Navajo Peak
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Navajo Peak clear sky chart from 2005-11-06 to 2026-02-16.

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	5% 8% 3 6% 4 4 4 4 5% 6% 51%	139555
	Night	5% 9% 3 6% 3 3 4 3 5% 6% 53%	138812
Transparency	Day	21% 38% 6% 13% 16% 6%	134509
	Night	21% 37% 5% 13% 17% 7%	134863
Seeing	Day	16% 21% 26% 22% 12% 3	16912
	Night	12% 9% 24% 34% 18% 3	27155

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 13% 6% 12% 3 3 3 2 4 5% 48%	5096
	11th to 20th	Day	2 6% 4 9% 3 3 3 2 3 4 59%	5340
	21st to end	Day	3 11% 5% 7% 3 3 3 3 4 5% 53%	5844
February	1st to 10th	Day	3 13% 5% 9% 3 3 2 2 3 5% 51%	1890
	11th to 20th	Day	6% 15% 5% 8% 4 3 3 3 4 6% 43%	1931
	21st to end	Day	5% 15% 7% 9% 2 3 3 3 4 5% 44%	1650
March	1st to 10th	Day	4 16% 8% 7% 3 3 3 2 4 5% 45%	4811
	11th to 20th	Day	3 18% 9% 8% 4 5% 4 3 5% 6% 35%	5000
	21st to end	Day	4 18% 5% 6% 4 3 4 3 4 6% 42%	5610
April	1st to 10th	Day	6% 12% 3 6% 4 3 3 3 4 7% 49%	2400
	11th to 20th	Day	5% 14% 3 5% 4 4 4 4 5% 7% 46%	2371
	21st to end	Day	7% 13% 2 4 3 3 4 4 5% 6% 48%	2400
May	1st to 10th	Day	7% 10% 3 8% 5% 5% 5% 4 5% 6% 43%	5474
	11th to 20th	Day	5% 9% 2 5% 4 4 4 4 5% 6% 51%	5996
	21st to end	Day	4 4 1 4 3 4 4 3 6% 7% 61%	6925
June	1st to 10th	Day	5% 3 1 4 3 4 4 4 7% 8% 57%	2800
	11th to 20th	Day	4 3 1 3 2 2 4 3 5% 6% 67%	2800
	21st to end	Day	5% 4 2 5% 4 4 5% 4 6% 7% 56%	2800
July	1st to 10th	Day	4 3 1 4 4 4 5% 4 5% 6% 60%	6339
	11th to 20th	Day	2 2 1 6% 5% 7% 9% 7% 10% 10% 40%	5927
	21st to end	Day	4 4 2 7% 6% 7% 8% 6% 8% 8% 41%	6401
August	1st to 10th	Day	7% 4 2 6% 6% 6% 7% 6% 7% 8% 42%	5779
	11th to 20th	Day	4 3 2 6% 5% 5% 6% 6% 8% 7% 49%	5417
	21st to end	Day	8% 6% 2 8% 6% 7% 7% 6% 8% 9% 33%	5984
September	1st to 10th	Day	11% 6% 2 6% 4 4 5% 4 5% 6% 48%	2400
	11th to 20th	Day	11% 5% 2 5% 4 3 5% 4 5% 5% 52%	2400
	21st to end	Day	12% 4 1 4 3 3 3 3 4 5% 58%	2141
October	1st to 10th	Day	9% 4 1 2 2 2 3 3 4 6% 65%	3270
	11th to 20th	Day	14% 7% 2 5% 4 3 3 3 4 5% 49%	3250
	21st to end	Day	7% 8% 3 3 2 2 1 2 2 5% 66%	3548
November	1st to 10th	Day	5% 7% 1 3 2 2 2 3 4 6% 65%	1985
	11th to 20th	Day	4 7% 2 3 2 2 2 3 4 6% 65%	1890
	21st to end	Day	7% 10% 3 4 3 2 2 2 3 4 60%	1788
December	1st to 10th	Day	3 6% 2 4 1 1 2 2 4 6% 68%	2700
	11th to 20th	Day	4 10% 3 5% 2 2 3 3 5% 8% 56%	3106
	21st to end	Day	3 11% 3 7% 2 2 3 2 4 6% 56%	4092
January	1st to 10th	Night	2 11% 5% 12% 4 3 3 3 5% 5% 47%	7868
	11th to 20th	Night	1 8% 4 8% 2 2 2 2 4 4 61%	7650
	21st to end	Night	3 11% 4 7% 3 3 3 2 3 5% 55%	8370
February	1st to 10th	Night	4 13% 5% 6% 2 2 2 2 3 5% 57%	2730
	11th to 20th	Night	5% 16% 4 6% 3 3 3 2 3 4 51%	2465
	21st to end	Night	5% 17% 5% 7% 2 2 2 2 3 5% 50%	1980
March	1st to 10th	Night	4 19% 6% 7% 3 3 2 2 3 5% 47%	5072
