Chihuahua
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chihuahua clear sky chart from 2005-11-06 to 2025-05-26.

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%	115159
	Night	4 4 1 5% 4 4 4 3 5% 7% 59%	114417
Transparency	Day	18% 5% 8% 15% 25% 29%	118848
	Night	24% 5% 7% 13% 24% 27%	118898
Seeing	Day	6% 7% 23% 30% 26% 8%	14949
	Night	7% 4 20% 39% 27% 4	24886

By Month

Percentage Cloud Cover SE (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 2 1 2 2 2 2 2 4 7% 75%	4098
	11th to 20th	Day	1 1 1 2 1 2 3 3 4 5% 77%	4100
	21st to end	Day	2 3 1 4 3 3 3 3 5% 7% 66%	4993
February	1st to 10th	Day	3 3 2 4 4 3 3 2 4 5% 68%	2000
	11th to 20th	Day	2 3 1 3 3 3 3 3 4 6% 69%	1949
	21st to end	Day	3 2 2 2 2 3 4 5% 7% 70%	1669
March	1st to 10th	Day	2 2 1 3 3 3 4 3 5% 6% 67%	4954
	11th to 20th	Day	2 3 1 3 3 3 2 2 4 5% 72%	5000
	21st to end	Day	2 3 1 3 2 3 3 3 5% 6% 69%	5588
April	1st to 10th	Day	3 3 1 3 2 3 4 3 5% 6% 67%	2400
	11th to 20th	Day	2 2 1 3 2 3 4 2 5% 6% 70%	2374
	21st to end	Day	3 3 1 3 3 2 3 3 4 5% 72%	2400
May	1st to 10th	Day	1 1 1 2 1 2 3 2 4 5% 79%	3885
	11th to 20th	Day	2 3 1 3 3 2 3 3 4 6% 69%	3885
	21st to end	Day	1 1 1 1 2 2 3 2 4 6% 78%	4191
June	1st to 10th	Day	3 3 1 4 4 3 4 4 6% 7% 62%	2280
	11th to 20th	Day	3 2 1 5% 4 4 5% 5% 7% 8% 57%	2399
	21st to end	Day	4 3 1 4 4 5% 5% 5% 7% 10% 51%	2470
July	1st to 10th	Day	4 3 2 5% 5% 5% 6% 5% 7% 10% 47%	4110
	11th to 20th	Day	3 2 1 3 4 5% 5% 6% 8% 12% 51%	4048
	21st to end	Day	4 4 2 4 4 5% 6% 5% 8% 11% 47%	4117
August	1st to 10th	Day	2 2 1 4 4 5% 5% 5% 8% 10% 56%	3785
	11th to 20th	Day	3 2 1 4 4 5% 6% 5% 7% 11% 51%	3726
	21st to end	Day	4 2 1 4 5% 5% 5% 5% 7% 11% 50%	4180
September	1st to 10th	Day	8% 5% 3 6% 5% 5% 6% 5% 7% 9% 39%	2280
	11th to 20th	Day	9% 4 2 5% 5% 5% 5% 4 7% 9% 46%	2280
	21st to end	Day	8% 4 1 4 3 4 4 4 6% 7% 56%	2104
October	1st to 10th	Day	3 2 1 4 3 4 5% 4 7% 6% 62%	1907
	11th to 20th	Day	6% 3 2 3 3 2 3 2 4 7% 65%	1900
	21st to end	Day	4 2 1 2 1 1 2 2 3 5% 78%	2090
November	1st to 10th	Day	3 2 1 3 2 2 2 2 4 5% 74%	1959
	11th to 20th	Day	5% 2 1 3 2 3 3 2 3 5% 72%	2000
	21st to end	Day	4 4 1 4 3 3 3 3 6% 6% 62%	2000
