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 2025-02-25.

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% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	108659
	Night	17% 11% 4 9% 5% 4 4 3 5% 6% 30%	110011
Transparency	Day	49% 8% 14% 20% 9% 1	112151
	Night	53% 7% 12% 18% 10% 1	114682
Seeing	Day	20% 10% 28% 26% 13% 4	14843
	Night	22% 8% 29% 30% 10% 1	23931

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% 21% 6% 11% 5% 4 3 2 3 3 25%	3597
	11th to 20th	Day	13% 16% 6% 11% 6% 6% 5% 3 4 6% 26%	3570
	21st to end	Day	11% 15% 4 11% 5% 5% 6% 4 5% 6% 28%	3960
February	1st to 10th	Day	15% 17% 4 9% 6% 5% 5% 4 4 4 28%	1720
	11th to 20th	Day	15% 12% 5% 12% 6% 5% 3 3 5% 6% 27%	1872
	21st to end	Day	17% 15% 3 9% 5% 4 4 4 5% 6% 27%	1610
March	1st to 10th	Day	18% 11% 4 10% 6% 5% 5% 3 4 5% 28%	3116
	11th to 20th	Day	13% 16% 5% 11% 6% 5% 4 3 4 5% 27%	3268
	21st to end	Day	14% 9% 3 9% 4 5% 5% 3 5% 6% 37%	4166
April	1st to 10th	Day	21% 10% 4 8% 5% 4 5% 3 5% 5% 31%	2280
	11th to 20th	Day	21% 8% 3 7% 4 4 3 4 4 6% 37%	2254
	21st to end	Day	22% 9% 3 8% 5% 4 5% 3 4 5% 32%	2461
May	1st to 10th	Day	20% 8% 3 8% 5% 4 4 4 5% 7% 32%	4345
	11th to 20th	Day	16% 8% 3 8% 5% 5% 5% 4 6% 9% 32%	4398
	21st to end	Day	15% 6% 2 6% 5% 5% 5% 4 7% 8% 36%	4837
June	1st to 10th	Day	20% 8% 2 7% 5% 4 4 4 6% 7% 31%	2660
	11th to 20th	Day	14% 5% 3 6% 4 5% 5% 5% 6% 9% 38%	2660
	21st to end	Day	20% 9% 2 7% 5% 4 4 4 7% 8% 29%	2660
July	1st to 10th	Day	12% 6% 2 6% 6% 6% 5% 4 7% 9% 35%	4440
	11th to 20th	Day	13% 5% 2 7% 5% 5% 5% 5% 7% 9% 37%	4440
	21st to end	Day	11% 6% 2 5% 4 4 5% 4 6% 8% 44%	4814
August	1st to 10th	Day	14% 6% 2 8% 5% 6% 6% 5% 8% 9% 32%	4423
	11th to 20th	Day	15% 6% 2 7% 5% 5% 5% 4 6% 9% 36%	4035
	21st to end	Day	17% 5% 3 7% 4 4 5% 4 6% 8% 39%	4180
September	1st to 10th	Day	12% 4 2 6% 6% 5% 5% 4 7% 8% 42%	2280
	11th to 20th	Day	14% 6% 2 5% 3 4 3 3 6% 8% 47%	2181
	21st to end	Day	17% 5% 2 6% 4 4 5% 3 6% 6% 41%	2090
October	1st to 10th	Day	20% 6% 2 7% 5% 4 5% 4 5% 7% 35%	1986
	11th to 20th	Day	19% 8% 3 7% 5% 6% 6% 4 5% 7% 30%	1833
	21st to end	Day	24% 10% 3 7% 5% 4 4 3 5% 5% 32%	1881
November	1st to 10th	Day	16% 10% 3 7% 6% 4 5% 4 5% 6% 34%	1761
	11th to 20th	Day	18% 11% 3 8% 4 4 4 3 6% 7% 31%	1735
	21st to end	Day	22% 12% 3 7% 5% 5% 5% 3 4 5% 27%	1600
December	1st to 10th	Day	20% 18% 4 11% 6% 5% 4 3 4 5% 21%	2600
	11th to 20th	Day	19% 13% 5% 9% 5% 4 4 3 6% 5% 27%	2986
	21st to end	Day	24% 12% 4 9% 5% 5% 5% 4 6% 4 20%	3960
January	1st to 10th	Night	15% 19% 8% 14% 5% 4 4 3 4 4 20%	6349
	11th to 20th	Night	10% 16% 6% 17% 8% 6% 5% 4 5% 5% 20%	6315
	21st to end	Night	13% 14% 5% 12% 7% 5% 5% 4 5% 6% 24%	6996
February	1st to 10th	Night	14% 15% 5% 12% 7% 5% 4 4 5% 5% 24%	2679
	11th to 20th	Night	14% 12% 5% 10% 6% 6% 5% 3 5% 5% 28%	2412
