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 2024-12-06.

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% 29%	101826
	Night	18% 13% 4 9% 5% 4 4 3 5% 5% 29%	97877
Transparency	Day	55% 6% 12% 19% 9% 1	105275
	Night	56% 5% 12% 18% 9% 1	102517
Seeing	Day	27% 18% 29% 18% 7% 2	14551
	Night	25% 14% 27% 24% 9% 1	23579

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% 20% 7% 18% 8% 4 5% 2 2 3 15%	2517
	11th to 20th	Day	14% 16% 7% 21% 10% 3 2 2 3 5% 18%	2520
	21st to end	Day	11% 17% 9% 13% 7% 6% 5% 4 5% 5% 18%	2772
February	1st to 10th	Day	11% 19% 6% 14% 8% 4 4 3 4 5% 21%	1693
	11th to 20th	Day	12% 20% 5% 13% 6% 5% 4 2 4 5% 24%	1709
	21st to end	Day	16% 19% 5% 10% 7% 5% 4 3 4 4 23%	1570
March	1st to 10th	Day	18% 17% 4 10% 7% 4 4 3 4 5% 24%	3116
	11th to 20th	Day	13% 18% 8% 14% 6% 5% 4 3 4 5% 23%	3352
	21st to end	Day	14% 10% 3 9% 6% 4 4 4 5% 6% 35%	4117
April	1st to 10th	Day	20% 16% 4 9% 4 4 3 2 4 5% 29%	2280
	11th to 20th	Day	22% 11% 4 7% 5% 4 4 3 4 5% 31%	2254
	21st to end	Day	22% 11% 3 9% 5% 4 4 4 4 4 30%	2439
May	1st to 10th	Day	22% 11% 3 7% 5% 4 5% 4 5% 6% 28%	4426
	11th to 20th	Day	19% 7% 3 8% 6% 5% 5% 4 6% 7% 31%	4398
	21st to end	Day	18% 9% 3 8% 5% 5% 4 4 6% 7% 33%	4837
June	1st to 10th	Day	24% 10% 2 7% 5% 5% 5% 4 6% 7% 25%	2660
	11th to 20th	Day	17% 7% 3 7% 6% 5% 5% 4 6% 7% 32%	2660
	21st to end	Day	23% 8% 3 7% 6% 5% 5% 4 5% 7% 26%	2660
July	1st to 10th	Day	15% 8% 3 7% 5% 5% 5% 5% 7% 9% 30%	4440
	11th to 20th	Day	16% 8% 3 7% 5% 5% 5% 4 7% 7% 32%	4440
	21st to end	Day	13% 7% 2 6% 4 4 4 3 6% 7% 43%	4814
August	1st to 10th	Day	16% 7% 3 8% 6% 6% 6% 4 6% 9% 28%	4423
	11th to 20th	Day	17% 8% 3 6% 5% 4 5% 4 7% 8% 34%	4026
	21st to end	Day	17% 5% 2 6% 5% 5% 5% 4 6% 8% 36%	4180
September	1st to 10th	Day	19% 6% 2 6% 4 5% 4 3 5% 6% 40%	2280
	11th to 20th	Day	17% 7% 2 6% 3 4 4 4 7% 7% 42%	2236
	21st to end	Day	22% 7% 2 5% 4 4 3 3 5% 7% 37%	2090
October	1st to 10th	Day	24% 11% 2 7% 4 4 4 3 5% 7% 31%	1905
	11th to 20th	Day	27% 14% 3 8% 5% 4 4 3 4 5% 24%	1887
	21st to end	Day	26% 16% 4 8% 4 4 3 3 4 5% 23%	1881
November	1st to 10th	Day	18% 14% 3 9% 4 3 4 3 6% 6% 29%	1761
	11th to 20th	Day	20% 17% 6% 10% 6% 5% 4 3 4 5% 21%	1645
	21st to end	Day	23% 17% 6% 13% 5% 4 4 2 3 4 19%	1600
December	1st to 10th	Day	23% 22% 6% 10% 5% 4 4 3 5% 5% 15%	1560
	11th to 20th	Day	21% 18% 6% 13% 6% 4 4 3 4 3 18%	1906
	21st to end	Day	21% 21% 6% 12% 5% 3 4 2 4 4 18%	2772
January	1st to 10th	Night	16% 20% 8% 12% 6% 4 4 3 3 4 19%	4429
	11th to 20th	Night	12% 15% 7% 18% 10% 5% 3 3 4 4 17%	4440
	21st to end	Night	10% 17% 9% 16% 8% 7% 5% 3 4 4 16%	4884
February	1st to 10th	Night	12% 18% 5% 12% 8% 5% 4 4 4 5% 22%	2485
	11th to 20th	Night	13% 16% 7% 12% 8% 5% 4 3 3 5% 24%	2356
	21st to end	Night	15% 16% 6% 10% 5% 5% 4 4 5% 6% 25%	1884
