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 2025-06-10.

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% 66%	123347
	Night	3 4 2 4 3 3 3 3 5% 7% 64%	123732
Transparency	Day	18% 5% 9% 20% 26% 23%	123090
	Night	20% 5% 10% 23% 25% 17%	123577
Seeing	Day	6% 10% 23% 32% 21% 8%	15761
	Night	5% 4 20% 42% 25% 4	25226

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% 55%	3639
	11th to 20th	Day	3 5% 2 5% 3 3 3 3 4 6% 62%	3640
	21st to end	Day	4 9% 3 6% 4 4 4 4 6% 7% 49%	4510
February	1st to 10th	Day	2 6% 2 5% 3 3 4 4 6% 9% 56%	1864
	11th to 20th	Day	2 6% 3 5% 3 4 5% 3 6% 10% 53%	1950
	21st to end	Day	1 4 3 7% 3 4 3 3 6% 8% 58%	1650
March	1st to 10th	Day	3 9% 3 7% 5% 5% 5% 4 7% 9% 42%	4518
	11th to 20th	Day	1 3 2 4 3 3 3 4 6% 8% 63%	4797
	21st to end	Day	3 5% 2 6% 4 4 5% 3 6% 8% 54%	5920
April	1st to 10th	Day	3 5% 2 4 5% 4 4 4 5% 7% 57%	2400
	11th to 20th	Day	4 5% 1 4 4 3 3 3 5% 7% 60%	2369
	21st to end	Day	5% 4 1 3 3 3 3 4 5% 6% 62%	2400
May	1st to 10th	Day	5% 4 1 3 2 2 2 2 3 5% 69%	5807
	11th to 20th	Day	3 3 1 3 2 2 3 2 4 5% 72%	6009
	21st to end	Day	3 2 1 3 3 2 3 2 4 5% 72%	6902
June	1st to 10th	Day	3 3 1 3 3 4 3 3 5% 7% 64%	2789
	11th to 20th	Day	2 2 3 2 3 2 2 4 5% 75%	2660
	21st to end	Day	2 1 1 2 3 2 3 2 3 4 77%	2660
July	1st to 10th	Day	1 1 1 2 1 2 2 2 2 3 84%	4420
	11th to 20th	Day	2 2 1 3 3 3 3 3 5% 6% 68%	4420
	21st to end	Day	2 2 1 3 2 3 4 3 4 5% 72%	4770
August	1st to 10th	Day	2 2 1 3 2 3 3 3 4 5% 72%	3949
	11th to 20th	Day	1 1 1 1 2 2 3 3 85%	3724
	21st to end	Day	2 1 1 2 1 1 1 1 2 3 84%	4180
September	1st to 10th	Day	2 1 1 2 2 2 2 2 3 4 80%	2280
	11th to 20th	Day	2 2 1 2 2 2 3 2 4 5% 76%	2214
	21st to end	Day	2 2 1 2 1 2 2 2 3 4 80%	2090
October	1st to 10th	Day	2 2 1 3 3 2 2 2 4 5% 75%	3335
	11th to 20th	Day	3 2 1 2 2 2 1 1 3 4 79%	3161
	21st to end	Day	1 2 1 3 2 3 4 3 5% 7% 69%	3296
November	1st to 10th	Day	3 4 2 3 2 3 4 3 5% 7% 64%	1764
	11th to 20th	Day	2 2 1 2 3 2 3 4 7% 8% 65%	1800
	21st to end	Day	3 4 2 4 3 3 4 3 6% 7% 61%	1800
December	1st to 10th	Day	2 3 1 3 3 2 4 3 5% 7% 68%	2628
	11th to 20th	Day	3 5% 2 6% 5% 5% 6% 5% 7% 9% 45%	3028
	21st to end	Day	3 6% 3 7% 5% 5% 5% 4 7% 11% 45%	4004
January	1st to 10th	Night	2 6% 2 5% 3 3 4 3 6% 9% 58%	6306
	11th to 20th	Night	2 6% 3 7% 4 3 3 3 4 5% 60%	6304
	21st to end	Night	4 8% 3 6% 3 3 4 3 5% 7% 53%	6468
February	1st to 10th	Night	2 7% 2 5% 3 4 4 3 7% 7% 55%	2535
	11th to 20th	Night	2 5% 2 5% 3 3 4 4 7% 8% 56%	2338
	21st to end	Night	2 5% 2 6% 4 4 4 4 5% 8% 56%	1980
March	1st to 10th	Night	3 9% 4 8% 5% 4 4 3 5% 6% 49%	5376
	11th to 20th	Night	2 5% 2 5% 4 4 3 3 5% 7% 61%	5188
	21st to end	Night	3 6% 2 6% 4 4 4 4 5% 8% 53%	5055
April	1st to 10th	Night	4 5% 2 4 3 4 4 4 5% 7% 58%	2000
