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 2024-01-15.

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	7% 9% 3 5% 4 2 4 4 5% 6% 51%	74711
	Night	7% 8% 3 5% 4 2 3 4 4 6% 54%	75072
Transparency	Day	34% 6% 9% 21% 22% 7%	74429
	Night	32% 6% 9% 22% 23% 9%	74874
Seeing	Day	15% 21% 25% 23% 13% 3	14105
	Night	11% 9% 22% 34% 20% 3	24347

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 12% 4 6% 3 2 3 3 4 6% 54%	1634
	11th to 20th	Day	5% 11% 5% 6% 4 2 2 3 4 6% 53%	1656
	21st to end	Day	7% 11% 4 8% 3 2 2 3 4 5% 51%	1782
February	1st to 10th	Day	3 14% 5% 8% 4 2 3 2 3 5% 51%	1620
	11th to 20th	Day	7% 14% 5% 8% 4 2 2 4 3 7% 44%	1691
	21st to end	Day	5% 15% 8% 10% 3 2 4 3 4 5% 41%	1480
March	1st to 10th	Day	8% 13% 7% 6% 3 2 3 3 4 6% 44%	1916
	11th to 20th	Day	6% 14% 6% 5% 3 2 3 4 4 6% 47%	1980
	21st to end	Day	7% 16% 6% 6% 4 2 3 3 4 6% 43%	2225
April	1st to 10th	Day	7% 11% 2 4 4 2 3 4 4 8% 50%	2160
	11th to 20th	Day	6% 13% 2 5% 5% 3 4 4 5% 7% 46%	2131
	21st to end	Day	9% 12% 3 3 4 2 4 5% 5% 6% 47%	2160
May	1st to 10th	Day	8% 9% 2 4 4 2 4 5% 5% 7% 49%	2168
	11th to 20th	Day	9% 9% 3 5% 5% 3 5% 4 5% 6% 46%	2358
	21st to end	Day	8% 6% 2 4 4 3 4 4 5% 6% 55%	2724
June	1st to 10th	Day	5% 3 1 3 4 2 4 6% 6% 8% 58%	2520
	11th to 20th	Day	5% 3 1 2 3 2 3 4 5% 6% 67%	2520
	21st to end	Day	4 3 2 5% 4 3 6% 4 6% 7% 57%	2520
July	1st to 10th	Day	7% 4 2 5% 6% 3 6% 7% 7% 8% 46%	2520
	11th to 20th	Day	5% 4 3 5% 6% 4 7% 7% 8% 9% 43%	2359
	21st to end	Day	9% 6% 2 6% 8% 5% 9% 8% 8% 9% 30%	2545
August	1st to 10th	Day	11% 5% 3 6% 6% 4 6% 6% 6% 6% 41%	2328
	11th to 20th	Day	8% 5% 3 6% 6% 4 5% 6% 7% 7% 42%	2149
	21st to end	Day	10% 6% 2 5% 7% 4 5% 5% 6% 8% 43%	2376
September	1st to 10th	Day	12% 6% 2 5% 5% 3 5% 5% 5% 6% 48%	2160
	11th to 20th	Day	11% 5% 2 4 5% 2 4 5% 5% 6% 52%	2160
	21st to end	Day	12% 4 1 3 3 2 3 3 4 5% 59%	1928
October	1st to 10th	Day	15% 7% 1 3 4 2 3 4 4 6% 52%	1800
	11th to 20th	Day	9% 6% 1 3 3 1 2 3 2 4 66%	1800
	21st to end	Day	7% 9% 2 3 2 2 2 2 3 5% 63%	1980
November	1st to 10th	Day	5% 6% 1 3 2 1 3 3 3 6% 67%	1793
	11th to 20th	Day	5% 6% 2 2 2 2 2 3 4 6% 66%	1710
	21st to end	Day	6% 10% 4 4 3 2 2 2 3 5% 59%	1618
December	1st to 10th	Day	6% 11% 3 6% 3 1 3 2 3 6% 55%	1520
	11th to 20th	Day	6% 14% 4 7% 3 2 3 4 5% 6% 47%	1926
	21st to end	Day	4 12% 4 8% 3 1 3 4 4 6% 52%	2794
January	1st to 10th	Night	4 11% 3 6% 3 2 3 3 3 5% 58%	2547
	11th to 20th	Night	4 11% 4 5% 4 2 2 3 3 4 57%	2392
	21st to end	Night	7% 10% 5% 5% 3 1 2 2 4 6% 54%	2574
February	1st to 10th	Night	4 13% 4 5% 2 1 2 2 2 6% 57%	2340
	11th to 20th	Night	6% 14% 4 6% 3 2 3 3 3 5% 52%	2155
	21st to end	Night	5% 18% 5% 7% 3 1 2 2 3 5% 49%	1776
March	1st to 10th	Night	7% 11% 4 5% 4 2 3 3 4 7% 50%	2039
	11th to 20th	Night	7% 12% 4 5% 3 2 3 3 5% 5% 50%	1980
