Navajo Flats
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Navajo Flats clear sky chart from 2005-11-06 to 2026-08-15.

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	3 3 1 3 2 2 3 3 4 5% 72%	151621
	Night	3 4 1 4 3 3 3 3 4 6% 68%	147835
Transparency	Day	16% 2 5% 18% 30% 28%	146662
	Night	20% 3 6% 18% 27% 26%	143772
Seeing	Day	6% 8% 22% 33% 23% 8%	17889
	Night	6% 4 12% 36% 35% 7%	27442

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 5% 2 5% 4 4 5% 4 6% 8% 53%	4944
	11th to 20th	Day	4 4 1 3 3 3 3 3 5% 6% 65%	5340
	21st to end	Day	6% 6% 2 6% 4 4 4 4 6% 8% 50%	5843
February	1st to 10th	Day	10% 7% 2 4 4 3 3 3 4 6% 53%	1996
	11th to 20th	Day	6% 6% 2 5% 5% 5% 4 4 6% 8% 48%	2050
	21st to end	Day	7% 7% 2 7% 4 3 4 4 5% 7% 49%	1730
March	1st to 10th	Day	10% 7% 3 6% 4 5% 5% 5% 6% 7% 43%	4695
	11th to 20th	Day	4 5% 2 5% 4 4 5% 4 5% 7% 56%	5110
	21st to end	Day	4 6% 2 6% 5% 5% 6% 5% 7% 9% 45%	5906
April	1st to 10th	Day	6% 5% 2 4 4 4 4 3 5% 7% 56%	2520
	11th to 20th	Day	4 4 2 4 3 3 4 4 5% 8% 59%	2489
	21st to end	Day	4 3 1 3 3 3 4 3 5% 7% 64%	2520
May	1st to 10th	Day	1 2 1 2 2 2 2 2 4 6% 78%	7058
	11th to 20th	Day	1 1 1 1 1 1 2 3 4 84%	7369
	21st to end	Day	1 1 2 2 2 2 2 3 6% 80%	8931
June	1st to 10th	Day	2 2 1 2 2 2 2 3 5% 7% 73%	2940
	11th to 20th	Day	1 1 1 1 1 2 3 89%	2940
	21st to end	Day	1 1 2 1 1 1 2 2 88%	2940
July	1st to 10th	Day	1 1 1 1 1 1 2 93%	8219
	11th to 20th	Day	1 1 1 1 1 2 2 1 2 4 84%	7825
	21st to end	Day	1 1 1 1 1 2 4 89%	8304
August	1st to 10th	Day	1 1 1 2 1 3 4 88%	5600
	11th to 20th	Day	1 1 1 2 95%	5413
	21st to end	Day	1 1 1 1 1 2 3 89%	5984
September	1st to 10th	Day	1 1 1 1 1 1 1 2 4 87%	2400
	11th to 20th	Day	1 1 2 1 2 2 2 2 4 84%	2377
	21st to end	Day	1 1 1 2 2 2 2 2 4 5% 79%	2200
October	1st to 10th	Day	1 1 2 2 2 2 3 3 5% 78%	3327
	11th to 20th	Day	1 1 1 3 2 2 3 2 3 4 78%	3261
	21st to end	Day	2 3 1 4 3 3 3 3 4 7% 67%	3558
November	1st to 10th	Day	3 4 1 4 3 2 3 3 5% 7% 65%	1944
	11th to 20th	Day	5% 3 2 4 3 4 4 4 4 6% 62%	1890
	21st to end	Day	6% 4 1 5% 3 4 4 4 6% 7% 57%	1890
December	1st to 10th	Day	3 4 2 5% 4 4 4 3 5% 8% 57%	2908
	11th to 20th	Day	7% 6% 3 6% 4 4 5% 5% 6% 8% 46%	3108
	21st to end	Day	8% 7% 2 7% 5% 4 5% 5% 7% 10% 40%	4092
January	1st to 10th	Night	7% 8% 3 6% 4 4 5% 3 5% 7% 49%	7946
	11th to 20th	Night	3 5% 1 4 3 3 3 3 4 7% 64%	7650
	21st to end	Night	7% 8% 2 6% 4 4 4 4 5% 8% 47%	8371
February	1st to 10th	Night	7% 6% 3 5% 3 4 4 3 5% 6% 55%	2621
	11th to 20th	Night	5% 4 2 5% 4 4 5% 4 5% 8% 54%	2458
	21st to end	Night	6% 6% 2 5% 4 5% 4 3 4 6% 56%	2076
March	1st to 10th	Night	5% 9% 3 7% 5% 5% 6% 4 7% 8% 41%	5417
	11th to 20th	Night	4 5% 2 5% 4 4 4 4 6% 6% 56%	5110
