Yerington
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Yerington clear sky chart from 2005-11-06 to 2026-10-14.

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	2 3 1 4 3 3 3 3 5% 6% 67%	157726
	Night	3 4 2 4 3 3 3 3 5% 7% 64%	151481
Transparency	Day	17% 4 8% 19% 25% 26%	152730
	Night	20% 5% 9% 23% 25% 19%	147470
Seeing	Day	6% 10% 22% 32% 22% 9%	17570
	Night	5% 4 20% 43% 25% 4	26907

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 4 2 6% 4 4 5% 4 6% 9% 54%	4722
	11th to 20th	Day	3 4 2 4 3 2 3 2 4 6% 67%	4740
	21st to end	Day	3 8% 2 6% 4 4 4 4 6% 9% 49%	5843
February	1st to 10th	Day	2 5% 2 5% 4 3 4 4 6% 9% 56%	1957
	11th to 20th	Day	2 7% 3 6% 4 4 5% 3 6% 10% 52%	2050
	21st to end	Day	1 4 3 7% 3 4 3 3 6% 8% 57%	1730
March	1st to 10th	Day	3 9% 3 7% 5% 5% 5% 4 6% 9% 43%	4618
	11th to 20th	Day	1 3 2 4 3 3 3 3 6% 8% 64%	4902
	21st to end	Day	3 5% 2 6% 4 4 5% 3 6% 8% 54%	6051
April	1st to 10th	Day	3 5% 1 4 5% 4 4 4 5% 8% 57%	2520
	11th to 20th	Day	3 5% 1 4 4 3 3 3 5% 7% 61%	2489
	21st to end	Day	4 4 1 3 3 3 4 4 5% 7% 62%	2520
May	1st to 10th	Day	5% 4 1 3 2 2 2 3 4 5% 68%	7527
	11th to 20th	Day	2 2 1 3 2 2 2 2 3 5% 74%	7816
	21st to end	Day	3 3 1 4 3 3 3 3 4 5% 68%	8992
June	1st to 10th	Day	3 3 1 3 3 3 3 3 5% 7% 65%	2940
	11th to 20th	Day	2 1 3 1 2 2 2 4 5% 76%	2940
	21st to end	Day	2 2 1 2 2 2 2 2 3 4 77%	2940
July	1st to 10th	Day	1 1 1 1 2 2 2 3 3 85%	8219
	11th to 20th	Day	2 2 1 3 2 3 3 3 4 6% 72%	8220
	21st to end	Day	1 1 1 3 2 3 3 3 5% 5% 72%	8889
August	1st to 10th	Day	1 1 1 2 1 2 2 2 3 4 81%	7293
	11th to 20th	Day	1 1 1 2 2 2 2 2 4 4 78%	7001
	21st to end	Day	4 2 1 4 3 3 3 3 4 5% 68%	7750
September	1st to 10th	Day	2 1 1 2 2 2 2 2 3 4 79%	2520
	11th to 20th	Day	1 2 1 3 2 2 3 2 4 5% 76%	2447
	21st to end	Day	2 2 1 2 1 2 2 2 3 4 79%	2310
October	1st to 10th	Day	2 2 1 2 3 2 2 2 4 5% 75%	3545
	11th to 20th	Day	3 2 1 2 2 2 1 1 3 4 79%	3292
	21st to end	Day	1 2 1 3 2 3 3 3 5% 7% 69%	3401
November	1st to 10th	Day	2 3 2 3 2 3 4 3 6% 7% 65%	1854
	11th to 20th	Day	3 3 1 3 3 2 4 4 6% 8% 63%	1890
	21st to end	Day	2 4 2 4 3 3 4 3 6% 7% 62%	1890
December	1st to 10th	Day	2 3 1 3 3 2 3 3 5% 8% 68%	2708
	11th to 20th	Day	3 5% 2 6% 5% 5% 6% 5% 8% 9% 46%	3108
	21st to end	Day	3 6% 3 7% 5% 5% 5% 4 7% 11% 45%	4092
January	1st to 10th	Night	2 6% 2 6% 3 3 4 3 6% 9% 58%	8172
	11th to 20th	Night	2 5% 2 5% 3 3 3 3 4 6% 66%	8204
	21st to end	Night	3 7% 3 6% 4 4 4 3 5% 8% 52%	8371
February	1st to 10th	Night	2 7% 2 5% 3 4 4 3 6% 7% 55%	2662
	11th to 20th	Night	2 5% 2 5% 4 4 4 4 7% 8% 55%	2458
	21st to end	Night	2 4 2 6% 4 4 4 4 5% 9% 56%	2076
March	1st to 10th	Night	3 9% 4 8% 5% 4 4 3 5% 6% 50%	5496
	11th to 20th	Night	2 5% 2 5% 4 4 3 3 5% 7% 61%	5303
