Laonil Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Laonil Lake clear sky chart from 2005-11-06 to 2026-01-02.

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	10% 10% 4 10% 6% 5% 5% 4 6% 7% 33%	131644
	Night	8% 11% 4 11% 7% 6% 6% 5% 6% 7% 29%	128379
Transparency	Day	49% 5% 14% 23% 9%	131318
	Night	54% 5% 13% 21% 7%	128286
Seeing	Day	17% 12% 32% 25% 11% 3	17412
	Night	16% 9% 31% 30% 12% 2	26690

By Month

Percentage Cloud Cover NW (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	4 13% 7% 20% 11% 9% 6% 3 4 5% 18%	2725
	11th to 20th	Day	4 11% 5% 13% 10% 9% 12% 8% 11% 6% 11%	2702
	21st to end	Day	5% 17% 7% 20% 8% 6% 5% 3 4 6% 18%	3658
February	1st to 10th	Day	4 9% 6% 10% 11% 7% 7% 7% 10% 8% 23%	1600
	11th to 20th	Day	5% 10% 5% 10% 6% 6% 6% 5% 8% 8% 30%	1621
	21st to end	Day	3 9% 6% 14% 8% 7% 7% 4 5% 6% 29%	1564
March	1st to 10th	Day	4 12% 6% 15% 7% 8% 6% 4 4 6% 29%	4500
	11th to 20th	Day	5% 8% 3 11% 10% 7% 6% 4 7% 8% 30%	4656
	21st to end	Day	4 10% 4 11% 6% 5% 5% 3 5% 7% 39%	5969
April	1st to 10th	Day	8% 10% 4 10% 6% 6% 5% 4 6% 6% 35%	2400
	11th to 20th	Day	10% 10% 4 9% 7% 5% 5% 4 6% 7% 33%	2583
	21st to end	Day	9% 10% 4 9% 6% 5% 5% 5% 7% 7% 34%	2800
May	1st to 10th	Day	11% 11% 4 9% 5% 5% 5% 3 6% 8% 35%	6427
	11th to 20th	Day	19% 10% 3 6% 5% 4 4 4 5% 8% 31%	6831
	21st to end	Day	12% 11% 3 8% 4 4 4 3 4 6% 41%	7907
June	1st to 10th	Day	17% 10% 3 8% 5% 4 5% 4 5% 6% 31%	3200
	11th to 20th	Day	20% 10% 3 8% 5% 5% 5% 4 6% 7% 25%	3200
	21st to end	Day	18% 8% 3 7% 6% 5% 5% 4 6% 8% 30%	3200
July	1st to 10th	Day	7% 4 1 5% 5% 6% 6% 5% 7% 10% 44%	7240
	11th to 20th	Day	7% 4 2 5% 4 5% 5% 4 6% 8% 50%	7240
	21st to end	Day	9% 6% 2 6% 5% 5% 5% 5% 7% 9% 40%	7693
August	1st to 10th	Day	7% 4 2 5% 4 5% 6% 5% 7% 11% 44%	4552
	11th to 20th	Day	12% 7% 3 8% 5% 5% 5% 4 6% 7% 38%	4483
	21st to end	Day	12% 6% 3 7% 5% 5% 6% 5% 7% 9% 35%	4793
September	1st to 10th	Day	12% 9% 3 9% 5% 4 6% 4 6% 8% 34%	2400
	11th to 20th	Day	17% 10% 3 9% 5% 4 5% 4 5% 8% 29%	2365
	21st to end	Day	15% 11% 2 6% 4 5% 4 4 5% 7% 37%	2190
October	1st to 10th	Day	14% 11% 4 9% 5% 5% 6% 5% 6% 7% 27%	3270
	11th to 20th	Day	12% 15% 5% 10% 5% 5% 5% 4 6% 7% 27%	2928
	21st to end	Day	15% 22% 8% 12% 5% 4 4 3 4 4 18%	3116
November	1st to 10th	Day	15% 18% 7% 15% 8% 6% 4 2 4 5% 16%	1547
	11th to 20th	Day	12% 14% 6% 17% 10% 8% 5% 4 5% 3 17%	1470
	21st to end	Day	9% 13% 9% 17% 11% 7% 7% 4 5% 6% 13%	1417
December	1st to 10th	Day	7% 17% 8% 18% 10% 5% 6% 7% 5% 5% 11%	2020
	11th to 20th	Day	6% 10% 4 14% 10% 7% 7% 4 6% 7% 25%	2319
	21st to end	Day	5% 13% 5% 13% 8% 6% 5% 4 6% 6% 28%	3058
January	1st to 10th	Night	4 11% 5% 19% 11% 9% 8% 6% 7% 5% 15%	7243
	11th to 20th	Night	4 10% 5% 16% 11% 10% 10% 7% 10% 6% 12%	7196
	21st to end	Night	6% 15% 7% 15% 8% 6% 7% 4 6% 6% 19%	7304
February	1st to 10th	Night	6% 10% 4 11% 7% 7% 7% 5% 8% 10% 24%	2800
