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 2024-10-24.

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 3 3 4 5% 69%	100768
	Night	4 4 1 4 3 3 3 3 4 6% 65%	98226
Transparency	Day	19% 2 5% 19% 27% 28%	100522
	Night	22% 2 6% 19% 25% 26%	98061
Seeing	Day	6% 9% 22% 33% 23% 7%	15496
	Night	6% 4 12% 35% 36% 8%	25070

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	6% 5% 2 6% 4 4 5% 4 6% 7% 51%	2649
	11th to 20th	Day	8% 8% 2 5% 4 5% 5% 4 6% 8% 44%	2860
	21st to end	Day	10% 9% 3 9% 4 5% 5% 5% 7% 8% 36%	3146
February	1st to 10th	Day	11% 7% 2 4 4 3 3 3 4 6% 54%	1805
	11th to 20th	Day	6% 6% 2 5% 5% 4 4 4 6% 8% 50%	1850
	21st to end	Day	8% 8% 2 7% 4 3 4 4 5% 6% 49%	1570
March	1st to 10th	Day	9% 8% 3 7% 5% 5% 5% 5% 7% 7% 38%	3188
	11th to 20th	Day	5% 4 1 3 3 4 4 3 4 7% 62%	3490
	21st to end	Day	5% 7% 2 8% 7% 5% 6% 5% 6% 7% 42%	4027
April	1st to 10th	Day	7% 6% 2 4 4 4 4 3 5% 7% 56%	2280
	11th to 20th	Day	5% 4 1 4 3 3 4 4 5% 8% 59%	2249
	21st to end	Day	3 3 1 3 3 3 3 3 5% 7% 66%	2280
May	1st to 10th	Day	2 2 1 3 2 2 2 2 4 5% 77%	3800
	11th to 20th	Day	1 1 1 1 2 2 2 2 4 5% 79%	3947
	21st to end	Day	1 1 2 2 2 2 2 3 5% 81%	4778
June	1st to 10th	Day	2 2 1 2 2 2 2 3 5% 7% 72%	2660
	11th to 20th	Day	1 1 1 1 1 2 2 3 88%	2660
	21st to end	Day	1 1 2 1 1 1 2 2 87%	2660
July	1st to 10th	Day	1 1 1 1 1 2 2 92%	4420
	11th to 20th	Day	1 1 1 1 1 2 2 2 2 4 83%	4207
	21st to end	Day	1 1 1 1 1 1 2 1 2 4 86%	4455
August	1st to 10th	Day	1 1 1 1 1 2 1 3 4 86%	3875
	11th to 20th	Day	1 1 1 2 93%	3724
	21st to end	Day	1 1 1 1 1 2 2 91%	4180
September	1st to 10th	Day	1 1 1 1 1 1 1 3 4 87%	2280
	11th to 20th	Day	1 1 2 1 2 2 2 2 4 84%	2258
	21st to end	Day	1 1 2 2 2 2 2 4 5% 81%	2090
October	1st to 10th	Day	2 1 1 3 2 2 3 3 4 6% 73%	1933
	11th to 20th	Day	1 2 1 3 3 3 3 3 4 5% 72%	1900
	21st to end	Day	2 2 1 3 3 2 2 3 4 6% 71%	2011
November	1st to 10th	Day	4 4 1 4 3 3 3 2 6% 7% 64%	1756
	11th to 20th	Day	3 3 1 5% 3 4 4 5% 4 6% 63%	1710
	21st to end	Day	5% 4 2 5% 3 4 4 4 6% 7% 57%	1710
December	1st to 10th	Day	5% 5% 2 6% 4 5% 5% 4 5% 8% 51%	1638
	11th to 20th	Day	11% 9% 3 8% 5% 5% 5% 5% 6% 6% 37%	1928
	21st to end	Day	10% 8% 2 7% 6% 5% 5% 5% 6% 8% 39%	2794
January	1st to 10th	Night	7% 8% 3 7% 4 4 4 4 5% 7% 49%	4284
	11th to 20th	Night	6% 8% 3 8% 5% 4 5% 4 6% 9% 44%	4110
	21st to end	Night	11% 11% 2 7% 4 4 4 4 5% 8% 39%	4521
February	1st to 10th	Night	7% 6% 3 5% 3 3 4 3 5% 5% 55%	2372
	11th to 20th	Night	5% 4 2 5% 4 4 5% 4 5% 7% 56%	2218
	21st to end	Night	6% 6% 2 5% 4 5% 4 3 4 6% 55%	1884
March	1st to 10th	Night	5% 10% 4 7% 5% 6% 6% 4 6% 8% 39%	3684
	11th to 20th	Night	3 4 1 4 4 3 4 3 6% 7% 61%	3490
