Lac des Piles
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac des Piles clear sky chart from 2005-11-06 to 2025-05-11.

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	17% 10% 3 8% 5% 5% 5% 4 5% 6% 31%	113381
	Night	17% 11% 4 9% 5% 4 5% 3 5% 6% 31%	115529
Transparency	Day	52% 5% 13% 19% 10% 1	116861
	Night	54% 5% 12% 19% 10% 1	120214
Seeing	Day	24% 13% 31% 21% 9% 2	15094
	Night	24% 9% 30% 28% 9% 1	24227

By Month

Percentage Cloud Cover NE (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	14% 18% 6% 12% 6% 7% 5% 4 4 5% 20%	3597
	11th to 20th	Day	11% 14% 6% 16% 7% 6% 5% 3 4 4 24%	3570
	21st to end	Day	9% 11% 6% 13% 6% 4 5% 4 5% 7% 30%	3960
February	1st to 10th	Day	12% 16% 6% 12% 7% 6% 4 2 4 5% 26%	1670
	11th to 20th	Day	12% 17% 5% 11% 6% 5% 4 3 5% 6% 26%	1875
	21st to end	Day	15% 16% 5% 9% 7% 5% 4 3 3 5% 28%	1650
March	1st to 10th	Day	21% 16% 4 10% 6% 4 4 3 4 3 25%	4476
	11th to 20th	Day	11% 14% 4 10% 5% 5% 5% 3 5% 6% 32%	4648
	21st to end	Day	16% 14% 4 8% 5% 4 4 3 3 4 33%	5970
April	1st to 10th	Day	22% 13% 4 8% 4 4 4 3 4 5% 30%	2400
	11th to 20th	Day	21% 7% 3 7% 4 4 4 3 5% 5% 36%	2403
	21st to end	Day	21% 11% 3 7% 4 5% 4 4 5% 6% 30%	2600
May	1st to 10th	Day	23% 8% 2 7% 4 4 4 3 5% 6% 33%	4485
	11th to 20th	Day	17% 6% 2 7% 5% 5% 5% 4 6% 9% 33%	4398
	21st to end	Day	17% 7% 3 8% 5% 5% 6% 4 6% 7% 31%	4837
June	1st to 10th	Day	20% 8% 3 8% 6% 5% 5% 4 6% 7% 27%	2660
	11th to 20th	Day	17% 7% 2 7% 5% 5% 5% 4 6% 7% 33%	2660
	21st to end	Day	23% 10% 3 8% 6% 5% 4 4 5% 6% 27%	2660
July	1st to 10th	Day	14% 7% 2 8% 6% 6% 6% 5% 7% 9% 31%	4440
	11th to 20th	Day	15% 6% 2 7% 5% 6% 6% 5% 8% 9% 31%	4440
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 5% 6% 7% 41%	4814
August	1st to 10th	Day	14% 6% 2 7% 6% 6% 7% 5% 8% 10% 29%	4423
	11th to 20th	Day	19% 7% 2 6% 5% 4 5% 5% 7% 8% 31%	4121
	21st to end	Day	18% 6% 3 6% 4 5% 5% 4 5% 8% 37%	4181
September	1st to 10th	Day	16% 5% 2 6% 4 4 5% 4 7% 7% 41%	2280
	11th to 20th	Day	15% 6% 2 5% 4 4 4 3 5% 7% 45%	2167
	21st to end	Day	21% 7% 3 6% 3 3 3 3 4 7% 39%	2090
October	1st to 10th	Day	21% 8% 2 7% 4 4 5% 3 4 7% 34%	2005
	11th to 20th	Day	22% 10% 2 8% 6% 6% 4 5% 5% 6% 26%	1801
	21st to end	Day	26% 11% 3 7% 3 4 4 3 5% 6% 27%	1881
November	1st to 10th	Day	18% 11% 4 8% 5% 5% 5% 3 4 5% 33%	1761
	11th to 20th	Day	21% 13% 4 8% 6% 4 4 3 4 6% 28%	1725
