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 2024-02-25.

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	6% 7% 3 5% 5% 3 5% 5% 5% 7% 51%	78606
	Night	6% 7% 3 5% 4 2 3 4 5% 6% 56%	80750
Transparency	Day	32% 7% 10% 19% 22% 10%	78329
	Night	29% 5% 9% 20% 25% 11%	80548
Seeing	Day	13% 17% 28% 27% 12% 3	14183
	Night	10% 7% 25% 35% 19% 3	24507

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	2 8% 3 6% 4 3 3 5% 6% 7% 53%	2836
	11th to 20th	Day	4 9% 3 5% 4 3 4 4 5% 7% 53%	2860
	21st to end	Day	4 12% 3 5% 5% 3 4 4 4 5% 51%	3146
February	1st to 10th	Day	2 12% 4 6% 5% 2 3 3 5% 4 54%	1710
	11th to 20th	Day	5% 12% 4 7% 5% 2 4 4 5% 6% 47%	1723
	21st to end	Day	3 13% 7% 6% 4 3 4 3 4 5% 48%	1522
March	1st to 10th	Day	6% 10% 3 6% 5% 2 4 4 5% 8% 45%	1980
	11th to 20th	Day	5% 11% 4 6% 4 3 4 4 6% 7% 47%	1980
	21st to end	Day	7% 10% 4 6% 5% 3 3 5% 5% 7% 45%	2182
April	1st to 10th	Day	5% 9% 3 6% 4 3 4 4 5% 6% 51%	2160
	11th to 20th	Day	5% 9% 2 5% 5% 3 5% 5% 6% 7% 47%	2131
	21st to end	Day	6% 7% 2 6% 5% 3 5% 6% 6% 7% 48%	2160
May	1st to 10th	Day	6% 7% 3 6% 6% 3 4 5% 6% 6% 48%	2258
	11th to 20th	Day	7% 7% 3 6% 6% 3 6% 6% 7% 7% 43%	2301
	21st to end	Day	7% 5% 2 5% 4 3 5% 5% 5% 7% 52%	2707
June	1st to 10th	Day	4 3 2 3 3 2 5% 6% 6% 8% 58%	2520
	11th to 20th	Day	4 3 2 3 4 2 3 4 4 5% 67%	2520
	21st to end	Day	3 3 2 4 4 3 5% 6% 7% 6% 57%	2520
July	1st to 10th	Day	5% 4 2 4 6% 5% 7% 7% 8% 8% 44%	2454
	11th to 20th	Day	5% 4 2 6% 8% 5% 8% 8% 8% 8% 37%	2340
	21st to end	Day	8% 6% 3 7% 8% 5% 7% 9% 8% 10% 27%	2545
August	1st to 10th	Day	8% 6% 3 6% 8% 4 7% 7% 8% 8% 35%	2328
	11th to 20th	Day	6% 5% 2 5% 7% 6% 7% 7% 7% 8% 39%	2210
	21st to end	Day	7% 5% 2 6% 7% 5% 7% 7% 6% 8% 39%	2376
September	1st to 10th	Day	9% 5% 3 5% 6% 4 6% 6% 6% 6% 45%	2160
	11th to 20th	Day	7% 5% 3 6% 5% 3 6% 6% 5% 6% 49%	2156
	21st to end	Day	9% 3 2 2 4 2 3 4 4 6% 60%	1895
October	1st to 10th	Day	13% 5% 2 4 4 2 3 4 4 6% 53%	1800
	11th to 20th	Day	7% 3 1 2 3 2 3 3 3 4 70%	1800
	21st to end	Day	5% 6% 1 4 2 1 3 3 3 5% 66%	1980
November	1st to 10th	Day	5% 4 1 2 2 2 3 3 3 6% 69%	1859
	11th to 20th	Day	4 4 1 2 2 2 3 4 4 5% 69%	1712
	21st to end	Day	6% 9% 2 2 3 1 3 3 4 5% 62%	1535
December	1st to 10th	Day	6% 9% 2 4 3 2 3 3 4 6% 57%	1520
	11th to 20th	Day	5% 11% 3 4 4 3 4 4 4 8% 49%	1926
	21st to end	Day	4 10% 3 5% 3 2 4 4 4 5% 55%	2794
January	1st to 10th	Night	2 8% 4 9% 6% 3 4 4 4 6% 50%	4147
	11th to 20th	Night	3 9% 6% 7% 4 3 4 4 4 4 53%	4110
	21st to end	Night	4 12% 4 5% 4 2 3 3 4 5% 53%	4521
February	1st to 10th	Night	3 12% 3 5% 3 2 3 2 4 6% 59%	2470
	11th to 20th	Night	5% 9% 4 5% 3 2 3 4 4 6% 56%	2342
	21st to end	Night	3 13% 2 6% 3 2 2 3 4 6% 55%	1826
March	1st to 10th	Night	6% 8% 3 4 4 2 3 4 4 7% 55%	1980
	11th to 20th	Night	5% 9% 4 6% 3 3 3 3 4 8% 52%	1980