	21st to end	Night	7% 7% 3 7% 5% 4 4 4 5% 7% 46%	3624
April	1st to 10th	Night	4 4 2 4 3 3 4 4 4 7% 60%	1900
	11th to 20th	Night	4 4 1 3 3 3 2 3 5% 5% 67%	1879
	21st to end	Night	3 3 1 3 3 2 4 4 4 7% 67%	1900
May	1st to 10th	Night	1 3 1 2 1 2 1 2 3 4 80%	3180
	11th to 20th	Night	1 1 1 2 3 3 3 4 7% 76%	2947
	21st to end	Night	1 1 1 1 2 2 2 5% 6% 79%	2794
June	1st to 10th	Night	1 1 2 2 1 2 2 5% 6% 77%	1520
	11th to 20th	Night	1 1 2 1 1 2 5% 87%	1520
	21st to end	Night	1 1 1 1 1 2 3 89%	1520
July	1st to 10th	Night	1 1 1 1 2 93%	2540
	11th to 20th	Night	1 1 1 1 1 1 2 4 87%	2754
	21st to end	Night	1 1 1 1 1 2 2 3 87%	3109
August	1st to 10th	Night	1 1 1 1 1 2 1 2 3 86%	3071
	11th to 20th	Night	1 1 1 1 1 1 3 92%	3126
	21st to end	Night	1 1 1 1 1 1 2 92%	3498
September	1st to 10th	Night	1 1 1 1 2 1 2 4 86%	1900
	11th to 20th	Night	1 1 2 1 2 2 2 2 4 84%	1920
	21st to end	Night	1 2 2 1 2 2 2 4 84%	2090
October	1st to 10th	Night	2 2 1 2 2 2 2 2 5% 5% 75%	2242
	11th to 20th	Night	2 3 1 3 3 2 3 2 4 6% 72%	2280
	21st to end	Night	2 3 1 3 2 2 3 2 4 5% 74%	2412
November	1st to 10th	Night	3 4 1 4 3 2 3 3 4 6% 67%	2321
	11th to 20th	Night	2 3 1 4 3 3 3 3 5% 6% 64%	2470
	21st to end	Night	4 4 2 5% 3 4 4 5% 7% 8% 55%	2470
December	1st to 10th	Night	6% 5% 2 4 4 4 5% 3 6% 9% 52%	2538
	11th to 20th	Night	10% 8% 3 9% 6% 5% 4 4 6% 6% 37%	3276
	21st to end	Night	9% 7% 3 8% 6% 5% 5% 4 6% 8% 38%	4862

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	32% 3 8% 35% 17% 5%	2649
	11th to 20th	Day	38% 2 10% 23% 17% 10%	2860
	21st to end	Day	46% 2 9% 21% 14% 9%	3146
February	1st to 10th	Day	33% 3 5% 19% 23% 17%	1805
	11th to 20th	Day	32% 3 6% 23% 25% 11%	1860
	21st to end	Day	36% 3 8% 20% 25% 6%	1570
March	1st to 10th	Day	44% 2 11% 20% 17% 6%	3188
	11th to 20th	Day	23% 3 11% 32% 20% 11%	3490
	21st to end	Day	41% 2 9% 28% 15% 4	4027
April	1st to 10th	Day	29% 3 10% 26% 22% 9%	2280
	11th to 20th	Day	24% 2 11% 27% 26% 10%	2252
	21st to end	Day	19% 3 8% 30% 31% 8%	2280
May	1st to 10th	Day	12% 2 7% 22% 36% 20%	3800
	11th to 20th	Day	10% 2 3 24% 43% 18%	3950
	21st to end	Day	9% 2 5% 32% 44% 8%	4778
June	1st to 10th	Day	14% 2 9% 21% 36% 18%	2660
	11th to 20th	Day	5% 1 4 15% 42% 32%	2660
	21st to end	Day	7% 1 2 8% 34% 49%	2660
July	1st to 10th	Day	3 1 1 4 17% 75%	4351
	11th to 20th	Day	9% 1 2 6% 18% 64%	4134
	21st to end	Day	6% 2 2 11% 28% 52%	4315
August	1st to 10th	Day	6% 1 1 7% 36% 48%	3860
	11th to 20th	Day	3 1 6% 30% 61%	3760
	21st to end	Day	4 1 1 10% 28% 57%	4179
September	1st to 10th	Day	5% 1 2 8% 31% 52%	2280
	11th to 20th	Day	8% 1 1 17% 43% 30%	2258
	21st to end	Day	9% 1 1 17% 40% 31%	2090
October	1st to 10th	Day	14% 2 4 21% 24% 35%	1933
