Echo Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Echo Park clear sky chart from 2005-11-06 to 2026-07-31.

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 5% 2 5% 4 4 5% 4 6% 8% 53%	147269
	Night	3 5% 2 6% 4 4 5% 4 6% 8% 52%	143320
Transparency	Day	24% 7% 13% 23% 21% 12%	142094
	Night	27% 7% 13% 25% 19% 8%	139504
Seeing	Day	7% 13% 29% 31% 17% 4	17845
	Night	6% 5% 23% 43% 20% 2	27957

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	1 7% 3 8% 6% 6% 6% 5% 7% 9% 43%	5038
	11th to 20th	Day	1 4 2 6% 5% 4 5% 4 6% 7% 57%	5340
	21st to end	Day	1 7% 3 9% 5% 4 4 3 5% 6% 53%	5844
February	1st to 10th	Day	2 6% 4 10% 6% 6% 4 5% 7% 10% 40%	1890
	11th to 20th	Day	3 9% 3 7% 6% 4 6% 5% 7% 10% 40%	1845
	21st to end	Day	1 7% 4 9% 6% 5% 5% 4 7% 8% 44%	1699
March	1st to 10th	Day	2 10% 3 8% 6% 5% 4 4 6% 6% 46%	5064
	11th to 20th	Day	2 9% 3 6% 5% 5% 5% 4 6% 9% 46%	5110
	21st to end	Day	2 10% 3 8% 6% 6% 7% 5% 9% 10% 35%	5607
April	1st to 10th	Day	4 8% 3 6% 5% 5% 4 4 7% 8% 46%	2478
	11th to 20th	Day	4 9% 3 9% 4 6% 5% 3 7% 7% 44%	2491
	21st to end	Day	4 8% 2 8% 5% 6% 6% 4 7% 9% 41%	2662
May	1st to 10th	Day	5% 8% 2 6% 4 5% 5% 4 6% 8% 47%	7626
	11th to 20th	Day	4 4 2 5% 5% 5% 6% 5% 8% 9% 47%	7751
	21st to end	Day	4 4 2 4 4 4 5% 5% 6% 9% 53%	9026
June	1st to 10th	Day	3 3 1 3 4 4 5% 4 6% 10% 57%	2940
	11th to 20th	Day	3 3 1 4 3 3 3 4 6% 8% 61%	2940
	21st to end	Day	2 2 1 4 3 4 3 4 6% 7% 66%	2940
July	1st to 10th	Day	1 2 1 3 2 3 3 3 5% 7% 70%	6479
	11th to 20th	Day	2 2 1 3 3 5% 6% 6% 8% 10% 55%	6104
	21st to end	Day	2 2 1 3 3 4 4 4 7% 8% 63%	6532
August	1st to 10th	Day	2 1 1 4 3 4 5% 5% 8% 9% 58%	5779
	11th to 20th	Day	2 2 1 3 3 3 4 4 7% 9% 65%	5798
	21st to end	Day	4 3 2 5% 4 5% 5% 5% 7% 7% 53%	6082
September	1st to 10th	Day	3 2 1 4 3 3 3 3 5% 7% 66%	2400
	11th to 20th	Day	2 3 1 5% 4 3 5% 3 6% 7% 62%	2291
	21st to end	Day	5% 3 2 4 2 3 2 2 4 5% 68%	2165
October	1st to 10th	Day	4 4 1 3 2 2 3 3 4 5% 70%	3270
	11th to 20th	Day	5% 4 1 3 3 3 4 3 6% 10% 57%	3250
	21st to end	Day	4 5% 2 5% 3 3 5% 4 5% 6% 58%	3548
November	1st to 10th	Day	3 5% 1 6% 4 4 5% 4 6% 8% 56%	2022
	11th to 20th	Day	2 6% 2 6% 4 4 4 3 6% 8% 55%	1680
	21st to end	Day	2 7% 3 6% 5% 4 4 5% 7% 8% 49%	1680
December	1st to 10th	Day	2 5% 2 5% 3 3 4 3 4 6% 62%	2700
	11th to 20th	Day	2 5% 2 5% 4 5% 5% 4 6% 11% 50%	3106
	21st to end	Day	3 10% 4 9% 6% 5% 5% 5% 6% 8% 38%	4092
January	1st to 10th	Night	2 6% 3 8% 5% 5% 7% 5% 8% 9% 42%	7924
	11th to 20th	Night	6% 2 6% 4 4 4 3 5% 7% 58%	7650
	21st to end	Night	1 7% 3 7% 4 5% 5% 4 5% 7% 53%	8370
February	1st to 10th	Night	2 5% 3 8% 7% 4 4 5% 7% 9% 46%	2730
	11th to 20th	Night	2 8% 3 10% 6% 5% 6% 4 5% 10% 42%	2662
	21st to end	Night	1 8% 4 7% 6% 4 5% 4 6% 8% 48%	2102
March	1st to 10th	Night	2 8% 3 8% 5% 5% 4 4 6% 7% 47%	5050
