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 2024-02-25.

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	20% 12% 4 8% 6% 3 4 4 5% 6% 27%	78223
	Night	18% 13% 5% 9% 7% 3 4 4 4 5% 27%	81071
Transparency	Day	58% 6% 10% 16% 8% 1	77928
	Night	58% 7% 10% 16% 8% 1	80900
Seeing	Day	27% 19% 28% 17% 7% 2	13476
	Night	25% 15% 26% 23% 9% 1	22650

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	16% 18% 8% 18% 9% 4 4 3 2 3 15%	2517
	11th to 20th	Day	13% 16% 6% 18% 14% 4 3 2 2 4 19%	2520
	21st to end	Day	12% 15% 9% 13% 8% 4 6% 5% 5% 5% 18%	2772
February	1st to 10th	Day	11% 19% 7% 12% 11% 4 4 3 4 5% 20%	1688
	11th to 20th	Day	12% 19% 7% 12% 6% 4 4 4 4 4 23%	1709
	21st to end	Day	16% 19% 5% 10% 8% 4 4 4 4 4 22%	1520
March	1st to 10th	Day	15% 13% 7% 10% 8% 4 4 3 4 6% 26%	1797
	11th to 20th	Day	16% 15% 6% 9% 6% 4 5% 4 4 7% 26%	1907
	21st to end	Day	19% 11% 4 8% 6% 3 4 4 4 6% 32%	2344
April	1st to 10th	Day	21% 16% 5% 8% 5% 3 3 3 4 5% 27%	2160
	11th to 20th	Day	23% 11% 4 6% 5% 3 3 3 4 4 32%	2134
	21st to end	Day	22% 11% 5% 7% 6% 4 4 4 4 5% 29%	2316
May	1st to 10th	Day	24% 10% 4 6% 5% 3 4 4 4 5% 31%	2520
	11th to 20th	Day	21% 9% 2 6% 7% 3 5% 4 4 5% 34%	2478
	21st to end	Day	22% 8% 3 6% 5% 3 4 4 5% 7% 33%	2725
June	1st to 10th	Day	27% 8% 3 6% 5% 4 5% 5% 6% 6% 26%	2520
	11th to 20th	Day	20% 6% 3 6% 6% 4 6% 5% 5% 8% 32%	2520
	21st to end	Day	26% 7% 3 6% 6% 3 5% 4 6% 6% 27%	2520
July	1st to 10th	Day	19% 6% 2 6% 5% 4 5% 6% 6% 8% 34%	2520
	11th to 20th	Day	17% 6% 3 6% 6% 3 5% 6% 7% 9% 31%	2520
	21st to end	Day	16% 7% 4 6% 6% 3 6% 5% 7% 8% 32%	2744
August	1st to 10th	Day	18% 8% 3 7% 6% 4 5% 5% 6% 8% 29%	2506
	11th to 20th	Day	18% 6% 3 6% 6% 4 6% 5% 5% 8% 33%	2307
	21st to end	Day	18% 6% 3 5% 6% 4 5% 4 5% 8% 35%	2376
September	1st to 10th	Day	20% 5% 2 6% 5% 3 4 4 5% 6% 39%	2160
	11th to 20th	Day	20% 7% 3 5% 4 3 4 5% 6% 6% 38%	2116
	21st to end	Day	24% 7% 2 4 5% 3 3 4 5% 6% 38%	1980
October	1st to 10th	Day	27% 10% 3 4 4 3 4 4 3 7% 30%	1808
	11th to 20th	Day	30% 14% 3 7% 6% 3 3 3 3 4 23%	1785
	21st to end	Day	29% 17% 4 5% 6% 3 3 3 3 5% 22%	1782
November	1st to 10th	Day	19% 17% 4 7% 4 2 4 4 3 6% 29%	1671
	11th to 20th	Day	22% 17% 7% 10% 7% 3 3 4 3 4 19%	1563
	21st to end	Day	21% 19% 7% 11% 7% 3 3 3 3 4 19%	1520
December	1st to 10th	Day	23% 21% 6% 10% 7% 3 3 4 4 5% 15%	1520
