Parc du Mont Ste-Anne
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Parc du Mont Ste-Anne clear sky chart from 2005-11-06 to 2025-09-19.

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% 10% 3 8% 5% 5% 5% 4 6% 7% 31%	126152
	Night	15% 11% 4 9% 5% 5% 5% 4 5% 6% 32%	122952
Transparency	Day	51% 6% 13% 19% 10% 1	129593
	Night	52% 5% 12% 20% 10% 1	127599
Seeing	Day	24% 18% 31% 19% 7% 1	16494
	Night	22% 14% 29% 27% 8% 1	24809

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% 20% 5% 11% 6% 4 4 3 5% 6% 25%	3597
	11th to 20th	Day	8% 12% 5% 16% 6% 6% 5% 4 5% 5% 25%	3570
	21st to end	Day	6% 5% 4 11% 6% 5% 6% 5% 6% 7% 40%	3960
February	1st to 10th	Day	7% 13% 5% 12% 7% 6% 5% 5% 6% 6% 27%	1609
	11th to 20th	Day	11% 13% 5% 13% 8% 5% 5% 4 4 6% 27%	1909
	21st to end	Day	11% 13% 4 11% 7% 5% 5% 3 5% 7% 28%	1650
March	1st to 10th	Day	19% 14% 3 10% 7% 5% 4 3 4 4 26%	4476
	11th to 20th	Day	12% 15% 4 9% 5% 5% 5% 5% 6% 6% 29%	4786
	21st to end	Day	15% 15% 5% 9% 5% 4 4 3 4 4 33%	5776
April	1st to 10th	Day	19% 12% 4 10% 6% 4 4 3 5% 5% 29%	2400
	11th to 20th	Day	18% 8% 4 7% 4 5% 6% 3 5% 5% 35%	2490
	21st to end	Day	23% 9% 3 7% 5% 5% 4 3 5% 6% 31%	2600
May	1st to 10th	Day	24% 10% 3 7% 4 4 4 3 5% 6% 31%	6014
	11th to 20th	Day	20% 7% 2 7% 6% 5% 5% 4 5% 7% 31%	6318
	21st to end	Day	18% 10% 3 8% 5% 5% 5% 4 6% 7% 28%	7174
June	1st to 10th	Day	19% 7% 3 7% 5% 6% 6% 5% 6% 8% 27%	3000
	11th to 20th	Day	19% 8% 2 6% 5% 5% 5% 4 6% 8% 32%	3000
	21st to end	Day	22% 8% 4 8% 5% 5% 5% 4 6% 7% 26%	3000
July	1st to 10th	Day	16% 7% 3 8% 6% 6% 6% 5% 7% 9% 27%	6601
	11th to 20th	Day	15% 6% 2 7% 5% 5% 5% 5% 8% 9% 32%	6360
	21st to end	Day	11% 5% 2 6% 4 5% 6% 6% 7% 9% 39%	6926
August	1st to 10th	Day	13% 5% 2 7% 5% 6% 8% 5% 9% 9% 31%	4518
	11th to 20th	Day	18% 7% 3 7% 6% 6% 6% 5% 7% 9% 27%	4175
	21st to end	Day	17% 7% 2 6% 4 5% 5% 4 6% 7% 36%	4519
September	1st to 10th	Day	16% 7% 2 6% 5% 5% 4 4 6% 9% 36%	2400
	11th to 20th	Day	16% 6% 2 6% 3 4 4 3 5% 7% 45%	2188
	21st to end	Day	21% 8% 2 7% 4 3 4 3 5% 6% 37%	2090
October	1st to 10th	Day	18% 9% 2 8% 5% 5% 4 4 5% 6% 34%	2090
	11th to 20th	Day	21% 10% 3 9% 5% 7% 5% 3 5% 5% 27%	1733
	21st to end	Day	25% 11% 3 8% 5% 4 4 3 4 7% 26%	1881
November	1st to 10th	Day	15% 12% 4 8% 4 5% 5% 4 5% 7% 31%	1761
	11th to 20th	Day	19% 11% 4 9% 7% 5% 5% 4 4 5% 28%	1783
	21st to end	Day	17% 18% 5% 8% 5% 3 4 4 5% 5% 24%	1410
December	1st to 10th	Day	16% 13% 6% 11% 5% 5% 5% 3 5% 7% 24%	2280
	11th to 20th	Day	16% 10% 5% 11% 6% 6% 4 3 5% 4 28%	2618
	21st to end	Day	15% 12% 4 11% 6% 4 4 4 5% 6% 29%	3490
January	1st to 10th	Night	11% 19% 6% 13% 6% 6% 5% 4 4 4 22%	6349
	11th to 20th	Night	7% 15% 7% 17% 8% 6% 6% 4 5% 5% 20%	6315
	21st to end	Night	4 8% 5% 11% 6% 7% 7% 4 6% 7% 34%	6996
February	1st to 10th	Night	8% 11% 4 11% 7% 5% 5% 4 6% 7% 32%	2790
	11th to 20th	Night	9% 15% 6% 12% 5% 5% 4 4 5% 6% 28%	2373
