Tadoussac
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tadoussac 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% 10% 3 8% 5% 5% 5% 4 6% 7% 32%	131006
	Night	16% 11% 4 9% 5% 5% 5% 4 5% 6% 30%	130600
Transparency	Day	49% 7% 15% 20% 8% 1	134436
	Night	52% 7% 12% 20% 8% 1	135258
Seeing	Day	21% 11% 28% 27% 11% 2	17340
	Night	22% 11% 28% 28% 10% 1	25634

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	13% 18% 5% 11% 7% 5% 4 3 5% 5% 23%	4190
	11th to 20th	Day	10% 14% 5% 14% 7% 5% 6% 4 6% 6% 22%	4650
	21st to end	Day	4 8% 6% 11% 7% 7% 5% 5% 7% 9% 31%	5124
February	1st to 10th	Day	6% 14% 5% 9% 7% 6% 6% 5% 6% 7% 28%	1722
	11th to 20th	Day	12% 14% 5% 10% 8% 4 4 4 7% 7% 26%	1920
	21st to end	Day	12% 10% 4 9% 6% 6% 5% 4 6% 7% 32%	1730
March	1st to 10th	Day	20% 12% 3 8% 5% 4 5% 3 6% 6% 28%	4576
	11th to 20th	Day	15% 15% 3 8% 5% 5% 6% 4 6% 7% 24%	4958
	21st to end	Day	15% 16% 4 9% 4 4 4 3 4 6% 31%	5634
April	1st to 10th	Day	19% 11% 4 7% 4 4 4 4 5% 7% 30%	2400
	11th to 20th	Day	18% 9% 2 7% 5% 4 5% 3 4 7% 37%	2557
	21st to end	Day	22% 9% 2 7% 4 4 5% 3 4 6% 34%	2600
May	1st to 10th	Day	19% 10% 3 7% 5% 4 4 3 5% 6% 35%	5949
	11th to 20th	Day	25% 8% 2 6% 3 4 4 3 5% 5% 35%	6445
	21st to end	Day	18% 8% 3 8% 5% 4 4 4 6% 9% 31%	7451
June	1st to 10th	Day	19% 8% 3 8% 5% 5% 4 4 5% 7% 32%	3000
	11th to 20th	Day	17% 7% 2 6% 5% 4 5% 4 6% 7% 37%	3000
	21st to end	Day	21% 8% 3 8% 5% 5% 4 5% 5% 7% 30%	3000
July	1st to 10th	Day	14% 8% 3 7% 5% 5% 6% 5% 8% 9% 30%	6820
	11th to 20th	Day	14% 6% 3 8% 5% 6% 6% 6% 7% 8% 32%	6604
	21st to end	Day	10% 5% 2 6% 4 5% 5% 5% 6% 8% 44%	6926
August	1st to 10th	Day	12% 6% 2 6% 5% 5% 6% 5% 8% 9% 37%	4478
	11th to 20th	Day	16% 7% 3 8% 6% 6% 6% 4 8% 6% 29%	4175
	21st to end	Day	15% 6% 2 6% 5% 5% 5% 5% 7% 8% 37%	4675
September	1st to 10th	Day	14% 5% 3 6% 4 4 6% 4 6% 8% 39%	2375
	11th to 20th	Day	15% 6% 2 6% 3 3 4 3 6% 6% 47%	2200
	21st to end	Day	17% 7% 2 6% 5% 4 3 4 5% 7% 42%	2200
October	1st to 10th	Day	17% 7% 3 7% 4 4 5% 4 5% 8% 36%	2150
	11th to 20th	Day	20% 8% 3 8% 5% 6% 5% 4 6% 7% 29%	1863
	21st to end	Day	25% 10% 3 6% 4 4 5% 3 4 7% 28%	1980
November	1st to 10th	Day	16% 12% 2 9% 6% 5% 6% 4 5% 7% 27%	1851
	11th to 20th	Day	18% 13% 4 8% 5% 5% 5% 4 6% 7% 27%	1715
	21st to end	Day	21% 14% 5% 7% 5% 5% 5% 4 5% 6% 24%	1497
December	1st to 10th	Day	17% 17% 4 8% 5% 4 4 3 5% 6% 27%	2350
	11th to 20th	Day	17% 12% 3 7% 7% 4 6% 4 5% 6% 29%	2688
	21st to end	Day	18% 12% 5% 9% 5% 4 4 3 4 5% 32%	3553
January	1st to 10th	Night	14% 15% 5% 13% 7% 6% 5% 4 5% 5% 20%	8714
	11th to 20th	Night	9% 16% 6% 15% 7% 5% 6% 4 6% 6% 20%	8235
	21st to end	Night	4 9% 5% 10% 7% 7% 7% 5% 8% 10% 27%	9057
February	1st to 10th	Night	9% 13% 5% 11% 6% 5% 4 4 6% 7% 31%	2898
	11th to 20th	Night	11% 15% 6% 11% 6% 5% 4 4 5% 7% 26%	2584
	21st to end	Night	13% 13% 5% 10% 5% 4 5% 3 4 5% 33%	2076
