% 5% 6% 4 7% 8% 40%	4268
	11th to 20th	Night	2 8% 3 11% 5% 5% 5% 4 7% 8% 42%	3617
	21st to end	Night	1 4 2 5% 3 4 5% 4 5% 8% 58%	3972
June	1st to 10th	Night	2 4 1 4 3 4 4 5% 7% 9% 59%	1600
	11th to 20th	Night	3 3 1 4 2 3 4 3 5% 6% 65%	1600
	21st to end	Night	2 3 1 5% 3 3 3 3 7% 8% 61%	1600
July	1st to 10th	Night	3 3 1 4 4 4 4 4 7% 8% 58%	2580
	11th to 20th	Night	2 3 1 3 3 4 6% 5% 9% 12% 53%	2540
	21st to end	Night	3 3 1 4 3 4 5% 5% 9% 9% 54%	3005
August	1st to 10th	Night	4 4 2 6% 4 5% 7% 5% 9% 12% 43%	2847
	11th to 20th	Night	3 3 1 3 3 4 5% 5% 8% 11% 54%	3042
	21st to end	Night	3 3 2 5% 3 5% 7% 6% 8% 11% 48%	3487
September	1st to 10th	Night	3 4 2 5% 3 4 4 4 6% 8% 57%	1900
	11th to 20th	Night	3 4 2 4 3 4 4 3 5% 7% 62%	1900
	21st to end	Night	2 4 2 5% 4 4 4 3 4 7% 61%	2121
October	1st to 10th	Night	2 3 1 2 2 2 3 3 4 5% 73%	3800
	11th to 20th	Night	1 3 2 3 4 4 4 4 6% 8% 62%	3778
	21st to end	Night	1 4 2 6% 3 3 2 2 4 6% 67%	4120
November	1st to 10th	Night	3 2 5% 4 3 3 4 5% 7% 63%	2519
	11th to 20th	Night	3 2 7% 4 4 4 2 6% 7% 60%	2600
	21st to end	Night	4 2 8% 6% 4 4 4 6% 8% 54%	2757
December	1st to 10th	Night	1 1 6% 6% 5% 4 2 5% 6% 65%	4570
	11th to 20th	Night	2 2 6% 6% 4 5% 3 5% 9% 57%	5181
	21st to end	Night	5% 4 14% 9% 6% 5% 4 6% 8% 39%	6974

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	36% 11% 12% 19% 16% 6%	3639
	11th to 20th	Day	40% 12% 11% 16% 17% 4	3939
	21st to end	Day	34% 7% 11% 21% 19% 9%	4510
February	1st to 10th	Day	38% 8% 16% 18% 13% 7%	1800
	11th to 20th	Day	36% 6% 13% 21% 17% 7%	1881
	21st to end	Day	38% 5% 12% 18% 18% 7%	1650
March	1st to 10th	Day	35% 6% 6% 20% 21% 12%	4624
	11th to 20th	Day	40% 11% 9% 23% 15% 2	5000
	21st to end	Day	46% 5% 13% 25% 10% 1	5705
April	1st to 10th	Day	38% 7% 13% 21% 16% 6%	2400
	11th to 20th	Day	48% 4 12% 16% 16% 3	2374
	21st to end	Day	47% 7% 10% 25% 11% 1	2400
May	1st to 10th	Day	47% 7% 10% 19% 15% 2	5682
	11th to 20th	Day	37% 10% 12% 22% 17% 2	6302
	21st to end	Day	31% 6% 12% 23% 25% 3	6926
June	1st to 10th	Day	34% 7% 13% 24% 18% 5%	2800
	11th to 20th	Day	32% 6% 9% 18% 23% 13%	2800
	21st to end	Day	32% 6% 8% 18% 23% 11%	2800
July	1st to 10th	Day	28% 6% 7% 12% 21% 26%	4432
	11th to 20th	Day	34% 8% 13% 20% 16% 9%	4355
	21st to end	Day	35% 8% 11% 14% 15% 16%	4410
August	1st to 10th	Day	46% 9% 15% 12% 14% 3	4078
	11th to 20th	Day	41% 7% 12% 13% 19% 8%	3834
	21st to end	Day	39% 7% 10% 16% 21% 6%	4179
September	1st to 10th	Day	35% 4 8% 15% 27% 11%	2280
	11th to 20th	Day	34% 5% 10% 17% 25% 8%	2280
	21st to end	Day	30% 4 7% 25% 28% 6%	2054
October	1st to 10th	Day	20% 3 7% 25% 36% 9%	3170
	11th to 20th	Day	29% 4 13% 30% 19% 5%	3150
	21st to end	Day	25% 5% 7% 31% 28% 4	3421
