Parc de la Frayère
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Parc de la Frayère clear sky chart from 2005-11-06 to 2026-08-30.

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	16% 9% 3 8% 5% 5% 5% 4 6% 7% 32%	144328
	Night	17% 11% 4 9% 5% 5% 4 3 5% 6% 30%	137915
Transparency	Day	49% 6% 13% 21% 10% 1	147788
	Night	54% 5% 11% 19% 10% 1	142544
Seeing	Day	21% 12% 28% 24% 12% 3	16852
	Night	23% 9% 29% 29% 10% 1	25716

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% 17% 6% 13% 5% 5% 4 3 3 4 23%	4661
	11th to 20th	Day	12% 15% 6% 13% 6% 6% 4 3 4 6% 23%	4650
	21st to end	Day	10% 13% 5% 11% 8% 8% 7% 4 5% 5% 24%	5124
February	1st to 10th	Day	14% 15% 4 10% 5% 5% 5% 3 4 6% 28%	1823
	11th to 20th	Day	13% 12% 5% 11% 6% 4 5% 5% 6% 5% 27%	1963
	21st to end	Day	17% 16% 4 9% 7% 4 4 2 5% 6% 27%	1730
March	1st to 10th	Day	18% 12% 4 11% 7% 5% 5% 3 4 5% 26%	4576
	11th to 20th	Day	12% 13% 4 9% 5% 5% 4 3 6% 7% 31%	4791
	21st to end	Day	17% 11% 4 10% 5% 4 4 3 5% 5% 33%	6102
April	1st to 10th	Day	22% 11% 3 9% 5% 4 5% 3 4 6% 31%	2520
	11th to 20th	Day	20% 9% 3 7% 4 4 3 3 4 5% 37%	2494
	21st to end	Day	21% 9% 3 8% 4 4 4 4 5% 6% 33%	2706
May	1st to 10th	Day	22% 10% 4 9% 5% 4 5% 4 6% 7% 25%	8089
	11th to 20th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 8% 30%	8221
	21st to end	Day	20% 9% 3 7% 4 4 4 4 5% 7% 33%	9060
June	1st to 10th	Day	20% 8% 3 7% 5% 5% 5% 3 6% 8% 31%	2940
	11th to 20th	Day	15% 6% 3 6% 5% 4 4 4 6% 9% 38%	2940
	21st to end	Day	18% 8% 3 8% 6% 5% 5% 4 6% 8% 31%	2940
July	1st to 10th	Day	11% 6% 2 7% 5% 5% 5% 4 7% 9% 38%	8280
	11th to 20th	Day	10% 4 2 6% 4 4 5% 4 6% 9% 45%	8280
	21st to end	Day	10% 6% 2 6% 4 4 5% 4 7% 10% 42%	8993
August	1st to 10th	Day	13% 6% 2 8% 5% 5% 6% 5% 7% 10% 33%	4703
	11th to 20th	Day	13% 6% 3 8% 5% 4 4 4 6% 9% 38%	4276
	21st to end	Day	15% 6% 2 6% 4 4 4 4 6% 8% 40%	4420
September	1st to 10th	Day	11% 5% 2 6% 5% 4 5% 5% 6% 9% 43%	2400
	11th to 20th	Day	13% 5% 2 5% 3 3 4 3 6% 7% 49%	2305
	21st to end	Day	15% 6% 2 7% 4 4 5% 4 5% 8% 41%	2200
October	1st to 10th	Day	18% 6% 3 6% 5% 5% 4 4 5% 8% 36%	2080
	11th to 20th	Day	16% 9% 3 8% 5% 6% 5% 5% 6% 7% 30%	1940
	21st to end	Day	24% 9% 3 7% 4 4 4 3 5% 5% 31%	1980
November	1st to 10th	Day	17% 11% 3 7% 5% 4 5% 4 6% 6% 31%	1851
	11th to 20th	Day	17% 11% 3 9% 5% 5% 5% 5% 5% 5% 30%	1816
	21st to end	Day	22% 13% 3 8% 5% 4 6% 4 4 6% 25%	1680
December	1st to 10th	Day	20% 19% 5% 12% 5% 4 4 3 4 5% 18%	2680
	11th to 20th	Day	19% 13% 4 10% 4 4 5% 4 5% 6% 26%	3066
	21st to end	Day	23% 13% 4 10% 6% 5% 6% 5% 6% 5% 19%	4048
January	1st to 10th	Night	13% 18% 7% 15% 6% 5% 4 3 4 5% 22%	8234
	11th to 20th	Night	11% 16% 7% 16% 8% 6% 5% 3 4 5% 18%	8235
	21st to end	Night	11% 13% 4 12% 9% 6% 5% 3 5% 6% 25%	9057
February	1st to 10th	Night	14% 14% 6% 12% 7% 5% 4 3 5% 6% 23%	2793
	11th to 20th	Night	14% 13% 5% 9% 5% 6% 4 3 5% 5% 30%	2542