March	1st to 10th	Night	19% 13% 4 9% 6% 5% 5% 3 5% 6% 25%	5484
	11th to 20th	Night	14% 16% 5% 10% 7% 5% 5% 4 5% 6% 23%	5156
	21st to end	Night	20% 16% 4 8% 4 3 3 3 4 5% 31%	5294
April	1st to 10th	Night	22% 13% 3 8% 5% 5% 4 3 3 4 31%	2000
	11th to 20th	Night	20% 10% 3 6% 5% 4 3 3 6% 6% 33%	1791
	21st to end	Night	25% 9% 3 5% 3 3 3 4 5% 5% 34%	1800
May	1st to 10th	Night	19% 7% 3 7% 5% 4 4 3 5% 6% 36%	4022
	11th to 20th	Night	26% 9% 2 6% 4 3 4 3 5% 7% 32%	3451
	21st to end	Night	19% 7% 2 6% 4 4 5% 4 6% 7% 34%	3446
June	1st to 10th	Night	19% 9% 3 8% 5% 4 5% 4 6% 6% 31%	1400
	11th to 20th	Night	17% 7% 2 5% 4 5% 5% 4 7% 7% 37%	1400
	21st to end	Night	23% 10% 3 7% 5% 4 4 4 6% 7% 28%	1400
July	1st to 10th	Night	12% 7% 3 8% 5% 4 6% 5% 8% 9% 32%	3160
	11th to 20th	Night	14% 6% 3 8% 5% 5% 6% 5% 6% 8% 33%	3350
	21st to end	Night	10% 6% 2 6% 4 5% 5% 4 5% 7% 44%	3926
August	1st to 10th	Night	16% 6% 2 8% 5% 5% 5% 4 7% 7% 35%	2638
	11th to 20th	Night	14% 7% 3 9% 7% 6% 6% 5% 7% 8% 27%	2872
	21st to end	Night	17% 6% 3 6% 4 4 4 3 5% 7% 41%	3223
September	1st to 10th	Night	14% 7% 2 7% 5% 5% 5% 3 4 7% 42%	2021
	11th to 20th	Night	18% 6% 2 5% 4 4 4 4 4 5% 44%	2200
	21st to end	Night	17% 8% 2 6% 3 4 4 3 5% 4 44%	2200
October	1st to 10th	Night	17% 7% 2 6% 4 4 4 3 5% 7% 42%	2250
	11th to 20th	Night	23% 7% 3 6% 4 5% 4 3 5% 6% 32%	2535
	21st to end	Night	24% 8% 3 6% 4 4 4 3 5% 6% 32%	2860
November	1st to 10th	Night	19% 11% 4 8% 5% 4 4 4 5% 6% 31%	2667
	11th to 20th	Night	19% 12% 4 8% 5% 4 4 4 5% 5% 30%	2903
	21st to end	Night	20% 15% 5% 9% 5% 5% 4 3 5% 6% 23%	3119
December	1st to 10th	Night	14% 15% 5% 11% 5% 4 4 3 4 6% 28%	5060
	11th to 20th	Night	20% 12% 4 9% 6% 4 5% 4 5% 6% 27%	5741
	21st to end	Night	15% 12% 4 10% 6% 4 4 3 5% 6% 29%	7667

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% 6% 10% 18% 4	4191
	11th to 20th	Day	59% 7% 11% 17% 6% 1	4680
	21st to end	Day	46% 7% 13% 21% 12%	5124
February	1st to 10th	Day	52% 8% 12% 17% 9% 2	1722
	11th to 20th	Day	57% 6% 11% 16% 10%	1928
	21st to end	Day	50% 6% 10% 21% 11% 2	1730
March	1st to 10th	Day	54% 6% 14% 10% 13% 3	4579
	11th to 20th	Day	57% 8% 13% 13% 7% 1	4958
	21st to end	Day	54% 5% 7% 19% 12% 3	5634
April	1st to 10th	Day	53% 6% 9% 19% 10% 2	2400
	11th to 20th	Day	47% 5% 12% 25% 10% 2	2557
	21st to end	Day	52% 5% 10% 18% 14% 2	2600
May	1st to 10th	Day	49% 6% 14% 19% 10% 1	5960
	11th to 20th	Day	51% 5% 14% 21% 7% 2	6449
	21st to end	Day	49% 7% 13% 21% 10% 1	7451
June	1st to 10th	Day	51% 6% 11% 20% 10% 1	3000
	11th to 20th	Day	46% 6% 15% 20% 11% 1	3000
	21st to end	Day	52% 8% 13% 17% 9% 1	3000
July	1st to 10th	Day	46% 8% 16% 24% 6%	6745
	11th to 20th	Day	45% 9% 21% 20% 4	6523
	21st to end	Day	36% 8% 19% 29% 8%	6728
August	1st to 10th	Day	40% 9% 22% 23% 6%	4464
	11th to 20th	Day	49% 11% 18% 19% 4	4214