December	1st to 10th	Day	3 6% 2 3 3 3 3 3 6% 7% 62%	3270
	11th to 20th	Day	2 2 1 3 2 2 3 2 4 6% 71%	3774
	21st to end	Day	1 2 1 2 1 2 2 2 4 6% 78%	4994
January	1st to 10th	Night	2 3 1 2 2 2 2 2 3 4 76%	5845
	11th to 20th	Night	2 1 2 2 3 3 3 5% 6% 73%	5860
	21st to end	Night	4 4 2 4 3 4 4 3 4 6% 62%	5984
February	1st to 10th	Night	4 3 2 3 3 3 2 3 4 5% 69%	2400
	11th to 20th	Night	4 4 1 4 3 2 3 3 5% 7% 64%	2338
	21st to end	Night	2 4 1 2 2 2 3 3 5% 8% 67%	1955
March	1st to 10th	Night	3 3 1 4 2 2 3 3 6% 6% 66%	4940
	11th to 20th	Night	3 3 1 3 2 2 3 3 4 6% 69%	5000
	21st to end	Night	4 4 1 3 2 2 3 2 4 6% 69%	5365
April	1st to 10th	Night	4 3 1 3 3 3 3 3 6% 7% 66%	2000
	11th to 20th	Night	3 4 1 4 2 3 3 3 4 7% 66%	1977
	21st to end	Night	5% 3 1 4 2 3 3 2 4 5% 69%	2000
May	1st to 10th	Night	2 2 1 2 2 2 2 2 4 5% 75%	3240
	11th to 20th	Night	5% 4 2 4 3 3 3 3 5% 7% 64%	3240
	21st to end	Night	3 4 1 4 2 3 3 3 5% 5% 66%	3492
June	1st to 10th	Night	5% 4 2 6% 6% 6% 6% 4 8% 8% 45%	1900
	11th to 20th	Night	6% 5% 2 7% 6% 7% 6% 5% 7% 9% 42%	1773
	21st to end	Night	8% 5% 2 7% 7% 7% 7% 6% 8% 10% 33%	1710
July	1st to 10th	Night	7% 8% 3 12% 7% 8% 8% 6% 9% 9% 23%	2860
	11th to 20th	Night	5% 4 3 9% 6% 6% 7% 7% 9% 13% 32%	2917
	21st to end	Night	7% 6% 3 8% 7% 7% 7% 6% 8% 11% 30%	3446
August	1st to 10th	Night	5% 6% 3 9% 7% 8% 9% 6% 9% 9% 30%	3155
	11th to 20th	Night	6% 5% 3 10% 7% 8% 8% 7% 10% 10% 26%	3113
	21st to end	Night	6% 5% 3 9% 7% 6% 7% 6% 9% 12% 31%	3487
September	1st to 10th	Night	13% 8% 3 9% 8% 6% 6% 5% 7% 9% 27%	1900
	11th to 20th	Night	13% 7% 3 7% 6% 7% 6% 5% 7% 8% 31%	1900
	21st to end	Night	10% 5% 2 7% 5% 6% 6% 4 8% 9% 39%	2076
October	1st to 10th	Night	6% 4 2 5% 5% 4 4 3 5% 6% 57%	2266
	11th to 20th	Night	7% 3 1 5% 3 3 4 3 5% 6% 59%	2280
	21st to end	Night	5% 2 1 2 2 2 3 2 3 4 74%	2508
November	1st to 10th	Night	6% 2 1 2 2 2 2 2 3 4 74%	2340
	11th to 20th	Night	5% 3 1 3 3 2 4 2 5% 4 68%	2400
	21st to end	Night	4 4 2 4 3 3 4 3 3 5% 66%	2400
December	1st to 10th	Night	3 4 1 5% 4 4 4 3 6% 7% 59%	3920
	11th to 20th	Night	1 3 1 3 1 2 2 3 4 6% 74%	4446
	21st to end	Night	2 2 1 2 2 2 2 2 3 6% 76%	5984

