Lost Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lost Lake clear sky chart from 2005-11-06 to 2026-10-29.

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	8% 13% 5% 9% 4 4 3 3 4 5% 41%	159015
	Night	10% 14% 5% 11% 5% 4 4 3 4 5% 35%	150414
Transparency	Day	43% 7% 9% 20% 14% 6%	153775
	Night	48% 9% 9% 16% 13% 5%	146667
Seeing	Day	23% 21% 31% 18% 6% 1	17086
	Night	22% 18% 24% 24% 11% 2	25993

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	16% 27% 9% 17% 6% 4 4 3 3 5% 7%	4722
	11th to 20th	Day	11% 12% 4 9% 5% 4 3 2 4 6% 41%	4740
	21st to end	Day	13% 17% 5% 10% 5% 5% 4 3 4 5% 30%	5521
February	1st to 10th	Day	14% 21% 9% 15% 6% 4 3 3 5% 4 15%	1890
	11th to 20th	Day	11% 24% 9% 16% 6% 4 4 3 3 4 17%	1845
	21st to end	Day	12% 27% 7% 13% 5% 4 3 2 3 4 19%	1685
March	1st to 10th	Day	7% 18% 8% 16% 6% 5% 6% 4 5% 6% 20%	4708
	11th to 20th	Day	8% 25% 9% 15% 5% 3 2 2 2 3 25%	5110
	21st to end	Day	9% 26% 9% 17% 6% 6% 5% 3 4 3 11%	5820
April	1st to 10th	Day	14% 26% 8% 12% 5% 4 3 3 4 4 17%	2520
	11th to 20th	Day	13% 23% 6% 12% 5% 4 3 2 3 4 24%	2489
	21st to end	Day	13% 22% 6% 11% 4 4 4 3 4 5% 24%	2670
May	1st to 10th	Day	8% 14% 4 8% 4 3 3 3 4 5% 45%	8195
	11th to 20th	Day	7% 16% 9% 11% 5% 4 3 3 4 6% 32%	8160
	21st to end	Day	10% 13% 5% 9% 5% 4 4 3 5% 7% 35%	8992
June	1st to 10th	Day	19% 14% 5% 7% 4 4 3 3 4 5% 33%	2940
	11th to 20th	Day	14% 14% 5% 9% 4 3 5% 4 5% 6% 30%	2940
	21st to end	Day	8% 8% 3 6% 5% 3 4 3 5% 7% 48%	2940
July	1st to 10th	Day	2 3 1 3 2 3 3 3 4 6% 72%	8219
	11th to 20th	Day	3 3 1 2 2 2 2 2 2 4 79%	8220
	21st to end	Day	2 3 1 2 2 2 2 2 3 5% 76%	8922
August	1st to 10th	Day	1 3 2 4 3 3 3 2 4 5% 70%	7799
	11th to 20th	Day	3 3 1 4 3 3 4 4 6% 8% 61%	7563
	21st to end	Day	5% 5% 2 5% 3 3 4 3 6% 7% 55%	7862
September	1st to 10th	Day	6% 5% 2 5% 3 3 3 3 5% 6% 59%	2520
	11th to 20th	Day	9% 7% 3 7% 4 3 4 4 5% 6% 48%	2520
	21st to end	Day	10% 8% 3 8% 4 3 4 3 4 5% 48%	2231
October	1st to 10th	Day	10% 9% 3 6% 4 3 3 3 4 5% 50%	3380
	11th to 20th	Day	10% 12% 6% 10% 5% 5% 4 4 4 7% 33%	3361
	21st to end	Day	12% 16% 9% 15% 5% 5% 4 3 5% 5% 21%	3478
November	1st to 10th	Day	17% 21% 8% 13% 5% 4 4 2 5% 5% 16%	1793
	11th to 20th	Day	16% 23% 6% 14% 4 4 5% 3 4 5% 15%	1680
	21st to end	Day	15% 20% 6% 11% 5% 4 4 3 4 5% 23%	1680
December	1st to 10th	Day	10% 16% 5% 10% 4 4 3 3 5% 7% 34%	2700
	11th to 20th	Day	16% 23% 8% 15% 7% 5% 4 3 5% 5% 9%	3108
	21st to end	Day	13% 26% 9% 15% 6% 5% 4 3 4 3 13%	4092
January	1st to 10th	Night	16% 24% 9% 16% 5% 5% 5% 3 4 5% 9%	8172
	11th to 20th	Night	11% 14% 4 9% 4 3 3 2 4 5% 39%	8220
	21st to end	Night	12% 15% 5% 13% 5% 4 4 3 4 5% 31%	8674
February	1st to 10th	Night	13% 19% 8% 17% 6% 4 4 3 4 4 18%	2730
	11th to 20th	Night	12% 22% 8% 16% 5% 3 3 2 4 3 22%	2662
	21st to end	Night	12% 24% 8% 13% 6% 4 3 2 3 5% 18%	2120
