Lakeside Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lakeside Site clear sky chart from 2005-11-06 to 2024-01-12.

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% 6% 3 6% 6% 3 5% 5% 6% 7% 50%	75327
	Night	6% 6% 3 6% 6% 3 5% 5% 5% 7% 48%	74331
Transparency	Day	33% 3 9% 21% 21% 13%	75045
	Night	35% 3 10% 23% 20% 10%	74134
Seeing	Day	7% 8% 22% 33% 22% 8%	13711
	Night	9% 5% 15% 39% 28% 5%	23443

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	9% 10% 5% 11% 10% 6% 5% 4 6% 6% 27%	1696
	11th to 20th	Day	6% 11% 5% 10% 10% 6% 5% 6% 6% 8% 27%	1629
	21st to end	Day	8% 12% 6% 13% 11% 5% 5% 4 5% 7% 23%	1782
February	1st to 10th	Day	5% 8% 5% 12% 9% 5% 7% 7% 5% 8% 30%	1620
	11th to 20th	Day	6% 9% 4 8% 7% 4 5% 5% 6% 10% 37%	1692
	21st to end	Day	5% 10% 5% 7% 8% 4 5% 5% 6% 9% 37%	1480
March	1st to 10th	Day	6% 9% 3 7% 6% 3 5% 4 6% 9% 41%	1872
	11th to 20th	Day	4 7% 4 7% 7% 4 7% 6% 7% 10% 38%	1980
	21st to end	Day	8% 8% 4 7% 6% 3 6% 5% 6% 9% 37%	2178
April	1st to 10th	Day	7% 7% 3 6% 6% 4 6% 5% 6% 8% 44%	2020
	11th to 20th	Day	6% 8% 4 5% 6% 3 4 5% 5% 8% 49%	2276
	21st to end	Day	7% 6% 2 5% 5% 3 4 4 4 8% 51%	2340
May	1st to 10th	Day	5% 5% 2 5% 6% 4 5% 5% 7% 7% 49%	2340
	11th to 20th	Day	6% 4 2 6% 6% 3 5% 5% 7% 9% 47%	2301
	21st to end	Day	6% 5% 2 5% 6% 3 7% 6% 7% 9% 44%	2530
June	1st to 10th	Day	3 3 1 3 4 2 4 5% 7% 9% 59%	2340
	11th to 20th	Day	4 3 1 3 4 2 4 4 5% 7% 63%	2483
	21st to end	Day	2 2 1 3 2 2 3 3 4 5% 74%	2520
July	1st to 10th	Day	2 2 1 3 3 2 4 4 5% 8% 66%	2520
	11th to 20th	Day	3 3 1 2 3 2 4 4 4 7% 67%	2386
	21st to end	Day	3 2 1 3 4 3 4 5% 5% 9% 61%	2545
August	1st to 10th	Day	3 3 2 3 4 3 4 4 5% 7% 62%	2328
	11th to 20th	Day	3 3 1 3 3 3 3 3 5% 6% 67%	2299
	21st to end	Day	3 3 1 4 3 2 3 4 5% 6% 67%	2551
September	1st to 10th	Day	2 2 1 2 3 2 3 3 4 6% 72%	2013
	11th to 20th	Day	3 2 1 3 3 2 3 4 5% 5% 69%	1980
	21st to end	Day	6% 3 2 3 2 2 2 3 4 5% 70%	1980
October	1st to 10th	Day	7% 3 1 5% 4 2 4 4 4 6% 58%	1940
	11th to 20th	Day	5% 5% 2 4 2 2 4 4 5% 6% 63%	1800
	21st to end	Day	3 4 2 4 5% 3 6% 5% 6% 6% 58%	1900
November	1st to 10th	Day	5% 6% 2 6% 6% 3 5% 4 7% 8% 47%	1674
	11th to 20th	Day	7% 7% 3 4 4 3 4 5% 7% 6% 50%	1710
	21st to end	Day	6% 8% 3 7% 7% 3 4 4 5% 6% 46%	1710
December	1st to 10th	Day	6% 11% 4 10% 7% 4 5% 4 5% 7% 36%	1601
	11th to 20th	Day	7% 9% 5% 11% 10% 5% 8% 7% 7% 8% 22%	2165
	21st to end	Day	6% 10% 5% 10% 11% 5% 6% 6% 6% 7% 28%	3146
January	1st to 10th	Night	7% 9% 4 8% 9% 4 5% 5% 6% 9% 32%	2457
	11th to 20th	Night	8% 9% 4 9% 7% 4 6% 5% 6% 8% 34%	2359
	21st to end	Night	7% 11% 5% 10% 8% 5% 5% 5% 5% 8% 30%	2574
February	1st to 10th	Night	4 9% 4 8% 7% 4 5% 7% 6% 8% 39%	2340
	11th to 20th	Night	6% 9% 3 7% 6% 3 4 4 5% 6% 45%	2151
	21st to end	Night	3 8% 4 7% 7% 3 4 6% 6% 8% 43%	1776
