Sommet du Mont Tremblant
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sommet du Mont Tremblant clear sky chart from 2005-11-06 to 2024-10-25.

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	19% 12% 4 9% 5% 5% 4 3 5% 6% 28%	101483
	Night	18% 13% 5% 9% 5% 4 4 3 4 5% 28%	97316
Transparency	Day	56% 6% 11% 17% 8% 1	101244
	Night	57% 7% 11% 16% 8% 1	97175
Seeing	Day	27% 19% 29% 17% 7% 2	14446
	Night	25% 15% 26% 23% 9% 1	23401

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	15% 19% 8% 20% 8% 6% 4 2 2 3 15%	2517
	11th to 20th	Day	13% 16% 6% 21% 11% 4 3 2 3 4 18%	2520
	21st to end	Day	11% 15% 9% 14% 7% 5% 6% 4 5% 5% 18%	2772
February	1st to 10th	Day	11% 20% 6% 14% 9% 5% 3 2 4 5% 20%	1688
	11th to 20th	Day	12% 20% 6% 14% 5% 6% 3 3 4 4 23%	1709
	21st to end	Day	16% 19% 4 10% 7% 5% 4 3 4 4 22%	1570
March	1st to 10th	Day	17% 18% 6% 10% 6% 5% 3 3 3 4 24%	3116
	11th to 20th	Day	13% 20% 8% 13% 6% 5% 3 2 3 5% 23%	3351
	21st to end	Day	13% 11% 4 10% 6% 5% 4 4 4 6% 34%	4120
April	1st to 10th	Day	20% 17% 4 9% 5% 3 2 3 4 5% 27%	2280
	11th to 20th	Day	23% 12% 4 7% 5% 4 3 3 4 4 31%	2254
	21st to end	Day	21% 12% 4 8% 5% 4 4 3 4 4 30%	2445
May	1st to 10th	Day	22% 11% 3 7% 5% 5% 4 4 5% 5% 28%	4426
	11th to 20th	Day	20% 8% 2 7% 5% 5% 5% 3 7% 7% 31%	4398
	21st to end	Day	21% 8% 3 7% 5% 5% 4 3 5% 6% 33%	4837
June	1st to 10th	Day	26% 9% 3 6% 5% 5% 5% 4 6% 6% 26%	2660
	11th to 20th	Day	19% 7% 3 7% 6% 5% 5% 4 5% 8% 31%	2660
	21st to end	Day	26% 8% 2 7% 6% 5% 5% 3 6% 6% 26%	2660
July	1st to 10th	Day	18% 8% 3 8% 5% 5% 5% 5% 7% 8% 29%	4440
	11th to 20th	Day	18% 8% 3 6% 4 5% 5% 5% 7% 8% 32%	4440
	21st to end	Day	15% 7% 3 6% 4 4 3 4 6% 7% 42%	4814
August	1st to 10th	Day	18% 8% 3 8% 6% 5% 6% 4 6% 8% 28%	4423
	11th to 20th	Day	19% 8% 3 6% 4 5% 5% 4 6% 7% 33%	4031
	21st to end	Day	18% 6% 2 6% 5% 5% 5% 4 6% 9% 35%	4180
September	1st to 10th	Day	20% 6% 2 6% 4 4 4 3 5% 6% 39%	2280
	11th to 20th	Day	19% 7% 2 6% 3 3 4 4 6% 6% 40%	2233
	21st to end	Day	24% 8% 2 5% 4 3 3 3 5% 6% 37%	2090
October	1st to 10th	Day	26% 10% 3 5% 4 4 4 3 4 7% 30%	1908
	11th to 20th	Day	28% 15% 3 9% 4 4 3 3 4 4 24%	1884
	21st to end	Day	28% 18% 4 6% 5% 3 3 2 4 5% 22%	1825
November	1st to 10th	Day	18% 18% 4 7% 3 3 4 3 4 6% 29%	1671
	11th to 20th	Day	22% 18% 6% 11% 6% 4 3 4 3 4 19%	1563
	21st to end	Day	21% 20% 6% 13% 6% 3 4 2 3 4 19%	1520
December	1st to 10th	Day	22% 23% 5% 11% 6% 3 3 3 4 5% 15%	1520
	11th to 20th	Day	20% 19% 6% 16% 7% 4 4 3 3 4 15%	1906
	21st to end	Day	20% 21% 6% 12% 5% 4 4 3 4 4 17%	2772
January	1st to 10th	Night	14% 22% 9% 13% 6% 4 4 3 4 4 18%	4429
	11th to 20th	Night	12% 15% 6% 17% 13% 5% 4 3 4 4 16%	4440
	21st to end	Night	10% 16% 10% 17% 8% 7% 5% 4 5% 5% 15%	4884
February	1st to 10th	Night	12% 18% 6% 12% 9% 5% 5% 3 4 5% 21%	2489
	11th to 20th	Night	13% 16% 8% 12% 7% 6% 4 3 4 4 21%	2356