	21st to end	Night	6% 6% 3 7% 5% 4 5% 4 6% 7% 48%	5309
April	1st to 10th	Night	4 4 1 4 4 3 3 4 5% 7% 60%	2100
	11th to 20th	Night	3 4 2 3 3 3 3 3 5% 5% 66%	2079
	21st to end	Night	2 3 1 3 3 2 4 4 5% 7% 66%	2100
May	1st to 10th	Night	1 2 1 2 1 2 2 2 3 5% 79%	5919
	11th to 20th	Night	1 1 1 2 2 2 3 6% 82%	5519
	21st to end	Night	1 1 1 1 2 2 3 4 84%	5241
June	1st to 10th	Night	1 1 2 2 1 2 2 5% 6% 78%	1680
	11th to 20th	Night	1 1 2 1 1 2 4 87%	1680
	21st to end	Night	1 1 1 1 1 2 3 90%	1680
July	1st to 10th	Night	1 1 1 1 2 93%	4740
	11th to 20th	Night	1 1 1 1 1 1 1 2 3 86%	5150
	21st to end	Night	1 1 1 1 1 2 4 88%	5806
August	1st to 10th	Night	1 1 1 1 1 2 3 88%	4446
	11th to 20th	Night	1 1 1 1 1 2 93%	4546
	21st to end	Night	1 1 1 1 1 2 3 90%	5015
September	1st to 10th	Night	1 1 1 1 2 1 2 4 87%	2000
	11th to 20th	Night	1 2 2 1 2 2 2 2 3 83%	2021
	21st to end	Night	1 1 1 2 2 1 2 2 3 4 83%	2200
October	1st to 10th	Night	1 1 1 1 1 2 2 4 4 82%	3856
	11th to 20th	Night	1 2 1 2 2 2 3 2 3 4 78%	3897
	21st to end	Night	1 3 1 4 2 3 2 2 4 5% 73%	4253
November	1st to 10th	Night	2 3 1 4 2 2 3 3 4 6% 68%	2573
	11th to 20th	Night	3 3 2 5% 3 3 4 3 5% 6% 63%	2730
	21st to end	Night	4 5% 2 5% 4 4 4 4 6% 8% 54%	2730
December	1st to 10th	Night	4 4 1 3 3 4 5% 3 5% 8% 59%	4494
	11th to 20th	Night	7% 6% 3 7% 5% 5% 5% 5% 7% 8% 43%	5316
	21st to end	Night	7% 7% 3 9% 6% 6% 6% 5% 7% 10% 34%	7106

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% 4 10% 31% 18% 10%	4945
	11th to 20th	Day	22% 1 6% 13% 23% 36%	5340
	21st to end	Day	32% 3 6% 17% 27% 16%	5843
February	1st to 10th	Day	33% 3 5% 19% 23% 17%	1996
	11th to 20th	Day	32% 4 8% 22% 24% 10%	2060
	21st to end	Day	35% 3 8% 21% 26% 7%	1730
March	1st to 10th	Day	39% 4 11% 18% 24% 6%	4695
	11th to 20th	Day	26% 5% 10% 33% 17% 9%	5110
	21st to end	Day	34% 5% 10% 30% 18% 4	5906
April	1st to 10th	Day	28% 4 10% 25% 25% 9%	2520
	11th to 20th	Day	24% 3 10% 28% 26% 9%	2492
	21st to end	Day	20% 3 8% 30% 30% 8%	2520
May	1st to 10th	Day	10% 3 6% 24% 39% 17%	7058
	11th to 20th	Day	7% 1 3 23% 47% 18%	7372
	21st to end	Day	9% 3 4 27% 47% 11%	8932
June	1st to 10th	Day	13% 2 8% 21% 37% 18%	2940
	11th to 20th	Day	5% 1 4 14% 41% 36%	2940
	21st to end	Day	6% 1 1 8% 35% 49%	2940
July	1st to 10th	Day	3 1 1 3 23% 70%	8151
	11th to 20th	Day	8% 1 3 8% 22% 58%	7752
	21st to end	Day	4 1 1 14% 31% 49%	8119
August	1st to 10th	Day	6% 1 1 8% 36% 48%	4106
	11th to 20th	Day	3 1 6% 30% 60%	3929
	21st to end	Day	4 1 1 10% 28% 56%	4311
September	1st to 10th	Day	5% 1 2 9% 33% 50%	2400
	11th to 20th	Day	8% 1 1 17% 43% 29%	2377
	21st to end	Day	10% 2 2 17% 40% 30%	2200
October	1st to 10th	Day	10% 2 3 14% 22% 49%	3327
