Lemon Lake Reservoir
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lemon Lake Reservoir clear sky chart from 2005-11-06 to 2025-03-27.

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	5% 7% 2 6% 4 4 5% 4 6% 7% 51%	113007
	Night	5% 7% 2 5% 3 3 3 3 5% 6% 56%	115202
Transparency	Day	30% 7% 10% 19% 23% 10%	112770
	Night	28% 5% 9% 19% 26% 13%	115028
Seeing	Day	13% 17% 28% 26% 11% 3	15654
	Night	10% 7% 27% 35% 18% 3	25969

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 8% 4 9% 3 3 3 4 5% 6% 54%	4076
	11th to 20th	Day	2 6% 2 5% 3 3 3 4 5% 6% 59%	4100
	21st to end	Day	3 11% 3 5% 4 3 3 3 4 4 57%	4510
February	1st to 10th	Day	2 12% 4 7% 4 3 3 3 5% 4 54%	1800
	11th to 20th	Day	5% 12% 3 8% 4 3 4 4 5% 6% 47%	1817
	21st to end	Day	3 13% 6% 7% 3 3 4 2 4 5% 50%	1653
March	1st to 10th	Day	3 12% 4 8% 5% 4 4 4 6% 8% 42%	3554
	11th to 20th	Day	4 18% 5% 8% 4 4 4 4 6% 6% 38%	3600
	21st to end	Day	5% 17% 4 10% 5% 4 4 3 4 6% 38%	3908
April	1st to 10th	Day	5% 9% 2 7% 4 4 4 3 5% 6% 51%	2280
	11th to 20th	Day	4 9% 2 6% 5% 5% 5% 4 6% 7% 48%	2251
	21st to end	Day	6% 7% 2 7% 4 4 4 5% 6% 6% 48%	2280
May	1st to 10th	Day	7% 6% 2 6% 5% 4 4 4 6% 6% 52%	3976
	11th to 20th	Day	5% 6% 2 7% 5% 6% 6% 6% 7% 7% 42%	4071
	21st to end	Day	5% 5% 1 6% 4 4 5% 4 6% 7% 54%	4794
June	1st to 10th	Day	4 3 2 4 3 3 5% 5% 6% 7% 58%	2660
	11th to 20th	Day	4 3 1 4 4 3 3 3 5% 5% 66%	2660
	21st to end	Day	3 3 2 5% 4 5% 5% 5% 7% 6% 55%	2660
July	1st to 10th	Day	4 3 1 4 4 5% 6% 5% 6% 6% 57%	4308
	11th to 20th	Day	3 3 1 5% 6% 9% 10% 8% 12% 9% 35%	4110
	21st to end	Day	5% 4 2 6% 6% 6% 6% 6% 8% 9% 41%	4454
August	1st to 10th	Day	7% 5% 2 8% 7% 8% 8% 7% 11% 10% 28%	4092
	11th to 20th	Day	4 4 2 6% 5% 7% 7% 6% 7% 9% 42%	3874
	21st to end	Day	5% 5% 2 8% 6% 7% 7% 7% 8% 9% 36%	4180
September	1st to 10th	Day	8% 5% 3 6% 5% 5% 5% 5% 6% 6% 46%	2280
	11th to 20th	Day	7% 5% 2 7% 5% 5% 5% 4 5% 6% 49%	2275
	21st to end	Day	8% 3 2 3 3 3 4 3 4 6% 61%	2000
October	1st to 10th	Day	7% 4 1 3 3 2 3 3 3 5% 66%	3170
	11th to 20th	Day	14% 5% 2 5% 3 4 3 3 5% 5% 52%	3150
	21st to end	Day	5% 5% 2 4 2 2 2 2 3 5% 68%	3438
November	1st to 10th	Day	4 5% 1 3 3 2 3 2 4 6% 67%	1959
	11th to 20th	Day	4 4 1 3 2 2 3 3 4 5% 69%	1802
	21st to end	Day	6% 9% 2 3 3 2 2 3 4 5% 62%	1615
December	1st to 10th	Day	3 5% 1 3 2 2 2 2 5% 7% 68%	2620
	11th to 20th	Day	3 8% 2 4 3 4 4 3 4 7% 58%	3026
	21st to end	Day	3 9% 3 5% 3 3 4 3 4 5% 59%	4004
January	1st to 10th	Night	2 7% 4 10% 5% 4 4 3 4 6% 52%	5931
	11th to 20th	Night	2 7% 4 6% 3 3 3 2 5% 4 61%	5880
	21st to end	Night	3 10% 4 7% 3 3 3 3 4 5% 55%	6468
February	1st to 10th	Night	3 11% 2 5% 3 2 2 2 4 7% 59%	2600
	11th to 20th	Night	5% 10% 4 5% 3 3 3 3 4 6% 55%	2468
	21st to end	Night	4 12% 2 6% 3 2 2 3 4 6% 56%	1974
March	1st to 10th	Night	3 15% 3 6% 3 3 4 3 5% 6% 48%	3540
