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 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	16% 11% 4 9% 5% 5% 4 4 5% 7% 30%	131390
	Night	16% 12% 4 10% 5% 5% 4 4 5% 6% 30%	130088
Transparency	Day	53% 6% 11% 20% 9% 1	134855
	Night	54% 5% 11% 19% 10% 1	134710
Seeing	Day	24% 18% 31% 18% 7% 2	16057
	Night	23% 14% 28% 25% 9% 1	25272

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% 17% 6% 15% 8% 6% 4 3 5% 4 19%	4661
	11th to 20th	Day	10% 20% 9% 17% 8% 4 4 3 4 5% 17%	4650
	21st to end	Day	8% 13% 7% 17% 9% 8% 5% 4 4 5% 20%	5304
February	1st to 10th	Day	13% 16% 5% 13% 7% 5% 4 4 5% 5% 23%	1890
	11th to 20th	Day	12% 17% 5% 13% 7% 5% 4 3 5% 5% 26%	1844
	21st to end	Day	17% 15% 5% 10% 7% 5% 4 3 5% 4 24%	1730
March	1st to 10th	Day	18% 16% 4 11% 6% 4 4 3 5% 5% 23%	4576
	11th to 20th	Day	12% 14% 5% 10% 6% 5% 5% 4 5% 7% 28%	5046
	21st to end	Day	17% 12% 4 8% 6% 4 3 3 4 5% 35%	5780
April	1st to 10th	Day	22% 13% 4 7% 5% 4 3 2 4 5% 31%	2400
	11th to 20th	Day	22% 11% 4 6% 4 3 3 3 5% 5% 34%	2374
	21st to end	Day	22% 11% 4 8% 5% 4 4 3 4 5% 31%	2562
May	1st to 10th	Day	22% 10% 4 9% 5% 5% 5% 3 6% 6% 25%	6346
	11th to 20th	Day	17% 9% 3 8% 5% 5% 5% 3 5% 7% 31%	6318
	21st to end	Day	22% 9% 3 7% 5% 4 4 4 5% 6% 32%	6949
June	1st to 10th	Day	22% 8% 3 7% 5% 4 5% 4 6% 7% 29%	2800
	11th to 20th	Day	14% 6% 2 6% 5% 5% 5% 4 6% 8% 38%	2800
	21st to end	Day	20% 7% 2 6% 5% 5% 5% 4 6% 8% 31%	2800
July	1st to 10th	Day	14% 6% 3 8% 6% 6% 6% 5% 7% 9% 32%	6360
	11th to 20th	Day	12% 5% 2 7% 4 4 5% 4 7% 8% 41%	6360
	21st to end	Day	10% 5% 2 5% 4 3 4 4 6% 10% 46%	6926
August	1st to 10th	Day	14% 6% 3 8% 5% 5% 5% 4 6% 9% 35%	4517
	11th to 20th	Day	17% 6% 2 6% 4 4 5% 4 7% 8% 37%	4123
	21st to end	Day	13% 6% 2 6% 4 5% 5% 4 6% 10% 39%	4312
September	1st to 10th	Day	14% 6% 2 6% 4 4 5% 4 6% 7% 42%	2400
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 3 5% 7% 46%	2399
	21st to end	Day	20% 7% 2 4 4 4 5% 3 5% 8% 39%	2135
October	1st to 10th	Day	20% 8% 3 6% 4 4 4 4 5% 6% 36%	2000
	11th to 20th	Day	24% 9% 3 8% 4 5% 5% 3 5% 7% 27%	2000
	21st to end	Day	25% 12% 3 8% 4 4 5% 3 4 6% 26%	2028
November	1st to 10th	Day	15% 11% 4 8% 5% 4 4 4 5% 8% 31%	1846
	11th to 20th	Day	18% 15% 5% 9% 6% 5% 5% 4 5% 6% 24%	1680
	21st to end	Day	22% 16% 5% 11% 6% 4 4 3 4 5% 19%	1680
December	1st to 10th	Day	19% 22% 7% 11% 5% 4 5% 4 5% 5% 13%	2680
	11th to 20th	Day	17% 15% 7% 13% 6% 4 4 3 4 4 23%	3066
	21st to end	Day	21% 19% 5% 10% 5% 4 5% 3 4 4 20%	4048
January	1st to 10th	Night	12% 20% 8% 14% 6% 4 5% 3 5% 5% 19%	8234
	11th to 20th	Night	10% 19% 8% 16% 8% 5% 5% 3 4 5% 18%	8235
	21st to end	Night	9% 15% 6% 14% 8% 8% 6% 4 5% 6% 20%	8877
February	1st to 10th	Night	12% 15% 5% 13% 7% 6% 4 4 5% 6% 24%	2730
	11th to 20th	Night	12% 14% 6% 12% 6% 5% 5% 3 4 5% 28%	2661