	21st to end	Night	14% 17% 6% 11% 6% 4 5% 4 5% 6% 23%	1884
March	1st to 10th	Night	20% 14% 5% 10% 6% 4 5% 2 4 5% 27%	3724
	11th to 20th	Night	16% 21% 6% 11% 4 3 3 3 3 4 26%	3593
	21st to end	Night	15% 10% 5% 11% 5% 5% 4 3 4 4 32%	3512
April	1st to 10th	Night	23% 14% 4 7% 5% 4 3 3 4 6% 28%	1900
	11th to 20th	Night	21% 11% 3 5% 4 4 3 4 6% 5% 34%	1875
	21st to end	Night	20% 12% 3 8% 4 4 3 3 4 5% 34%	1749
May	1st to 10th	Night	21% 11% 3 7% 5% 4 4 4 5% 6% 30%	2514
	11th to 20th	Night	21% 8% 3 7% 4 3 4 2 4 7% 37%	2495
	21st to end	Night	22% 8% 2 6% 5% 5% 5% 4 4 7% 32%	2738
June	1st to 10th	Night	20% 8% 3 7% 5% 5% 5% 4 6% 7% 30%	1520
	11th to 20th	Night	19% 8% 2 6% 4 4 4 4 5% 7% 37%	1520
	21st to end	Night	21% 8% 2 5% 5% 5% 4 4 5% 5% 35%	1520
July	1st to 10th	Night	17% 8% 3 8% 6% 5% 5% 3 6% 7% 33%	2520
	11th to 20th	Night	20% 7% 3 6% 3 4 4 3 6% 6% 37%	2520
	21st to end	Night	13% 4 2 5% 4 4 4 4 7% 7% 46%	2739
August	1st to 10th	Night	16% 8% 3 7% 5% 4 4 4 5% 7% 37%	2506
	11th to 20th	Night	23% 7% 3 6% 3 4 4 3 5% 6% 37%	2761
	21st to end	Night	21% 7% 2 6% 4 4 4 3 4 7% 38%	3476
September	1st to 10th	Night	19% 8% 2 5% 3 4 4 3 4 6% 43%	1900
	11th to 20th	Night	18% 7% 2 4 3 4 3 3 4 6% 46%	1946
	21st to end	Night	20% 8% 2 6% 3 2 3 2 5% 8% 40%	2090
October	1st to 10th	Night	22% 9% 3 6% 3 5% 4 3 4 5% 36%	2270
	11th to 20th	Night	26% 14% 4 7% 4 4 3 3 3 4 28%	2295
	21st to end	Night	27% 16% 3 7% 5% 4 4 3 4 5% 24%	2637
November	1st to 10th	Night	22% 14% 4 7% 5% 4 4 4 4 6% 26%	2407
	11th to 20th	Night	18% 19% 6% 10% 6% 5% 4 3 4 5% 21%	2615
	21st to end	Night	23% 19% 6% 12% 5% 4 4 3 3 4 18%	2660
December	1st to 10th	Night	20% 22% 8% 14% 5% 4 3 2 4 3 14%	2660
	11th to 20th	Night	22% 19% 6% 11% 6% 4 4 2 3 4 19%	3288
	21st to end	Night	20% 23% 5% 13% 6% 4 4 2 3 3 17%	4884

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	75% 5% 7% 10% 3	2518
	11th to 20th	Day	72% 3 5% 13% 7% 1	2520
	21st to end	Day	67% 8% 8% 10% 6% 1	2772
February	1st to 10th	Day	67% 4 6% 15% 6% 2	1688
	11th to 20th	Day	64% 5% 9% 11% 9% 1	1718
	21st to end	Day	65% 5% 6% 13% 9% 2	1570
March	1st to 10th	Day	64% 6% 6% 12% 11% 1	3119
	11th to 20th	Day	65% 5% 9% 10% 9% 2	3351
	21st to end	Day	49% 6% 9% 19% 16% 2	4120
April	1st to 10th	Day	60% 3 9% 15% 10% 2	2280
	11th to 20th	Day	56% 4 9% 18% 11% 2	2254
	21st to end	Day	58% 5% 7% 15% 12% 3	2445
May	1st to 10th	Day	54% 8% 9% 20% 8% 1	4440
	11th to 20th	Day	49% 9% 16% 16% 8% 1	4402
	21st to end	Day	50% 7% 10% 18% 14% 1	4837
June	1st to 10th	Day	56% 7% 11% 15% 10% 1	2660
	11th to 20th	Day	49% 8% 11% 20% 10% 2	2660
	21st to end	Day	58% 8% 10% 16% 8%	2660
July	1st to 10th	Day	49% 8% 13% 22% 7%	4370
	11th to 20th	Day	47% 8% 18% 23% 5%	4365
	21st to end	Day	41% 7% 15% 28% 9%	4661
August	1st to 10th	Day	53% 7% 15% 20% 5%	4409
