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 2024-12-06.

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	17% 10% 4 8% 5% 4 4 4 5% 7% 31%	101828
	Night	17% 12% 4 9% 5% 4 4 3 5% 6% 31%	97877
Transparency	Day	51% 6% 12% 21% 9% 1	105311
	Night	53% 6% 12% 20% 9% 1	102483
Seeing	Day	24% 17% 31% 18% 8% 2	14519
	Night	23% 14% 28% 25% 9% 1	23627

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% 19% 7% 13% 6% 5% 4 3 4 3 20%	2517
	11th to 20th	Day	14% 14% 6% 17% 7% 5% 4 3 4 5% 20%	2520
	21st to end	Day	13% 17% 8% 13% 5% 7% 5% 4 5% 5% 18%	2868
February	1st to 10th	Day	13% 17% 5% 13% 6% 5% 4 4 5% 5% 22%	1710
	11th to 20th	Day	12% 17% 6% 12% 6% 4 4 3 4 4 27%	1663
	21st to end	Day	18% 14% 5% 9% 7% 5% 4 3 5% 4 25%	1570
March	1st to 10th	Day	19% 18% 4 8% 5% 4 3 3 4 5% 25%	3116
	11th to 20th	Day	12% 17% 6% 10% 6% 5% 5% 3 4 5% 26%	3470
	21st to end	Day	13% 9% 3 7% 7% 5% 4 3 5% 6% 39%	4032
April	1st to 10th	Day	23% 13% 4 7% 5% 4 3 2 4 5% 31%	2280
	11th to 20th	Day	22% 11% 4 6% 4 3 3 3 5% 5% 34%	2254
	21st to end	Day	22% 11% 4 8% 5% 4 4 3 4 4 30%	2433
May	1st to 10th	Day	21% 9% 3 8% 5% 4 5% 3 6% 7% 29%	4426
	11th to 20th	Day	19% 9% 3 7% 5% 4 5% 3 6% 8% 33%	4398
	21st to end	Day	18% 7% 2 7% 5% 5% 4 4 5% 7% 36%	4837
June	1st to 10th	Day	23% 8% 3 7% 5% 4 5% 4 6% 7% 29%	2660
	11th to 20th	Day	15% 6% 3 6% 5% 5% 5% 4 6% 8% 37%	2660
	21st to end	Day	21% 7% 2 6% 5% 5% 5% 4 6% 7% 31%	2660
July	1st to 10th	Day	12% 7% 3 8% 6% 5% 6% 5% 7% 9% 33%	4440
	11th to 20th	Day	15% 6% 3 7% 5% 5% 5% 4 7% 8% 37%	4440
	21st to end	Day	12% 6% 2 5% 4 4 4 4 6% 8% 45%	4814
August	1st to 10th	Day	14% 6% 3 8% 6% 5% 5% 4 6% 9% 34%	4378
	11th to 20th	Day	17% 6% 2 6% 4 4 5% 4 7% 8% 36%	3994
	21st to end	Day	13% 5% 2 6% 4 5% 5% 5% 6% 10% 39%	4180
September	1st to 10th	Day	15% 7% 2 6% 4 4 5% 3 6% 7% 42%	2280
	11th to 20th	Day	14% 5% 2 6% 5% 4 5% 3 5% 7% 45%	2279
	21st to end	Day	20% 7% 2 5% 4 3 5% 3 5% 8% 39%	2028
October	1st to 10th	Day	21% 9% 3 7% 4 4 4 4 5% 6% 33%	1900
	11th to 20th	Day	25% 9% 3 8% 4 5% 5% 3 5% 7% 27%	1900
	21st to end	Day	26% 11% 3 8% 4 4 5% 3 4 6% 26%	1927
November	1st to 10th	Day	15% 10% 3 8% 5% 5% 4 4 5% 8% 33%	1756
	11th to 20th	Day	18% 14% 4 9% 6% 5% 4 3 5% 6% 25%	1600
	21st to end	Day	22% 15% 5% 11% 6% 4 4 3 4 5% 19%	1600
December	1st to 10th	Day	21% 20% 6% 11% 5% 5% 4 3 4 5% 15%	1560
	11th to 20th	Day	20% 14% 5% 12% 6% 4 4 3 4 6% 23%	1906
	21st to end	Day	25% 21% 6% 10% 4 3 3 2 3 3 19%	2772
January	1st to 10th	Night	16% 19% 7% 11% 6% 4 4 3 4 5% 21%	4429
	11th to 20th	Night	12% 16% 7% 13% 7% 5% 4 4 4 6% 23%	4440
	21st to end	Night	15% 18% 7% 13% 6% 7% 4 3 4 4 20%	4788
February	1st to 10th	Night	13% 15% 5% 13% 7% 5% 4 4 5% 6% 23%	2470