	11th to 20th	Day	12% 3 4 20% 39% 23%	3261
	21st to end	Day	17% 3 3 12% 36% 28%	3558
November	1st to 10th	Day	20% 2 7% 22% 29% 21%	1944
	11th to 20th	Day	24% 3 9% 22% 25% 18%	1890
	21st to end	Day	26% 4 7% 17% 24% 22%	1890
December	1st to 10th	Day	25% 3 5% 18% 27% 22%	2908
	11th to 20th	Day	34% 5% 10% 18% 21% 11%	3108
	21st to end	Day	38% 4 12% 28% 14% 4	4092
January	1st to 10th	Night	34% 4 12% 24% 19% 7%	7946
	11th to 20th	Night	22% 1 5% 15% 25% 31%	7650
	21st to end	Night	35% 3 6% 19% 24% 13%	8371
February	1st to 10th	Night	30% 4 7% 18% 25% 16%	2621
	11th to 20th	Night	28% 4 8% 23% 27% 11%	2459
	21st to end	Night	30% 4 7% 25% 27% 8%	2076
March	1st to 10th	Night	38% 5% 8% 20% 24% 5%	5417
	11th to 20th	Night	27% 4 12% 30% 19% 8%	5110
	21st to end	Night	34% 4 14% 26% 19% 4	5309
April	1st to 10th	Night	23% 5% 13% 27% 21% 11%	2100
	11th to 20th	Night	21% 3 10% 28% 29% 9%	2079
	21st to end	Night	17% 4 10% 28% 32% 8%	2100
May	1st to 10th	Night	8% 3 10% 28% 37% 15%	5917
	11th to 20th	Night	7% 3 3 22% 46% 20%	5520
	21st to end	Night	7% 2 3 24% 48% 16%	5242
June	1st to 10th	Night	9% 2 9% 20% 38% 22%	1680
	11th to 20th	Night	5% 1 4 13% 37% 40%	1680
	21st to end	Night	4 1 2 6% 31% 55%	1680
July	1st to 10th	Night	2 1 3 17% 77%	4700
	11th to 20th	Night	6% 1 2 7% 17% 66%	5100
	21st to end	Night	4 1 1 11% 31% 51%	5679
August	1st to 10th	Night	6% 1 1 8% 28% 55%	3256
	11th to 20th	Night	3 1 4 26% 66%	3296
	21st to end	Night	3 1 2 5% 28% 61%	3608
September	1st to 10th	Night	6% 1 2 6% 28% 56%	2000
	11th to 20th	Night	9% 2 2 12% 38% 37%	2021
	21st to end	Night	8% 2 1 15% 41% 33%	2200
October	1st to 10th	Night	7% 2 3 12% 24% 52%	3856
	11th to 20th	Night	11% 3 3 19% 37% 26%	3897
	21st to end	Night	15% 2 2 14% 39% 27%	4253
November	1st to 10th	Night	18% 3 6% 23% 29% 23%	2573
	11th to 20th	Night	22% 3 9% 21% 25% 20%	2730
	21st to end	Night	27% 4 8% 18% 25% 19%	2730
December	1st to 10th	Night	23% 4 5% 17% 33% 19%	4494
	11th to 20th	Night	36% 5% 13% 18% 17% 12%	5316
	21st to end	Night	44% 4 13% 22% 12% 4	7106

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	18% 14% 33% 24% 10% 1	299
	11th to 20th	Day	12% 14% 27% 30% 13% 3	430
	21st to end	Day	12% 12% 33% 25% 15% 3	473
February	1st to 10th	Day	14% 15% 28% 29% 12% 3	486
	11th to 20th	Day	13% 17% 31% 27% 12% 1	535
	21st to end	Day	11% 16% 33% 28% 10% 2	446
March	1st to 10th	Day	17% 16% 33% 26% 9%	540
	11th to 20th	Day	14% 14% 27% 30% 14% 1	540
	21st to end	Day	12% 17% 31% 27% 11% 3	594
April	1st to 10th	Day	11% 11% 30% 28% 18% 2	540
	11th to 20th	Day	8% 13% 32% 27% 17% 4	532
	21st to end	Day	5% 12% 33% 29% 16% 5%	540
May	1st to 10th	Day	7% 10% 29% 30% 18% 6%	543
	11th to 20th	Day	2 9% 28% 33% 21% 6%	568
