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 2026-10-29.

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 6% 7% 44%	158328
	Night	1 4 2 8% 6% 5% 5% 4 6% 8% 52%	151356
Transparency	Day	35% 7% 11% 21% 19% 7%	153252
	Night	26% 8% 15% 25% 20% 6%	147441
Seeing	Day	17% 24% 29% 19% 9% 2	18250
	Night	7% 19% 31% 29% 12% 1	28232

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% 17% 11% 9% 4 2 3 5% 41%	4720
	11th to 20th	Day	2 3 14% 8% 9% 6% 3 4 6% 45%	5137
	21st to end	Day	3 4 14% 7% 7% 5% 3 4 6% 48%	5844
February	1st to 10th	Day	4 5% 14% 7% 6% 5% 4 6% 6% 43%	1890
	11th to 20th	Day	4 4 14% 7% 6% 5% 4 5% 5% 44%	1968
	21st to end	Day	4 4 14% 9% 7% 5% 3 4 6% 44%	1730
March	1st to 10th	Day	5% 5% 16% 6% 5% 3 2 4 5% 49%	4726
	11th to 20th	Day	7% 6% 16% 8% 6% 4 4 5% 7% 37%	5110
	21st to end	Day	9% 7% 15% 7% 6% 5% 4 5% 6% 36%	5831
April	1st to 10th	Day	1 8% 4 10% 6% 6% 5% 4 6% 6% 44%	2520
	11th to 20th	Day	2 11% 7% 14% 7% 6% 4 3 6% 6% 36%	2491
	21st to end	Day	2 14% 5% 12% 7% 5% 5% 4 6% 6% 33%	2520
May	1st to 10th	Day	2 13% 6% 12% 6% 6% 5% 4 6% 6% 32%	7363
	11th to 20th	Day	3 12% 3 9% 5% 6% 6% 5% 6% 7% 38%	8191
	21st to end	Day	3 7% 3 7% 6% 6% 6% 5% 8% 9% 41%	9026
June	1st to 10th	Day	5% 7% 3 7% 4 5% 6% 4 7% 9% 43%	2940
	11th to 20th	Day	6% 6% 2 6% 4 5% 5% 4 5% 6% 52%	2940
	21st to end	Day	5% 5% 2 7% 5% 5% 6% 4 7% 7% 49%	2940
July	1st to 10th	Day	4 5% 2 6% 5% 5% 5% 4 6% 7% 50%	8249
	11th to 20th	Day	5% 5% 2 7% 6% 6% 7% 6% 8% 9% 41%	8250
	21st to end	Day	8% 6% 3 8% 7% 7% 6% 5% 6% 8% 36%	8486
August	1st to 10th	Day	6% 4 2 7% 5% 5% 6% 5% 7% 10% 43%	7549
	11th to 20th	Day	8% 6% 3 8% 6% 6% 6% 5% 7% 8% 38%	7152
	21st to end	Day	8% 6% 2 9% 7% 6% 7% 5% 7% 8% 34%	7751
September	1st to 10th	Day	8% 6% 3 7% 4 4 5% 3 4 5% 51%	2520
	11th to 20th	Day	8% 6% 2 8% 5% 5% 5% 3 5% 7% 48%	2520
	21st to end	Day	6% 7% 3 7% 4 4 3 2 4 6% 53%	2270
October	1st to 10th	Day	3 5% 1 4 3 3 3 2 4 6% 66%	3370
	11th to 20th	Day	3 7% 2 6% 4 6% 6% 5% 7% 8% 48%	3350
	21st to end	Day	1 6% 2 9% 4 3 3 2 4 6% 60%	3611
November	1st to 10th	Day	5% 2 7% 4 3 3 3 5% 6% 60%	1853
	11th to 20th	Day	5% 2 7% 4 4 3 3 5% 8% 59%	1890
	21st to end	Day	4 4 9% 6% 4 4 4 4 7% 55%	1722
December	1st to 10th	Day	2 2 9% 6% 7% 5% 2 3 6% 57%	2700
	11th to 20th	Day	3 2 10% 5% 4 4 3 5% 8% 57%	3106
	21st to end	Day	4 3 13% 8% 6% 6% 4 5% 8% 43%	4092
January	1st to 10th	Night	2 3 16% 12% 6% 4 3 5% 6% 43%	8201
	11th to 20th	Night	1 2 12% 9% 8% 7% 2 4 6% 49%	7908
	21st to end	Night	2 2 12% 9% 7% 6% 3 5% 6% 49%	8370
February	1st to 10th	Night	1 2 11% 8% 6% 5% 6% 6% 8% 47%	2730
	11th to 20th	Night	3 2 10% 8% 6% 7% 5% 7% 8% 44%	2538
	21st to end	Night	3 3 10% 7% 7% 6% 4 7% 8% 47%	2076
March	1st to 10th	Night	4 6% 12% 7% 5% 5% 4 6% 6% 46%	5370
	11th to 20th	Night	5% 5% 13% 7% 4 4 3 5% 7% 48%	5110
