Durango
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Durango clear sky chart from 2005-11-06 to 2025-10-19.

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	4 5% 2 5% 4 4 5% 4 6% 7% 56%	134983
	Night	5% 5% 2 5% 3 3 4 3 5% 7% 59%	132238
Transparency	Day	25% 6% 10% 20% 25% 14%	129897
	Night	26% 4 9% 21% 26% 14%	128327
Seeing	Day	9% 12% 31% 30% 15% 3	16451
	Night	8% 5% 26% 39% 20% 3	26589

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 6% 3 7% 3 3 4 4 5% 7% 57%	4098
	11th to 20th	Day	2 4 1 3 2 3 4 4 6% 7% 64%	4100
	21st to end	Day	3 9% 2 5% 3 3 4 3 4 5% 60%	4510
February	1st to 10th	Day	2 8% 3 6% 4 3 4 3 5% 5% 57%	1800
	11th to 20th	Day	5% 9% 2 7% 4 4 4 3 5% 6% 50%	1805
	21st to end	Day	4 10% 4 6% 3 4 4 3 4 6% 53%	1672
March	1st to 10th	Day	3 8% 2 6% 4 4 5% 4 6% 7% 52%	4954
	11th to 20th	Day	5% 11% 3 8% 4 5% 6% 4 6% 6% 42%	5000
	21st to end	Day	3 9% 3 7% 4 5% 5% 4 6% 7% 47%	5486
April	1st to 10th	Day	4 5% 1 6% 4 5% 5% 4 5% 7% 55%	2392
	11th to 20th	Day	3 5% 2 5% 4 4 5% 5% 6% 7% 54%	2371
	21st to end	Day	4 5% 2 4 4 5% 4 4 6% 7% 56%	2400
May	1st to 10th	Day	7% 5% 2 5% 4 4 5% 4 6% 7% 52%	5719
	11th to 20th	Day	3 4 1 4 4 4 5% 5% 7% 8% 55%	5841
	21st to end	Day	2 3 1 3 3 3 4 4 6% 7% 65%	6803
June	1st to 10th	Day	4 3 1 3 3 3 4 4 6% 7% 63%	2800
	11th to 20th	Day	3 2 1 3 3 3 4 3 4 4 72%	2800
	21st to end	Day	2 2 1 4 3 4 5% 4 6% 7% 62%	2800
July	1st to 10th	Day	2 2 1 4 3 3 4 4 5% 6% 65%	6065
	11th to 20th	Day	2 2 1 4 5% 7% 10% 8% 11% 10% 41%	5880
	21st to end	Day	3 3 2 5% 5% 5% 6% 6% 8% 9% 50%	6401
August	1st to 10th	Day	4 3 1 4 5% 6% 7% 6% 8% 10% 46%	5779
	11th to 20th	Day	2 3 1 5% 4 5% 6% 5% 7% 10% 51%	5589
	21st to end	Day	4 4 1 7% 5% 7% 8% 7% 9% 9% 40%	5984
September	1st to 10th	Day	7% 4 1 6% 4 5% 5% 4 6% 8% 51%	2400
	11th to 20th	Day	6% 4 2 5% 4 4 4 4 6% 6% 54%	2372
	21st to end	Day	7% 2 1 4 3 2 3 2 4 6% 65%	2117
October	1st to 10th	Day	5% 3 1 3 3 2 3 3 4 5% 68%	3270
	11th to 20th	Day	11% 5% 1 4 3 4 3 3 4 6% 55%	3230
	21st to end	Day	4 3 1 2 2 2 2 2 3 5% 73%	3438
November	1st to 10th	Day	4 4 1 2 2 3 3 2 4 6% 69%	1959
	11th to 20th	Day	2 3 1 3 2 2 3 2 5% 6% 71%	1830
	21st to end	Day	7% 6% 1 3 2 2 3 2 4 4 65%	1604
December	1st to 10th	Day	3 4 1 2 1 2 2 2 4 8% 72%	2620
	11th to 20th	Day	4 5% 1 3 2 3 4 4 5% 7% 61%	3026
	21st to end	Day	4 7% 2 4 3 3 3 3 5% 6% 60%	4068
January	1st to 10th	Night	1 8% 3 8% 4 4 4 3 5% 5% 54%	5867
	11th to 20th	Night	2 6% 2 4 3 3 3 3 4 6% 66%	5880
	21st to end	Night	3 9% 4 6% 4 3 3 2 4 6% 56%	6468
February	1st to 10th	Night	4 8% 2 4 2 2 2 2 4 7% 62%	2600
	11th to 20th	Night	6% 7% 2 4 4 3 3 3 4 5% 59%	2481
	21st to end	Night	4 10% 3 4 3 3 3 3 5% 4 60%	1955
March	1st to 10th	Night	4 10% 2 6% 4 4 4 3 5% 6% 52%	4940
	11th to 20th	Night	7% 10% 2 6% 4 4 4 3 5% 6% 48%	5000
