Mont-Tremblant
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mont-Tremblant 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	17% 12% 4 9% 6% 5% 4 3 5% 6% 28%	131277
	Night	17% 14% 5% 11% 6% 5% 4 3 4 5% 27%	130200
Transparency	Day	56% 5% 11% 18% 9% 1	134708
	Night	58% 5% 11% 17% 9% 1	134856
Seeing	Day	27% 18% 29% 18% 7% 2	16086
	Night	25% 13% 28% 24% 9% 1	25223

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	12% 18% 7% 19% 7% 5% 5% 3 4 4 14%	4661
	11th to 20th	Day	11% 23% 8% 19% 10% 3 2 2 3 4 16%	4650
	21st to end	Day	7% 14% 9% 15% 9% 7% 6% 4 6% 6% 18%	5124
February	1st to 10th	Day	10% 18% 6% 14% 8% 4 4 3 4 5% 22%	1872
	11th to 20th	Day	12% 19% 5% 13% 7% 5% 4 2 4 5% 24%	1895
	21st to end	Day	15% 19% 5% 10% 7% 5% 4 3 5% 4 23%	1730
March	1st to 10th	Day	18% 17% 6% 14% 7% 4 4 2 4 4 21%	4576
	11th to 20th	Day	14% 15% 6% 12% 5% 5% 4 3 4 6% 27%	4869
	21st to end	Day	18% 13% 4 8% 5% 4 4 3 4 5% 32%	5893
April	1st to 10th	Day	20% 16% 4 9% 4 4 3 2 4 5% 29%	2400
	11th to 20th	Day	22% 12% 4 7% 5% 4 4 3 4 5% 31%	2374
	21st to end	Day	22% 11% 3 9% 5% 4 5% 4 4 5% 30%	2568
May	1st to 10th	Day	24% 12% 4 8% 5% 5% 5% 4 5% 6% 23%	6346
	11th to 20th	Day	20% 8% 3 8% 5% 5% 5% 4 5% 7% 30%	6318
	21st to end	Day	22% 11% 3 8% 5% 4 4 3 5% 6% 29%	6949
June	1st to 10th	Day	24% 9% 2 7% 5% 5% 5% 4 6% 7% 26%	2800
	11th to 20th	Day	17% 7% 3 7% 6% 5% 5% 4 7% 7% 32%	2800
	21st to end	Day	23% 8% 3 7% 5% 5% 5% 4 5% 7% 26%	2800
July	1st to 10th	Day	17% 8% 3 8% 6% 6% 6% 5% 7% 8% 28%	6360
	11th to 20th	Day	14% 7% 3 7% 4 5% 5% 4 6% 9% 36%	6360
	21st to end	Day	11% 6% 2 5% 4 5% 5% 4 7% 9% 42%	6926
August	1st to 10th	Day	16% 7% 3 7% 6% 5% 6% 4 6% 9% 29%	4563
	11th to 20th	Day	17% 8% 3 6% 5% 4 5% 4 7% 7% 34%	4155
	21st to end	Day	17% 5% 2 6% 5% 5% 5% 4 6% 8% 35%	4312
September	1st to 10th	Day	18% 6% 2 6% 4 5% 4 4 5% 7% 40%	2400
	11th to 20th	Day	16% 6% 2 6% 3 4 4 4 7% 7% 43%	2353
	21st to end	Day	22% 7% 2 5% 4 4 3 3 5% 7% 38%	2200
October	1st to 10th	Day	23% 10% 2 6% 4 3 4 3 5% 7% 33%	2005
	11th to 20th	Day	26% 13% 3 8% 5% 4 4 3 5% 5% 25%	1986
	21st to end	Day	26% 16% 4 8% 4 4 3 3 4 5% 24%	1980
November	1st to 10th	Day	18% 16% 4 9% 4 3 4 3 5% 6% 28%	1851
	11th to 20th	Day	20% 18% 6% 10% 6% 4 4 3 4 5% 20%	1727
	21st to end	Day	23% 18% 7% 13% 5% 4 4 2 3 4 18%	1680
December	1st to 10th	Day	19% 23% 10% 10% 7% 4 3 3 4 4 12%	2680
	11th to 20th	Day	18% 21% 7% 13% 6% 4 3 3 3 3 19%	3066
	21st to end	Day	19% 18% 5% 11% 5% 4 5% 3 5% 4 21%	4048
January	1st to 10th	Night	12% 21% 9% 15% 6% 4 4 3 4 4 17%	8234
	11th to 20th	Night	11% 20% 9% 20% 11% 5% 3 2 3 3 12%	8235
	21st to end	Night	6% 14% 8% 17% 9% 9% 6% 4 5% 5% 17%	9057
February	1st to 10th	Night	11% 18% 5% 13% 8% 5% 4 4 4 5% 23%	2746
	11th to 20th	Night	13% 16% 7% 13% 8% 5% 3 3 3 5% 24%	2610
	21st to end	Night	14% 16% 7% 11% 5% 5% 4 4 4 5% 25%	2076
March	1st to 10th	Night	20% 15% 5% 12% 5% 4 4 3 4 4 24%	5484
