Alamogordo
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Alamogordo clear sky chart from 2005-11-06 to 2025-09-04.

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 3 1 3 3 3 4 3 5% 7% 64%	133513
	Night	4 4 1 4 3 3 4 3 5% 7% 63%	132666
Transparency	Day	20% 7% 9% 17% 26% 22%	128602
	Night	20% 6% 7% 15% 28% 23%	128584
Seeing	Day	5% 10% 24% 31% 24% 7%	15760
	Night	6% 5% 28% 38% 21% 2	25985

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	4 10% 3 5% 3 3 3 3 4 5% 57%	4098
	11th to 20th	Day	3 2 1 3 2 2 2 1 4 5% 75%	4100
	21st to end	Day	8% 5% 1 3 3 3 3 3 4 6% 61%	4510
February	1st to 10th	Day	6% 6% 1 3 2 2 3 2 4 5% 66%	1937
	11th to 20th	Day	7% 5% 1 3 3 3 3 2 3 7% 62%	1949
	21st to end	Day	6% 4 1 4 3 2 3 2 3 5% 67%	1650
March	1st to 10th	Day	4 4 1 3 3 2 3 2 4 6% 67%	4793
	11th to 20th	Day	3 5% 2 5% 3 3 3 3 4 5% 64%	5000
	21st to end	Day	3 7% 2 5% 3 3 3 3 5% 6% 60%	5656
April	1st to 10th	Day	3 3 1 4 2 2 3 3 5% 7% 68%	2400
	11th to 20th	Day	3 3 1 3 2 2 2 2 3 5% 74%	2371
	21st to end	Day	3 2 1 3 2 2 2 2 3 5% 76%	2400
May	1st to 10th	Day	1 2 1 2 1 2 3 2 3 4 79%	5440
	11th to 20th	Day	2 2 1 2 2 2 3 3 4 5% 73%	5405
	21st to end	Day	1 1 1 1 1 2 2 3 5% 82%	6259
June	1st to 10th	Day	2 3 1 3 2 3 3 3 5% 8% 68%	2800
	11th to 20th	Day	2 2 1 2 2 2 3 3 5% 5% 74%	2800
	21st to end	Day	4 3 2 4 4 5% 5% 5% 7% 8% 53%	2677
July	1st to 10th	Day	3 2 1 5% 4 5% 6% 5% 7% 9% 52%	5879
	11th to 20th	Day	1 1 1 3 3 4 6% 6% 11% 13% 51%	5880
	21st to end	Day	4 3 1 5% 5% 6% 7% 7% 10% 14% 38%	6401
August	1st to 10th	Day	2 2 1 3 3 4 6% 5% 8% 11% 55%	5358
	11th to 20th	Day	2 2 1 4 3 4 6% 6% 9% 12% 50%	5366
	21st to end	Day	2 2 1 4 4 5% 6% 5% 9% 12% 52%	5981
September	1st to 10th	Day	5% 5% 1 5% 5% 5% 6% 5% 8% 8% 47%	2317
	11th to 20th	Day	6% 3 1 4 3 4 4 4 6% 7% 58%	2280
	21st to end	Day	3 2 1 3 3 3 3 2 4 6% 70%	2087
October	1st to 10th	Day	2 2 1 3 3 2 2 2 4 6% 73%	3170
	11th to 20th	Day	2 2 1 3 2 2 3 2 4 6% 73%	3150
	21st to end	Day	2 1 1 1 1 1 1 1 2 3 85%	3438
November	1st to 10th	Day	2 2 1 3 3 3 2 2 4 6% 72%	1959
	11th to 20th	Day	3 2 1 2 2 2 3 2 5% 6% 71%	1860
	21st to end	Day	6% 5% 1 3 3 2 3 3 5% 7% 61%	1800
December	1st to 10th	Day	5% 4 1 3 2 2 2 2 4 7% 69%	2940
	11th to 20th	Day	4 4 2 5% 3 3 2 2 3 7% 66%	3058
	21st to end	Day	5% 3 1 2 2 2 2 2 4 7% 69%	4344
January	1st to 10th	Night	4 11% 3 5% 3 3 3 3 4 5% 57%	5867
	11th to 20th	Night	4 3 1 2 1 2 3 3 4 5% 74%	5880
	21st to end	Night	8% 6% 1 4 3 3 3 3 4 6% 58%	6468
February	1st to 10th	Night	5% 5% 2 2 2 2 3 3 4 6% 65%	2460
	11th to 20th	Night	9% 5% 1 3 3 2 3 2 4 6% 62%	2338
	21st to end	Night	7% 5% 2 3 2 3 4 3 4 5% 63%	1980
March	1st to 10th	Night	5% 5% 1 4 3 2 2 2 4 5% 67%	5077
	11th to 20th	Night	7% 6% 1 4 3 2 3 3 4 5% 62%	5000