	21st to end	Night	15% 15% 3 9% 5% 5% 4 3 4 6% 31%	2076
March	1st to 10th	Night	22% 12% 4 8% 5% 4 4 3 4 5% 30%	5484
	11th to 20th	Night	14% 14% 4 8% 5% 5% 5% 4 5% 7% 30%	5386
	21st to end	Night	15% 12% 4 9% 6% 5% 4 3 4 5% 31%	5072
April	1st to 10th	Night	23% 10% 3 7% 4 4 4 3 4 6% 31%	2100
	11th to 20th	Night	22% 9% 3 7% 4 4 4 3 4 6% 34%	2075
	21st to end	Night	21% 9% 3 6% 4 4 4 3 5% 5% 35%	1912
May	1st to 10th	Night	22% 9% 4 8% 5% 5% 5% 4 7% 7% 25%	4864
	11th to 20th	Night	20% 9% 3 8% 5% 4 5% 3 6% 7% 29%	4639
	21st to end	Night	18% 9% 3 7% 5% 4 4 4 6% 7% 32%	5114
June	1st to 10th	Night	21% 7% 3 8% 4 4 5% 4 5% 7% 33%	1680
	11th to 20th	Night	15% 7% 3 7% 4 4 5% 3 8% 7% 37%	1680
	21st to end	Night	18% 7% 2 8% 5% 6% 5% 4 5% 8% 33%	1680
July	1st to 10th	Night	13% 7% 3 7% 5% 5% 6% 4 7% 10% 35%	4680
	11th to 20th	Night	12% 6% 2 6% 4 4 5% 4 6% 8% 44%	4680
	21st to end	Night	11% 6% 3 7% 5% 5% 5% 4 6% 8% 40%	5084
August	1st to 10th	Night	14% 8% 3 8% 5% 5% 5% 3 6% 7% 36%	2666
	11th to 20th	Night	14% 7% 3 8% 5% 5% 5% 4 6% 7% 38%	2954
	21st to end	Night	16% 6% 3 7% 5% 5% 4 4 6% 7% 38%	3677
September	1st to 10th	Night	11% 5% 2 7% 5% 4 4 4 6% 7% 44%	2000
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 5% 7% 50%	2095
	21st to end	Night	16% 7% 3 6% 5% 4 3 3 5% 6% 43%	2200
October	1st to 10th	Night	17% 6% 2 7% 4 4 4 3 5% 7% 40%	2315
	11th to 20th	Night	20% 8% 3 7% 5% 4 4 3 5% 6% 35%	2458
	21st to end	Night	22% 8% 3 8% 5% 4 4 3 5% 5% 31%	2860
November	1st to 10th	Night	20% 9% 3 7% 5% 5% 4 3 5% 5% 33%	2667
	11th to 20th	Night	19% 11% 3 8% 5% 5% 4 3 5% 6% 32%	2798
	21st to end	Night	22% 13% 4 9% 6% 4 4 3 4 5% 26%	2940
December	1st to 10th	Night	17% 17% 6% 13% 6% 5% 5% 3 5% 5% 18%	4720
	11th to 20th	Night	22% 13% 4 10% 5% 4 4 3 6% 5% 24%	5348
	21st to end	Night	24% 15% 5% 9% 4 3 4 4 6% 5% 21%	7150

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	62% 6% 11% 17% 4	4662
	11th to 20th	Day	62% 5% 9% 14% 9% 1	4680
	21st to end	Day	59% 5% 10% 14% 11% 1	5124
February	1st to 10th	Day	59% 5% 9% 19% 7% 2	1823
	11th to 20th	Day	57% 7% 11% 16% 9% 1	1972
	21st to end	Day	59% 4 10% 16% 10% 2	1730
March	1st to 10th	Day	59% 6% 8% 14% 11% 3	4579
	11th to 20th	Day	51% 7% 16% 14% 10% 2	4791
	21st to end	Day	53% 5% 8% 16% 16% 2	6102
April	1st to 10th	Day	56% 5% 8% 18% 11% 2	2520
	11th to 20th	Day	50% 4 9% 22% 13% 1	2494
	21st to end	Day	53% 5% 9% 18% 12% 3	2706
May	1st to 10th	Day	57% 6% 9% 20% 8% 1	8101
	11th to 20th	Day	49% 8% 15% 19% 8% 1	8225
	21st to end	Day	49% 6% 11% 23% 10% 1	9061
June	1st to 10th	Day	50% 6% 11% 20% 11% 2	2940
	11th to 20th	Day	41% 7% 12% 25% 12% 2	2940
	21st to end	Day	51% 7% 13% 20% 9% 1	2940
July	1st to 10th	Day	41% 6% 15% 27% 11%	8210
	11th to 20th	Day	34% 6% 16% 32% 12%	8205
	21st to end	Day	36% 7% 18% 31% 8%	8795
August	1st to 10th	Day	45% 7% 18% 22% 7%	4689