	21st to end	Night	5% 6% 2 5% 4 4 4 4 5% 7% 53%	5489
April	1st to 10th	Night	6% 6% 2 4 3 3 4 4 5% 7% 57%	2007
	11th to 20th	Night	6% 5% 2 5% 4 4 4 4 5% 6% 57%	1977
	21st to end	Night	4 5% 2 4 2 3 2 4 5% 7% 62%	2000
May	1st to 10th	Night	7% 5% 2 5% 4 3 3 3 5% 7% 57%	4245
	11th to 20th	Night	4 4 1 4 3 3 3 3 5% 7% 62%	4074
	21st to end	Night	4 3 1 3 2 3 3 2 4 6% 70%	4090
June	1st to 10th	Night	2 3 1 4 3 2 4 3 4 7% 67%	1600
	11th to 20th	Night	4 3 1 3 2 3 2 3 4 5% 71%	1600
	21st to end	Night	4 2 1 3 3 4 5% 4 6% 8% 61%	1600
July	1st to 10th	Night	3 3 1 4 3 3 4 4 4 6% 63%	3908
	11th to 20th	Night	2 2 1 4 4 5% 6% 6% 10% 12% 48%	4100
	21st to end	Night	3 4 2 6% 4 5% 6% 5% 9% 9% 47%	4472
August	1st to 10th	Night	4 4 2 6% 4 5% 6% 6% 9% 10% 44%	4033
	11th to 20th	Night	3 4 1 5% 4 5% 6% 5% 7% 10% 51%	4257
	21st to end	Night	6% 5% 3 8% 7% 6% 6% 4 7% 10% 37%	4993
September	1st to 10th	Night	5% 4 2 5% 5% 4 5% 5% 6% 8% 50%	2000
	11th to 20th	Night	7% 4 1 5% 4 5% 4 3 4 6% 57%	2024
	21st to end	Night	8% 3 1 3 2 2 3 2 3 5% 67%	2281
October	1st to 10th	Night	7% 3 1 2 1 2 2 2 3 4 73%	3920
	11th to 20th	Night	12% 5% 2 4 4 3 3 3 4 5% 55%	3874
	21st to end	Night	6% 3 1 3 2 2 2 2 3 4 72%	4120
November	1st to 10th	Night	5% 3 1 2 2 2 3 2 4 6% 69%	2340
	11th to 20th	Night	2 3 1 2 2 2 2 2 4 6% 74%	2546
	21st to end	Night	7% 6% 2 3 2 2 2 2 3 5% 65%	2794
December	1st to 10th	Night	3 4 1 2 2 2 2 2 3 6% 73%	4570
	11th to 20th	Night	4 7% 1 4 3 3 3 3 4 6% 62%	5181
	21st to end	Night	6% 7% 2 4 3 3 3 3 3 5% 62%	6952

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	28% 4 13% 30% 20% 5%	4099
	11th to 20th	Day	20% 4 11% 25% 22% 18%	4100
	21st to end	Day	28% 4 8% 25% 25% 10%	4510
February	1st to 10th	Day	29% 5% 12% 25% 20% 9%	1800
	11th to 20th	Day	34% 4 8% 23% 25% 5%	1814
	21st to end	Day	33% 4 8% 15% 30% 9%	1672
March	1st to 10th	Day	28% 4 8% 19% 30% 11%	4954
	11th to 20th	Day	37% 7% 9% 23% 19% 6%	5000
	21st to end	Day	34% 5% 11% 27% 21% 3	5486
April	1st to 10th	Day	27% 5% 8% 19% 29% 12%	2392
	11th to 20th	Day	26% 5% 9% 19% 27% 14%	2374
	21st to end	Day	25% 4 8% 22% 30% 10%	2400
May	1st to 10th	Day	29% 6% 10% 17% 24% 14%	5719
	11th to 20th	Day	21% 6% 10% 18% 32% 12%	5844
	21st to end	Day	15% 4 8% 14% 40% 19%	6804
June	1st to 10th	Day	19% 5% 7% 19% 29% 22%	2800
	11th to 20th	Day	15% 3 6% 11% 26% 39%	2800
	21st to end	Day	19% 5% 7% 14% 24% 31%	2800
July	1st to 10th	Day	18% 6% 9% 9% 19% 40%	6002
	11th to 20th	Day	25% 12% 17% 25% 13% 8%	5811
	21st to end	Day	24% 11% 16% 19% 19% 11%	6217
August	1st to 10th	Day	33% 13% 21% 12% 11% 9%	4208
	11th to 20th	Day	26% 10% 14% 15% 20% 15%	4048
	21st to end	Day	29% 11% 14% 19% 19% 7%	4311
September	1st to 10th	Day	28% 7% 10% 18% 21% 16%	2400
	11th to 20th	Day	26% 7% 9% 16% 25% 18%	2372