	21st to end	Night	11% 13% 4 10% 8% 5% 5% 4 5% 7% 29%	1980
March	1st to 10th	Night	18% 13% 5% 11% 6% 4 5% 3 4 5% 26%	5364
	11th to 20th	Night	12% 15% 5% 9% 6% 6% 6% 4 5% 6% 26%	5173
	21st to end	Night	15% 15% 5% 9% 5% 4 4 3 4 5% 31%	5155
April	1st to 10th	Night	19% 14% 4 7% 4 4 4 3 5% 5% 30%	2000
	11th to 20th	Night	17% 9% 2 5% 4 5% 5% 4 6% 7% 35%	1857
	21st to end	Night	23% 8% 3 7% 5% 4 4 3 5% 5% 35%	1800
May	1st to 10th	Night	23% 9% 3 7% 4 4 4 4 4 6% 33%	3970
	11th to 20th	Night	27% 7% 2 6% 4 4 4 3 5% 6% 32%	3575
	21st to end	Night	17% 7% 2 5% 5% 5% 5% 4 6% 7% 36%	3709
June	1st to 10th	Night	18% 9% 3 8% 6% 5% 6% 4 7% 8% 29%	1400
	11th to 20th	Night	18% 6% 2 6% 4 4 5% 3 7% 6% 39%	1400
	21st to end	Night	24% 8% 3 6% 5% 4 4 3 4 7% 32%	1400
July	1st to 10th	Night	12% 6% 3 7% 5% 5% 6% 6% 8% 9% 33%	3352
	11th to 20th	Night	19% 5% 2 6% 4 4 4 4 6% 8% 38%	3600
	21st to end	Night	11% 4 2 5% 4 4 5% 4 6% 8% 46%	3926
August	1st to 10th	Night	16% 6% 2 7% 4 4 5% 3 5% 7% 39%	2586
	11th to 20th	Night	17% 6% 3 7% 5% 5% 5% 4 6% 7% 35%	2872
	21st to end	Night	14% 7% 3 7% 5% 5% 5% 3 5% 7% 38%	3377
September	1st to 10th	Night	15% 6% 2 6% 4 4 4 3 5% 7% 43%	2000
	11th to 20th	Night	17% 5% 2 5% 4 3 4 3 5% 7% 45%	2169
	21st to end	Night	18% 7% 2 6% 4 3 4 3 4 5% 42%	2090
October	1st to 10th	Night	18% 8% 2 7% 4 4 5% 3 4 6% 38%	2090
	11th to 20th	Night	23% 8% 2 7% 6% 4 5% 3 5% 5% 33%	2444
	21st to end	Night	23% 10% 2 7% 4 4 4 4 5% 7% 30%	2717
November	1st to 10th	Night	16% 9% 4 7% 5% 4 5% 4 6% 7% 33%	2537
	11th to 20th	Night	17% 11% 4 6% 4 4 4 4 5% 6% 34%	2615
	21st to end	Night	17% 16% 4 9% 6% 5% 4 4 5% 5% 25%	2986
December	1st to 10th	Night	12% 12% 7% 11% 7% 5% 5% 4 5% 7% 25%	4910
	11th to 20th	Night	20% 12% 5% 10% 6% 5% 4 3 4 5% 27%	5591
	21st to end	Night	16% 15% 5% 9% 5% 4 3 3 3 4 32%	7484

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	62% 2 9% 16% 10%	3598
	11th to 20th	Day	58% 7% 10% 17% 7% 2	3600
	21st to end	Day	42% 4 12% 20% 21% 1	3960
February	1st to 10th	Day	55% 5% 9% 17% 11% 3	1609
	11th to 20th	Day	59% 4 8% 15% 12% 2	1918
	21st to end	Day	54% 5% 7% 20% 10% 3	1650
March	1st to 10th	Day	62% 3 10% 11% 10% 5%	4479
	11th to 20th	Day	54% 6% 14% 17% 9% 1	4786
	21st to end	Day	55% 3 6% 17% 14% 5%	5776
April	1st to 10th	Day	56% 5% 10% 14% 12% 4	2400
	11th to 20th	Day	49% 6% 9% 23% 11% 2	2490
	21st to end	Day	53% 5% 10% 17% 12% 3	2600
May	1st to 10th	Day	54% 4 12% 16% 14% 1	6025
	11th to 20th	Day	52% 5% 15% 20% 6% 3	6322
	21st to end	Day	53% 5% 10% 18% 12% 1	7174
June	1st to 10th	Day	52% 7% 12% 21% 7% 1	3000
	11th to 20th	Day	48% 6% 15% 20% 10% 1	3000
	21st to end	Day	55% 6% 13% 17% 8% 1	3000
July	1st to 10th	Day	49% 7% 16% 22% 6%	6530
	11th to 20th	Day	42% 9% 20% 23% 5%	6285
	21st to end	Day	38% 7% 19% 27% 9%	6728
August	1st to 10th	Day	43% 9% 22% 18% 9%	4504