	11th to 20th	Night	4 4 2 2 3 3 3 4 4 7% 63%	1979
	21st to end	Night	7% 6% 2 5% 3 2 3 2 4 6% 61%	2000
May	1st to 10th	Night	5% 3 1 3 2 2 2 2 3 4 72%	4174
	11th to 20th	Night	4 3 1 3 3 2 3 2 4 5% 71%	3892
	21st to end	Night	3 2 1 3 1 2 3 3 3 6% 73%	3972
June	1st to 10th	Night	4 4 1 4 3 3 4 3 4 7% 65%	1595
	11th to 20th	Night	2 1 2 1 2 2 2 4 6% 77%	1520
	21st to end	Night	2 2 2 2 2 2 3 2 4 79%	1520
July	1st to 10th	Night	1 1 1 1 1 1 1 2 3 88%	2540
	11th to 20th	Night	2 3 1 4 3 3 4 2 5% 6% 67%	2540
	21st to end	Night	2 2 1 3 2 3 3 3 5% 5% 70%	2778
August	1st to 10th	Night	2 2 1 3 2 2 3 2 4 5% 73%	2993
	11th to 20th	Night	1 1 1 2 1 2 2 2 3 3 83%	3126
	21st to end	Night	4 1 1 1 1 1 1 2 3 85%	3498
September	1st to 10th	Night	2 1 1 2 2 2 1 2 3 3 82%	1900
	11th to 20th	Night	2 2 1 4 2 2 2 2 3 4 74%	1966
	21st to end	Night	3 2 1 2 1 2 2 2 3 4 77%	2090
October	1st to 10th	Night	3 2 1 3 2 2 3 2 3 4 74%	3642
	11th to 20th	Night	2 1 1 2 2 1 2 2 3 6% 78%	3777
	21st to end	Night	3 3 1 3 2 2 2 2 4 5% 72%	4267
November	1st to 10th	Night	3 3 2 4 2 2 3 3 5% 6% 68%	2535
	11th to 20th	Night	2 4 2 3 3 2 3 3 4 7% 67%	2600
	21st to end	Night	3 3 2 4 3 3 3 3 5% 7% 63%	2600
December	1st to 10th	Night	2 3 1 4 3 3 4 3 5% 8% 64%	4550
	11th to 20th	Night	3 6% 2 6% 4 4 5% 4 8% 12% 45%	5176
	21st to end	Night	3 8% 3 8% 5% 5% 6% 5% 8% 11% 37%	6952

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	21% 9% 23% 33% 13%	3639
	11th to 20th	Day	22% 6% 12% 29% 27% 4	3640
	21st to end	Day	32% 8% 12% 20% 24% 5%	4510
February	1st to 10th	Day	24% 6% 14% 28% 20% 9%	1864
	11th to 20th	Day	27% 5% 11% 30% 23% 5%	1960
	21st to end	Day	24% 4 14% 32% 19% 7%	1650
March	1st to 10th	Day	32% 8% 10% 25% 20% 6%	4518
	11th to 20th	Day	17% 5% 13% 31% 28% 5%	4797
	21st to end	Day	25% 8% 14% 23% 24% 6%	5920
April	1st to 10th	Day	25% 7% 10% 25% 24% 9%	2400
	11th to 20th	Day	22% 5% 10% 25% 26% 12%	2372
	21st to end	Day	22% 5% 10% 29% 27% 8%	2400
May	1st to 10th	Day	17% 4 6% 23% 40% 10%	5807
	11th to 20th	Day	13% 4 6% 22% 35% 19%	6012
	21st to end	Day	14% 5% 5% 15% 38% 22%	6904
June	1st to 10th	Day	19% 5% 7% 19% 31% 19%	2789
	11th to 20th	Day	11% 3 6% 17% 31% 31%	2660
	21st to end	Day	12% 3 4 8% 24% 48%	2660
July	1st to 10th	Day	8% 2 2 6% 11% 71%	4351
	11th to 20th	Day	15% 3 5% 8% 13% 56%	4345
	21st to end	Day	14% 4 4 9% 18% 50%	4619
August	1st to 10th	Day	14% 3 4 8% 21% 50%	3934
	11th to 20th	Day	6% 2 3 5% 15% 69%	3760
	21st to end	Day	10% 2 2 7% 27% 53%	4179
September	1st to 10th	Day	10% 2 3 8% 25% 51%	2280
	11th to 20th	Day	12% 4 5% 15% 31% 33%	2214
	21st to end	Day	11% 2 3 16% 33% 35%	2090
October	1st to 10th	Day	13% 3 5% 11% 30% 39%	3335
	11th to 20th	Day	11% 2 4 17% 45% 21%	3161