March	1st to 10th	Night	6% 9% 4 9% 7% 4 6% 5% 6% 6% 38%	2087
	11th to 20th	Night	4 7% 3 6% 7% 4 6% 7% 7% 11% 40%	1980
	21st to end	Night	7% 8% 3 6% 6% 4 7% 6% 7% 7% 39%	2178
April	1st to 10th	Night	7% 7% 3 6% 5% 3 6% 5% 5% 7% 46%	1936
	11th to 20th	Night	7% 7% 3 6% 5% 3 5% 5% 4 7% 49%	1631
	21st to end	Night	8% 6% 2 5% 5% 3 4 5% 5% 6% 52%	1620
May	1st to 10th	Night	9% 4 3 5% 5% 3 5% 4 6% 7% 49%	1620
	11th to 20th	Night	8% 5% 2 5% 5% 4 4 5% 7% 9% 47%	1594
	21st to end	Night	8% 7% 2 6% 6% 4 6% 6% 5% 8% 43%	1746
June	1st to 10th	Night	5% 4 1 5% 5% 3 4 5% 7% 8% 53%	1620
	11th to 20th	Night	5% 3 1 3 4 3 3 4 5% 7% 62%	1472
	21st to end	Night	2 2 1 2 3 3 3 4 5% 6% 68%	1440
July	1st to 10th	Night	3 3 2 4 4 2 5% 5% 6% 9% 58%	1440
	11th to 20th	Night	3 4 2 5% 5% 2 5% 6% 5% 7% 56%	1570
	21st to end	Night	4 3 1 3 4 3 5% 6% 7% 9% 54%	1773
August	1st to 10th	Night	4 3 1 5% 3 3 4 6% 6% 8% 57%	1611
	11th to 20th	Night	3 4 1 4 4 3 4 5% 5% 7% 59%	1602
	21st to end	Night	3 4 1 3 3 2 5% 4 6% 7% 61%	1802
September	1st to 10th	Night	3 2 1 3 4 2 3 4 5% 6% 68%	1945
	11th to 20th	Night	4 2 1 3 4 2 3 3 4 6% 68%	1980
	21st to end	Night	5% 4 1 2 3 2 3 3 3 4 70%	1980
October	1st to 10th	Night	5% 4 2 5% 4 2 4 5% 4 6% 60%	2020
	11th to 20th	Night	5% 4 2 4 4 2 3 3 4 6% 63%	2160
	21st to end	Night	4 4 1 4 3 3 4 4 4 7% 61%	2452
November	1st to 10th	Night	6% 6% 3 6% 5% 3 5% 4 5% 8% 50%	2405
	11th to 20th	Night	4 5% 3 7% 5% 3 5% 4 6% 8% 51%	2470
	21st to end	Night	5% 7% 4 6% 5% 3 5% 4 5% 8% 50%	2470
December	1st to 10th	Night	6% 9% 3 8% 6% 3 5% 4 6% 8% 41%	2508
	11th to 20th	Night	8% 10% 4 8% 8% 4 6% 5% 6% 9% 31%	3041
	21st to end	Night	7% 10% 5% 9% 7% 4 6% 5% 6% 8% 32%	4521

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	58% 3 19% 15% 4	1696
	11th to 20th	Day	55% 4 18% 19% 4	1629
	21st to end	Day	61% 4 13% 15% 5% 1	1782
February	1st to 10th	Day	50% 5% 14% 22% 7% 2	1620
	11th to 20th	Day	42% 4 17% 24% 12% 1	1702
	21st to end	Day	44% 4 14% 27% 10% 1	1480
March	1st to 10th	Day	39% 3 16% 27% 13% 2	1872
	11th to 20th	Day	41% 3 12% 27% 14% 2	1980
	21st to end	Day	44% 3 12% 26% 11% 2	2178
April	1st to 10th	Day	38% 4 12% 24% 17% 5%	2020
	11th to 20th	Day	36% 3 8% 25% 25% 4	2279
	21st to end	Day	33% 2 8% 28% 24% 5%	2340
May	1st to 10th	Day	33% 3 6% 25% 28% 6%	2340
	11th to 20th	Day	32% 3 6% 25% 25% 9%	2304
	21st to end	Day	35% 4 8% 25% 21% 7%	2530
June	1st to 10th	Day	22% 3 7% 22% 34% 12%	2340
	11th to 20th	Day	22% 2 5% 18% 29% 24%	2483
	21st to end	Day	15% 1 1 12% 31% 40%	2520
July	1st to 10th	Day	17% 3 3 12% 25% 40%	2451
	11th to 20th	Day	18% 2 2 11% 25% 42%	2314
	21st to end	Day	20% 3 4 13% 28% 32%	2404
August	1st to 10th	Day	21% 3 4 15% 25% 32%	2313
	11th to 20th	Day	19% 2 3 11% 34% 32%	2299
	21st to end	Day	20% 2 2 16% 32% 28%	2551