	21st to end	Night	6% 9% 3 6% 4 2 4 4 5% 7% 52%	2174
April	1st to 10th	Night	7% 8% 2 4 3 2 4 3 5% 6% 55%	1800
	11th to 20th	Night	8% 7% 3 4 4 2 3 4 5% 5% 55%	1777
	21st to end	Night	7% 7% 2 4 2 2 4 3 4 7% 58%	1800
May	1st to 10th	Night	8% 6% 2 4 3 2 4 4 4 6% 57%	1699
	11th to 20th	Night	9% 7% 3 5% 4 2 4 4 5% 5% 53%	1594
	21st to end	Night	10% 5% 2 4 3 2 4 4 4 6% 56%	1565
June	1st to 10th	Night	4 3 1 3 3 2 3 4 5% 7% 65%	1440
	11th to 20th	Night	5% 3 1 3 3 1 3 3 3 6% 69%	1440
	21st to end	Night	4 3 1 2 3 3 4 5% 7% 7% 60%	1440
July	1st to 10th	Night	4 4 2 5% 6% 4 5% 7% 7% 10% 46%	1500
	11th to 20th	Night	5% 3 2 5% 6% 3 6% 6% 7% 9% 47%	1620
	21st to end	Night	7% 4 3 7% 6% 5% 7% 7% 10% 12% 33%	1773
August	1st to 10th	Night	6% 4 2 5% 6% 4 5% 6% 7% 9% 45%	1611
	11th to 20th	Night	6% 4 2 4 5% 3 5% 6% 8% 9% 47%	1688
	21st to end	Night	6% 5% 2 5% 5% 3 5% 5% 7% 10% 46%	1980
September	1st to 10th	Night	6% 5% 2 4 5% 3 6% 6% 7% 9% 47%	1800
	11th to 20th	Night	9% 4 2 4 5% 2 4 4 5% 7% 54%	1801
	21st to end	Night	10% 3 1 3 3 1 3 3 3 5% 66%	2063
October	1st to 10th	Night	14% 4 2 4 3 2 2 3 4 5% 56%	2160
	11th to 20th	Night	6% 3 1 2 2 1 2 3 3 4 73%	2160
	21st to end	Night	7% 4 1 3 2 1 2 2 4 5% 68%	2376
November	1st to 10th	Night	5% 4 1 2 2 1 2 3 4 6% 68%	2220
	11th to 20th	Night	3 4 1 3 2 2 2 3 3 6% 71%	2446
	21st to end	Night	7% 7% 2 3 3 2 3 2 3 6% 62%	2643
December	1st to 10th	Night	5% 8% 2 4 4 2 3 3 4 6% 60%	2660
	11th to 20th	Night	6% 9% 3 4 4 3 4 4 4 7% 51%	3271
	21st to end	Night	6% 9% 4 6% 3 2 2 3 3 6% 56%	4873

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	29% 6% 14% 23% 20% 8%	2837
	11th to 20th	Day	29% 8% 10% 28% 21% 4	2860
	21st to end	Day	34% 6% 10% 23% 24% 4	3146
February	1st to 10th	Day	34% 4 13% 20% 19% 9%	1710
	11th to 20th	Day	37% 5% 6% 22% 23% 6%	1732
	21st to end	Day	39% 4 7% 14% 27% 9%	1522
March	1st to 10th	Day	36% 5% 8% 24% 21% 6%	1980
	11th to 20th	Day	36% 7% 8% 26% 19% 5%	1980
	21st to end	Day	38% 6% 8% 23% 20% 5%	2182
April	1st to 10th	Day	33% 6% 9% 20% 22% 10%	2160
	11th to 20th	Day	34% 7% 9% 19% 23% 8%	2134
	21st to end	Day	33% 6% 10% 22% 24% 4	2160
May	1st to 10th	Day	34% 8% 9% 21% 24% 5%	2258
	11th to 20th	Day	37% 8% 10% 22% 20% 4	2304
	21st to end	Day	31% 6% 9% 16% 28% 10%	2707
June	1st to 10th	Day	22% 8% 10% 20% 26% 15%	2520
	11th to 20th	Day	19% 5% 6% 13% 29% 28%	2520
	21st to end	Day	23% 6% 11% 14% 24% 21%	2520
July	1st to 10th	Day	34% 10% 13% 12% 14% 17%	2388
	11th to 20th	Day	36% 13% 18% 14% 11% 8%	2271
	21st to end	Day	44% 15% 20% 13% 6% 1	2404
August	1st to 10th	Day	41% 14% 13% 11% 12% 10%	2313
	11th to 20th	Day	38% 10% 14% 12% 15% 10%	2210
	21st to end	Day	37% 10% 14% 17% 17% 6%	2376
September	1st to 10th	Day	36% 8% 9% 13% 21% 11%	2160
	11th to 20th	Day	32% 9% 8% 17% 23% 11%	2156