	11th to 20th	Night	6% 9% 4 9% 7% 7% 6% 6% 7% 7% 30%	2682
	21st to end	Night	2 9% 5% 11% 8% 8% 7% 6% 9% 8% 28%	2065
March	1st to 10th	Night	5% 11% 4 13% 7% 7% 7% 5% 6% 7% 30%	5374
	11th to 20th	Night	7% 10% 4 12% 8% 7% 5% 4 5% 8% 31%	5323
	21st to end	Night	4 8% 3 11% 6% 5% 5% 4 6% 6% 40%	4984
April	1st to 10th	Night	8% 10% 4 9% 6% 6% 5% 4 5% 7% 36%	2000
	11th to 20th	Night	10% 12% 4 9% 6% 6% 5% 4 5% 7% 33%	1766
	21st to end	Night	9% 9% 3 10% 6% 4 5% 3 5% 6% 40%	1600
May	1st to 10th	Night	12% 9% 3 8% 5% 6% 7% 4 5% 6% 33%	3552
	11th to 20th	Night	16% 7% 2 6% 5% 5% 6% 4 7% 7% 34%	3079
	21st to end	Night	11% 10% 2 8% 5% 3 3 3 5% 8% 40%	2968
June	1st to 10th	Night	15% 9% 2 7% 7% 5% 5% 4 5% 8% 34%	1200
	11th to 20th	Night	15% 10% 3 8% 5% 6% 4 4 4 7% 34%	1200
	21st to end	Night	14% 8% 3 8% 5% 4 5% 5% 6% 7% 37%	1200
July	1st to 10th	Night	6% 3 1 5% 5% 4 5% 6% 8% 12% 45%	2720
	11th to 20th	Night	6% 4 2 6% 5% 5% 5% 5% 6% 9% 49%	2720
	21st to end	Night	8% 4 2 5% 4 4 4 4 7% 11% 48%	3150
August	1st to 10th	Night	7% 4 2 4 3 4 5% 5% 7% 11% 48%	2608
	11th to 20th	Night	11% 6% 3 7% 5% 4 5% 4 5% 8% 42%	2576
	21st to end	Night	10% 5% 2 7% 4 5% 5% 5% 7% 10% 41%	3112
September	1st to 10th	Night	12% 6% 3 7% 5% 5% 5% 4 6% 8% 38%	2000
	11th to 20th	Night	16% 9% 3 7% 4 5% 5% 4 5% 7% 34%	2035
	21st to end	Night	12% 8% 3 6% 4 3 5% 4 6% 7% 42%	2206
October	1st to 10th	Night	14% 12% 3 7% 4 4 4 4 5% 7% 37%	3920
	11th to 20th	Night	12% 13% 4 10% 5% 5% 5% 3 5% 6% 31%	4188
	21st to end	Night	15% 19% 7% 11% 5% 4 4 4 5% 6% 20%	4672
November	1st to 10th	Night	15% 19% 7% 13% 8% 5% 4 3 5% 5% 17%	2970
	11th to 20th	Night	12% 15% 6% 13% 11% 8% 6% 3 4 4 19%	3150
	21st to end	Night	7% 15% 7% 15% 10% 9% 7% 4 5% 5% 17%	3203
December	1st to 10th	Night	8% 18% 7% 16% 10% 11% 8% 4 4 3 10%	5380
	11th to 20th	Night	6% 11% 6% 16% 8% 6% 6% 6% 6% 7% 22%	6093
	21st to end	Night	5% 14% 6% 15% 7% 6% 5% 4 5% 6% 28%	8140

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	70% 2 8% 14% 5%	2725
	11th to 20th	Day	65% 4 8% 18% 5%	2720
	21st to end	Day	68% 4 8% 13% 7%	3658
February	1st to 10th	Day	53% 4 13% 21% 8%	1600
	11th to 20th	Day	49% 3 13% 24% 11%	1629
	21st to end	Day	54% 4 12% 20% 9%	1564
March	1st to 10th	Day	57% 3 10% 20% 9% 1	4500
	11th to 20th	Day	48% 7% 11% 20% 14%	4657
	21st to end	Day	44% 4 8% 21% 23% 1	5969
April	1st to 10th	Day	47% 6% 11% 21% 15% 1	2400
	11th to 20th	Day	48% 5% 12% 24% 10% 1	2583
	21st to end	Day	46% 4 12% 25% 11% 1	2800
May	1st to 10th	Day	48% 4 11% 27% 10% 1	6427
	11th to 20th	Day	51% 4 11% 25% 9% 1	6835
	21st to end	Day	44% 4 11% 19% 21% 1	7908
June	1st to 10th	Day	52% 5% 10% 21% 11% 1	3200
	11th to 20th	Day	56% 5% 12% 19% 7% 1	3200
	21st to end	Day	51% 6% 13% 22% 9%	3200
July	1st to 10th	Day	31% 7% 21% 32% 8%	7161
	11th to 20th	Day	29% 6% 15% 41% 9%	7153