	21st to end	Day	41% 9% 19% 22% 9%	4675
September	1st to 10th	Day	40% 8% 18% 24% 10%	2375
	11th to 20th	Day	37% 6% 19% 29% 9% 1	2200
	21st to end	Day	41% 6% 17% 26% 9%	2200
October	1st to 10th	Day	50% 6% 17% 21% 6%	3501
	11th to 20th	Day	46% 7% 19% 25% 3	3014
	21st to end	Day	47% 8% 18% 21% 6%	3180
November	1st to 10th	Day	54% 7% 15% 19% 5%	1851
	11th to 20th	Day	56% 6% 13% 20% 5%	1715
	21st to end	Day	59% 7% 13% 15% 6%	1497
December	1st to 10th	Day	56% 7% 13% 17% 7%	2350
	11th to 20th	Day	53% 7% 12% 19% 8%	2688
	21st to end	Day	54% 6% 11% 20% 7% 3	3553
January	1st to 10th	Night	63% 7% 11% 13% 5%	8714
	11th to 20th	Night	62% 7% 11% 15% 6%	8280
	21st to end	Night	47% 7% 12% 21% 12%	9057
February	1st to 10th	Night	52% 6% 10% 20% 11% 1	2898
	11th to 20th	Night	57% 6% 10% 18% 8%	2587
	21st to end	Night	53% 5% 8% 23% 9% 1	2076
March	1st to 10th	Night	58% 6% 9% 14% 11%	5494
	11th to 20th	Night	60% 7% 11% 13% 8% 1	5157
	21st to end	Night	55% 4 7% 20% 12% 1	5294
April	1st to 10th	Night	58% 5% 6% 16% 13% 2	2000
	11th to 20th	Night	49% 5% 9% 21% 14% 1	1791
	21st to end	Night	52% 5% 9% 20% 13% 2	1800
May	1st to 10th	Night	47% 7% 11% 19% 15% 1	4028
	11th to 20th	Night	52% 6% 11% 22% 9% 1	3452
	21st to end	Night	45% 10% 11% 21% 13% 1	3447
June	1st to 10th	Night	52% 5% 12% 21% 9% 2	1400
	11th to 20th	Night	44% 7% 14% 19% 13% 3	1400
	21st to end	Night	54% 6% 12% 18% 10%	1400
July	1st to 10th	Night	45% 8% 17% 24% 6%	3125
	11th to 20th	Night	45% 9% 21% 22% 3	3308
	21st to end	Night	38% 6% 21% 25% 9%	3809
August	1st to 10th	Night	45% 8% 18% 22% 6%	2628
	11th to 20th	Night	51% 11% 18% 14% 6%	2899
	21st to end	Night	42% 6% 14% 29% 9%	3223
September	1st to 10th	Night	42% 7% 14% 27% 10% 1	2021
	11th to 20th	Night	42% 5% 17% 25% 10% 1	2200
	21st to end	Night	42% 6% 12% 27% 12%	2200
October	1st to 10th	Night	46% 5% 12% 29% 8% 1	3679
	11th to 20th	Night	47% 7% 13% 29% 4	4123
	21st to end	Night	48% 7% 17% 21% 7%	4610
November	1st to 10th	Night	52% 6% 14% 20% 8%	2667
	11th to 20th	Night	53% 6% 13% 20% 7%	2903
	21st to end	Night	62% 6% 10% 15% 7%	3119
December	1st to 10th	Night	57% 5% 14% 20% 4	5060
	11th to 20th	Night	55% 8% 8% 22% 6%	5742
	21st to end	Night	55% 5% 12% 19% 7% 1	7667

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	25% 16% 35% 18% 5% 1	220
	11th to 20th	Day	21% 23% 30% 18% 6% 1	220
	21st to end	Day	14% 21% 27% 29% 9% 1	242
February	1st to 10th	Day	16% 16% 34% 24% 7% 3	262
	11th to 20th	Day	19% 21% 36% 17% 6%	467
	21st to end	Day	17% 18% 38% 20% 6% 1	446
March	1st to 10th	Day	25% 16% 31% 21% 7% 1	540
	11th to 20th	Day	22% 18% 30% 20% 9% 1	528
	21st to end	Day	26% 15% 32% 21% 5% 2	550
April	1st to 10th	Day	26% 18% 29% 21% 5% 1	500
	11th to 20th	Day	20% 11% 33% 26% 7% 2	492
	21st to end	Day	25% 13% 32% 22% 8% 1	500
May	1st to 10th	Day	24% 12% 27% 25% 10% 2	503