	21st to end	Night	1 6% 4 16% 7% 6% 5% 4 6% 7% 39%	5376
April	1st to 10th	Night	4 2 7% 6% 5% 5% 4 6% 8% 52%	2100
	11th to 20th	Night	1 8% 3 9% 7% 4 5% 4 5% 7% 46%	2077
	21st to end	Night	2 9% 3 8% 5% 3 5% 3 5% 8% 49%	2100
May	1st to 10th	Night	1 10% 5% 8% 5% 5% 5% 4 6% 8% 42%	5554
	11th to 20th	Night	1 7% 3 9% 4 4 5% 4 7% 8% 48%	4701
	21st to end	Night	2 5% 2 6% 4 4 4 4 5% 8% 55%	5181
June	1st to 10th	Night	2 4 1 4 3 4 4 4 7% 9% 59%	1680
	11th to 20th	Night	3 3 1 4 2 3 4 3 5% 6% 66%	1680
	21st to end	Night	2 3 1 4 3 3 3 3 7% 8% 62%	1680
July	1st to 10th	Night	2 2 1 4 3 4 5% 4 7% 8% 61%	4740
	11th to 20th	Night	1 2 1 3 3 3 5% 4 8% 12% 58%	4740
	21st to end	Night	3 3 1 5% 4 5% 6% 6% 10% 12% 46%	5619
August	1st to 10th	Night	2 3 1 4 3 4 5% 4 7% 10% 58%	5273
	11th to 20th	Night	2 3 1 4 3 4 4 4 8% 11% 55%	5704
	21st to end	Night	3 3 2 6% 4 6% 8% 6% 9% 12% 41%	6465
September	1st to 10th	Night	3 4 2 5% 3 5% 4 4 6% 8% 57%	2100
	11th to 20th	Night	3 4 2 4 3 4 5% 4 5% 7% 60%	2100
	21st to end	Night	3 4 2 6% 4 4 4 3 4 7% 58%	2345
October	1st to 10th	Night	2 3 1 3 2 3 3 3 4 5% 73%	4040
	11th to 20th	Night	1 3 1 4 4 4 5% 4 6% 7% 61%	4018
	21st to end	Night	1 4 2 6% 4 3 2 2 4 6% 67%	4348
November	1st to 10th	Night	3 2 5% 3 3 3 3 5% 7% 64%	2648
	11th to 20th	Night	3 2 7% 4 4 4 2 6% 8% 60%	2730
	21st to end	Night	4 2 8% 6% 4 4 4 6% 8% 54%	2895
December	1st to 10th	Night	1 1 7% 6% 4 4 2 5% 6% 64%	4710
	11th to 20th	Night	2 2 6% 6% 4 5% 3 5% 9% 58%	5321
	21st to end	Night	4 4 14% 9% 6% 5% 4 6% 8% 40%	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	38% 10% 10% 23% 14% 5%	4723
	11th to 20th	Day	35% 10% 13% 20% 16% 6%	5137
	21st to end	Day	34% 7% 10% 20% 20% 9%	5844
February	1st to 10th	Day	38% 8% 16% 19% 13% 6%	1890
	11th to 20th	Day	37% 7% 12% 21% 17% 7%	1977
	21st to end	Day	37% 5% 12% 18% 19% 7%	1730
March	1st to 10th	Day	35% 5% 6% 20% 21% 12%	4726
	11th to 20th	Day	39% 11% 9% 24% 15% 2	5110
	21st to end	Day	45% 5% 13% 25% 10% 1	5831
April	1st to 10th	Day	37% 7% 13% 21% 16% 6%	2520
	11th to 20th	Day	48% 4 12% 17% 16% 3	2494
	21st to end	Day	47% 7% 10% 24% 11% 2	2520
May	1st to 10th	Day	45% 6% 11% 20% 16% 1	7363
	11th to 20th	Day	37% 9% 10% 22% 18% 2	8195
	21st to end	Day	34% 7% 13% 23% 21% 3	9027
June	1st to 10th	Day	34% 7% 12% 24% 19% 5%	2940
	11th to 20th	Day	31% 6% 9% 18% 24% 13%	2940
	21st to end	Day	31% 6% 8% 18% 24% 12%	2940
July	1st to 10th	Day	27% 7% 5% 14% 23% 24%	8181
	11th to 20th	Day	34% 8% 12% 20% 16% 10%	8175
	21st to end	Day	42% 8% 16% 12% 13% 9%	8298
August	1st to 10th	Day	37% 7% 13% 15% 17% 12%	5978
	11th to 20th	Day	42% 9% 16% 14% 13% 5%	5633
	21st to end	Day	41% 7% 17% 16% 15% 4	6078
September	1st to 10th	Day	35% 4 8% 17% 25% 10%	2520
	11th to 20th	Day	36% 5% 11% 17% 24% 8%	2520
