Carlsbad Caverns Visitor Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carlsbad Caverns Visitor Center clear sky chart from 2005-11-06 to 2025-07-21.

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 3 1 3 3 3 3 3 5% 7% 66%	123871
	Night	4 3 1 3 2 3 3 3 5% 7% 66%	124104
Transparency	Day	18% 4 7% 16% 26% 28%	123647
	Night	18% 4 7% 15% 26% 30%	123917
Seeing	Day	6% 8% 23% 31% 24% 8%	15761
	Night	6% 7% 26% 38% 21% 2	25856

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 4 2 4 3 3 4 3 4 6% 65%	4098
	11th to 20th	Day	2 3 1 2 2 2 2 3 3 5% 74%	4100
	21st to end	Day	2 4 2 4 3 2 3 3 5% 7% 66%	4931
February	1st to 10th	Day	2 3 2 4 2 3 3 3 4 6% 70%	2000
	11th to 20th	Day	3 6% 2 4 3 4 3 3 5% 7% 61%	1949
	21st to end	Day	2 4 2 4 3 2 2 3 4 5% 69%	1650
March	1st to 10th	Day	2 3 2 4 2 2 3 3 4 6% 68%	4500
	11th to 20th	Day	9% 4 1 3 3 3 3 3 4 6% 61%	4949
	21st to end	Day	2 4 2 4 3 3 3 3 5% 7% 63%	5867
April	1st to 10th	Day	4 3 1 2 3 2 3 3 5% 6% 68%	2400
	11th to 20th	Day	5% 2 1 2 2 3 3 1 3 5% 72%	2371
	21st to end	Day	2 2 1 2 2 2 2 2 4 6% 75%	2400
May	1st to 10th	Day	4 2 1 2 2 2 2 2 3 5% 74%	5440
	11th to 20th	Day	4 2 1 2 2 2 3 3 4 6% 71%	5441
	21st to end	Day	4 2 1 2 2 2 3 3 5% 7% 70%	6446
June	1st to 10th	Day	2 2 1 3 2 2 3 4 7% 8% 66%	2623
	11th to 20th	Day	2 2 1 3 2 3 3 4 5% 8% 68%	2800
	21st to end	Day	6% 3 1 4 4 3 4 4 6% 8% 57%	2800
July	1st to 10th	Day	6% 3 1 4 4 5% 6% 6% 8% 11% 46%	4388
	11th to 20th	Day	3 2 1 3 3 3 4 4 7% 9% 61%	4240
	21st to end	Day	6% 3 2 4 3 3 4 4 7% 11% 52%	4119
August	1st to 10th	Day	3 1 1 2 2 3 3 3 6% 9% 67%	3784
	11th to 20th	Day	2 3 1 3 3 3 4 4 7% 9% 62%	3726
	21st to end	Day	5% 2 1 4 3 3 5% 4 7% 10% 54%	4180
September	1st to 10th	Day	9% 3 1 4 4 4 5% 4 6% 8% 52%	2280
	11th to 20th	Day	9% 4 2 5% 4 4 5% 4 6% 8% 51%	2204
	21st to end	Day	7% 2 1 3 2 3 3 3 4 6% 67%	2090
October	1st to 10th	Day	3 2 1 2 1 2 2 2 3 5% 78%	3428
	11th to 20th	Day	4 2 1 2 2 2 2 1 4 6% 76%	3150
	21st to end	Day	2 2 1 2 2 2 1 1 2 4 81%	3438
November	1st to 10th	Day	6% 2 1 2 2 2 2 2 3 5% 73%	1879
	11th to 20th	Day	3 3 1 3 3 3 3 3 4 5% 69%	1800
	21st to end	Day	5% 4 1 3 2 3 3 3 6% 6% 65%	1800
December	1st to 10th	Day	11% 9% 2 5% 2 3 3 3 4 5% 54%	2940
	11th to 20th	Day	2 3 2 3 3 3 3 3 5% 6% 66%	3391
	21st to end	Day	2 2 1 2 1 2 2 2 3 6% 76%	4269
January	1st to 10th	Night	5% 5% 1 4 3 3 3 3 4 5% 64%	5867
	11th to 20th	Night	2 3 1 3 2 2 3 2 4 6% 73%	5880
	21st to end	Night	3 4 2 4 3 3 3 3 4 7% 64%	6015
February	1st to 10th	Night	3 4 1 3 2 2 3 3 4 6% 70%	2400
	11th to 20th	Night	5% 3 2 4 3 3 3 3 5% 6% 65%	2338
	21st to end	Night	4 4 1 4 3 3 3 3 4 6% 66%	1980
March	1st to 10th	Night	3 3 1 3 3 2 3 3 4 6% 69%	5374
	11th to 20th	Night	10% 3 1 3 3 3 3 3 5% 5% 62%	5045