	21st to end	Night	9% 11% 4 5% 2 1 3 3 4 6% 50%	2129
April	1st to 10th	Night	9% 12% 3 4 4 2 3 3 5% 5% 51%	1800
	11th to 20th	Night	9% 12% 2 5% 3 2 3 4 4 5% 50%	1777
	21st to end	Night	10% 9% 2 3 3 2 3 4 4 5% 56%	1800
May	1st to 10th	Night	10% 7% 2 4 3 2 4 3 4 6% 56%	1789
	11th to 20th	Night	9% 8% 3 5% 4 4 5% 4 5% 6% 47%	1533
	21st to end	Night	8% 6% 1 3 3 2 4 4 4 6% 59%	1552
June	1st to 10th	Night	4 3 1 3 4 3 5% 4 5% 6% 62%	1440
	11th to 20th	Night	4 3 1 3 3 2 3 3 4 6% 70%	1440
	21st to end	Night	6% 1 2 3 4 3 5% 5% 7% 7% 57%	1440
July	1st to 10th	Night	5% 3 2 7% 6% 3 7% 7% 8% 9% 42%	1440
	11th to 20th	Night	4 4 3 4 5% 3 5% 7% 9% 10% 47%	1595
	21st to end	Night	8% 5% 2 5% 7% 5% 6% 8% 10% 12% 34%	1773
August	1st to 10th	Night	6% 3 2 5% 5% 4 6% 8% 8% 10% 42%	1611
	11th to 20th	Night	7% 4 2 7% 6% 4 6% 7% 7% 8% 43%	1752
	21st to end	Night	7% 4 2 5% 6% 4 6% 7% 7% 8% 44%	1980
September	1st to 10th	Night	8% 5% 2 5% 6% 4 6% 5% 7% 7% 46%	1800
	11th to 20th	Night	10% 4 1 4 4 3 3 4 4 5% 57%	1800
	21st to end	Night	10% 4 1 3 3 1 2 3 4 5% 62%	2025
October	1st to 10th	Night	13% 5% 1 4 3 2 3 3 4 5% 57%	2160
	11th to 20th	Night	8% 4 1 2 2 2 2 3 3 4 70%	2160
	21st to end	Night	8% 6% 1 3 3 2 3 2 3 5% 65%	2376
November	1st to 10th	Night	7% 6% 1 2 2 1 2 3 5% 5% 66%	2263
	11th to 20th	Night	5% 6% 1 2 2 1 2 3 3 5% 69%	2470
	21st to end	Night	8% 11% 3 4 2 1 2 2 3 5% 58%	2560
December	1st to 10th	Night	7% 9% 3 6% 3 2 3 2 3 5% 57%	2660
	11th to 20th	Night	6% 12% 3 6% 3 2 4 4 6% 7% 45%	3271
	21st to end	Night	6% 13% 5% 8% 5% 2 2 2 2 5% 51%	4873

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	33% 4 11% 29% 18% 6%	1635
	11th to 20th	Day	35% 3 9% 29% 19% 5%	1656
	21st to end	Day	36% 5% 9% 25% 19% 6%	1782
February	1st to 10th	Day	39% 4 12% 20% 18% 7%	1620
	11th to 20th	Day	42% 4 7% 22% 19% 6%	1700
	21st to end	Day	46% 3 5% 15% 24% 6%	1480
March	1st to 10th	Day	42% 4 8% 20% 19% 7%	1916
	11th to 20th	Day	39% 5% 7% 26% 20% 4	1980
	21st to end	Day	45% 4 8% 23% 17% 3	2225
April	1st to 10th	Day	35% 5% 9% 22% 21% 7%	2160
	11th to 20th	Day	38% 6% 8% 21% 22% 5%	2134
	21st to end	Day	38% 6% 8% 23% 22% 3	2160
May	1st to 10th	Day	36% 7% 7% 26% 23% 3	2168
	11th to 20th	Day	41% 6% 9% 23% 17% 3	2361
	21st to end	Day	31% 5% 8% 21% 27% 9%	2724
June	1st to 10th	Day	23% 8% 11% 25% 23% 10%	2520
	11th to 20th	Day	18% 6% 7% 19% 29% 22%	2520
	21st to end	Day	27% 6% 9% 20% 24% 15%	2520
July	1st to 10th	Day	34% 11% 12% 14% 18% 12%	2451
	11th to 20th	Day	34% 12% 18% 18% 12% 6%	2288
	21st to end	Day	45% 16% 21% 14% 4 1	2404
August	1st to 10th	Day	42% 12% 12% 13% 15% 6%	2313
	11th to 20th	Day	38% 12% 11% 17% 16% 7%	2149
	21st to end	Day	39% 10% 11% 20% 16% 3	2376
September	1st to 10th	Day	38% 7% 9% 18% 20% 7%	2160
	11th to 20th	Day	34% 8% 7% 17% 25% 10%	2160