	21st to end	Day	32% 4 8% 24% 26% 6%	2270
October	1st to 10th	Day	21% 3 7% 25% 35% 9%	3370
	11th to 20th	Day	29% 5% 12% 29% 19% 5%	3350
	21st to end	Day	25% 5% 7% 31% 28% 4	3611
November	1st to 10th	Day	22% 6% 13% 23% 31% 5%	1853
	11th to 20th	Day	21% 6% 16% 29% 20% 8%	1890
	21st to end	Day	28% 5% 12% 27% 18% 10%	1722
December	1st to 10th	Day	26% 9% 10% 34% 18% 5%	2700
	11th to 20th	Day	24% 7% 14% 33% 20% 2	3104
	21st to end	Day	33% 8% 14% 17% 23% 5%	4092
January	1st to 10th	Night	33% 11% 12% 25% 14% 5%	8202
	11th to 20th	Night	30% 11% 12% 24% 17% 6%	7908
	21st to end	Night	27% 10% 10% 20% 23% 10%	8370
February	1st to 10th	Night	28% 11% 17% 22% 18% 5%	2730
	11th to 20th	Night	30% 8% 16% 24% 18% 4	2539
	21st to end	Night	29% 6% 15% 20% 23% 7%	2076
March	1st to 10th	Night	30% 10% 9% 20% 22% 9%	5370
	11th to 20th	Night	28% 12% 10% 23% 26% 3	5110
	21st to end	Night	38% 7% 20% 26% 8% 1	5376
April	1st to 10th	Night	26% 9% 16% 25% 20% 4	2100
	11th to 20th	Night	33% 6% 15% 26% 18% 2	2077
	21st to end	Night	30% 7% 16% 30% 16% 1	2100
May	1st to 10th	Night	35% 7% 15% 29% 14% 1	5552
	11th to 20th	Night	26% 10% 15% 31% 18%	4702
	21st to end	Night	23% 6% 17% 30% 22% 2	5182
June	1st to 10th	Night	19% 7% 18% 31% 19% 5%	1680
	11th to 20th	Night	18% 5% 12% 22% 29% 14%	1680
	21st to end	Night	18% 5% 13% 23% 26% 14%	1680
July	1st to 10th	Night	18% 6% 7% 17% 32% 20%	4700
	11th to 20th	Night	16% 5% 20% 33% 20% 5%	4692
	21st to end	Night	24% 10% 28% 20% 9% 8%	5495
August	1st to 10th	Night	24% 7% 19% 23% 18% 9%	4168
	11th to 20th	Night	24% 9% 30% 18% 13% 6%	4499
	21st to end	Night	28% 9% 30% 15% 16% 2	5069
September	1st to 10th	Night	23% 7% 13% 24% 25% 8%	2100
	11th to 20th	Night	22% 7% 13% 24% 24% 10%	2100
	21st to end	Night	24% 6% 11% 31% 24% 5%	2345
October	1st to 10th	Night	13% 4 8% 32% 34% 8%	4040
	11th to 20th	Night	17% 5% 13% 40% 20% 5%	4018
	21st to end	Night	18% 5% 8% 31% 32% 6%	4348
November	1st to 10th	Night	18% 7% 14% 27% 28% 6%	2648
	11th to 20th	Night	20% 6% 15% 31% 22% 6%	2730
	21st to end	Night	25% 6% 13% 28% 21% 7%	2895
December	1st to 10th	Night	18% 9% 13% 35% 21% 4	4710
	11th to 20th	Night	21% 8% 13% 29% 25% 3	5322
	21st to end	Night	34% 11% 12% 19% 19% 6%	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	23% 29% 22% 18% 7% 2	330
	11th to 20th	Day	20% 31% 29% 16% 3 1	330
	21st to end	Day	17% 36% 29% 13% 4 1	363
February	1st to 10th	Day	28% 36% 25% 8% 2 1	330
	11th to 20th	Day	28% 35% 25% 10% 2	330
	21st to end	Day	33% 30% 25% 11%	273
March	1st to 10th	Day	22% 33% 27% 16% 3	378
	11th to 20th	Day	21% 31% 29% 16% 3 1	540
	21st to end	Day	18% 40% 30% 10% 2	594
April	1st to 10th	Day	19% 40% 28% 10% 2 1	540
	11th to 20th	Day	26% 37% 24% 10% 2 1	532
	21st to end	Day	19% 36% 33% 9% 2 1	540
May	1st to 10th	Day	20% 31% 30% 15% 4 1	590
