Coyote Howl Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coyote Howl Observatory clear sky chart from 2005-11-06 to 2026-05-17.

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	14% 10% 4 8% 5% 4 4 4 6% 7% 35%	131458
	Night	14% 10% 4 8% 5% 4 4 3 5% 6% 36%	131553
Transparency	Day	47% 5% 11% 22% 13% 1	135057
	Night	47% 5% 10% 22% 14% 2	136027
Seeing	Day	17% 9% 26% 24% 17% 7%	17578
	Night	19% 8% 28% 30% 14% 2	27471

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	16% 15% 7% 13% 6% 4 4 3 5% 6% 22%	4691
	11th to 20th	Day	10% 14% 7% 15% 9% 8% 6% 4 3 4 20%	4710
	21st to end	Day	17% 16% 7% 13% 6% 4 6% 3 4 5% 19%	5476
February	1st to 10th	Day	18% 14% 6% 10% 6% 5% 3 3 4 5% 26%	2070
	11th to 20th	Day	15% 13% 4 11% 7% 5% 4 3 4 5% 28%	2048
	21st to end	Day	16% 14% 5% 10% 4 3 3 4 4 6% 31%	1730
March	1st to 10th	Day	20% 15% 7% 8% 4 3 3 2 3 4 30%	4580
	11th to 20th	Day	12% 10% 3 6% 4 3 4 4 5% 7% 42%	4963
	21st to end	Day	17% 12% 4 8% 5% 4 4 3 5% 6% 31%	5765
April	1st to 10th	Day	16% 11% 3 8% 5% 4 4 4 5% 6% 33%	2520
	11th to 20th	Day	16% 10% 3 6% 4 4 4 3 6% 7% 36%	2494
	21st to end	Day	19% 8% 3 7% 5% 5% 5% 3 5% 6% 36%	2725
May	1st to 10th	Day	20% 10% 3 7% 5% 5% 5% 4 6% 7% 28%	5992
	11th to 20th	Day	18% 8% 2 7% 5% 4 4 3 6% 6% 36%	5939
	21st to end	Day	14% 7% 3 7% 5% 5% 5% 4 7% 9% 34%	6513
June	1st to 10th	Day	11% 6% 2 6% 5% 5% 5% 4 6% 8% 42%	2800
	11th to 20th	Day	10% 6% 2 5% 5% 5% 4 4 7% 8% 43%	2800
	21st to end	Day	9% 5% 2 7% 5% 5% 4 5% 7% 9% 43%	2800
July	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 4 7% 9% 41%	6360
	11th to 20th	Day	9% 6% 2 7% 5% 5% 5% 5% 8% 11% 38%	6360
	21st to end	Day	11% 7% 3 7% 5% 5% 6% 5% 6% 9% 36%	6657
August	1st to 10th	Day	8% 5% 2 6% 4 4 4 4 6% 11% 46%	4234
	11th to 20th	Day	9% 5% 3 6% 4 5% 4 4 8% 11% 40%	4051
	21st to end	Day	7% 5% 2 5% 4 4 4 4 6% 9% 51%	4312
September	1st to 10th	Day	11% 5% 2 5% 4 4 4 4 5% 7% 48%	2350
	11th to 20th	Day	10% 5% 1 4 4 4 5% 4 6% 8% 49%	2200
	21st to end	Day	14% 6% 2 6% 4 3 4 3 5% 6% 47%	2200
October	1st to 10th	Day	12% 5% 2 6% 4 3 4 3 5% 7% 49%	2200
	11th to 20th	Day	14% 6% 2 5% 4 4 5% 4 5% 7% 44%	2046
	21st to end	Day	19% 10% 3 7% 3 3 5% 3 5% 6% 35%	1980
November	1st to 10th	Day	9% 7% 2 5% 5% 4 4 3 5% 7% 49%	1852
	11th to 20th	Day	16% 12% 4 8% 4 4 4 3 6% 7% 33%	1890
	21st to end	Day	20% 13% 4 8% 4 3 3 3 4 6% 33%	1890
December	1st to 10th	Day	15% 13% 4 8% 4 3 3 2 4 5% 39%	3020
	11th to 20th	Day	16% 16% 6% 11% 5% 4 4 4 5% 5% 25%	3170
	21st to end	Day	25% 18% 8% 10% 6% 5% 3 3 4 5% 13%	4070
January	1st to 10th	Night	15% 15% 7% 13% 6% 4 4 3 5% 5% 22%	8232
	11th to 20th	Night	10% 17% 7% 16% 7% 6% 5% 4 4 4 20%	8280
	21st to end	Night	18% 13% 5% 8% 5% 5% 4 4 5% 6% 27%	8718
February	1st to 10th	Night	18% 13% 5% 10% 6% 4 3 3 5% 5% 28%	2546
	11th to 20th	Night	16% 12% 5% 10% 4 3 4 3 4 6% 32%	2458