March	1st to 10th	Night	21% 13% 4 8% 6% 4 4 2 4 4 29%	3724
	11th to 20th	Night	16% 19% 5% 11% 5% 4 3 3 3 4 26%	3589
	21st to end	Night	15% 11% 4 9% 6% 5% 4 3 5% 5% 34%	3514
April	1st to 10th	Night	23% 13% 3 7% 5% 3 4 2 5% 6% 29%	1900
	11th to 20th	Night	21% 9% 3 6% 4 4 3 3 6% 6% 35%	1875
	21st to end	Night	20% 12% 3 8% 4 4 4 3 5% 5% 34%	1753
May	1st to 10th	Night	19% 10% 3 8% 4 4 5% 3 6% 6% 31%	2514
	11th to 20th	Night	20% 8% 3 7% 4 4 3 3 4 7% 37%	2495
	21st to end	Night	19% 7% 3 7% 5% 5% 5% 4 5% 6% 34%	2738
June	1st to 10th	Night	19% 8% 3 8% 4 5% 5% 4 6% 7% 31%	1520
	11th to 20th	Night	16% 8% 2 6% 4 4 4 5% 6% 8% 37%	1520
	21st to end	Night	21% 7% 3 6% 5% 4 5% 4 5% 6% 35%	1520
July	1st to 10th	Night	15% 8% 3 9% 6% 5% 5% 4 5% 8% 33%	2520
	11th to 20th	Night	18% 7% 3 6% 4 4 4 4 6% 7% 37%	2520
	21st to end	Night	12% 4 2 5% 4 4 4 4 7% 8% 46%	2739
August	1st to 10th	Night	14% 8% 3 8% 5% 4 4 4 6% 7% 38%	2506
	11th to 20th	Night	19% 7% 3 7% 4 4 4 3 6% 5% 39%	2768
	21st to end	Night	19% 7% 2 6% 4 4 4 3 5% 7% 39%	3476
September	1st to 10th	Night	16% 8% 2 5% 4 3 3 3 5% 6% 44%	1900
	11th to 20th	Night	17% 6% 2 4 3 3 4 3 5% 7% 46%	1943
	21st to end	Night	18% 7% 2 6% 3 3 4 3 4 9% 41%	2090
October	1st to 10th	Night	21% 8% 2 7% 4 4 4 3 4 6% 36%	2270
	11th to 20th	Night	24% 13% 3 7% 4 4 4 3 4 5% 29%	2292
	21st to end	Night	26% 12% 3 8% 4 4 4 3 4 5% 26%	2717
November	1st to 10th	Night	21% 13% 4 7% 4 4 4 3 5% 6% 27%	2537
	11th to 20th	Night	18% 16% 5% 10% 6% 4 4 4 4 6% 23%	2750
	21st to end	Night	22% 18% 6% 11% 5% 5% 4 3 4 5% 18%	2800
December	1st to 10th	Night	21% 22% 7% 13% 6% 4 3 3 4 4 14%	2737
	11th to 20th	Night	22% 18% 5% 10% 6% 4 3 2 3 4 21%	3288
	21st to end	Night	23% 22% 5% 12% 5% 3 3 2 3 4 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	74% 5% 7% 10% 4	2518
	11th to 20th	Day	72% 3 5% 14% 6% 1	2520
	21st to end	Day	67% 6% 10% 10% 6% 1	2772
February	1st to 10th	Day	65% 4 7% 16% 6% 2	1693
	11th to 20th	Day	63% 5% 9% 12% 10% 1	1718
	21st to end	Day	64% 4 7% 14% 10% 2	1570
March	1st to 10th	Day	62% 5% 8% 14% 10% 1	3119
	11th to 20th	Day	64% 5% 10% 11% 10% 2	3352
	21st to end	Day	48% 5% 9% 20% 17% 2	4117
April	1st to 10th	Day	58% 4 9% 16% 11% 3	2280
	11th to 20th	Day	55% 4 8% 19% 12% 2	2254
	21st to end	Day	57% 5% 7% 15% 12% 3	2439
May	1st to 10th	Day	55% 6% 10% 20% 8% 2	4440
	11th to 20th	Day	49% 9% 15% 16% 9% 1	4402
	21st to end	Day	49% 6% 10% 19% 14% 1	4837
June	1st to 10th	Day	56% 7% 10% 16% 10% 1	2660
	11th to 20th	Day	48% 7% 11% 20% 11% 3	2660
	21st to end	Day	57% 8% 10% 17% 9%	2660
July	1st to 10th	Day	48% 6% 15% 24% 7%	4370
	11th to 20th	Day	47% 6% 17% 24% 6%	4365
	21st to end	Day	40% 6% 15% 30% 8%	4661
August	1st to 10th	Day	52% 6% 16% 21% 6%	4409
	11th to 20th	Day	47% 6% 17% 25% 5%	4068