	11th to 20th	Day	41% 7% 19% 25% 7%	4318
	21st to end	Day	42% 6% 16% 22% 14%	4420
September	1st to 10th	Day	36% 8% 15% 30% 11% 1	2400
	11th to 20th	Day	34% 6% 13% 33% 14% 1	2305
	21st to end	Day	42% 7% 14% 25% 12%	2200
October	1st to 10th	Day	43% 6% 15% 27% 8%	3392
	11th to 20th	Day	44% 6% 18% 25% 7%	3143
	21st to end	Day	44% 6% 19% 22% 9% 1	3180
November	1st to 10th	Day	50% 7% 13% 21% 9% 1	1851
	11th to 20th	Day	52% 7% 11% 19% 11%	1816
	21st to end	Day	59% 8% 13% 14% 6%	1680
December	1st to 10th	Day	68% 4 8% 16% 4	2680
	11th to 20th	Day	59% 5% 9% 17% 10%	3066
	21st to end	Day	65% 6% 12% 11% 6%	4048
January	1st to 10th	Night	65% 5% 11% 13% 5% 1	8234
	11th to 20th	Night	67% 7% 8% 12% 6%	8280
	21st to end	Night	60% 5% 9% 13% 13%	9057
February	1st to 10th	Night	62% 5% 9% 16% 8% 1	2793
	11th to 20th	Night	58% 5% 8% 18% 10%	2544
	21st to end	Night	55% 5% 8% 17% 12% 1	2076
March	1st to 10th	Night	58% 4 8% 14% 11% 5%	5494
	11th to 20th	Night	53% 6% 13% 15% 13% 2	5387
	21st to end	Night	55% 5% 6% 20% 11% 2	5072
April	1st to 10th	Night	55% 4 7% 18% 14% 2	2100
	11th to 20th	Night	53% 4 7% 20% 14% 2	2075
	21st to end	Night	50% 4 8% 19% 15% 3	1912
May	1st to 10th	Night	56% 7% 11% 17% 8% 2	4870
	11th to 20th	Night	52% 7% 10% 22% 8% 1	4640
	21st to end	Night	51% 5% 9% 19% 15% 1	5115
June	1st to 10th	Night	48% 6% 9% 22% 14% 1	1680
	11th to 20th	Night	45% 7% 11% 21% 14% 3	1680
	21st to end	Night	49% 7% 10% 19% 14% 1	1680
July	1st to 10th	Night	42% 6% 18% 20% 13% 1	4640
	11th to 20th	Night	37% 5% 17% 29% 11%	4632
	21st to end	Night	41% 6% 16% 27% 9%	4967
August	1st to 10th	Night	47% 7% 13% 25% 9%	2656
	11th to 20th	Night	45% 7% 17% 23% 8%	2978
	21st to end	Night	45% 6% 13% 21% 14% 1	3677
September	1st to 10th	Night	38% 7% 12% 27% 15% 1	2000
	11th to 20th	Night	35% 5% 13% 32% 13% 1	2095
	21st to end	Night	40% 8% 10% 27% 15%	2200
October	1st to 10th	Night	43% 6% 13% 26% 11% 1	3783
	11th to 20th	Night	45% 5% 11% 30% 9%	3994
	21st to end	Night	48% 4 15% 19% 12% 2	4610
November	1st to 10th	Night	53% 5% 12% 22% 8% 1	2667
	11th to 20th	Night	53% 6% 11% 19% 10% 1	2798
	21st to end	Night	61% 5% 11% 17% 7%	2940
December	1st to 10th	Night	69% 5% 11% 12% 4	4720
	11th to 20th	Night	61% 5% 8% 14% 11%	5348
	21st to end	Night	64% 4 8% 14% 9%	7150

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	27% 13% 32% 18% 10%	220
	11th to 20th	Day	25% 17% 34% 18% 5%	220
	21st to end	Day	18% 13% 35% 23% 10% 2	242
February	1st to 10th	Day	25% 15% 36% 19% 4	295
	11th to 20th	Day	21% 16% 32% 26% 4	451
	21st to end	Day	25% 13% 34% 24% 4	446
March	1st to 10th	Day	22% 15% 31% 24% 9%	540
	11th to 20th	Day	23% 14% 35% 21% 6% 1	540
	21st to end	Day	27% 13% 32% 21% 7% 1	594
April	1st to 10th	Day	28% 16% 28% 19% 7% 1	540
	11th to 20th	Day	28% 18% 24% 20% 7% 2	532
	21st to end	Day	26% 14% 32% 18% 9% 1	540