	11th to 20th	Day	49% 8% 21% 17% 4	4214
	21st to end	Day	44% 8% 17% 19% 12% 1	4519
September	1st to 10th	Day	43% 5% 16% 26% 10%	2400
	11th to 20th	Day	37% 6% 17% 30% 10% 1	2188
	21st to end	Day	47% 4 13% 25% 10%	2090
October	1st to 10th	Day	50% 7% 11% 24% 7%	3480
	11th to 20th	Day	49% 6% 16% 25% 4	2845
	21st to end	Day	48% 5% 20% 15% 11%	3081
November	1st to 10th	Day	52% 7% 11% 21% 8% 1	1761
	11th to 20th	Day	56% 6% 8% 20% 9% 1	1783
	21st to end	Day	61% 6% 12% 14% 7% 1	1410
December	1st to 10th	Day	59% 5% 12% 12% 11%	2280
	11th to 20th	Day	56% 6% 8% 18% 12% 1	2618
	21st to end	Day	56% 4 10% 15% 12% 3	3490
January	1st to 10th	Night	65% 4 8% 15% 8% 1	6349
	11th to 20th	Night	65% 5% 8% 16% 5% 1	6360
	21st to end	Night	47% 4 10% 20% 18% 1	6996
February	1st to 10th	Night	50% 5% 9% 21% 13% 2	2790
	11th to 20th	Night	56% 4 10% 15% 13% 1	2375
	21st to end	Night	54% 4 7% 19% 14% 2	1980
March	1st to 10th	Night	60% 3 10% 12% 13% 2	5374
	11th to 20th	Night	57% 6% 13% 14% 8% 3	5174
	21st to end	Night	57% 2 6% 21% 11% 2	5155
April	1st to 10th	Night	56% 3 7% 16% 14% 4	2000
	11th to 20th	Night	46% 5% 9% 25% 13% 2	1857
	21st to end	Night	53% 4 8% 19% 14% 3	1800
May	1st to 10th	Night	52% 4 9% 20% 13% 1	3976
	11th to 20th	Night	52% 5% 13% 21% 9% 1	3576
	21st to end	Night	45% 5% 15% 18% 14% 2	3710
June	1st to 10th	Night	52% 5% 12% 23% 8% 1	1400
	11th to 20th	Night	43% 5% 13% 24% 11% 3	1400
	21st to end	Night	53% 6% 13% 17% 11%	1400
July	1st to 10th	Night	43% 7% 22% 22% 6%	3313
	11th to 20th	Night	42% 6% 22% 26% 4	3552
	21st to end	Night	34% 7% 21% 28% 10%	3809
August	1st to 10th	Night	44% 5% 17% 26% 7%	2576
	11th to 20th	Night	46% 8% 21% 17% 7% 1	2899
	21st to end	Night	42% 7% 16% 24% 11%	3377
September	1st to 10th	Night	40% 5% 15% 27% 12% 1	2000
	11th to 20th	Night	39% 5% 18% 29% 8%	2169
	21st to end	Night	44% 5% 12% 27% 12%	2090
October	1st to 10th	Night	48% 6% 10% 27% 9%	3480
	11th to 20th	Night	48% 5% 13% 28% 5%	4071
	21st to end	Night	45% 4 19% 18% 12% 1	4467
November	1st to 10th	Night	48% 6% 12% 25% 8% 1	2537
	11th to 20th	Night	49% 6% 11% 21% 12% 1	2615
	21st to end	Night	58% 6% 10% 17% 7% 1	2986
December	1st to 10th	Night	57% 7% 12% 17% 6%	4910
	11th to 20th	Night	58% 4 8% 20% 10% 1	5592
	21st to end	Night	58% 3 8% 17% 13% 2	7484

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% 23% 35% 14% 6% 1	200
	11th to 20th	Day	22% 29% 33% 14% 4	200
	21st to end	Day	16% 27% 37% 14% 5% 1	220
February	1st to 10th	Day	25% 31% 34% 7% 3	209
	11th to 20th	Day	21% 24% 36% 15% 4	477
	21st to end	Day	24% 22% 32% 17% 4	414
March	1st to 10th	Day	25% 24% 31% 16% 3 1	500
	11th to 20th	Day	25% 19% 32% 17% 6% 1	500
	21st to end	Day	25% 21% 31% 16% 6% 1	550
April	1st to 10th	Day	28% 23% 28% 14% 5% 1	500
	11th to 20th	Day	29% 20% 32% 15% 3 1	492
	21st to end	Day	29% 20% 34% 12% 2 2	500