	11th to 20th	Night	13% 15% 4 11% 5% 4 4 4 5% 6% 28%	5227
	21st to end	Night	17% 14% 4 9% 6% 5% 4 3 5% 5% 28%	5038
April	1st to 10th	Night	22% 13% 4 7% 5% 3 4 2 5% 6% 29%	2000
	11th to 20th	Night	21% 10% 3 6% 4 4 3 3 5% 5% 35%	1975
	21st to end	Night	20% 11% 3 8% 4 4 4 2 5% 5% 34%	1845
May	1st to 10th	Night	20% 12% 3 9% 5% 4 5% 4 6% 6% 27%	3594
	11th to 20th	Night	20% 9% 3 8% 4 4 4 3 5% 7% 34%	3575
	21st to end	Night	21% 11% 3 7% 5% 5% 5% 4 5% 6% 28%	3926
June	1st to 10th	Night	19% 8% 3 8% 4 5% 5% 4 6% 7% 31%	1600
	11th to 20th	Night	17% 9% 2 6% 4 4 4 5% 5% 8% 37%	1600
	21st to end	Night	21% 7% 3 6% 5% 4 6% 4 5% 6% 35%	1600
July	1st to 10th	Night	15% 7% 3 9% 6% 5% 6% 5% 7% 9% 29%	3600
	11th to 20th	Night	16% 8% 3 6% 4 4 4 3 5% 7% 39%	3600
	21st to end	Night	11% 4 2 6% 4 4 4 4 7% 8% 46%	3926
August	1st to 10th	Night	13% 8% 3 8% 5% 4 4 4 6% 7% 38%	2586
	11th to 20th	Night	19% 7% 3 7% 4 4 3 3 6% 5% 40%	2858
	21st to end	Night	19% 7% 2 6% 5% 4 4 3 5% 7% 38%	3586
September	1st to 10th	Night	15% 8% 2 5% 4 3 3 3 5% 7% 44%	2000
	11th to 20th	Night	16% 5% 2 4 3 3 4 3 5% 7% 48%	2046
	21st to end	Night	18% 7% 2 6% 3 3 4 3 4 8% 42%	2200
October	1st to 10th	Night	20% 8% 2 6% 4 4 4 3 4 6% 38%	2390
	11th to 20th	Night	23% 12% 3 7% 4 4 4 3 4 5% 30%	2413
	21st to end	Night	25% 12% 4 8% 4 4 4 3 4 5% 26%	2860
November	1st to 10th	Night	22% 13% 4 7% 4 4 4 3 5% 6% 27%	2667
	11th to 20th	Night	18% 16% 6% 11% 6% 4 4 4 4 6% 23%	2888
	21st to end	Night	21% 19% 6% 12% 5% 5% 4 3 4 4 17%	2940
December	1st to 10th	Night	18% 19% 8% 15% 8% 5% 4 3 4 4 13%	4720
	11th to 20th	Night	23% 18% 5% 11% 6% 4 3 2 2 4 21%	5348
	21st to end	Night	21% 21% 4 11% 5% 3 3 2 3 4 23%	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% 4 6% 13% 4	4662
	11th to 20th	Day	75% 2 3 10% 9% 1	4680
	21st to end	Day	66% 4 8% 10% 11% 1	5124
February	1st to 10th	Day	64% 4 6% 16% 7% 2	1872
	11th to 20th	Day	63% 4 9% 13% 10% 1	1904
	21st to end	Day	65% 4 6% 14% 10% 2	1730
March	1st to 10th	Day	66% 4 6% 10% 11% 2	4579
	11th to 20th	Day	59% 4 14% 11% 11% 1	4869
	21st to end	Day	54% 4 7% 16% 17% 2	5893
April	1st to 10th	Day	57% 4 8% 16% 12% 3	2400
	11th to 20th	Day	55% 4 8% 19% 12% 2	2374
	21st to end	Day	58% 5% 7% 15% 12% 3	2568
May	1st to 10th	Day	61% 5% 8% 17% 7% 1	6357
	11th to 20th	Day	52% 7% 14% 17% 9% 1	6322
	21st to end	Day	55% 5% 10% 16% 13% 1	6949
June	1st to 10th	Day	55% 7% 10% 16% 11% 1	2800
	11th to 20th	Day	48% 7% 11% 21% 11% 2	2800
	21st to end	Day	56% 7% 10% 17% 9% 1	2800
July	1st to 10th	Day	52% 5% 14% 24% 6%	6290
	11th to 20th	Day	43% 5% 16% 29% 7%	6285
	21st to end	Day	37% 5% 17% 33% 8%	6728
August	1st to 10th	Day	51% 6% 17% 21% 6%	4549
	11th to 20th	Day	46% 6% 17% 25% 5%	4197
	21st to end	Day	45% 5% 15% 21% 12% 1	4312
September	1st to 10th	Day	43% 6% 13% 27% 11%	2400
	11th to 20th	Day	39% 7% 12% 30% 11% 1	2353
	21st to end	Day	46% 6% 12% 25% 11%	2200
