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 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	4 6% 2 6% 4 4 5% 4 6% 7% 52%	146792
	Night	5% 7% 2 5% 3 3 4 3 5% 6% 56%	143790
Transparency	Day	29% 7% 10% 20% 24% 11%	141706
	Night	28% 5% 8% 19% 27% 13%	139884
Seeing	Day	14% 18% 29% 26% 11% 3	17554
	Night	10% 8% 28% 34% 17% 3	27688

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% 4 4 4 4 5% 6% 51%	5296
	11th to 20th	Day	2 5% 2 4 2 3 3 3 4 5% 68%	5340
	21st to end	Day	2 10% 3 5% 4 3 4 3 4 4 59%	5844
February	1st to 10th	Day	1 11% 4 7% 4 3 3 3 5% 5% 54%	1890
	11th to 20th	Day	5% 12% 3 8% 5% 3 4 4 5% 6% 46%	1910
	21st to end	Day	3 13% 6% 7% 3 3 3 2 4 4 52%	1733
March	1st to 10th	Day	3 11% 4 7% 5% 4 4 4 5% 7% 46%	5064
	11th to 20th	Day	3 15% 4 9% 6% 6% 5% 3 5% 6% 38%	5110
	21st to end	Day	4 12% 4 9% 5% 5% 5% 4 5% 7% 42%	5623
April	1st to 10th	Day	5% 9% 2 7% 4 4 4 3 5% 6% 51%	2520
	11th to 20th	Day	4 9% 2 6% 5% 4 5% 4 6% 7% 47%	2491
	21st to end	Day	6% 7% 2 7% 4 5% 4 5% 6% 7% 48%	2520
May	1st to 10th	Day	6% 7% 2 7% 5% 5% 5% 4 6% 7% 45%	7375
	11th to 20th	Day	4 5% 2 5% 5% 5% 6% 5% 7% 7% 50%	7596
	21st to end	Day	4 4 1 5% 4 4 5% 4 6% 7% 57%	8967
June	1st to 10th	Day	4 3 1 4 3 3 5% 5% 7% 7% 57%	2940
	11th to 20th	Day	4 3 1 4 3 3 3 3 5% 5% 67%	2940
	21st to end	Day	3 3 2 5% 3 5% 5% 5% 7% 6% 57%	2940
July	1st to 10th	Day	3 2 1 4 4 5% 6% 4 6% 6% 60%	6297
	11th to 20th	Day	2 3 1 5% 6% 9% 10% 8% 11% 9% 36%	6010
	21st to end	Day	4 3 2 6% 6% 6% 6% 6% 8% 9% 45%	6532
August	1st to 10th	Day	5% 3 2 6% 6% 6% 6% 6% 9% 10% 41%	5779
	11th to 20th	Day	3 4 2 5% 5% 6% 7% 5% 7% 9% 47%	5579
	21st to end	Day	5% 4 2 7% 6% 7% 8% 7% 9% 9% 34%	5984
September	1st to 10th	Day	8% 5% 3 6% 5% 5% 5% 5% 6% 6% 46%	2400
	11th to 20th	Day	7% 5% 2 7% 5% 5% 5% 4 5% 6% 50%	2394
	21st to end	Day	8% 4 2 4 3 3 4 3 4 6% 60%	2105
October	1st to 10th	Day	7% 4 1 3 3 2 3 3 3 5% 66%	3270
	11th to 20th	Day	15% 5% 2 5% 3 4 3 3 5% 5% 52%	3250
	21st to end	Day	5% 5% 2 4 2 2 2 2 3 5% 68%	3548
November	1st to 10th	Day	4 5% 1 3 3 2 3 2 4 6% 67%	2059
	11th to 20th	Day	4 5% 1 3 2 2 3 3 4 5% 68%	1892
	21st to end	Day	6% 9% 2 3 3 2 2 3 4 5% 62%	1696
December	1st to 10th	Day	3 6% 1 3 2 2 2 2 5% 7% 68%	2700
	11th to 20th	Day	3 7% 2 4 3 4 4 3 4 7% 59%	3106
	21st to end	Day	3 9% 3 5% 3 3 4 3 5% 5% 59%	4092
January	1st to 10th	Night	2 8% 4 11% 5% 5% 5% 4 5% 6% 47%	7681
	11th to 20th	Night	2 5% 3 5% 2 2 3 2 4 5% 68%	7650
	21st to end	Night	3 10% 4 6% 3 3 2 2 4 5% 59%	8370
February	1st to 10th	Night	2 11% 2 5% 3 2 2 2 4 6% 60%	2730
	11th to 20th	Night	5% 10% 4 6% 3 3 3 3 4 6% 53%	2595
	21st to end	Night	3 12% 2 6% 3 2 2 3 4 6% 57%	2070
March	1st to 10th	Night	3 14% 3 7% 4 4 4 3 4 5% 49%	5050
	11th to 20th	Night	4 14% 3 6% 3 4 4 3 6% 7% 45%	5110