November	1st to 10th	Day	23% 6% 13% 22% 31% 5%	1763
	11th to 20th	Day	21% 6% 16% 28% 21% 8%	1800
	21st to end	Day	27% 5% 12% 28% 18% 10%	1640
December	1st to 10th	Day	25% 9% 10% 34% 18% 5%	2620
	11th to 20th	Day	24% 7% 15% 32% 20% 2	3024
	21st to end	Day	33% 8% 14% 17% 23% 5%	4004
January	1st to 10th	Night	33% 11% 12% 22% 16% 6%	6327
	11th to 20th	Night	32% 13% 12% 20% 16% 7%	6082
	21st to end	Night	28% 9% 12% 20% 22% 9%	6468
February	1st to 10th	Night	29% 11% 17% 21% 17% 5%	2600
	11th to 20th	Night	30% 8% 16% 23% 19% 5%	2415
	21st to end	Night	30% 6% 16% 20% 21% 8%	1980
March	1st to 10th	Night	30% 10% 9% 20% 22% 9%	5252
	11th to 20th	Night	28% 12% 9% 22% 26% 3	5000
	21st to end	Night	39% 7% 20% 26% 7% 1	5260
April	1st to 10th	Night	26% 9% 16% 25% 20% 4	2000
	11th to 20th	Night	34% 6% 15% 26% 17% 2	1977
	21st to end	Night	30% 7% 16% 31% 15% 1	2000
May	1st to 10th	Night	35% 7% 15% 27% 15% 2	4265
	11th to 20th	Night	29% 11% 16% 27% 16%	3618
	21st to end	Night	20% 6% 15% 32% 25% 2	3972
June	1st to 10th	Night	19% 8% 18% 31% 18% 5%	1600
	11th to 20th	Night	19% 6% 12% 22% 27% 14%	1600
	21st to end	Night	19% 6% 13% 24% 26% 12%	1600
July	1st to 10th	Night	22% 8% 10% 20% 20% 21%	2540
	11th to 20th	Night	20% 6% 20% 31% 16% 7%	2492
	21st to end	Night	21% 9% 20% 27% 9% 15%	2911
August	1st to 10th	Night	31% 9% 24% 19% 13% 4	2838
	11th to 20th	Night	23% 8% 27% 16% 18% 9%	3071
	21st to end	Night	27% 8% 19% 20% 23% 3	3487
September	1st to 10th	Night	23% 7% 13% 22% 26% 8%	1900
	11th to 20th	Night	21% 7% 13% 24% 25% 10%	1900
	21st to end	Night	22% 6% 11% 32% 25% 5%	2121
October	1st to 10th	Night	13% 5% 8% 31% 35% 8%	3800
	11th to 20th	Night	17% 5% 14% 41% 18% 5%	3778
	21st to end	Night	18% 5% 8% 31% 32% 6%	4120
November	1st to 10th	Night	19% 7% 14% 26% 27% 6%	2519
	11th to 20th	Night	20% 6% 15% 30% 23% 7%	2600
	21st to end	Night	25% 5% 13% 28% 21% 8%	2757
December	1st to 10th	Night	17% 9% 12% 36% 21% 4	4570
	11th to 20th	Night	22% 8% 13% 29% 26% 3	5182
	21st to end	Night	34% 11% 12% 18% 18% 6%	6974

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	20% 30% 21% 19% 8% 2	300
	11th to 20th	Day	17% 33% 30% 17% 3 1	300
	21st to end	Day	13% 37% 30% 14% 5% 1	330
February	1st to 10th	Day	27% 37% 25% 8% 1 1	300
	11th to 20th	Day	26% 36% 26% 10% 2	300
	21st to end	Day	30% 31% 27% 12%	249
March	1st to 10th	Day	22% 32% 26% 16% 4	346
	11th to 20th	Day	17% 31% 31% 17% 3 1	500
	21st to end	Day	18% 40% 29% 11% 2	550
April	1st to 10th	Day	19% 40% 28% 10% 2 1	500
	11th to 20th	Day	25% 37% 25% 10% 2 1	492
	21st to end	Day	18% 35% 34% 10% 2 1	500
May	1st to 10th	Day	21% 30% 30% 16% 4 1	548
	11th to 20th	Day	15% 18% 33% 23% 9% 1	725
	21st to end	Day	15% 20% 29% 23% 11% 2	789