	21st to end	Day	37% 7% 21% 31% 4	7475
August	1st to 10th	Day	32% 7% 24% 32% 5%	4536
	11th to 20th	Day	43% 6% 22% 25% 4	4525
	21st to end	Day	43% 6% 24% 23% 4	4792
September	1st to 10th	Day	48% 6% 20% 18% 8%	2400
	11th to 20th	Day	53% 5% 20% 18% 3	2365
	21st to end	Day	47% 4 20% 24% 4	2190
October	1st to 10th	Day	53% 5% 16% 21% 4	3270
	11th to 20th	Day	55% 5% 16% 20% 4	2928
	21st to end	Day	70% 6% 10% 11% 2	3116
November	1st to 10th	Day	73% 3 10% 11% 3	1547
	11th to 20th	Day	70% 5% 10% 12% 3	1470
	21st to end	Day	72% 3 11% 10% 4	1417
December	1st to 10th	Day	71% 6% 9% 9% 4	2020
	11th to 20th	Day	58% 4 10% 21% 6%	2320
	21st to end	Day	54% 4 12% 20% 10%	3058
January	1st to 10th	Night	68% 4 10% 14% 4	7243
	11th to 20th	Night	67% 4 8% 17% 3	7240
	21st to end	Night	64% 4 14% 11% 7%	7304
February	1st to 10th	Night	53% 4 13% 20% 10% 1	2800
	11th to 20th	Night	51% 4 14% 23% 9%	2684
	21st to end	Night	50% 5% 14% 22% 9%	2065
March	1st to 10th	Night	52% 5% 11% 22% 9% 1	5374
	11th to 20th	Night	50% 5% 9% 22% 12%	5323
	21st to end	Night	41% 5% 9% 24% 20% 2	4984
April	1st to 10th	Night	47% 4 12% 20% 15% 2	2000
	11th to 20th	Night	48% 6% 9% 21% 14% 1	1766
	21st to end	Night	45% 4 9% 29% 12% 2	1600
May	1st to 10th	Night	50% 5% 12% 24% 10% 1	3552
	11th to 20th	Night	46% 5% 11% 27% 9% 2	3079
	21st to end	Night	43% 5% 11% 17% 22% 2	2968
June	1st to 10th	Night	47% 5% 12% 22% 14% 1	1200
	11th to 20th	Night	49% 6% 14% 22% 8% 1	1200
	21st to end	Night	45% 6% 14% 26% 8% 1	1200
July	1st to 10th	Night	29% 6% 21% 36% 8%	2690
	11th to 20th	Night	30% 6% 14% 45% 5%	2684
	21st to end	Night	29% 6% 25% 37% 3	3063
August	1st to 10th	Night	27% 7% 23% 35% 8%	2600
	11th to 20th	Night	39% 7% 23% 24% 7%	2600
	21st to end	Night	37% 6% 24% 30% 3	3112
September	1st to 10th	Night	43% 5% 20% 25% 7% 1	2000
	11th to 20th	Night	48% 5% 19% 23% 5%	2035
	21st to end	Night	40% 4 18% 29% 8% 1	2206
October	1st to 10th	Night	47% 4 14% 28% 6%	3920
	11th to 20th	Night	54% 4 14% 23% 5%	4188
	21st to end	Night	65% 5% 15% 13% 2	4672
November	1st to 10th	Night	70% 4 10% 13% 3	2970
	11th to 20th	Night	69% 5% 11% 11% 4	3150
	21st to end	Night	68% 4 12% 12% 4	3203
December	1st to 10th	Night	78% 4 7% 8% 3	5380
	11th to 20th	Night	60% 4 9% 19% 8%	6091
	21st to end	Night	57% 3 11% 21% 7%	8140

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	12% 12% 42% 23% 10%	202
	11th to 20th	Day	14% 10% 44% 22% 8% 2	200
	21st to end	Day	13% 16% 33% 27% 10% 1	255
February	1st to 10th	Day	7% 14% 39% 26% 10% 3	300
	11th to 20th	Day	8% 14% 37% 29% 11% 2	300
	21st to end	Day	5% 15% 35% 33% 9% 2	249
March	1st to 10th	Day	12% 14% 33% 26% 12% 2	300
	11th to 20th	Day	9% 12% 40% 28% 10% 1	333
	21st to end	Day	12% 14% 35% 27% 11% 2	550
April	1st to 10th	Day	14% 14% 38% 23% 8% 2	500
	11th to 20th	Day	15% 13% 38% 23% 10% 1	650
	21st to end	Day	14% 12% 34% 26% 12% 2	700