	21st to end	Day	25% 6% 8% 17% 36% 9%	1895
October	1st to 10th	Day	33% 7% 6% 19% 23% 13%	1800
	11th to 20th	Day	20% 4 3 21% 38% 14%	1800
	21st to end	Day	22% 4 8% 26% 31% 9%	1980
November	1st to 10th	Day	18% 4 8% 30% 31% 9%	1859
	11th to 20th	Day	18% 5% 7% 26% 35% 8%	1712
	21st to end	Day	27% 3 5% 24% 28% 13%	1535
December	1st to 10th	Day	28% 5% 13% 24% 21% 8%	1520
	11th to 20th	Day	35% 7% 8% 22% 21% 6%	1924
	21st to end	Day	30% 4 11% 17% 23% 14%	2794
January	1st to 10th	Night	33% 6% 10% 22% 23% 6%	4147
	11th to 20th	Night	31% 9% 8% 22% 24% 5%	4110
	21st to end	Night	32% 5% 8% 27% 23% 6%	4521
February	1st to 10th	Night	30% 3 10% 23% 23% 10%	2470
	11th to 20th	Night	31% 5% 8% 22% 26% 9%	2343
	21st to end	Night	32% 4 7% 16% 31% 11%	1826
March	1st to 10th	Night	31% 4 6% 24% 27% 8%	1980
	11th to 20th	Night	31% 5% 8% 26% 23% 8%	1980
	21st to end	Night	33% 5% 8% 22% 25% 7%	2174
April	1st to 10th	Night	30% 6% 9% 18% 27% 11%	1800
	11th to 20th	Night	31% 4 7% 19% 27% 11%	1777
	21st to end	Night	26% 4 9% 25% 29% 7%	1800
May	1st to 10th	Night	29% 5% 6% 22% 30% 8%	1699
	11th to 20th	Night	32% 5% 12% 21% 25% 5%	1595
	21st to end	Night	29% 5% 9% 18% 28% 11%	1565
June	1st to 10th	Night	19% 4 10% 18% 33% 17%	1440
	11th to 20th	Night	18% 3 7% 14% 26% 33%	1440
	21st to end	Night	20% 7% 7% 14% 27% 25%	1440
July	1st to 10th	Night	32% 7% 15% 12% 15% 20%	1457
	11th to 20th	Night	31% 10% 16% 17% 13% 13%	1566
	21st to end	Night	38% 15% 22% 14% 7% 3	1674
August	1st to 10th	Night	33% 10% 16% 14% 13% 15%	1602
	11th to 20th	Night	30% 8% 17% 14% 18% 13%	1688
	21st to end	Night	32% 8% 14% 20% 19% 8%	1980
September	1st to 10th	Night	32% 7% 12% 17% 20% 12%	1800
	11th to 20th	Night	31% 6% 9% 15% 20% 19%	1801
	21st to end	Night	23% 4 6% 18% 36% 13%	2063
October	1st to 10th	Night	30% 6% 8% 16% 23% 17%	2160
	11th to 20th	Night	17% 3 5% 19% 39% 17%	2160
	21st to end	Night	20% 4 6% 24% 33% 13%	2376
November	1st to 10th	Night	19% 3 8% 27% 32% 11%	2220
	11th to 20th	Night	16% 4 6% 29% 36% 9%	2446
	21st to end	Night	27% 2 6% 23% 29% 13%	2643
December	1st to 10th	Night	27% 5% 12% 24% 24% 9%	2660
	11th to 20th	Night	34% 5% 10% 18% 24% 9%	3272
	21st to end	Night	33% 3 8% 17% 23% 16%	4873

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% 35% 25% 6% 1	270
	11th to 20th	Day	17% 22% 34% 22% 5%	270
	21st to end	Day	10% 15% 41% 25% 8% 1	297
February	1st to 10th	Day	15% 22% 40% 19% 4	270
	11th to 20th	Day	19% 23% 37% 19% 2	270
	21st to end	Day	21% 28% 33% 17% 2	212
March	1st to 10th	Day	21% 25% 31% 21% 2	420
	11th to 20th	Day	19% 25% 28% 21% 6% 1	420
	21st to end	Day	23% 30% 31% 12% 3	462
April	1st to 10th	Day	20% 29% 29% 15% 6% 1	420
	11th to 20th	Day	24% 34% 23% 12% 5% 1	412
	21st to end	Day	21% 29% 30% 16% 3 1	420
