Ferme Véronneau
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ferme Véronneau clear sky chart from 2005-11-06 to 2026-06-16.

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% 12% 4 10% 6% 5% 5% 4 5% 6% 25%	137550
	Night	16% 15% 5% 12% 7% 5% 4 3 4 5% 24%	134506
Transparency	Day	58% 6% 11% 17% 7% 1	141020
	Night	62% 5% 10% 15% 7% 1	139125
Seeing	Day	28% 19% 28% 16% 7% 2	16707
	Night	27% 17% 27% 21% 7% 1	25610

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	11% 19% 10% 19% 9% 9% 4 3 3 3 11%	4661
	11th to 20th	Day	7% 18% 8% 24% 13% 6% 5% 3 3 4 9%	4650
	21st to end	Day	7% 15% 8% 14% 10% 13% 6% 3 5% 4 14%	5124
February	1st to 10th	Day	13% 17% 7% 16% 9% 7% 6% 3 3 4 16%	1767
	11th to 20th	Day	11% 18% 9% 17% 9% 5% 5% 3 4 5% 15%	2048
	21st to end	Day	10% 19% 7% 12% 8% 6% 6% 3 4 5% 20%	1730
March	1st to 10th	Day	17% 17% 6% 14% 6% 5% 5% 3 4 3 19%	4576
	11th to 20th	Day	13% 19% 5% 11% 5% 4 4 3 5% 5% 27%	4803
	21st to end	Day	20% 16% 5% 11% 5% 4 3 3 3 5% 25%	6005
April	1st to 10th	Day	20% 19% 4 10% 4 4 4 2 4 4 25%	2520
	11th to 20th	Day	19% 15% 4 7% 4 4 3 3 3 5% 31%	2536
	21st to end	Day	23% 14% 4 7% 4 4 4 3 5% 5% 27%	2730
May	1st to 10th	Day	26% 13% 4 8% 6% 5% 5% 4 5% 6% 19%	7713
	11th to 20th	Day	19% 9% 3 8% 6% 6% 5% 4 6% 8% 25%	8221
	21st to end	Day	22% 9% 3 7% 5% 5% 5% 4 6% 7% 29%	9060
June	1st to 10th	Day	26% 9% 2 6% 4 5% 5% 4 5% 7% 26%	2940
	11th to 20th	Day	17% 7% 2 7% 5% 5% 5% 5% 6% 8% 33%	2870
	21st to end	Day	22% 9% 3 7% 5% 5% 5% 5% 6% 7% 28%	2800
July	1st to 10th	Day	16% 8% 3 8% 5% 5% 6% 6% 8% 10% 26%	6360
	11th to 20th	Day	13% 6% 2 6% 5% 5% 6% 5% 8% 10% 33%	6360
	21st to end	Day	15% 6% 2 6% 4 4 5% 4 7% 8% 39%	6926
August	1st to 10th	Day	18% 9% 3 7% 6% 5% 5% 4 6% 8% 28%	4504
	11th to 20th	Day	18% 7% 3 8% 5% 6% 6% 5% 8% 9% 27%	4175
	21st to end	Day	19% 7% 3 5% 4 4 5% 4 5% 9% 36%	4327
September	1st to 10th	Day	16% 6% 2 6% 4 4 5% 3 5% 7% 41%	2400
	11th to 20th	Day	18% 7% 3 5% 3 3 4 3 4 7% 43%	2236
	21st to end	Day	19% 8% 2 5% 4 4 5% 4 5% 9% 34%	2200
October	1st to 10th	Day	22% 11% 3 6% 4 4 4 4 6% 6% 31%	2185
	11th to 20th	Day	20% 13% 3 7% 4 5% 4 4 6% 6% 28%	1876
	21st to end	Day	24% 21% 3 6% 4 4 4 3 3 4 24%	1980
November	1st to 10th	Day	19% 19% 4 8% 5% 4 4 3 4 5% 26%	1851
	11th to 20th	Day	17% 19% 6% 11% 5% 4 3 3 4 5% 22%	1890
	21st to end	Day	18% 18% 7% 12% 6% 5% 5% 3 5% 6% 16%	1732
December	1st to 10th	Day	13% 21% 8% 22% 10% 5% 3 2 3 4 11%	2680
	11th to 20th	Day	15% 19% 7% 14% 6% 4 4 3 4 4 20%	3066
	21st to end	Day	17% 19% 5% 14% 6% 4 5% 3 4 5% 18%	4048
January	1st to 10th	Night	10% 20% 9% 21% 10% 7% 4 2 2 3 12%	8234
	11th to 20th	Night	9% 20% 10% 21% 12% 6% 4 3 3 3 9%	8235
	21st to end	Night	8% 14% 7% 16% 12% 11% 6% 4 4 4 15%	9057
February	1st to 10th	Night	12% 17% 6% 17% 9% 7% 4 3 4 4 16%	2849