	21st to end	Day	29% 6% 5% 23% 32% 5%	1928
October	1st to 10th	Day	35% 7% 6% 21% 22% 10%	1800
	11th to 20th	Day	25% 3 4 22% 36% 10%	1800
	21st to end	Day	27% 4 6% 27% 29% 7%	1980
November	1st to 10th	Day	22% 3 8% 27% 32% 7%	1793
	11th to 20th	Day	21% 5% 8% 29% 31% 7%	1710
	21st to end	Day	30% 2 6% 24% 26% 12%	1618
December	1st to 10th	Day	32% 4 13% 24% 19% 9%	1520
	11th to 20th	Day	38% 5% 8% 19% 23% 7%	1924
	21st to end	Day	32% 4 10% 19% 24% 12%	2794
January	1st to 10th	Night	31% 4 10% 25% 23% 7%	2547
	11th to 20th	Night	32% 3 8% 25% 25% 7%	2392
	21st to end	Night	33% 5% 6% 28% 20% 7%	2574
February	1st to 10th	Night	32% 4 12% 23% 21% 9%	2340
	11th to 20th	Night	38% 3 8% 22% 21% 7%	2155
	21st to end	Night	41% 5% 5% 17% 26% 7%	1776
March	1st to 10th	Night	35% 4 8% 20% 23% 10%	2039
	11th to 20th	Night	35% 6% 7% 26% 21% 6%	1980
	21st to end	Night	36% 4 8% 25% 23% 5%	2129
April	1st to 10th	Night	35% 4 7% 22% 23% 8%	1800
	11th to 20th	Night	37% 4 7% 20% 25% 7%	1777
	21st to end	Night	31% 5% 10% 25% 25% 4	1800
May	1st to 10th	Night	30% 6% 7% 26% 25% 6%	1789
	11th to 20th	Night	38% 7% 10% 20% 21% 4	1534
	21st to end	Night	28% 5% 9% 20% 27% 11%	1552
June	1st to 10th	Night	23% 6% 10% 21% 26% 13%	1440
	11th to 20th	Night	18% 4 6% 17% 30% 25%	1440
	21st to end	Night	24% 7% 10% 17% 25% 17%	1440
July	1st to 10th	Night	36% 9% 13% 12% 16% 13%	1400
	11th to 20th	Night	28% 11% 19% 20% 12% 10%	1543
	21st to end	Night	38% 17% 24% 14% 6% 1	1674
August	1st to 10th	Night	32% 14% 18% 14% 14% 8%	1602
	11th to 20th	Night	35% 10% 16% 17% 14% 7%	1752
	21st to end	Night	34% 11% 15% 19% 16% 4	1980
September	1st to 10th	Night	35% 8% 12% 19% 19% 7%	1800
	11th to 20th	Night	29% 5% 10% 19% 24% 13%	1800
	21st to end	Night	26% 5% 6% 23% 34% 7%	2025
October	1st to 10th	Night	31% 6% 7% 18% 26% 12%	2160
	11th to 20th	Night	21% 3 5% 21% 38% 12%	2160
	21st to end	Night	24% 5% 5% 26% 30% 10%	2376
November	1st to 10th	Night	22% 4 7% 27% 32% 8%	2263
	11th to 20th	Night	19% 4 7% 31% 31% 8%	2470
	21st to end	Night	32% 3 5% 22% 27% 11%	2560
December	1st to 10th	Night	32% 4 11% 25% 22% 7%	2660
	11th to 20th	Night	36% 6% 8% 19% 23% 8%	3272
	21st to end	Night	39% 3 7% 17% 20% 14%	4873

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	19% 19% 33% 20% 7% 1	270
	11th to 20th	Day	20% 21% 29% 24% 6%	252
	21st to end	Day	12% 24% 36% 19% 8% 1	264
February	1st to 10th	Day	13% 30% 31% 19% 6% 1	240
	11th to 20th	Day	23% 29% 26% 16% 5%	240
	21st to end	Day	28% 30% 26% 13% 3	198
March	1st to 10th	Day	25% 30% 22% 20% 3 1	356
	11th to 20th	Day	23% 29% 28% 14% 5% 1	420
	21st to end	Day	25% 39% 26% 7% 2	462
April	1st to 10th	Day	23% 36% 25% 10% 4 1	420
	11th to 20th	Day	27% 36% 23% 8% 4	412
	21st to end	Day	24% 34% 29% 10% 3	420
May	1st to 10th	Day	22% 32% 29% 13% 5%	423
