CAAS - Parc Ecoforestier Johnville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the CAAS - Parc Ecoforestier Johnville clear sky chart from 2005-11-06 to 2026-03-18.

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	18% 13% 4 10% 6% 5% 5% 4 5% 6% 25%	130917
	Night	18% 15% 5% 11% 6% 5% 4 3 4 5% 24%	130459
Transparency	Day	58% 6% 11% 17% 7% 1	134385
	Night	62% 6% 10% 15% 7% 1	135078
Seeing	Day	28% 18% 28% 18% 7% 2	16329
	Night	27% 15% 26% 23% 8% 1	25321

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	13% 21% 9% 17% 8% 8% 4 3 3 3 11%	4661
	11th to 20th	Day	8% 19% 9% 25% 12% 6% 4 3 3 3 9%	4650
	21st to end	Day	8% 16% 8% 14% 10% 13% 6% 4 4 4 13%	5124
February	1st to 10th	Day	14% 18% 5% 16% 10% 6% 5% 3 4 3 16%	1754
	11th to 20th	Day	13% 20% 9% 16% 9% 4 4 3 4 3 16%	2048
	21st to end	Day	12% 19% 6% 11% 8% 6% 5% 3 4 5% 20%	1730
March	1st to 10th	Day	19% 17% 7% 14% 6% 4 5% 2 3 4 19%	4576
	11th to 20th	Day	14% 18% 5% 11% 6% 4 4 3 4 5% 26%	4775
	21st to end	Day	21% 16% 6% 10% 5% 4 3 2 3 4 26%	5868
April	1st to 10th	Day	22% 17% 4 9% 4 4 3 3 4 5% 25%	2400
	11th to 20th	Day	20% 15% 3 7% 4 4 4 3 3 5% 33%	2423
	21st to end	Day	24% 15% 4 6% 4 4 4 3 5% 6% 27%	2600
May	1st to 10th	Day	29% 12% 4 9% 6% 5% 4 3 5% 5% 20%	5948
	11th to 20th	Day	21% 9% 3 8% 5% 5% 5% 4 5% 7% 28%	6318
	21st to end	Day	20% 9% 3 7% 5% 5% 5% 4 6% 7% 28%	6949
June	1st to 10th	Day	26% 9% 3 7% 5% 5% 5% 3 6% 7% 26%	2800
	11th to 20th	Day	18% 7% 3 7% 5% 4 5% 4 6% 8% 33%	2800
	21st to end	Day	21% 8% 3 8% 5% 5% 5% 4 5% 7% 28%	2800
July	1st to 10th	Day	16% 8% 3 8% 6% 6% 6% 5% 8% 9% 26%	6360
	11th to 20th	Day	14% 7% 2 7% 5% 5% 6% 5% 7% 9% 33%	6360
	21st to end	Day	15% 7% 2 6% 4 4 4 4 6% 9% 39%	6926
August	1st to 10th	Day	18% 8% 3 8% 5% 5% 6% 4 6% 8% 28%	4504
	11th to 20th	Day	18% 8% 3 8% 5% 5% 6% 5% 8% 10% 25%	4175
	21st to end	Day	20% 7% 2 6% 3 4 4 4 7% 8% 35%	4355
September	1st to 10th	Day	17% 7% 2 6% 4 4 4 4 5% 7% 40%	2400
	11th to 20th	Day	18% 6% 2 6% 3 3 4 3 5% 7% 42%	2232
	21st to end	Day	20% 8% 2 5% 4 4 4 4 5% 8% 34%	2200
October	1st to 10th	Day	23% 10% 3 5% 4 4 5% 3 6% 7% 30%	2190
	11th to 20th	Day	19% 13% 4 8% 4 4 4 4 6% 6% 27%	1869
	21st to end	Day	25% 20% 4 7% 4 3 3 3 4 4 23%	1980
November	1st to 10th	Day	20% 18% 4 7% 5% 4 4 3 4 4 27%	1851
	11th to 20th	Day	18% 19% 6% 11% 5% 4 4 3 4 4 22%	1890
	21st to end	Day	19% 20% 6% 11% 5% 3 4 4 5% 5% 17%	1727
December	1st to 10th	Day	15% 23% 7% 20% 8% 5% 3 3 2 3 11%	2593
	11th to 20th	Day	18% 19% 6% 14% 5% 4 4 2 4 4 19%	3033
	21st to end	Day	19% 18% 5% 15% 4 5% 4 3 4 4 18%	4048
January	1st to 10th	Night	12% 23% 9% 18% 9% 6% 4 3 2 3 12%	8234
	11th to 20th	Night	11% 22% 10% 22% 9% 6% 4 3 3 3 9%	8235
	21st to end	Night	9% 16% 6% 16% 11% 10% 5% 4 4 4 16%	9057
February	1st to 10th	Night	13% 19% 6% 15% 8% 6% 4 3 4 4 18%	2862