	11th to 20th	Night	12% 14% 6% 12% 6% 5% 5% 3 4 5% 28%	2402
	21st to end	Night	15% 15% 4 9% 5% 5% 5% 4 5% 5% 29%	1884
March	1st to 10th	Night	21% 13% 4 8% 5% 4 4 3 4 4 31%	3724
	11th to 20th	Night	16% 18% 5% 10% 4 4 3 3 5% 6% 26%	3484
	21st to end	Night	14% 10% 3 9% 5% 4 3 2 4 4 41%	3599
April	1st to 10th	Night	21% 12% 2 7% 4 4 4 3 4 6% 31%	1900
	11th to 20th	Night	18% 10% 3 7% 4 4 4 3 5% 5% 36%	1875
	21st to end	Night	21% 10% 4 7% 3 3 4 3 4 6% 34%	1762
May	1st to 10th	Night	20% 10% 3 8% 5% 4 5% 3 5% 6% 30%	2514
	11th to 20th	Night	20% 8% 3 6% 4 5% 4 4 4 6% 37%	2495
	21st to end	Night	17% 7% 2 7% 4 5% 6% 4 6% 6% 38%	2738
June	1st to 10th	Night	17% 7% 2 7% 4 5% 4 6% 6% 8% 34%	1520
	11th to 20th	Night	14% 7% 3 6% 4 4 5% 5% 5% 6% 42%	1520
	21st to end	Night	18% 7% 3 5% 5% 5% 5% 3 6% 8% 35%	1520
July	1st to 10th	Night	13% 7% 3 8% 6% 5% 5% 4 6% 8% 36%	2520
	11th to 20th	Night	15% 6% 2 6% 4 4 4 3 6% 8% 42%	2520
	21st to end	Night	10% 6% 2 6% 4 5% 5% 4 6% 8% 45%	2739
August	1st to 10th	Night	12% 6% 3 8% 5% 4 5% 4 6% 7% 39%	2535
	11th to 20th	Night	15% 7% 3 6% 4 4 4 3 5% 6% 42%	2801
	21st to end	Night	16% 6% 2 6% 5% 4 4 4 5% 7% 42%	3476
September	1st to 10th	Night	12% 6% 2 6% 5% 3 4 4 5% 7% 46%	1900
	11th to 20th	Night	15% 5% 1 5% 3 4 4 3 6% 6% 48%	1900
	21st to end	Night	18% 6% 3 6% 5% 3 3 3 4 4 45%	2147
October	1st to 10th	Night	20% 8% 3 5% 4 4 4 3 5% 6% 39%	2280
	11th to 20th	Night	22% 8% 3 8% 5% 5% 4 4 5% 6% 31%	2280
	21st to end	Night	23% 11% 4 8% 5% 4 3 3 5% 5% 28%	2669
November	1st to 10th	Night	19% 11% 3 6% 5% 5% 5% 4 5% 6% 32%	2537
	11th to 20th	Night	19% 12% 4 9% 5% 4 5% 4 4 5% 29%	2800
	21st to end	Night	20% 15% 4 10% 5% 4 5% 4 5% 6% 22%	2800
December	1st to 10th	Night	21% 18% 5% 10% 6% 5% 4 4 5% 5% 18%	2737
	11th to 20th	Night	22% 14% 5% 11% 5% 4 3 2 3 5% 26%	3288
	21st to end	Night	26% 20% 5% 10% 4 3 3 3 4 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	68% 6% 10% 11% 5%	2518
	11th to 20th	Day	66% 5% 10% 12% 6%	2520
	21st to end	Day	68% 7% 8% 10% 6%	2868
February	1st to 10th	Day	63% 4 9% 17% 5% 2	1710
	11th to 20th	Day	60% 4 12% 14% 9% 1	1672
	21st to end	Day	60% 6% 9% 13% 10% 1	1570
March	1st to 10th	Day	61% 5% 8% 16% 10% 1	3119
	11th to 20th	Day	60% 5% 11% 13% 9% 2	3470
	21st to end	Day	45% 4 8% 23% 17% 3	4032
April	1st to 10th	Day	57% 4 7% 18% 12% 3	2280
	11th to 20th	Day	52% 4 7% 20% 14% 2	2254
	21st to end	Day	58% 4 7% 15% 12% 4	2433
May	1st to 10th	Day	52% 7% 9% 21% 9% 2	4440
	11th to 20th	Day	48% 8% 13% 19% 9% 2	4402
	21st to end	Day	47% 6% 11% 20% 14% 2	4837
June	1st to 10th	Day	53% 7% 10% 19% 11% 1	2660
	11th to 20th	Day	43% 7% 11% 24% 12% 2	2660
	21st to end	Day	50% 8% 13% 19% 9% 1	2660
July	1st to 10th	Day	44% 7% 14% 25% 9%	4370
	11th to 20th	Day	42% 7% 15% 28% 8%	4365