	11th to 20th	Night	10% 19% 6% 18% 9% 7% 4 2 3 4 18%	2458
	21st to end	Night	12% 17% 7% 11% 9% 6% 4 3 3 4 24%	2076
March	1st to 10th	Night	18% 18% 6% 12% 6% 6% 4 2 3 4 20%	5484
	11th to 20th	Night	15% 19% 5% 11% 6% 5% 4 4 5% 6% 23%	5375
	21st to end	Night	15% 19% 6% 13% 6% 4 4 2 3 4 24%	5166
April	1st to 10th	Night	21% 17% 5% 8% 5% 3 3 3 5% 4 26%	2100
	11th to 20th	Night	21% 15% 4 7% 4 3 3 3 4 5% 30%	2032
	21st to end	Night	22% 13% 3 7% 5% 4 3 3 4 6% 30%	1890
May	1st to 10th	Night	27% 11% 3 8% 5% 4 4 3 4 6% 25%	5241
	11th to 20th	Night	22% 9% 2 7% 5% 5% 5% 4 7% 7% 28%	4639
	21st to end	Night	21% 11% 3 7% 4 4 4 4 5% 7% 32%	5114
June	1st to 10th	Night	26% 9% 3 5% 4 4 4 4 6% 6% 30%	1680
	11th to 20th	Night	20% 6% 3 6% 4 5% 6% 5% 6% 7% 34%	1640
	21st to end	Night	20% 7% 3 7% 5% 4 5% 5% 6% 8% 30%	1600
July	1st to 10th	Night	16% 7% 3 8% 6% 6% 6% 4 7% 8% 30%	3600
	11th to 20th	Night	18% 7% 2 7% 4 4 4 4 6% 7% 38%	3600
	21st to end	Night	14% 7% 2 7% 5% 5% 5% 4 6% 9% 38%	3926
August	1st to 10th	Night	23% 8% 3 6% 4 4 4 3 6% 6% 32%	2613
	11th to 20th	Night	17% 7% 3 8% 5% 5% 5% 5% 7% 8% 30%	2872
	21st to end	Night	18% 8% 2 6% 4 4 4 3 5% 6% 40%	3567
September	1st to 10th	Night	16% 8% 3 6% 4 5% 4 4 5% 6% 41%	2000
	11th to 20th	Night	16% 6% 2 5% 3 3 4 3 4 7% 47%	2163
	21st to end	Night	21% 6% 2 5% 3 3 4 3 5% 8% 41%	2200
October	1st to 10th	Night	20% 9% 3 7% 4 3 3 3 5% 6% 35%	2211
	11th to 20th	Night	22% 13% 2 8% 5% 4 4 3 4 5% 29%	2522
	21st to end	Night	25% 16% 3 7% 4 4 4 3 5% 6% 24%	2860
November	1st to 10th	Night	20% 17% 5% 9% 4 5% 3 3 4 5% 25%	2667
	11th to 20th	Night	17% 18% 7% 10% 6% 3 3 3 4 5% 25%	2730
	21st to end	Night	18% 20% 6% 13% 5% 4 4 3 3 4 20%	2887
December	1st to 10th	Night	13% 23% 13% 21% 7% 4 4 2 3 3 8%	4720
	11th to 20th	Night	16% 22% 6% 18% 6% 4 4 2 3 3 15%	5348
	21st to end	Night	17% 18% 6% 13% 7% 5% 5% 3 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	80% 3 9% 6% 1	4662
	11th to 20th	Day	80% 4 6% 7% 3 1	4680
	21st to end	Day	74% 3 7% 8% 8% 1	5124
February	1st to 10th	Day	73% 4 5% 11% 5% 1	1767
	11th to 20th	Day	73% 4 8% 9% 5% 1	2057
	21st to end	Day	67% 5% 8% 13% 6% 1	1730
March	1st to 10th	Day	70% 5% 6% 8% 7% 3	4579
	11th to 20th	Day	60% 5% 12% 12% 10% 2	4803
	21st to end	Day	62% 4 7% 13% 13% 1	6005
April	1st to 10th	Day	63% 4 8% 16% 8% 2	2520
	11th to 20th	Day	57% 4 8% 18% 12% 1	2536
	21st to end	Day	58% 5% 9% 16% 9% 2	2730
May	1st to 10th	Day	65% 6% 8% 14% 6%	7725
	11th to 20th	Day	54% 8% 14% 17% 6% 1	8225
	21st to end	Day	52% 7% 11% 22% 7%	9061
June	1st to 10th	Day	57% 6% 12% 17% 7% 1	2940
	11th to 20th	Day	47% 7% 12% 23% 10% 1	2870
	21st to end	Day	54% 8% 11% 19% 7%	2800
July	1st to 10th	Day	49% 8% 16% 21% 7%	6290
	11th to 20th	Day	43% 9% 15% 27% 7%	6285
	21st to end	Day	43% 7% 13% 30% 7%	6728
August	1st to 10th	Day	53% 7% 15% 20% 5%	4490