	11th to 20th	Night	12% 18% 7% 16% 8% 6% 4 2 3 4 18%	2458
	21st to end	Night	14% 20% 5% 10% 7% 6% 4 3 3 4 24%	2076
March	1st to 10th	Night	21% 18% 6% 11% 5% 6% 4 2 3 3 21%	5484
	11th to 20th	Night	16% 19% 5% 10% 5% 4 5% 3 5% 6% 23%	5325
	21st to end	Night	18% 20% 5% 11% 6% 4 3 2 3 3 25%	5061
April	1st to 10th	Night	23% 14% 5% 8% 4 3 4 3 4 4 27%	2000
	11th to 20th	Night	23% 13% 3 6% 5% 4 4 3 4 4 32%	1925
	21st to end	Night	23% 13% 3 7% 5% 3 3 3 4 6% 29%	1800
May	1st to 10th	Night	29% 10% 3 9% 4 5% 4 3 4 6% 22%	4022
	11th to 20th	Night	26% 8% 2 8% 5% 5% 4 3 5% 5% 28%	3575
	21st to end	Night	20% 9% 3 7% 5% 5% 4 4 5% 7% 31%	3926
June	1st to 10th	Night	28% 7% 3 7% 4 3 4 3 6% 7% 28%	1600
	11th to 20th	Night	20% 7% 3 6% 4 4 4 5% 6% 7% 34%	1600
	21st to end	Night	20% 8% 4 6% 5% 5% 5% 5% 6% 7% 31%	1600
July	1st to 10th	Night	15% 8% 3 8% 6% 6% 5% 5% 6% 8% 29%	3600
	11th to 20th	Night	18% 8% 3 7% 4 4 4 3 6% 7% 36%	3600
	21st to end	Night	14% 7% 2 7% 5% 5% 5% 4 7% 8% 37%	3926
August	1st to 10th	Night	24% 7% 3 7% 4 5% 4 3 5% 7% 31%	2613
	11th to 20th	Night	17% 8% 3 9% 5% 5% 5% 5% 6% 8% 30%	2872
	21st to end	Night	19% 7% 2 6% 4 4 4 3 5% 7% 39%	3540
September	1st to 10th	Night	17% 8% 2 7% 4 4 4 3 5% 6% 39%	2000
	11th to 20th	Night	16% 6% 2 5% 3 4 3 4 4 6% 47%	2167
	21st to end	Night	21% 7% 2 4 3 3 4 3 5% 7% 40%	2200
October	1st to 10th	Night	21% 9% 3 6% 5% 4 4 3 5% 6% 35%	2208
	11th to 20th	Night	22% 11% 4 8% 4 5% 4 3 4 5% 29%	2530
	21st to end	Night	26% 13% 4 7% 4 4 4 4 5% 4 26%	2860
November	1st to 10th	Night	23% 16% 4 8% 5% 4 4 3 4 5% 25%	2667
	11th to 20th	Night	18% 18% 6% 11% 5% 4 3 2 4 5% 25%	2730
	21st to end	Night	21% 19% 5% 13% 6% 3 3 2 3 5% 20%	2888
December	1st to 10th	Night	15% 25% 13% 18% 7% 4 3 2 2 3 8%	4720
	11th to 20th	Night	18% 22% 6% 16% 6% 4 3 3 3 3 16%	5348
	21st to end	Night	19% 20% 5% 11% 6% 5% 4 2 3 4 20%	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	79% 5% 9% 6% 1	4662
	11th to 20th	Day	81% 6% 4 7% 3	4680
	21st to end	Day	75% 4 6% 8% 7%	5124
February	1st to 10th	Day	74% 4 6% 11% 5% 1	1754
	11th to 20th	Day	73% 4 8% 9% 4 1	2057
	21st to end	Day	67% 5% 8% 13% 6% 1	1730
March	1st to 10th	Day	70% 5% 7% 9% 7% 3	4579
	11th to 20th	Day	60% 4 13% 13% 9% 1	4775
	21st to end	Day	63% 4 6% 13% 12% 1	5868
April	1st to 10th	Day	63% 5% 8% 16% 8% 2	2400
	11th to 20th	Day	55% 5% 7% 20% 12% 1	2423
	21st to end	Day	59% 6% 8% 16% 9% 2	2600
May	1st to 10th	Day	65% 7% 9% 14% 5%	5959
	11th to 20th	Day	53% 9% 14% 15% 7% 1	6322
	21st to end	Day	51% 9% 11% 19% 9% 1	6949
June	1st to 10th	Day	56% 8% 11% 17% 7% 1	2800
	11th to 20th	Day	47% 7% 13% 22% 10% 1	2800
	21st to end	Day	55% 7% 11% 18% 7%	2800
July	1st to 10th	Day	50% 8% 15% 20% 6%	6290
	11th to 20th	Day	44% 9% 14% 27% 7%	6285
	21st to end	Day	41% 7% 14% 31% 7%	6728
