Val-des-Monts
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Val-des-Monts clear sky chart from 2005-11-06 to 2024-01-16.

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% 10% 4 7% 6% 3 4 4 5% 6% 31%	74757
	Night	18% 11% 4 7% 6% 3 4 4 5% 6% 32%	75040
Transparency	Day	52% 6% 11% 19% 10% 1	74462
	Night	53% 6% 11% 19% 10% 1	74869
Seeing	Day	24% 17% 30% 18% 8% 2	13338
	Night	23% 14% 28% 25% 9% 1	22548

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% 10% 8% 4 5% 3 4 4 19%	1517
	11th to 20th	Day	19% 15% 5% 10% 7% 4 4 4 3 6% 22%	1480
	21st to end	Day	14% 13% 7% 10% 6% 5% 4 5% 5% 5% 25%	1638
February	1st to 10th	Day	14% 17% 6% 12% 7% 4 5% 4 5% 6% 22%	1620
	11th to 20th	Day	13% 16% 7% 10% 7% 3 4 4 4 4 28%	1573
	21st to end	Day	19% 14% 6% 9% 7% 4 4 4 5% 4 25%	1480
March	1st to 10th	Day	15% 13% 4 9% 7% 4 4 4 5% 5% 28%	1797
	11th to 20th	Day	15% 14% 5% 7% 7% 4 5% 4 4 6% 29%	1970
	21st to end	Day	19% 9% 4 7% 5% 4 4 2 5% 5% 36%	2298
April	1st to 10th	Day	23% 12% 4 6% 6% 3 3 3 4 4 31%	2160
	11th to 20th	Day	22% 10% 5% 5% 6% 2 4 3 5% 5% 35%	2134
	21st to end	Day	23% 11% 4 7% 6% 3 4 4 4 5% 30%	2304
May	1st to 10th	Day	22% 8% 3 7% 5% 4 4 4 5% 6% 33%	2520
	11th to 20th	Day	18% 7% 3 6% 6% 3 4 4 4 7% 37%	2478
	21st to end	Day	18% 7% 3 6% 6% 4 5% 5% 5% 6% 36%	2725
June	1st to 10th	Day	23% 7% 4 6% 6% 3 5% 5% 5% 7% 29%	2520
	11th to 20th	Day	15% 6% 2 5% 6% 3 5% 5% 6% 8% 38%	2520
	21st to end	Day	21% 6% 3 5% 6% 4 5% 5% 6% 8% 31%	2520
July	1st to 10th	Day	13% 6% 3 5% 6% 4 5% 6% 7% 8% 38%	2520
	11th to 20th	Day	14% 6% 3 6% 6% 3 5% 6% 7% 10% 35%	2520
	21st to end	Day	13% 5% 3 5% 6% 3 5% 6% 7% 9% 38%	2744
August	1st to 10th	Day	13% 6% 3 6% 6% 4 5% 6% 6% 9% 36%	2489
	11th to 20th	Day	14% 6% 2 6% 6% 3 6% 6% 6% 8% 38%	2281
	21st to end	Day	14% 6% 2 5% 5% 4 5% 5% 5% 9% 40%	2376
September	1st to 10th	Day	15% 6% 2 5% 5% 3 4 5% 6% 7% 42%	2160
	11th to 20th	Day	15% 4 3 6% 5% 3 5% 4 5% 7% 43%	2160
	21st to end	Day	20% 7% 2 4 5% 2 5% 4 5% 8% 39%	1922
October	1st to 10th	Day	22% 8% 3 6% 5% 3 4 5% 5% 6% 34%	1800
	11th to 20th	Day	26% 8% 4 7% 5% 4 5% 4 5% 7% 25%	1800
	21st to end	Day	28% 11% 3 7% 6% 4 4 4 4 5% 25%	1826
November	1st to 10th	Day	15% 9% 4 7% 6% 3 4 4 5% 8% 33%	1667
	11th to 20th	Day	20% 14% 5% 8% 7% 4 5% 4 5% 6% 24%	1520
	21st to end	Day	22% 14% 5% 10% 8% 3 4 5% 4 5% 20%	1520
December	1st to 10th	Day	23% 17% 7% 9% 6% 4 5% 4 4 5% 16%	1520
	11th to 20th	Day	20% 13% 6% 11% 7% 3 4 4 4 6% 23%	1906
	21st to end	Day	25% 20% 6% 9% 6% 2 3 3 3 3 19%	2772
January	1st to 10th	Night	18% 18% 7% 11% 7% 4 5% 4 4 4 18%	2649
	11th to 20th	Night	17% 17% 8% 8% 7% 3 5% 4 4 5% 22%	2602
	21st to end	Night	12% 13% 6% 9% 8% 4 5% 4 4 6% 29%	2718
February	1st to 10th	Night	14% 14% 5% 11% 9% 4 5% 4 4 6% 23%	2340
	11th to 20th	Night	13% 13% 6% 10% 7% 4 5% 4 4 5% 29%	2272