	21st to end	Night	5% 10% 2 6% 4 4 5% 3 5% 6% 49%	5593
April	1st to 10th	Night	7% 8% 2 5% 3 3 4 3 5% 5% 55%	2100
	11th to 20th	Night	7% 8% 2 5% 3 4 3 3 5% 5% 54%	2077
	21st to end	Night	6% 7% 1 4 2 3 3 2 5% 6% 58%	2100
May	1st to 10th	Night	7% 7% 2 5% 4 4 4 3 4 7% 54%	5556
	11th to 20th	Night	6% 6% 2 5% 3 2 3 3 4 6% 60%	5296
	21st to end	Night	7% 4 1 4 3 3 3 3 3 5% 64%	5222
June	1st to 10th	Night	3 3 1 3 3 3 3 3 5% 8% 64%	1680
	11th to 20th	Night	5% 3 1 3 2 2 3 3 3 5% 70%	1680
	21st to end	Night	4 3 1 3 3 4 4 5% 7% 7% 60%	1680
July	1st to 10th	Night	4 3 1 5% 3 4 4 3 5% 6% 62%	3895
	11th to 20th	Night	2 2 1 5% 5% 5% 7% 6% 8% 12% 47%	4190
	21st to end	Night	4 4 2 7% 5% 6% 6% 5% 9% 9% 44%	4562
August	1st to 10th	Night	5% 4 2 6% 5% 5% 6% 5% 9% 10% 43%	4033
	11th to 20th	Night	3 3 2 6% 4 5% 6% 5% 8% 10% 48%	4267
	21st to end	Night	8% 7% 3 8% 6% 7% 7% 5% 7% 9% 35%	4993
September	1st to 10th	Night	6% 5% 2 5% 5% 5% 5% 5% 7% 8% 48%	2000
	11th to 20th	Night	9% 4 2 5% 4 3 4 3 5% 7% 54%	2002
	21st to end	Night	9% 3 1 4 2 2 3 2 3 5% 65%	2293
October	1st to 10th	Night	8% 3 1 3 2 2 2 2 3 4 71%	3920
	11th to 20th	Night	15% 5% 2 5% 3 3 3 2 4 5% 54%	3898
	21st to end	Night	8% 4 1 3 1 2 2 2 4 5% 69%	4252
November	1st to 10th	Night	5% 5% 1 3 2 2 2 3 4 6% 67%	2460
	11th to 20th	Night	3 5% 1 3 2 2 2 2 3 6% 71%	2704
	21st to end	Night	6% 8% 2 3 3 3 2 2 3 6% 61%	2922
December	1st to 10th	Night	3 5% 1 3 2 2 2 2 3 5% 72%	4710
	11th to 20th	Night	3 7% 2 4 3 3 3 3 4 6% 61%	5321
	21st to end	Night	5% 8% 3 5% 3 3 2 2 4 5% 60%	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	32% 5% 10% 27% 19% 6%	5299
	11th to 20th	Day	17% 6% 6% 21% 27% 23%	5340
	21st to end	Day	28% 4 5% 20% 27% 15%	5844
February	1st to 10th	Day	32% 4 13% 19% 22% 10%	1890
	11th to 20th	Day	38% 5% 7% 21% 23% 7%	1919
	21st to end	Day	36% 4 7% 15% 29% 10%	1733
March	1st to 10th	Day	31% 7% 10% 18% 22% 11%	5064
	11th to 20th	Day	42% 9% 6% 22% 15% 5%	5110
	21st to end	Day	38% 8% 10% 22% 18% 3	5623
April	1st to 10th	Day	33% 6% 9% 20% 23% 9%	2520
	11th to 20th	Day	33% 7% 9% 19% 25% 8%	2494
	21st to end	Day	31% 7% 9% 22% 26% 4	2520
May	1st to 10th	Day	34% 7% 11% 21% 20% 7%	7375
	11th to 20th	Day	25% 10% 8% 23% 30% 4	7599
	21st to end	Day	21% 5% 10% 19% 37% 7%	8968
June	1st to 10th	Day	22% 7% 10% 21% 26% 14%	2940
	11th to 20th	Day	19% 5% 6% 13% 30% 28%	2940
	21st to end	Day	23% 6% 11% 14% 24% 22%	2940
July	1st to 10th	Day	23% 7% 7% 9% 19% 34%	6232
	11th to 20th	Day	33% 11% 19% 20% 10% 6%	5941
	21st to end	Day	31% 9% 19% 17% 16% 7%	6348
August	1st to 10th	Day	42% 11% 21% 9% 9% 6%	4208
	11th to 20th	Day	34% 9% 15% 14% 19% 9%	4038
	21st to end	Day	38% 10% 14% 17% 17% 4	4311
September	1st to 10th	Day	36% 8% 9% 16% 21% 10%	2400
	11th to 20th	Day	32% 8% 7% 17% 24% 11%	2394
	21st to end	Day	26% 6% 7% 17% 35% 9%	2105