	21st to end	Night	4 8% 2 4 3 3 3 2 4 6% 61%	5309
April	1st to 10th	Night	3 4 1 3 3 3 3 3 5% 6% 67%	2000
	11th to 20th	Night	6% 3 1 3 2 2 3 3 4 5% 66%	1977
	21st to end	Night	5% 3 1 3 2 2 2 3 4 4 72%	2000
May	1st to 10th	Night	3 3 1 3 2 2 2 2 4 5% 73%	4540
	11th to 20th	Night	4 2 1 3 3 3 4 3 5% 5% 68%	4510
	21st to end	Night	1 1 1 1 2 2 2 3 4 81%	4613
June	1st to 10th	Night	1 3 1 4 4 4 5% 4 6% 8% 58%	1600
	11th to 20th	Night	3 2 3 2 2 3 2 6% 7% 70%	1600
	21st to end	Night	4 3 1 4 4 7% 6% 4 9% 10% 48%	1712
July	1st to 10th	Night	2 3 2 5% 4 5% 5% 6% 8% 10% 50%	4100
	11th to 20th	Night	2 2 1 5% 4 5% 6% 5% 8% 12% 50%	4100
	21st to end	Night	4 4 2 6% 5% 6% 8% 7% 10% 13% 36%	4472
August	1st to 10th	Night	2 2 1 4 4 4 4 5% 9% 14% 51%	4450
	11th to 20th	Night	2 3 1 5% 4 5% 5% 6% 9% 14% 45%	4483
	21st to end	Night	2 2 2 6% 5% 6% 6% 6% 8% 12% 47%	4993
September	1st to 10th	Night	4 3 2 5% 4 4 5% 5% 6% 10% 52%	1930
	11th to 20th	Night	6% 3 1 3 3 4 4 4 6% 7% 58%	1900
	21st to end	Night	3 3 1 3 3 3 4 3 4 6% 67%	2085
October	1st to 10th	Night	3 1 1 3 2 2 2 2 4 5% 76%	3800
	11th to 20th	Night	3 3 1 4 3 3 2 2 3 5% 69%	3778
	21st to end	Night	4 2 1 2 2 2 2 1 2 4 79%	4120
November	1st to 10th	Night	4 2 1 2 2 2 2 2 4 7% 72%	2340
	11th to 20th	Night	3 2 1 2 2 2 2 3 4 7% 71%	2515
	21st to end	Night	7% 3 1 5% 3 3 4 3 4 6% 62%	2600
December	1st to 10th	Night	5% 2 1 3 2 2 2 3 4 7% 69%	4250
	11th to 20th	Night	4 3 1 3 2 3 4 3 5% 7% 65%	5144
	21st to end	Night	5% 3 1 3 2 3 3 2 4 7% 66%	6675

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	27% 7% 7% 9% 36% 14%	4099
	11th to 20th	Day	12% 4 4 17% 44% 18%	4100
	21st to end	Day	24% 6% 8% 12% 27% 22%	4510
February	1st to 10th	Day	22% 4 4 16% 27% 26%	1937
	11th to 20th	Day	26% 5% 4 16% 27% 22%	1959
	21st to end	Day	22% 4 4 8% 30% 32%	1650
March	1st to 10th	Day	19% 5% 5% 7% 29% 34%	4793
	11th to 20th	Day	21% 6% 5% 14% 29% 24%	5000
	21st to end	Day	22% 7% 6% 11% 30% 23%	5656
April	1st to 10th	Day	17% 4 6% 14% 32% 27%	2400
	11th to 20th	Day	16% 4 4 9% 31% 36%	2374
	21st to end	Day	13% 5% 4 13% 32% 33%	2400
May	1st to 10th	Day	11% 3 5% 13% 31% 37%	5440
	11th to 20th	Day	14% 5% 5% 11% 25% 40%	5408
	21st to end	Day	9% 3 5% 12% 16% 56%	6260
June	1st to 10th	Day	16% 6% 9% 18% 27% 24%	2800
	11th to 20th	Day	12% 3 6% 13% 24% 42%	2800
	21st to end	Day	26% 10% 12% 17% 19% 16%	2677
July	1st to 10th	Day	27% 10% 14% 22% 17% 9%	5816
	11th to 20th	Day	21% 14% 21% 28% 13% 3	5811
	21st to end	Day	31% 16% 20% 20% 10% 2	6217
August	1st to 10th	Day	24% 14% 16% 30% 13% 3	3901
	11th to 20th	Day	23% 12% 17% 25% 21% 3	3882
	21st to end	Day	28% 15% 17% 26% 13% 2	4311
September	1st to 10th	Day	32% 10% 12% 17% 18% 10%	2317
	11th to 20th	Day	26% 8% 10% 19% 25% 12%	2280