May	1st to 10th	Day	24% 11% 32% 21% 10% 2	543
	11th to 20th	Day	19% 12% 27% 25% 14% 3	567
	21st to end	Day	21% 13% 31% 24% 9% 2	617
June	1st to 10th	Day	21% 11% 26% 29% 11% 2	570
	11th to 20th	Day	16% 12% 26% 31% 13% 2	570
	21st to end	Day	22% 11% 25% 26% 14% 3	570
July	1st to 10th	Day	13% 8% 26% 30% 18% 5%	565
	11th to 20th	Day	12% 9% 29% 31% 15% 4	564
	21st to end	Day	13% 8% 25% 32% 18% 4	620
August	1st to 10th	Day	14% 5% 25% 30% 20% 6%	566
	11th to 20th	Day	12% 6% 21% 32% 21% 8%	559
	21st to end	Day	15% 9% 23% 26% 18% 10%	619
September	1st to 10th	Day	12% 9% 27% 29% 16% 7%	530
	11th to 20th	Day	13% 7% 19% 28% 20% 13%	530
	21st to end	Day	18% 9% 26% 23% 18% 6%	530
October	1st to 10th	Day	19% 13% 26% 23% 15% 4	530
	11th to 20th	Day	22% 12% 30% 23% 11% 2	497
	21st to end	Day	30% 11% 26% 24% 8%	462
November	1st to 10th	Day	26% 15% 30% 19% 9%	425
	11th to 20th	Day	23% 15% 31% 21% 8% 1	356
	21st to end	Day	34% 13% 30% 15% 8%	220
December	1st to 10th	Day	29% 10% 28% 19% 11% 3	220
	11th to 20th	Day	25% 20% 34% 15% 4 1	220
	21st to end	Day	31% 17% 27% 19% 4 2	242
January	1st to 10th	Night	28% 10% 32% 26% 5%	840
	11th to 20th	Night	25% 11% 33% 24% 6%	840
	21st to end	Night	19% 10% 33% 30% 6% 1	924
February	1st to 10th	Night	21% 10% 35% 28% 5% 1	840
	11th to 20th	Night	20% 11% 38% 25% 5% 1	823
	21st to end	Night	21% 11% 33% 31% 4	692
March	1st to 10th	Night	25% 9% 32% 28% 5%	840
	11th to 20th	Night	25% 12% 31% 25% 7%	840
	21st to end	Night	23% 10% 31% 28% 7%	924
April	1st to 10th	Night	29% 12% 26% 27% 6%	840
	11th to 20th	Night	26% 13% 29% 26% 6%	831
	21st to end	Night	28% 11% 30% 24% 6% 1	652
May	1st to 10th	Night	26% 8% 32% 27% 7% 1	494
	11th to 20th	Night	23% 9% 28% 31% 8% 1	414
	21st to end	Night	19% 9% 36% 28% 9%	455
June	1st to 10th	Night	22% 6% 27% 36% 9% 1	420
	11th to 20th	Night	20% 5% 28% 35% 12%	420
	21st to end	Night	18% 7% 26% 35% 14%	420
July	1st to 10th	Night	11% 6% 30% 38% 15%	410
	11th to 20th	Night	12% 3 25% 45% 14% 1	408
	21st to end	Night	14% 5% 21% 44% 16%	460
August	1st to 10th	Night	13% 5% 18% 43% 19% 2	418
	11th to 20th	Night	13% 4 20% 38% 23% 2	610
	21st to end	Night	16% 5% 21% 37% 20% 2	917
September	1st to 10th	Night	15% 5% 24% 40% 16% 1	800
	11th to 20th	Night	16% 5% 20% 34% 23% 2	800
	21st to end	Night	18% 6% 26% 32% 15% 3	800
October	1st to 10th	Night	20% 7% 28% 31% 13% 1	800
	11th to 20th	Night	25% 8% 28% 29% 9% 1	800
	21st to end	Night	27% 10% 31% 26% 7%	880
November	1st to 10th	Night	25% 11% 31% 24% 8%	820
	11th to 20th	Night	25% 10% 33% 23% 9% 1	840
	21st to end	Night	29% 12% 31% 21% 7%	840
December	1st to 10th	Night	28% 11% 30% 25% 6%	840
	11th to 20th	Night	28% 13% 32% 21% 6% 1	840
	21st to end	Night	31% 11% 30% 20% 7%	924

Page generated at 2026-08-27 04:07:09. Version ac07

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