	21st to end	Night	18% 12% 5% 10% 4 4 3 3 4 6% 31%	2076
March	1st to 10th	Night	19% 12% 3 6% 4 3 3 3 4 5% 38%	5493
	11th to 20th	Night	13% 7% 3 6% 4 4 4 3 5% 7% 44%	5216
	21st to end	Night	18% 9% 4 8% 4 4 4 4 5% 6% 34%	5450
April	1st to 10th	Night	16% 10% 3 6% 4 4 5% 4 6% 7% 37%	2100
	11th to 20th	Night	16% 8% 3 6% 5% 4 4 3 5% 7% 40%	2075
	21st to end	Night	17% 8% 3 6% 5% 4 5% 4 7% 7% 36%	1895
May	1st to 10th	Night	20% 10% 3 8% 5% 4 4 3 5% 7% 29%	4123
	11th to 20th	Night	16% 8% 2 7% 5% 3 4 3 5% 9% 38%	4086
	21st to end	Night	13% 8% 3 7% 4 4 5% 4 6% 8% 38%	4341
June	1st to 10th	Night	9% 7% 2 6% 5% 4 3 3 6% 7% 48%	1600
	11th to 20th	Night	9% 7% 2 6% 5% 4 4 3 5% 9% 46%	1600
	21st to end	Night	7% 3 1 6% 5% 4 5% 5% 8% 10% 45%	1600
July	1st to 10th	Night	8% 5% 2 6% 4 4 5% 4 6% 10% 47%	3618
	11th to 20th	Night	9% 5% 2 5% 4 4 5% 4 7% 9% 46%	3617
	21st to end	Night	10% 7% 3 7% 5% 4 6% 4 6% 10% 39%	4200
August	1st to 10th	Night	9% 6% 2 5% 3 4 4 3 5% 9% 49%	2915
	11th to 20th	Night	8% 6% 2 6% 4 5% 4 3 7% 8% 46%	2995
	21st to end	Night	5% 4 2 5% 4 5% 4 3 6% 8% 54%	3586
September	1st to 10th	Night	11% 5% 2 5% 3 3 4 4 5% 7% 50%	2030
	11th to 20th	Night	8% 4 1 5% 4 3 4 4 5% 7% 56%	2200
	21st to end	Night	12% 6% 2 5% 3 4 4 3 4 6% 50%	2200
October	1st to 10th	Night	9% 5% 1 5% 3 4 4 3 5% 6% 56%	2200
	11th to 20th	Night	16% 7% 2 5% 3 4 3 2 4 6% 46%	2350
	21st to end	Night	17% 8% 3 7% 5% 4 4 3 5% 6% 40%	2860
November	1st to 10th	Night	13% 8% 2 5% 3 3 3 3 4 5% 49%	2666
	11th to 20th	Night	14% 10% 3 7% 4 3 4 3 5% 7% 40%	2730
	21st to end	Night	19% 14% 4 8% 5% 4 4 3 3 5% 31%	2730
December	1st to 10th	Night	14% 11% 4 9% 5% 4 4 3 4 6% 38%	4380
	11th to 20th	Night	18% 15% 7% 10% 5% 5% 4 3 4 4 25%	5237
	21st to end	Night	26% 20% 6% 10% 5% 4 4 3 4 4 15%	7150

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	64% 4 10% 17% 5%	4692
	11th to 20th	Day	69% 3 8% 10% 8% 2	4710
	21st to end	Day	69% 3 7% 14% 6% 2	5476
February	1st to 10th	Day	62% 3 9% 15% 9% 1	2070
	11th to 20th	Day	58% 4 9% 20% 9% 1	2058
	21st to end	Day	56% 4 9% 22% 8% 2	1730
March	1st to 10th	Day	58% 3 7% 19% 11% 1	4580
	11th to 20th	Day	41% 4 10% 32% 11% 1	4963
	21st to end	Day	53% 5% 13% 18% 8% 2	5767
April	1st to 10th	Day	51% 6% 11% 20% 12% 1	2520
	11th to 20th	Day	47% 5% 12% 24% 10% 3	2494
	21st to end	Day	49% 5% 11% 23% 10% 2	2725
May	1st to 10th	Day	53% 7% 11% 18% 10%	6027
	11th to 20th	Day	48% 6% 11% 23% 11% 1	5943
	21st to end	Day	42% 7% 13% 24% 12% 1	6527
June	1st to 10th	Day	39% 7% 12% 24% 16% 3	2800
	11th to 20th	Day	36% 8% 11% 25% 19% 2	2800
	21st to end	Day	37% 8% 16% 20% 16% 4	2800
July	1st to 10th	Day	38% 6% 11% 26% 19% 1	6291
	11th to 20th	Day	36% 8% 17% 24% 14% 1	6285
	21st to end	Day	42% 8% 14% 20% 13% 2	6467
August	1st to 10th	Day	32% 7% 16% 30% 14% 1	4221
	11th to 20th	Day	34% 8% 13% 31% 14%	4090