	21st to end	Day	20% 4 6% 17% 37% 15%	2117
October	1st to 10th	Day	17% 5% 6% 15% 32% 25%	3270
	11th to 20th	Day	29% 4 4 22% 29% 12%	3230
	21st to end	Day	16% 2 7% 23% 42% 9%	3438
November	1st to 10th	Day	18% 2 8% 28% 35% 9%	1959
	11th to 20th	Day	16% 3 7% 27% 38% 8%	1830
	21st to end	Day	25% 3 6% 25% 29% 12%	1604
December	1st to 10th	Day	15% 3 10% 33% 30% 9%	2620
	11th to 20th	Day	24% 5% 9% 35% 25% 2	3024
	21st to end	Day	26% 4 13% 24% 26% 7%	4068
January	1st to 10th	Night	32% 3 9% 28% 23% 5%	5867
	11th to 20th	Night	22% 3 11% 23% 25% 16%	5880
	21st to end	Night	30% 4 7% 28% 20% 11%	6468
February	1st to 10th	Night	25% 2 12% 28% 22% 11%	2600
	11th to 20th	Night	29% 3 10% 22% 28% 8%	2482
	21st to end	Night	29% 3 7% 17% 31% 13%	1955
March	1st to 10th	Night	32% 3 7% 17% 31% 9%	4940
	11th to 20th	Night	35% 5% 8% 18% 25% 10%	5000
	21st to end	Night	29% 5% 10% 29% 23% 5%	5489
April	1st to 10th	Night	27% 5% 7% 18% 29% 14%	2007
	11th to 20th	Night	28% 4 7% 17% 27% 18%	1977
	21st to end	Night	22% 4 7% 21% 34% 12%	2000
May	1st to 10th	Night	26% 4 11% 19% 28% 11%	4242
	11th to 20th	Night	20% 5% 8% 20% 33% 14%	4075
	21st to end	Night	16% 3 7% 12% 37% 25%	4090
June	1st to 10th	Night	18% 4 8% 15% 28% 27%	1600
	11th to 20th	Night	16% 2 7% 10% 20% 44%	1600
	21st to end	Night	19% 5% 9% 12% 21% 34%	1600
July	1st to 10th	Night	22% 5% 9% 7% 10% 47%	3863
	11th to 20th	Night	24% 9% 17% 26% 11% 13%	4046
	21st to end	Night	29% 9% 16% 19% 15% 12%	4344
August	1st to 10th	Night	38% 12% 19% 10% 10% 12%	2928
	11th to 20th	Night	30% 8% 17% 12% 13% 20%	3074
	21st to end	Night	35% 8% 13% 19% 16% 9%	3597
September	1st to 10th	Night	29% 7% 13% 16% 18% 18%	2000
	11th to 20th	Night	28% 5% 8% 14% 20% 24%	2024
	21st to end	Night	22% 3 6% 13% 34% 22%	2281
October	1st to 10th	Night	17% 3 5% 10% 36% 29%	3920
	11th to 20th	Night	32% 4 5% 14% 31% 14%	3874
	21st to end	Night	17% 3 4 20% 45% 11%	4120
November	1st to 10th	Night	19% 3 6% 26% 35% 12%	2340
	11th to 20th	Night	14% 3 5% 28% 38% 10%	2546
	21st to end	Night	25% 2 7% 23% 32% 11%	2794
December	1st to 10th	Night	16% 3 8% 35% 28% 9%	4570
	11th to 20th	Night	25% 4 7% 28% 30% 6%	5182
	21st to end	Night	28% 3 10% 23% 29% 8%	6952

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	10% 11% 40% 26% 11% 1	300
	11th to 20th	Day	16% 13% 36% 25% 9% 1	300
	21st to end	Day	6% 12% 38% 31% 11% 2	330
February	1st to 10th	Day	11% 17% 42% 24% 5%	300
	11th to 20th	Day	14% 16% 41% 23% 5%	300
	21st to end	Day	15% 18% 41% 21% 4	271
March	1st to 10th	Day	13% 21% 36% 22% 8%	500
	11th to 20th	Day	14% 21% 34% 21% 9% 1	500
	21st to end	Day	17% 28% 33% 15% 6% 1	550
April	1st to 10th	Day	14% 23% 38% 18% 7% 1	500
	11th to 20th	Day	17% 28% 32% 17% 6%	492
	21st to end	Day	13% 24% 36% 22% 5%	500
May	1st to 10th	Day	13% 22% 40% 18% 6%	503
