Ferme Alarie
Clear Sky Chart
History

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

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% 12% 4 9% 5% 4 4 3 5% 6% 28%	127798
	Night	17% 13% 5% 10% 6% 4 4 3 5% 6% 28%	124216
Transparency	Day	54% 6% 11% 18% 9% 1	131229
	Night	56% 6% 11% 17% 9% 1	128872
Seeing	Day	27% 18% 29% 18% 7% 2	15924
	Night	25% 13% 28% 24% 9% 1	25047

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% 21% 6% 19% 7% 7% 4 2 3 3 14%	3677
	11th to 20th	Day	11% 19% 8% 18% 11% 3 3 2 4 4 17%	3650
	21st to end	Day	8% 17% 9% 15% 6% 5% 5% 4 5% 5% 20%	4048
February	1st to 10th	Day	11% 18% 7% 14% 9% 4 4 2 4 5% 21%	1790
	11th to 20th	Day	12% 20% 5% 13% 6% 5% 4 3 4 4 24%	1798
	21st to end	Day	16% 17% 6% 11% 8% 5% 3 2 4 5% 23%	1650
March	1st to 10th	Day	18% 17% 6% 13% 6% 4 4 3 4 4 21%	4476
	11th to 20th	Day	13% 15% 6% 11% 5% 5% 4 3 4 6% 28%	4828
	21st to end	Day	18% 13% 3 8% 5% 4 4 3 4 5% 32%	5877
April	1st to 10th	Day	21% 16% 3 8% 4 4 3 3 4 5% 30%	2400
	11th to 20th	Day	22% 12% 3 7% 4 4 4 3 4 5% 33%	2374
	21st to end	Day	22% 11% 4 9% 5% 5% 4 4 4 5% 30%	2568
May	1st to 10th	Day	24% 12% 3 8% 6% 5% 5% 4 5% 6% 22%	6346
	11th to 20th	Day	19% 9% 3 8% 6% 5% 5% 4 6% 7% 29%	6318
	21st to end	Day	23% 10% 3 8% 5% 4 4 3 5% 6% 30%	6949
June	1st to 10th	Day	23% 9% 3 7% 4 5% 6% 4 6% 7% 27%	2800
	11th to 20th	Day	16% 7% 3 7% 5% 5% 6% 5% 6% 8% 33%	2800
	21st to end	Day	22% 8% 3 7% 6% 5% 6% 4 6% 7% 28%	2800
July	1st to 10th	Day	16% 7% 3 9% 5% 5% 6% 5% 7% 9% 28%	6360
	11th to 20th	Day	14% 6% 2 8% 4 4 5% 4 6% 9% 37%	6360
	21st to end	Day	10% 6% 2 5% 4 4 5% 4 7% 10% 43%	6926
August	1st to 10th	Day	16% 7% 3 8% 6% 6% 6% 4 6% 8% 30%	4563
	11th to 20th	Day	16% 7% 2 7% 5% 4 5% 5% 7% 8% 35%	4151
	21st to end	Day	16% 6% 3 6% 4 5% 5% 3 6% 9% 36%	4312
September	1st to 10th	Day	17% 5% 2 6% 4 4 4 4 5% 8% 41%	2400
	11th to 20th	Day	15% 6% 3 5% 3 4 4 3 5% 8% 43%	2355
	21st to end	Day	21% 7% 2 5% 4 3 4 4 5% 7% 38%	2200
October	1st to 10th	Day	22% 11% 2 6% 3 5% 5% 3 5% 6% 33%	2000
	11th to 20th	Day	25% 13% 4 9% 3 4 5% 2 4 6% 26%	1990
	21st to end	Day	26% 14% 4 8% 4 4 3 3 4 6% 24%	1980
November	1st to 10th	Day	18% 15% 4 7% 4 4 4 4 5% 6% 30%	1851
	11th to 20th	Day	19% 17% 6% 10% 6% 4 4 4 5% 5% 21%	1727
	21st to end	Day	23% 17% 7% 11% 6% 4 4 2 3 4 18%	1680
December	1st to 10th	Day	19% 23% 9% 11% 6% 4 4 3 4 4 12%	2680
	11th to 20th	Day	18% 20% 6% 14% 6% 3 4 3 3 3 20%	3066
	21st to end	Day	20% 18% 5% 10% 5% 4 4 3 5% 4 21%	4048
January	1st to 10th	Night	13% 24% 8% 14% 6% 4 3 2 4 4 17%	6489
	11th to 20th	Night	11% 18% 8% 18% 10% 5% 4 3 4 5% 15%	6455
	21st to end	Night	9% 17% 8% 16% 7% 7% 5% 3 4 5% 19%	7150
February	1st to 10th	Night	12% 16% 6% 13% 8% 4 5% 4 5% 4 23%	2610
	11th to 20th	Night	13% 16% 6% 13% 8% 5% 4 3 4 4 24%	2487