October	1st to 10th	Day	21% 6% 4 18% 31% 19%	3270
	11th to 20th	Day	34% 5% 3 23% 28% 8%	3250
	21st to end	Day	20% 4 5% 26% 35% 10%	3548
November	1st to 10th	Day	19% 4 8% 31% 30% 8%	2059
	11th to 20th	Day	18% 5% 7% 27% 34% 9%	1892
	21st to end	Day	27% 3 6% 24% 28% 13%	1696
December	1st to 10th	Day	17% 4 8% 30% 31% 10%	2700
	11th to 20th	Day	25% 5% 8% 29% 28% 5%	3104
	21st to end	Day	27% 4 10% 23% 25% 11%	4092
January	1st to 10th	Night	36% 5% 8% 21% 21% 9%	7682
	11th to 20th	Night	19% 6% 5% 20% 31% 20%	7650
	21st to end	Night	28% 4 5% 19% 25% 18%	8370
February	1st to 10th	Night	27% 3 10% 23% 25% 12%	2730
	11th to 20th	Night	33% 5% 8% 20% 26% 9%	2596
	21st to end	Night	30% 3 7% 16% 31% 13%	2070
March	1st to 10th	Night	35% 4 6% 17% 27% 10%	5050
	11th to 20th	Night	35% 6% 7% 20% 24% 9%	5110
	21st to end	Night	34% 7% 7% 28% 21% 4	5593
April	1st to 10th	Night	30% 6% 8% 18% 28% 10%	2100
	11th to 20th	Night	32% 4 7% 18% 28% 11%	2077
	21st to end	Night	26% 4 8% 24% 31% 7%	2100
May	1st to 10th	Night	30% 4 9% 21% 27% 8%	5554
	11th to 20th	Night	24% 4 7% 20% 35% 9%	5297
	21st to end	Night	23% 3 6% 17% 39% 12%	5223
June	1st to 10th	Night	19% 4 9% 18% 33% 16%	1680
	11th to 20th	Night	18% 2 6% 13% 26% 34%	1680
	21st to end	Night	22% 6% 7% 13% 26% 27%	1680
July	1st to 10th	Night	24% 4 9% 7% 12% 44%	3852
	11th to 20th	Night	26% 7% 16% 27% 13% 11%	4136
	21st to end	Night	32% 9% 18% 17% 15% 9%	4434
August	1st to 10th	Night	40% 8% 22% 9% 11% 9%	2928
	11th to 20th	Night	32% 8% 19% 10% 15% 15%	3084
	21st to end	Night	40% 7% 12% 19% 16% 6%	3597
September	1st to 10th	Night	31% 7% 12% 18% 21% 11%	2000
	11th to 20th	Night	31% 5% 8% 15% 22% 19%	2002
	21st to end	Night	23% 4 6% 18% 37% 13%	2293
October	1st to 10th	Night	19% 3 5% 13% 37% 23%	3920
	11th to 20th	Night	33% 3 4 20% 30% 10%	3898
	21st to end	Night	19% 4 4 19% 41% 13%	4252
November	1st to 10th	Night	19% 3 8% 27% 32% 10%	2460
	11th to 20th	Night	17% 4 5% 29% 35% 10%	2704
	21st to end	Night	27% 2 6% 24% 29% 13%	2922
December	1st to 10th	Night	17% 3 7% 29% 31% 12%	4710
	11th to 20th	Night	25% 4 7% 20% 32% 11%	5322
	21st to end	Night	28% 3 9% 19% 28% 13%	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	16% 19% 37% 23% 5% 1	330
	11th to 20th	Day	18% 21% 37% 20% 5%	330
	21st to end	Day	11% 17% 42% 22% 7% 1	363
February	1st to 10th	Day	16% 24% 38% 18% 4	330
	11th to 20th	Day	24% 24% 35% 16% 2	330
	21st to end	Day	21% 29% 32% 16% 3	276
March	1st to 10th	Day	21% 27% 29% 20% 2 1	540
	11th to 20th	Day	22% 27% 26% 19% 5% 1	540
	21st to end	Day	22% 30% 31% 13% 3 1	594
April	1st to 10th	Day	21% 27% 29% 15% 6% 1	540
	11th to 20th	Day	25% 33% 23% 12% 5% 1	532
	21st to end	Day	23% 29% 29% 15% 3 1	540
May	1st to 10th	Day	20% 26% 34% 16% 5% 1	543
	11th to 20th	Day	19% 20% 33% 20% 7% 1	568