	21st to end	Day	29% 7% 13% 30% 17% 4	4311
September	1st to 10th	Day	35% 6% 11% 25% 19% 4	2350
	11th to 20th	Day	32% 6% 11% 25% 23% 3	2200
	21st to end	Day	37% 5% 10% 23% 24% 2	2200
October	1st to 10th	Day	24% 4 9% 31% 31% 2	3590
	11th to 20th	Day	33% 4 10% 27% 24% 2	3301
	21st to end	Day	41% 4 9% 24% 20% 1	3180
November	1st to 10th	Day	35% 4 12% 28% 17% 3	1852
	11th to 20th	Day	50% 5% 9% 20% 13% 3	1890
	21st to end	Day	55% 4 10% 22% 9% 1	1890
December	1st to 10th	Day	50% 3 10% 26% 11%	3020
	11th to 20th	Day	62% 4 10% 18% 6%	3167
	21st to end	Day	73% 5% 8% 10% 5%	4070
January	1st to 10th	Night	64% 4 9% 15% 7%	8233
	11th to 20th	Night	68% 4 7% 11% 9% 1	8280
	21st to end	Night	58% 4 10% 21% 7% 1	8718
February	1st to 10th	Night	59% 4 10% 17% 8% 1	2546
	11th to 20th	Night	54% 4 10% 20% 11% 1	2459
	21st to end	Night	55% 5% 11% 17% 10% 2	2076
March	1st to 10th	Night	50% 3 7% 26% 11% 2	5493
	11th to 20th	Night	39% 5% 11% 27% 16% 2	5216
	21st to end	Night	50% 5% 9% 26% 9% 1	5450
April	1st to 10th	Night	46% 6% 11% 23% 13% 2	2100
	11th to 20th	Night	44% 5% 11% 20% 16% 4	2075
	21st to end	Night	46% 6% 10% 23% 13% 4	1895
May	1st to 10th	Night	55% 7% 8% 18% 10% 2	4150
	11th to 20th	Night	43% 6% 12% 27% 11% 1	4087
	21st to end	Night	41% 7% 15% 23% 12% 2	4349
June	1st to 10th	Night	35% 5% 10% 26% 21% 4	1600
	11th to 20th	Night	35% 5% 11% 25% 21% 3	1600
	21st to end	Night	30% 9% 15% 25% 17% 4	1600
July	1st to 10th	Night	33% 7% 12% 27% 18% 5%	3580
	11th to 20th	Night	31% 8% 16% 28% 16% 1	3572
	21st to end	Night	39% 7% 13% 24% 14% 3	4077
August	1st to 10th	Night	32% 6% 15% 32% 13% 1	2904
	11th to 20th	Night	35% 6% 12% 28% 18% 1	3022
	21st to end	Night	27% 6% 13% 29% 23% 3	3586
September	1st to 10th	Night	32% 6% 11% 23% 22% 6%	2030
	11th to 20th	Night	28% 5% 9% 28% 27% 3	2200
	21st to end	Night	35% 6% 9% 23% 23% 3	2200
October	1st to 10th	Night	21% 4 7% 27% 39% 2	3590
	11th to 20th	Night	29% 3 9% 24% 33% 2	3834
	21st to end	Night	35% 3 7% 26% 24% 4	4610
November	1st to 10th	Night	38% 4 9% 25% 22% 3	2666
	11th to 20th	Night	45% 4 8% 24% 16% 3	2730
	21st to end	Night	57% 4 9% 20% 10%	2730
December	1st to 10th	Night	49% 4 11% 25% 11%	4380
	11th to 20th	Night	62% 4 10% 16% 8% 1	5239
	21st to end	Night	73% 4 8% 11% 4	7150

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	24% 17% 34% 20% 5% 1	330
	11th to 20th	Day	22% 22% 37% 14% 4 1	330
	21st to end	Day	29% 15% 30% 22% 5%	363
February	1st to 10th	Day	27% 13% 36% 20% 5%	330
	11th to 20th	Day	23% 18% 36% 18% 5%	330
	21st to end	Day	22% 15% 41% 20% 2	273
March	1st to 10th	Day	23% 19% 37% 19% 2	330
	11th to 20th	Day	24% 16% 34% 17% 7% 1	478
	21st to end	Day	28% 14% 34% 16% 7% 1	594
April	1st to 10th	Day	20% 14% 33% 22% 8% 3	540
	11th to 20th	Day	20% 16% 31% 20% 11% 3	532
	21st to end	Day	23% 11% 34% 22% 8% 2	540