	11th to 20th	Night	5% 16% 3 7% 3 4 4 3 5% 7% 41%	3600
	21st to end	Night	6% 13% 3 7% 4 4 5% 3 5% 6% 43%	3882
April	1st to 10th	Night	7% 8% 2 4 3 3 4 3 5% 6% 55%	1900
	11th to 20th	Night	8% 8% 2 5% 3 3 3 3 5% 5% 56%	1877
	21st to end	Night	7% 7% 1 4 2 3 3 3 5% 7% 58%	1900
May	1st to 10th	Night	7% 6% 1 4 3 3 3 3 4 6% 61%	2991
	11th to 20th	Night	7% 6% 2 5% 3 3 4 4 5% 7% 55%	2834
	21st to end	Night	8% 4 1 3 2 2 3 3 3 5% 66%	2775
June	1st to 10th	Night	4 3 1 3 3 3 3 3 5% 7% 65%	1520
	11th to 20th	Night	6% 3 1 3 2 2 3 3 3 6% 69%	1520
	21st to end	Night	4 3 1 3 3 4 4 5% 7% 7% 58%	1520
July	1st to 10th	Night	5% 4 1 4 4 3 4 3 5% 6% 60%	2656
	11th to 20th	Night	3 3 1 5% 5% 5% 6% 6% 8% 11% 48%	2860
	21st to end	Night	5% 4 2 6% 4 5% 6% 4 8% 9% 45%	3109
August	1st to 10th	Night	6% 5% 3 7% 6% 6% 7% 6% 10% 11% 32%	2847
	11th to 20th	Night	4 4 2 6% 5% 5% 6% 6% 9% 11% 43%	2962
	21st to end	Night	6% 7% 3 7% 5% 6% 6% 4 7% 11% 38%	3487
September	1st to 10th	Night	6% 5% 2 5% 4 5% 5% 4 7% 9% 48%	1900
	11th to 20th	Night	9% 4 2 5% 4 3 4 3 5% 7% 54%	1902
	21st to end	Night	9% 3 1 4 2 2 3 2 3 5% 66%	2178
October	1st to 10th	Night	8% 3 1 3 2 2 2 2 3 4 71%	3800
	11th to 20th	Night	13% 5% 2 5% 3 3 3 2 4 5% 55%	3778
	21st to end	Night	8% 4 1 3 2 2 2 2 4 4 69%	4120
November	1st to 10th	Night	5% 5% 1 3 2 2 2 3 4 6% 66%	2340
	11th to 20th	Night	3 4 1 3 2 2 2 2 3 6% 72%	2575
	21st to end	Night	7% 9% 2 3 3 3 2 2 3 6% 62%	2783
December	1st to 10th	Night	3 5% 1 3 2 2 2 2 3 5% 72%	4570
	11th to 20th	Night	4 7% 2 4 3 3 3 3 4 6% 60%	5181
	21st to end	Night	5% 8% 3 5% 3 3 2 2 4 5% 60%	6974

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% 6% 11% 24% 21% 8%	4077
	11th to 20th	Day	22% 8% 7% 19% 21% 22%	4100
	21st to end	Day	29% 5% 7% 20% 27% 12%	4510
February	1st to 10th	Day	33% 4 13% 20% 19% 10%	1800
	11th to 20th	Day	37% 6% 7% 21% 23% 7%	1826
	21st to end	Day	37% 4 6% 14% 28% 10%	1653
March	1st to 10th	Day	32% 6% 14% 22% 20% 5%	3554
	11th to 20th	Day	42% 9% 9% 25% 12% 3	3600
	21st to end	Day	45% 8% 8% 15% 19% 4	3908
April	1st to 10th	Day	32% 6% 9% 20% 24% 9%	2280
	11th to 20th	Day	33% 6% 9% 19% 24% 8%	2254
	21st to end	Day	32% 7% 10% 22% 25% 4	2280
May	1st to 10th	Day	29% 6% 12% 15% 27% 11%	3976
	11th to 20th	Day	30% 10% 13% 19% 24% 4	4074
	21st to end	Day	22% 4 16% 12% 39% 7%	4794
June	1st to 10th	Day	21% 7% 10% 20% 27% 14%	2660
	11th to 20th	Day	20% 5% 6% 13% 29% 27%	2660
	21st to end	Day	24% 6% 11% 15% 23% 20%	2660
July	1st to 10th	Day	25% 8% 8% 10% 19% 30%	4242
	11th to 20th	Day	33% 12% 17% 23% 10% 4	4041
	21st to end	Day	33% 11% 18% 18% 12% 9%	4314
August	1st to 10th	Day	44% 12% 22% 9% 9% 6%	4078
	11th to 20th	Day	35% 9% 15% 13% 19% 9%	3913
	21st to end	Day	38% 10% 13% 17% 17% 4	4179
September	1st to 10th	Day	36% 8% 9% 15% 22% 11%	2280
	11th to 20th	Day	32% 9% 8% 17% 24% 11%	2275
