Mascouche
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mascouche clear sky chart from 2005-11-06 to 2024-01-16.

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% 8% 4 7% 6% 3 5% 5% 5% 7% 34%	74786
	Night	18% 10% 4 7% 5% 3 4 4 5% 6% 34%	75019
Transparency	Day	49% 6% 12% 20% 11% 1	74491
	Night	52% 6% 11% 20% 11% 1	74848
Seeing	Day	21% 9% 28% 25% 13% 4	13454
	Night	22% 7% 28% 31% 10% 1	22542

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	18% 15% 5% 10% 6% 4 4 4 5% 5% 24%	1517
	11th to 20th	Day	18% 15% 4 8% 7% 3 5% 4 3 4 29%	1480
	21st to end	Day	11% 13% 4 9% 7% 3 5% 5% 5% 6% 31%	1584
February	1st to 10th	Day	15% 16% 4 8% 8% 4 4 4 4 6% 27%	1568
	11th to 20th	Day	13% 13% 5% 9% 7% 4 5% 5% 5% 6% 28%	1666
	21st to end	Day	17% 15% 5% 9% 6% 3 4 4 5% 4 28%	1480
March	1st to 10th	Day	15% 12% 4 8% 8% 5% 6% 4 5% 5% 30%	1797
	11th to 20th	Day	16% 11% 3 7% 6% 4 4 4 4 6% 33%	1858
	21st to end	Day	19% 9% 4 7% 6% 3 4 4 4 5% 36%	2376
April	1st to 10th	Day	21% 10% 4 6% 6% 3 6% 3 4 5% 32%	2160
	11th to 20th	Day	21% 7% 3 5% 6% 3 4 3 3 6% 38%	2134
	21st to end	Day	22% 8% 4 6% 5% 4 4 4 4 6% 32%	2312
May	1st to 10th	Day	20% 7% 3 7% 6% 3 4 4 4 6% 35%	2487
	11th to 20th	Day	19% 6% 3 5% 6% 3 4 5% 5% 6% 37%	2478
	21st to end	Day	17% 6% 4 5% 5% 4 5% 5% 6% 7% 35%	2725
June	1st to 10th	Day	21% 7% 3 5% 6% 4 5% 5% 5% 9% 30%	2520
	11th to 20th	Day	15% 6% 3 6% 5% 3 6% 5% 5% 8% 38%	2520
	21st to end	Day	19% 7% 4 7% 7% 3 6% 6% 5% 7% 29%	2520
July	1st to 10th	Day	12% 4 3 5% 5% 4 6% 5% 7% 8% 40%	2520
	11th to 20th	Day	12% 5% 3 5% 5% 4 6% 7% 7% 9% 37%	2520
	21st to end	Day	11% 5% 3 5% 5% 4 5% 6% 7% 9% 38%	2744
August	1st to 10th	Day	12% 5% 2 7% 7% 4 6% 5% 7% 8% 36%	2506
	11th to 20th	Day	10% 4 2 7% 7% 4 6% 6% 8% 8% 40%	2298
	21st to end	Day	12% 6% 2 5% 5% 3 5% 5% 6% 8% 45%	2376
September	1st to 10th	Day	12% 5% 3 6% 5% 3 5% 6% 6% 8% 42%	2160
	11th to 20th	Day	15% 5% 2 4 4 2 4 4 6% 6% 50%	2082
	21st to end	Day	15% 6% 3 5% 5% 3 5% 3 4 7% 43%	1980
October	1st to 10th	Day	20% 6% 3 6% 4 4 4 4 6% 7% 37%	1863
	11th to 20th	Day	20% 7% 4 7% 6% 4 6% 5% 6% 6% 29%	1754
	21st to end	Day	24% 9% 4 5% 6% 3 4 4 4 6% 31%	1782
November	1st to 10th	Day	16% 9% 4 6% 5% 3 4 5% 5% 7% 36%	1671
	11th to 20th	Day	18% 10% 4 7% 5% 3 5% 4 6% 6% 31%	1630
	21st to end	Day	21% 10% 4 6% 5% 3 7% 5% 4 7% 28%	1520
December	1st to 10th	Day	25% 12% 6% 7% 8% 3 4 4 4 4 23%	1520
	11th to 20th	Day	22% 13% 5% 7% 5% 3 4 4 4 4 29%	1906
	21st to end	Day	27% 16% 5% 9% 5% 3 3 3 3 5% 22%	2772
January	1st to 10th	Night	17% 16% 5% 10% 7% 4 5% 4 4 6% 22%	2649
	11th to 20th	Night	16% 15% 6% 9% 7% 3 5% 4 4 5% 26%	2602
	21st to end	Night	12% 12% 6% 7% 7% 3 5% 5% 5% 6% 32%	2772
February	1st to 10th	Night	14% 14% 6% 10% 8% 3 5% 5% 5% 5% 25%	2390
	11th to 20th	Night	15% 10% 5% 9% 6% 3 5% 5% 5% 5% 31%	2180