	21st to end	Day	14% 20% 28% 26% 10% 3	824
June	1st to 10th	Day	8% 12% 28% 32% 16% 3	780
	11th to 20th	Day	9% 13% 35% 27% 12% 4	780
	21st to end	Day	6% 16% 28% 31% 14% 5%	780
July	1st to 10th	Day	6% 8% 23% 37% 19% 7%	696
	11th to 20th	Day	7% 8% 15% 40% 23% 7%	564
	21st to end	Day	7% 6% 17% 39% 23% 7%	616
August	1st to 10th	Day	10% 7% 19% 37% 20% 7%	527
	11th to 20th	Day	7% 8% 24% 39% 15% 7%	517
	21st to end	Day	8% 6% 24% 37% 19% 7%	583
September	1st to 10th	Day	8% 7% 26% 34% 19% 6%	530
	11th to 20th	Day	8% 12% 32% 32% 12% 4	530
	21st to end	Day	13% 13% 31% 27% 9% 7%	435
October	1st to 10th	Day	15% 20% 20% 26% 15% 4	330
	11th to 20th	Day	20% 19% 22% 25% 12% 2	330
	21st to end	Day	15% 17% 29% 26% 11% 1	363
November	1st to 10th	Day	11% 24% 33% 25% 7%	330
	11th to 20th	Day	10% 23% 35% 24% 8% 1	330
	21st to end	Day	16% 15% 35% 23% 9%	330
December	1st to 10th	Day	13% 18% 38% 23% 8% 1	330
	11th to 20th	Day	10% 21% 38% 24% 7% 1	330
	21st to end	Day	21% 19% 34% 21% 4 1	363
January	1st to 10th	Night	8% 9% 31% 35% 14% 3	866
	11th to 20th	Night	10% 9% 35% 30% 13% 3	840
	21st to end	Night	10% 9% 34% 33% 12% 2	924
February	1st to 10th	Night	9% 12% 36% 33% 9% 1	840
	11th to 20th	Night	12% 10% 38% 30% 8% 1	824
	21st to end	Night	11% 12% 38% 34% 6%	692
March	1st to 10th	Night	10% 13% 35% 29% 12% 2	840
	11th to 20th	Night	10% 11% 31% 31% 15% 2	840
	21st to end	Night	11% 12% 36% 30% 10% 1	919
April	1st to 10th	Night	14% 15% 33% 30% 8%	630
	11th to 20th	Night	15% 14% 28% 31% 11%	623
	21st to end	Night	11% 10% 37% 30% 10% 1	630
May	1st to 10th	Night	11% 10% 32% 35% 12% 1	630
	11th to 20th	Night	14% 8% 27% 34% 15% 2	621
	21st to end	Night	14% 8% 30% 31% 15% 2	683
June	1st to 10th	Night	5% 5% 28% 39% 21% 2	630
	11th to 20th	Night	6% 7% 27% 38% 19% 2	630
	21st to end	Night	6% 4 26% 37% 25% 2	630
July	1st to 10th	Night	6% 3 17% 39% 33% 3	615
	11th to 20th	Night	7% 2 8% 39% 36% 8%	612
	21st to end	Night	7% 3 10% 35% 37% 8%	687
August	1st to 10th	Night	8% 3 10% 33% 41% 6%	597
	11th to 20th	Night	7% 3 12% 38% 34% 5%	594
	21st to end	Night	8% 5% 11% 37% 32% 7%	660
September	1st to 10th	Night	7% 2 14% 42% 28% 7%	600
	11th to 20th	Night	11% 3 18% 39% 26% 3	602
	21st to end	Night	11% 4 20% 36% 24% 5%	800
October	1st to 10th	Night	16% 4 25% 37% 15% 3	800
	11th to 20th	Night	10% 6% 27% 37% 17% 4	800
	21st to end	Night	11% 7% 28% 33% 17% 4	880
November	1st to 10th	Night	9% 5% 27% 39% 18% 3	820
	11th to 20th	Night	7% 8% 33% 36% 13% 3	1024
	21st to end	Night	13% 9% 28% 30% 16% 3	1050
December	1st to 10th	Night	9% 9% 33% 37% 10% 2	1050
	11th to 20th	Night	13% 8% 33% 32% 13% 1	1050
	21st to end	Night	13% 11% 33% 33% 8% 1	1155

Page generated at 2026-07-28 01:25:24. Version ac07

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