August	1st to 10th	Day	52% 8% 16% 20% 5%	4490
	11th to 20th	Day	50% 10% 17% 18% 4	4214
	21st to end	Day	45% 8% 15% 19% 12% 2	4355
September	1st to 10th	Day	42% 8% 13% 27% 8%	2400
	11th to 20th	Day	42% 5% 13% 27% 13%	2232
	21st to end	Day	47% 8% 13% 22% 10% 1	2200
October	1st to 10th	Day	49% 6% 15% 23% 7%	3567
	11th to 20th	Day	54% 6% 14% 23% 4	3020
	21st to end	Day	55% 5% 14% 19% 7% 1	3180
November	1st to 10th	Day	61% 7% 10% 16% 6% 1	1851
	11th to 20th	Day	66% 5% 9% 11% 8% 1	1890
	21st to end	Day	69% 7% 12% 10% 2	1727
December	1st to 10th	Day	80% 4 8% 6% 2	2593
	11th to 20th	Day	70% 4 6% 15% 5%	3033
	21st to end	Day	70% 5% 6% 10% 8%	4048
January	1st to 10th	Night	78% 4 8% 7% 2	8234
	11th to 20th	Night	81% 5% 6% 5% 3	8280
	21st to end	Night	72% 4 7% 9% 8%	9057
February	1st to 10th	Night	70% 5% 8% 12% 5%	2862
	11th to 20th	Night	71% 4 8% 12% 5%	2460
	21st to end	Night	65% 5% 8% 13% 8% 1	2076
March	1st to 10th	Night	68% 4 8% 11% 7% 2	5494
	11th to 20th	Night	61% 6% 14% 12% 6% 1	5326
	21st to end	Night	65% 3 6% 15% 10% 1	5061
April	1st to 10th	Night	60% 5% 8% 16% 10% 1	2000
	11th to 20th	Night	54% 6% 10% 19% 11% 1	1925
	21st to end	Night	57% 6% 9% 16% 10% 2	1800
May	1st to 10th	Night	62% 8% 10% 13% 6% 1	4028
	11th to 20th	Night	53% 10% 12% 18% 6% 1	3576
	21st to end	Night	51% 8% 13% 17% 12%	3927
June	1st to 10th	Night	54% 7% 10% 20% 8%	1600
	11th to 20th	Night	47% 8% 12% 21% 10% 2	1600
	21st to end	Night	51% 9% 13% 19% 9%	1600
July	1st to 10th	Night	51% 8% 16% 19% 6%	3560
	11th to 20th	Night	46% 8% 13% 26% 7%	3552
	21st to end	Night	42% 7% 16% 27% 7%	3809
August	1st to 10th	Night	52% 7% 13% 23% 4	2603
	11th to 20th	Night	50% 10% 16% 17% 7%	2899
	21st to end	Night	45% 6% 13% 22% 13% 1	3540
September	1st to 10th	Night	45% 7% 12% 25% 11%	2000
	11th to 20th	Night	38% 6% 15% 29% 11% 1	2167
	21st to end	Night	43% 7% 13% 24% 11% 2	2200
October	1st to 10th	Night	51% 5% 11% 23% 9%	3611
	11th to 20th	Night	55% 5% 11% 23% 6%	4118
	21st to end	Night	53% 6% 13% 19% 8% 1	4610
November	1st to 10th	Night	61% 5% 13% 14% 6% 1	2667
	11th to 20th	Night	62% 5% 10% 13% 8% 2	2730
	21st to end	Night	68% 6% 11% 11% 3	2888
December	1st to 10th	Night	84% 4 6% 6% 1	4720
	11th to 20th	Night	75% 4 5% 10% 5%	5348
	21st to end	Night	68% 6% 7% 12% 7%	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	31% 20% 32% 15% 1	220
	11th to 20th	Day	34% 25% 28% 10% 3 1	220
	21st to end	Day	29% 22% 32% 12% 4	242
February	1st to 10th	Day	33% 28% 24% 12% 2	266
	11th to 20th	Day	31% 24% 32% 11% 2	536
	21st to end	Day	29% 25% 29% 15% 1	446
March	1st to 10th	Day	31% 23% 30% 13% 3	540
	11th to 20th	Day	32% 26% 23% 15% 4	528
	21st to end	Day	37% 21% 22% 13% 6% 1	550
April	1st to 10th	Day	39% 19% 23% 13% 6% 1	500
	11th to 20th	Day	37% 20% 24% 11% 6% 2	492
	21st to end	Day	36% 19% 27% 14% 3 1	500