	21st to end	Night	3 6% 2 6% 4 4 4 4 5% 8% 53%	5166
April	1st to 10th	Night	4 5% 2 4 3 4 4 4 5% 7% 58%	2100
	11th to 20th	Night	3 4 1 3 3 3 3 4 4 8% 62%	2079
	21st to end	Night	7% 6% 2 5% 3 2 3 2 4 6% 61%	2100
May	1st to 10th	Night	6% 3 1 4 2 2 3 2 3 4 68%	5423
	11th to 20th	Night	3 3 1 3 2 2 2 2 3 4 74%	5058
	21st to end	Night	3 3 1 4 2 3 4 3 4 7% 66%	5181
June	1st to 10th	Night	4 4 1 3 2 3 4 3 5% 7% 65%	1680
	11th to 20th	Night	2 1 2 1 2 2 2 3 5% 79%	1680
	21st to end	Night	2 2 2 2 2 2 2 2 3 80%	1680
July	1st to 10th	Night	1 1 1 1 2 2 2 3 3 85%	4740
	11th to 20th	Night	3 3 1 4 3 4 4 2 4 5% 67%	4740
	21st to end	Night	2 1 1 3 2 3 4 3 5% 5% 70%	5170
August	1st to 10th	Night	1 1 1 2 1 2 2 2 3 4 81%	5528
	11th to 20th	Night	2 2 1 3 2 2 3 3 4 6% 71%	5886
	21st to end	Night	5% 2 1 4 2 3 3 3 4 6% 67%	6499
September	1st to 10th	Night	2 1 1 2 2 2 2 2 3 4 80%	2100
	11th to 20th	Night	3 2 1 3 2 2 2 2 3 4 74%	2173
	21st to end	Night	3 2 1 2 2 2 2 2 3 5% 76%	2310
October	1st to 10th	Night	3 2 1 3 2 3 3 2 3 4 74%	3872
	11th to 20th	Night	2 2 1 2 2 1 2 2 3 6% 78%	3933
	21st to end	Night	3 3 1 3 2 2 2 2 4 5% 72%	4404
November	1st to 10th	Night	3 3 2 4 2 2 3 3 5% 6% 68%	2665
	11th to 20th	Night	2 4 2 3 3 3 3 3 4 7% 66%	2730
	21st to end	Night	3 3 2 4 3 3 3 3 5% 8% 63%	2730
December	1st to 10th	Night	2 3 1 3 3 3 4 3 4 9% 64%	4690
	11th to 20th	Night	3 6% 2 6% 4 4 5% 4 8% 13% 45%	5316
	21st to end	Night	3 8% 3 8% 5% 5% 6% 5% 8% 11% 38%	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	22% 8% 21% 37% 12%	4723
	11th to 20th	Day	18% 5% 11% 25% 35% 6%	4740
	21st to end	Day	29% 7% 11% 23% 25% 5%	5843
February	1st to 10th	Day	24% 6% 13% 28% 20% 9%	1957
	11th to 20th	Day	27% 5% 10% 29% 23% 5%	2060
	21st to end	Day	24% 5% 16% 31% 18% 7%	1730
March	1st to 10th	Day	32% 8% 10% 25% 20% 6%	4618
	11th to 20th	Day	17% 5% 13% 31% 28% 6%	4902
	21st to end	Day	25% 7% 14% 23% 24% 6%	6051
April	1st to 10th	Day	25% 7% 11% 24% 24% 10%	2520
	11th to 20th	Day	22% 5% 10% 25% 26% 12%	2492
	21st to end	Day	22% 5% 9% 28% 28% 8%	2520
May	1st to 10th	Day	19% 4 6% 20% 36% 15%	7527
	11th to 20th	Day	12% 4 5% 19% 36% 25%	7819
	21st to end	Day	17% 5% 6% 18% 36% 18%	8994
June	1st to 10th	Day	18% 5% 7% 19% 31% 20%	2940
	11th to 20th	Day	11% 3 6% 16% 30% 35%	2940
	21st to end	Day	11% 3 4 8% 26% 48%	2940
July	1st to 10th	Day	7% 2 2 5% 14% 69%	8151
	11th to 20th	Day	13% 3 4 9% 13% 58%	8145
	21st to end	Day	12% 4 4 11% 21% 48%	8690
August	1st to 10th	Day	11% 3 3 7% 22% 54%	5777
	11th to 20th	Day	12% 3 4 14% 19% 48%	5517
	21st to end	Day	16% 3 3 14% 25% 40%	6077
September	1st to 10th	Day	11% 3 3 9% 27% 47%	2520
	11th to 20th	Day	13% 3 4 15% 31% 34%	2447
	21st to end	Day	11% 2 3 16% 34% 34%	2310
October	1st to 10th	Day	13% 3 5% 11% 30% 39%	3545