	11th to 20th	Night	2 8% 3 8% 5% 5% 5% 4 6% 8% 46%	5110
	21st to end	Night	4 11% 3 9% 5% 5% 5% 4 6% 9% 38%	5610
April	1st to 10th	Night	4 8% 3 6% 5% 5% 5% 4 6% 7% 47%	2142
	11th to 20th	Night	6% 9% 3 7% 4 5% 5% 4 7% 8% 41%	2077
	21st to end	Night	5% 7% 3 6% 5% 6% 5% 5% 7% 8% 43%	1954
May	1st to 10th	Night	7% 7% 2 6% 4 4 4 3 5% 7% 51%	5321
	11th to 20th	Night	4 4 2 7% 4 5% 6% 4 6% 8% 50%	5125
	21st to end	Night	5% 5% 2 5% 4 5% 6% 5% 7% 9% 48%	5181
June	1st to 10th	Night	3 3 2 4 4 5% 5% 5% 7% 10% 53%	1680
	11th to 20th	Night	5% 3 1 5% 4 4 4 4 5% 7% 58%	1680
	21st to end	Night	2 2 1 4 3 4 5% 4 6% 7% 62%	1680
July	1st to 10th	Night	2 2 1 4 4 4 4 4 7% 8% 59%	3720
	11th to 20th	Night	2 2 1 5% 5% 5% 6% 5% 8% 10% 51%	4091
	21st to end	Night	1 1 1 3 3 3 4 4 7% 9% 62%	4562
August	1st to 10th	Night	1 2 1 4 3 4 4 4 7% 9% 59%	4033
	11th to 20th	Night	2 2 1 4 4 4 5% 5% 6% 8% 60%	4051
	21st to end	Night	2 3 1 5% 5% 5% 6% 5% 6% 8% 54%	4895
September	1st to 10th	Night	3 4 1 4 2 3 4 3 4 6% 66%	2000
	11th to 20th	Night	4 3 1 6% 4 4 4 4 5% 6% 59%	2105
	21st to end	Night	3 2 1 4 3 3 3 3 4 7% 68%	2234
October	1st to 10th	Night	3 3 1 3 2 2 2 2 4 5% 73%	3920
	11th to 20th	Night	4 3 1 4 3 3 4 3 5% 8% 60%	3898
	21st to end	Night	4 5% 2 5% 3 3 4 3 5% 8% 58%	4252
November	1st to 10th	Night	4 5% 2 6% 4 3 4 4 6% 7% 55%	2472
	11th to 20th	Night	2 5% 2 5% 5% 4 3 4 7% 8% 56%	2940
	21st to end	Night	3 6% 3 6% 4 4 4 4 6% 9% 51%	2940
December	1st to 10th	Night	2 7% 2 5% 3 3 3 3 4 6% 63%	4710
	11th to 20th	Night	2 5% 3 6% 4 4 5% 4 7% 10% 50%	5321
	21st to end	Night	2 8% 4 10% 6% 6% 5% 4 6% 8% 42%	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	30% 12% 26% 23% 9%	5041
	11th to 20th	Day	20% 9% 19% 34% 14% 3	5340
	21st to end	Day	30% 8% 16% 25% 19% 2	5844
February	1st to 10th	Day	35% 12% 19% 23% 10% 1	1890
	11th to 20th	Day	36% 9% 19% 25% 10% 1	1854
	21st to end	Day	34% 7% 19% 25% 12% 2	1699
March	1st to 10th	Day	32% 9% 13% 27% 13% 7%	5064
	11th to 20th	Day	31% 8% 16% 28% 16% 2	5110
	21st to end	Day	35% 13% 16% 24% 11% 1	5607
April	1st to 10th	Day	32% 8% 14% 22% 19% 5%	2478
	11th to 20th	Day	34% 8% 14% 21% 19% 4	2494
	21st to end	Day	33% 8% 14% 25% 17% 2	2662
May	1st to 10th	Day	28% 10% 12% 19% 25% 7%	7626
	11th to 20th	Day	25% 8% 11% 23% 25% 8%	7754
	21st to end	Day	22% 6% 11% 27% 29% 6%	9027
June	1st to 10th	Day	19% 7% 11% 23% 29% 12%	2940
	11th to 20th	Day	18% 5% 8% 15% 29% 26%	2940
	21st to end	Day	15% 4 6% 15% 30% 30%	2940
July	1st to 10th	Day	13% 3 5% 9% 17% 52%	6411
	11th to 20th	Day	18% 6% 7% 15% 32% 23%	6033
	21st to end	Day	16% 4 6% 16% 24% 33%	6348
August	1st to 10th	Day	20% 7% 10% 26% 18% 20%	4208
	11th to 20th	Day	17% 6% 11% 23% 26% 18%	4197
	21st to end	Day	17% 6% 10% 20% 24% 22%	4385
September	1st to 10th	Day	17% 3 10% 19% 26% 25%	2400