	21st to end	Day	14% 4 5% 27% 35% 14%	3296
November	1st to 10th	Day	18% 5% 12% 26% 30% 8%	1764
	11th to 20th	Day	15% 5% 15% 29% 31% 5%	1800
	21st to end	Day	22% 4 13% 28% 28% 5%	1800
December	1st to 10th	Day	16% 5% 13% 32% 29% 4	2628
	11th to 20th	Day	30% 9% 18% 26% 14% 2	3028
	21st to end	Day	29% 9% 25% 27% 9% 1	4004
January	1st to 10th	Night	23% 7% 24% 32% 12% 2	6306
	11th to 20th	Night	24% 7% 11% 30% 25% 3	6304
	21st to end	Night	29% 7% 12% 25% 25% 2	6468
February	1st to 10th	Night	27% 5% 14% 28% 19% 7%	2535
	11th to 20th	Night	24% 6% 12% 33% 21% 4	2339
	21st to end	Night	22% 7% 15% 32% 17% 8%	1980
March	1st to 10th	Night	30% 7% 8% 27% 20% 7%	5376
	11th to 20th	Night	21% 5% 11% 40% 20% 3	5188
	21st to end	Night	26% 8% 16% 30% 17% 4	5055
April	1st to 10th	Night	25% 5% 14% 29% 20% 7%	2000
	11th to 20th	Night	21% 6% 10% 29% 22% 11%	1979
	21st to end	Night	25% 5% 9% 27% 29% 5%	2000
May	1st to 10th	Night	16% 4 6% 24% 42% 9%	4171
	11th to 20th	Night	16% 4 6% 18% 39% 17%	3893
	21st to end	Night	12% 4 7% 16% 44% 18%	3972
June	1st to 10th	Night	19% 5% 8% 20% 31% 18%	1595
	11th to 20th	Night	10% 4 6% 15% 34% 31%	1520
	21st to end	Night	11% 2 4 12% 27% 44%	1520
July	1st to 10th	Night	5% 1 2 6% 14% 71%	2500
	11th to 20th	Night	17% 3 4 8% 14% 55%	2492
	21st to end	Night	14% 3 4 11% 16% 51%	2691
August	1st to 10th	Night	13% 3 4 10% 22% 48%	2984
	11th to 20th	Night	8% 2 3 6% 17% 64%	3156
	21st to end	Night	9% 1 2 7% 30% 51%	3498
September	1st to 10th	Night	9% 2 3 8% 29% 49%	1900
	11th to 20th	Night	14% 3 6% 16% 29% 33%	1966
	21st to end	Night	13% 2 4 13% 33% 35%	2090
October	1st to 10th	Night	15% 3 4 11% 30% 36%	3642
	11th to 20th	Night	9% 3 6% 16% 47% 19%	3777
	21st to end	Night	14% 4 4 24% 38% 16%	4267
November	1st to 10th	Night	17% 5% 10% 29% 27% 11%	2535
	11th to 20th	Night	17% 5% 11% 31% 29% 6%	2600
	21st to end	Night	22% 4 10% 29% 30% 5%	2600
December	1st to 10th	Night	19% 5% 12% 31% 26% 7%	4550
	11th to 20th	Night	28% 8% 20% 29% 14% 1	5176
	21st to end	Night	36% 10% 17% 23% 13% 1	6952

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% 18% 5%	200
	11th to 20th	Day	3 7% 23% 38% 24% 7%	200
	21st to end	Day	7% 7% 21% 33% 26% 6%	440
February	1st to 10th	Day	6% 16% 21% 34% 16% 7%	433
	11th to 20th	Day	8% 13% 23% 36% 18% 2	495
	21st to end	Day	6% 15% 26% 36% 15% 1	414
March	1st to 10th	Day	11% 15% 24% 33% 14% 3	500
	11th to 20th	Day	8% 16% 27% 31% 13% 5%	500
	21st to end	Day	10% 18% 25% 30% 15% 2	550
April	1st to 10th	Day	8% 16% 28% 27% 15% 5%	500
	11th to 20th	Day	10% 18% 23% 29% 14% 5%	492
	21st to end	Day	9% 16% 27% 24% 16% 7%	500
May	1st to 10th	Day	11% 15% 26% 27% 14% 6%	503
	11th to 20th	Day	11% 15% 23% 27% 17% 6%	528
