Morin-Heights
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morin-Heights clear sky chart from 2005-11-06 to 2025-08-05.

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% 11% 4 9% 5% 5% 5% 4 5% 7% 30%	126053
	Night	15% 11% 4 10% 5% 5% 4 3 5% 6% 31%	122006
Transparency	Day	51% 6% 12% 20% 10% 1	129485
	Night	51% 6% 12% 19% 10% 1	126661
Seeing	Day	24% 18% 31% 19% 7% 2	15426
	Night	22% 14% 31% 24% 8% 1	24370

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	12% 23% 6% 13% 7% 3 5% 3 3 5% 20%	3597
	11th to 20th	Day	10% 16% 7% 15% 9% 6% 5% 3 4 5% 21%	3570
	21st to end	Day	7% 14% 8% 15% 6% 5% 6% 4 5% 6% 24%	3960
February	1st to 10th	Day	11% 18% 4 13% 7% 5% 4 3 4 6% 24%	1771
	11th to 20th	Day	12% 18% 5% 11% 5% 6% 4 3 5% 5% 25%	1823
	21st to end	Day	14% 17% 6% 10% 6% 4 5% 3 4 5% 25%	1650
March	1st to 10th	Day	16% 17% 6% 12% 7% 4 4 3 4 4 23%	4476
	11th to 20th	Day	10% 14% 5% 11% 5% 4 4 4 5% 7% 30%	4764
	21st to end	Day	16% 13% 4 9% 5% 4 3 3 4 5% 33%	5919
April	1st to 10th	Day	20% 13% 3 8% 5% 3 3 3 4 5% 31%	2400
	11th to 20th	Day	21% 11% 2 8% 4 4 4 3 4 6% 33%	2374
	21st to end	Day	22% 11% 4 7% 4 5% 4 3 5% 6% 30%	2552
May	1st to 10th	Day	25% 11% 4 9% 5% 5% 5% 3 5% 5% 23%	6346
	11th to 20th	Day	21% 9% 3 8% 5% 4 4 4 6% 7% 29%	6318
	21st to end	Day	23% 8% 3 7% 5% 5% 5% 3 5% 7% 29%	6949
June	1st to 10th	Day	21% 9% 3 7% 5% 5% 5% 4 6% 7% 27%	2800
	11th to 20th	Day	15% 7% 2 7% 6% 5% 5% 4 7% 7% 34%	2800
	21st to end	Day	22% 8% 3 8% 5% 5% 5% 4 6% 7% 27%	2800
July	1st to 10th	Day	15% 6% 3 8% 6% 7% 6% 5% 6% 8% 30%	6360
	11th to 20th	Day	12% 5% 2 6% 5% 5% 6% 5% 7% 9% 38%	6360
	21st to end	Day	10% 6% 2 6% 4 4 5% 4 7% 9% 44%	6926
August	1st to 10th	Day	15% 5% 3 8% 6% 6% 6% 5% 7% 9% 31%	4479
	11th to 20th	Day	15% 7% 3 7% 5% 5% 5% 4 7% 8% 35%	4020
	21st to end	Day	16% 5% 3 6% 5% 5% 5% 4 5% 9% 37%	4180
September	1st to 10th	Day	16% 6% 2 5% 4 4 5% 4 6% 7% 41%	2280
	11th to 20th	Day	14% 5% 3 6% 4 3 4 4 5% 7% 46%	2221
	21st to end	Day	19% 7% 2 6% 3 4 4 4 5% 6% 40%	2090
October	1st to 10th	Day	21% 8% 2 7% 4 4 4 4 5% 6% 34%	1929
	11th to 20th	Day	22% 11% 3 8% 5% 4 5% 4 5% 6% 27%	1876
	21st to end	Day	24% 13% 3 7% 5% 4 4 3 5% 6% 27%	1881
November	1st to 10th	Day	14% 11% 4 7% 6% 4 5% 4 6% 6% 33%	1761
	11th to 20th	Day	18% 13% 4 9% 5% 5% 4 4 5% 6% 27%	1675
	21st to end	Day	21% 14% 6% 9% 5% 4 5% 4 6% 5% 22%	1600
December	1st to 10th	Day	17% 17% 9% 13% 6% 4 4 3 4 5% 17%	2600
	11th to 20th	Day	16% 15% 7% 12% 6% 4 4 3 4 5% 25%	2986
	21st to end	Day	19% 16% 6% 9% 4 4 4 3 4 4 25%	3960
January	1st to 10th	Night	10% 22% 9% 14% 5% 4 4 3 3 5% 20%	6349
	11th to 20th	Night	7% 14% 7% 20% 8% 6% 4 3 5% 5% 21%	6315
	21st to end	Night	8% 13% 6% 16% 7% 6% 5% 4 5% 5% 24%	6996
February	1st to 10th	Night	11% 14% 5% 12% 6% 5% 5% 4 5% 6% 26%	2625
	11th to 20th	Night	11% 13% 5% 12% 6% 5% 5% 4 5% 6% 28%	2462