	21st to end	Day	21% 16% 4 7% 6% 4 4 3 5% 5% 25%	1600
December	1st to 10th	Day	19% 16% 6% 11% 6% 5% 4 3 4 4 22%	2387
	11th to 20th	Day	18% 13% 5% 9% 4 4 4 3 5% 5% 28%	2786
	21st to end	Day	19% 15% 5% 10% 6% 4 4 3 4 5% 26%	3960
January	1st to 10th	Night	13% 19% 7% 14% 6% 5% 4 3 4 5% 19%	6349
	11th to 20th	Night	10% 18% 7% 14% 7% 5% 5% 3 4 5% 22%	6315
	21st to end	Night	9% 11% 5% 13% 7% 6% 6% 4 5% 6% 28%	6996
February	1st to 10th	Night	11% 15% 4 10% 6% 5% 5% 4 5% 5% 29%	2727
	11th to 20th	Night	12% 15% 5% 12% 6% 5% 5% 3 4 5% 28%	2410
	21st to end	Night	15% 12% 5% 9% 6% 5% 5% 4 4 5% 31%	1980
March	1st to 10th	Night	22% 14% 4 12% 6% 4 4 3 4 4 23%	5364
	11th to 20th	Night	13% 15% 4 8% 5% 5% 5% 4 6% 7% 28%	5307
	21st to end	Night	16% 11% 4 9% 5% 5% 5% 4 5% 5% 31%	4962
April	1st to 10th	Night	22% 11% 3 7% 4 4 4 4 5% 6% 32%	2000
	11th to 20th	Night	20% 9% 3 7% 4 4 4 3 5% 5% 36%	1945
	21st to end	Night	23% 9% 3 7% 4 3 4 3 4 6% 35%	1800
May	1st to 10th	Night	21% 9% 3 7% 5% 4 5% 4 5% 6% 31%	2705
	11th to 20th	Night	21% 6% 2 5% 3 4 6% 4 5% 8% 36%	2501
	21st to end	Night	18% 6% 2 7% 6% 6% 5% 3 6% 9% 32%	2738
June	1st to 10th	Night	20% 6% 2 7% 4 4 5% 3 6% 8% 34%	1520
	11th to 20th	Night	19% 7% 2 6% 5% 4 4 4 6% 8% 35%	1520
	21st to end	Night	20% 8% 3 7% 5% 4 5% 4 6% 7% 32%	1520
July	1st to 10th	Night	14% 6% 2 8% 6% 6% 6% 4 7% 8% 33%	2520
	11th to 20th	Night	16% 5% 2 6% 5% 4 5% 4 6% 7% 39%	2520
	21st to end	Night	12% 4 1 5% 4 4 5% 4 6% 8% 46%	2739
August	1st to 10th	Night	14% 5% 3 7% 5% 5% 5% 4 7% 8% 37%	2506
	11th to 20th	Night	17% 7% 3 7% 4 4 4 3 6% 7% 38%	2674
	21st to end	Night	17% 7% 3 8% 4 4 4 3 4 6% 39%	3471
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 5% 7% 45%	1900
	11th to 20th	Night	15% 5% 2 4 4 3 3 3 5% 7% 49%	2012
	21st to end	Night	18% 6% 2 5% 4 3 4 3 4 5% 45%	2090
October	1st to 10th	Night	18% 8% 3 7% 5% 3 4 3 5% 5% 40%	2172
	11th to 20th	Night	22% 8% 3 7% 5% 4 4 3 5% 6% 34%	2378
	21st to end	Night	24% 9% 3 7% 4 4 4 3 4 7% 31%	2717
November	1st to 10th	Night	18% 10% 3 8% 5% 4 4 4 5% 6% 33%	2537
	11th to 20th	Night	19% 10% 3 8% 6% 5% 5% 3 5% 6% 31%	2671
	21st to end	Night	22% 15% 4 7% 5% 4 4 3 5% 5% 27%	2800
December	1st to 10th	Night	16% 14% 5% 10% 6% 5% 5% 4 5% 6% 22%	4778
	11th to 20th	Night	23% 12% 4 9% 6% 4 5% 3 4 4 26%	5389
	21st to end	Night	21% 17% 6% 9% 4 3 3 2 3 4 27%	6996