	21st to end	Night	15% 14% 5% 8% 6% 4 4 5% 5% 5% 29%	1776
March	1st to 10th	Night	17% 11% 6% 8% 7% 4 5% 5% 4 5% 28%	2150
	11th to 20th	Night	16% 14% 4 8% 6% 4 4 3 4 6% 32%	1984
	21st to end	Night	17% 10% 3 7% 6% 2 4 3 4 5% 40%	2057
April	1st to 10th	Night	21% 11% 3 6% 5% 3 5% 4 4 6% 32%	1800
	11th to 20th	Night	18% 9% 3 6% 5% 3 4 4 5% 6% 36%	1775
	21st to end	Night	20% 10% 4 7% 4 3 4 4 4 6% 33%	1670
May	1st to 10th	Night	21% 8% 3 6% 5% 2 4 4 5% 6% 37%	1440
	11th to 20th	Night	19% 7% 4 6% 3 3 4 4 4 5% 40%	1415
	21st to end	Night	14% 6% 2 5% 5% 3 5% 5% 5% 7% 43%	1550
June	1st to 10th	Night	18% 6% 2 6% 4 3 5% 6% 7% 8% 34%	1440
	11th to 20th	Night	15% 7% 3 5% 5% 3 5% 6% 5% 6% 42%	1440
	21st to end	Night	17% 6% 2 4 6% 3 6% 4 6% 9% 35%	1440
July	1st to 10th	Night	11% 4 2 5% 5% 4 4 5% 5% 8% 46%	1440
	11th to 20th	Night	13% 5% 3 5% 4 3 4 4 6% 8% 45%	1440
	21st to end	Night	9% 5% 2 6% 5% 4 5% 5% 6% 9% 43%	1574
August	1st to 10th	Night	9% 5% 3 7% 6% 3 5% 5% 6% 8% 43%	1447
	11th to 20th	Night	11% 6% 3 5% 5% 3 4 5% 5% 8% 46%	1600
	21st to end	Night	14% 6% 2 5% 5% 3 5% 5% 5% 7% 45%	1980
September	1st to 10th	Night	12% 6% 2 5% 6% 2 5% 4 5% 7% 45%	1800
	11th to 20th	Night	16% 5% 2 4 4 3 4 4 6% 6% 47%	1800
	21st to end	Night	18% 6% 3 6% 6% 2 3 4 5% 4 44%	2034
October	1st to 10th	Night	21% 7% 3 4 5% 4 4 4 4 6% 38%	2160
	11th to 20th	Night	23% 8% 3 6% 6% 3 5% 5% 5% 6% 30%	2160
	21st to end	Night	24% 10% 4 7% 7% 3 3 4 5% 5% 28%	2528
November	1st to 10th	Night	19% 10% 4 6% 5% 4 5% 5% 5% 6% 32%	2407
	11th to 20th	Night	20% 12% 4 8% 6% 3 5% 5% 4 5% 29%	2660
	21st to end	Night	21% 14% 5% 9% 6% 3 5% 5% 4 6% 22%	2660
December	1st to 10th	Night	22% 16% 6% 9% 7% 3 4 5% 4 5% 18%	2660
	11th to 20th	Night	23% 13% 6% 10% 6% 3 4 3 3 5% 26%	3288
	21st to end	Night	26% 20% 5% 8% 6% 2 4 3 3 4 18%	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	69% 4 8% 13% 5%	1518
	11th to 20th	Day	65% 4 9% 10% 11% 1	1480
	21st to end	Day	60% 6% 8% 15% 10% 1	1638
February	1st to 10th	Day	64% 4 9% 16% 6% 2	1620
	11th to 20th	Day	59% 4 12% 14% 9% 1	1582
	21st to end	Day	62% 6% 9% 13% 10% 1	1480
March	1st to 10th	Day	58% 5% 9% 17% 10% 1	1800
	11th to 20th	Day	57% 5% 11% 12% 12% 3	1970
	21st to end	Day	51% 4 8% 18% 14% 5%	2298
April	1st to 10th	Day	58% 3 7% 17% 12% 3	2160
	11th to 20th	Day	51% 4 7% 21% 15% 2	2134
	21st to end	Day	58% 4 7% 14% 13% 4	2304
May	1st to 10th	Day	52% 5% 7% 19% 13% 3	2520
	11th to 20th	Day	48% 5% 8% 20% 16% 3	2482
	21st to end	Day	48% 7% 10% 19% 13% 2	2725
June	1st to 10th	Day	53% 8% 10% 18% 11% 1	2520
	11th to 20th	Day	43% 7% 11% 24% 12% 2	2520
	21st to end	Day	50% 8% 13% 19% 10% 1	2520
July	1st to 10th	Day	40% 8% 12% 27% 12% 1	2450
	11th to 20th	Day	41% 8% 15% 24% 11%	2445
	21st to end	Day	41% 9% 15% 25% 10%	2591
August	1st to 10th	Day	43% 9% 16% 24% 8%	2475