March	1st to 10th	Night	6% 15% 8% 18% 7% 5% 6% 4 5% 6% 20%	5392
	11th to 20th	Night	8% 19% 8% 17% 5% 4 3 2 2 3 28%	5110
	21st to end	Night	9% 25% 9% 18% 6% 5% 4 3 5% 5% 12%	5397
April	1st to 10th	Night	11% 25% 9% 12% 6% 4 4 3 3 4 19%	2100
	11th to 20th	Night	11% 19% 6% 12% 5% 4 4 3 5% 5% 26%	2079
	21st to end	Night	12% 21% 4 12% 5% 4 4 3 5% 6% 25%	1944
May	1st to 10th	Night	10% 15% 4 8% 4 3 3 3 4 6% 41%	4723
	11th to 20th	Night	6% 22% 9% 12% 6% 3 3 2 3 4 30%	4700
	21st to end	Night	10% 16% 4 8% 4 3 4 4 6% 8% 34%	5181
June	1st to 10th	Night	19% 14% 4 8% 4 3 4 3 5% 4 33%	1680
	11th to 20th	Night	11% 14% 5% 10% 4 4 4 3 4 6% 35%	1680
	21st to end	Night	8% 7% 3 6% 6% 4 4 2 4 7% 50%	1680
July	1st to 10th	Night	2 3 1 5% 3 2 3 3 4 5% 69%	4740
	11th to 20th	Night	2 3 2 4 3 2 2 2 2 3 74%	4740
	21st to end	Night	2 3 1 2 2 2 2 2 3 6% 75%	5153
August	1st to 10th	Night	2 3 2 4 3 3 2 2 5% 6% 67%	4994
	11th to 20th	Night	4 4 3 9% 5% 4 4 3 5% 6% 54%	5292
	21st to end	Night	4 5% 2 7% 4 3 4 3 5% 6% 57%	6381
September	1st to 10th	Night	5% 4 2 7% 3 3 3 3 5% 8% 58%	2100
	11th to 20th	Night	8% 9% 4 9% 4 3 3 3 4 5% 48%	2100
	21st to end	Night	10% 8% 3 9% 3 3 4 3 5% 7% 46%	2385
October	1st to 10th	Night	9% 9% 3 7% 3 2 3 3 4 6% 51%	4040
	11th to 20th	Night	9% 11% 6% 10% 4 4 4 4 6% 7% 35%	4017
	21st to end	Night	13% 15% 9% 16% 5% 4 3 3 4 4 24%	4503
November	1st to 10th	Night	19% 19% 7% 13% 6% 4 3 3 3 5% 18%	2723
	11th to 20th	Night	17% 19% 7% 16% 5% 4 4 3 3 4 18%	2940
	21st to end	Night	12% 18% 6% 14% 5% 4 4 3 5% 5% 25%	2940
December	1st to 10th	Night	9% 13% 4 13% 5% 3 3 3 4 7% 35%	4700
	11th to 20th	Night	16% 23% 7% 16% 6% 5% 4 3 4 4 12%	5316
	21st to end	Night	18% 22% 7% 16% 5% 4 4 3 3 4 13%	7106

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	77% 9% 6% 6% 2	4723
	11th to 20th	Day	43% 7% 5% 14% 20% 10%	4740
	21st to end	Day	57% 5% 5% 11% 16% 6%	5521
February	1st to 10th	Day	70% 7% 9% 10% 3 1	1890
	11th to 20th	Day	71% 7% 7% 10% 5% 1	1854
	21st to end	Day	69% 6% 7% 7% 9% 1	1685
March	1st to 10th	Day	61% 7% 12% 12% 7% 2	4708
	11th to 20th	Day	62% 8% 4 20% 5%	5110
	21st to end	Day	73% 10% 8% 6% 3	5820
April	1st to 10th	Day	71% 6% 9% 13% 2	2520
	11th to 20th	Day	65% 5% 9% 11% 8% 1	2492
	21st to end	Day	62% 7% 9% 14% 7% 2	2670
May	1st to 10th	Day	40% 5% 10% 30% 14% 1	8195
	11th to 20th	Day	44% 14% 16% 19% 7%	8163
	21st to end	Day	44% 11% 18% 22% 5% 1	8994
June	1st to 10th	Day	53% 6% 12% 19% 9% 1	2940
	11th to 20th	Day	52% 8% 13% 17% 9% 1	2940
	21st to end	Day	33% 8% 14% 28% 14% 4	2940
July	1st to 10th	Day	12% 6% 8% 29% 26% 19%	8151
	11th to 20th	Day	12% 3 4 18% 30% 33%	8145
	21st to end	Day	11% 5% 10% 34% 32% 9%	8723
August	1st to 10th	Day	14% 4 6% 20% 31% 24%	6181
	11th to 20th	Day	16% 9% 14% 38% 19% 4	5962
	21st to end	Day	23% 7% 10% 33% 22% 4	6165