	21st to end	Night	14% 15% 5% 10% 5% 5% 4 4 5% 5% 28%	2076
March	1st to 10th	Night	21% 15% 5% 10% 5% 4 4 3 4 4 27%	5484
	11th to 20th	Night	12% 14% 4 9% 5% 5% 5% 4 6% 8% 28%	5062
	21st to end	Night	17% 11% 4 9% 6% 4 4 3 5% 4 33%	5151
April	1st to 10th	Night	21% 12% 2 8% 4 4 4 3 4 6% 31%	2000
	11th to 20th	Night	18% 10% 3 7% 4 4 4 3 5% 5% 35%	1975
	21st to end	Night	21% 10% 4 7% 3 4 4 3 4 6% 34%	1854
May	1st to 10th	Night	20% 11% 4 9% 5% 5% 5% 4 6% 7% 25%	3594
	11th to 20th	Night	16% 8% 3 7% 4 5% 5% 4 4 6% 38%	3575
	21st to end	Night	20% 9% 3 8% 5% 5% 5% 4 5% 5% 32%	3926
June	1st to 10th	Night	17% 7% 2 7% 4 5% 4 6% 6% 8% 34%	1600
	11th to 20th	Night	14% 7% 3 6% 4 4 5% 5% 5% 6% 42%	1600
	21st to end	Night	18% 7% 3 5% 5% 5% 5% 3 6% 8% 35%	1600
July	1st to 10th	Night	14% 7% 3 7% 5% 5% 5% 5% 6% 9% 34%	3600
	11th to 20th	Night	13% 6% 2 7% 4 4 4 3 6% 7% 44%	3600
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 6% 8% 48%	3926
August	1st to 10th	Night	11% 6% 3 8% 5% 4 5% 4 6% 7% 39%	2616
	11th to 20th	Night	15% 7% 3 6% 4 4 4 3 5% 6% 43%	2891
	21st to end	Night	16% 6% 2 6% 4 4 5% 4 5% 7% 42%	3586
September	1st to 10th	Night	12% 6% 2 6% 5% 3 4 4 5% 7% 47%	2000
	11th to 20th	Night	15% 5% 1 5% 3 4 4 3 6% 6% 49%	2000
	21st to end	Night	17% 7% 3 6% 5% 3 3 3 4 4 45%	2260
October	1st to 10th	Night	19% 7% 3 5% 4 4 4 3 5% 6% 41%	2400
	11th to 20th	Night	21% 8% 3 7% 5% 5% 4 4 5% 6% 32%	2400
	21st to end	Night	22% 11% 4 8% 5% 4 3 3 5% 5% 29%	2810
November	1st to 10th	Night	19% 12% 3 6% 5% 5% 5% 4 5% 6% 31%	2667
	11th to 20th	Night	19% 12% 4 9% 5% 4 5% 4 5% 5% 29%	2940
	21st to end	Night	19% 15% 5% 10% 6% 4 5% 4 4 6% 21%	2940
December	1st to 10th	Night	17% 17% 6% 12% 6% 5% 5% 4 5% 5% 16%	4720
	11th to 20th	Night	22% 13% 5% 12% 6% 4 3 2 3 5% 25%	5348
	21st to end	Night	22% 21% 4 9% 5% 4 3 3 4 5% 21%	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	67% 5% 8% 15% 5%	4662
	11th to 20th	Day	70% 4 6% 10% 10%	4680
	21st to end	Day	66% 6% 8% 11% 9% 1	5304
February	1st to 10th	Day	62% 4 9% 17% 6% 1	1890
	11th to 20th	Day	61% 4 11% 15% 9% 1	1853
	21st to end	Day	62% 5% 9% 13% 10% 1	1730
March	1st to 10th	Day	63% 5% 7% 12% 11% 3	4579
	11th to 20th	Day	55% 5% 15% 14% 10% 1	5046
	21st to end	Day	53% 3 6% 18% 17% 2	5780
April	1st to 10th	Day	57% 4 7% 17% 13% 3	2400
	11th to 20th	Day	52% 4 7% 20% 15% 2	2374
	21st to end	Day	57% 4 7% 15% 13% 4	2562
May	1st to 10th	Day	57% 6% 8% 19% 8% 2	6357
	11th to 20th	Day	50% 7% 13% 18% 10% 1	6322
	21st to end	Day	53% 5% 10% 19% 12% 1	6949
June	1st to 10th	Day	52% 7% 10% 19% 11% 1	2800
	11th to 20th	Day	43% 7% 11% 25% 12% 2	2800
	21st to end	Day	49% 7% 13% 20% 10% 1	2800
July	1st to 10th	Day	46% 7% 13% 26% 8%	6290
	11th to 20th	Day	38% 7% 14% 31% 10%	6285
	21st to end	Day	33% 6% 16% 35% 10%	6728
August	1st to 10th	Day	45% 6% 17% 24% 8%	4503