	21st to end	Day	3 11% 21% 35% 22% 8%	617
June	1st to 10th	Day	2 5% 20% 36% 26% 11%	570
	11th to 20th	Day	1 5% 21% 39% 24% 11%	570
	21st to end	Day	1 3 16% 35% 28% 17%	570
July	1st to 10th	Day	1 10% 38% 36% 14%	566
	11th to 20th	Day	1 1 7% 34% 36% 21%	564
	21st to end	Day	1 6% 34% 37% 21%	619
August	1st to 10th	Day	1 1 12% 36% 31% 19%	567
	11th to 20th	Day	1 1 9% 38% 34% 18%	534
	21st to end	Day	1 1 8% 34% 41% 16%	583
September	1st to 10th	Day	1 3 12% 37% 34% 14%	530
	11th to 20th	Day	3 4 17% 39% 31% 7%	530
	21st to end	Day	1 5% 18% 39% 32% 6%	530
October	1st to 10th	Day	2 6% 22% 36% 30% 5%	530
	11th to 20th	Day	2 9% 23% 35% 26% 5%	530
	21st to end	Day	3 7% 23% 35% 26% 5%	583
November	1st to 10th	Day	5% 8% 23% 31% 29% 4	420
	11th to 20th	Day	8% 9% 28% 34% 19% 3	330
	21st to end	Day	11% 7% 24% 34% 21% 3	330
December	1st to 10th	Day	5% 11% 26% 39% 15% 4	288
	11th to 20th	Day	10% 13% 25% 26% 21% 5%	220
	21st to end	Day	15% 15% 32% 24% 10% 3	242
January	1st to 10th	Night	14% 6% 18% 37% 20% 5%	840
	11th to 20th	Night	9% 3 17% 44% 23% 4	840
	21st to end	Night	12% 4 17% 42% 21% 4	924
February	1st to 10th	Night	12% 7% 14% 40% 22% 4	840
	11th to 20th	Night	8% 8% 18% 39% 22% 5%	824
	21st to end	Night	10% 7% 18% 46% 15% 3	692
March	1st to 10th	Night	9% 7% 18% 43% 19% 3	840
	11th to 20th	Night	8% 5% 15% 40% 27% 5%	840
	21st to end	Night	9% 8% 18% 38% 25% 3	924
April	1st to 10th	Night	7% 6% 16% 43% 25% 3	840
	11th to 20th	Night	7% 6% 18% 34% 30% 4	831
	21st to end	Night	4 6% 18% 37% 28% 7%	840
May	1st to 10th	Night	3 4 14% 39% 34% 6%	840
	11th to 20th	Night	2 4 14% 37% 38% 5%	703
	21st to end	Night	2 4 10% 38% 38% 8%	476
June	1st to 10th	Night	2 3 7% 36% 48% 5%	420
	11th to 20th	Night	8% 35% 50% 7%	420
	21st to end	Night	5% 30% 55% 9%	420
July	1st to 10th	Night	1 20% 70% 8%	410
	11th to 20th	Night	1 13% 62% 23%	543
	21st to end	Night	1 1 13% 61% 23%	690
August	1st to 10th	Night	1 2 23% 58% 16%	773
	11th to 20th	Night	1 22% 63% 13%	808
	21st to end	Night	1 1 20% 62% 16%	880
September	1st to 10th	Night	1 1 3 25% 57% 13%	800
	11th to 20th	Night	2 1 5% 36% 46% 10%	800
	21st to end	Night	1 1 8% 33% 49% 9%	800
October	1st to 10th	Night	3 1 7% 40% 42% 6%	800
	11th to 20th	Night	4 2 9% 41% 37% 7%	800
	21st to end	Night	4 2 9% 42% 35% 9%	880
November	1st to 10th	Night	4 4 13% 38% 34% 7%	820
	11th to 20th	Night	5% 3 14% 47% 25% 5%	840
	21st to end	Night	6% 5% 16% 45% 24% 5%	840
December	1st to 10th	Night	10% 4 15% 42% 26% 4	840
	11th to 20th	Night	11% 4 16% 45% 21% 3	840
	21st to end	Night	13% 6% 20% 41% 16% 3	924

Page generated at 2026-08-12 00:37:18. Version ac07

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