	11th to 20th	Day	18% 23% 26% 21% 9% 2	505
	21st to end	Day	15% 22% 27% 23% 12% 2	679
June	1st to 10th	Day	6% 16% 27% 29% 18% 5%	630
	11th to 20th	Day	8% 21% 29% 22% 16% 4	630
	21st to end	Day	6% 17% 27% 26% 18% 6%	630
July	1st to 10th	Day	8% 10% 14% 32% 28% 7%	621
	11th to 20th	Day	7% 7% 20% 33% 23% 10%	461
	21st to end	Day	9% 4 14% 37% 30% 6%	487
August	1st to 10th	Day	11% 12% 19% 34% 18% 6%	447
	11th to 20th	Day	9% 12% 23% 33% 18% 5%	437
	21st to end	Day	9% 11% 20% 32% 23% 5%	495
September	1st to 10th	Day	11% 13% 25% 26% 18% 7%	450
	11th to 20th	Day	10% 16% 35% 24% 12% 4	450
	21st to end	Day	15% 18% 22% 28% 11% 7%	322
October	1st to 10th	Day	19% 22% 16% 24% 16% 4	270
	11th to 20th	Day	16% 22% 25% 18% 14% 5%	270
	21st to end	Day	20% 22% 23% 23% 10% 2	297
November	1st to 10th	Day	20% 27% 21% 20% 11% 1	270
	11th to 20th	Day	11% 24% 25% 26% 11% 2	270
	21st to end	Day	18% 20% 26% 24% 11% 1	270
December	1st to 10th	Day	20% 20% 29% 23% 9% 1	270
	11th to 20th	Day	16% 26% 27% 22% 8% 1	270
	21st to end	Day	22% 24% 32% 20% 4	297
January	1st to 10th	Night	10% 10% 23% 38% 16% 3	850
	11th to 20th	Night	12% 8% 24% 38% 15% 2	736
	21st to end	Night	12% 9% 27% 36% 13% 3	792
February	1st to 10th	Night	10% 13% 29% 36% 11% 1	720
	11th to 20th	Night	13% 15% 28% 33% 10% 1	704
	21st to end	Night	17% 13% 33% 31% 6%	592
March	1st to 10th	Night	16% 15% 27% 31% 10% 1	720
	11th to 20th	Night	11% 13% 25% 37% 14% 1	720
	21st to end	Night	16% 14% 32% 29% 8% 1	743
April	1st to 10th	Night	16% 17% 33% 27% 7% 1	540
	11th to 20th	Night	16% 14% 29% 32% 9% 1	533
	21st to end	Night	14% 13% 32% 30% 10% 1	540
May	1st to 10th	Night	13% 10% 30% 33% 13% 1	540
	11th to 20th	Night	13% 7% 24% 37% 16% 3	531
	21st to end	Night	12% 11% 27% 30% 18% 2	584
June	1st to 10th	Night	5% 6% 22% 45% 20% 2	540
	11th to 20th	Night	6% 9% 26% 39% 18% 2	540
	21st to end	Night	5% 4 20% 39% 30% 3	540
July	1st to 10th	Night	7% 3 12% 38% 36% 4	525
	11th to 20th	Night	4 2 6% 35% 43% 9%	522
	21st to end	Night	6% 3 5% 28% 48% 10%	591
August	1st to 10th	Night	8% 2 7% 24% 49% 10%	537
	11th to 20th	Night	7% 3 9% 34% 40% 7%	534
	21st to end	Night	6% 3 8% 34% 40% 8%	594
September	1st to 10th	Night	9% 3 10% 38% 34% 6%	540
	11th to 20th	Night	11% 3 12% 41% 27% 6%	540
	21st to end	Night	10% 7% 12% 33% 29% 8%	639
October	1st to 10th	Night	14% 7% 21% 32% 22% 4	720
	11th to 20th	Night	10% 5% 22% 38% 20% 5%	720
	21st to end	Night	12% 9% 20% 33% 20% 6%	792
November	1st to 10th	Night	11% 8% 19% 40% 19% 4	783
	11th to 20th	Night	8% 9% 24% 39% 17% 3	950
	21st to end	Night	14% 11% 22% 31% 18% 3	950
December	1st to 10th	Night	13% 11% 26% 34% 14% 1	950
	11th to 20th	Night	14% 10% 26% 33% 16% 1	950
	21st to end	Night	14% 13% 27% 35% 9% 2	1045

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