	11th to 20th	Day	42% 8% 14% 28% 7% 1	4162
	21st to end	Day	40% 6% 17% 25% 11% 1	4312
September	1st to 10th	Day	39% 7% 14% 29% 11%	2400
	11th to 20th	Day	36% 6% 14% 32% 11% 1	2399
	21st to end	Day	44% 6% 15% 25% 10%	2135
October	1st to 10th	Day	49% 5% 11% 27% 7%	3260
	11th to 20th	Day	48% 7% 13% 22% 9% 1	3240
	21st to end	Day	52% 6% 19% 18% 6%	3253
November	1st to 10th	Day	50% 7% 13% 22% 6% 1	1846
	11th to 20th	Day	61% 5% 13% 14% 7% 1	1680
	21st to end	Day	67% 7% 12% 8% 6% 1	1680
December	1st to 10th	Day	72% 5% 11% 9% 2	2680
	11th to 20th	Day	65% 5% 9% 14% 7%	3066
	21st to end	Day	67% 5% 7% 15% 5%	4048
January	1st to 10th	Night	68% 5% 10% 12% 4	8234
	11th to 20th	Night	69% 5% 9% 11% 6%	8280
	21st to end	Night	64% 5% 7% 12% 12%	8877
February	1st to 10th	Night	60% 5% 10% 17% 8% 1	2730
	11th to 20th	Night	60% 4 9% 20% 8% 1	2663
	21st to end	Night	57% 5% 10% 18% 10% 1	2076
March	1st to 10th	Night	61% 4 7% 14% 11% 3	5494
	11th to 20th	Night	54% 7% 14% 15% 7% 3	5063
	21st to end	Night	53% 4 7% 21% 12% 3	5151
April	1st to 10th	Night	55% 4 10% 17% 13% 2	2000
	11th to 20th	Night	50% 6% 7% 21% 15% 1	1975
	21st to end	Night	51% 5% 9% 18% 14% 3	1854
May	1st to 10th	Night	56% 7% 8% 19% 8% 2	3600
	11th to 20th	Night	46% 7% 12% 20% 13% 2	3576
	21st to end	Night	53% 6% 10% 17% 13% 1	3927
June	1st to 10th	Night	46% 7% 13% 24% 10% 1	1600
	11th to 20th	Night	40% 8% 11% 26% 13% 2	1600
	21st to end	Night	47% 8% 12% 20% 13% 1	1600
July	1st to 10th	Night	45% 6% 17% 22% 9%	3560
	11th to 20th	Night	38% 6% 14% 32% 10%	3552
	21st to end	Night	33% 6% 13% 34% 13%	3809
August	1st to 10th	Night	42% 7% 16% 26% 9%	2606
	11th to 20th	Night	41% 6% 14% 30% 8%	2918
	21st to end	Night	41% 6% 15% 25% 12% 2	3586
September	1st to 10th	Night	36% 7% 12% 30% 14% 1	2000
	11th to 20th	Night	35% 7% 12% 34% 10% 1	2000
	21st to end	Night	43% 4 12% 30% 12%	2260
October	1st to 10th	Night	40% 6% 13% 29% 13%	3920
	11th to 20th	Night	45% 7% 15% 24% 9%	3899
	21st to end	Night	49% 6% 18% 18% 9%	4535
November	1st to 10th	Night	53% 6% 15% 19% 8%	2667
	11th to 20th	Night	57% 5% 12% 16% 9% 1	2940
	21st to end	Night	63% 7% 13% 14% 4	2940
December	1st to 10th	Night	67% 7% 12% 12% 3	4720
	11th to 20th	Night	64% 4 7% 14% 11% 1	5348
	21st to end	Night	68% 3 6% 13% 10%	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	27% 19% 35% 16% 4	220
	11th to 20th	Day	30% 20% 37% 10% 3 1	220
	21st to end	Day	21% 21% 36% 18% 4	275
February	1st to 10th	Day	31% 25% 32% 11% 1	330
	11th to 20th	Day	28% 30% 36% 6% 1	331
	21st to end	Day	30% 24% 31% 13% 2	446
March	1st to 10th	Day	27% 23% 33% 13% 5%	540
	11th to 20th	Day	32% 22% 29% 13% 3 1	528
	21st to end	Day	33% 20% 28% 15% 4 1	550
April	1st to 10th	Day	34% 22% 26% 13% 4 1	500
	11th to 20th	Day	33% 24% 23% 12% 8% 1	492
	21st to end	Day	31% 22% 31% 10% 5% 1	500
