Québec
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Québec clear sky chart from 2005-11-06 to 2025-09-04.

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% 3 8% 5% 5% 5% 4 5% 7% 31%	125837
	Night	18% 12% 4 9% 5% 5% 4 3 5% 6% 29%	122906
Transparency	Day	52% 6% 13% 19% 9% 1	129279
	Night	56% 6% 12% 18% 8% 1	127539
Seeing	Day	23% 14% 30% 22% 9% 2	16307
	Night	24% 11% 28% 28% 8% 1	24728

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% 12% 6% 4 3 2 3 4 23%	3597
	11th to 20th	Day	9% 15% 8% 15% 7% 6% 4 3 4 5% 24%	3570
	21st to end	Day	7% 13% 5% 11% 6% 5% 4 4 5% 7% 34%	3960
February	1st to 10th	Day	10% 14% 6% 12% 7% 5% 5% 4 5% 6% 26%	1600
	11th to 20th	Day	14% 14% 6% 10% 5% 5% 4 4 5% 6% 27%	1933
	21st to end	Day	13% 14% 5% 10% 7% 4 4 4 4 7% 28%	1650
March	1st to 10th	Day	21% 14% 5% 9% 6% 5% 4 3 3 5% 26%	4476
	11th to 20th	Day	14% 14% 4 7% 5% 5% 5% 4 6% 7% 30%	4749
	21st to end	Day	17% 14% 4 7% 4 4 4 3 4 5% 34%	5804
April	1st to 10th	Day	21% 12% 3 7% 5% 5% 4 3 5% 5% 30%	2400
	11th to 20th	Day	20% 7% 2 6% 5% 5% 4 3 5% 6% 37%	2472
	21st to end	Day	24% 8% 3 7% 4 4 4 4 4 6% 31%	2600
May	1st to 10th	Day	26% 9% 2 7% 4 4 4 3 5% 6% 29%	6019
	11th to 20th	Day	22% 6% 2 7% 5% 5% 5% 3 6% 8% 31%	6318
	21st to end	Day	20% 8% 2 8% 5% 5% 6% 4 6% 6% 29%	7031
June	1st to 10th	Day	19% 6% 3 7% 5% 5% 6% 4 8% 7% 28%	3000
	11th to 20th	Day	19% 7% 2 5% 5% 5% 5% 4 6% 8% 34%	3000
	21st to end	Day	23% 8% 3 7% 6% 5% 5% 4 5% 7% 27%	3000
July	1st to 10th	Day	17% 7% 3 8% 5% 5% 6% 5% 7% 9% 28%	6453
	11th to 20th	Day	16% 6% 3 7% 4 5% 5% 5% 7% 9% 34%	6360
	21st to end	Day	12% 5% 2 5% 4 5% 5% 4 7% 9% 42%	6926
August	1st to 10th	Day	15% 5% 2 7% 5% 5% 6% 5% 7% 10% 32%	4537
	11th to 20th	Day	19% 6% 2 7% 5% 6% 4 4 6% 9% 30%	4175
	21st to end	Day	21% 5% 2 7% 4 5% 3 3 5% 7% 38%	4479
September	1st to 10th	Day	17% 7% 2 6% 4 4 4 4 5% 9% 38%	2316
	11th to 20th	Day	18% 5% 2 4 3 3 3 2 5% 8% 46%	2109
	21st to end	Day	21% 7% 2 7% 3 4 4 3 5% 6% 37%	2090
October	1st to 10th	Day	20% 8% 3 6% 5% 4 5% 4 5% 7% 33%	2089
	11th to 20th	Day	24% 9% 3 7% 6% 5% 5% 4 6% 7% 25%	1738
	21st to end	Day	27% 10% 4 7% 4 4 4 4 5% 5% 25%	1881
November	1st to 10th	Day	20% 11% 3 8% 5% 5% 4 3 4 6% 31%	1761
	11th to 20th	Day	22% 12% 5% 8% 5% 4 5% 3 5% 4 27%	1800
	21st to end	Day	24% 16% 5% 8% 4 4 4 4 4 5% 22%	1440
December	1st to 10th	Day	18% 16% 4 9% 5% 5% 5% 4 6% 6% 21%	2280
	11th to 20th	Day	20% 14% 5% 9% 6% 5% 4 3 4 5% 27%	2618
	21st to end	Day	20% 17% 4 8% 4 5% 4 4 5% 4 25%	3606
January	1st to 10th	Night	16% 23% 6% 14% 6% 4 3 2 3 3 21%	6349
	11th to 20th	Night	11% 20% 8% 15% 7% 5% 4 3 4 4 19%	6315
	21st to end	Night	8% 13% 4 12% 7% 6% 5% 5% 6% 7% 28%	6996
February	1st to 10th	Night	11% 13% 6% 11% 8% 5% 5% 4 5% 5% 28%	2799
	11th to 20th	Night	13% 17% 5% 11% 6% 4 4 3 5% 6% 26%	2349