	11th to 20th	Day	48% 7% 16% 23% 5%	4073
	21st to end	Day	45% 7% 14% 20% 12% 1	4180
September	1st to 10th	Day	45% 6% 14% 23% 11%	2280
	11th to 20th	Day	42% 7% 14% 28% 9%	2233
	21st to end	Day	48% 7% 11% 24% 10%	2090
October	1st to 10th	Day	56% 5% 11% 20% 8% 1	1908
	11th to 20th	Day	64% 7% 9% 15% 5% 1	1884
	21st to end	Day	65% 6% 11% 12% 6% 1	1825
November	1st to 10th	Day	57% 6% 11% 18% 6% 1	1671
	11th to 20th	Day	69% 6% 8% 10% 6% 1	1563
	21st to end	Day	71% 5% 8% 10% 4 1	1520
December	1st to 10th	Day	73% 5% 8% 9% 5%	1520
	11th to 20th	Day	71% 7% 6% 11% 5%	1906
	21st to end	Day	71% 5% 6% 11% 6%	2772
January	1st to 10th	Night	69% 6% 11% 11% 3	4429
	11th to 20th	Night	69% 8% 9% 9% 4 1	4440
	21st to end	Night	69% 7% 8% 8% 7% 1	4884
February	1st to 10th	Night	65% 5% 9% 14% 6% 1	2489
	11th to 20th	Night	65% 5% 8% 13% 8% 1	2358
	21st to end	Night	61% 5% 9% 14% 9% 1	1884
March	1st to 10th	Night	59% 6% 10% 11% 10% 3	3734
	11th to 20th	Night	62% 6% 8% 12% 11% 1	3594
	21st to end	Night	53% 5% 9% 18% 11% 4	3512
April	1st to 10th	Night	57% 5% 9% 15% 12% 2	1900
	11th to 20th	Night	49% 7% 9% 21% 12% 2	1875
	21st to end	Night	52% 6% 9% 17% 13% 2	1749
May	1st to 10th	Night	50% 9% 14% 17% 8% 2	2520
	11th to 20th	Night	46% 8% 17% 16% 12% 2	2496
	21st to end	Night	50% 7% 10% 19% 12% 1	2739
June	1st to 10th	Night	51% 8% 12% 19% 9%	1520
	11th to 20th	Night	45% 7% 13% 21% 11% 3	1520
	21st to end	Night	51% 7% 11% 18% 12% 1	1520
July	1st to 10th	Night	50% 7% 16% 19% 8%	2480
	11th to 20th	Night	46% 7% 18% 23% 5%	2472
	21st to end	Night	35% 9% 19% 27% 11%	2651
August	1st to 10th	Night	45% 9% 14% 25% 6%	2496
	11th to 20th	Night	47% 6% 19% 22% 6%	2785
	21st to end	Night	46% 7% 15% 21% 9% 2	3476
September	1st to 10th	Night	41% 7% 14% 25% 13% 1	1900
	11th to 20th	Night	38% 6% 16% 30% 9% 1	1946
	21st to end	Night	42% 7% 13% 27% 10%	2090
October	1st to 10th	Night	50% 6% 11% 21% 11% 1	2270
	11th to 20th	Night	59% 6% 12% 16% 6% 1	2295
	21st to end	Night	64% 5% 10% 14% 6% 1	2637
November	1st to 10th	Night	58% 7% 13% 16% 5% 1	2407
	11th to 20th	Night	64% 6% 10% 12% 6% 2	2615
	21st to end	Night	71% 6% 9% 10% 4	2660
December	1st to 10th	Night	75% 6% 8% 8% 3	2660
	11th to 20th	Night	70% 6% 6% 12% 6% 1	3288
	21st to end	Night	73% 6% 5% 10% 6%	4884

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	19% 27% 38% 14% 2	180
	11th to 20th	Day	30% 18% 34% 13% 4 1	180
	21st to end	Day	21% 23% 37% 15% 4 1	198
February	1st to 10th	Day	31% 35% 27% 5% 2	260
	11th to 20th	Day	28% 31% 32% 9%	316
	21st to end	Day	31% 27% 27% 12% 3	382
March	1st to 10th	Day	27% 21% 33% 15% 3	460
	11th to 20th	Day	29% 23% 30% 15% 2 1	460
	21st to end	Day	32% 24% 25% 13% 6% 1	506
April	1st to 10th	Day	32% 19% 29% 13% 6% 1	460
	11th to 20th	Day	35% 18% 24% 11% 9% 2	452
	21st to end	Day	31% 23% 28% 12% 4 1	460