	11th to 20th	Day	11% 16% 34% 26% 11% 2	528
	21st to end	Day	7% 15% 33% 28% 15% 2	732
June	1st to 10th	Day	5% 8% 24% 40% 20% 3	730
	11th to 20th	Day	5% 8% 33% 33% 17% 5%	730
	21st to end	Day	3 8% 29% 36% 20% 4	730
July	1st to 10th	Day	3 4 22% 39% 26% 5%	608
	11th to 20th	Day	3 3 20% 34% 31% 8%	524
	21st to end	Day	4 2 19% 39% 29% 7%	575
August	1st to 10th	Day	6% 5% 21% 40% 22% 6%	527
	11th to 20th	Day	3 4 25% 41% 21% 6%	517
	21st to end	Day	5% 3 22% 40% 25% 5%	583
September	1st to 10th	Day	7% 4 22% 39% 23% 5%	530
	11th to 20th	Day	6% 5% 32% 38% 15% 4	530
	21st to end	Day	8% 10% 27% 34% 17% 5%	447
October	1st to 10th	Day	11% 11% 21% 30% 21% 6%	330
	11th to 20th	Day	12% 15% 26% 29% 15% 3	324
	21st to end	Day	8% 12% 31% 30% 18% 1	330
November	1st to 10th	Day	11% 14% 31% 29% 15% 1	300
	11th to 20th	Day	7% 9% 38% 32% 12% 3	300
	21st to end	Day	14% 8% 34% 28% 14% 3	300
December	1st to 10th	Day	12% 9% 36% 28% 12% 3	300
	11th to 20th	Day	9% 11% 40% 27% 10% 3	300
	21st to end	Day	15% 14% 37% 27% 6% 1	330
January	1st to 10th	Night	7% 4 33% 38% 15% 4	800
	11th to 20th	Night	8% 4 32% 38% 15% 3	800
	21st to end	Night	10% 5% 31% 36% 15% 3	880
February	1st to 10th	Night	9% 6% 37% 36% 11% 1	800
	11th to 20th	Night	9% 7% 36% 38% 10% 1	784
	21st to end	Night	11% 6% 41% 37% 6%	660
March	1st to 10th	Night	8% 7% 36% 35% 13% 2	800
	11th to 20th	Night	9% 7% 28% 38% 17% 2	800
	21st to end	Night	10% 8% 37% 34% 11% 1	880
April	1st to 10th	Night	9% 10% 37% 36% 8%	607
	11th to 20th	Night	9% 12% 32% 35% 11% 1	593
	21st to end	Night	7% 10% 34% 38% 11% 1	600
May	1st to 10th	Night	8% 8% 31% 38% 15% 1	600
	11th to 20th	Night	8% 6% 25% 41% 17% 2	591
	21st to end	Night	9% 6% 29% 37% 18% 1	650
June	1st to 10th	Night	4 4 20% 47% 25% 1	600
	11th to 20th	Night	4 4 24% 45% 23% 1	600
	21st to end	Night	4 3 20% 43% 29% 2	600
July	1st to 10th	Night	3 1 16% 41% 37% 2	585
	11th to 20th	Night	4 1 10% 38% 41% 7%	582
	21st to end	Night	4 2 9% 36% 41% 7%	657
August	1st to 10th	Night	5% 2 11% 33% 44% 7%	597
	11th to 20th	Night	5% 2 11% 40% 37% 5%	594
	21st to end	Night	6% 3 11% 38% 37% 5%	660
September	1st to 10th	Night	6% 1 12% 44% 32% 4	600
	11th to 20th	Night	8% 2 17% 43% 28% 3	624
	21st to end	Night	8% 4 18% 40% 26% 5%	800
October	1st to 10th	Night	12% 3 24% 39% 19% 3	800
	11th to 20th	Night	8% 3 24% 42% 19% 4	792
	21st to end	Night	6% 4 25% 40% 21% 4	836
November	1st to 10th	Night	7% 3 21% 44% 21% 3	780
	11th to 20th	Night	3 5% 32% 40% 16% 4	946
	21st to end	Night	12% 6% 25% 35% 20% 4	1000
December	1st to 10th	Night	8% 7% 29% 41% 12% 2	1000
	11th to 20th	Night	11% 6% 31% 36% 15% 1	1000
	21st to end	Night	12% 7% 32% 38% 10% 1	1091

Page generated at 2025-10-15 23:50:28. Version ac07

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