	21st to end	Night	12% 15% 5% 11% 6% 4 4 3 6% 6% 29%	1980
March	1st to 10th	Night	18% 14% 5% 11% 6% 4 4 3 4 5% 28%	5364
	11th to 20th	Night	10% 14% 4 9% 4 5% 5% 4 6% 8% 31%	5191
	21st to end	Night	15% 11% 4 9% 5% 5% 4 3 5% 6% 32%	5012
April	1st to 10th	Night	21% 12% 3 7% 5% 3 4 2 4 6% 32%	2000
	11th to 20th	Night	18% 8% 3 7% 5% 5% 4 4 6% 5% 36%	1975
	21st to end	Night	21% 8% 3 8% 4 4 4 4 5% 5% 35%	1855
May	1st to 10th	Night	21% 10% 4 9% 6% 5% 5% 4 5% 6% 26%	3604
	11th to 20th	Night	20% 9% 3 7% 4 4 4 3 5% 6% 35%	3575
	21st to end	Night	21% 10% 3 7% 5% 5% 4 4 5% 7% 29%	3926
June	1st to 10th	Night	19% 9% 3 6% 5% 4 4 4 6% 9% 32%	1600
	11th to 20th	Night	17% 7% 2 6% 5% 4 4 4 5% 8% 38%	1600
	21st to end	Night	20% 7% 2 6% 5% 5% 4 5% 5% 6% 36%	1600
July	1st to 10th	Night	14% 6% 2 8% 6% 6% 6% 5% 7% 7% 34%	3600
	11th to 20th	Night	13% 5% 2 6% 4 5% 5% 3 6% 7% 43%	3600
	21st to end	Night	9% 5% 2 5% 4 5% 5% 4 7% 7% 47%	3926
August	1st to 10th	Night	12% 6% 2 7% 5% 5% 5% 4 6% 8% 40%	2538
	11th to 20th	Night	14% 7% 3 6% 5% 4 5% 3 5% 6% 42%	2774
	21st to end	Night	15% 6% 2 7% 4 5% 4 3 5% 7% 43%	3476
September	1st to 10th	Night	11% 5% 2 7% 4 4 4 4 5% 6% 47%	1900
	11th to 20th	Night	14% 5% 2 5% 3 3 3 3 6% 7% 49%	1958
	21st to end	Night	18% 6% 2 5% 3 4 4 3 5% 7% 44%	2090
October	1st to 10th	Night	17% 7% 3 7% 4 5% 4 3 5% 5% 39%	2250
	11th to 20th	Night	20% 9% 2 7% 5% 5% 4 3 5% 6% 34%	2304
	21st to end	Night	22% 10% 3 7% 5% 4 4 4 5% 6% 29%	2717
November	1st to 10th	Night	17% 9% 5% 8% 6% 4 5% 4 6% 6% 30%	2537
	11th to 20th	Night	17% 10% 4 9% 5% 5% 4 3 5% 6% 32%	2723
	21st to end	Night	18% 15% 5% 9% 6% 4 3 4 5% 6% 26%	2800
December	1st to 10th	Night	15% 14% 6% 11% 7% 5% 5% 4 6% 8% 19%	4580
	11th to 20th	Night	21% 13% 5% 10% 6% 4 4 3 4 4 25%	5208
	21st to end	Night	20% 19% 4 9% 5% 3 3 2 3 4 27%	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	65% 7% 9% 15% 4 1	3598
	11th to 20th	Day	62% 6% 8% 16% 7% 2	3600
	21st to end	Day	58% 7% 9% 13% 12% 1	3960
February	1st to 10th	Day	60% 5% 8% 17% 8% 2	1771
	11th to 20th	Day	60% 5% 11% 15% 9% 1	1832
	21st to end	Day	61% 4 8% 15% 9% 2	1650
March	1st to 10th	Day	62% 5% 7% 12% 11% 3	4479
	11th to 20th	Day	51% 5% 17% 14% 11% 2	4764
	21st to end	Day	53% 4 6% 16% 19% 2	5919
April	1st to 10th	Day	55% 4 8% 17% 13% 3	2400
	11th to 20th	Day	51% 4 9% 21% 13% 2	2374
	21st to end	Day	55% 5% 8% 17% 12% 3	2552
May	1st to 10th	Day	61% 6% 7% 17% 8% 1	6357
	11th to 20th	Day	51% 9% 15% 16% 8% 2	6322
	21st to end	Day	53% 6% 11% 17% 12% 1	6949
June	1st to 10th	Day	53% 6% 10% 17% 12% 2	2800
	11th to 20th	Day	45% 7% 12% 21% 12% 3	2800
	21st to end	Day	55% 8% 11% 17% 9% 1	2800
July	1st to 10th	Day	48% 8% 14% 23% 7%	6290
	11th to 20th	Day	37% 8% 15% 30% 10%	6285
	21st to end	Day	35% 6% 17% 33% 9%	6728
August	1st to 10th	Day	45% 8% 17% 22% 8%	4465