	11th to 20th	Day	19% 5% 10% 23% 27% 16%	2291
	21st to end	Day	19% 3 5% 24% 35% 14%	2165
October	1st to 10th	Day	16% 3 7% 19% 31% 23%	3270
	11th to 20th	Day	21% 4 10% 33% 28% 4	3250
	21st to end	Day	24% 5% 12% 35% 21% 3	3548
November	1st to 10th	Day	26% 5% 14% 32% 20% 2	2022
	11th to 20th	Day	26% 6% 19% 33% 15% 1	1680
	21st to end	Day	29% 9% 19% 27% 16%	1680
December	1st to 10th	Day	23% 6% 15% 44% 11%	2700
	11th to 20th	Day	26% 10% 28% 28% 7%	3104
	21st to end	Day	40% 10% 18% 21% 10% 2	4092
January	1st to 10th	Night	30% 11% 23% 25% 9% 1	7925
	11th to 20th	Night	23% 8% 17% 36% 15% 2	7650
	21st to end	Night	29% 8% 16% 23% 22% 3	8370
February	1st to 10th	Night	32% 9% 20% 26% 12% 1	2730
	11th to 20th	Night	36% 8% 17% 23% 14% 1	2663
	21st to end	Night	33% 6% 18% 26% 14% 3	2102
March	1st to 10th	Night	32% 6% 12% 28% 16% 6%	5050
	11th to 20th	Night	31% 8% 15% 31% 14% 3	5110
	21st to end	Night	38% 9% 17% 24% 11% 1	5610
April	1st to 10th	Night	34% 7% 13% 22% 19% 5%	2142
	11th to 20th	Night	36% 7% 14% 20% 19% 4	2077
	21st to end	Night	34% 9% 12% 24% 19% 3	1954
May	1st to 10th	Night	30% 7% 10% 21% 27% 6%	5319
	11th to 20th	Night	26% 8% 11% 23% 25% 7%	5126
	21st to end	Night	26% 7% 12% 27% 26% 1	5182
June	1st to 10th	Night	23% 8% 11% 21% 24% 14%	1680
	11th to 20th	Night	24% 4 8% 14% 25% 25%	1680
	21st to end	Night	18% 5% 6% 13% 26% 32%	1680
July	1st to 10th	Night	20% 4 5% 11% 19% 41%	3680
	11th to 20th	Night	24% 5% 6% 16% 26% 23%	4040
	21st to end	Night	15% 5% 7% 18% 25% 29%	4434
August	1st to 10th	Night	21% 4 11% 24% 20% 20%	2928
	11th to 20th	Night	24% 7% 12% 18% 23% 16%	2928
	21st to end	Night	21% 5% 10% 17% 26% 21%	3523
September	1st to 10th	Night	20% 3 7% 18% 26% 26%	2000
	11th to 20th	Night	23% 6% 8% 21% 22% 19%	2105
	21st to end	Night	18% 3 7% 19% 37% 16%	2234
October	1st to 10th	Night	15% 3 6% 17% 38% 21%	3920
	11th to 20th	Night	22% 5% 8% 30% 29% 7%	3898
	21st to end	Night	24% 5% 11% 35% 22% 3	4252
November	1st to 10th	Night	27% 6% 13% 29% 23% 3	2472
	11th to 20th	Night	22% 7% 16% 36% 18% 1	2940
	21st to end	Night	29% 7% 15% 32% 16% 2	2940
December	1st to 10th	Night	22% 6% 15% 41% 14% 1	4710
	11th to 20th	Night	26% 9% 24% 33% 7%	5322
	21st to end	Night	36% 11% 17% 23% 13% 1	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	6% 15% 31% 32% 13% 2	330
	11th to 20th	Day	5% 9% 32% 38% 14% 2	330
	21st to end	Day	5% 11% 27% 42% 15% 1	363
February	1st to 10th	Day	8% 12% 40% 33% 7% 1	330
	11th to 20th	Day	8% 12% 36% 37% 6% 2	330
	21st to end	Day	4 13% 35% 37% 10% 1	321
March	1st to 10th	Day	10% 14% 35% 27% 12% 1	540
	11th to 20th	Day	11% 17% 30% 30% 10% 1	540
	21st to end	Day	12% 23% 35% 24% 6% 1	594
April	1st to 10th	Day	9% 19% 35% 22% 12% 3	540
	11th to 20th	Day	12% 27% 34% 19% 7% 1	532
	21st to end	Day	11% 25% 27% 22% 12% 2	540