	21st to end	Day	45% 5% 15% 21% 12% 1	4180
September	1st to 10th	Day	44% 6% 12% 26% 12%	2280
	11th to 20th	Day	40% 7% 13% 29% 11% 1	2236
	21st to end	Day	46% 6% 12% 26% 10%	2090
October	1st to 10th	Day	51% 5% 11% 26% 6%	3165
	11th to 20th	Day	55% 5% 12% 21% 6%	3115
	21st to end	Day	56% 4 19% 13% 7% 1	3081
November	1st to 10th	Day	54% 6% 13% 19% 7% 1	1761
	11th to 20th	Day	65% 5% 9% 11% 9% 1	1645
	21st to end	Day	69% 5% 11% 10% 4 1	1600
December	1st to 10th	Day	72% 6% 8% 10% 4	1560
	11th to 20th	Day	69% 5% 9% 12% 5%	1906
	21st to end	Day	71% 4 6% 13% 6%	2772
January	1st to 10th	Night	67% 6% 13% 11% 3	4429
	11th to 20th	Night	67% 5% 10% 12% 5% 1	4440
	21st to end	Night	69% 6% 9% 8% 7% 1	4884
February	1st to 10th	Night	63% 5% 8% 16% 7% 1	2485
	11th to 20th	Night	63% 4 9% 15% 8% 1	2358
	21st to end	Night	59% 4 9% 16% 10% 2	1884
March	1st to 10th	Night	57% 5% 10% 14% 10% 3	3734
	11th to 20th	Night	62% 5% 9% 14% 10% 1	3590
	21st to end	Night	52% 4 8% 19% 14% 3	3514
April	1st to 10th	Night	56% 4 8% 17% 13% 2	1900
	11th to 20th	Night	49% 5% 9% 21% 14% 2	1875
	21st to end	Night	52% 4 9% 18% 13% 3	1753
May	1st to 10th	Night	51% 8% 12% 19% 8% 2	2520
	11th to 20th	Night	45% 8% 16% 16% 12% 2	2496
	21st to end	Night	49% 6% 10% 19% 14% 2	2739
June	1st to 10th	Night	49% 8% 11% 21% 10%	1520
	11th to 20th	Night	44% 8% 11% 22% 12% 3	1520
	21st to end	Night	49% 8% 10% 20% 12% 1	1520
July	1st to 10th	Night	49% 5% 17% 19% 9%	2480
	11th to 20th	Night	44% 6% 18% 25% 6%	2472
	21st to end	Night	35% 6% 20% 27% 11%	2651
August	1st to 10th	Night	45% 7% 15% 26% 7%	2496
	11th to 20th	Night	46% 5% 19% 23% 6%	2792
	21st to end	Night	44% 5% 15% 23% 11% 2	3476
September	1st to 10th	Night	39% 7% 13% 27% 13% 1	1900
	11th to 20th	Night	37% 6% 14% 32% 10% 1	1943
	21st to end	Night	42% 6% 12% 29% 11%	2090
October	1st to 10th	Night	46% 6% 14% 23% 10%	3790
	11th to 20th	Night	52% 6% 13% 21% 8%	3803
	21st to end	Night	54% 4 17% 14% 9% 1	4467
November	1st to 10th	Night	57% 6% 13% 18% 6%	2537
	11th to 20th	Night	61% 5% 10% 14% 8% 1	2750
	21st to end	Night	69% 5% 10% 12% 4	2800
December	1st to 10th	Night	74% 5% 8% 10% 4	2737
	11th to 20th	Night	68% 3 7% 14% 6% 1	3288
	21st to end	Night	72% 4 6% 13% 5%	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	23% 22% 37% 16% 3	180
	11th to 20th	Day	28% 23% 29% 13% 6% 1	180
	21st to end	Day	23% 23% 33% 16% 4 2	198
February	1st to 10th	Day	35% 30% 27% 7% 2	263
	11th to 20th	Day	28% 32% 31% 9%	316
	21st to end	Day	34% 21% 30% 13% 2	382
March	1st to 10th	Day	28% 19% 33% 15% 3 1	460
	11th to 20th	Day	29% 23% 30% 15% 2 1	460
	21st to end	Day	32% 22% 25% 15% 6% 1	506
April	1st to 10th	Day	32% 19% 30% 14% 4 1	460
	11th to 20th	Day	35% 18% 23% 14% 8% 2	452
	21st to end	Day	33% 19% 29% 14% 4 1	460
May	1st to 10th	Day	29% 21% 30% 13% 5% 1	463