September	1st to 10th	Day	15% 2 3 17% 31% 31%	2013
	11th to 20th	Day	19% 2 5% 21% 28% 25%	1980
	21st to end	Day	19% 2 5% 20% 37% 17%	1980
October	1st to 10th	Day	28% 2 8% 21% 32% 8%	1940
	11th to 20th	Day	23% 3 7% 37% 25% 5%	1800
	21st to end	Day	27% 3 12% 35% 20% 2	1900
November	1st to 10th	Day	35% 2 16% 24% 20% 2	1674
	11th to 20th	Day	34% 3 14% 37% 12% 1	1710
	21st to end	Day	40% 2 15% 29% 14% 1	1710
December	1st to 10th	Day	48% 4 17% 21% 8% 1	1601
	11th to 20th	Day	58% 3 19% 17% 4	2164
	21st to end	Day	56% 2 14% 17% 10% 1	3146
January	1st to 10th	Night	48% 4 19% 23% 5%	2457
	11th to 20th	Night	49% 3 17% 22% 8% 1	2359
	21st to end	Night	52% 4 16% 19% 8% 1	2574
February	1st to 10th	Night	43% 4 17% 27% 8% 1	2340
	11th to 20th	Night	40% 3 11% 26% 19% 1	2152
	21st to end	Night	39% 4 10% 30% 15% 2	1776
March	1st to 10th	Night	46% 3 11% 24% 13% 2	2087
	11th to 20th	Night	37% 3 11% 28% 18% 2	1980
	21st to end	Night	42% 4 10% 28% 13% 3	2178
April	1st to 10th	Night	38% 3 10% 24% 17% 9%	1936
	11th to 20th	Night	36% 2 6% 27% 24% 4	1631
	21st to end	Night	34% 3 8% 23% 28% 4	1620
May	1st to 10th	Night	34% 3 5% 21% 30% 6%	1620
	11th to 20th	Night	34% 2 7% 24% 25% 9%	1595
	21st to end	Night	39% 4 8% 24% 20% 5%	1746
June	1st to 10th	Night	27% 3 6% 21% 29% 12%	1620
	11th to 20th	Night	23% 2 5% 20% 31% 19%	1472
	21st to end	Night	18% 3 1 14% 28% 37%	1440
July	1st to 10th	Night	24% 3 3 12% 22% 37%	1400
	11th to 20th	Night	27% 3 2 11% 21% 36%	1519
	21st to end	Night	26% 3 4 12% 23% 32%	1674
August	1st to 10th	Night	23% 4 5% 13% 26% 29%	1602
	11th to 20th	Night	25% 3 2 9% 29% 31%	1602
	21st to end	Night	22% 3 3 12% 28% 32%	1802
September	1st to 10th	Night	19% 2 2 15% 24% 37%	1945
	11th to 20th	Night	20% 1 5% 15% 29% 29%	1980
	21st to end	Night	20% 2 3 15% 34% 26%	1980
October	1st to 10th	Night	27% 3 7% 20% 32% 11%	2020
	11th to 20th	Night	24% 3 5% 28% 33% 8%	2160
	21st to end	Night	24% 3 7% 34% 27% 5%	2452
November	1st to 10th	Night	33% 2 11% 29% 20% 5%	2405
	11th to 20th	Night	32% 3 12% 36% 15% 2	2470
	21st to end	Night	35% 2 11% 36% 16% 1	2470
December	1st to 10th	Night	41% 3 17% 26% 11% 1	2508
	11th to 20th	Night	50% 2 17% 24% 7%	3041
	21st to end	Night	51% 1 16% 19% 12%	4521

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% 4 25% 32% 18% 7%	270
	11th to 20th	Day	10% 5% 17% 37% 25% 6%	243
	21st to end	Day	11% 5% 13% 39% 23% 8%	264
February	1st to 10th	Day	8% 5% 28% 34% 20% 5%	240
	11th to 20th	Day	8% 8% 18% 42% 20% 4	358
	21st to end	Day	6% 11% 26% 34% 20% 3	346
March	1st to 10th	Day	12% 7% 18% 37% 22% 4	420
	11th to 20th	Day	7% 8% 22% 37% 22% 5%	420
	21st to end	Day	15% 10% 24% 33% 16% 1	462
April	1st to 10th	Day	12% 10% 25% 28% 20% 5%	420
	11th to 20th	Day	11% 18% 25% 30% 13% 3	412
	21st to end	Day	12% 16% 26% 20% 22% 5%	420