	21st to end	Night	15% 13% 4 9% 7% 4 3 3 5% 6% 30%	1939
March	1st to 10th	Night	21% 12% 4 8% 4 3 4 4 3 4 32%	3724
	11th to 20th	Night	18% 17% 5% 9% 5% 5% 4 3 4 4 28%	3686
	21st to end	Night	13% 10% 5% 9% 5% 5% 4 3 5% 5% 36%	3466
April	1st to 10th	Night	23% 11% 3 7% 4 4 4 4 5% 6% 30%	1900
	11th to 20th	Night	21% 8% 2 7% 5% 4 4 3 5% 5% 35%	1875
	21st to end	Night	22% 9% 3 7% 4 4 3 3 4 6% 35%	1718
May	1st to 10th	Night	22% 9% 3 7% 5% 4 5% 3 5% 6% 29%	2624
	11th to 20th	Night	20% 9% 3 6% 5% 4 4 4 5% 6% 34%	2495
	21st to end	Night	16% 7% 3 7% 5% 4 4 3 6% 9% 36%	2738
June	1st to 10th	Night	21% 6% 3 6% 4 4 4 4 7% 8% 33%	1520
	11th to 20th	Night	16% 7% 2 8% 4 4 5% 4 6% 8% 37%	1520
	21st to end	Night	19% 7% 2 7% 6% 5% 5% 4 6% 7% 32%	1520
July	1st to 10th	Night	13% 7% 3 8% 6% 5% 6% 4 7% 8% 34%	2520
	11th to 20th	Night	15% 6% 2 6% 4 4 5% 5% 6% 7% 40%	2520
	21st to end	Night	12% 5% 2 6% 5% 5% 5% 4 7% 7% 43%	2739
August	1st to 10th	Night	15% 8% 3 9% 5% 4 4 4 6% 6% 35%	2506
	11th to 20th	Night	16% 7% 3 8% 4 5% 5% 4 5% 7% 37%	2747
	21st to end	Night	18% 6% 3 7% 5% 4 4 3 4 7% 38%	3476
September	1st to 10th	Night	13% 5% 2 7% 3 4 5% 4 5% 7% 45%	1900
	11th to 20th	Night	14% 6% 2 6% 4 3 4 3 4 6% 49%	1998
	21st to end	Night	16% 6% 2 5% 4 5% 4 4 5% 7% 43%	2090
October	1st to 10th	Night	19% 5% 3 7% 4 4 4 3 5% 6% 40%	2190
	11th to 20th	Night	20% 9% 4 7% 4 4 4 3 4 5% 35%	2346
	21st to end	Night	23% 9% 3 7% 5% 5% 4 3 4 6% 31%	2717
November	1st to 10th	Night	19% 9% 3 7% 5% 5% 4 4 5% 5% 33%	2537
	11th to 20th	Night	19% 10% 4 8% 5% 5% 4 4 5% 5% 33%	2665
	21st to end	Night	24% 15% 3 8% 4 4 4 3 4 5% 27%	2800
December	1st to 10th	Night	18% 16% 6% 12% 7% 6% 5% 3 5% 5% 18%	4580
	11th to 20th	Night	24% 12% 4 8% 5% 4 4 3 5% 5% 26%	5208
	21st to end	Night	24% 15% 4 9% 4 3 5% 4 5% 6% 21%	6996

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	63% 7% 10% 17% 3	3598
	11th to 20th	Day	60% 7% 10% 15% 7% 1	3600
	21st to end	Day	55% 7% 11% 15% 11% 1	3960
February	1st to 10th	Day	59% 5% 9% 18% 7% 2	1720
	11th to 20th	Day	56% 8% 12% 14% 9% 1	1881
	21st to end	Day	58% 6% 10% 17% 9% 2	1610
March	1st to 10th	Day	56% 9% 9% 18% 7% 1	3119
	11th to 20th	Day	56% 8% 13% 11% 10% 3	3268
	21st to end	Day	45% 8% 11% 20% 15% 2	4166
April	1st to 10th	Day	55% 5% 9% 18% 10% 2	2280
	11th to 20th	Day	48% 6% 10% 22% 13% 1	2254
	21st to end	Day	53% 7% 10% 16% 11% 3	2461
May	1st to 10th	Day	48% 9% 12% 21% 9% 1	4359
	11th to 20th	Day	45% 12% 17% 16% 9% 1	4402
	21st to end	Day	41% 9% 13% 21% 13% 1	4837
June	1st to 10th	Day	50% 8% 12% 19% 10% 2	2660
	11th to 20th	Day	41% 8% 14% 22% 12% 2	2660
	21st to end	Day	51% 8% 13% 18% 9% 1	2660
July	1st to 10th	Day	42% 8% 15% 25% 9%	4370
	11th to 20th	Day	40% 9% 18% 27% 7%	4365
	21st to end	Day	36% 8% 15% 31% 9%	4661
August	1st to 10th	Day	45% 9% 18% 21% 7%	4409
	11th to 20th	Day	42% 9% 21% 22% 6%	4076