	21st to end	Day	8% 11% 20% 30% 20% 10%	573
June	1st to 10th	Day	4 13% 22% 27% 23% 10%	527
	11th to 20th	Day	6% 12% 26% 29% 19% 7%	490
	21st to end	Day	3 9% 24% 31% 25% 9%	490
July	1st to 10th	Day	2 7% 23% 32% 23% 12%	486
	11th to 20th	Day	3 5% 20% 31% 29% 12%	484
	21st to end	Day	3 4 20% 31% 29% 12%	531
August	1st to 10th	Day	4 7% 20% 31% 24% 14%	487
	11th to 20th	Day	1 7% 26% 29% 23% 14%	477
	21st to end	Day	2 5% 22% 33% 27% 10%	539
September	1st to 10th	Day	3 6% 20% 32% 27% 13%	490
	11th to 20th	Day	3 9% 22% 36% 22% 8%	490
	21st to end	Day	2 6% 21% 37% 26% 8%	490
October	1st to 10th	Day	3 8% 22% 30% 26% 10%	490
	11th to 20th	Day	4 8% 18% 34% 28% 8%	490
	21st to end	Day	4 8% 18% 35% 26% 9%	449
November	1st to 10th	Day	4 6% 21% 31% 27% 11%	300
	11th to 20th	Day	2 5% 19% 37% 25% 13%	300
	21st to end	Day	5% 6% 19% 33% 29% 8%	300
December	1st to 10th	Day	4 6% 17% 33% 25% 15%	203
	11th to 20th	Day	6% 7% 22% 35% 22% 9%	200
	21st to end	Day	10% 8% 20% 36% 18% 7%	220
January	1st to 10th	Night	5% 4 23% 40% 20% 8%	800
	11th to 20th	Night	3 3 22% 43% 23% 6%	800
	21st to end	Night	6% 3 19% 45% 21% 6%	880
February	1st to 10th	Night	5% 6% 23% 41% 22% 4	800
	11th to 20th	Night	3 4 27% 40% 21% 4	784
	21st to end	Night	4 3 29% 46% 15% 3	660
March	1st to 10th	Night	7% 6% 27% 40% 18% 3	800
	11th to 20th	Night	4 7% 25% 39% 21% 4	800
	21st to end	Night	6% 6% 29% 41% 16% 2	880
April	1st to 10th	Night	6% 8% 25% 40% 21% 2	800
	11th to 20th	Night	7% 7% 27% 37% 19% 4	791
	21st to end	Night	7% 8% 24% 38% 20% 4	800
May	1st to 10th	Night	7% 8% 27% 38% 18% 2	635
	11th to 20th	Night	7% 4 25% 39% 23% 1	514
	21st to end	Night	8% 3 17% 45% 24% 3	433
June	1st to 10th	Night	6% 2 16% 47% 28% 2	399
	11th to 20th	Night	2 2 20% 49% 26% 2	380
	21st to end	Night	2 1 12% 57% 27% 2	380
July	1st to 10th	Night	2 1 9% 55% 32% 1	370
	11th to 20th	Night	2 1 9% 55% 33% 1	368
	21st to end	Night	3 2 6% 52% 37% 1	421
August	1st to 10th	Night	3 1 11% 44% 38% 3	647
	11th to 20th	Night	2 2 14% 45% 32% 4	752
	21st to end	Night	2 1 13% 44% 37% 3	836
September	1st to 10th	Night	2 2 12% 39% 40% 5%	760
	11th to 20th	Night	3 3 14% 39% 36% 6%	760
	21st to end	Night	4 2 13% 38% 37% 6%	760
October	1st to 10th	Night	5% 3 13% 43% 29% 8%	760
	11th to 20th	Night	3 2 14% 40% 35% 6%	760
	21st to end	Night	3 3 15% 39% 28% 12%	836
November	1st to 10th	Night	3 2 17% 41% 27% 9%	780
	11th to 20th	Night	4 3 18% 45% 24% 6%	800
	21st to end	Night	4 3 17% 44% 26% 5%	800
December	1st to 10th	Night	6% 2 22% 42% 23% 6%	800
	11th to 20th	Night	7% 2 21% 43% 20% 5%	800
	21st to end	Night	7% 4 27% 44% 16% 2	880

Page generated at 2025-06-07 07:28:16. Version ac07

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