May	1st to 10th	Day	5% 16% 32% 29% 12% 6%	423
	11th to 20th	Day	8% 12% 26% 30% 18% 6%	448
	21st to end	Day	10% 8% 25% 29% 20% 7%	485
June	1st to 10th	Day	5% 10% 26% 34% 18% 7%	450
	11th to 20th	Day	8% 10% 32% 27% 17% 6%	450
	21st to end	Day	2 6% 31% 35% 21% 5%	450
July	1st to 10th	Day	2 4 24% 39% 25% 6%	446
	11th to 20th	Day	2 4 24% 43% 18% 8%	444
	21st to end	Day	2 3 16% 39% 30% 10%	487
August	1st to 10th	Day	4 3 22% 36% 25% 10%	447
	11th to 20th	Day	5% 4 15% 35% 30% 12%	437
	21st to end	Day	3 5% 15% 33% 30% 15%	495
September	1st to 10th	Day	2 5% 21% 28% 21% 23%	450
	11th to 20th	Day	5% 6% 18% 29% 28% 13%	450
	21st to end	Day	7% 6% 19% 23% 31% 13%	450
October	1st to 10th	Day	7% 8% 19% 29% 24% 13%	410
	11th to 20th	Day	5% 10% 20% 21% 25% 19%	270
	21st to end	Day	6% 7% 23% 30% 29% 5%	297
November	1st to 10th	Day	10% 10% 19% 29% 23% 9%	270
	11th to 20th	Day	7% 7% 20% 35% 20% 10%	270
	21st to end	Day	10% 7% 16% 27% 31% 9%	270
December	1st to 10th	Day	10% 8% 14% 37% 23% 9%	270
	11th to 20th	Day	13% 4 15% 41% 24% 3	270
	21st to end	Day	14% 8% 18% 36% 21% 4	297
January	1st to 10th	Night	12% 5% 13% 37% 26% 7%	760
	11th to 20th	Night	12% 5% 13% 36% 28% 7%	726
	21st to end	Night	13% 4 12% 40% 25% 6%	792
February	1st to 10th	Night	10% 4 17% 43% 23% 4	720
	11th to 20th	Night	10% 3 17% 44% 23% 4	704
	21st to end	Night	7% 5% 19% 46% 20% 2	592
March	1st to 10th	Night	10% 6% 13% 47% 21% 4	720
	11th to 20th	Night	7% 6% 15% 44% 27% 2	720
	21st to end	Night	13% 5% 21% 40% 18% 3	792
April	1st to 10th	Night	11% 9% 18% 40% 19% 4	720
	11th to 20th	Night	10% 9% 22% 40% 16% 2	563
	21st to end	Night	11% 6% 19% 38% 21% 4	540
May	1st to 10th	Night	9% 7% 21% 41% 19% 3	540
	11th to 20th	Night	9% 7% 16% 35% 28% 5%	531
	21st to end	Night	11% 7% 16% 33% 27% 5%	584
June	1st to 10th	Night	7% 7% 14% 38% 29% 5%	540
	11th to 20th	Night	5% 8% 17% 40% 28% 1	392
	21st to end	Night	2 4 18% 39% 33% 4	360
July	1st to 10th	Night	4 2 15% 37% 37% 5%	350
	11th to 20th	Night	5% 3 16% 46% 30% 1	475
	21st to end	Night	5% 2 9% 38% 42% 4	591
August	1st to 10th	Night	5% 2 12% 41% 38% 2	537
	11th to 20th	Night	4 2 12% 42% 37% 4	534
	21st to end	Night	5% 3 12% 37% 36% 7%	614
September	1st to 10th	Night	4 3 10% 36% 37% 11%	720
	11th to 20th	Night	4 3 11% 36% 36% 10%	720
	21st to end	Night	7% 4 13% 30% 35% 12%	720
October	1st to 10th	Night	5% 4 16% 37% 30% 8%	720
	11th to 20th	Night	6% 4 13% 34% 36% 7%	720
	21st to end	Night	7% 5% 14% 35% 32% 7%	792
November	1st to 10th	Night	9% 5% 14% 35% 30% 6%	740
	11th to 20th	Night	6% 4 16% 44% 25% 6%	760
	21st to end	Night	8% 4 15% 40% 27% 7%	760
December	1st to 10th	Night	10% 4 14% 45% 24% 3	798
	11th to 20th	Night	14% 4 13% 40% 25% 4	760
	21st to end	Night	17% 5% 16% 39% 19% 3	836

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