	21st to end	Night	16% 12% 5% 8% 6% 3 4 4 4 6% 32%	1776
March	1st to 10th	Night	19% 12% 5% 7% 5% 3 5% 4 4 5% 30%	2150
	11th to 20th	Night	16% 13% 4 7% 6% 3 4 4 4 6% 32%	2097
	21st to end	Night	17% 9% 4 6% 5% 3 4 4 4 4 39%	1980
April	1st to 10th	Night	24% 8% 4 7% 4 3 4 4 5% 6% 31%	1800
	11th to 20th	Night	21% 7% 3 5% 5% 3 5% 5% 4 5% 37%	1775
	21st to end	Night	21% 11% 2 6% 4 3 3 4 5% 5% 36%	1647
May	1st to 10th	Night	22% 7% 4 6% 5% 2 4 4 4 6% 36%	1490
	11th to 20th	Night	20% 6% 3 5% 5% 2 4 5% 6% 6% 37%	1415
	21st to end	Night	16% 7% 3 6% 5% 4 4 4 5% 8% 39%	1550
June	1st to 10th	Night	22% 6% 3 5% 6% 3 3 5% 6% 8% 33%	1440
	11th to 20th	Night	16% 7% 2 6% 4 3 5% 5% 6% 7% 38%	1440
	21st to end	Night	18% 6% 3 6% 6% 3 5% 6% 5% 8% 35%	1440
July	1st to 10th	Night	10% 5% 2 6% 5% 3 5% 5% 8% 8% 43%	1440
	11th to 20th	Night	11% 6% 2 5% 5% 3 7% 6% 6% 9% 40%	1440
	21st to end	Night	11% 5% 2 6% 5% 3 5% 4 8% 8% 41%	1574
August	1st to 10th	Night	12% 5% 3 6% 5% 4 6% 4 7% 8% 42%	1432
	11th to 20th	Night	13% 6% 2 5% 5% 4 5% 5% 5% 8% 43%	1582
	21st to end	Night	14% 6% 2 5% 5% 2 4 5% 6% 7% 43%	1980
September	1st to 10th	Night	11% 5% 3 6% 5% 4 5% 4 5% 6% 46%	1800
	11th to 20th	Night	14% 6% 2 4 4 2 4 4 5% 6% 50%	1877
	21st to end	Night	15% 5% 2 5% 5% 3 3 4 4 7% 45%	1980
October	1st to 10th	Night	18% 6% 2 5% 5% 3 5% 4 4 6% 41%	2096
	11th to 20th	Night	19% 9% 3 6% 5% 4 4 4 5% 5% 36%	2205
	21st to end	Night	23% 9% 3 6% 6% 3 4 4 5% 6% 31%	2574
November	1st to 10th	Night	18% 9% 4 6% 5% 4 4 4 5% 6% 34%	2407
	11th to 20th	Night	19% 9% 4 7% 5% 3 4 4 5% 5% 35%	2547
	21st to end	Night	22% 13% 4 7% 6% 3 4 3 4 5% 30%	2660
December	1st to 10th	Night	21% 13% 5% 10% 6% 3 5% 5% 4 6% 23%	2660
	11th to 20th	Night	23% 13% 5% 8% 5% 2 3 3 4 5% 28%	3288
	21st to end	Night	28% 15% 5% 8% 5% 3 3 3 3 4 23%	4884

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% 5% 11% 16% 5%	1518
	11th to 20th	Day	60% 5% 9% 14% 11%	1480
	21st to end	Day	53% 5% 12% 18% 10% 1	1584
February	1st to 10th	Day	59% 4 10% 18% 7% 2	1568
	11th to 20th	Day	56% 7% 12% 15% 10% 1	1675
	21st to end	Day	59% 4 8% 16% 10% 2	1480
March	1st to 10th	Day	55% 5% 11% 16% 11% 2	1800
	11th to 20th	Day	51% 5% 13% 16% 13% 3	1858
	21st to end	Day	51% 4 10% 18% 13% 3	2376
April	1st to 10th	Day	55% 5% 8% 18% 12% 2	2160
	11th to 20th	Day	49% 4 8% 23% 14% 2	2134
	21st to end	Day	54% 5% 9% 16% 13% 3	2312
May	1st to 10th	Day	49% 5% 9% 20% 15% 2	2487
	11th to 20th	Day	46% 6% 11% 19% 15% 3	2482
	21st to end	Day	45% 8% 13% 18% 14% 2	2725
June	1st to 10th	Day	50% 7% 11% 18% 11% 2	2520
	11th to 20th	Day	42% 7% 11% 24% 13% 3	2520
	21st to end	Day	51% 8% 11% 18% 10% 1	2520
July	1st to 10th	Day	38% 10% 12% 27% 12% 1	2450
	11th to 20th	Day	40% 9% 14% 28% 10%	2445
	21st to end	Day	39% 10% 16% 26% 9%	2591
August	1st to 10th	Day	42% 9% 16% 24% 8%	2492