May	1st to 10th	Day	20% 12% 31% 25% 11% 1	703
	11th to 20th	Day	18% 16% 30% 23% 11% 2	725
	21st to end	Day	19% 11% 28% 29% 11% 2	789
June	1st to 10th	Day	23% 13% 29% 22% 10% 3	730
	11th to 20th	Day	27% 11% 29% 22% 8% 2	730
	21st to end	Day	19% 11% 25% 26% 14% 5%	730
July	1st to 10th	Day	14% 11% 29% 29% 13% 3	721
	11th to 20th	Day	15% 7% 25% 30% 18% 5%	718
	21st to end	Day	15% 7% 28% 27% 19% 4	794
August	1st to 10th	Day	13% 7% 28% 30% 16% 5%	726
	11th to 20th	Day	15% 10% 28% 26% 16% 5%	715
	21st to end	Day	17% 9% 30% 31% 9% 4	770
September	1st to 10th	Day	20% 17% 35% 22% 7%	530
	11th to 20th	Day	21% 9% 35% 24% 9% 2	495
	21st to end	Day	20% 18% 35% 20% 7%	330
October	1st to 10th	Day	25% 14% 33% 20% 7% 1	330
	11th to 20th	Day	25% 20% 31% 16% 8% 1	330
	21st to end	Day	27% 14% 30% 18% 8% 2	363
November	1st to 10th	Day	17% 15% 37% 20% 11%	330
	11th to 20th	Day	21% 17% 38% 20% 3	330
	21st to end	Day	16% 16% 40% 21% 7% 1	302
December	1st to 10th	Day	13% 18% 32% 28% 6% 3	220
	11th to 20th	Day	12% 12% 48% 22% 5%	220
	21st to end	Day	8% 9% 31% 35% 13% 4	242
January	1st to 10th	Night	14% 11% 32% 32% 11%	1006
	11th to 20th	Night	14% 10% 39% 28% 8% 1	1000
	21st to end	Night	18% 13% 34% 26% 8% 1	1100
February	1st to 10th	Night	10% 10% 39% 28% 11% 2	1000
	11th to 20th	Night	10% 9% 33% 31% 13% 3	934
	21st to end	Night	6% 10% 35% 32% 15% 2	660
March	1st to 10th	Night	10% 10% 29% 35% 15% 2	800
	11th to 20th	Night	15% 10% 34% 28% 11% 2	792
	21st to end	Night	12% 8% 30% 30% 18% 2	660
April	1st to 10th	Night	14% 9% 31% 32% 14% 2	600
	11th to 20th	Night	16% 7% 33% 31% 13% 1	593
	21st to end	Night	13% 9% 33% 34% 11% 1	600
May	1st to 10th	Night	19% 10% 31% 30% 9% 1	600
	11th to 20th	Night	16% 9% 30% 31% 12% 1	562
	21st to end	Night	18% 6% 29% 33% 13% 1	433
June	1st to 10th	Night	22% 7% 26% 30% 15% 1	400
	11th to 20th	Night	20% 8% 25% 31% 15% 1	400
	21st to end	Night	16% 6% 23% 35% 18% 2	400
July	1st to 10th	Night	14% 5% 23% 38% 18% 1	390
	11th to 20th	Night	13% 5% 21% 34% 24% 3	388
	21st to end	Night	14% 5% 18% 36% 23% 4	461
August	1st to 10th	Night	12% 6% 23% 32% 24% 3	597
	11th to 20th	Night	14% 7% 22% 33% 20% 3	594
	21st to end	Night	17% 6% 26% 35% 16% 1	660
September	1st to 10th	Night	17% 8% 26% 33% 15% 1	600
	11th to 20th	Night	21% 6% 27% 36% 10%	600
	21st to end	Night	17% 10% 33% 33% 7%	606
October	1st to 10th	Night	24% 9% 31% 26% 8% 1	800
	11th to 20th	Night	27% 10% 30% 23% 8% 2	974
	21st to end	Night	25% 13% 28% 23% 9% 1	1100
November	1st to 10th	Night	23% 11% 34% 22% 9% 1	1025
	11th to 20th	Night	21% 12% 34% 26% 7% 1	1050
	21st to end	Night	15% 12% 38% 27% 8% 1	1050
December	1st to 10th	Night	13% 12% 33% 31% 10% 2	1050
	11th to 20th	Night	14% 11% 37% 26% 10% 3	1050
	21st to end	Night	12% 9% 28% 35% 14% 2	1155

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