	11th to 20th	Day	21% 17% 7% 14% 8% 3 4 3 3 4 15%	1906
	21st to end	Day	21% 20% 6% 12% 6% 3 5% 3 4 4 17%	2772
January	1st to 10th	Night	15% 21% 9% 12% 7% 3 4 4 4 4 18%	4429
	11th to 20th	Night	12% 14% 7% 14% 16% 4 4 4 4 4 16%	4440
	21st to end	Night	10% 15% 10% 15% 9% 5% 6% 4 5% 5% 15%	4884
February	1st to 10th	Night	13% 17% 7% 10% 10% 3 6% 4 4 5% 21%	2489
	11th to 20th	Night	14% 15% 9% 11% 9% 5% 5% 4 4 4 22%	2356
	21st to end	Night	14% 16% 6% 10% 6% 3 5% 4 5% 5% 24%	1831
March	1st to 10th	Night	17% 12% 5% 10% 8% 5% 5% 4 4 5% 24%	2150
	11th to 20th	Night	19% 15% 5% 8% 6% 3 5% 4 4 5% 28%	2051
	21st to end	Night	17% 10% 4 8% 5% 3 5% 4 5% 4 36%	2012
April	1st to 10th	Night	24% 12% 5% 7% 5% 3 3 4 4 6% 28%	1800
	11th to 20th	Night	20% 10% 3 5% 5% 3 3 4 5% 5% 36%	1775
	21st to end	Night	20% 11% 4 7% 5% 3 4 3 4 5% 33%	1657
May	1st to 10th	Night	22% 10% 3 6% 5% 2 4 5% 4 6% 34%	1440
	11th to 20th	Night	21% 9% 3 5% 5% 3 4 3 4 7% 37%	1415
	21st to end	Night	19% 8% 3 5% 5% 3 5% 4 4 8% 38%	1550
June	1st to 10th	Night	20% 7% 4 6% 6% 4 5% 5% 6% 7% 31%	1440
	11th to 20th	Night	19% 7% 2 5% 5% 3 4 5% 5% 7% 37%	1440
	21st to end	Night	20% 7% 2 5% 5% 4 5% 5% 6% 5% 35%	1440
July	1st to 10th	Night	14% 5% 4 6% 5% 4 5% 3 5% 8% 42%	1440
	11th to 20th	Night	16% 5% 3 4 5% 2 5% 4 7% 7% 41%	1440
	21st to end	Night	15% 5% 2 5% 4 3 4 5% 8% 8% 39%	1574
August	1st to 10th	Night	14% 6% 2 5% 5% 3 5% 5% 6% 8% 39%	1432
	11th to 20th	Night	15% 6% 3 5% 4 4 4 4 5% 8% 41%	1571
	21st to end	Night	18% 7% 3 5% 5% 3 4 4 5% 8% 39%	1980
September	1st to 10th	Night	19% 8% 2 5% 3 3 4 4 5% 6% 42%	1800
	11th to 20th	Night	19% 7% 2 4 4 3 3 4 4 6% 44%	1843
	21st to end	Night	20% 8% 2 5% 4 2 3 3 5% 8% 40%	1980
October	1st to 10th	Night	23% 8% 3 5% 4 4 4 4 4 6% 35%	2150
	11th to 20th	Night	27% 14% 4 6% 5% 3 3 3 3 5% 27%	2174
	21st to end	Night	28% 15% 4 6% 6% 3 4 4 3 5% 23%	2574
November	1st to 10th	Night	22% 14% 5% 6% 5% 3 4 4 5% 6% 26%	2407
	11th to 20th	Night	19% 17% 7% 10% 7% 3 4 4 4 5% 21%	2615
	21st to end	Night	23% 18% 6% 11% 6% 3 4 3 3 4 18%	2660
December	1st to 10th	Night	20% 21% 9% 13% 7% 3 4 3 4 3 14%	2660
	11th to 20th	Night	22% 18% 7% 10% 7% 4 4 3 3 4 19%	3288
	21st to end	Night	21% 23% 5% 11% 8% 3 4 3 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	66% 5% 5% 13% 9% 2	1520
March	1st to 10th	Day	61% 5% 7% 15% 9% 2	1800