	11th to 20th	Day	12% 2 4 17% 45% 21%	3292
	21st to end	Day	14% 4 5% 28% 35% 13%	3401
November	1st to 10th	Day	17% 5% 12% 27% 30% 9%	1854
	11th to 20th	Day	17% 6% 15% 29% 29% 4	1890
	21st to end	Day	21% 4 13% 29% 28% 5%	1890
December	1st to 10th	Day	16% 5% 14% 33% 29% 4	2708
	11th to 20th	Day	30% 9% 18% 26% 14% 3	3108
	21st to end	Day	29% 9% 25% 27% 10% 1	4092
January	1st to 10th	Night	23% 7% 22% 35% 12% 1	8172
	11th to 20th	Night	19% 6% 9% 28% 34% 4	8204
	21st to end	Night	29% 6% 11% 28% 24% 2	8371
February	1st to 10th	Night	27% 5% 14% 28% 20% 7%	2662
	11th to 20th	Night	25% 6% 11% 33% 20% 4	2459
	21st to end	Night	22% 7% 16% 32% 16% 7%	2076
March	1st to 10th	Night	30% 7% 8% 27% 20% 7%	5496
	11th to 20th	Night	21% 5% 10% 40% 20% 4	5303
	21st to end	Night	26% 8% 16% 30% 17% 4	5166
April	1st to 10th	Night	24% 5% 13% 29% 21% 8%	2100
	11th to 20th	Night	21% 6% 10% 29% 23% 11%	2079
	21st to end	Night	25% 5% 9% 27% 29% 5%	2100
May	1st to 10th	Night	19% 4 6% 20% 36% 15%	5421
	11th to 20th	Night	14% 4 5% 15% 41% 21%	5059
	21st to end	Night	16% 5% 7% 18% 40% 14%	5182
June	1st to 10th	Night	18% 5% 8% 19% 31% 19%	1680
	11th to 20th	Night	9% 4 5% 14% 32% 36%	1680
	21st to end	Night	11% 2 4 12% 27% 45%	1680
July	1st to 10th	Night	6% 2 2 7% 16% 67%	4700
	11th to 20th	Night	18% 3 3 7% 12% 57%	4692
	21st to end	Night	14% 3 4 15% 18% 46%	5057
August	1st to 10th	Night	10% 3 3 8% 24% 51%	4374
	11th to 20th	Night	13% 3 6% 16% 17% 45%	4636
	21st to end	Night	15% 2 4 14% 26% 39%	5092
September	1st to 10th	Night	9% 2 4 10% 29% 45%	2100
	11th to 20th	Night	14% 3 5% 15% 29% 34%	2173
	21st to end	Night	13% 2 4 13% 34% 33%	2310
October	1st to 10th	Night	15% 3 4 12% 29% 37%	3872
	11th to 20th	Night	10% 3 6% 16% 47% 19%	3933
	21st to end	Night	14% 4 4 24% 38% 15%	4404
November	1st to 10th	Night	17% 5% 11% 30% 27% 11%	2665
	11th to 20th	Night	19% 5% 11% 31% 28% 6%	2730
	21st to end	Night	21% 4 10% 31% 29% 5%	2730
December	1st to 10th	Night	18% 5% 12% 32% 25% 7%	4690
	11th to 20th	Night	27% 8% 19% 29% 15% 1	5316
	21st to end	Night	35% 10% 17% 23% 13% 1	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	8% 7% 26% 38% 17% 5%	220
	11th to 20th	Day	3 6% 21% 36% 25% 10%	220
	21st to end	Day	7% 7% 20% 33% 27% 7%	473
February	1st to 10th	Day	6% 15% 20% 35% 17% 7%	466
	11th to 20th	Day	8% 12% 24% 37% 17% 2	535
	21st to end	Day	6% 14% 26% 37% 15% 1	446
March	1st to 10th	Day	11% 15% 24% 33% 14% 3	540
	11th to 20th	Day	7% 15% 27% 31% 14% 5%	540
	21st to end	Day	10% 17% 26% 29% 15% 3	594
April	1st to 10th	Day	8% 16% 26% 28% 15% 6%	540
	11th to 20th	Day	10% 17% 23% 29% 14% 6%	532
	21st to end	Day	9% 16% 27% 24% 17% 7%	540
May	1st to 10th	Day	11% 14% 26% 28% 15% 6%	543