	21st to end	Night	1 2 1 4 2 3 4 3 5% 7% 67%	5088
April	1st to 10th	Night	4 3 1 4 4 3 3 3 4 6% 67%	2000
	11th to 20th	Night	4 2 1 3 2 3 3 3 4 5% 70%	1977
	21st to end	Night	3 2 1 2 2 2 2 2 3 5% 76%	2000
May	1st to 10th	Night	8% 2 1 3 2 2 2 2 3 5% 71%	4540
	11th to 20th	Night	6% 4 1 2 2 3 3 2 5% 8% 63%	4469
	21st to end	Night	4 2 1 2 2 2 3 2 4 5% 74%	4451
June	1st to 10th	Night	3 2 1 3 3 3 4 4 8% 8% 61%	1770
	11th to 20th	Night	2 1 1 3 3 3 3 3 6% 7% 69%	1600
	21st to end	Night	4 3 1 4 3 4 5% 3 7% 10% 57%	1600
July	1st to 10th	Night	7% 2 1 5% 4 4 5% 5% 8% 11% 49%	2782
	11th to 20th	Night	1 1 1 3 3 3 4 4 7% 11% 62%	2950
	21st to end	Night	6% 3 1 6% 4 3 4 4 8% 14% 46%	3440
August	1st to 10th	Night	2 1 1 2 3 4 4 4 7% 12% 60%	3155
	11th to 20th	Night	2 2 1 3 3 3 4 4 6% 10% 62%	3113
	21st to end	Night	5% 3 2 4 3 4 5% 5% 8% 13% 49%	3487
September	1st to 10th	Night	8% 4 1 4 3 4 4 4 6% 7% 54%	1900
	11th to 20th	Night	8% 4 2 4 3 3 4 3 7% 9% 54%	1975
	21st to end	Night	6% 3 1 4 3 3 3 3 6% 7% 63%	2090
October	1st to 10th	Night	4 2 2 1 1 2 2 3 4 79%	3530
	11th to 20th	Night	8% 2 1 2 2 2 2 1 3 4 73%	3778
	21st to end	Night	3 2 1 2 1 1 1 2 2 3 82%	4120
November	1st to 10th	Night	6% 2 1 1 2 2 2 2 4 5% 74%	2397
	11th to 20th	Night	2 3 1 3 2 2 3 3 4 5% 71%	2600
	21st to end	Night	6% 4 1 3 2 3 3 3 4 5% 67%	2600
December	1st to 10th	Night	12% 7% 1 3 2 2 2 2 4 6% 59%	4250
	11th to 20th	Night	3 2 1 3 2 2 3 2 4 7% 71%	4816
	21st to end	Night	2 3 1 2 2 2 2 2 3 5% 77%	6727

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	22% 2 5% 11% 33% 26%	4099
	11th to 20th	Day	12% 3 4 18% 36% 27%	4100
	21st to end	Day	18% 4 6% 20% 26% 27%	4931
February	1st to 10th	Day	17% 3 6% 15% 24% 34%	2000
	11th to 20th	Day	23% 4 7% 15% 23% 29%	1959
	21st to end	Day	18% 4 4 10% 24% 41%	1650
March	1st to 10th	Day	17% 3 5% 7% 24% 44%	4500
	11th to 20th	Day	24% 4 5% 9% 21% 37%	4949
	21st to end	Day	17% 3 7% 9% 25% 39%	5867
April	1st to 10th	Day	16% 3 6% 11% 28% 36%	2400
	11th to 20th	Day	16% 3 4 11% 25% 41%	2374
	21st to end	Day	11% 3 5% 12% 29% 39%	2400
May	1st to 10th	Day	13% 3 5% 16% 21% 43%	5440
	11th to 20th	Day	13% 4 5% 12% 25% 42%	5444
	21st to end	Day	14% 4 7% 14% 15% 47%	6447
June	1st to 10th	Day	14% 6% 10% 21% 24% 25%	2623
	11th to 20th	Day	13% 4 7% 14% 24% 38%	2800
	21st to end	Day	24% 6% 10% 18% 24% 19%	2800
July	1st to 10th	Day	28% 7% 14% 26% 19% 7%	4324
	11th to 20th	Day	18% 6% 12% 23% 31% 11%	4171
	21st to end	Day	24% 7% 12% 27% 26% 4	3989
August	1st to 10th	Day	13% 5% 9% 29% 33% 10%	3772
	11th to 20th	Day	17% 6% 13% 20% 30% 13%	3762
	21st to end	Day	23% 7% 17% 26% 22% 5%	4179
September	1st to 10th	Day	27% 8% 12% 17% 20% 16%	2280
	11th to 20th	Day	29% 7% 10% 18% 23% 13%	2204