	21st to end	Day	25% 6% 7% 17% 36% 9%	2000
October	1st to 10th	Day	21% 6% 4 18% 31% 20%	3170
	11th to 20th	Day	34% 5% 3 23% 27% 8%	3150
	21st to end	Day	21% 4 5% 26% 35% 10%	3438
November	1st to 10th	Day	20% 4 8% 30% 30% 9%	1959
	11th to 20th	Day	17% 5% 7% 26% 36% 10%	1802
	21st to end	Day	27% 3 5% 23% 29% 13%	1615
December	1st to 10th	Day	17% 4 8% 30% 31% 10%	2620
	11th to 20th	Day	26% 5% 8% 29% 27% 5%	3024
	21st to end	Day	27% 4 10% 24% 25% 11%	4004
January	1st to 10th	Night	32% 5% 8% 19% 25% 11%	5931
	11th to 20th	Night	24% 7% 6% 19% 25% 20%	5880
	21st to end	Night	31% 5% 5% 22% 23% 14%	6468
February	1st to 10th	Night	29% 3 10% 23% 24% 11%	2600
	11th to 20th	Night	31% 5% 8% 21% 26% 9%	2469
	21st to end	Night	31% 4 7% 15% 31% 13%	1974
March	1st to 10th	Night	34% 4 9% 22% 25% 6%	3540
	11th to 20th	Night	39% 6% 10% 24% 16% 5%	3600
	21st to end	Night	39% 8% 8% 19% 21% 5%	3882
April	1st to 10th	Night	30% 5% 9% 18% 28% 10%	1900
	11th to 20th	Night	31% 4 7% 19% 28% 11%	1877
	21st to end	Night	26% 4 9% 25% 29% 7%	1900
May	1st to 10th	Night	25% 4 8% 15% 37% 10%	2991
	11th to 20th	Night	26% 6% 11% 23% 28% 7%	2835
	21st to end	Night	22% 3 8% 16% 38% 14%	2775
June	1st to 10th	Night	19% 4 10% 18% 34% 17%	1520
	11th to 20th	Night	18% 3 6% 14% 26% 33%	1520
	21st to end	Night	22% 7% 7% 14% 27% 24%	1520
July	1st to 10th	Night	25% 4 9% 7% 13% 41%	2613
	11th to 20th	Night	26% 8% 14% 28% 16% 8%	2806
	21st to end	Night	30% 10% 18% 18% 12% 11%	3011
August	1st to 10th	Night	41% 8% 22% 9% 11% 8%	2838
	11th to 20th	Night	32% 8% 19% 10% 15% 16%	2989
	21st to end	Night	39% 6% 12% 19% 17% 7%	3487
September	1st to 10th	Night	31% 7% 11% 18% 21% 12%	1900
	11th to 20th	Night	30% 5% 9% 15% 21% 19%	1902
	21st to end	Night	23% 4 6% 18% 37% 13%	2178
October	1st to 10th	Night	18% 4 5% 13% 37% 23%	3800
	11th to 20th	Night	32% 3 4 21% 30% 10%	3778
	21st to end	Night	20% 4 4 19% 41% 13%	4120
November	1st to 10th	Night	20% 3 8% 26% 31% 11%	2340
	11th to 20th	Night	16% 4 5% 28% 36% 10%	2575
	21st to end	Night	27% 2 5% 23% 29% 14%	2783
December	1st to 10th	Night	17% 3 7% 29% 31% 13%	4570
	11th to 20th	Night	26% 4 7% 20% 32% 10%	5182
	21st to end	Night	28% 3 9% 19% 28% 13%	6974

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	15% 19% 36% 24% 5% 1	300
	11th to 20th	Day	17% 21% 36% 21% 4	300
	21st to end	Day	11% 16% 42% 23% 8% 1	330
February	1st to 10th	Day	17% 23% 39% 17% 4	300
	11th to 20th	Day	21% 24% 36% 17% 2	300
	21st to end	Day	21% 28% 32% 17% 3	252
March	1st to 10th	Day	22% 26% 29% 20% 2 1	500
	11th to 20th	Day	21% 27% 26% 20% 6% 1	500
	21st to end	Day	23% 30% 31% 13% 3	531
April	1st to 10th	Day	20% 28% 29% 15% 6% 1	460
	11th to 20th	Day	23% 34% 24% 13% 5% 1	452
	21st to end	Day	20% 28% 31% 16% 3 1	460
May	1st to 10th	Day	19% 26% 35% 15% 5% 1	463