	11th to 20th	Day	11% 14% 24% 27% 17% 7%	568
	21st to end	Day	8% 11% 20% 30% 21% 10%	617
June	1st to 10th	Day	4 13% 23% 28% 22% 10%	570
	11th to 20th	Day	6% 12% 26% 29% 20% 8%	570
	21st to end	Day	3 9% 24% 32% 24% 9%	570
July	1st to 10th	Day	2 7% 24% 34% 23% 11%	566
	11th to 20th	Day	3 5% 20% 32% 29% 12%	564
	21st to end	Day	3 4 19% 32% 30% 13%	619
August	1st to 10th	Day	3 6% 20% 32% 24% 15%	567
	11th to 20th	Day	1 6% 25% 28% 25% 15%	557
	21st to end	Day	3 5% 20% 32% 29% 11%	627
September	1st to 10th	Day	2 6% 20% 33% 26% 13%	570
	11th to 20th	Day	3 9% 22% 35% 24% 8%	570
	21st to end	Day	2 6% 21% 37% 26% 9%	570
October	1st to 10th	Day	4 8% 22% 30% 25% 11%	570
	11th to 20th	Day	4 9% 18% 33% 27% 9%	543
	21st to end	Day	5% 7% 17% 34% 27% 9%	488
November	1st to 10th	Day	4 5% 19% 31% 27% 13%	330
	11th to 20th	Day	2 5% 20% 38% 24% 12%	330
	21st to end	Day	5% 6% 18% 33% 31% 8%	330
December	1st to 10th	Day	4 5% 16% 33% 26% 15%	223
	11th to 20th	Day	6% 7% 21% 33% 20% 12%	220
	21st to end	Day	11% 9% 21% 34% 17% 7%	242
January	1st to 10th	Night	5% 4 24% 40% 19% 8%	840
	11th to 20th	Night	3 3 21% 42% 25% 5%	840
	21st to end	Night	6% 2 19% 45% 21% 6%	924
February	1st to 10th	Night	5% 6% 22% 42% 22% 3	840
	11th to 20th	Night	4 4 27% 40% 20% 4	824
	21st to end	Night	4 3 29% 47% 15% 3	692
March	1st to 10th	Night	7% 6% 27% 40% 18% 3	840
	11th to 20th	Night	3 7% 25% 39% 21% 4	840
	21st to end	Night	6% 6% 30% 42% 15% 2	924
April	1st to 10th	Night	5% 8% 24% 40% 21% 1	840
	11th to 20th	Night	6% 7% 27% 37% 19% 4	831
	21st to end	Night	7% 8% 24% 37% 20% 3	840
May	1st to 10th	Night	7% 7% 27% 39% 18% 2	667
	11th to 20th	Night	7% 4 25% 40% 23% 1	540
	21st to end	Night	8% 2 17% 45% 24% 3	455
June	1st to 10th	Night	6% 2 16% 49% 26% 2	420
	11th to 20th	Night	1 2 19% 52% 24% 2	420
	21st to end	Night	2 1 13% 58% 25% 1	420
July	1st to 10th	Night	2 9% 58% 30% 1	410
	11th to 20th	Night	2 1 8% 57% 32%	408
	21st to end	Night	3 2 5% 55% 35% 1	465
August	1st to 10th	Night	3 1 11% 45% 38% 2	715
	11th to 20th	Night	2 2 15% 45% 33% 3	832
	21st to end	Night	3 2 13% 44% 35% 3	924
September	1st to 10th	Night	2 2 13% 40% 38% 5%	840
	11th to 20th	Night	3 3 15% 40% 35% 5%	840
	21st to end	Night	4 2 13% 40% 35% 6%	840
October	1st to 10th	Night	5% 3 14% 42% 29% 7%	840
	11th to 20th	Night	4 2 15% 39% 34% 6%	812
	21st to end	Night	3 2 15% 39% 29% 12%	880
November	1st to 10th	Night	3 2 18% 40% 27% 10%	820
	11th to 20th	Night	4 3 18% 46% 23% 6%	840
	21st to end	Night	4 3 17% 45% 26% 5%	840
December	1st to 10th	Night	6% 2 22% 42% 23% 6%	840
	11th to 20th	Night	7% 2 22% 43% 21% 5%	840
	21st to end	Night	7% 5% 27% 43% 15% 2	924

Page generated at 2026-10-11 02:06:33. Version ac07

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