	11th to 20th	Day	14% 4 5% 18% 31% 28%	1900
	21st to end	Day	16% 2 4 15% 33% 30%	2011
November	1st to 10th	Day	21% 2 7% 21% 29% 21%	1756
	11th to 20th	Day	22% 3 9% 22% 25% 20%	1710
	21st to end	Day	25% 4 7% 16% 24% 23%	1710
December	1st to 10th	Day	32% 4 7% 19% 20% 19%	1638
	11th to 20th	Day	48% 3 8% 16% 16% 9%	1928
	21st to end	Day	44% 2 8% 24% 17% 5%	2794
January	1st to 10th	Night	36% 2 9% 28% 21% 4	4284
	11th to 20th	Night	39% 2 9% 27% 12% 10%	4110
	21st to end	Night	45% 2 8% 22% 14% 9%	4521
February	1st to 10th	Night	31% 4 7% 18% 25% 16%	2372
	11th to 20th	Night	27% 3 7% 22% 28% 12%	2219
	21st to end	Night	31% 3 7% 24% 27% 7%	1884
March	1st to 10th	Night	43% 4 8% 24% 17% 5%	3684
	11th to 20th	Night	24% 3 11% 31% 23% 9%	3490
	21st to end	Night	39% 3 13% 23% 19% 4	3624
April	1st to 10th	Night	24% 5% 13% 28% 20% 11%	1900
	11th to 20th	Night	20% 2 11% 28% 29% 9%	1879
	21st to end	Night	17% 4 10% 28% 33% 9%	1900
May	1st to 10th	Night	10% 2 7% 28% 29% 24%	3180
	11th to 20th	Night	11% 3 3 22% 39% 22%	2948
	21st to end	Night	10% 2 4 27% 42% 14%	2794
June	1st to 10th	Night	10% 2 9% 20% 35% 22%	1520
	11th to 20th	Night	6% 1 4 14% 38% 37%	1520
	21st to end	Night	4 1 2 7% 31% 55%	1520
July	1st to 10th	Night	2 1 5% 14% 78%	2500
	11th to 20th	Night	5% 1 1 6% 15% 72%	2704
	21st to end	Night	5% 2 1 5% 30% 57%	3011
August	1st to 10th	Night	6% 1 1 8% 28% 55%	3062
	11th to 20th	Night	3 1 4 25% 67%	3156
	21st to end	Night	3 1 2 5% 27% 61%	3498
September	1st to 10th	Night	7% 1 2 6% 27% 58%	1900
	11th to 20th	Night	9% 2 2 12% 38% 38%	1920
	21st to end	Night	7% 2 1 15% 42% 34%	2090
October	1st to 10th	Night	12% 2 4 19% 26% 37%	2242
	11th to 20th	Night	16% 3 5% 16% 32% 29%	2280
	21st to end	Night	15% 2 2 18% 34% 29%	2412
November	1st to 10th	Night	19% 3 5% 22% 28% 23%	2321
	11th to 20th	Night	20% 3 9% 21% 25% 21%	2470
	21st to end	Night	26% 4 8% 17% 24% 20%	2470
December	1st to 10th	Night	29% 4 8% 19% 21% 19%	2538
	11th to 20th	Night	46% 4 9% 15% 17% 9%	3276
	21st to end	Night	45% 2 10% 20% 17% 6%	4862

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	20% 13% 34% 23% 9% 1	251
	11th to 20th	Day	14% 15% 28% 29% 12% 2	370
	21st to end	Day	13% 14% 33% 23% 15% 2	407
February	1st to 10th	Day	13% 15% 27% 29% 13% 3	415
	11th to 20th	Day	12% 17% 29% 28% 13% 2	455
	21st to end	Day	12% 19% 32% 25% 9% 2	382
March	1st to 10th	Day	18% 16% 32% 26% 9%	460
	11th to 20th	Day	13% 16% 29% 30% 12% 1	460
	21st to end	Day	13% 19% 32% 26% 9% 2	506
April	1st to 10th	Day	12% 12% 30% 26% 17% 2	460
	11th to 20th	Day	9% 13% 32% 27% 16% 3	452
	21st to end	Day	4 12% 32% 30% 17% 5%	460
May	1st to 10th	Day	8% 10% 30% 31% 16% 5%	463