	11th to 20th	Day	38% 9% 18% 25% 10%	2298
	21st to end	Day	37% 7% 15% 26% 14%	2376
September	1st to 10th	Day	38% 7% 14% 28% 12% 1	2160
	11th to 20th	Day	35% 6% 13% 31% 15% 1	2082
	21st to end	Day	42% 6% 13% 27% 11% 1	1980
October	1st to 10th	Day	48% 6% 12% 23% 11%	1863
	11th to 20th	Day	53% 8% 13% 19% 6%	1754
	21st to end	Day	55% 5% 12% 19% 8% 1	1782
November	1st to 10th	Day	47% 6% 14% 23% 9% 1	1671
	11th to 20th	Day	53% 6% 12% 17% 11%	1630
	21st to end	Day	57% 6% 14% 15% 6% 1	1520
December	1st to 10th	Day	65% 5% 11% 14% 5%	1520
	11th to 20th	Day	58% 5% 11% 19% 7%	1906
	21st to end	Day	67% 5% 12% 10% 6%	2772
January	1st to 10th	Night	64% 6% 10% 15% 5%	2649
	11th to 20th	Night	61% 7% 10% 13% 8% 1	2602
	21st to end	Night	54% 5% 11% 17% 12% 1	2772
February	1st to 10th	Night	62% 5% 8% 17% 7% 1	2390
	11th to 20th	Night	55% 6% 10% 20% 9% 1	2182
	21st to end	Night	55% 5% 9% 17% 13% 1	1776
March	1st to 10th	Night	56% 5% 9% 17% 11% 2	2160
	11th to 20th	Night	55% 4 9% 16% 13% 3	2098
	21st to end	Night	51% 4 7% 20% 15% 4	1980
April	1st to 10th	Night	55% 4 8% 18% 14% 2	1800
	11th to 20th	Night	49% 4 7% 22% 15% 2	1775
	21st to end	Night	51% 5% 8% 19% 13% 4	1647
May	1st to 10th	Night	50% 4 8% 18% 15% 5%	1490
	11th to 20th	Night	46% 6% 9% 17% 17% 4	1416
	21st to end	Night	44% 6% 12% 19% 17% 2	1551
June	1st to 10th	Night	50% 6% 10% 21% 13% 1	1440
	11th to 20th	Night	43% 7% 12% 21% 14% 4	1440
	21st to end	Night	47% 8% 12% 19% 14%	1440
July	1st to 10th	Night	36% 10% 12% 26% 15% 1	1400
	11th to 20th	Night	38% 8% 15% 26% 12%	1392
	21st to end	Night	38% 9% 17% 25% 11%	1486
August	1st to 10th	Night	39% 9% 16% 25% 11%	1422
	11th to 20th	Night	38% 8% 17% 25% 11%	1582
	21st to end	Night	38% 8% 14% 27% 12% 1	1980
September	1st to 10th	Night	38% 7% 13% 26% 14% 1	1800
	11th to 20th	Night	36% 5% 14% 32% 12% 1	1877
	21st to end	Night	39% 7% 11% 28% 15%	1980
October	1st to 10th	Night	44% 7% 10% 25% 13% 1	2096
	11th to 20th	Night	51% 6% 11% 24% 8%	2205
	21st to end	Night	55% 5% 12% 18% 9% 1	2574
November	1st to 10th	Night	51% 5% 12% 22% 9% 1	2407
	11th to 20th	Night	51% 5% 12% 20% 10% 2	2547
	21st to end	Night	59% 5% 10% 18% 7%	2660
December	1st to 10th	Night	63% 5% 12% 15% 5%	2660
	11th to 20th	Night	60% 5% 9% 18% 8% 1	3288
	21st to end	Night	66% 5% 8% 15% 5%	4884

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% 14% 28% 24% 11%	180
	11th to 20th	Day	26% 12% 31% 25% 5% 1	170
	21st to end	Day	16% 11% 37% 23% 10% 2	176
February	1st to 10th	Day	32% 18% 33% 15% 1	218
	11th to 20th	Day	21% 11% 37% 26% 5%	333
	21st to end	Day	28% 8% 34% 25% 5%	346
March	1st to 10th	Day	24% 8% 33% 25% 10%	420
	11th to 20th	Day	21% 12% 33% 26% 6% 1	420
	21st to end	Day	26% 9% 32% 22% 10% 1	462
April	1st to 10th	Day	25% 14% 27% 24% 9% 2	420
	11th to 20th	Day	25% 15% 25% 23% 9% 3	412