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	12% 2 3 12% 36% 34%	4099
	11th to 20th	Day	12% 3 3 14% 30% 39%	4100
	21st to end	Day	19% 4 4 17% 31% 25%	4993
February	1st to 10th	Day	21% 3 4 9% 25% 38%	2000
	11th to 20th	Day	18% 3 6% 11% 30% 32%	1959
	21st to end	Day	14% 3 6% 9% 29% 39%	1669
March	1st to 10th	Day	17% 3 5% 7% 21% 47%	4954
	11th to 20th	Day	15% 3 4 6% 18% 54%	5000
	21st to end	Day	15% 3 4 8% 26% 43%	5590
April	1st to 10th	Day	18% 4 5% 9% 22% 43%	2400
	11th to 20th	Day	14% 3 7% 8% 24% 44%	2374
	21st to end	Day	15% 2 4 8% 24% 46%	2400
May	1st to 10th	Day	10% 2 3 7% 17% 61%	3920
	11th to 20th	Day	16% 3 7% 8% 21% 45%	3888
	21st to end	Day	8% 2 5% 9% 20% 55%	4202
June	1st to 10th	Day	17% 5% 9% 17% 30% 23%	2280
	11th to 20th	Day	20% 5% 8% 15% 25% 27%	2399
	21st to end	Day	25% 7% 12% 23% 19% 15%	2470
July	1st to 10th	Day	28% 10% 17% 24% 14% 7%	4046
	11th to 20th	Day	21% 9% 21% 32% 14% 3	3979
	21st to end	Day	26% 11% 17% 25% 17% 4	3988
August	1st to 10th	Day	19% 8% 20% 33% 18% 2	3772
	11th to 20th	Day	24% 10% 19% 30% 15% 2	3762
	21st to end	Day	25% 9% 20% 29% 16% 2	4179
September	1st to 10th	Day	38% 11% 16% 18% 12% 6%	2280
	11th to 20th	Day	33% 10% 13% 17% 20% 8%	2280
	21st to end	Day	25% 7% 13% 20% 23% 11%	2104
October	1st to 10th	Day	12% 5% 6% 12% 27% 38%	3177
	11th to 20th	Day	13% 4 6% 18% 26% 32%	3150
	21st to end	Day	7% 2 3 12% 44% 32%	3438
November	1st to 10th	Day	14% 3 6% 18% 34% 24%	1959
	11th to 20th	Day	17% 3 4 19% 33% 24%	2000
	21st to end	Day	23% 5% 6% 18% 25% 25%	2000
December	1st to 10th	Day	22% 4 4 16% 32% 22%	3270
	11th to 20th	Day	16% 3 4 13% 40% 24%	3773
	21st to end	Day	10% 2 4 10% 39% 36%	4994
January	1st to 10th	Night	13% 2 3 12% 38% 31%	5845
	11th to 20th	Night	13% 3 5% 12% 29% 38%	5860
	21st to end	Night	23% 5% 4 15% 31% 22%	5984
February	1st to 10th	Night	19% 3 6% 12% 25% 36%	2400
	11th to 20th	Night	21% 4 7% 10% 28% 31%	2338
	21st to end	Night	17% 4 5% 11% 29% 34%	1955
March	1st to 10th	Night	19% 4 3 6% 23% 45%	4940
	11th to 20th	Night	16% 3 5% 5% 23% 48%	5000
	21st to end	Night	17% 4 3 9% 28% 38%	5365
April	1st to 10th	Night	18% 3 5% 11% 25% 38%	2000
	11th to 20th	Night	20% 5% 5% 8% 25% 38%	1977
	21st to end	Night	19% 3 4 9% 23% 42%	2000
May	1st to 10th	Night	13% 3 4 7% 15% 58%	3270
	11th to 20th	Night	20% 4 6% 8% 20% 42%	3241
	21st to end	Night	19% 3 6% 7% 15% 50%	3502
June	1st to 10th	Night	33% 7% 10% 16% 19% 14%	1900
	11th to 20th	Night	36% 7% 10% 13% 19% 15%	1773
	21st to end	Night	40% 11% 13% 16% 10% 10%	1710
July	1st to 10th	Night	51% 12% 15% 13% 6% 3	2815
	11th to 20th	Night	37% 11% 20% 25% 5% 2	2863
	21st to end	Night	42% 10% 12% 19% 16% 1	3336
August	1st to 10th	Night	43% 11% 13% 20% 12% 1	3144
	11th to 20th	Night	45% 12% 16% 18% 8% 1	3143
	21st to end	Night	41% 11% 13% 21% 11% 2	3487
September	1st to 10th	Night	50% 10% 15% 12% 7% 5%	1900
	11th to 20th	Night	47% 10% 12% 11% 12% 8%	1900
	21st to end	Night	39% 11% 12% 13% 16% 10%	2076
October	1st to 10th	Night	18% 5% 6% 11% 24% 37%	3786
	11th to 20th	Night	22% 5% 6% 15% 24% 28%	3778
	21st to end	Night	11% 2 3 14% 41% 28%	4120
November	1st to 10th	Night	15% 3 7% 16% 37% 22%	2340
	11th to 20th	Night	20% 4 7% 16% 30% 23%	2400
	21st to end	Night	21% 4 7% 18% 26% 23%	2400
December	1st to 10th	Night	25% 4 5% 20% 29% 18%	3920
	11th to 20th	Night	13% 3 5% 13% 44% 21%	4446
	21st to end	Night	13% 2 3 11% 38% 32%	5984