	21st to end	Day	36% 6% 14% 33% 11%	4661
August	1st to 10th	Day	46% 7% 16% 23% 8%	4364
	11th to 20th	Day	42% 8% 14% 28% 7%	4033
	21st to end	Day	40% 6% 17% 25% 12% 1	4180
September	1st to 10th	Day	40% 6% 14% 28% 11%	2280
	11th to 20th	Day	37% 6% 14% 31% 11% 1	2279
	21st to end	Day	44% 6% 16% 26% 9%	2028
October	1st to 10th	Day	50% 5% 11% 27% 6%	3160
	11th to 20th	Day	49% 6% 13% 22% 9%	3140
	21st to end	Day	52% 6% 19% 17% 6%	3152
November	1st to 10th	Day	49% 7% 14% 23% 6% 1	1756
	11th to 20th	Day	60% 5% 13% 14% 8% 1	1600
	21st to end	Day	66% 7% 12% 8% 6% 1	1600
December	1st to 10th	Day	71% 4 12% 9% 3	1560
	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	65% 6% 14% 11% 3	4429
	11th to 20th	Night	62% 7% 14% 12% 5%	4440
	21st to end	Night	69% 5% 9% 10% 7%	4788
February	1st to 10th	Night	61% 5% 10% 16% 7% 1	2470
	11th to 20th	Night	59% 4 9% 19% 8% 1	2404
	21st to end	Night	56% 5% 10% 18% 11% 1	1884
March	1st to 10th	Night	57% 5% 9% 17% 9% 2	3734
	11th to 20th	Night	60% 6% 11% 14% 8% 1	3485
	21st to end	Night	46% 4 8% 22% 16% 4	3599
April	1st to 10th	Night	54% 4 10% 17% 13% 2	1900
	11th to 20th	Night	50% 5% 7% 21% 15% 2	1875
	21st to end	Night	51% 5% 9% 18% 14% 3	1762
May	1st to 10th	Night	52% 7% 9% 20% 9% 2	2520
	11th to 20th	Night	47% 8% 11% 21% 12% 2	2496
	21st to end	Night	45% 7% 10% 19% 16% 2	2739
June	1st to 10th	Night	46% 7% 13% 24% 9% 1	1520
	11th to 20th	Night	40% 8% 11% 26% 13% 2	1520
	21st to end	Night	47% 8% 12% 20% 13%	1520
July	1st to 10th	Night	45% 6% 16% 20% 12% 1	2480
	11th to 20th	Night	40% 7% 14% 30% 8%	2472
	21st to end	Night	35% 7% 15% 30% 13%	2651
August	1st to 10th	Night	43% 7% 15% 25% 9%	2525
	11th to 20th	Night	42% 6% 15% 30% 7%	2828
	21st to end	Night	41% 6% 15% 25% 12% 2	3476
September	1st to 10th	Night	37% 7% 11% 30% 14% 1	1900
	11th to 20th	Night	36% 7% 12% 33% 10% 1	1900
	21st to end	Night	43% 4 12% 30% 11%	2147
October	1st to 10th	Night	41% 6% 12% 28% 12%	3800
	11th to 20th	Night	45% 7% 15% 24% 9%	3779
	21st to end	Night	50% 6% 18% 17% 9%	4394
November	1st to 10th	Night	52% 6% 15% 19% 8%	2537
	11th to 20th	Night	57% 5% 12% 15% 9% 1	2800
	21st to end	Night	63% 7% 13% 14% 4	2800
December	1st to 10th	Night	67% 6% 10% 12% 4	2737
	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	29% 18% 37% 11% 3 1	180
	21st to end	Day	23% 20% 35% 18% 5%	225
February	1st to 10th	Day	32% 27% 31% 9% 1	270
	11th to 20th	Day	28% 31% 35% 6% 1	270
	21st to end	Day	32% 24% 29% 13% 2	382
March	1st to 10th	Day	26% 21% 33% 14% 6%	460
	11th to 20th	Day	28% 23% 30% 14% 3 1	460
	21st to end	Day	32% 20% 28% 15% 4 1	506
April	1st to 10th	Day	31% 22% 28% 13% 4 1	460
	11th to 20th	Day	33% 23% 24% 12% 8% 1	452
	21st to end	Day	31% 22% 30% 11% 5% 1	460