	11th to 20th	Day	16% 19% 33% 23% 8% 1	775
	21st to end	Day	16% 21% 29% 23% 11% 2	844
June	1st to 10th	Day	11% 19% 27% 25% 16% 3	780
	11th to 20th	Day	13% 21% 30% 23% 11% 2	780
	21st to end	Day	10% 19% 29% 24% 15% 2	780
July	1st to 10th	Day	10% 10% 25% 30% 21% 4	771
	11th to 20th	Day	9% 9% 26% 29% 21% 6%	768
	21st to end	Day	13% 10% 27% 26% 18% 5%	686
August	1st to 10th	Day	14% 17% 29% 23% 12% 3	567
	11th to 20th	Day	12% 10% 31% 27% 14% 5%	557
	21st to end	Day	12% 12% 31% 28% 13% 3	627
September	1st to 10th	Day	12% 15% 31% 24% 12% 5%	570
	11th to 20th	Day	12% 17% 36% 24% 10% 2	570
	21st to end	Day	12% 23% 28% 20% 12% 5%	385
October	1st to 10th	Day	11% 22% 27% 21% 15% 5%	360
	11th to 20th	Day	22% 27% 23% 18% 9% 2	360
	21st to end	Day	20% 29% 27% 17% 6% 1	387
November	1st to 10th	Day	18% 34% 27% 14% 6% 1	330
	11th to 20th	Day	20% 31% 29% 13% 5% 2	330
	21st to end	Day	12% 30% 37% 16% 4	330
December	1st to 10th	Day	25% 29% 25% 13% 7% 1	330
	11th to 20th	Day	21% 32% 30% 13% 4 1	330
	21st to end	Day	24% 31% 29% 11% 5%	363
January	1st to 10th	Night	11% 28% 30% 21% 9% 1	1050
	11th to 20th	Night	12% 29% 32% 20% 6% 1	929
	21st to end	Night	5% 26% 43% 19% 6% 1	924
February	1st to 10th	Night	8% 30% 40% 17% 5%	840
	11th to 20th	Night	8% 31% 37% 20% 3	824
	21st to end	Night	7% 33% 37% 19% 3	692
March	1st to 10th	Night	6% 24% 38% 27% 5%	840
	11th to 20th	Night	8% 20% 35% 28% 8%	840
	21st to end	Night	6% 23% 44% 24% 4	819
April	1st to 10th	Night	7% 22% 42% 25% 3	630
	11th to 20th	Night	8% 25% 35% 25% 7%	623
	21st to end	Night	7% 20% 36% 29% 8% 1	630
May	1st to 10th	Night	9% 13% 40% 29% 9%	630
	11th to 20th	Night	8% 11% 29% 38% 13%	621
	21st to end	Night	7% 14% 28% 35% 14% 1	683
June	1st to 10th	Night	4 7% 27% 40% 19% 2	630
	11th to 20th	Night	5% 10% 28% 44% 11% 1	630
	21st to end	Night	3 6% 23% 40% 26% 1	630
July	1st to 10th	Night	5% 3 17% 40% 33% 2	615
	11th to 20th	Night	3 2 11% 43% 37% 4	612
	21st to end	Night	6% 2 11% 38% 40% 3	690
August	1st to 10th	Night	8% 2 16% 39% 32% 3	627
	11th to 20th	Night	5% 3 15% 45% 29% 4	624
	21st to end	Night	6% 2 16% 43% 30% 3	693
September	1st to 10th	Night	4 3 17% 49% 23% 4	630
	11th to 20th	Night	6% 3 24% 45% 21% 3	630
	21st to end	Night	5% 9% 25% 39% 19% 4	691
October	1st to 10th	Night	3 13% 32% 34% 14% 3	840
	11th to 20th	Night	7% 20% 30% 29% 13% 1	840
	21st to end	Night	6% 19% 35% 29% 9% 2	912
November	1st to 10th	Night	6% 23% 35% 27% 8% 1	1008
	11th to 20th	Night	8% 27% 36% 23% 5% 1	1050
	21st to end	Night	5% 24% 37% 27% 6% 1	1050
December	1st to 10th	Night	10% 29% 35% 21% 5%	1050
	11th to 20th	Night	10% 30% 34% 20% 6% 1	1050
	21st to end	Night	12% 29% 35% 19% 4 1	1155

Page generated at 2026-10-26 02:37:52. Version ac07

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