	21st to end	Night	15% 15% 4 10% 5% 5% 4 3 4 6% 30%	1980
March	1st to 10th	Night	22% 14% 4 9% 4 3 5% 3 4 5% 25%	5364
	11th to 20th	Night	16% 14% 3 9% 6% 6% 5% 4 6% 6% 25%	5209
	21st to end	Night	19% 15% 4 8% 5% 4 3 3 3 5% 31%	5110
April	1st to 10th	Night	22% 14% 4 7% 5% 4 3 3 4 5% 29%	2000
	11th to 20th	Night	21% 8% 3 7% 4 4 4 4 5% 6% 33%	1877
	21st to end	Night	24% 10% 2 7% 5% 3 3 3 4 5% 35%	1800
May	1st to 10th	Night	25% 8% 3 6% 5% 5% 5% 3 4 6% 30%	3962
	11th to 20th	Night	27% 7% 3 7% 4 4 4 3 4 6% 31%	3575
	21st to end	Night	19% 7% 2 6% 5% 5% 5% 4 5% 7% 35%	3843
June	1st to 10th	Night	22% 8% 3 6% 5% 4 5% 5% 5% 8% 29%	1400
	11th to 20th	Night	20% 6% 3 6% 4 5% 3 4 6% 7% 36%	1400
	21st to end	Night	22% 9% 4 7% 5% 4 5% 3 4 7% 30%	1400
July	1st to 10th	Night	15% 8% 2 7% 5% 6% 6% 5% 7% 8% 31%	3505
	11th to 20th	Night	21% 7% 2 6% 5% 4 4 3 5% 7% 36%	3600
	21st to end	Night	13% 5% 2 7% 5% 5% 5% 3 5% 7% 42%	3926
August	1st to 10th	Night	18% 7% 3 7% 5% 5% 5% 4 5% 7% 35%	2586
	11th to 20th	Night	19% 7% 3 8% 5% 5% 5% 4 6% 7% 32%	2866
	21st to end	Night	21% 6% 3 7% 5% 5% 5% 3 5% 6% 34%	3416
September	1st to 10th	Night	18% 6% 2 7% 5% 3 4 3 4 7% 41%	1931
	11th to 20th	Night	18% 7% 2 5% 4 4 3 3 5% 6% 44%	2070
	21st to end	Night	20% 7% 3 5% 4 4 4 3 5% 6% 40%	2090
October	1st to 10th	Night	19% 8% 2 7% 4 4 4 4 5% 6% 36%	2090
	11th to 20th	Night	26% 8% 3 7% 5% 5% 4 3 5% 4 31%	2440
	21st to end	Night	25% 11% 3 7% 4 4 3 3 5% 7% 30%	2717
November	1st to 10th	Night	20% 11% 3 7% 5% 5% 4 3 6% 6% 31%	2537
	11th to 20th	Night	20% 11% 3 8% 5% 4 4 4 4 6% 32%	2600
	21st to end	Night	23% 15% 5% 8% 4 5% 5% 3 4 5% 24%	2954
December	1st to 10th	Night	17% 16% 6% 11% 7% 6% 5% 4 4 4 19%	4910
	11th to 20th	Night	23% 13% 4 9% 6% 5% 4 3 4 6% 23%	5591
	21st to end	Night	21% 18% 4 9% 4 4 4 3 4 5% 24%	7349

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	66% 4 8% 14% 7%	3598
	11th to 20th	Day	63% 5% 9% 16% 5% 1	3600
	21st to end	Day	50% 5% 9% 20% 15%	3960
February	1st to 10th	Day	58% 5% 11% 15% 9% 2	1600
	11th to 20th	Day	59% 5% 13% 13% 9% 1	1942
	21st to end	Day	56% 5% 10% 19% 9% 2	1650
March	1st to 10th	Day	61% 5% 9% 12% 10% 3	4479
	11th to 20th	Day	52% 6% 16% 17% 9% 1	4749
	21st to end	Day	53% 4 8% 17% 14% 3	5804
April	1st to 10th	Day	57% 4 11% 14% 11% 3	2400
	11th to 20th	Day	48% 5% 11% 23% 11% 2	2472
	21st to end	Day	54% 6% 11% 17% 12% 2	2600
May	1st to 10th	Day	54% 5% 12% 15% 13% 1	6030
	11th to 20th	Day	50% 8% 16% 17% 6% 2	6322
	21st to end	Day	52% 8% 11% 17% 10% 3	7031
June	1st to 10th	Day	50% 10% 12% 19% 8% 1	3000
	11th to 20th	Day	46% 8% 14% 20% 11% 1	3000
	21st to end	Day	56% 7% 11% 16% 9%	3000
July	1st to 10th	Day	50% 8% 14% 22% 6%	6383
	11th to 20th	Day	44% 8% 20% 24% 5%	6285
	21st to end	Day	37% 7% 19% 29% 9%	6728
August	1st to 10th	Day	44% 9% 20% 20% 6%	4523