	11th to 20th	Day	42% 9% 15% 25% 9% 1	2281
	21st to end	Day	41% 7% 14% 26% 11% 1	2376
September	1st to 10th	Day	40% 7% 14% 28% 12%	2160
	11th to 20th	Day	39% 6% 14% 30% 10% 1	2160
	21st to end	Day	44% 6% 16% 26% 8%	1922
October	1st to 10th	Day	50% 6% 12% 21% 10% 1	1800
	11th to 20th	Day	59% 6% 15% 15% 5% 1	1800
	21st to end	Day	61% 6% 12% 15% 6%	1826
November	1st to 10th	Day	48% 7% 14% 23% 6% 1	1667
	11th to 20th	Day	61% 5% 13% 13% 7% 1	1520
	21st to end	Day	66% 7% 12% 8% 6% 1	1520
December	1st to 10th	Day	71% 5% 12% 9% 3	1520
	11th to 20th	Day	63% 7% 12% 13% 5%	1906
	21st to end	Day	71% 4 7% 14% 4	2772
January	1st to 10th	Night	70% 5% 9% 12% 4	2649
	11th to 20th	Night	66% 6% 10% 10% 8% 1	2602
	21st to end	Night	56% 5% 9% 16% 12% 1	2718
February	1st to 10th	Night	62% 5% 10% 15% 7% 1	2340
	11th to 20th	Night	59% 4 10% 19% 8% 1	2274
	21st to end	Night	56% 5% 10% 18% 11% 1	1776
March	1st to 10th	Night	58% 5% 9% 17% 9% 2	2160
	11th to 20th	Night	55% 4 10% 17% 11% 3	1985
	21st to end	Night	49% 4 7% 21% 15% 5%	2057
April	1st to 10th	Night	54% 4 10% 17% 14% 2	1800
	11th to 20th	Night	49% 5% 7% 21% 16% 2	1775
	21st to end	Night	52% 5% 9% 17% 14% 3	1670
May	1st to 10th	Night	48% 5% 8% 20% 16% 4	1440
	11th to 20th	Night	45% 5% 7% 21% 18% 3	1416
	21st to end	Night	40% 8% 13% 20% 17% 3	1551
June	1st to 10th	Night	46% 7% 13% 24% 8% 1	1440
	11th to 20th	Night	41% 8% 11% 26% 13% 2	1440
	21st to end	Night	45% 9% 13% 20% 13%	1440
July	1st to 10th	Night	35% 7% 14% 28% 16% 1	1400
	11th to 20th	Night	37% 7% 12% 31% 13%	1392
	21st to end	Night	35% 9% 16% 27% 13%	1486
August	1st to 10th	Night	36% 10% 19% 23% 11% 1	1437
	11th to 20th	Night	37% 8% 15% 30% 11%	1600
	21st to end	Night	38% 8% 16% 28% 10%	1980
September	1st to 10th	Night	38% 7% 11% 29% 14% 1	1800
	11th to 20th	Night	37% 7% 12% 33% 9% 1	1800
	21st to end	Night	43% 5% 12% 31% 9%	2034
October	1st to 10th	Night	47% 6% 9% 24% 13%	2160
	11th to 20th	Night	54% 6% 12% 19% 7% 1	2160
	21st to end	Night	58% 6% 13% 15% 7%	2528
November	1st to 10th	Night	52% 6% 15% 19% 8%	2407
	11th to 20th	Night	58% 5% 12% 15% 8% 1	2660
	21st to end	Night	62% 7% 13% 14% 4	2660
December	1st to 10th	Night	67% 6% 10% 12% 4	2660
	11th to 20th	Night	63% 4 10% 15% 7% 1	3288
	21st to end	Night	72% 4 7% 13% 4	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	28% 19% 31% 18% 3	180
	11th to 20th	Day	30% 20% 34% 12% 4 1	170
	21st to end	Day	24% 21% 34% 16% 6% 1	200
February	1st to 10th	Day	35% 27% 30% 8%	240
	11th to 20th	Day	30% 30% 34% 5% 1	240
	21st to end	Day	31% 24% 29% 13% 3	346
March	1st to 10th	Day	26% 21% 34% 14% 5%	420
	11th to 20th	Day	29% 23% 29% 15% 4 1	420
	21st to end	Day	33% 18% 27% 16% 5% 1	462
April	1st to 10th	Day	31% 22% 29% 13% 4 1	420
	11th to 20th	Day	31% 22% 24% 14% 8% 1	412
	21st to end	Day	31% 21% 31% 11% 5% 1	420