	11th to 20th	Day	42% 8% 17% 26% 6%	4062
	21st to end	Day	42% 8% 15% 20% 13% 1	4180
September	1st to 10th	Day	40% 6% 14% 27% 13%	2280
	11th to 20th	Day	36% 6% 15% 29% 12% 1	2221
	21st to end	Day	43% 6% 14% 25% 12%	2090
October	1st to 10th	Day	43% 6% 16% 26% 8%	3202
	11th to 20th	Day	45% 7% 16% 24% 8%	3092
	21st to end	Day	45% 5% 23% 17% 9% 1	3081
November	1st to 10th	Day	49% 7% 14% 20% 9% 1	1761
	11th to 20th	Day	55% 4 15% 15% 10% 1	1675
	21st to end	Day	61% 6% 14% 14% 4 1	1600
December	1st to 10th	Day	69% 5% 10% 13% 3	2600
	11th to 20th	Day	60% 4 10% 17% 9%	2986
	21st to end	Day	62% 5% 8% 15% 9%	3960
January	1st to 10th	Night	66% 5% 12% 12% 4	6349
	11th to 20th	Night	62% 6% 14% 13% 5% 1	6360
	21st to end	Night	59% 7% 10% 10% 14% 1	6996
February	1st to 10th	Night	58% 5% 10% 19% 8% 1	2625
	11th to 20th	Night	54% 6% 13% 18% 9% 1	2464
	21st to end	Night	56% 4 9% 18% 11% 2	1980
March	1st to 10th	Night	59% 4 8% 14% 12% 4	5374
	11th to 20th	Night	50% 7% 14% 16% 11% 3	5192
	21st to end	Night	52% 4 8% 21% 12% 3	5012
April	1st to 10th	Night	53% 4 8% 18% 15% 2	2000
	11th to 20th	Night	48% 5% 9% 22% 15% 2	1975
	21st to end	Night	50% 5% 8% 20% 13% 3	1855
May	1st to 10th	Night	57% 7% 10% 18% 7% 2	3610
	11th to 20th	Night	48% 8% 13% 19% 10% 2	3576
	21st to end	Night	53% 6% 10% 16% 13% 1	3927
June	1st to 10th	Night	48% 6% 12% 21% 13% 1	1600
	11th to 20th	Night	44% 6% 11% 23% 13% 3	1600
	21st to end	Night	47% 8% 11% 20% 13% 1	1600
July	1st to 10th	Night	44% 8% 18% 21% 8%	3560
	11th to 20th	Night	37% 7% 18% 31% 7%	3552
	21st to end	Night	33% 6% 17% 31% 12%	3809
August	1st to 10th	Night	40% 8% 15% 28% 9%	2528
	11th to 20th	Night	40% 7% 19% 27% 7%	2798
	21st to end	Night	40% 7% 16% 23% 13% 2	3476
September	1st to 10th	Night	36% 8% 13% 27% 16% 1	1900
	11th to 20th	Night	35% 6% 14% 33% 12% 1	1958
	21st to end	Night	39% 6% 12% 29% 14%	2090
October	1st to 10th	Night	42% 6% 15% 25% 11% 1	3757
	11th to 20th	Night	41% 7% 14% 27% 11%	3827
	21st to end	Night	44% 6% 20% 17% 11% 2	4467
November	1st to 10th	Night	51% 6% 14% 21% 7% 1	2537
	11th to 20th	Night	51% 5% 14% 18% 9% 2	2723
	21st to end	Night	57% 6% 13% 17% 6% 1	2800
December	1st to 10th	Night	61% 7% 14% 15% 4	4580
	11th to 20th	Night	60% 5% 8% 16% 11% 1	5208
	21st to end	Night	62% 4 7% 13% 13% 1	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	21% 23% 39% 15% 4	200
	11th to 20th	Day	28% 19% 38% 12% 5% 1	200
	21st to end	Day	20% 23% 38% 14% 4	220
February	1st to 10th	Day	32% 29% 31% 8% 1	286
	11th to 20th	Day	23% 28% 38% 10% 1	370
	21st to end	Day	27% 25% 31% 15% 2	414
March	1st to 10th	Day	29% 20% 31% 17% 3	500
	11th to 20th	Day	23% 27% 32% 14% 4 1	500
	21st to end	Day	30% 22% 27% 14% 6% 1	550
April	1st to 10th	Day	33% 19% 28% 13% 6% 1	500
	11th to 20th	Day	34% 19% 26% 13% 7% 1	492
	21st to end	Day	30% 22% 29% 14% 4 1	500