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% 9% 32% 34% 17% 1	300
	11th to 20th	Day	3 8% 31% 42% 16% 1	300
	21st to end	Day	7% 12% 35% 34% 11% 1	330
February	1st to 10th	Day	6% 9% 31% 31% 20% 3	300
	11th to 20th	Day	7% 12% 39% 30% 11% 1	300
	21st to end	Day	8% 15% 40% 29% 8% 1	268
March	1st to 10th	Day	8% 20% 39% 24% 8% 1	500
	11th to 20th	Day	9% 19% 37% 24% 9% 2	500
	21st to end	Day	9% 17% 44% 19% 9% 2	550
April	1st to 10th	Day	8% 15% 40% 27% 9% 1	500
	11th to 20th	Day	6% 16% 40% 27% 10% 1	492
	21st to end	Day	6% 13% 40% 30% 10% 1	500
May	1st to 10th	Day	4 13% 40% 31% 11% 2	503
	11th to 20th	Day	5% 9% 34% 36% 14% 2	528
	21st to end	Day	4 7% 33% 36% 17% 2	550
June	1st to 10th	Day	6% 2 21% 39% 27% 5%	490
	11th to 20th	Day	2 1 14% 40% 38% 5%	490
	21st to end	Day	3 1 7% 34% 42% 12%	490
July	1st to 10th	Day	5% 2 4 27% 44% 19%	486
	11th to 20th	Day	4 1 3 26% 53% 13%	484
	21st to end	Day	4 1 3 26% 48% 19%	531
August	1st to 10th	Day	2 3 21% 55% 20%	487
	11th to 20th	Day	5% 1 5% 24% 41% 24%	477
	21st to end	Day	6% 1 4 24% 44% 21%	539
September	1st to 10th	Day	7% 2 6% 27% 42% 16%	490
	11th to 20th	Day	8% 1 5% 24% 47% 16%	490
	21st to end	Day	8% 1 8% 26% 40% 17%	314
October	1st to 10th	Day	4 2 12% 31% 34% 17%	300
	11th to 20th	Day	6% 4 15% 33% 29% 13%	300
	21st to end	Day	4 5% 20% 33% 24% 13%	330
November	1st to 10th	Day	2 6% 26% 33% 25% 8%	300
	11th to 20th	Day	5% 5% 21% 38% 23% 7%	300
	21st to end	Day	10% 10% 30% 30% 17% 3	300
December	1st to 10th	Day	6% 6% 25% 36% 23% 3	300
	11th to 20th	Day	4 7% 30% 39% 16% 3	300
	21st to end	Day	6% 9% 31% 35% 16% 2	330
January	1st to 10th	Night	6% 3 23% 47% 19% 2	800
	11th to 20th	Night	5% 3 22% 45% 24% 2	800
	21st to end	Night	6% 8% 28% 42% 15% 1	880
February	1st to 10th	Night	5% 8% 25% 39% 21% 3	800
	11th to 20th	Night	5% 7% 31% 43% 13% 1	784
	21st to end	Night	6% 8% 36% 39% 10%	660
March	1st to 10th	Night	8% 8% 34% 39% 10% 1	800
	11th to 20th	Night	8% 9% 30% 40% 14% 1	800
	21st to end	Night	5% 6% 35% 40% 12% 1	833
April	1st to 10th	Night	7% 8% 38% 39% 9% 1	600
	11th to 20th	Night	4 8% 41% 40% 7%	593
	21st to end	Night	6% 7% 38% 41% 8%	600
May	1st to 10th	Night	6% 5% 43% 38% 9% 1	600
	11th to 20th	Night	7% 3 31% 48% 10% 1	591
	21st to end	Night	3 4 26% 48% 17%	634
June	1st to 10th	Night	6% 3 15% 48% 27% 2	570
	11th to 20th	Night	6% 1 12% 45% 35% 1	570
	21st to end	Night	7% 2 9% 38% 41% 2	570
July	1st to 10th	Night	10% 2 6% 28% 51% 3	555
	11th to 20th	Night	9% 1 5% 27% 53% 5%	552
	21st to end	Night	9% 1 5% 27% 50% 7%	624
August	1st to 10th	Night	8% 1 4 23% 53% 11%	567
	11th to 20th	Night	9% 2 6% 23% 46% 14%	564
	21st to end	Night	9% 2 6% 19% 54% 10%	627
September	1st to 10th	Night	13% 2 7% 21% 49% 8%	570
	11th to 20th	Night	15% 1 7% 26% 48% 4	570
	21st to end	Night	11% 1 8% 31% 44% 6%	570
October	1st to 10th	Night	5% 2 9% 34% 44% 6%	746
	11th to 20th	Night	8% 2 11% 43% 31% 6%	760
	21st to end	Night	4 4 11% 42% 31% 8%	836
November	1st to 10th	Night	6% 1 13% 40% 33% 6%	780
	11th to 20th	Night	6% 2 13% 47% 30% 3	800
	21st to end	Night	6% 4 20% 43% 22% 5%	800
December	1st to 10th	Night	6% 2 20% 46% 23% 4	800
	11th to 20th	Night	5% 3 21% 48% 20% 4	800
	21st to end	Night	5% 6% 24% 43% 19% 4	880

Page generated at 2025-05-23 06:20:59. Version ac07

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