May	1st to 10th	Day	29% 17% 31% 17% 6% 1	503
	11th to 20th	Day	23% 14% 36% 19% 6% 2	527
	21st to end	Day	25% 20% 31% 18% 6%	668
June	1st to 10th	Day	23% 14% 32% 22% 7% 1	730
	11th to 20th	Day	23% 17% 28% 22% 9% 1	730
	21st to end	Day	25% 14% 28% 25% 7% 1	730
July	1st to 10th	Day	19% 15% 33% 24% 8% 1	635
	11th to 20th	Day	19% 13% 38% 22% 7% 1	524
	21st to end	Day	16% 13% 38% 25% 8% 1	576
August	1st to 10th	Day	16% 13% 34% 25% 9% 2	526
	11th to 20th	Day	17% 10% 31% 26% 13% 2	519
	21st to end	Day	20% 17% 27% 21% 11% 4	583
September	1st to 10th	Day	20% 15% 29% 25% 8% 4	530
	11th to 20th	Day	19% 12% 32% 21% 11% 5%	522
	21st to end	Day	23% 16% 27% 21% 9% 4	490
October	1st to 10th	Day	23% 16% 29% 22% 9% 2	490
	11th to 20th	Day	27% 19% 28% 17% 9% 1	395
	21st to end	Day	37% 17% 24% 17% 5% 1	429
November	1st to 10th	Day	28% 21% 29% 16% 5% 1	395
	11th to 20th	Day	28% 19% 26% 19% 8% 1	400
	21st to end	Day	31% 22% 32% 12% 2	210
December	1st to 10th	Day	28% 17% 28% 21% 7%	200
	11th to 20th	Day	32% 23% 27% 13% 5% 1	200
	21st to end	Day	30% 20% 32% 13% 5%	220
January	1st to 10th	Night	21% 18% 31% 26% 4	800
	11th to 20th	Night	20% 18% 32% 23% 7% 1	800
	21st to end	Night	14% 16% 34% 30% 6% 1	880
February	1st to 10th	Night	14% 21% 34% 26% 6%	800
	11th to 20th	Night	19% 19% 37% 20% 5% 1	783
	21st to end	Night	21% 15% 33% 25% 5%	660
March	1st to 10th	Night	19% 17% 35% 24% 4	800
	11th to 20th	Night	20% 18% 35% 21% 6% 1	800
	21st to end	Night	20% 17% 33% 21% 7% 1	880
April	1st to 10th	Night	28% 16% 29% 21% 5%	800
	11th to 20th	Night	24% 12% 35% 23% 6%	673
	21st to end	Night	29% 11% 31% 22% 6% 1	600
May	1st to 10th	Night	26% 11% 30% 28% 5% 1	568
	11th to 20th	Night	22% 11% 27% 31% 9%	394
	21st to end	Night	25% 8% 33% 27% 7%	433
June	1st to 10th	Night	22% 9% 28% 31% 10% 1	400
	11th to 20th	Night	20% 7% 25% 36% 12% 1	400
	21st to end	Night	25% 7% 21% 38% 10% 1	400
July	1st to 10th	Night	19% 7% 31% 33% 11% 1	390
	11th to 20th	Night	19% 5% 25% 38% 12% 1	388
	21st to end	Night	16% 4 22% 44% 13% 1	438
August	1st to 10th	Night	17% 3 22% 40% 18% 1	398
	11th to 20th	Night	17% 6% 24% 35% 17% 1	592
	21st to end	Night	17% 9% 24% 34% 14% 2	749
September	1st to 10th	Night	18% 7% 27% 36% 12% 1	800
	11th to 20th	Night	19% 7% 27% 29% 16% 2	793
	21st to end	Night	22% 11% 23% 31% 13% 1	760
October	1st to 10th	Night	22% 12% 25% 29% 11% 1	760
	11th to 20th	Night	26% 12% 26% 26% 9% 1	760
	21st to end	Night	30% 14% 28% 20% 7%	836
November	1st to 10th	Night	23% 17% 29% 22% 7% 1	780
	11th to 20th	Night	22% 18% 25% 25% 8% 1	807
	21st to end	Night	27% 18% 27% 21% 5% 1	900
December	1st to 10th	Night	27% 14% 28% 24% 7% 1	900
	11th to 20th	Night	24% 20% 25% 23% 5% 1	900
	21st to end	Night	27% 18% 28% 20% 7% 1	987

Page generated at 2025-09-16 01:49:16. Version ac07

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