May	1st to 10th	Day	16% 27% 35% 16% 6% 1	423
	11th to 20th	Day	16% 21% 33% 21% 8% 2	448
	21st to end	Day	13% 20% 27% 25% 12% 3	662
June	1st to 10th	Day	7% 12% 27% 33% 18% 4	630
	11th to 20th	Day	7% 11% 33% 29% 15% 5%	630
	21st to end	Day	4 13% 26% 34% 17% 6%	630
July	1st to 10th	Day	6% 6% 17% 41% 22% 9%	558
	11th to 20th	Day	8% 7% 15% 37% 25% 8%	444
	21st to end	Day	9% 5% 15% 38% 25% 8%	487
August	1st to 10th	Day	11% 6% 19% 37% 20% 7%	447
	11th to 20th	Day	8% 9% 23% 37% 17% 7%	437
	21st to end	Day	7% 5% 22% 37% 21% 7%	495
September	1st to 10th	Day	9% 8% 23% 34% 20% 6%	450
	11th to 20th	Day	6% 10% 32% 35% 12% 4	450
	21st to end	Day	13% 14% 28% 28% 9% 7%	365
October	1st to 10th	Day	16% 21% 18% 26% 16% 4	270
	11th to 20th	Day	13% 20% 23% 27% 14% 2	270
	21st to end	Day	16% 16% 27% 26% 13% 1	297
November	1st to 10th	Day	13% 22% 31% 26% 8%	270
	11th to 20th	Day	9% 23% 33% 26% 9% 1	270
	21st to end	Day	16% 13% 35% 26% 10%	270
December	1st to 10th	Day	14% 17% 36% 24% 8% 1	270
	11th to 20th	Day	9% 20% 38% 24% 7% 1	270
	21st to end	Day	20% 18% 35% 22% 5% 1	297
January	1st to 10th	Night	8% 8% 29% 36% 15% 3	784
	11th to 20th	Night	11% 8% 34% 30% 14% 3	760
	21st to end	Night	10% 7% 31% 36% 13% 3	836
February	1st to 10th	Night	9% 11% 34% 35% 10% 1	760
	11th to 20th	Night	11% 8% 37% 33% 9% 1	744
	21st to end	Night	11% 8% 38% 37% 6%	610
March	1st to 10th	Night	11% 13% 33% 30% 12% 2	720
	11th to 20th	Night	9% 9% 29% 33% 18% 2	720
	21st to end	Night	12% 11% 33% 31% 12% 1	788
April	1st to 10th	Night	13% 14% 33% 32% 9%	540
	11th to 20th	Night	15% 13% 25% 34% 13%	533
	21st to end	Night	12% 9% 36% 30% 11% 1	540
May	1st to 10th	Night	11% 9% 29% 36% 14% 1	540
	11th to 20th	Night	14% 7% 24% 36% 17% 3	531
	21st to end	Night	15% 7% 26% 33% 17% 2	584
June	1st to 10th	Night	6% 4 25% 38% 24% 3	540
	11th to 20th	Night	6% 6% 23% 40% 22% 3	540
	21st to end	Night	5% 2 21% 39% 29% 3	540
July	1st to 10th	Night	6% 1 13% 39% 38% 3	525
	11th to 20th	Night	7% 2 7% 37% 38% 10%	522
	21st to end	Night	7% 3 6% 34% 40% 10%	591
August	1st to 10th	Night	8% 2 7% 32% 44% 7%	537
	11th to 20th	Night	8% 3 10% 36% 37% 6%	534
	21st to end	Night	8% 4 8% 38% 35% 7%	594
September	1st to 10th	Night	8% 2 11% 41% 31% 7%	540
	11th to 20th	Night	10% 3 14% 41% 28% 4	541
	21st to end	Night	12% 3 17% 36% 26% 5%	720
October	1st to 10th	Night	17% 5% 22% 37% 17% 3	720
	11th to 20th	Night	7% 6% 26% 38% 19% 4	720
	21st to end	Night	11% 6% 26% 33% 19% 5%	792
November	1st to 10th	Night	9% 4 24% 41% 19% 3	740
	11th to 20th	Night	6% 7% 31% 38% 15% 4	926
	21st to end	Night	13% 8% 26% 31% 18% 3	950
December	1st to 10th	Night	10% 8% 32% 37% 11% 2	950
	11th to 20th	Night	13% 7% 31% 33% 14% 1	950
	21st to end	Night	13% 10% 32% 35% 9% 1	1045

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