	11th to 20th	Day	2 9% 28% 33% 22% 6%	488
	21st to end	Day	3 12% 22% 34% 21% 7%	529
June	1st to 10th	Day	3 5% 20% 36% 26% 9%	490
	11th to 20th	Day	1 6% 22% 39% 24% 9%	490
	21st to end	Day	1 3 15% 36% 29% 16%	490
July	1st to 10th	Day	1 10% 39% 35% 15%	486
	11th to 20th	Day	1 1 8% 35% 35% 20%	484
	21st to end	Day	1 7% 34% 38% 19%	531
August	1st to 10th	Day	2 1 14% 38% 30% 16%	487
	11th to 20th	Day	1 1 9% 38% 34% 17%	477
	21st to end	Day	1 1 8% 34% 41% 15%	539
September	1st to 10th	Day	1 3 11% 37% 35% 13%	490
	11th to 20th	Day	2 4 17% 40% 31% 6%	490
	21st to end	Day	5% 17% 39% 32% 7%	490
October	1st to 10th	Day	2 6% 23% 37% 29% 4	490
	11th to 20th	Day	2 8% 23% 36% 26% 5%	490
	21st to end	Day	3 7% 23% 35% 26% 6%	508
November	1st to 10th	Day	6% 8% 24% 32% 28% 3	352
	11th to 20th	Day	4 9% 27% 36% 21% 4	270
	21st to end	Day	10% 7% 24% 34% 20% 4	270
December	1st to 10th	Day	6% 14% 28% 41% 11% 1	236
	11th to 20th	Day	11% 14% 26% 27% 17% 5%	180
	21st to end	Day	16% 14% 31% 25% 9% 4	198
January	1st to 10th	Night	14% 6% 17% 35% 22% 6%	760
	11th to 20th	Night	10% 4 17% 42% 23% 5%	760
	21st to end	Night	13% 5% 17% 42% 20% 4	836
February	1st to 10th	Night	13% 8% 13% 38% 24% 5%	760
	11th to 20th	Night	8% 8% 17% 39% 24% 5%	744
	21st to end	Night	11% 8% 18% 43% 16% 4	628
March	1st to 10th	Night	10% 8% 18% 42% 20% 3	760
	11th to 20th	Night	8% 5% 15% 39% 27% 5%	760
	21st to end	Night	10% 9% 18% 36% 24% 3	836
April	1st to 10th	Night	7% 6% 16% 43% 25% 3	760
	11th to 20th	Night	7% 7% 19% 33% 30% 4	751
	21st to end	Night	4 6% 17% 37% 29% 7%	760
May	1st to 10th	Night	3 4 14% 40% 32% 7%	760
	11th to 20th	Night	2 4 13% 36% 39% 6%	635
	21st to end	Night	2 5% 11% 37% 38% 8%	430
June	1st to 10th	Night	2 3 7% 35% 48% 4	380
	11th to 20th	Night	8% 34% 50% 7%	380
	21st to end	Night	1 1 4 29% 57% 8%	380
July	1st to 10th	Night	1 20% 70% 9%	370
	11th to 20th	Night	1 12% 64% 22%	489
	21st to end	Night	1 1 12% 61% 24%	624
August	1st to 10th	Night	1 2 23% 58% 15%	699
	11th to 20th	Night	1 21% 63% 13%	752
	21st to end	Night	1 1 19% 63% 17%	836
September	1st to 10th	Night	1 1 4 24% 58% 13%	760
	11th to 20th	Night	1 1 5% 36% 46% 10%	760
	21st to end	Night	1 1 7% 33% 50% 9%	760
October	1st to 10th	Night	3 1 7% 40% 42% 7%	760
	11th to 20th	Night	4 2 9% 40% 38% 7%	760
	21st to end	Night	3 1 9% 40% 36% 9%	804
November	1st to 10th	Night	4 4 13% 38% 33% 8%	740
	11th to 20th	Night	4 3 13% 46% 27% 6%	760
	21st to end	Night	5% 5% 16% 43% 26% 6%	760
December	1st to 10th	Night	11% 5% 15% 41% 25% 4	760
	11th to 20th	Night	12% 4 17% 44% 20% 3	760
	21st to end	Night	12% 7% 19% 41% 18% 4	836

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