	21st to end	Night	15% 16% 5% 11% 5% 5% 5% 3 5% 5% 26%	1980
March	1st to 10th	Night	21% 14% 5% 12% 5% 4 4 2 3 4 26%	5364
	11th to 20th	Night	13% 14% 4 10% 5% 5% 4 4 5% 6% 29%	5127
	21st to end	Night	17% 13% 4 10% 6% 5% 4 3 4 5% 29%	5054
April	1st to 10th	Night	22% 13% 4 7% 5% 3 3 3 5% 5% 31%	2000
	11th to 20th	Night	20% 10% 3 7% 4 3 4 3 5% 6% 35%	1975
	21st to end	Night	20% 11% 3 7% 4 4 4 3 4 5% 34%	1847
May	1st to 10th	Night	21% 11% 4 8% 5% 4 5% 4 6% 6% 26%	3594
	11th to 20th	Night	19% 9% 3 8% 5% 4 4 3 5% 7% 34%	3575
	21st to end	Night	21% 10% 4 7% 5% 5% 5% 4 5% 6% 29%	3926
June	1st to 10th	Night	19% 8% 3 8% 6% 4 5% 4 6% 7% 31%	1600
	11th to 20th	Night	16% 8% 2 6% 5% 4 4 4 6% 8% 37%	1600
	21st to end	Night	20% 7% 2 6% 5% 4 4 4 5% 6% 36%	1600
July	1st to 10th	Night	15% 7% 3 8% 6% 6% 6% 6% 6% 8% 31%	3600
	11th to 20th	Night	16% 7% 3 7% 4 3 4 3 6% 7% 40%	3600
	21st to end	Night	10% 5% 1 6% 4 4 5% 4 7% 8% 46%	3926
August	1st to 10th	Night	13% 7% 3 8% 5% 4 5% 4 6% 8% 38%	2586
	11th to 20th	Night	17% 7% 2 7% 4 4 4 3 6% 6% 40%	2860
	21st to end	Night	18% 6% 3 7% 4 4 4 3 5% 7% 39%	3586
September	1st to 10th	Night	15% 7% 2 6% 3 4 3 3 5% 7% 45%	2000
	11th to 20th	Night	15% 6% 1 4 4 4 3 3 6% 6% 48%	2044
	21st to end	Night	18% 7% 2 5% 3 3 4 2 5% 8% 42%	2200
October	1st to 10th	Night	19% 9% 3 6% 4 4 4 3 5% 5% 38%	2395
	11th to 20th	Night	22% 10% 3 8% 4 4 4 3 5% 6% 30%	2409
	21st to end	Night	24% 12% 3 9% 5% 3 4 3 4 6% 27%	2860
November	1st to 10th	Night	21% 13% 4 8% 5% 5% 4 3 5% 6% 28%	2667
	11th to 20th	Night	18% 15% 5% 10% 5% 5% 4 3 5% 6% 24%	2892
	21st to end	Night	21% 19% 6% 10% 6% 4 4 3 4 4 18%	2940
December	1st to 10th	Night	18% 18% 7% 14% 7% 5% 4 3 4 5% 13%	4720
	11th to 20th	Night	24% 16% 5% 12% 6% 3 3 2 3 4 22%	5348
	21st to end	Night	22% 21% 4 10% 5% 4 3 3 3 6% 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	73% 7% 5% 11% 3	3678
	11th to 20th	Day	71% 4 5% 12% 8% 1	3680
	21st to end	Day	64% 6% 9% 11% 10% 1	4048
February	1st to 10th	Day	65% 3 8% 15% 7% 2	1790
	11th to 20th	Day	63% 5% 10% 12% 9% 1	1807
	21st to end	Day	64% 4 7% 14% 9% 2	1650
March	1st to 10th	Day	64% 5% 7% 10% 11% 2	4479
	11th to 20th	Day	56% 6% 14% 12% 10% 1	4828
	21st to end	Day	53% 5% 7% 16% 17% 2	5877
April	1st to 10th	Day	56% 4 9% 17% 11% 3	2400
	11th to 20th	Day	54% 6% 7% 19% 12% 2	2374
	21st to end	Day	57% 6% 8% 14% 12% 3	2568
May	1st to 10th	Day	60% 7% 9% 17% 7% 1	6357
	11th to 20th	Day	51% 9% 15% 16% 9% 1	6322
	21st to end	Day	53% 7% 11% 16% 12% 1	6949
June	1st to 10th	Day	54% 7% 11% 16% 11% 1	2800
	11th to 20th	Day	46% 9% 12% 20% 11% 3	2800
	21st to end	Day	55% 7% 11% 17% 9% 1	2800
July	1st to 10th	Day	50% 7% 13% 24% 6%	6290
	11th to 20th	Day	42% 6% 15% 29% 8%	6285
	21st to end	Day	36% 7% 17% 33% 8%	6728
August	1st to 10th	Day	49% 7% 16% 21% 6%	4549
	11th to 20th	Day	44% 7% 17% 26% 5%	4193