	21st to end	Day	42% 7% 16% 20% 14% 1	4180
September	1st to 10th	Day	37% 9% 15% 27% 11% 1	2280
	11th to 20th	Day	35% 7% 15% 30% 13% 1	2181
	21st to end	Day	42% 8% 15% 25% 11%	2090
October	1st to 10th	Day	44% 6% 17% 26% 7%	3298
	11th to 20th	Day	45% 7% 18% 23% 6%	3023
	21st to end	Day	43% 5% 21% 22% 8% 1	3081
November	1st to 10th	Day	49% 7% 13% 22% 8% 1	1761
	11th to 20th	Day	51% 8% 12% 18% 11%	1735
	21st to end	Day	58% 8% 14% 15% 6%	1600
December	1st to 10th	Day	67% 5% 9% 15% 4	2600
	11th to 20th	Day	57% 5% 10% 17% 10%	2986
	21st to end	Day	64% 7% 11% 12% 6%	3960
January	1st to 10th	Night	66% 7% 11% 11% 4	6349
	11th to 20th	Night	64% 8% 11% 13% 4	6360
	21st to end	Night	59% 6% 10% 11% 13%	6996
February	1st to 10th	Night	61% 6% 9% 15% 8% 1	2679
	11th to 20th	Night	58% 6% 10% 17% 9% 1	2414
	21st to end	Night	56% 5% 9% 16% 12% 2	1939
March	1st to 10th	Night	53% 7% 11% 17% 8% 3	3734
	11th to 20th	Night	58% 7% 9% 12% 12% 2	3687
	21st to end	Night	48% 7% 8% 22% 12% 3	3466
April	1st to 10th	Night	54% 5% 9% 17% 13% 2	1900
	11th to 20th	Night	50% 6% 8% 19% 14% 2	1875
	21st to end	Night	51% 4 9% 18% 14% 3	1718
May	1st to 10th	Night	52% 9% 12% 17% 8% 3	2630
	11th to 20th	Night	46% 11% 14% 17% 10% 2	2496
	21st to end	Night	44% 7% 11% 19% 16% 2	2739
June	1st to 10th	Night	47% 8% 12% 20% 12% 1	1520
	11th to 20th	Night	44% 8% 11% 20% 13% 4	1520
	21st to end	Night	48% 9% 10% 18% 13% 1	1520
July	1st to 10th	Night	45% 8% 17% 19% 11% 1	2480
	11th to 20th	Night	39% 8% 19% 25% 9%	2472
	21st to end	Night	37% 8% 21% 23% 12%	2651
August	1st to 10th	Night	47% 8% 13% 24% 8%	2496
	11th to 20th	Night	45% 8% 18% 22% 8%	2771
	21st to end	Night	45% 7% 13% 21% 13% 1	3476
September	1st to 10th	Night	37% 8% 15% 24% 14% 1	1900
	11th to 20th	Night	36% 5% 16% 31% 12% 1	1998
	21st to end	Night	40% 8% 10% 27% 15%	2090
October	1st to 10th	Night	45% 7% 14% 24% 10%	3658
	11th to 20th	Night	44% 5% 13% 29% 8%	3895
	21st to end	Night	47% 5% 16% 18% 12% 2	4467
November	1st to 10th	Night	52% 6% 13% 20% 8% 1	2537
	11th to 20th	Night	52% 6% 12% 17% 10% 1	2665
	21st to end	Night	59% 6% 12% 17% 6%	2800
December	1st to 10th	Night	69% 5% 12% 11% 4	4580
	11th to 20th	Night	60% 6% 9% 15% 11% 1	5208
	21st to end	Night	63% 5% 9% 14% 9%	6996

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% 14% 28% 22% 10%	200
	11th to 20th	Day	25% 14% 32% 22% 7% 1	200
	21st to end	Day	15% 14% 33% 29% 9% 1	220
February	1st to 10th	Day	28% 15% 33% 20% 3	260
	11th to 20th	Day	22% 12% 36% 25% 5%	420
	21st to end	Day	24% 10% 33% 28% 5%	398
March	1st to 10th	Day	21% 9% 30% 31% 9%	460
	11th to 20th	Day	18% 14% 34% 25% 7% 1	460
	21st to end	Day	26% 8% 31% 23% 10% 2	506
April	1st to 10th	Day	26% 13% 28% 23% 9% 2	460
	11th to 20th	Day	25% 16% 27% 20% 9% 3	452
	21st to end	Day	26% 11% 30% 21% 9% 2	460
