Contrecoeur
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Contrecoeur clear sky chart from 2005-11-06 to 2026-07-01.

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% 9% 3 8% 5% 5% 5% 4 5% 7% 32%	138025
	Night	17% 11% 4 9% 5% 5% 4 4 5% 6% 30%	134351
Transparency	Day	49% 7% 13% 20% 9% 1	141471
	Night	53% 6% 11% 18% 10% 1	138993
Seeing	Day	20% 10% 28% 26% 12% 3	16606
	Night	22% 8% 30% 30% 9% 1	25543

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	15% 18% 6% 12% 5% 4 3 3 3 5% 27%	4661
	11th to 20th	Day	13% 16% 6% 11% 6% 6% 5% 3 4 6% 24%	4650
	21st to end	Day	9% 13% 4 12% 7% 7% 7% 4 5% 6% 26%	5124
February	1st to 10th	Day	14% 16% 3 10% 6% 5% 5% 4 4 4 29%	1806
	11th to 20th	Day	14% 12% 4 12% 6% 5% 3 3 5% 7% 28%	1968
	21st to end	Day	16% 15% 4 9% 6% 4 4 3 5% 6% 28%	1730
March	1st to 10th	Day	18% 12% 5% 10% 6% 5% 5% 3 5% 6% 26%	4576
	11th to 20th	Day	12% 13% 4 10% 5% 5% 4 3 5% 7% 32%	4773
	21st to end	Day	18% 10% 4 10% 5% 4 4 3 4 5% 33%	6102
April	1st to 10th	Day	21% 10% 4 8% 5% 4 5% 3 5% 5% 31%	2520
	11th to 20th	Day	22% 8% 3 7% 4 4 3 4 4 5% 36%	2494
	21st to end	Day	21% 8% 3 8% 5% 4 5% 3 4 6% 33%	2721
May	1st to 10th	Day	24% 9% 3 8% 5% 4 5% 4 5% 7% 26%	8072
	11th to 20th	Day	19% 7% 3 8% 5% 5% 5% 4 6% 9% 31%	8221
	21st to end	Day	20% 8% 3 6% 5% 5% 4 4 6% 7% 33%	9060
June	1st to 10th	Day	20% 8% 2 6% 5% 4 4 4 6% 7% 32%	2940
	11th to 20th	Day	15% 6% 3 6% 4 5% 5% 5% 6% 9% 38%	2940
	21st to end	Day	19% 8% 3 7% 5% 5% 4 4 7% 9% 29%	2940
July	1st to 10th	Day	14% 6% 3 7% 6% 6% 6% 4 7% 9% 33%	6360
	11th to 20th	Day	11% 5% 2 7% 4 5% 5% 4 7% 9% 40%	6360
	21st to end	Day	10% 6% 2 5% 4 4 5% 4 6% 10% 46%	6926
August	1st to 10th	Day	13% 6% 2 8% 5% 6% 6% 5% 8% 9% 33%	4563
	11th to 20th	Day	15% 6% 2 7% 5% 4 5% 4 6% 9% 37%	4165
	21st to end	Day	17% 5% 3 7% 4 4 5% 4 6% 8% 39%	4312
September	1st to 10th	Day	11% 4 2 6% 6% 5% 5% 4 7% 8% 43%	2400
	11th to 20th	Day	13% 5% 2 5% 3 4 3 3 6% 8% 48%	2296
	21st to end	Day	17% 5% 2 6% 4 4 5% 3 6% 6% 41%	2200
October	1st to 10th	Day	19% 6% 2 7% 5% 3 5% 3 5% 7% 37%	2090
	11th to 20th	Day	18% 8% 3 8% 5% 5% 6% 4 5% 7% 31%	1929
	21st to end	Day	24% 10% 3 7% 5% 4 4 3 5% 6% 31%	1980
November	1st to 10th	Day	17% 11% 3 8% 6% 4 4 4 5% 6% 33%	1851
	11th to 20th	Day	17% 12% 3 8% 5% 4 4 3 6% 7% 31%	1821
	21st to end	Day	23% 13% 3 7% 5% 5% 5% 3 4 5% 27%	1680
December	1st to 10th	Day	20% 18% 4 11% 6% 5% 4 3 4 5% 21%	2680
	11th to 20th	Day	18% 13% 5% 9% 5% 4 4 3 6% 6% 27%	3066
	21st to end	Day	24% 12% 4 10% 5% 5% 5% 4 6% 4 20%	4048
January	1st to 10th	Night	14% 17% 7% 14% 5% 5% 4 3 4 4 22%	8234
	11th to 20th	Night	12% 17% 6% 17% 8% 5% 5% 4 4 4 18%	8235
	21st to end	Night	10% 13% 5% 13% 9% 6% 5% 4 5% 6% 24%	9057
February	1st to 10th	Night	13% 15% 5% 12% 7% 5% 4 4 5% 5% 24%	2813
	11th to 20th	Night	14% 12% 5% 10% 7% 6% 5% 3 5% 5% 28%	2536