	21st to end	Day	44% 7% 15% 21% 12% 1	4312
September	1st to 10th	Day	41% 7% 14% 26% 12%	2400
	11th to 20th	Day	37% 7% 13% 31% 11% 1	2355
	21st to end	Day	45% 6% 13% 24% 11%	2200
October	1st to 10th	Day	50% 6% 11% 26% 7%	3260
	11th to 20th	Day	52% 8% 13% 21% 6% 1	3218
	21st to end	Day	53% 6% 19% 14% 7% 1	3180
November	1st to 10th	Day	54% 8% 13% 18% 6% 1	1851
	11th to 20th	Day	65% 6% 10% 10% 9% 1	1727
	21st to end	Day	69% 7% 10% 10% 4 1	1680
December	1st to 10th	Day	75% 5% 7% 10% 2	2680
	11th to 20th	Day	68% 5% 7% 14% 6%	3066
	21st to end	Day	66% 5% 8% 14% 7%	4048
January	1st to 10th	Night	71% 6% 10% 11% 3	6489
	11th to 20th	Night	70% 6% 10% 10% 4 1	6500
	21st to end	Night	67% 5% 8% 8% 11% 1	7150
February	1st to 10th	Night	62% 6% 9% 15% 7% 1	2610
	11th to 20th	Night	62% 5% 10% 16% 7% 1	2489
	21st to end	Night	58% 6% 10% 16% 9% 1	1980
March	1st to 10th	Night	63% 4 9% 11% 11% 3	5374
	11th to 20th	Night	53% 8% 13% 15% 8% 3	5128
	21st to end	Night	56% 6% 7% 20% 10% 2	5054
April	1st to 10th	Night	55% 4 9% 17% 13% 2	2000
	11th to 20th	Night	50% 6% 9% 21% 13% 2	1975
	21st to end	Night	51% 5% 9% 18% 13% 3	1847
May	1st to 10th	Night	55% 8% 10% 18% 7% 2	3600
	11th to 20th	Night	47% 10% 15% 16% 11% 2	3576
	21st to end	Night	54% 7% 9% 16% 12% 1	3927
June	1st to 10th	Night	48% 10% 12% 20% 10%	1600
	11th to 20th	Night	44% 8% 11% 22% 13% 2	1600
	21st to end	Night	48% 8% 12% 19% 13% 1	1600
July	1st to 10th	Night	49% 7% 18% 20% 7%	3560
	11th to 20th	Night	42% 7% 17% 28% 6%	3552
	21st to end	Night	34% 7% 17% 31% 11%	3809
August	1st to 10th	Night	42% 9% 15% 26% 7%	2576
	11th to 20th	Night	42% 8% 19% 25% 7%	2884
	21st to end	Night	43% 8% 15% 22% 11% 2	3586
September	1st to 10th	Night	37% 7% 15% 27% 12% 1	2000
	11th to 20th	Night	36% 6% 14% 33% 10% 1	2044
	21st to end	Night	41% 7% 13% 28% 11%	2200
October	1st to 10th	Night	44% 6% 15% 24% 11% 1	3915
	11th to 20th	Night	48% 7% 15% 22% 8%	3920
	21st to end	Night	52% 5% 18% 15% 9% 1	4610
November	1st to 10th	Night	56% 7% 14% 18% 6%	2667
	11th to 20th	Night	59% 7% 11% 14% 8% 1	2892
	21st to end	Night	68% 7% 10% 12% 4	2940
December	1st to 10th	Night	72% 6% 10% 9% 3	4720
	11th to 20th	Night	68% 3 6% 13% 9% 1	5348
	21st to end	Night	65% 4 6% 12% 12%	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	22% 21% 37% 15% 3	220
	11th to 20th	Day	30% 24% 30% 11% 5%	220
	21st to end	Day	22% 24% 33% 17% 3 1	242
February	1st to 10th	Day	35% 31% 26% 7% 1	295
	11th to 20th	Day	29% 31% 31% 9% 1	345
	21st to end	Day	33% 21% 31% 12% 2	414
March	1st to 10th	Day	30% 20% 33% 14% 3 1	500
	11th to 20th	Day	30% 23% 29% 15% 2 1	500
	21st to end	Day	33% 22% 24% 15% 5% 1	550
April	1st to 10th	Day	34% 19% 28% 14% 4 1	500
	11th to 20th	Day	36% 18% 22% 14% 8% 2	492
	21st to end	Day	34% 19% 29% 13% 3 1	500