May	1st to 10th	Day	37% 17% 26% 14% 5% 1	503
	11th to 20th	Day	26% 17% 30% 19% 6% 1	527
	21st to end	Day	24% 20% 30% 21% 5% 1	573
June	1st to 10th	Day	29% 16% 32% 16% 5% 1	530
	11th to 20th	Day	21% 20% 28% 24% 7% 1	530
	21st to end	Day	24% 17% 36% 15% 8% 1	530
July	1st to 10th	Day	20% 13% 30% 27% 8% 1	525
	11th to 20th	Day	15% 13% 40% 24% 6% 2	524
	21st to end	Day	19% 12% 35% 26% 7% 1	576
August	1st to 10th	Day	18% 12% 27% 27% 14% 2	526
	11th to 20th	Day	21% 10% 27% 23% 16% 4	519
	21st to end	Day	24% 14% 22% 24% 11% 5%	583
September	1st to 10th	Day	19% 12% 29% 22% 12% 5%	530
	11th to 20th	Day	19% 12% 21% 22% 18% 8%	530
	21st to end	Day	21% 13% 23% 25% 14% 5%	530
October	1st to 10th	Day	25% 15% 25% 19% 13% 4	530
	11th to 20th	Day	29% 18% 25% 17% 10% 1	457
	21st to end	Day	42% 14% 23% 15% 5%	462
November	1st to 10th	Day	39% 16% 25% 16% 4	425
	11th to 20th	Day	30% 20% 27% 15% 6% 1	430
	21st to end	Day	33% 22% 31% 10% 3	267
December	1st to 10th	Day	33% 17% 31% 15% 4 1	220
	11th to 20th	Day	34% 25% 30% 7% 3	220
	21st to end	Day	38% 19% 27% 11% 4 1	242
January	1st to 10th	Night	29% 22% 30% 17% 2	840
	11th to 20th	Night	29% 22% 29% 16% 4	840
	21st to end	Night	22% 19% 31% 22% 5%	924
February	1st to 10th	Night	23% 20% 31% 22% 3	840
	11th to 20th	Night	24% 23% 33% 17% 3	823
	21st to end	Night	27% 17% 33% 21% 2	692
March	1st to 10th	Night	29% 18% 30% 19% 3	840
	11th to 20th	Night	31% 18% 28% 18% 5%	829
	21st to end	Night	29% 17% 27% 20% 7% 1	880
April	1st to 10th	Night	33% 17% 27% 19% 5%	800
	11th to 20th	Night	31% 16% 27% 20% 7%	741
	21st to end	Night	32% 17% 26% 20% 5%	600
May	1st to 10th	Night	31% 10% 29% 24% 6% 1	594
	11th to 20th	Night	24% 12% 30% 28% 6% 1	394
	21st to end	Night	23% 9% 31% 30% 6% 1	433
June	1st to 10th	Night	33% 7% 24% 30% 7% 1	400
	11th to 20th	Night	23% 9% 22% 34% 12%	400
	21st to end	Night	19% 8% 30% 34% 9%	400
July	1st to 10th	Night	15% 7% 26% 39% 12% 1	390
	11th to 20th	Night	16% 4 27% 38% 14% 1	388
	21st to end	Night	16% 6% 25% 37% 15%	438
August	1st to 10th	Night	18% 4 17% 41% 19% 1	412
	11th to 20th	Night	17% 7% 21% 37% 18% 1	592
	21st to end	Night	20% 7% 21% 34% 17% 2	847
September	1st to 10th	Night	22% 7% 23% 34% 13% 1	800
	11th to 20th	Night	19% 7% 20% 29% 23% 2	800
	21st to end	Night	24% 10% 24% 26% 15% 2	800
October	1st to 10th	Night	27% 10% 23% 26% 14% 1	800
	11th to 20th	Night	29% 14% 23% 25% 8% 1	800
	21st to end	Night	34% 15% 26% 21% 4	880
November	1st to 10th	Night	35% 13% 28% 18% 6%	820
	11th to 20th	Night	29% 18% 27% 18% 7% 1	840
	21st to end	Night	34% 19% 25% 17% 5% 1	840
December	1st to 10th	Night	33% 21% 27% 15% 4	840
	11th to 20th	Night	32% 20% 27% 16% 5%	840
	21st to end	Night	34% 21% 25% 15% 4	924

Page generated at 2026-03-15 02:23:58. Version ac07

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