May	1st to 10th	Day	24% 10% 31% 25% 7% 3	543
	11th to 20th	Day	21% 8% 27% 23% 15% 7%	551
	21st to end	Day	14% 4 25% 27% 18% 11%	601
June	1st to 10th	Day	12% 5% 25% 29% 22% 6%	730
	11th to 20th	Day	12% 4 21% 33% 23% 7%	730
	21st to end	Day	11% 5% 23% 30% 22% 9%	730
July	1st to 10th	Day	12% 2 14% 25% 28% 19%	721
	11th to 20th	Day	8% 4 17% 31% 26% 14%	718
	21st to end	Day	10% 3 11% 30% 31% 15%	679
August	1st to 10th	Day	10% 3 12% 26% 30% 20%	526
	11th to 20th	Day	13% 3 14% 26% 29% 14%	519
	21st to end	Day	9% 3 10% 30% 32% 16%	583
September	1st to 10th	Day	10% 6% 15% 24% 32% 13%	530
	11th to 20th	Day	10% 2 12% 28% 29% 21%	530
	21st to end	Day	19% 6% 18% 23% 23% 10%	530
October	1st to 10th	Day	12% 5% 19% 33% 22% 8%	530
	11th to 20th	Day	13% 11% 32% 26% 15% 3	481
	21st to end	Day	28% 11% 35% 21% 5%	363
November	1st to 10th	Day	14% 15% 32% 23% 13% 3	330
	11th to 20th	Day	23% 15% 31% 20% 9% 2	330
	21st to end	Day	27% 10% 37% 21% 4 1	330
December	1st to 10th	Day	20% 18% 40% 16% 5% 1	330
	11th to 20th	Day	22% 16% 37% 20% 5% 1	330
	21st to end	Day	30% 14% 34% 18% 4	363
January	1st to 10th	Night	24% 14% 34% 24% 4	1050
	11th to 20th	Night	26% 13% 38% 20% 4	1050
	21st to end	Night	24% 12% 37% 23% 4	1034
February	1st to 10th	Night	25% 9% 37% 26% 3	840
	11th to 20th	Night	21% 12% 38% 27% 2	823
	21st to end	Night	24% 10% 41% 23% 2	692
March	1st to 10th	Night	24% 13% 33% 24% 6%	840
	11th to 20th	Night	21% 13% 36% 25% 6% 1	840
	21st to end	Night	24% 10% 33% 27% 5% 1	863
April	1st to 10th	Night	19% 10% 38% 25% 7%	630
	11th to 20th	Night	19% 11% 33% 28% 9% 1	623
	21st to end	Night	21% 6% 39% 24% 8% 1	630
May	1st to 10th	Night	22% 7% 34% 27% 10%	630
	11th to 20th	Night	19% 5% 24% 33% 17% 2	609
	21st to end	Night	10% 5% 22% 38% 23% 2	650
June	1st to 10th	Night	11% 3 23% 45% 17% 1	600
	11th to 20th	Night	12% 3 18% 43% 21% 2	600
	21st to end	Night	7% 2 22% 39% 28% 2	600
July	1st to 10th	Night	10% 2 10% 35% 36% 7%	585
	11th to 20th	Night	9% 2 13% 40% 32% 5%	582
	21st to end	Night	8% 2 10% 41% 36% 2	657
August	1st to 10th	Night	9% 3 10% 38% 36% 5%	597
	11th to 20th	Night	7% 1 11% 42% 34% 5%	594
	21st to end	Night	7% 1 13% 38% 38% 4	660
September	1st to 10th	Night	13% 3 11% 35% 33% 5%	630
	11th to 20th	Night	9% 2 13% 36% 34% 6%	800
	21st to end	Night	15% 5% 19% 34% 24% 3	800
October	1st to 10th	Night	12% 5% 22% 37% 21% 4	800
	11th to 20th	Night	20% 8% 28% 29% 14% 1	800
	21st to end	Night	20% 9% 37% 26% 8%	880
November	1st to 10th	Night	17% 8% 34% 27% 13%	820
	11th to 20th	Night	18% 14% 32% 28% 7% 1	840
	21st to end	Night	26% 11% 30% 26% 8%	840
December	1st to 10th	Night	23% 10% 37% 24% 5%	840
	11th to 20th	Night	26% 8% 36% 25% 5%	987
	21st to end	Night	31% 12% 32% 21% 3	1155

Page generated at 2026-05-14 02:58:58. Version ac07

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