	21st to end	Night	15% 13% 5% 9% 7% 4 3 3 5% 6% 30%	2076
March	1st to 10th	Night	22% 13% 4 9% 5% 4 4 3 3 4 29%	5484
	11th to 20th	Night	15% 13% 4 8% 5% 5% 5% 4 6% 6% 30%	5401
	21st to end	Night	16% 12% 5% 10% 6% 5% 5% 3 5% 5% 31%	5072
April	1st to 10th	Night	23% 11% 3 7% 4 4 3 4 5% 6% 31%	2100
	11th to 20th	Night	21% 9% 3 8% 5% 4 4 3 5% 5% 34%	2075
	21st to end	Night	22% 9% 2 7% 4 4 3 3 4 5% 35%	1898
May	1st to 10th	Night	23% 9% 3 9% 5% 5% 5% 4 5% 7% 25%	4882
	11th to 20th	Night	20% 9% 3 8% 6% 4 5% 4 5% 6% 31%	4639
	21st to end	Night	19% 9% 3 7% 5% 4 4 4 6% 8% 32%	5114
June	1st to 10th	Night	21% 6% 3 6% 4 4 4 3 7% 7% 34%	1680
	11th to 20th	Night	16% 8% 2 8% 4 4 5% 4 6% 8% 36%	1680
	21st to end	Night	18% 6% 2 7% 6% 5% 5% 4 6% 7% 33%	1680
July	1st to 10th	Night	13% 6% 3 8% 5% 5% 6% 4 8% 9% 33%	3600
	11th to 20th	Night	15% 6% 2 6% 5% 4 5% 4 6% 7% 40%	3600
	21st to end	Night	10% 5% 2 6% 5% 5% 5% 4 7% 8% 43%	3926
August	1st to 10th	Night	14% 8% 3 9% 5% 4 4 4 6% 6% 37%	2586
	11th to 20th	Night	16% 7% 3 8% 4 4 4 4 5% 7% 38%	2836
	21st to end	Night	18% 6% 3 7% 5% 4 4 3 4 7% 38%	3586
September	1st to 10th	Night	12% 5% 2 6% 3 4 5% 4 5% 7% 46%	2000
	11th to 20th	Night	14% 6% 2 6% 3 3 4 3 4 6% 50%	2103
	21st to end	Night	16% 6% 2 5% 4 5% 4 4 5% 7% 43%	2200
October	1st to 10th	Night	18% 5% 2 7% 4 4 4 3 5% 6% 42%	2305
	11th to 20th	Night	19% 9% 4 7% 4 4 4 3 4 6% 36%	2470
	21st to end	Night	23% 8% 3 7% 5% 5% 5% 3 4 6% 31%	2860
November	1st to 10th	Night	20% 9% 3 7% 5% 5% 4 3 5% 5% 33%	2667
	11th to 20th	Night	19% 10% 4 8% 5% 5% 4 4 5% 5% 32%	2798
	21st to end	Night	23% 15% 3 8% 4 4 4 3 4 5% 27%	2940
December	1st to 10th	Night	18% 16% 6% 11% 7% 6% 5% 3 5% 5% 18%	4720
	11th to 20th	Night	23% 12% 4 9% 5% 4 4 3 5% 5% 26%	5348
	21st to end	Night	24% 15% 4 9% 4 3 5% 4 5% 6% 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	61% 6% 11% 17% 5%	4662
	11th to 20th	Day	62% 6% 9% 14% 9% 1	4680
	21st to end	Day	57% 6% 10% 15% 11% 1	5124
February	1st to 10th	Day	58% 5% 9% 19% 7% 2	1806
	11th to 20th	Day	55% 8% 11% 15% 9% 1	1977
	21st to end	Day	57% 5% 9% 17% 9% 2	1730
March	1st to 10th	Day	58% 7% 8% 14% 9% 3	4579
	11th to 20th	Day	50% 8% 17% 13% 11% 2	4773
	21st to end	Day	52% 6% 9% 17% 15% 2	6102
April	1st to 10th	Day	55% 5% 9% 18% 11% 2	2520
	11th to 20th	Day	49% 6% 10% 21% 13% 1	2494
	21st to end	Day	52% 7% 10% 17% 11% 3	2721
May	1st to 10th	Day	56% 8% 9% 19% 8% 1	8084
	11th to 20th	Day	48% 9% 16% 19% 8% 1	8225
	21st to end	Day	48% 7% 12% 22% 10% 1	9061
June	1st to 10th	Day	49% 7% 11% 20% 10% 2	2940
	11th to 20th	Day	41% 8% 13% 23% 12% 2	2940
	21st to end	Day	50% 8% 13% 19% 9% 1	2940
July	1st to 10th	Day	45% 8% 15% 25% 7%	6290
	11th to 20th	Day	38% 8% 16% 29% 9%	6285
	21st to end	Day	34% 7% 16% 35% 9%	6728
August	1st to 10th	Day	44% 9% 19% 22% 7%	4549