	21st to end	Day	28% 10% 30% 22% 8% 3	420
May	1st to 10th	Day	22% 10% 32% 24% 9% 2	423
	11th to 20th	Day	19% 9% 30% 24% 13% 4	447
	21st to end	Day	19% 11% 31% 25% 13% 2	485
June	1st to 10th	Day	23% 10% 26% 26% 12% 3	450
	11th to 20th	Day	16% 10% 24% 31% 15% 4	450
	21st to end	Day	20% 8% 23% 30% 15% 4	450
July	1st to 10th	Day	14% 5% 22% 31% 21% 7%	445
	11th to 20th	Day	14% 5% 25% 33% 18% 5%	444
	21st to end	Day	14% 4 24% 32% 20% 6%	488
August	1st to 10th	Day	14% 6% 22% 30% 22% 7%	446
	11th to 20th	Day	10% 4 20% 32% 21% 13%	439
	21st to end	Day	15% 7% 24% 23% 20% 12%	495
September	1st to 10th	Day	12% 6% 27% 28% 19% 8%	450
	11th to 20th	Day	13% 8% 21% 28% 18% 11%	450
	21st to end	Day	18% 8% 26% 23% 19% 7%	450
October	1st to 10th	Day	20% 11% 27% 22% 15% 4	450
	11th to 20th	Day	21% 11% 31% 22% 12% 2	426
	21st to end	Day	32% 8% 28% 23% 10% 1	396
November	1st to 10th	Day	25% 13% 26% 25% 10% 1	365
	11th to 20th	Day	26% 10% 32% 20% 10% 1	290
	21st to end	Day	28% 13% 29% 17% 12% 1	180
December	1st to 10th	Day	31% 10% 22% 22% 12% 3	180
	11th to 20th	Day	23% 13% 36% 23% 4 1	180
	21st to end	Day	31% 15% 29% 17% 7% 2	198
January	1st to 10th	Night	26% 10% 28% 29% 6%	760
	11th to 20th	Night	25% 9% 33% 27% 7%	744
	21st to end	Night	19% 6% 35% 31% 8% 1	792
February	1st to 10th	Night	22% 8% 36% 27% 6% 1	720
	11th to 20th	Night	22% 8% 35% 29% 6% 1	703
	21st to end	Night	23% 7% 33% 32% 5%	592
March	1st to 10th	Night	24% 7% 32% 32% 6%	720
	11th to 20th	Night	24% 9% 32% 27% 8%	720
	21st to end	Night	22% 7% 31% 32% 8%	792
April	1st to 10th	Night	28% 8% 26% 30% 7%	720
	11th to 20th	Night	25% 9% 31% 29% 6%	711
	21st to end	Night	29% 7% 32% 24% 8%	567
May	1st to 10th	Night	23% 7% 29% 32% 8% 1	410
	11th to 20th	Night	23% 8% 29% 33% 7% 1	354
	21st to end	Night	19% 6% 33% 33% 9%	389
June	1st to 10th	Night	26% 4 24% 36% 10% 1	360
	11th to 20th	Night	19% 6% 26% 37% 12% 1	360
	21st to end	Night	19% 4 26% 37% 14%	360
July	1st to 10th	Night	11% 6% 25% 40% 17% 1	350
	11th to 20th	Night	11% 4 22% 45% 17% 1	348
	21st to end	Night	14% 2 19% 47% 16% 1	394
August	1st to 10th	Night	15% 4 13% 45% 22% 1	358
	11th to 20th	Night	14% 3 20% 36% 24% 3	518
	21st to end	Night	15% 4 21% 35% 22% 2	792
September	1st to 10th	Night	15% 3 22% 42% 17% 1	720
	11th to 20th	Night	18% 3 19% 37% 21% 2	720
	21st to end	Night	18% 4 25% 33% 17% 3	720
October	1st to 10th	Night	21% 6% 26% 34% 12% 1	720
	11th to 20th	Night	23% 9% 26% 31% 11% 1	720
	21st to end	Night	27% 8% 29% 29% 7%	792
November	1st to 10th	Night	24% 9% 29% 28% 9%	740
	11th to 20th	Night	23% 9% 33% 24% 10% 1	760
	21st to end	Night	29% 9% 30% 23% 9% 1	760
December	1st to 10th	Night	29% 8% 31% 25% 7%	760
	11th to 20th	Night	29% 10% 30% 25% 6% 1	760
	21st to end	Night	33% 9% 30% 22% 6%	836

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