	11th to 20th	Night	4 19% 4 6% 3 3 4 3 5% 5% 45%	5000
	21st to end	Night	7% 18% 4 7% 3 3 3 3 4 5% 45%	5357
April	1st to 10th	Night	8% 13% 3 4 4 3 3 3 4 5% 51%	2000
	11th to 20th	Night	9% 13% 2 5% 3 3 3 3 4 5% 50%	1977
	21st to end	Night	9% 10% 1 3 3 3 3 3 4 5% 56%	2000
May	1st to 10th	Night	9% 9% 2 6% 3 4 4 3 4 6% 49%	4503
	11th to 20th	Night	7% 7% 2 4 3 4 4 3 5% 6% 56%	3901
	21st to end	Night	6% 6% 2 4 3 3 3 3 5% 5% 60%	3972
June	1st to 10th	Night	5% 4 1 3 4 4 4 3 5% 6% 61%	1600
	11th to 20th	Night	4 3 1 3 2 2 3 3 4 6% 70%	1600
	21st to end	Night	6% 2 2 5% 4 4 4 4 7% 6% 56%	1600
July	1st to 10th	Night	5% 3 1 6% 4 4 5% 4 5% 6% 57%	3640
	11th to 20th	Night	2 3 1 4 5% 5% 7% 6% 11% 15% 41%	4047
	21st to end	Night	4 4 2 7% 6% 7% 7% 7% 9% 10% 38%	4472
August	1st to 10th	Night	6% 4 2 6% 5% 6% 6% 6% 8% 10% 40%	4033
	11th to 20th	Night	4 3 2 6% 5% 5% 6% 6% 8% 10% 44%	4432
	21st to end	Night	10% 6% 3 8% 6% 6% 8% 6% 8% 9% 29%	4993
September	1st to 10th	Night	7% 5% 2 5% 5% 5% 6% 4 7% 7% 47%	2000
	11th to 20th	Night	10% 4 1 4 4 3 4 3 4 5% 57%	2000
	21st to end	Night	9% 4 1 4 3 2 2 2 4 5% 62%	2252
October	1st to 10th	Night	8% 3 1 3 2 2 2 2 3 4 68%	3920
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 4 4 54%	3898
	21st to end	Night	8% 7% 2 3 2 2 2 1 3 4 68%	4252
November	1st to 10th	Night	6% 6% 1 3 2 2 2 2 5% 5% 65%	2509
	11th to 20th	Night	5% 6% 1 3 2 2 2 2 4 5% 69%	2730
	21st to end	Night	8% 12% 2 4 2 2 2 2 3 4 57%	2830
December	1st to 10th	Night	4 6% 2 4 2 2 2 1 3 4 69%	4710
	11th to 20th	Night	4 9% 2 4 2 2 3 3 5% 6% 60%	5321
	21st to end	Night	4 11% 4 8% 4 3 2 2 3 5% 54%	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	34% 22% 6% 22% 12% 5%	5099
	11th to 20th	Day	24% 23% 5% 15% 21% 13%	5340
	21st to end	Day	24% 24% 4 14% 23% 12%	5844
February	1st to 10th	Day	15% 58% 4 10% 9% 4	1890
	11th to 20th	Day	17% 59% 3 10% 8% 2	1940
	21st to end	Day	18% 61% 1 5% 11% 4	1650
March	1st to 10th	Day	28% 31% 3 11% 18% 9%	4811
	11th to 20th	Day	37% 32% 3 15% 11% 1	5000
	21st to end	Day	29% 32% 9% 17% 11% 1	5610
April	1st to 10th	Day	14% 62% 4 10% 9% 1	2400
	11th to 20th	Day	15% 62% 3 8% 10% 2	2374
	21st to end	Day	17% 62% 3 9% 8% 1	2400
May	1st to 10th	Day	31% 32% 8% 12% 12% 5%	5474
	11th to 20th	Day	21% 32% 4 19% 21% 3	5999
	21st to end	Day	14% 30% 5% 16% 31% 3	6926
June	1st to 10th	Day	9% 64% 4 10% 9% 4	2800
	11th to 20th	Day	7% 62% 4 6% 12% 10%	2800
	21st to end	Day	9% 61% 4 9% 10% 8%	2800
July	1st to 10th	Day	16% 27% 4 7% 20% 25%	6271
	11th to 20th	Day	26% 30% 16% 16% 6% 5%	5856
	21st to end	Day	26% 30% 12% 14% 14% 3	6217
August	1st to 10th	Day	34% 39% 12% 8% 5% 2	4208
	11th to 20th	Day	20% 40% 10% 11% 14% 5%	3921
	21st to end	Day	34% 39% 8% 9% 10% 1	4311
September	1st to 10th	Day	15% 59% 4 10% 9% 3	2400
	11th to 20th	Day	15% 58% 2 8% 12% 5%	2400