	11th to 20th	Day	15% 20% 34% 22% 8% 1	488
	21st to end	Day	13% 19% 27% 25% 12% 3	716
June	1st to 10th	Day	7% 12% 27% 34% 17% 4	680
	11th to 20th	Day	8% 12% 33% 28% 14% 5%	680
	21st to end	Day	5% 13% 27% 33% 16% 6%	680
July	1st to 10th	Day	6% 7% 19% 38% 21% 8%	604
	11th to 20th	Day	8% 7% 15% 38% 25% 8%	484
	21st to end	Day	9% 6% 16% 38% 24% 7%	531
August	1st to 10th	Day	10% 5% 18% 38% 21% 7%	487
	11th to 20th	Day	7% 8% 23% 38% 16% 7%	477
	21st to end	Day	8% 5% 24% 36% 20% 7%	539
September	1st to 10th	Day	9% 8% 24% 33% 20% 7%	490
	11th to 20th	Day	7% 11% 33% 33% 12% 4	490
	21st to end	Day	13% 13% 30% 28% 9% 7%	400
October	1st to 10th	Day	15% 19% 19% 27% 16% 4	300
	11th to 20th	Day	16% 19% 23% 27% 13% 2	300
	21st to end	Day	15% 17% 28% 26% 12% 1	330
November	1st to 10th	Day	12% 23% 32% 25% 7%	300
	11th to 20th	Day	11% 22% 34% 24% 8% 1	300
	21st to end	Day	16% 14% 35% 25% 10%	300
December	1st to 10th	Day	13% 16% 36% 25% 8% 1	300
	11th to 20th	Day	9% 20% 38% 24% 7% 1	300
	21st to end	Day	21% 18% 34% 21% 5% 1	330
January	1st to 10th	Night	8% 9% 30% 36% 15% 3	825
	11th to 20th	Night	10% 9% 35% 30% 13% 3	800
	21st to end	Night	10% 8% 33% 34% 13% 3	880
February	1st to 10th	Night	9% 12% 35% 33% 9% 1	800
	11th to 20th	Night	11% 10% 37% 32% 9% 1	784
	21st to end	Night	11% 10% 39% 35% 6%	660
March	1st to 10th	Night	10% 13% 34% 30% 12% 2	800
	11th to 20th	Night	10% 10% 30% 32% 16% 2	800
	21st to end	Night	12% 12% 34% 31% 11% 1	857
April	1st to 10th	Night	14% 14% 33% 31% 8%	570
	11th to 20th	Night	15% 13% 27% 32% 13%	563
	21st to end	Night	11% 10% 37% 30% 11% 1	570
May	1st to 10th	Night	11% 10% 29% 35% 13% 1	570
	11th to 20th	Night	14% 6% 25% 36% 16% 2	561
	21st to end	Night	14% 8% 26% 33% 17% 2	617
June	1st to 10th	Night	5% 4 27% 38% 23% 2	570
	11th to 20th	Night	7% 6% 25% 39% 21% 3	570
	21st to end	Night	6% 3 22% 39% 28% 3	570
July	1st to 10th	Night	6% 3 14% 37% 36% 3	555
	11th to 20th	Night	7% 2 7% 38% 38% 9%	552
	21st to end	Night	7% 3 8% 34% 38% 9%	624
August	1st to 10th	Night	8% 2 7% 33% 43% 6%	567
	11th to 20th	Night	7% 3 12% 37% 36% 5%	564
	21st to end	Night	8% 4 10% 38% 33% 7%	627
September	1st to 10th	Night	8% 2 11% 42% 29% 7%	570
	11th to 20th	Night	10% 3 16% 40% 27% 4	572
	21st to end	Night	12% 3 19% 36% 25% 5%	760
October	1st to 10th	Night	16% 4 23% 38% 16% 3	760
	11th to 20th	Night	8% 6% 26% 38% 18% 4	760
	21st to end	Night	11% 6% 27% 33% 18% 4	836
November	1st to 10th	Night	9% 4 26% 40% 18% 3	780
	11th to 20th	Night	6% 9% 32% 37% 14% 3	975
	21st to end	Night	14% 8% 27% 31% 17% 3	1000
December	1st to 10th	Night	9% 9% 32% 38% 10% 2	1000
	11th to 20th	Night	13% 7% 33% 32% 14% 1	1000
	21st to end	Night	13% 12% 31% 34% 9% 1	1100

Page generated at 2025-03-24 07:04:28. Version ac07

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