May	1st to 10th	Day	32% 21% 28% 14% 5% 1	463
	11th to 20th	Day	24% 19% 30% 18% 8% 1	487
	21st to end	Day	26% 20% 29% 16% 6% 1	529
June	1st to 10th	Day	30% 16% 33% 16% 4 1	490
	11th to 20th	Day	23% 21% 29% 18% 9% 1	490
	21st to end	Day	29% 15% 31% 18% 6% 1	490
July	1st to 10th	Day	17% 14% 35% 24% 8% 1	485
	11th to 20th	Day	19% 14% 33% 26% 7% 1	484
	21st to end	Day	17% 12% 34% 26% 9% 2	532
August	1st to 10th	Day	20% 13% 28% 28% 10% 1	486
	11th to 20th	Day	19% 8% 30% 27% 11% 6%	479
	21st to end	Day	21% 15% 29% 18% 12% 6%	539
September	1st to 10th	Day	22% 15% 28% 19% 11% 6%	490
	11th to 20th	Day	18% 13% 25% 22% 15% 8%	490
	21st to end	Day	23% 18% 21% 21% 11% 6%	490
October	1st to 10th	Day	29% 18% 22% 20% 9% 3	490
	11th to 20th	Day	35% 22% 22% 14% 6% 1	481
	21st to end	Day	37% 18% 23% 15% 5%	411
November	1st to 10th	Day	35% 16% 25% 19% 5% 1	365
	11th to 20th	Day	31% 24% 26% 11% 7%	223
	21st to end	Day	31% 29% 29% 9% 2	180
December	1st to 10th	Day	35% 17% 29% 14% 4 1	180
	11th to 20th	Day	31% 28% 27% 11% 2 1	180
	21st to end	Day	34% 23% 28% 10% 4 2	198
January	1st to 10th	Night	27% 21% 32% 16% 4	760
	11th to 20th	Night	28% 19% 28% 20% 5%	760
	21st to end	Night	18% 16% 37% 22% 6% 1	836
February	1st to 10th	Night	19% 23% 34% 18% 5%	760
	11th to 20th	Night	22% 23% 34% 17% 3	743
	21st to end	Night	25% 21% 28% 23% 3	628
March	1st to 10th	Night	26% 17% 31% 21% 4	760
	11th to 20th	Night	27% 21% 28% 18% 4 1	760
	21st to end	Night	24% 17% 29% 22% 7%	836
April	1st to 10th	Night	30% 16% 26% 23% 4	760
	11th to 20th	Night	28% 17% 26% 21% 7% 1	751
	21st to end	Night	27% 17% 27% 20% 9%	609
May	1st to 10th	Night	25% 10% 28% 25% 11% 2	380
	11th to 20th	Night	24% 10% 28% 28% 9%	374
	21st to end	Night	22% 10% 33% 27% 8%	411
June	1st to 10th	Night	22% 10% 29% 29% 9%	380
	11th to 20th	Night	21% 9% 23% 32% 14% 1	380
	21st to end	Night	24% 4 19% 37% 15% 1	380
July	1st to 10th	Night	16% 8% 24% 41% 12% 1	370
	11th to 20th	Night	16% 7% 19% 40% 18% 1	368
	21st to end	Night	14% 6% 24% 39% 15% 1	416
August	1st to 10th	Night	17% 3 20% 40% 19%	378
	11th to 20th	Night	18% 5% 18% 33% 23% 2	537
	21st to end	Night	19% 10% 23% 28% 17% 3	836
September	1st to 10th	Night	22% 8% 23% 30% 16% 1	760
	11th to 20th	Night	22% 7% 18% 30% 22% 2	760
	21st to end	Night	22% 11% 22% 24% 18% 2	760
October	1st to 10th	Night	26% 13% 21% 25% 13% 1	760
	11th to 20th	Night	32% 13% 24% 21% 9% 1	760
	21st to end	Night	33% 17% 23% 21% 6%	812
November	1st to 10th	Night	28% 18% 25% 21% 7% 1	740
	11th to 20th	Night	27% 20% 28% 16% 9% 1	760
	21st to end	Night	33% 21% 23% 16% 5% 1	760
December	1st to 10th	Night	32% 20% 25% 17% 6%	760
	11th to 20th	Night	30% 20% 27% 16% 5% 1	760
	21st to end	Night	34% 18% 26% 17% 4	836

Page generated at 2024-10-22 20:20:59. Version ac07

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