October	1st to 10th	Day	50% 5% 11% 27% 7%	3265
	11th to 20th	Day	55% 5% 12% 21% 6% 1	3214
	21st to end	Day	56% 4 19% 14% 7% 1	3180
November	1st to 10th	Day	56% 6% 12% 18% 6% 1	1851
	11th to 20th	Day	66% 5% 9% 10% 9% 1	1727
	21st to end	Day	70% 5% 10% 10% 4 1	1680
December	1st to 10th	Day	76% 4 7% 9% 3	2680
	11th to 20th	Day	70% 4 6% 14% 6%	3066
	21st to end	Day	66% 4 8% 15% 7%	4048
January	1st to 10th	Night	71% 4 9% 12% 3	8234
	11th to 20th	Night	77% 3 7% 8% 4	8280
	21st to end	Night	68% 5% 6% 9% 11% 1	9057
February	1st to 10th	Night	63% 5% 8% 16% 7% 1	2746
	11th to 20th	Night	63% 3 9% 16% 8% 1	2612
	21st to end	Night	60% 4 9% 16% 9% 1	2076
March	1st to 10th	Night	63% 4 8% 11% 11% 3	5494
	11th to 20th	Night	56% 5% 12% 15% 9% 3	5228
	21st to end	Night	58% 3 7% 19% 10% 2	5038
April	1st to 10th	Night	56% 4 8% 17% 13% 2	2000
	11th to 20th	Night	50% 5% 9% 21% 14% 2	1975
	21st to end	Night	53% 4 9% 18% 13% 3	1845
May	1st to 10th	Night	56% 7% 10% 19% 7% 2	3600
	11th to 20th	Night	50% 7% 14% 17% 11% 2	3576
	21st to end	Night	56% 5% 10% 16% 12% 1	3927
June	1st to 10th	Night	50% 8% 10% 21% 11%	1600
	11th to 20th	Night	45% 8% 11% 22% 12% 3	1600
	21st to end	Night	49% 8% 10% 20% 12% 1	1600
July	1st to 10th	Night	51% 4 19% 20% 6%	3560
	11th to 20th	Night	44% 5% 18% 28% 6%	3552
	21st to end	Night	36% 5% 18% 30% 11%	3809
August	1st to 10th	Night	44% 7% 15% 27% 7%	2576
	11th to 20th	Night	45% 5% 19% 24% 7%	2882
	21st to end	Night	44% 5% 15% 23% 10% 2	3586
September	1st to 10th	Night	38% 7% 14% 28% 13% 1	2000
	11th to 20th	Night	36% 6% 14% 33% 10% 1	2046
	21st to end	Night	42% 6% 12% 28% 12%	2200
October	1st to 10th	Night	45% 5% 14% 23% 11% 1	3910
	11th to 20th	Night	52% 6% 13% 21% 9%	3924
	21st to end	Night	54% 4 17% 15% 9% 1	4610
November	1st to 10th	Night	57% 5% 12% 18% 6%	2667
	11th to 20th	Night	62% 5% 10% 14% 8% 1	2888
	21st to end	Night	70% 4 10% 12% 4	2940
December	1st to 10th	Night	75% 3 10% 9% 3	4720
	11th to 20th	Night	69% 3 5% 14% 9%	5348
	21st to end	Night	67% 3 5% 13% 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	32% 29% 27% 10% 2	322
	11th to 20th	Day	29% 29% 32% 9% 1	382
	21st to end	Day	32% 20% 33% 12% 2	446
March	1st to 10th	Day	30% 21% 33% 13% 3 1	540
	11th to 20th	Day	32% 23% 29% 14% 2 1	528
	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	522
	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% 35% 21% 6% 1	924
February	1st to 10th	Night	20% 20% 33% 20% 5% 1	840
	11th to 20th	Night	24% 21% 33% 18% 3	823
	21st to end	Night	25% 19% 30% 24% 3	692
March	1st to 10th	Night	27% 17% 32% 20% 3	840
	11th to 20th	Night	27% 20% 30% 18% 4 1	829
	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	28% 16% 28% 19% 8%	645
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% 35% 24% 2	574
	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 2026-03-15 02:23:55. Version ac07

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