May	1st to 10th	Day	27% 20% 34% 14% 5% 1	503
	11th to 20th	Day	24% 19% 31% 21% 5% 1	527
	21st to end	Day	25% 19% 30% 19% 6%	573
June	1st to 10th	Day	24% 18% 34% 17% 6% 1	530
	11th to 20th	Day	18% 20% 35% 18% 8% 2	530
	21st to end	Day	27% 13% 34% 17% 7% 2	530
July	1st to 10th	Day	15% 11% 37% 25% 10% 2	525
	11th to 20th	Day	16% 12% 37% 27% 7% 1	524
	21st to end	Day	14% 11% 36% 28% 10% 1	576
August	1st to 10th	Day	16% 9% 31% 30% 12% 2	502
	11th to 20th	Day	14% 9% 29% 30% 12% 6%	479
	21st to end	Day	17% 14% 29% 22% 12% 6%	539
September	1st to 10th	Day	18% 11% 33% 24% 10% 5%	490
	11th to 20th	Day	12% 11% 27% 26% 17% 7%	490
	21st to end	Day	21% 14% 26% 23% 12% 4	490
October	1st to 10th	Day	24% 19% 24% 21% 10% 1	490
	11th to 20th	Day	25% 17% 32% 18% 7% 1	477
	21st to end	Day	32% 15% 30% 18% 5%	429
November	1st to 10th	Day	29% 19% 29% 18% 4 1	395
	11th to 20th	Day	26% 23% 33% 15% 3	275
	21st to end	Day	29% 25% 32% 14% 2	200
December	1st to 10th	Day	29% 17% 33% 17% 4 1	200
	11th to 20th	Day	30% 24% 33% 12% 1 1	200
	21st to end	Day	33% 23% 25% 13% 4 2	220
January	1st to 10th	Night	23% 18% 35% 21% 3	800
	11th to 20th	Night	23% 20% 31% 21% 4	800
	21st to end	Night	16% 16% 39% 23% 5% 1	880
February	1st to 10th	Night	20% 19% 38% 20% 4 1	800
	11th to 20th	Night	21% 19% 40% 16% 3 1	783
	21st to end	Night	22% 17% 34% 25% 2	660
March	1st to 10th	Night	24% 19% 34% 21% 3	800
	11th to 20th	Night	23% 17% 35% 19% 5%	800
	21st to end	Night	23% 17% 33% 22% 5% 1	880
April	1st to 10th	Night	28% 17% 29% 23% 4	800
	11th to 20th	Night	24% 15% 34% 22% 5%	791
	21st to end	Night	26% 15% 34% 18% 7%	655
May	1st to 10th	Night	25% 13% 33% 21% 6% 2	410
	11th to 20th	Night	21% 12% 30% 29% 8% 1	394
	21st to end	Night	20% 9% 39% 25% 7%	433
June	1st to 10th	Night	24% 10% 31% 28% 7%	400
	11th to 20th	Night	23% 8% 30% 30% 10% 1	400
	21st to end	Night	21% 8% 27% 31% 13% 1	400
July	1st to 10th	Night	11% 8% 31% 35% 13% 1	390
	11th to 20th	Night	11% 6% 27% 43% 13%	388
	21st to end	Night	13% 5% 26% 43% 11% 1	438
August	1st to 10th	Night	13% 5% 22% 42% 16% 2	386
	11th to 20th	Night	11% 6% 26% 32% 22% 2	550
	21st to end	Night	15% 7% 28% 32% 16% 2	836
September	1st to 10th	Night	13% 8% 31% 35% 12% 1	760
	11th to 20th	Night	16% 8% 24% 30% 20% 2	760
	21st to end	Night	20% 9% 25% 29% 16% 2	760
October	1st to 10th	Night	22% 11% 28% 27% 10% 1	760
	11th to 20th	Night	25% 13% 29% 24% 8% 1	760
	21st to end	Night	27% 15% 31% 22% 5%	836
November	1st to 10th	Night	24% 18% 29% 23% 6% 1	780
	11th to 20th	Night	23% 16% 33% 20% 7% 1	800
	21st to end	Night	28% 19% 28% 19% 5% 1	800
December	1st to 10th	Night	27% 18% 33% 17% 5%	800
	11th to 20th	Night	28% 20% 28% 18% 4 1	800
	21st to end	Night	31% 18% 30% 17% 4	880

Page generated at 2025-08-02 01:32:25. Version ac07

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