May	1st to 10th	Day	25% 19% 31% 16% 6% 2	463
	11th to 20th	Day	21% 18% 32% 19% 7% 2	487
	21st to end	Day	22% 17% 32% 21% 8% 1	529
June	1st to 10th	Day	26% 13% 33% 20% 7% 1	490
	11th to 20th	Day	16% 18% 33% 21% 10% 3	490
	21st to end	Day	24% 14% 31% 20% 9% 2	490
July	1st to 10th	Day	14% 10% 34% 29% 10% 3	485
	11th to 20th	Day	15% 13% 34% 25% 11% 3	484
	21st to end	Day	15% 8% 35% 29% 11% 3	532
August	1st to 10th	Day	15% 9% 30% 30% 12% 3	486
	11th to 20th	Day	17% 7% 29% 26% 14% 8%	479
	21st to end	Day	15% 14% 30% 24% 11% 6%	539
September	1st to 10th	Day	18% 12% 31% 22% 11% 7%	490
	11th to 20th	Day	13% 13% 24% 22% 18% 10%	490
	21st to end	Day	21% 14% 27% 20% 13% 4	490
October	1st to 10th	Day	26% 17% 23% 21% 10% 3	490
	11th to 20th	Day	27% 22% 30% 13% 7% 1	490
	21st to end	Day	32% 18% 29% 18% 4	452
November	1st to 10th	Day	27% 20% 30% 16% 7% 1	390
	11th to 20th	Day	28% 26% 32% 12% 4	200
	21st to end	Day	31% 26% 30% 10% 3 2	200
December	1st to 10th	Day	33% 15% 36% 14% 3	190
	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	28% 18% 29% 19% 6%	760
	21st to end	Night	19% 15% 36% 24% 6% 1	836
February	1st to 10th	Night	21% 21% 31% 24% 3	760
	11th to 20th	Night	21% 22% 35% 18% 3 1	743
	21st to end	Night	26% 18% 29% 23% 4	628
March	1st to 10th	Night	25% 17% 33% 22% 4	760
	11th to 20th	Night	24% 21% 31% 19% 5%	760
	21st to end	Night	24% 18% 28% 22% 7%	836
April	1st to 10th	Night	28% 17% 26% 24% 4	760
	11th to 20th	Night	26% 20% 27% 21% 7%	751
	21st to end	Night	27% 16% 27% 22% 7%	622
May	1st to 10th	Night	24% 11% 28% 27% 8% 2	380
	11th to 20th	Night	22% 10% 28% 31% 9%	374
	21st to end	Night	17% 10% 37% 27% 9%	411
June	1st to 10th	Night	18% 10% 29% 34% 8% 1	380
	11th to 20th	Night	16% 9% 28% 32% 14% 1	380
	21st to end	Night	21% 6% 25% 36% 12%	380
July	1st to 10th	Night	9% 6% 30% 39% 16%	370
	11th to 20th	Night	13% 4 25% 41% 17%	368
	21st to end	Night	9% 6% 25% 43% 15% 1	416
August	1st to 10th	Night	11% 4 23% 40% 21% 1	394
	11th to 20th	Night	13% 5% 20% 35% 24% 3	567
	21st to end	Night	14% 7% 26% 32% 19% 2	836
September	1st to 10th	Night	16% 7% 30% 29% 18% 1	760
	11th to 20th	Night	17% 8% 20% 30% 22% 3	760
	21st to end	Night	21% 8% 26% 25% 18% 1	760
October	1st to 10th	Night	23% 13% 26% 21% 15% 1	760
	11th to 20th	Night	26% 14% 27% 25% 7% 1	760
	21st to end	Night	28% 16% 28% 24% 5%	836
November	1st to 10th	Night	26% 16% 25% 24% 7% 1	780
	11th to 20th	Night	26% 19% 31% 16% 9% 1	800
	21st to end	Night	29% 21% 24% 21% 5%	800
December	1st to 10th	Night	29% 18% 29% 21% 3	783
	11th to 20th	Night	28% 20% 27% 19% 5% 1	760
	21st to end	Night	34% 16% 31% 16% 4	836

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

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