	21st to end	Day	19% 5% 7% 17% 32% 20%	2090
October	1st to 10th	Day	11% 4 6% 9% 23% 46%	3428
	11th to 20th	Day	13% 2 11% 16% 22% 36%	3150
	21st to end	Day	11% 2 2 14% 38% 33%	3438
November	1st to 10th	Day	16% 3 5% 18% 29% 29%	1879
	11th to 20th	Day	17% 4 7% 16% 29% 27%	1800
	21st to end	Day	20% 4 7% 15% 28% 26%	1800
December	1st to 10th	Day	33% 3 5% 14% 22% 22%	2940
	11th to 20th	Day	18% 4 6% 14% 32% 26%	3389
	21st to end	Day	11% 3 4 15% 43% 25%	4269
January	1st to 10th	Night	21% 3 6% 13% 33% 24%	5867
	11th to 20th	Night	13% 3 6% 15% 34% 28%	5880
	21st to end	Night	20% 4 5% 21% 25% 25%	6015
February	1st to 10th	Night	15% 3 8% 13% 24% 38%	2400
	11th to 20th	Night	20% 4 8% 12% 25% 30%	2338
	21st to end	Night	18% 4 5% 10% 21% 42%	1980
March	1st to 10th	Night	15% 4 4 7% 25% 46%	5374
	11th to 20th	Night	23% 5% 5% 8% 21% 38%	5045
	21st to end	Night	14% 4 7% 11% 23% 41%	5088
April	1st to 10th	Night	19% 3 5% 10% 24% 39%	2000
	11th to 20th	Night	15% 4 7% 12% 21% 40%	1977
	21st to end	Night	13% 3 4 14% 26% 40%	2000
May	1st to 10th	Night	17% 2 6% 16% 12% 46%	4537
	11th to 20th	Night	19% 4 6% 10% 23% 37%	4470
	21st to end	Night	13% 4 8% 11% 13% 52%	4452
June	1st to 10th	Night	17% 7% 12% 19% 23% 23%	1770
	11th to 20th	Night	14% 4 8% 13% 24% 37%	1600
	21st to end	Night	21% 6% 15% 20% 21% 17%	1600
July	1st to 10th	Night	27% 6% 17% 28% 17% 5%	2738
	11th to 20th	Night	15% 6% 16% 25% 29% 10%	2896
	21st to end	Night	26% 6% 13% 28% 24% 3	3332
August	1st to 10th	Night	16% 4 9% 26% 35% 10%	3144
	11th to 20th	Night	17% 5% 13% 24% 31% 10%	3143
	21st to end	Night	25% 7% 16% 28% 20% 5%	3487
September	1st to 10th	Night	27% 7% 12% 18% 18% 18%	1900
	11th to 20th	Night	25% 7% 12% 21% 20% 15%	1975
	21st to end	Night	21% 5% 9% 17% 28% 20%	2090
October	1st to 10th	Night	12% 3 5% 9% 24% 47%	3530
	11th to 20th	Night	18% 2 7% 13% 18% 42%	3778
	21st to end	Night	11% 1 4 12% 34% 38%	4120
November	1st to 10th	Night	15% 3 5% 15% 29% 33%	2397
	11th to 20th	Night	15% 3 6% 16% 30% 31%	2600
	21st to end	Night	21% 4 6% 14% 28% 27%	2600
December	1st to 10th	Night	28% 3 5% 16% 26% 22%	4250
	11th to 20th	Night	15% 2 4 13% 30% 36%	4817
	21st to end	Night	11% 3 4 13% 37% 32%	6727

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	8% 14% 33% 33% 11%	300
	11th to 20th	Day	10% 13% 35% 32% 10% 1	300
	21st to end	Day	3 13% 34% 38% 11% 1	330
February	1st to 10th	Day	5% 13% 34% 33% 13% 3	300
	11th to 20th	Day	11% 14% 37% 29% 9% 1	300
	21st to end	Day	8% 20% 35% 28% 7% 2	249
March	1st to 10th	Day	12% 12% 37% 31% 8% 1	300
	11th to 20th	Day	13% 17% 33% 26% 9% 2	475
	21st to end	Day	5% 24% 40% 23% 7% 1	550
April	1st to 10th	Day	8% 20% 35% 29% 7% 1	500
	11th to 20th	Day	6% 23% 37% 26% 6% 1	492