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	66% 4 11% 15% 4	3598
	11th to 20th	Day	64% 3 9% 16% 6% 2	3600
	21st to end	Day	54% 3 9% 19% 14% 1	3960
February	1st to 10th	Day	62% 2 9% 16% 9% 2	1670
	11th to 20th	Day	59% 3 13% 14% 11% 1	1884
	21st to end	Day	61% 3 8% 16% 10% 3	1650
March	1st to 10th	Day	63% 3 8% 12% 11% 3	4479
	11th to 20th	Day	53% 5% 16% 14% 11% 2	4648
	21st to end	Day	54% 4 6% 17% 16% 3	5970
April	1st to 10th	Day	56% 3 10% 15% 12% 2	2400
	11th to 20th	Day	50% 3 10% 22% 12% 3	2403
	21st to end	Day	55% 4 10% 17% 13% 3	2600
May	1st to 10th	Day	51% 3 12% 19% 14% 2	4499
	11th to 20th	Day	46% 5% 20% 20% 9% 1	4402
	21st to end	Day	49% 5% 12% 17% 16% 2	4837
June	1st to 10th	Day	54% 5% 11% 19% 9% 2	2660
	11th to 20th	Day	46% 5% 14% 22% 11% 2	2660
	21st to end	Day	57% 5% 11% 16% 10% 1	2660
July	1st to 10th	Day	46% 7% 15% 23% 8%	4370
	11th to 20th	Day	45% 9% 19% 21% 6%	4365
	21st to end	Day	40% 6% 17% 27% 9%	4661
August	1st to 10th	Day	45% 8% 19% 20% 6%	4409
	11th to 20th	Day	47% 7% 20% 21% 6%	4162
	21st to end	Day	44% 6% 16% 20% 14% 1	4181
September	1st to 10th	Day	40% 4 18% 26% 11% 1	2280
	11th to 20th	Day	38% 4 17% 29% 10% 1	2167
	21st to end	Day	46% 4 13% 27% 10%	2090
October	1st to 10th	Day	47% 7% 13% 26% 6%	3330
	11th to 20th	Day	49% 7% 17% 24% 3	2965
	21st to end	Day	47% 6% 20% 20% 7% 1	3081
November	1st to 10th	Day	53% 4 13% 20% 9% 1	1761
	11th to 20th	Day	57% 4 11% 19% 9%	1725
	21st to end	Day	62% 5% 11% 16% 6%	1600
December	1st to 10th	Day	67% 4 9% 17% 5%	2387
	11th to 20th	Day	57% 4 9% 18% 12%	2787
	21st to end	Day	62% 4 9% 15% 10%	3960
January	1st to 10th	Night	68% 4 11% 13% 4	6349
	11th to 20th	Night	65% 4 10% 15% 5% 1	6360
	21st to end	Night	57% 4 10% 16% 14%	6996
February	1st to 10th	Night	57% 3 10% 18% 10% 1	2727
	11th to 20th	Night	59% 4 9% 17% 10% 1	2412
	21st to end	Night	55% 4 8% 18% 13% 2	1980
March	1st to 10th	Night	65% 3 8% 11% 10% 3	5374
	11th to 20th	Night	54% 5% 14% 15% 10% 2	5308
	21st to end	Night	54% 5% 6% 22% 10% 2	4962
April	1st to 10th	Night	54% 3 9% 17% 16% 2	2000
	11th to 20th	Night	48% 4 9% 22% 14% 2	1945
	21st to end	Night	51% 4 8% 20% 15% 3	1800
May	1st to 10th	Night	54% 4 13% 19% 9% 2	2711
	11th to 20th	Night	46% 4 16% 20% 12% 2	2502
	21st to end	Night	49% 4 13% 17% 15% 1	2739
June	1st to 10th	Night	47% 5% 14% 22% 12% 1	1520
	11th to 20th	Night	46% 5% 13% 20% 13% 4	1520
	21st to end	Night	50% 5% 13% 18% 13%	1520
July	1st to 10th	Night	45% 7% 19% 19% 9%	2480
	11th to 20th	Night	42% 6% 20% 25% 6%	2472
	21st to end	Night	36% 5% 20% 27% 11%	2651
August	1st to 10th	Night	44% 7% 17% 24% 8%	2496
	11th to 20th	Night	45% 6% 19% 22% 7%	2699
	21st to end	Night	45% 6% 13% 24% 12%	3471
September	1st to 10th	Night	38% 5% 17% 27% 12% 1	1900
	11th to 20th	Night	36% 3 18% 32% 10% 1	2012
	21st to end	Night	42% 4 11% 31% 12%	2090
October	1st to 10th	Night	49% 6% 12% 24% 9%	3627
	11th to 20th	Night	45% 6% 16% 28% 6%	3953
	21st to end	Night	45% 5% 18% 19% 11% 1	4467
November	1st to 10th	Night	52% 5% 13% 22% 8% 1	2537
	11th to 20th	Night	54% 4 12% 19% 10% 1	2671
	21st to end	Night	60% 4 11% 17% 8%	2800
December	1st to 10th	Night	61% 5% 14% 15% 4	4778
	11th to 20th	Night	61% 4 8% 19% 8%	5389
	21st to end	Night	63% 3 7% 17% 11% 1	6996