	11th to 20th	Day	49% 8% 20% 18% 5%	4214
	21st to end	Day	45% 8% 15% 19% 12% 1	4479
September	1st to 10th	Day	41% 7% 17% 24% 10%	2316
	11th to 20th	Day	37% 6% 17% 30% 10%	2109
	21st to end	Day	46% 6% 14% 25% 8%	2090
October	1st to 10th	Day	54% 7% 11% 23% 5%	3466
	11th to 20th	Day	52% 8% 18% 21% 2	2863
	21st to end	Day	53% 6% 17% 16% 7%	3081
November	1st to 10th	Day	55% 6% 11% 20% 7%	1761
	11th to 20th	Day	60% 5% 9% 19% 6% 1	1800
	21st to end	Day	65% 5% 12% 12% 5%	1440
December	1st to 10th	Day	64% 5% 12% 12% 7%	2280
	11th to 20th	Day	60% 4 11% 14% 11%	2618
	21st to end	Day	61% 6% 11% 13% 8% 1	3606
January	1st to 10th	Night	69% 5% 8% 12% 6%	6349
	11th to 20th	Night	68% 5% 8% 15% 3	6360
	21st to end	Night	54% 5% 10% 18% 11%	6996
February	1st to 10th	Night	59% 5% 10% 17% 9% 1	2799
	11th to 20th	Night	60% 5% 11% 15% 9% 1	2351
	21st to end	Night	56% 5% 8% 17% 13% 1	1980
March	1st to 10th	Night	62% 4 9% 12% 11% 1	5374
	11th to 20th	Night	58% 7% 12% 14% 7% 2	5210
	21st to end	Night	58% 3 6% 21% 10% 2	5110
April	1st to 10th	Night	57% 4 9% 16% 12% 2	2000
	11th to 20th	Night	50% 5% 10% 20% 12% 2	1877
	21st to end	Night	53% 5% 8% 18% 15% 2	1800
May	1st to 10th	Night	55% 6% 10% 16% 12% 1	3968
	11th to 20th	Night	53% 7% 11% 19% 9% 1	3576
	21st to end	Night	48% 7% 12% 17% 15% 2	3844
June	1st to 10th	Night	51% 7% 12% 19% 10% 1	1400
	11th to 20th	Night	46% 7% 13% 20% 12% 3	1400
	21st to end	Night	54% 6% 12% 17% 11%	1400
July	1st to 10th	Night	48% 7% 20% 19% 6%	3465
	11th to 20th	Night	47% 7% 19% 23% 4	3552
	21st to end	Night	42% 7% 18% 26% 8%	3809
August	1st to 10th	Night	48% 8% 16% 23% 6%	2576
	11th to 20th	Night	50% 10% 18% 17% 6% 1	2893
	21st to end	Night	50% 6% 13% 20% 11%	3416
September	1st to 10th	Night	44% 6% 14% 24% 11% 1	1931
	11th to 20th	Night	40% 6% 17% 28% 8% 1	2070
	21st to end	Night	45% 6% 11% 26% 12%	2090
October	1st to 10th	Night	50% 6% 11% 26% 7%	3480
	11th to 20th	Night	54% 6% 13% 23% 3	4054
	21st to end	Night	51% 6% 18% 15% 10%	4467
November	1st to 10th	Night	54% 6% 13% 20% 6% 1	2537
	11th to 20th	Night	54% 7% 13% 18% 9%	2600
	21st to end	Night	64% 6% 11% 13% 6% 1	2954
December	1st to 10th	Night	67% 6% 12% 12% 3	4910
	11th to 20th	Night	63% 4 8% 17% 7%	5592
	21st to end	Night	63% 4 9% 16% 7% 1	7349

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	29% 20% 30% 17% 4 1	200
	11th to 20th	Day	26% 22% 31% 15% 6% 1	200
	21st to end	Day	16% 20% 37% 22% 4 1	220
February	1st to 10th	Day	24% 24% 36% 15% 3 1	200
	11th to 20th	Day	24% 19% 36% 17% 3	489
	21st to end	Day	22% 21% 30% 22% 5%	414
March	1st to 10th	Day	24% 19% 30% 20% 6% 1	500
	11th to 20th	Day	22% 18% 34% 18% 6% 1	500
	21st to end	Day	23% 17% 27% 21% 10% 1	550
April	1st to 10th	Day	28% 16% 29% 19% 8%	500
	11th to 20th	Day	27% 13% 30% 21% 8% 1	492
	21st to end	Day	29% 17% 31% 17% 5% 1	500