	11th to 20th	Day	51% 9% 17% 18% 5%	4214
	21st to end	Day	44% 7% 16% 19% 11% 2	4327
September	1st to 10th	Day	43% 6% 13% 28% 10%	2400
	11th to 20th	Day	42% 5% 11% 28% 14%	2236
	21st to end	Day	46% 8% 13% 22% 11% 1	2200
October	1st to 10th	Day	49% 6% 14% 23% 9%	3562
	11th to 20th	Day	54% 5% 13% 21% 8%	3027
	21st to end	Day	54% 3 14% 20% 8% 1	3180
November	1st to 10th	Day	61% 5% 10% 16% 7% 1	1851
	11th to 20th	Day	65% 6% 10% 10% 8% 2	1890
	21st to end	Day	70% 6% 11% 11% 2	1732
December	1st to 10th	Day	81% 4 7% 6% 2	2680
	11th to 20th	Day	68% 4 7% 14% 6%	3066
	21st to end	Day	70% 5% 6% 10% 8% 2	4048
January	1st to 10th	Night	80% 4 8% 7% 2	8234
	11th to 20th	Night	81% 4 5% 6% 3	8280
	21st to end	Night	73% 4 7% 8% 8% 1	9057
February	1st to 10th	Night	72% 5% 6% 11% 5%	2849
	11th to 20th	Night	72% 4 6% 11% 5%	2460
	21st to end	Night	66% 4 7% 13% 9% 1	2076
March	1st to 10th	Night	69% 4 8% 11% 6% 2	5494
	11th to 20th	Night	62% 6% 13% 12% 7% 1	5376
	21st to end	Night	67% 4 4 13% 11% 1	5166
April	1st to 10th	Night	61% 5% 8% 14% 10% 1	2100
	11th to 20th	Night	56% 5% 9% 18% 11% 1	2032
	21st to end	Night	56% 5% 9% 16% 12% 2	1890
May	1st to 10th	Night	60% 6% 12% 14% 7%	5247
	11th to 20th	Night	52% 8% 12% 21% 6% 1	4640
	21st to end	Night	52% 6% 11% 20% 12%	5115
June	1st to 10th	Night	54% 7% 10% 21% 9% 1	1680
	11th to 20th	Night	47% 8% 12% 21% 9% 3	1640
	21st to end	Night	52% 8% 14% 18% 8% 1	1600
July	1st to 10th	Night	50% 7% 16% 21% 6%	3560
	11th to 20th	Night	45% 7% 14% 27% 7%	3552
	21st to end	Night	43% 7% 15% 26% 9%	3809
August	1st to 10th	Night	52% 6% 14% 23% 5%	2603
	11th to 20th	Night	48% 10% 18% 16% 7%	2899
	21st to end	Night	45% 6% 13% 23% 12% 1	3567
September	1st to 10th	Night	43% 7% 14% 26% 11%	2000
	11th to 20th	Night	39% 6% 15% 29% 11% 1	2163
	21st to end	Night	43% 7% 13% 24% 11% 2	2200
October	1st to 10th	Night	51% 5% 11% 23% 9%	3614
	11th to 20th	Night	55% 5% 10% 21% 10%	4110
	21st to end	Night	54% 5% 14% 18% 9% 1	4610
November	1st to 10th	Night	62% 6% 10% 15% 7% 1	2667
	11th to 20th	Night	64% 5% 8% 14% 7% 2	2730
	21st to end	Night	69% 6% 10% 11% 3	2887
December	1st to 10th	Night	84% 5% 5% 6% 1	4720
	11th to 20th	Night	76% 3 6% 8% 7%	5348
	21st to end	Night	69% 5% 6% 11% 7% 1	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	29% 23% 35% 12% 1	220
	11th to 20th	Day	31% 30% 29% 7% 3	220
	21st to end	Day	29% 25% 32% 10% 3	242
February	1st to 10th	Day	35% 29% 25% 9% 1	275
	11th to 20th	Day	31% 29% 28% 10% 2	536
	21st to end	Day	29% 29% 28% 13% 1	446
March	1st to 10th	Day	31% 24% 29% 12% 3	540
	11th to 20th	Day	33% 27% 25% 12% 3	540
	21st to end	Day	38% 22% 22% 12% 5% 1	594
April	1st to 10th	Day	39% 21% 24% 12% 4 1	540
	11th to 20th	Day	37% 22% 24% 10% 5% 2	532
	21st to end	Day	34% 24% 25% 12% 5% 1	540