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	28% 13% 39% 16% 5% 1	200
	11th to 20th	Day	28% 12% 37% 18% 6% 1	200
	21st to end	Day	17% 14% 39% 22% 9%	220
February	1st to 10th	Day	27% 23% 36% 11% 2	235
	11th to 20th	Day	24% 21% 36% 17% 2	423
	21st to end	Day	26% 17% 36% 17% 5%	414
March	1st to 10th	Day	25% 16% 32% 21% 6%	500
	11th to 20th	Day	24% 19% 35% 17% 5% 1	500
	21st to end	Day	27% 21% 28% 17% 6% 2	550
April	1st to 10th	Day	32% 13% 28% 21% 6% 1	500
	11th to 20th	Day	28% 17% 29% 18% 5% 3	492
	21st to end	Day	31% 14% 37% 12% 4 2	500
May	1st to 10th	Day	30% 13% 33% 17% 6% 1	503
	11th to 20th	Day	22% 14% 30% 25% 8% 2	487
	21st to end	Day	23% 15% 36% 17% 8% 1	529
June	1st to 10th	Day	22% 12% 36% 20% 7% 2	490
	11th to 20th	Day	20% 13% 32% 21% 11% 1	490
	21st to end	Day	27% 12% 29% 22% 10% 2	490
July	1st to 10th	Day	16% 9% 33% 28% 12% 2	485
	11th to 20th	Day	17% 9% 31% 32% 9% 2	484
	21st to end	Day	15% 8% 30% 28% 16% 3	532
August	1st to 10th	Day	16% 7% 27% 31% 16% 3	486
	11th to 20th	Day	17% 5% 24% 33% 16% 5%	479
	21st to end	Day	17% 11% 28% 22% 16% 6%	539
September	1st to 10th	Day	18% 10% 33% 22% 12% 5%	490
	11th to 20th	Day	18% 9% 24% 26% 16% 7%	490
	21st to end	Day	24% 11% 26% 21% 12% 6%	490
October	1st to 10th	Day	25% 12% 29% 20% 12% 2	490
	11th to 20th	Day	27% 12% 32% 18% 10% 1	437
	21st to end	Day	33% 11% 29% 20% 7%	429
November	1st to 10th	Day	29% 13% 31% 20% 6% 1	395
	11th to 20th	Day	28% 13% 30% 22% 6%	325
	21st to end	Day	29% 18% 32% 18% 3 2	200
December	1st to 10th	Day	34% 12% 30% 17% 8% 1	200
	11th to 20th	Day	30% 17% 35% 17% 2 1	200
	21st to end	Day	33% 15% 30% 16% 5% 2	220
January	1st to 10th	Night	29% 10% 33% 24% 4	800
	11th to 20th	Night	27% 13% 32% 22% 7%	800
	21st to end	Night	17% 9% 34% 33% 6% 1	880
February	1st to 10th	Night	20% 10% 38% 27% 5% 1	800
	11th to 20th	Night	21% 14% 38% 22% 5%	783
	21st to end	Night	23% 11% 32% 27% 6%	660
March	1st to 10th	Night	24% 12% 32% 28% 4	800
	11th to 20th	Night	23% 13% 35% 23% 5% 1	800
	21st to end	Night	23% 13% 32% 24% 7% 1	880
April	1st to 10th	Night	30% 12% 28% 24% 6%	800
	11th to 20th	Night	27% 11% 30% 27% 4	761
	21st to end	Night	29% 13% 31% 22% 5%	600
May	1st to 10th	Night	28% 12% 27% 27% 5% 1	472
	11th to 20th	Night	24% 8% 30% 30% 8%	376
	21st to end	Night	22% 6% 36% 26% 9%	411
June	1st to 10th	Night	24% 4 27% 36% 8%	380
	11th to 20th	Night	22% 5% 23% 38% 10% 1	380
	21st to end	Night	23% 4 24% 35% 13%	380
July	1st to 10th	Night	15% 5% 28% 36% 16%	370
	11th to 20th	Night	15% 3 24% 40% 17% 1	368
	21st to end	Night	16% 5% 23% 40% 16% 1	416
August	1st to 10th	Night	13% 4 17% 47% 18% 1	378
	11th to 20th	Night	17% 4 21% 36% 20% 2	490
	21st to end	Night	19% 6% 25% 31% 19% 1	831
September	1st to 10th	Night	17% 4 28% 36% 13% 1	760
	11th to 20th	Night	17% 7% 24% 31% 20% 2	760
	21st to end	Night	22% 6% 27% 27% 15% 2	760
October	1st to 10th	Night	22% 9% 28% 30% 10%	760
	11th to 20th	Night	26% 9% 28% 26% 10% 1	760
	21st to end	Night	31% 8% 32% 22% 6%	836
November	1st to 10th	Night	26% 10% 31% 26% 7% 1	780
	11th to 20th	Night	26% 11% 30% 23% 10% 1	800
	21st to end	Night	32% 14% 24% 25% 5% 1	800
December	1st to 10th	Night	29% 8% 29% 25% 9%	860
	11th to 20th	Night	28% 12% 32% 21% 6% 1	855
	21st to end	Night	33% 10% 28% 22% 5% 1	880

Page generated at 2025-05-08 09:33:55. Version ac07

Copyright © 2025 Attilla Danko.