September	1st to 10th	Day	24% 5% 11% 26% 22% 11%	2520
	11th to 20th	Day	35% 7% 11% 21% 19% 6%	2520
	21st to end	Day	39% 6% 10% 24% 16% 6%	2231
October	1st to 10th	Day	34% 7% 5% 23% 25% 6%	3380
	11th to 20th	Day	48% 9% 11% 19% 12% 1	3361
	21st to end	Day	56% 14% 5% 16% 8%	3478
November	1st to 10th	Day	71% 5% 8% 12% 4	1793
	11th to 20th	Day	70% 8% 8% 10% 4 1	1680
	21st to end	Day	64% 7% 7% 11% 10% 1	1680
December	1st to 10th	Day	49% 7% 6% 14% 19% 3	2700
	11th to 20th	Day	74% 10% 8% 7% 2	3108
	21st to end	Day	70% 11% 8% 9% 2	4092
January	1st to 10th	Night	73% 11% 6% 7% 2	8172
	11th to 20th	Night	44% 8% 6% 13% 19% 10%	8220
	21st to end	Night	56% 5% 5% 9% 18% 7%	8674
February	1st to 10th	Night	69% 7% 8% 11% 5%	2730
	11th to 20th	Night	67% 6% 8% 11% 6% 1	2664
	21st to end	Night	68% 5% 7% 11% 8% 1	2120
March	1st to 10th	Night	59% 9% 12% 13% 4 3	5392
	11th to 20th	Night	56% 10% 9% 18% 7% 1	5110
	21st to end	Night	70% 11% 9% 8% 2	5397
April	1st to 10th	Night	67% 8% 9% 11% 4	2100
	11th to 20th	Night	61% 6% 11% 12% 7% 3	2079
	21st to end	Night	60% 7% 10% 13% 8% 1	1944
May	1st to 10th	Night	43% 6% 9% 24% 17% 1	4721
	11th to 20th	Night	51% 13% 12% 17% 5% 1	4700
	21st to end	Night	43% 12% 19% 21% 5% 1	5182
June	1st to 10th	Night	54% 6% 12% 21% 7% 1	1680
	11th to 20th	Night	49% 7% 13% 20% 9% 1	1680
	21st to end	Night	34% 7% 13% 26% 16% 4	1680
July	1st to 10th	Night	12% 9% 7% 25% 29% 18%	4700
	11th to 20th	Night	17% 3 5% 14% 31% 30%	4692
	21st to end	Night	11% 5% 12% 30% 32% 10%	5040
August	1st to 10th	Night	13% 3 6% 19% 29% 29%	3951
	11th to 20th	Night	18% 16% 13% 28% 21% 4	4169
	21st to end	Night	20% 12% 11% 28% 22% 7%	5000
September	1st to 10th	Night	23% 6% 13% 24% 22% 12%	2100
	11th to 20th	Night	36% 7% 9% 19% 17% 10%	2100
	21st to end	Night	38% 6% 12% 20% 17% 8%	2385
October	1st to 10th	Night	33% 7% 7% 22% 28% 4	4040
	11th to 20th	Night	43% 10% 12% 19% 14% 3	4017
	21st to end	Night	55% 13% 5% 15% 10% 1	4503
November	1st to 10th	Night	70% 5% 7% 12% 6% 1	2723
	11th to 20th	Night	68% 8% 7% 10% 7%	2940
	21st to end	Night	62% 6% 7% 13% 10% 1	2940
December	1st to 10th	Night	45% 11% 7% 16% 18% 4	4700
	11th to 20th	Night	73% 10% 7% 7% 3	5316
	21st to end	Night	70% 13% 8% 7% 2	7106

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	39% 29% 18% 11% 4	220
	11th to 20th	Day	30% 21% 33% 10% 5%	220
	21st to end	Day	30% 25% 25% 16% 4	358
February	1st to 10th	Day	30% 31% 25% 11% 3	430
	11th to 20th	Day	32% 32% 24% 11% 1	425
	21st to end	Day	36% 26% 25% 11% 2	423
March	1st to 10th	Day	30% 29% 28% 8% 4	540
	11th to 20th	Day	35% 24% 24% 11% 5% 1	540
	21st to end	Day	37% 27% 23% 10% 2	594
April	1st to 10th	Day	33% 24% 25% 13% 5% 1	540
	11th to 20th	Day	30% 29% 26% 11% 2 2	532
	21st to end	Day	28% 25% 32% 12% 2 1	540
May	1st to 10th	Day	25% 19% 34% 15% 6% 1	543