	11th to 20th	Day	25% 17% 31% 20% 7% 1	487
	21st to end	Day	26% 19% 30% 18% 6% 1	529
June	1st to 10th	Day	29% 17% 31% 17% 6%	490
	11th to 20th	Day	20% 18% 31% 19% 10% 1	490
	21st to end	Day	28% 15% 31% 18% 8% 1	490
July	1st to 10th	Day	19% 12% 34% 24% 9% 2	485
	11th to 20th	Day	17% 12% 36% 26% 7% 1	484
	21st to end	Day	17% 10% 36% 26% 9% 2	532
August	1st to 10th	Day	19% 12% 27% 30% 10% 2	486
	11th to 20th	Day	19% 8% 27% 26% 14% 7%	479
	21st to end	Day	20% 16% 27% 20% 12% 6%	539
September	1st to 10th	Day	22% 9% 31% 19% 12% 6%	490
	11th to 20th	Day	16% 13% 24% 22% 16% 9%	490
	21st to end	Day	22% 16% 25% 21% 10% 6%	490
October	1st to 10th	Day	31% 17% 20% 18% 12% 2	490
	11th to 20th	Day	34% 20% 24% 14% 7% 1	483
	21st to end	Day	37% 14% 28% 17% 4	429
November	1st to 10th	Day	37% 15% 25% 18% 4 1	395
	11th to 20th	Day	31% 23% 27% 13% 6%	245
	21st to end	Day	32% 27% 29% 12% 1 1	200
December	1st to 10th	Day	34% 19% 29% 13% 4 1	190
	11th to 20th	Day	31% 29% 29% 9% 1 1	180
	21st to end	Day	37% 22% 27% 10% 3 2	198
January	1st to 10th	Night	29% 16% 34% 16% 3	760
	11th to 20th	Night	31% 18% 28% 18% 5%	760
	21st to end	Night	20% 16% 35% 21% 6% 1	836
February	1st to 10th	Night	21% 20% 34% 20% 4 1	760
	11th to 20th	Night	24% 21% 33% 19% 3	743
	21st to end	Night	25% 20% 28% 24% 3	628
March	1st to 10th	Night	27% 17% 31% 22% 4	760
	11th to 20th	Night	26% 20% 30% 19% 4 1	760
	21st to end	Night	26% 14% 30% 23% 6% 1	836
April	1st to 10th	Night	30% 15% 27% 23% 5%	760
	11th to 20th	Night	27% 15% 28% 23% 6%	751
	21st to end	Night	28% 16% 27% 20% 8%	613
May	1st to 10th	Night	26% 11% 28% 25% 9% 2	380
	11th to 20th	Night	22% 10% 30% 30% 8%	374
	21st to end	Night	19% 10% 35% 27% 9%	411
June	1st to 10th	Night	23% 8% 30% 30% 9% 1	380
	11th to 20th	Night	20% 7% 28% 31% 12% 1	380
	21st to end	Night	22% 6% 21% 35% 16%	380
July	1st to 10th	Night	14% 6% 26% 39% 14% 1	370
	11th to 20th	Night	14% 5% 24% 38% 18% 1	368
	21st to end	Night	14% 6% 25% 40% 15% 1	416
August	1st to 10th	Night	14% 3 20% 43% 19% 1	378
	11th to 20th	Night	14% 5% 21% 34% 24% 2	544
	21st to end	Night	19% 6% 25% 31% 17% 2	836
September	1st to 10th	Night	19% 7% 27% 33% 14% 1	760
	11th to 20th	Night	21% 6% 18% 32% 23% 1	760
	21st to end	Night	21% 10% 23% 27% 18% 1	760
October	1st to 10th	Night	25% 11% 24% 26% 13% 1	760
	11th to 20th	Night	31% 13% 24% 23% 8% 1	760
	21st to end	Night	32% 13% 26% 24% 5%	836
November	1st to 10th	Night	29% 14% 27% 23% 6% 1	780
	11th to 20th	Night	28% 17% 30% 15% 9% 1	800
	21st to end	Night	34% 18% 24% 18% 5% 1	800
December	1st to 10th	Night	32% 19% 26% 17% 5%	783
	11th to 20th	Night	31% 20% 28% 16% 5% 1	760
	21st to end	Night	37% 16% 28% 16% 3	836

Page generated at 2024-12-03 06:45:13. Version ac07

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