	11th to 20th	Day	42% 9% 21% 22% 7%	4206
	21st to end	Day	42% 7% 16% 21% 13% 1	4312
September	1st to 10th	Day	36% 9% 16% 29% 10% 1	2400
	11th to 20th	Day	34% 7% 15% 31% 13% 1	2296
	21st to end	Day	41% 7% 15% 25% 11%	2200
October	1st to 10th	Day	43% 6% 17% 26% 8%	3402
	11th to 20th	Day	44% 7% 18% 24% 6%	3119
	21st to end	Day	44% 5% 21% 22% 8% 1	3180
November	1st to 10th	Day	50% 7% 12% 21% 8% 1	1851
	11th to 20th	Day	52% 7% 12% 18% 11%	1821
	21st to end	Day	58% 7% 13% 15% 6%	1680
December	1st to 10th	Day	66% 5% 9% 15% 4	2680
	11th to 20th	Day	57% 5% 10% 17% 10%	3066
	21st to end	Day	64% 7% 11% 12% 6%	4048
January	1st to 10th	Night	64% 7% 11% 13% 5% 1	8234
	11th to 20th	Night	67% 7% 9% 12% 5%	8280
	21st to end	Night	59% 6% 9% 13% 13%	9057
February	1st to 10th	Night	61% 6% 9% 16% 8% 1	2813
	11th to 20th	Night	57% 6% 10% 17% 9% 1	2538
	21st to end	Night	55% 5% 9% 18% 12% 1	2076
March	1st to 10th	Night	58% 5% 9% 13% 11% 4	5494
	11th to 20th	Night	51% 6% 14% 15% 12% 2	5402
	21st to end	Night	54% 6% 7% 21% 10% 2	5072
April	1st to 10th	Night	54% 5% 9% 18% 13% 2	2100
	11th to 20th	Night	51% 6% 8% 19% 14% 2	2075
	21st to end	Night	51% 4 8% 18% 15% 3	1898
May	1st to 10th	Night	56% 7% 12% 16% 7% 1	4888
	11th to 20th	Night	50% 8% 11% 21% 9% 1	4640
	21st to end	Night	49% 6% 10% 18% 15% 1	5115
June	1st to 10th	Night	47% 7% 11% 20% 14% 1	1680
	11th to 20th	Night	44% 8% 11% 20% 13% 3	1680
	21st to end	Night	48% 9% 11% 19% 13% 1	1680
July	1st to 10th	Night	44% 7% 20% 21% 8%	3560
	11th to 20th	Night	40% 8% 17% 26% 9%	3552
	21st to end	Night	36% 8% 19% 26% 11%	3809
August	1st to 10th	Night	46% 8% 13% 25% 8%	2576
	11th to 20th	Night	44% 7% 18% 23% 8%	2860
	21st to end	Night	45% 7% 13% 21% 13% 1	3586
September	1st to 10th	Night	37% 8% 15% 26% 14% 1	2000
	11th to 20th	Night	35% 5% 15% 32% 12% 1	2103
	21st to end	Night	40% 8% 10% 27% 15%	2200
October	1st to 10th	Night	44% 7% 14% 24% 11%	3773
	11th to 20th	Night	44% 5% 13% 29% 8%	4019
	21st to end	Night	47% 5% 16% 19% 12% 2	4610
November	1st to 10th	Night	52% 6% 12% 21% 7% 1	2667
	11th to 20th	Night	53% 6% 12% 18% 10% 1	2798
	21st to end	Night	60% 6% 12% 16% 6%	2940
December	1st to 10th	Night	69% 5% 12% 11% 4	4720
	11th to 20th	Night	60% 6% 9% 15% 10% 1	5348
	21st to end	Night	63% 5% 9% 14% 9%	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	26% 13% 28% 22% 10%	220
	11th to 20th	Day	26% 16% 31% 20% 6%	220
	21st to end	Day	14% 15% 31% 29% 9% 2	242
February	1st to 10th	Day	26% 13% 34% 22% 5%	286
	11th to 20th	Day	21% 12% 34% 27% 6%	456
	21st to end	Day	24% 11% 35% 26% 4	446
March	1st to 10th	Day	20% 11% 33% 28% 8%	540
	11th to 20th	Day	20% 15% 33% 25% 6% 1	540
	21st to end	Day	27% 10% 31% 23% 8% 1	594
April	1st to 10th	Day	26% 14% 29% 21% 8% 1	540
	11th to 20th	Day	26% 17% 26% 20% 8% 2	532
	21st to end	Day	25% 12% 32% 20% 9% 2	540