May	1st to 10th	Day	41% 18% 24% 12% 5% 1	543
	11th to 20th	Day	27% 20% 30% 17% 5% 2	567
	21st to end	Day	25% 20% 32% 17% 5% 1	617
June	1st to 10th	Day	31% 14% 31% 16% 7%	570
	11th to 20th	Day	23% 19% 30% 20% 8% 1	550
	21st to end	Day	26% 17% 33% 15% 8% 2	530
July	1st to 10th	Day	20% 15% 33% 23% 8% 1	525
	11th to 20th	Day	17% 12% 38% 23% 7% 2	524
	21st to end	Day	19% 11% 37% 24% 7% 1	576
August	1st to 10th	Day	18% 12% 29% 27% 12% 2	526
	11th to 20th	Day	18% 9% 31% 22% 16% 4	519
	21st to end	Day	24% 15% 24% 23% 11% 4	583
September	1st to 10th	Day	21% 14% 28% 20% 13% 4	530
	11th to 20th	Day	20% 12% 21% 23% 17% 8%	530
	21st to end	Day	20% 16% 23% 24% 12% 4	530
October	1st to 10th	Day	25% 17% 25% 18% 11% 3	530
	11th to 20th	Day	30% 20% 25% 16% 8% 1	461
	21st to end	Day	34% 23% 24% 14% 5%	462
November	1st to 10th	Day	37% 19% 27% 13% 4	425
	11th to 20th	Day	31% 23% 26% 13% 5% 1	430
	21st to end	Day	33% 22% 29% 13% 2	272
December	1st to 10th	Day	30% 24% 29% 12% 5%	220
	11th to 20th	Day	36% 28% 27% 8% 1	220
	21st to end	Day	38% 21% 29% 9% 2	242
January	1st to 10th	Night	27% 27% 30% 14% 2	840
	11th to 20th	Night	25% 27% 29% 15% 3	840
	21st to end	Night	22% 24% 31% 18% 5%	924
February	1st to 10th	Night	24% 25% 30% 19% 3	840
	11th to 20th	Night	24% 25% 33% 15% 2	823
	21st to end	Night	25% 20% 34% 18% 2	692
March	1st to 10th	Night	29% 22% 30% 17% 2	840
	11th to 20th	Night	31% 21% 27% 16% 5%	840
	21st to end	Night	32% 19% 25% 18% 6% 1	924
April	1st to 10th	Night	35% 20% 24% 17% 4	840
	11th to 20th	Night	32% 19% 24% 18% 6%	788
	21st to end	Night	31% 16% 29% 18% 5%	630
May	1st to 10th	Night	31% 13% 29% 21% 5% 1	625
	11th to 20th	Night	23% 12% 33% 24% 7% 1	414
	21st to end	Night	23% 11% 27% 32% 6% 1	455
June	1st to 10th	Night	30% 8% 25% 26% 10%	420
	11th to 20th	Night	21% 9% 26% 33% 12%	410
	21st to end	Night	20% 8% 29% 34% 9%	400
July	1st to 10th	Night	17% 6% 29% 35% 13% 1	390
	11th to 20th	Night	15% 6% 27% 35% 15% 1	388
	21st to end	Night	15% 7% 25% 38% 14%	438
August	1st to 10th	Night	20% 4 16% 41% 18%	412
	11th to 20th	Night	18% 7% 23% 32% 19% 1	592
	21st to end	Night	20% 7% 24% 32% 16% 2	861
September	1st to 10th	Night	19% 8% 26% 32% 14% 1	800
	11th to 20th	Night	21% 8% 19% 30% 21% 2	800
	21st to end	Night	23% 11% 26% 25% 13% 2	800
October	1st to 10th	Night	27% 12% 22% 25% 13% 1	800
	11th to 20th	Night	31% 15% 24% 21% 8% 1	800
	21st to end	Night	34% 17% 27% 19% 4	880
November	1st to 10th	Night	34% 16% 28% 17% 5%	820
	11th to 20th	Night	28% 21% 28% 15% 7% 1	840
	21st to end	Night	30% 24% 25% 15% 5% 1	840
December	1st to 10th	Night	31% 25% 27% 13% 3	840
	11th to 20th	Night	32% 24% 27% 13% 4	840
	21st to end	Night	33% 23% 26% 16% 2	924

Page generated at 2026-06-13 02:31:43. Version ac07

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