	11th to 20th	Day	21% 8% 27% 28% 12% 3	576
	21st to end	Day	22% 9% 29% 28% 9% 3	790
June	1st to 10th	Day	24% 6% 27% 30% 11% 3	730
	11th to 20th	Day	19% 6% 28% 29% 15% 3	730
	21st to end	Day	22% 7% 25% 33% 13% 2	730
July	1st to 10th	Day	19% 5% 24% 36% 14% 2	720
	11th to 20th	Day	14% 5% 24% 37% 17% 2	632
	21st to end	Day	13% 6% 24% 38% 18% 2	576
August	1st to 10th	Day	15% 4 20% 38% 18% 4	526
	11th to 20th	Day	15% 4 20% 37% 20% 3	519
	21st to end	Day	14% 9% 24% 31% 18% 4	583
September	1st to 10th	Day	16% 8% 28% 27% 17% 4	530
	11th to 20th	Day	17% 7% 25% 33% 13% 4	530
	21st to end	Day	18% 7% 28% 29% 14% 4	530
October	1st to 10th	Day	18% 9% 32% 26% 13% 3	502
	11th to 20th	Day	26% 11% 28% 20% 14% 2	420
	21st to end	Day	30% 13% 25% 24% 6% 1	462
November	1st to 10th	Day	24% 18% 31% 21% 6% 1	425
	11th to 20th	Day	27% 13% 32% 18% 10% 1	430
	21st to end	Day	33% 15% 28% 18% 5%	247
December	1st to 10th	Day	25% 15% 33% 19% 6% 1	220
	11th to 20th	Day	25% 19% 34% 15% 5% 2	220
	21st to end	Day	26% 20% 29% 19% 6%	242
January	1st to 10th	Night	22% 16% 33% 23% 5% 1	929
	11th to 20th	Night	21% 15% 38% 21% 5%	840
	21st to end	Night	14% 14% 38% 27% 6% 1	924
February	1st to 10th	Night	16% 15% 37% 24% 7% 1	840
	11th to 20th	Night	21% 18% 35% 20% 6%	823
	21st to end	Night	20% 13% 35% 24% 7% 1	692
March	1st to 10th	Night	20% 13% 34% 28% 5% 1	840
	11th to 20th	Night	22% 15% 32% 21% 9% 1	829
	21st to end	Night	22% 12% 31% 27% 7% 1	880
April	1st to 10th	Night	28% 11% 28% 24% 8% 1	800
	11th to 20th	Night	24% 8% 32% 25% 10% 1	607
	21st to end	Night	29% 10% 26% 25% 9% 2	600
May	1st to 10th	Night	26% 6% 25% 30% 12% 1	594
	11th to 20th	Night	24% 5% 24% 31% 13% 1	394
	21st to end	Night	21% 5% 30% 30% 11% 2	433
June	1st to 10th	Night	23% 4 19% 39% 13% 3	400
	11th to 20th	Night	19% 4 18% 35% 22% 2	400
	21st to end	Night	26% 7% 18% 32% 16% 1	400
July	1st to 10th	Night	18% 3 21% 40% 17% 2	390
	11th to 20th	Night	13% 2 16% 47% 20% 1	388
	21st to end	Night	16% 3 17% 41% 20% 3	438
August	1st to 10th	Night	16% 3 15% 37% 28% 2	424
	11th to 20th	Night	18% 4 15% 37% 23% 2	592
	21st to end	Night	15% 4 18% 37% 22% 4	660
September	1st to 10th	Night	16% 5% 23% 37% 16% 3	791
	11th to 20th	Night	22% 3 22% 32% 17% 4	800
	21st to end	Night	21% 4 24% 33% 16% 2	800
October	1st to 10th	Night	21% 6% 26% 32% 12% 3	800
	11th to 20th	Night	27% 8% 23% 28% 13% 1	800
	21st to end	Night	28% 10% 26% 27% 8%	880
November	1st to 10th	Night	24% 14% 29% 25% 8%	820
	11th to 20th	Night	27% 14% 31% 20% 8% 1	931
	21st to end	Night	27% 15% 27% 24% 6% 1	950
December	1st to 10th	Night	23% 17% 33% 21% 6% 1	950
	11th to 20th	Night	24% 19% 31% 19% 6%	950
	21st to end	Night	23% 17% 33% 21% 5% 1	1045

Page generated at 2026-03-15 02:23:55. Version ac07

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