May	1st to 10th	Day	25% 10% 30% 24% 9% 2	543
	11th to 20th	Day	17% 11% 29% 25% 15% 3	567
	21st to end	Day	19% 10% 34% 24% 11% 2	617
June	1st to 10th	Day	21% 10% 27% 29% 10% 3	570
	11th to 20th	Day	15% 12% 27% 29% 14% 3	570
	21st to end	Day	20% 10% 25% 27% 15% 4	570
July	1st to 10th	Day	14% 6% 25% 30% 20% 6%	525
	11th to 20th	Day	13% 5% 26% 37% 15% 4	524
	21st to end	Day	13% 6% 24% 34% 20% 3	576
August	1st to 10th	Day	15% 4 20% 33% 21% 7%	526
	11th to 20th	Day	12% 4 21% 32% 21% 10%	519
	21st to end	Day	14% 8% 25% 22% 20% 10%	583
September	1st to 10th	Day	11% 9% 27% 29% 17% 8%	530
	11th to 20th	Day	14% 5% 18% 29% 22% 12%	530
	21st to end	Day	18% 8% 23% 26% 18% 6%	530
October	1st to 10th	Day	18% 10% 28% 24% 15% 5%	530
	11th to 20th	Day	22% 11% 30% 23% 12% 3	490
	21st to end	Day	30% 9% 27% 25% 9%	462
November	1st to 10th	Day	24% 15% 30% 23% 8%	425
	11th to 20th	Day	24% 13% 31% 21% 10% 2	361
	21st to end	Day	33% 11% 31% 17% 8%	220
December	1st to 10th	Day	28% 11% 26% 21% 11% 3	220
	11th to 20th	Day	24% 14% 36% 21% 3 1	220
	21st to end	Day	31% 15% 28% 19% 6% 2	242
January	1st to 10th	Night	25% 9% 32% 28% 5%	840
	11th to 20th	Night	26% 10% 34% 24% 7%	840
	21st to end	Night	18% 8% 32% 33% 7% 1	924
February	1st to 10th	Night	21% 8% 36% 28% 6% 1	840
	11th to 20th	Night	19% 9% 39% 27% 5% 1	823
	21st to end	Night	22% 8% 34% 32% 5%	692
March	1st to 10th	Night	24% 9% 32% 29% 5%	840
	11th to 20th	Night	25% 11% 31% 27% 6%	840
	21st to end	Night	22% 9% 34% 28% 7%	924
April	1st to 10th	Night	29% 11% 28% 27% 6%	840
	11th to 20th	Night	25% 12% 31% 26% 6% 1	831
	21st to end	Night	27% 11% 30% 24% 8%	638
May	1st to 10th	Night	26% 8% 31% 28% 6% 1	499
	11th to 20th	Night	22% 7% 29% 34% 8% 1	414
	21st to end	Night	19% 7% 37% 28% 8%	455
June	1st to 10th	Night	21% 6% 28% 37% 8% 1	420
	11th to 20th	Night	19% 5% 28% 35% 12%	420
	21st to end	Night	19% 5% 26% 35% 14%	420
July	1st to 10th	Night	11% 4 28% 42% 14% 1	390
	11th to 20th	Night	12% 4 24% 46% 14% 1	388
	21st to end	Night	14% 3 22% 46% 15% 1	438
August	1st to 10th	Night	14% 4 16% 43% 22% 2	398
	11th to 20th	Night	13% 3 17% 42% 22% 2	565
	21st to end	Night	18% 4 20% 36% 20% 2	880
September	1st to 10th	Night	15% 4 25% 39% 16% 1	800
	11th to 20th	Night	16% 6% 18% 36% 22% 3	800
	21st to end	Night	18% 6% 26% 33% 15% 2	800
October	1st to 10th	Night	20% 5% 29% 32% 13% 1	800
	11th to 20th	Night	23% 9% 28% 31% 10%	800
	21st to end	Night	26% 9% 31% 28% 5%	880
November	1st to 10th	Night	25% 11% 30% 25% 8% 1	820
	11th to 20th	Night	23% 10% 34% 24% 8% 1	840
	21st to end	Night	29% 10% 31% 23% 7%	840
December	1st to 10th	Night	28% 10% 30% 25% 7%	840
	11th to 20th	Night	27% 11% 33% 23% 6% 1	840
	21st to end	Night	33% 10% 29% 21% 7%	924

Page generated at 2026-06-28 02:10:44. Version ac07

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