	21st to end	Day	17% 7% 8% 22% 31% 16%	2087
October	1st to 10th	Day	15% 4 6% 15% 30% 31%	3170
	11th to 20th	Day	14% 4 6% 17% 35% 24%	3150
	21st to end	Day	9% 2 3 14% 37% 35%	3438
November	1st to 10th	Day	16% 4 4 20% 33% 23%	1959
	11th to 20th	Day	16% 5% 6% 18% 29% 26%	1860
	21st to end	Day	23% 7% 6% 16% 31% 18%	1800
December	1st to 10th	Day	19% 3 6% 19% 34% 18%	2940
	11th to 20th	Day	23% 4 5% 12% 39% 18%	3056
	21st to end	Day	17% 4 4 19% 36% 20%	4344
January	1st to 10th	Night	25% 7% 6% 10% 38% 14%	5867
	11th to 20th	Night	12% 5% 4 11% 47% 21%	5880
	21st to end	Night	26% 7% 6% 11% 25% 25%	6468
February	1st to 10th	Night	21% 4 6% 14% 26% 29%	2460
	11th to 20th	Night	25% 4 5% 14% 29% 22%	2338
	21st to end	Night	23% 5% 4 8% 28% 32%	1980
March	1st to 10th	Night	20% 5% 4 9% 32% 31%	5077
	11th to 20th	Night	22% 7% 6% 13% 28% 24%	5000
	21st to end	Night	21% 6% 6% 13% 31% 23%	5309
April	1st to 10th	Night	19% 5% 5% 11% 36% 25%	2000
	11th to 20th	Night	20% 4 6% 12% 27% 32%	1977
	21st to end	Night	16% 5% 3 13% 32% 31%	2000
May	1st to 10th	Night	14% 3 4 14% 24% 41%	4537
	11th to 20th	Night	15% 8% 6% 12% 23% 36%	4511
	21st to end	Night	9% 3 4 10% 14% 60%	4614
June	1st to 10th	Night	22% 6% 9% 16% 21% 27%	1600
	11th to 20th	Night	13% 5% 4 14% 21% 43%	1600
	21st to end	Night	29% 9% 11% 18% 16% 17%	1712
July	1st to 10th	Night	27% 9% 15% 23% 18% 8%	4055
	11th to 20th	Night	23% 9% 19% 25% 19% 4	4046
	21st to end	Night	32% 13% 19% 22% 12% 2	4344
August	1st to 10th	Night	19% 10% 14% 29% 22% 5%	3231
	11th to 20th	Night	20% 9% 12% 22% 32% 4	3243
	21st to end	Night	30% 11% 15% 25% 18% 2	3597
September	1st to 10th	Night	28% 9% 13% 16% 20% 14%	1930
	11th to 20th	Night	24% 8% 10% 18% 25% 16%	1900
	21st to end	Night	18% 6% 9% 18% 32% 17%	2085
October	1st to 10th	Night	12% 4 6% 10% 30% 38%	3800
	11th to 20th	Night	18% 6% 6% 10% 30% 31%	3778
	21st to end	Night	14% 3 2 13% 31% 38%	4120
November	1st to 10th	Night	15% 5% 4 16% 34% 25%	2340
	11th to 20th	Night	15% 5% 6% 15% 32% 28%	2515
	21st to end	Night	24% 6% 5% 15% 30% 20%	2600
December	1st to 10th	Night	16% 4 6% 21% 37% 18%	4250
	11th to 20th	Night	22% 4 6% 12% 33% 24%	5145
	21st to end	Night	20% 4 4 17% 34% 21%	6675

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	11% 13% 31% 31% 12% 2	300
	11th to 20th	Day	7% 9% 38% 30% 14% 1	300
	21st to end	Day	6% 13% 35% 28% 17% 1	330
February	1st to 10th	Day	11% 14% 32% 27% 15% 2	300
	11th to 20th	Day	13% 14% 38% 28% 6% 1	300
	21st to end	Day	10% 24% 33% 25% 6% 2	249
March	1st to 10th	Day	9% 21% 40% 24% 6% 1	425
	11th to 20th	Day	11% 20% 32% 26% 10% 2	500
	21st to end	Day	7% 27% 36% 23% 5% 1	550
April	1st to 10th	Day	7% 20% 39% 25% 9% 1	500
	11th to 20th	Day	7% 25% 37% 24% 6% 1	492