May	1st to 10th	Day	26% 19% 30% 16% 6% 2	423
	11th to 20th	Day	23% 18% 32% 18% 6% 2	447
	21st to end	Day	21% 18% 32% 20% 8% 1	485
June	1st to 10th	Day	26% 14% 35% 18% 6% 1	450
	11th to 20th	Day	17% 17% 32% 21% 10% 3	450
	21st to end	Day	21% 15% 31% 21% 10% 2	450
July	1st to 10th	Day	14% 9% 33% 30% 10% 3	445
	11th to 20th	Day	15% 12% 34% 26% 11% 3	444
	21st to end	Day	15% 7% 35% 28% 11% 2	488
August	1st to 10th	Day	15% 9% 29% 31% 13% 3	446
	11th to 20th	Day	16% 6% 28% 27% 14% 8%	439
	21st to end	Day	15% 15% 30% 23% 11% 7%	495
September	1st to 10th	Day	17% 12% 30% 22% 12% 7%	450
	11th to 20th	Day	14% 14% 26% 21% 16% 9%	450
	21st to end	Day	21% 15% 27% 20% 14% 4	450
October	1st to 10th	Day	26% 17% 23% 20% 10% 4	450
	11th to 20th	Day	28% 21% 30% 13% 7% 1	450
	21st to end	Day	33% 18% 27% 18% 4	417
November	1st to 10th	Day	25% 19% 31% 17% 7% 1	361
	11th to 20th	Day	30% 26% 30% 11% 3	180
	21st to end	Day	29% 24% 31% 11% 3 2	180
December	1st to 10th	Day	33% 16% 37% 12% 2	180
	11th to 20th	Day	29% 26% 34% 10% 1 1	180
	21st to end	Day	32% 24% 32% 10% 2 1	198
January	1st to 10th	Night	28% 17% 33% 19% 4	760
	11th to 20th	Night	29% 18% 29% 19% 6%	744
	21st to end	Night	19% 15% 36% 23% 6% 1	792
February	1st to 10th	Night	21% 21% 31% 23% 3	720
	11th to 20th	Night	21% 20% 36% 18% 4 1	703
	21st to end	Night	26% 19% 28% 23% 4 1	592
March	1st to 10th	Night	24% 17% 33% 22% 4	720
	11th to 20th	Night	24% 20% 32% 19% 5%	720
	21st to end	Night	25% 17% 28% 23% 7%	792
April	1st to 10th	Night	28% 17% 26% 24% 4	720
	11th to 20th	Night	25% 19% 27% 21% 7%	711
	21st to end	Night	27% 17% 26% 22% 7% 1	590
May	1st to 10th	Night	25% 11% 27% 27% 9% 2	360
	11th to 20th	Night	22% 10% 29% 30% 8%	354
	21st to end	Night	17% 10% 36% 27% 10% 1	389
June	1st to 10th	Night	18% 10% 30% 34% 8% 1	360
	11th to 20th	Night	16% 9% 28% 31% 14% 1	360
	21st to end	Night	19% 6% 25% 37% 13%	360
July	1st to 10th	Night	9% 5% 30% 39% 17%	350
	11th to 20th	Night	13% 4 25% 41% 17%	348
	21st to end	Night	9% 6% 26% 42% 15% 2	394
August	1st to 10th	Night	11% 5% 23% 40% 21% 1	373
	11th to 20th	Night	13% 4 20% 36% 24% 3	536
	21st to end	Night	14% 7% 26% 32% 18% 2	792
September	1st to 10th	Night	16% 7% 30% 29% 18% 1	720
	11th to 20th	Night	18% 9% 21% 31% 18% 3	720
	21st to end	Night	21% 9% 26% 25% 19% 1	720
October	1st to 10th	Night	24% 13% 25% 21% 15% 1	720
	11th to 20th	Night	27% 14% 27% 25% 6% 1	720
	21st to end	Night	29% 16% 27% 24% 5%	792
November	1st to 10th	Night	26% 15% 26% 25% 8% 1	740
	11th to 20th	Night	25% 19% 30% 16% 9% 1	760
	21st to end	Night	29% 20% 25% 21% 5%	760
December	1st to 10th	Night	30% 18% 29% 21% 3	760
	11th to 20th	Night	28% 20% 27% 19% 5% 1	760
	21st to end	Night	34% 16% 31% 16% 4	836

Page generated at 2024-01-13 09:37:56. Version ac07

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