May	1st to 10th	Day	30% 22% 30% 13% 5% 1	503
	11th to 20th	Day	26% 17% 31% 19% 6% 1	527
	21st to end	Day	27% 19% 28% 19% 6% 1	573
June	1st to 10th	Day	29% 17% 32% 16% 5%	530
	11th to 20th	Day	21% 18% 33% 18% 9% 1	530
	21st to end	Day	27% 15% 33% 17% 7% 1	530
July	1st to 10th	Day	19% 13% 33% 25% 8% 2	525
	11th to 20th	Day	17% 13% 36% 26% 7% 1	524
	21st to end	Day	17% 12% 36% 25% 9% 2	576
August	1st to 10th	Day	18% 11% 26% 32% 11% 2	526
	11th to 20th	Day	18% 7% 27% 28% 14% 7%	519
	21st to end	Day	21% 15% 26% 20% 13% 6%	583
September	1st to 10th	Day	22% 10% 31% 19% 12% 6%	530
	11th to 20th	Day	15% 12% 24% 23% 17% 9%	530
	21st to end	Day	23% 15% 25% 21% 10% 6%	530
October	1st to 10th	Day	29% 16% 21% 20% 12% 2	530
	11th to 20th	Day	33% 19% 26% 15% 7% 1	524
	21st to end	Day	37% 13% 28% 18% 4	462
November	1st to 10th	Day	37% 16% 25% 18% 4 1	425
	11th to 20th	Day	32% 21% 27% 13% 6%	267
	21st to end	Day	34% 27% 27% 10% 1	220
December	1st to 10th	Day	35% 17% 30% 14% 4	220
	11th to 20th	Day	31% 28% 30% 9% 1 1	220
	21st to end	Day	33% 21% 29% 12% 2 2	242
January	1st to 10th	Night	29% 16% 35% 17% 3	840
	11th to 20th	Night	31% 19% 27% 18% 5%	840
	21st to end	Night	20% 17% 34% 21% 7% 1	924
February	1st to 10th	Night	21% 21% 34% 20% 4 1	801
	11th to 20th	Night	24% 21% 33% 18% 3	783
	21st to end	Night	25% 19% 29% 24% 3	660
March	1st to 10th	Night	27% 17% 31% 21% 4	800
	11th to 20th	Night	26% 20% 31% 19% 4 1	800
	21st to end	Night	27% 14% 29% 23% 5% 1	880
April	1st to 10th	Night	31% 16% 27% 22% 5%	800
	11th to 20th	Night	28% 15% 28% 23% 6%	791
	21st to end	Night	29% 16% 28% 20% 8%	647
May	1st to 10th	Night	27% 12% 28% 24% 8% 2	400
	11th to 20th	Night	22% 10% 30% 29% 8%	394
	21st to end	Night	21% 9% 34% 27% 9%	433
June	1st to 10th	Night	23% 8% 31% 29% 9% 1	400
	11th to 20th	Night	20% 7% 28% 32% 11% 1	400
	21st to end	Night	22% 6% 22% 35% 16%	400
July	1st to 10th	Night	14% 6% 26% 40% 14% 1	390
	11th to 20th	Night	15% 4 23% 40% 17% 1	388
	21st to end	Night	13% 5% 25% 40% 15% 1	438
August	1st to 10th	Night	14% 3 20% 43% 20% 1	398
	11th to 20th	Night	13% 5% 21% 34% 24% 2	576
	21st to end	Night	19% 6% 24% 32% 17% 2	880
September	1st to 10th	Night	18% 7% 27% 33% 14% 1	800
	11th to 20th	Night	20% 6% 18% 33% 23% 1	800
	21st to end	Night	22% 9% 23% 28% 18% 1	800
October	1st to 10th	Night	24% 11% 24% 28% 14% 1	800
	11th to 20th	Night	30% 12% 25% 24% 8% 1	800
	21st to end	Night	32% 13% 26% 24% 5%	880
November	1st to 10th	Night	30% 14% 27% 22% 6% 1	820
	11th to 20th	Night	28% 17% 29% 15% 9% 1	840
	21st to end	Night	34% 18% 25% 18% 5% 1	840
December	1st to 10th	Night	32% 18% 27% 17% 5%	840
	11th to 20th	Night	31% 20% 27% 16% 5% 1	840
	21st to end	Night	36% 16% 27% 17% 4	924

Page generated at 2026-01-29 01:21:46. Version ac07

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