	21st to end	Day	6% 23% 35% 26% 9% 1	500
May	1st to 10th	Day	3 16% 39% 32% 10%	503
	11th to 20th	Day	4 12% 33% 32% 16% 2	528
	21st to end	Day	2 11% 39% 35% 12% 1	600
June	1st to 10th	Day	2 5% 19% 40% 30% 4	730
	11th to 20th	Day	2 4 19% 42% 30% 3	730
	21st to end	Day	3 3 12% 38% 36% 8%	607
July	1st to 10th	Day	3 2 7% 33% 41% 14%	526
	11th to 20th	Day	1 1 4 26% 49% 20%	524
	21st to end	Day	3 6% 22% 47% 23%	575
August	1st to 10th	Day	3 1 4 26% 46% 21%	527
	11th to 20th	Day	5% 2 8% 27% 42% 16%	517
	21st to end	Day	4 1 5% 26% 44% 20%	583
September	1st to 10th	Day	5% 1 12% 34% 38% 10%	503
	11th to 20th	Day	6% 1 10% 37% 35% 10%	490
	21st to end	Day	2 4 18% 37% 28% 12%	311
October	1st to 10th	Day	6% 5% 18% 33% 26% 11%	300
	11th to 20th	Day	5% 9% 18% 33% 27% 9%	300
	21st to end	Day	5% 12% 20% 31% 25% 9%	330
November	1st to 10th	Day	4 10% 32% 29% 21% 5%	300
	11th to 20th	Day	4 7% 25% 34% 25% 6%	300
	21st to end	Day	10% 12% 30% 31% 15% 2	300
December	1st to 10th	Day	10% 11% 30% 30% 17% 3	300
	11th to 20th	Day	6% 12% 31% 36% 14% 1	300
	21st to end	Day	10% 15% 36% 30% 9%	330
January	1st to 10th	Night	7% 5% 33% 38% 15% 2	800
	11th to 20th	Night	9% 5% 34% 36% 14% 2	800
	21st to end	Night	9% 4 37% 34% 15% 1	880
February	1st to 10th	Night	7% 6% 37% 35% 13% 2	800
	11th to 20th	Night	11% 7% 41% 34% 7%	784
	21st to end	Night	8% 11% 47% 30% 4 1	660
March	1st to 10th	Night	8% 11% 41% 32% 8% 1	800
	11th to 20th	Night	8% 9% 35% 34% 14% 1	800
	21st to end	Night	6% 9% 43% 33% 9%	803
April	1st to 10th	Night	4 9% 48% 32% 8%	600
	11th to 20th	Night	7% 12% 42% 31% 8% 1	593
	21st to end	Night	6% 7% 45% 34% 8%	600
May	1st to 10th	Night	4 7% 44% 37% 8%	600
	11th to 20th	Night	3 4 34% 42% 17%	591
	21st to end	Night	2 5% 36% 46% 11% 1	650
June	1st to 10th	Night	2 3 24% 53% 17% 1	600
	11th to 20th	Night	3 2 23% 52% 19% 1	600
	21st to end	Night	3 2 14% 50% 30% 2	600
July	1st to 10th	Night	4 2 8% 47% 37% 3	585
	11th to 20th	Night	2 7% 38% 48% 4	582
	21st to end	Night	4 2 5% 34% 49% 7%	657
August	1st to 10th	Night	3 1 6% 29% 53% 9%	597
	11th to 20th	Night	4 1 6% 33% 47% 8%	594
	21st to end	Night	2 1 6% 38% 47% 7%	660
September	1st to 10th	Night	4 1 9% 40% 41% 6%	579
	11th to 20th	Night	5% 2 8% 44% 38% 3	570
	21st to end	Night	3 2 16% 48% 28% 3	579
October	1st to 10th	Night	4 2 23% 46% 24% 3	760
	11th to 20th	Night	3 4 24% 45% 21% 3	760
	21st to end	Night	6% 4 24% 35% 25% 6%	836
November	1st to 10th	Night	5% 5% 27% 36% 24% 4	780
	11th to 20th	Night	5% 4 23% 41% 23% 3	915
	21st to end	Night	8% 6% 30% 33% 20% 3	1000
December	1st to 10th	Night	9% 7% 29% 37% 18% 1	1000
	11th to 20th	Night	7% 7% 37% 34% 15% 1	1000
	21st to end	Night	10% 8% 32% 37% 12% 1	970

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