	21st to end	Day	4 16% 40% 30% 10% 1	500
May	1st to 10th	Day	5% 14% 41% 30% 10%	503
	11th to 20th	Day	7% 10% 31% 33% 17% 3	538
	21st to end	Day	5% 6% 31% 40% 17% 1	789
June	1st to 10th	Day	3 3 17% 44% 30% 3	730
	11th to 20th	Day	2 3 19% 41% 30% 5%	730
	21st to end	Day	7% 1 11% 34% 38% 9%	730
July	1st to 10th	Day	6% 1 6% 26% 45% 16%	622
	11th to 20th	Day	3 4 29% 41% 23%	524
	21st to end	Day	2 1 3 27% 43% 23%	532
August	1st to 10th	Day	3 4 22% 47% 24%	487
	11th to 20th	Day	4 1 7% 27% 42% 18%	477
	21st to end	Day	5% 1 6% 23% 40% 25%	539
September	1st to 10th	Day	9% 1 9% 30% 37% 15%	490
	11th to 20th	Day	5% 1 7% 31% 42% 14%	414
	21st to end	Day	7% 2 11% 28% 34% 17%	300
October	1st to 10th	Day	10% 2 16% 30% 33% 9%	300
	11th to 20th	Day	8% 5% 17% 36% 27% 8%	300
	21st to end	Day	7% 9% 24% 27% 24% 9%	330
November	1st to 10th	Day	12% 8% 29% 28% 19% 4	300
	11th to 20th	Day	6% 12% 22% 33% 22% 5%	300
	21st to end	Day	10% 13% 33% 28% 12% 4	300
December	1st to 10th	Day	15% 12% 21% 35% 15% 2	300
	11th to 20th	Day	4 15% 26% 40% 14% 2	300
	21st to end	Day	7% 14% 36% 32% 10% 2	330
January	1st to 10th	Night	8% 10% 32% 37% 12% 1	800
	11th to 20th	Night	7% 9% 37% 34% 10% 2	800
	21st to end	Night	6% 9% 35% 38% 11% 1	880
February	1st to 10th	Night	5% 12% 36% 35% 12% 1	800
	11th to 20th	Night	8% 10% 38% 37% 6% 1	784
	21st to end	Night	6% 17% 43% 28% 5%	660
March	1st to 10th	Night	8% 12% 37% 35% 8% 1	800
	11th to 20th	Night	11% 13% 30% 32% 13%	800
	21st to end	Night	3 12% 45% 33% 6%	712
April	1st to 10th	Night	6% 12% 42% 35% 5%	600
	11th to 20th	Night	5% 11% 42% 36% 6%	593
	21st to end	Night	3 11% 42% 36% 8%	600
May	1st to 10th	Night	4 5% 43% 41% 7%	600
	11th to 20th	Night	7% 6% 31% 42% 13%	591
	21st to end	Night	4 4 29% 50% 12%	650
June	1st to 10th	Night	2 3 20% 55% 19% 1	600
	11th to 20th	Night	2 1 20% 57% 20%	600
	21st to end	Night	5% 1 13% 50% 31% 1	600
July	1st to 10th	Night	6% 7% 42% 42% 3	585
	11th to 20th	Night	3 4 41% 49% 3	582
	21st to end	Night	4 1 5% 32% 53% 5%	624
August	1st to 10th	Night	4 4 26% 62% 4	567
	11th to 20th	Night	4 4 27% 56% 8%	564
	21st to end	Night	6% 1 4 30% 55% 6%	627
September	1st to 10th	Night	9% 1 5% 37% 43% 6%	570
	11th to 20th	Night	8% 1 4 41% 44% 2	570
	21st to end	Night	8% 1 9% 44% 35% 3	570
October	1st to 10th	Night	8% 2 16% 46% 26% 2	594
	11th to 20th	Night	8% 5% 18% 44% 22% 3	760
	21st to end	Night	6% 7% 21% 36% 25% 6%	836
November	1st to 10th	Night	7% 4 24% 38% 24% 3	837
	11th to 20th	Night	4 6% 25% 43% 20% 2	1000
	21st to end	Night	8% 10% 29% 36% 16% 2	1000
December	1st to 10th	Night	10% 8% 30% 36% 14% 1	1000
	11th to 20th	Night	6% 10% 35% 37% 12% 1	1000
	21st to end	Night	5% 13% 36% 35% 10% 1	1100

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