	11th to 20th	Day	29% 19% 27% 17% 5% 2	568
	21st to end	Day	24% 15% 33% 20% 6% 2	617
June	1st to 10th	Day	23% 20% 30% 18% 7% 2	570
	11th to 20th	Day	23% 25% 33% 12% 5% 1	570
	21st to end	Day	12% 18% 38% 23% 9% 1	570
July	1st to 10th	Day	5% 14% 48% 25% 5% 1	566
	11th to 20th	Day	6% 18% 43% 24% 8% 2	564
	21st to end	Day	5% 13% 41% 25% 12% 3	619
August	1st to 10th	Day	5% 11% 43% 27% 10% 4	567
	11th to 20th	Day	4 13% 38% 31% 10% 3	557
	21st to end	Day	9% 19% 37% 23% 9% 3	627
September	1st to 10th	Day	8% 17% 36% 26% 11% 2	570
	11th to 20th	Day	16% 17% 35% 24% 7% 1	570
	21st to end	Day	16% 19% 33% 22% 8% 1	570
October	1st to 10th	Day	20% 17% 31% 23% 7% 1	570
	11th to 20th	Day	25% 21% 27% 19% 7% 1	570
	21st to end	Day	32% 23% 24% 14% 5% 2	517
November	1st to 10th	Day	33% 24% 24% 16% 3	297
	11th to 20th	Day	30% 27% 24% 12% 4 2	220
	21st to end	Day	25% 25% 32% 15% 3	220
December	1st to 10th	Day	34% 17% 24% 19% 5% 1	220
	11th to 20th	Day	36% 27% 26% 9% 2	220
	21st to end	Day	38% 26% 19% 13% 2 1	242
January	1st to 10th	Night	32% 26% 20% 15% 6%	840
	11th to 20th	Night	26% 20% 24% 21% 7% 1	840
	21st to end	Night	24% 20% 26% 22% 7% 1	924
February	1st to 10th	Night	25% 22% 25% 22% 6%	840
	11th to 20th	Night	28% 25% 20% 21% 6%	824
	21st to end	Night	30% 24% 22% 20% 4	692
March	1st to 10th	Night	25% 24% 21% 21% 8% 1	840
	11th to 20th	Night	25% 23% 23% 21% 7% 1	840
	21st to end	Night	29% 24% 23% 15% 8% 1	924
April	1st to 10th	Night	27% 19% 25% 19% 9% 1	840
	11th to 20th	Night	26% 21% 24% 18% 9% 3	831
	21st to end	Night	25% 18% 26% 20% 10% 1	684
May	1st to 10th	Night	23% 14% 22% 25% 14% 1	420
	11th to 20th	Night	21% 13% 22% 28% 14% 2	414
	21st to end	Night	18% 15% 22% 28% 15% 2	455
June	1st to 10th	Night	28% 14% 19% 24% 13% 2	420
	11th to 20th	Night	18% 19% 30% 23% 9%	420
	21st to end	Night	13% 11% 27% 32% 16% 1	420
July	1st to 10th	Night	8% 6% 33% 34% 18%	410
	11th to 20th	Night	5% 9% 38% 33% 13% 2	408
	21st to end	Night	3 8% 29% 42% 17% 2	460
August	1st to 10th	Night	4 9% 26% 37% 20% 4	525
	11th to 20th	Night	6% 6% 24% 32% 25% 8%	624
	21st to end	Night	6% 10% 30% 31% 19% 3	882
September	1st to 10th	Night	8% 9% 24% 35% 21% 3	840
	11th to 20th	Night	12% 13% 22% 28% 21% 4	840
	21st to end	Night	15% 10% 25% 28% 18% 3	840
October	1st to 10th	Night	17% 13% 23% 28% 15% 3	840
	11th to 20th	Night	20% 14% 20% 27% 16% 3	840
	21st to end	Night	25% 21% 20% 21% 10% 3	912
November	1st to 10th	Night	31% 21% 19% 23% 6%	820
	11th to 20th	Night	29% 24% 24% 18% 5% 1	840
	21st to end	Night	21% 25% 24% 23% 7%	840
December	1st to 10th	Night	26% 20% 26% 21% 8%	840
	11th to 20th	Night	32% 22% 23% 19% 4	840
	21st to end	Night	34% 26% 23% 13% 3 1	924

Page generated at 2026-10-26 01:37:51. Version ac07

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