	21st to end	Day	15% 58% 2 9% 13% 3	2141
October	1st to 10th	Day	12% 36% 1 12% 29% 10%	3270
	11th to 20th	Day	30% 36% 3 14% 14% 4	3250
	21st to end	Day	17% 35% 2 13% 28% 5%	3548
November	1st to 10th	Day	11% 53% 2 13% 17% 4	1985
	11th to 20th	Day	12% 54% 3 12% 15% 5%	1890
	21st to end	Day	16% 53% 3 11% 10% 6%	1788
December	1st to 10th	Day	10% 34% 4 18% 30% 4	2700
	11th to 20th	Day	15% 31% 4 22% 24% 4	3104
	21st to end	Day	19% 26% 5% 20% 21% 9%	4092
January	1st to 10th	Night	33% 22% 4 19% 15% 6%	7869
	11th to 20th	Night	21% 23% 3 16% 22% 15%	7650
	21st to end	Night	25% 23% 3 13% 25% 11%	8370
February	1st to 10th	Night	14% 59% 4 9% 10% 5%	2730
	11th to 20th	Night	15% 59% 5% 10% 9% 2	2465
	21st to end	Night	17% 61% 1 5% 13% 4	1980
March	1st to 10th	Night	30% 30% 2 9% 19% 10%	5072
	11th to 20th	Night	31% 32% 3 12% 18% 5%	5000
	21st to end	Night	29% 33% 6% 20% 12% 1	5357
April	1st to 10th	Night	14% 62% 3 10% 10% 1	2000
	11th to 20th	Night	15% 62% 2 8% 11% 3	1977
	21st to end	Night	15% 62% 4 9% 9% 1	2000
May	1st to 10th	Night	27% 31% 8% 14% 16% 3	4500
	11th to 20th	Night	17% 30% 5% 22% 21% 5%	3902
	21st to end	Night	16% 29% 6% 12% 29% 6%	3972
June	1st to 10th	Night	11% 62% 4 9% 10% 5%	1600
	11th to 20th	Night	6% 62% 3 7% 11% 11%	1600
	21st to end	Night	10% 61% 5% 6% 9% 9%	1600
July	1st to 10th	Night	19% 26% 6% 6% 16% 27%	3600
	11th to 20th	Night	20% 29% 19% 22% 5% 6%	3995
	21st to end	Night	25% 29% 14% 17% 14% 1	4344
August	1st to 10th	Night	32% 40% 14% 7% 5% 2	2928
	11th to 20th	Night	23% 40% 14% 6% 14% 4	3204
	21st to end	Night	33% 38% 8% 11% 9% 1	3597
September	1st to 10th	Night	14% 59% 5% 10% 10% 2	2000
	11th to 20th	Night	12% 57% 3 9% 14% 6%	2000
	21st to end	Night	13% 57% 2 9% 15% 3	2252
October	1st to 10th	Night	9% 36% 2 18% 26% 9%	3920
	11th to 20th	Night	27% 36% 2 16% 15% 4	3898
	21st to end	Night	16% 35% 1 14% 25% 9%	4252
November	1st to 10th	Night	11% 53% 2 12% 18% 4	2509
	11th to 20th	Night	11% 54% 2 14% 16% 4	2730
	21st to end	Night	18% 54% 3 10% 9% 6%	2830
December	1st to 10th	Night	11% 34% 3 20% 27% 6%	4710
	11th to 20th	Night	14% 32% 3 16% 27% 8%	5322
	21st to end	Night	25% 26% 6% 14% 20% 10%	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	21% 21% 33% 18% 6% 1	330
	11th to 20th	Day	19% 22% 30% 23% 5%	330
	21st to end	Day	16% 22% 34% 19% 9% 1	363
February	1st to 10th	Day	21% 26% 30% 18% 5% 1	330
	11th to 20th	Day	29% 27% 25% 15% 4	315
	21st to end	Day	29% 29% 27% 13% 3	249
March	1st to 10th	Day	26% 29% 22% 19% 3 1	430
	11th to 20th	Day	24% 30% 27% 14% 5% 1	500
	21st to end	Day	28% 35% 26% 8% 3	550
April	1st to 10th	Day	22% 35% 27% 10% 5% 1	500
	11th to 20th	Day	28% 36% 24% 8% 4	492
	21st to end	Day	23% 32% 31% 11% 3	500
May	1st to 10th	Day	25% 30% 28% 12% 5%	503
	11th to 20th	Day	19% 24% 27% 20% 8% 2	592