June	1st to 10th	Day	10% 18% 27% 25% 17% 3	730
	11th to 20th	Day	12% 19% 30% 25% 12% 2	730
	21st to end	Day	8% 18% 30% 25% 16% 2	730
July	1st to 10th	Day	10% 9% 26% 30% 22% 4	697
	11th to 20th	Day	9% 8% 25% 29% 22% 6%	668
	21st to end	Day	13% 10% 27% 26% 19% 5%	592
August	1st to 10th	Day	15% 13% 29% 26% 13% 3	487
	11th to 20th	Day	11% 10% 32% 27% 15% 5%	477
	21st to end	Day	12% 12% 30% 29% 13% 4	539
September	1st to 10th	Day	12% 15% 29% 26% 12% 6%	490
	11th to 20th	Day	12% 16% 36% 24% 11% 2	490
	21st to end	Day	11% 22% 26% 22% 14% 6%	323
October	1st to 10th	Day	12% 21% 27% 21% 16% 4	300
	11th to 20th	Day	16% 28% 25% 18% 10% 2	300
	21st to end	Day	20% 28% 25% 18% 7% 1	330
November	1st to 10th	Day	17% 33% 28% 15% 6% 1	300
	11th to 20th	Day	21% 30% 29% 13% 6% 2	300
	21st to end	Day	10% 30% 39% 16% 4	300
December	1st to 10th	Day	18% 32% 27% 15% 7% 1	300
	11th to 20th	Day	18% 32% 33% 12% 4 1	300
	21st to end	Day	22% 32% 28% 12% 5%	330
January	1st to 10th	Night	10% 28% 30% 21% 9% 1	1000
	11th to 20th	Night	12% 29% 32% 20% 7% 1	885
	21st to end	Night	4 25% 43% 20% 6% 1	880
February	1st to 10th	Night	8% 31% 39% 17% 5% 1	800
	11th to 20th	Night	7% 32% 37% 21% 3	784
	21st to end	Night	6% 33% 38% 19% 3	660
March	1st to 10th	Night	6% 24% 37% 27% 5%	800
	11th to 20th	Night	6% 21% 36% 29% 8%	800
	21st to end	Night	6% 23% 43% 23% 4	780
April	1st to 10th	Night	7% 23% 43% 24% 4	600
	11th to 20th	Night	8% 24% 35% 25% 7%	593
	21st to end	Night	7% 20% 35% 29% 8% 1	600
May	1st to 10th	Night	9% 13% 39% 29% 9% 1	600
	11th to 20th	Night	8% 11% 29% 38% 14% 1	591
	21st to end	Night	7% 14% 27% 35% 15% 1	650
June	1st to 10th	Night	4 8% 27% 40% 20% 2	600
	11th to 20th	Night	5% 10% 27% 46% 12% 1	600
	21st to end	Night	4 6% 22% 41% 27% 1	600
July	1st to 10th	Night	5% 2 15% 39% 36% 3	570
	11th to 20th	Night	3 1 10% 42% 40% 5%	552
	21st to end	Night	5% 2 10% 37% 42% 4	624
August	1st to 10th	Night	9% 2 14% 38% 35% 3	567
	11th to 20th	Night	5% 2 15% 43% 30% 4	564
	21st to end	Night	6% 2 14% 42% 32% 4	627
September	1st to 10th	Night	4 3 15% 48% 26% 4	570
	11th to 20th	Night	5% 3 22% 45% 23% 3	570
	21st to end	Night	4 9% 24% 38% 21% 4	625
October	1st to 10th	Night	3 14% 32% 34% 14% 4	760
	11th to 20th	Night	6% 20% 30% 30% 13% 1	760
	21st to end	Night	6% 18% 35% 29% 10% 2	836
November	1st to 10th	Night	5% 23% 35% 28% 8% 1	959
	11th to 20th	Night	8% 27% 35% 24% 5% 2	1000
	21st to end	Night	4 24% 37% 28% 6% 1	1000
December	1st to 10th	Night	7% 29% 36% 21% 6%	1000
	11th to 20th	Night	8% 30% 35% 20% 6% 1	1000
	21st to end	Night	12% 28% 35% 20% 5% 1	1100

Page generated at 2025-07-02 23:30:15. Version ac07

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