May	1st to 10th	Day	26% 20% 30% 15% 6% 2	503
	11th to 20th	Day	22% 18% 33% 18% 7% 2	527
	21st to end	Day	23% 16% 31% 21% 7% 1	573
June	1st to 10th	Day	27% 14% 33% 19% 7% 1	530
	11th to 20th	Day	16% 17% 35% 20% 9% 2	530
	21st to end	Day	23% 16% 32% 19% 8% 2	530
July	1st to 10th	Day	15% 10% 35% 28% 10% 3	525
	11th to 20th	Day	15% 13% 35% 25% 10% 2	524
	21st to end	Day	14% 10% 35% 27% 11% 2	576
August	1st to 10th	Day	14% 9% 30% 32% 12% 3	526
	11th to 20th	Day	17% 7% 29% 25% 14% 7%	519
	21st to end	Day	15% 14% 30% 23% 11% 6%	583
September	1st to 10th	Day	18% 12% 31% 21% 11% 7%	530
	11th to 20th	Day	12% 12% 25% 22% 19% 10%	530
	21st to end	Day	22% 14% 28% 20% 13% 4	530
October	1st to 10th	Day	25% 17% 24% 21% 10% 3	530
	11th to 20th	Day	27% 21% 32% 13% 6% 1	530
	21st to end	Day	31% 18% 29% 18% 3	487
November	1st to 10th	Day	27% 21% 30% 15% 6%	420
	11th to 20th	Day	28% 24% 32% 12% 4	220
	21st to end	Day	32% 27% 29% 9% 3 1	220
December	1st to 10th	Day	32% 16% 37% 13% 2	220
	11th to 20th	Day	30% 24% 36% 9% 1	220
	21st to end	Day	32% 22% 32% 11% 2 1	242
January	1st to 10th	Night	27% 16% 35% 19% 3	840
	11th to 20th	Night	29% 18% 28% 19% 5%	840
	21st to end	Night	19% 16% 36% 23% 6% 1	924
February	1st to 10th	Night	20% 22% 31% 24% 4	840
	11th to 20th	Night	21% 22% 35% 19% 3	823
	21st to end	Night	26% 18% 30% 23% 4	692
March	1st to 10th	Night	25% 17% 33% 21% 4	840
	11th to 20th	Night	25% 21% 31% 19% 5%	829
	21st to end	Night	26% 18% 28% 22% 7%	880
April	1st to 10th	Night	29% 17% 26% 24% 4	800
	11th to 20th	Night	26% 19% 27% 21% 7%	791
	21st to end	Night	28% 16% 27% 21% 7%	654
May	1st to 10th	Night	26% 11% 28% 27% 8% 2	400
	11th to 20th	Night	21% 11% 29% 30% 9%	394
	21st to end	Night	18% 10% 36% 26% 10%	433
June	1st to 10th	Night	17% 10% 30% 35% 8% 1	400
	11th to 20th	Night	16% 10% 28% 32% 14% 1	400
	21st to end	Night	20% 7% 25% 36% 12%	400
July	1st to 10th	Night	9% 6% 30% 39% 16%	390
	11th to 20th	Night	14% 4 24% 42% 16%	388
	21st to end	Night	9% 7% 26% 43% 14% 1	438
August	1st to 10th	Night	11% 4 23% 41% 20% 1	415
	11th to 20th	Night	13% 5% 20% 35% 24% 3	597
	21st to end	Night	15% 7% 25% 32% 19% 2	880
September	1st to 10th	Night	15% 7% 30% 29% 18% 1	800
	11th to 20th	Night	16% 8% 21% 30% 22% 3	800
	21st to end	Night	21% 8% 26% 25% 18% 1	800
October	1st to 10th	Night	23% 13% 26% 22% 16% 1	800
	11th to 20th	Night	26% 14% 28% 24% 7% 1	800
	21st to end	Night	28% 15% 28% 25% 5%	880
November	1st to 10th	Night	27% 15% 26% 24% 7% 1	820
	11th to 20th	Night	26% 19% 30% 16% 9% 1	840
	21st to end	Night	29% 21% 24% 21% 5%	840
December	1st to 10th	Night	29% 18% 29% 21% 3	840
	11th to 20th	Night	29% 20% 28% 18% 4 1	840
	21st to end	Night	34% 16% 30% 17% 4	924

Page generated at 2026-03-15 02:23:50. Version ac07

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