	21st to end	Day	15% 22% 27% 23% 11% 2	789
June	1st to 10th	Day	7% 15% 27% 29% 18% 4	730
	11th to 20th	Day	9% 22% 30% 22% 14% 4	730
	21st to end	Day	8% 18% 27% 25% 16% 5%	730
July	1st to 10th	Day	8% 13% 18% 30% 25% 6%	721
	11th to 20th	Day	7% 6% 21% 35% 22% 8%	543
	21st to end	Day	9% 5% 17% 37% 26% 5%	575
August	1st to 10th	Day	12% 14% 19% 32% 17% 6%	527
	11th to 20th	Day	8% 12% 27% 32% 16% 5%	517
	21st to end	Day	10% 11% 22% 32% 21% 4	583
September	1st to 10th	Day	11% 12% 27% 27% 17% 6%	530
	11th to 20th	Day	11% 18% 34% 22% 11% 4	530
	21st to end	Day	16% 17% 24% 26% 10% 7%	387
October	1st to 10th	Day	18% 22% 19% 22% 15% 5%	330
	11th to 20th	Day	24% 21% 22% 16% 13% 4	330
	21st to end	Day	20% 23% 23% 22% 10% 2	363
November	1st to 10th	Day	20% 28% 21% 20% 10% 1	330
	11th to 20th	Day	14% 23% 26% 24% 11% 2	330
	21st to end	Day	20% 19% 28% 23% 9% 1	330
December	1st to 10th	Day	18% 19% 32% 22% 8% 1	330
	11th to 20th	Day	16% 23% 27% 24% 8% 2	330
	21st to end	Day	24% 21% 32% 19% 3	363
January	1st to 10th	Night	10% 9% 26% 37% 15% 3	938
	11th to 20th	Night	12% 9% 26% 37% 14% 2	840
	21st to end	Night	11% 10% 30% 34% 12% 3	924
February	1st to 10th	Night	13% 13% 30% 34% 10% 1	840
	11th to 20th	Night	14% 14% 30% 31% 9% 1	804
	21st to end	Night	17% 13% 34% 30% 5%	660
March	1st to 10th	Night	17% 15% 28% 29% 10% 1	800
	11th to 20th	Night	12% 14% 26% 36% 13% 1	800
	21st to end	Night	16% 13% 33% 29% 8%	825
April	1st to 10th	Night	17% 16% 34% 27% 7% 1	600
	11th to 20th	Night	16% 14% 31% 31% 8% 1	593
	21st to end	Night	14% 13% 33% 30% 9% 1	600
May	1st to 10th	Night	14% 10% 30% 32% 12% 1	600
	11th to 20th	Night	15% 7% 24% 36% 15% 2	591
	21st to end	Night	11% 12% 28% 31% 17% 1	650
June	1st to 10th	Night	5% 6% 23% 46% 18% 2	600
	11th to 20th	Night	6% 9% 28% 39% 16% 2	600
	21st to end	Night	7% 5% 20% 39% 27% 3	600
July	1st to 10th	Night	6% 4 15% 39% 33% 3	585
	11th to 20th	Night	4 2 9% 38% 39% 8%	582
	21st to end	Night	6% 3 9% 28% 45% 9%	657
August	1st to 10th	Night	8% 2 9% 27% 45% 9%	597
	11th to 20th	Night	7% 3 10% 36% 38% 6%	594
	21st to end	Night	7% 4 10% 35% 37% 7%	660
September	1st to 10th	Night	9% 3 11% 40% 32% 6%	600
	11th to 20th	Night	11% 3 15% 41% 24% 6%	600
	21st to end	Night	10% 6% 15% 35% 27% 7%	711
October	1st to 10th	Night	14% 7% 22% 34% 20% 4	800
	11th to 20th	Night	13% 6% 23% 36% 19% 4	800
	21st to end	Night	11% 9% 23% 34% 19% 5%	880
November	1st to 10th	Night	11% 8% 23% 38% 17% 4	869
	11th to 20th	Night	9% 8% 25% 39% 15% 3	1050
	21st to end	Night	15% 10% 24% 31% 16% 3	1050
December	1st to 10th	Night	12% 11% 29% 34% 12% 1	1050
	11th to 20th	Night	14% 10% 29% 32% 14% 1	1050
	21st to end	Night	15% 13% 29% 34% 8% 2	1155

Page generated at 2026-02-12 23:42:16. Version ac07

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