	11th to 20th	Day	60% 5% 9% 13% 11% 2	1907
	21st to end	Day	55% 5% 8% 16% 12% 3	2344
April	1st to 10th	Day	61% 3 10% 14% 10% 2	2160
	11th to 20th	Day	56% 4 9% 18% 11% 2	2134
	21st to end	Day	58% 5% 8% 14% 11% 3	2316
May	1st to 10th	Day	55% 5% 7% 18% 12% 2	2520
	11th to 20th	Day	53% 6% 8% 17% 14% 2	2482
	21st to end	Day	52% 6% 11% 18% 12% 1	2725
June	1st to 10th	Day	56% 7% 11% 15% 9% 1	2520
	11th to 20th	Day	50% 8% 11% 20% 9% 2	2520
	21st to end	Day	57% 8% 10% 16% 8%	2520
July	1st to 10th	Day	45% 9% 13% 24% 9%	2450
	11th to 20th	Day	46% 9% 15% 22% 9%	2445
	21st to end	Day	49% 9% 14% 20% 8%	2591
August	1st to 10th	Day	52% 9% 15% 20% 4	2492
	11th to 20th	Day	47% 9% 17% 20% 7%	2307
	21st to end	Day	47% 7% 14% 21% 11% 1	2376
September	1st to 10th	Day	45% 6% 14% 22% 12%	2160
	11th to 20th	Day	44% 7% 13% 27% 9%	2116
	21st to end	Day	48% 7% 12% 24% 9%	1980
October	1st to 10th	Day	56% 5% 11% 19% 8% 1	1808
	11th to 20th	Day	65% 7% 9% 14% 4 1	1785
	21st to end	Day	66% 6% 10% 12% 6% 1	1782
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% 10% 1	1831
March	1st to 10th	Night	62% 6% 8% 14% 8% 2	2160
	11th to 20th	Night	59% 5% 10% 13% 11% 1	2052
	21st to end	Night	51% 5% 9% 19% 12% 4	2012
April	1st to 10th	Night	57% 5% 9% 15% 11% 2	1800
	11th to 20th	Night	48% 6% 10% 21% 13% 2	1775
	21st to end	Night	53% 6% 9% 17% 13% 2	1657
May	1st to 10th	Night	50% 5% 10% 19% 13% 3	1440
	11th to 20th	Night	48% 6% 10% 17% 16% 3	1416
	21st to end	Night	46% 7% 12% 21% 12% 2	1551
June	1st to 10th	Night	50% 8% 12% 19% 9%	1440
	11th to 20th	Night	45% 7% 12% 22% 11% 3	1440
	21st to end	Night	50% 7% 12% 19% 11% 1	1440
July	1st to 10th	Night	40% 9% 15% 24% 11% 1	1400
	11th to 20th	Night	41% 8% 16% 26% 9% 1	1392
	21st to end	Night	39% 11% 17% 24% 8%	1486
August	1st to 10th	Night	40% 12% 17% 25% 6%	1422
	11th to 20th	Night	40% 9% 18% 24% 9%	1571
	21st to end	Night	43% 8% 16% 24% 9%	1980
September	1st to 10th	Night	41% 7% 14% 25% 12% 1	1800
	11th to 20th	Night	40% 6% 15% 30% 8% 1	1843
	21st to end	Night	42% 7% 13% 28% 10%	1980
October	1st to 10th	Night	51% 6% 10% 22% 11% 1	2150
	11th to 20th	Night	60% 6% 12% 16% 6% 1	2174
	21st to end	Night	65% 6% 9% 14% 6% 1	2574
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% 25% 28% 13% 3	362
March	1st to 10th	Day	27% 22% 32% 15% 3	420