May	1st to 10th	Day	10% 21% 34% 24% 9% 1	543
	11th to 20th	Day	9% 16% 31% 27% 14% 3	619
	21st to end	Day	9% 13% 26% 29% 20% 4	844
June	1st to 10th	Day	5% 8% 28% 31% 23% 5%	780
	11th to 20th	Day	6% 16% 26% 32% 18% 2	780
	21st to end	Day	6% 10% 26% 33% 21% 3	780
July	1st to 10th	Day	4 4 23% 35% 29% 4	771
	11th to 20th	Day	2 5% 25% 35% 23% 9%	604
	21st to end	Day	3 6% 19% 38% 26% 7%	616
August	1st to 10th	Day	5% 7% 29% 33% 20% 6%	527
	11th to 20th	Day	4 7% 24% 36% 21% 8%	517
	21st to end	Day	4 6% 26% 32% 25% 6%	583
September	1st to 10th	Day	4 8% 24% 31% 23% 10%	530
	11th to 20th	Day	4 13% 32% 27% 17% 7%	530
	21st to end	Day	7% 15% 21% 29% 21% 7%	495
October	1st to 10th	Day	8% 13% 24% 25% 20% 10%	330
	11th to 20th	Day	9% 15% 30% 23% 19% 4	330
	21st to end	Day	9% 12% 31% 34% 12% 2	363
November	1st to 10th	Day	9% 18% 27% 27% 15% 4	330
	11th to 20th	Day	7% 13% 32% 33% 12% 3	330
	21st to end	Day	8% 8% 28% 39% 15% 2	330
December	1st to 10th	Day	5% 8% 34% 36% 13% 4	330
	11th to 20th	Day	6% 7% 34% 43% 10%	330
	21st to end	Day	14% 12% 28% 36% 8% 2	363
January	1st to 10th	Night	6% 5% 26% 44% 17% 2	955
	11th to 20th	Night	4 5% 28% 48% 14% 2	840
	21st to end	Night	7% 4 27% 48% 12% 2	924
February	1st to 10th	Night	5% 4 33% 48% 10% 1	840
	11th to 20th	Night	5% 5% 31% 47% 11%	824
	21st to end	Night	4 7% 33% 47% 8% 1	692
March	1st to 10th	Night	7% 7% 28% 43% 15% 1	840
	11th to 20th	Night	6% 7% 26% 44% 16% 1	840
	21st to end	Night	8% 7% 30% 41% 13% 1	924
April	1st to 10th	Night	11% 10% 27% 40% 12%	672
	11th to 20th	Night	11% 11% 27% 39% 11% 1	623
	21st to end	Night	8% 13% 28% 32% 16% 2	630
May	1st to 10th	Night	12% 9% 26% 35% 16% 2	630
	11th to 20th	Night	6% 7% 21% 40% 21% 5%	621
	21st to end	Night	9% 7% 20% 39% 22% 3	683
June	1st to 10th	Night	5% 5% 19% 43% 26% 3	630
	11th to 20th	Night	7% 7% 23% 43% 19% 1	630
	21st to end	Night	3 3 18% 46% 27% 2	630
July	1st to 10th	Night	3 2 13% 42% 38% 2	615
	11th to 20th	Night	2 2 10% 42% 39% 5%	612
	21st to end	Night	1 1 9% 39% 45% 4	687
August	1st to 10th	Night	4 1 9% 46% 37% 2	597
	11th to 20th	Night	3 2 10% 46% 35% 5%	594
	21st to end	Night	4 2 10% 42% 35% 7%	660
September	1st to 10th	Night	5% 3 11% 42% 34% 6%	600
	11th to 20th	Night	5% 3 16% 43% 28% 5%	705
	21st to end	Night	5% 3 19% 36% 30% 8%	800
October	1st to 10th	Night	8% 4 17% 45% 22% 5%	800
	11th to 20th	Night	7% 5% 22% 40% 23% 3	800
	21st to end	Night	7% 6% 21% 43% 20% 3	880
November	1st to 10th	Night	7% 5% 21% 42% 23% 2	824
	11th to 20th	Night	4 6% 29% 46% 13% 2	1050
	21st to end	Night	5% 7% 22% 48% 17% 2	1050
December	1st to 10th	Night	7% 5% 24% 49% 15% 1	1050
	11th to 20th	Night	8% 5% 28% 46% 12% 1	1050
	21st to end	Night	8% 8% 29% 45% 8% 2	1155

Page generated at 2026-07-28 01:25:26. Version ac07

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