May	1st to 10th	Day	28% 16% 33% 17% 5% 1	503
	11th to 20th	Day	20% 14% 31% 24% 9% 2	527
	21st to end	Day	24% 18% 31% 20% 6% 1	603
June	1st to 10th	Day	22% 14% 29% 26% 9% 1	730
	11th to 20th	Day	21% 11% 28% 26% 12% 1	730
	21st to end	Day	26% 10% 27% 24% 11% 2	730
July	1st to 10th	Day	18% 12% 30% 26% 12% 2	566
	11th to 20th	Day	15% 11% 35% 26% 11% 2	524
	21st to end	Day	14% 10% 34% 27% 12% 2	576
August	1st to 10th	Day	16% 8% 28% 28% 15% 4	526
	11th to 20th	Day	18% 5% 28% 27% 18% 4	519
	21st to end	Day	21% 11% 25% 21% 15% 7%	583
September	1st to 10th	Day	18% 11% 27% 26% 15% 4	502
	11th to 20th	Day	18% 11% 27% 22% 18% 5%	490
	21st to end	Day	20% 13% 24% 23% 14% 6%	490
October	1st to 10th	Day	22% 13% 26% 25% 10% 3	490
	11th to 20th	Day	29% 14% 27% 18% 10% 1	404
	21st to end	Day	33% 15% 28% 18% 6%	429
November	1st to 10th	Day	31% 15% 24% 23% 7% 1	395
	11th to 20th	Day	28% 16% 30% 18% 9%	400
	21st to end	Day	33% 18% 30% 16% 3	205
December	1st to 10th	Day	31% 12% 29% 20% 6% 3	200
	11th to 20th	Day	30% 19% 29% 16% 5% 2	200
	21st to end	Day	33% 16% 31% 15% 5% 1	220
January	1st to 10th	Night	26% 17% 32% 21% 4	800
	11th to 20th	Night	25% 15% 30% 26% 5%	800
	21st to end	Night	16% 12% 34% 31% 6% 1	880
February	1st to 10th	Night	19% 13% 35% 27% 6%	800
	11th to 20th	Night	22% 15% 39% 20% 4 1	783
	21st to end	Night	24% 12% 32% 28% 5%	660
March	1st to 10th	Night	23% 12% 34% 25% 6%	800
	11th to 20th	Night	24% 15% 32% 22% 6% 1	800
	21st to end	Night	24% 10% 30% 28% 6% 1	880
April	1st to 10th	Night	28% 14% 27% 25% 6%	800
	11th to 20th	Night	26% 10% 33% 25% 6%	693
	21st to end	Night	29% 11% 30% 24% 6%	600
May	1st to 10th	Night	24% 10% 33% 27% 6%	560
	11th to 20th	Night	25% 9% 27% 31% 7%	394
	21st to end	Night	27% 6% 29% 30% 8%	433
June	1st to 10th	Night	25% 7% 27% 36% 5% 1	400
	11th to 20th	Night	19% 7% 25% 37% 12%	400
	21st to end	Night	24% 6% 23% 38% 9%	400
July	1st to 10th	Night	17% 5% 29% 37% 11% 1	390
	11th to 20th	Night	19% 4 22% 41% 13% 1	388
	21st to end	Night	15% 5% 18% 47% 14%	438
August	1st to 10th	Night	18% 4 14% 47% 17% 1	398
	11th to 20th	Night	16% 5% 21% 40% 17% 1	586
	21st to end	Night	19% 5% 24% 33% 18% 2	775
September	1st to 10th	Night	20% 5% 25% 33% 16% 1	773
	11th to 20th	Night	20% 6% 23% 31% 18% 2	760
	21st to end	Night	22% 6% 25% 31% 15% 1	760
October	1st to 10th	Night	22% 9% 26% 33% 9% 1	760
	11th to 20th	Night	29% 10% 24% 27% 9% 1	760
	21st to end	Night	30% 12% 29% 25% 4	836
November	1st to 10th	Night	27% 13% 26% 26% 9%	780
	11th to 20th	Night	25% 13% 27% 26% 8% 1	800
	21st to end	Night	31% 13% 30% 19% 6%	883
December	1st to 10th	Night	30% 12% 28% 22% 7% 1	900
	11th to 20th	Night	26% 18% 28% 22% 6% 1	900
	21st to end	Night	32% 15% 28% 19% 5% 1	958

Page generated at 2025-09-01 01:51:02. Version ac07

Copyright © 2025 Attilla Danko.