	11th to 20th	Day	29% 23% 29% 15% 2 1	420
	21st to end	Day	32% 21% 25% 14% 6% 2	462
April	1st to 10th	Day	32% 18% 29% 14% 6% 1	420
	11th to 20th	Day	34% 18% 24% 12% 10% 2	412
	21st to end	Day	30% 22% 29% 13% 4 1	420
May	1st to 10th	Day	32% 21% 27% 15% 4 1	423
	11th to 20th	Day	26% 19% 29% 17% 7% 1	447
	21st to end	Day	26% 21% 29% 16% 6% 1	485
June	1st to 10th	Day	31% 16% 32% 15% 4 1	450
	11th to 20th	Day	23% 21% 28% 18% 9% 1	450
	21st to end	Day	27% 14% 31% 20% 7% 1	450
July	1st to 10th	Day	17% 13% 35% 24% 9% 2	445
	11th to 20th	Day	18% 14% 33% 27% 8%	444
	21st to end	Day	17% 13% 34% 26% 10% 2	488
August	1st to 10th	Day	20% 13% 27% 28% 11% 1	446
	11th to 20th	Day	18% 7% 31% 26% 11% 6%	439
	21st to end	Day	21% 15% 28% 17% 12% 6%	495
September	1st to 10th	Day	21% 15% 27% 20% 11% 6%	450
	11th to 20th	Day	19% 14% 27% 21% 13% 6%	450
	21st to end	Day	22% 18% 22% 21% 10% 6%	450
October	1st to 10th	Day	28% 19% 22% 19% 9% 3	450
	11th to 20th	Day	36% 21% 21% 14% 6% 1	442
	21st to end	Day	38% 18% 23% 15% 5% 1	396
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% 20% 28% 23% 3	611
March	1st to 10th	Night	25% 18% 32% 21% 4	720
	11th to 20th	Night	28% 20% 28% 18% 5% 1	720
	21st to end	Night	24% 17% 29% 23% 8% 1	792
April	1st to 10th	Night	30% 16% 25% 23% 4	720
	11th to 20th	Night	27% 16% 26% 22% 8% 1	711
	21st to end	Night	27% 17% 27% 21% 9%	577
May	1st to 10th	Night	25% 10% 27% 25% 11% 2	360
	11th to 20th	Night	25% 10% 28% 27% 9%	354
	21st to end	Night	22% 10% 32% 27% 8% 1	389
June	1st to 10th	Night	23% 10% 30% 29% 8%	360
	11th to 20th	Night	21% 8% 23% 32% 15% 1	360
	21st to end	Night	23% 4 19% 38% 16% 1	360
July	1st to 10th	Night	15% 7% 24% 40% 12% 1	350
	11th to 20th	Night	16% 6% 19% 39% 19% 1	348
	21st to end	Night	14% 7% 24% 39% 15% 2	394
August	1st to 10th	Night	17% 3 20% 40% 20%	358
	11th to 20th	Night	17% 6% 18% 35% 23% 2	507
	21st to end	Night	19% 10% 24% 28% 16% 3	792
September	1st to 10th	Night	22% 9% 22% 30% 17% 1	720
	11th to 20th	Night	23% 7% 19% 31% 19% 2	720
	21st to end	Night	23% 11% 22% 24% 18% 2	720
October	1st to 10th	Night	27% 13% 22% 25% 13% 1	720
	11th to 20th	Night	32% 13% 24% 21% 8% 1	720
	21st to end	Night	34% 17% 23% 20% 6%	792
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 2024-02-22 06:05:43. Version ac07

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