May	1st to 10th	Day	23% 9% 32% 23% 10% 2	463
	11th to 20th	Day	16% 10% 29% 26% 16% 4	487
	21st to end	Day	18% 10% 33% 25% 12% 2	529
June	1st to 10th	Day	21% 11% 26% 29% 10% 3	490
	11th to 20th	Day	14% 11% 26% 31% 16% 3	490
	21st to end	Day	22% 11% 23% 27% 13% 4	490
July	1st to 10th	Day	14% 6% 24% 31% 21% 6%	485
	11th to 20th	Day	14% 6% 24% 37% 16% 4	484
	21st to end	Day	14% 5% 22% 34% 21% 4	532
August	1st to 10th	Day	16% 5% 20% 32% 21% 6%	486
	11th to 20th	Day	12% 4 21% 32% 21% 10%	479
	21st to end	Day	15% 7% 24% 23% 20% 11%	539
September	1st to 10th	Day	11% 8% 27% 30% 17% 7%	490
	11th to 20th	Day	15% 5% 19% 28% 20% 12%	490
	21st to end	Day	18% 8% 23% 26% 19% 7%	490
October	1st to 10th	Day	19% 10% 27% 23% 15% 5%	490
	11th to 20th	Day	22% 11% 29% 23% 12% 3	454
	21st to end	Day	29% 9% 28% 25% 9%	429
November	1st to 10th	Day	24% 13% 30% 25% 8% 1	395
	11th to 20th	Day	24% 13% 32% 21% 9% 1	335
	21st to end	Day	32% 11% 30% 19% 9%	200
December	1st to 10th	Day	29% 11% 24% 22% 11% 4	200
	11th to 20th	Day	25% 15% 36% 21% 4 1	200
	21st to end	Day	32% 14% 27% 19% 6% 3	220
January	1st to 10th	Night	26% 9% 32% 27% 6%	800
	11th to 20th	Night	25% 9% 34% 25% 7%	800
	21st to end	Night	19% 7% 32% 34% 7% 1	880
February	1st to 10th	Night	22% 8% 38% 27% 5% 1	800
	11th to 20th	Night	19% 9% 39% 26% 5% 1	783
	21st to end	Night	22% 8% 33% 32% 5%	647
March	1st to 10th	Night	25% 9% 30% 31% 6%	760
	11th to 20th	Night	25% 10% 31% 28% 7%	760
	21st to end	Night	21% 7% 35% 28% 8%	836
April	1st to 10th	Night	28% 9% 27% 29% 6%	760
	11th to 20th	Night	24% 12% 31% 26% 6% 1	751
	21st to end	Night	27% 11% 30% 24% 8%	578
May	1st to 10th	Night	26% 8% 31% 28% 7% 1	451
	11th to 20th	Night	22% 6% 29% 34% 8% 1	374
	21st to end	Night	18% 7% 38% 29% 8%	411
June	1st to 10th	Night	21% 7% 27% 36% 8% 1	380
	11th to 20th	Night	19% 3 28% 36% 13% 1	380
	21st to end	Night	20% 5% 27% 34% 14% 1	380
July	1st to 10th	Night	11% 4 28% 42% 15% 1	370
	11th to 20th	Night	12% 3 23% 47% 14% 1	368
	21st to end	Night	14% 3 21% 45% 15% 1	416
August	1st to 10th	Night	15% 4 16% 42% 21% 2	378
	11th to 20th	Night	14% 3 17% 42% 22% 2	536
	21st to end	Night	18% 4 20% 35% 21% 2	836
September	1st to 10th	Night	16% 3 25% 40% 16% 1	760
	11th to 20th	Night	17% 6% 18% 36% 21% 2	760
	21st to end	Night	18% 6% 25% 33% 15% 3	760
October	1st to 10th	Night	21% 5% 29% 31% 12% 1	760
	11th to 20th	Night	24% 9% 28% 29% 10%	760
	21st to end	Night	27% 9% 31% 28% 6%	836
November	1st to 10th	Night	24% 11% 31% 26% 8% 1	780
	11th to 20th	Night	23% 10% 34% 24% 9% 1	800
	21st to end	Night	30% 10% 31% 23% 7%	800
December	1st to 10th	Night	29% 10% 29% 25% 8%	800
	11th to 20th	Night	27% 11% 32% 24% 6% 1	800
	21st to end	Night	33% 10% 28% 22% 7%	880

Page generated at 2025-02-22 06:51:35. Version ac07

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