Dolbeau-Mistassini
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dolbeau-Mistassini 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% 4 10% 6% 5% 5% 4 6% 7% 27%	131075
	Night	16% 13% 5% 11% 6% 5% 5% 4 5% 6% 24%	130497
Transparency	Day	57% 3 11% 19% 8% 1	134477
	Night	61% 3 10% 18% 7%	135170
Seeing	Day	23% 8% 27% 26% 13% 4	16860
	Night	24% 7% 26% 31% 11% 1	25405

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% 21% 8% 14% 6% 5% 6% 4 4 4 15%	4532
	11th to 20th	Day	9% 14% 8% 19% 8% 8% 6% 5% 6% 5% 13%	4650
	21st to end	Day	4 9% 6% 15% 8% 6% 6% 5% 8% 7% 26%	5124
February	1st to 10th	Day	7% 12% 4 11% 9% 7% 8% 5% 6% 6% 25%	1680
	11th to 20th	Day	11% 14% 5% 12% 8% 7% 6% 4 5% 6% 23%	1922
	21st to end	Day	10% 13% 4 12% 6% 6% 6% 5% 7% 6% 25%	1730
March	1st to 10th	Day	17% 17% 5% 9% 5% 4 3 3 5% 5% 27%	4576
	11th to 20th	Day	16% 16% 4 10% 6% 6% 5% 4 5% 6% 21%	4723
	21st to end	Day	13% 11% 5% 10% 5% 5% 5% 4 6% 6% 30%	5956
April	1st to 10th	Day	16% 14% 4 11% 8% 4 4 3 5% 5% 26%	2400
	11th to 20th	Day	18% 9% 3 8% 5% 5% 4 3 6% 6% 32%	2467
	21st to end	Day	21% 10% 4 8% 4 5% 4 3 5% 6% 31%	2600
May	1st to 10th	Day	20% 10% 3 8% 5% 5% 5% 4 5% 6% 29%	6344
	11th to 20th	Day	25% 8% 3 7% 4 5% 4 3 5% 5% 31%	6318
	21st to end	Day	15% 8% 3 8% 5% 5% 5% 4 6% 7% 32%	7264
June	1st to 10th	Day	20% 8% 3 8% 5% 5% 5% 5% 6% 7% 29%	3000
	11th to 20th	Day	16% 7% 3 7% 5% 5% 5% 4 8% 7% 33%	3000
	21st to end	Day	22% 8% 2 7% 6% 5% 5% 3 6% 8% 28%	3000
July	1st to 10th	Day	17% 8% 3 7% 5% 5% 6% 4 7% 9% 28%	6738
	11th to 20th	Day	16% 6% 3 8% 5% 6% 6% 5% 7% 9% 30%	6360
	21st to end	Day	12% 6% 3 7% 5% 5% 6% 5% 7% 9% 37%	6926
August	1st to 10th	Day	15% 6% 3 9% 5% 6% 6% 6% 7% 10% 26%	4563
	11th to 20th	Day	14% 7% 4 9% 6% 6% 6% 5% 7% 10% 28%	4314
	21st to end	Day	15% 7% 3 9% 6% 6% 6% 4 6% 7% 33%	4460
September	1st to 10th	Day	17% 7% 2 9% 5% 5% 5% 4 6% 8% 31%	2400
	11th to 20th	Day	17% 7% 3 7% 4 5% 5% 4 6% 8% 35%	2270
	21st to end	Day	22% 8% 2 8% 5% 5% 5% 4 5% 6% 30%	2200
October	1st to 10th	Day	18% 9% 3 7% 5% 5% 5% 4 6% 7% 31%	2116
	11th to 20th	Day	26% 12% 4 10% 5% 6% 5% 4 4 6% 19%	1844
	21st to end	Day	27% 14% 4 7% 5% 5% 4 3 4 6% 21%	1980
November	1st to 10th	Day	20% 15% 4 10% 6% 5% 5% 4 4 4 21%	1851
	11th to 20th	Day	21% 14% 6% 10% 7% 5% 5% 3 5% 5% 19%	1706
	21st to end	Day	22% 18% 6% 11% 6% 5% 4 3 4 6% 15%	1470
December	1st to 10th	Day	16% 17% 6% 13% 7% 7% 5% 4 6% 5% 16%	2350
	11th to 20th	Day	18% 13% 5% 13% 9% 6% 6% 4 4 5% 18%	2688
	21st to end	Day	16% 15% 5% 12% 8% 7% 6% 5% 6% 5% 15%	3553
January	1st to 10th	Night	13% 22% 8% 14% 7% 5% 6% 4 4 5% 13%	8353
	11th to 20th	Night	9% 21% 8% 20% 8% 6% 5% 3 4 4 12%	8235
	21st to end	Night	4 9% 5% 13% 9% 9% 9% 7% 8% 7% 20%	9057
February	1st to 10th	Night	9% 12% 5% 13% 8% 7% 6% 4 6% 6% 26%	2940
	11th to 20th	Night	9% 18% 6% 13% 8% 6% 5% 3 5% 5% 20%	2580
	21st to end	Night	10% 16% 5% 10% 7% 6% 4 4 6% 7% 27%	2076
March	1st to 10th	Night	17% 14% 4 11% 6% 5% 6% 5% 6% 6% 20%	5484
	11th to 20th	Night	16% 14% 5% 12% 6% 6% 5% 4 5% 6% 22%	5390
	21st to end	Night	15% 15% 4 9% 6% 4 4 4 5% 6% 29%	4972
April	1st to 10th	Night	20% 16% 4 9% 4 5% 5% 4 4 5% 26%	2000
	11th to 20th	Night	19% 11% 3 6% 4 5% 4 4 5% 7% 33%	1882
	21st to end	Night	19% 10% 3 8% 6% 4 3 4 5% 6% 32%	1800
May	1st to 10th	Night	19% 9% 3 7% 4 4 5% 3 4 6% 35%	3640
	11th to 20th	Night	27% 9% 3 7% 4 4 4 3 5% 5% 28%	3575
	21st to end	Night	20% 8% 3 8% 5% 4 5% 3 5% 7% 32%	3625
June	1st to 10th	Night	20% 8% 3 8% 6% 5% 4 4 6% 7% 28%	1400
	11th to 20th	Night	16% 8% 3 7% 5% 4 5% 3 6% 7% 36%	1400
	21st to end	Night	18% 7% 3 7% 5% 5% 5% 5% 8% 7% 29%	1400
July	1st to 10th	Night	14% 7% 2 9% 7% 5% 7% 5% 7% 8% 29%	3234
	11th to 20th	Night	14% 7% 3 9% 6% 6% 5% 5% 8% 8% 30%	3600
	21st to end	Night	13% 6% 2 7% 5% 5% 5% 4 6% 8% 42%	3926
August	1st to 10th	Night	14% 6% 3 8% 5% 5% 6% 4 8% 9% 32%	2586
	11th to 20th	Night	15% 7% 3 8% 5% 4 4 4 6% 9% 35%	2701
	21st to end	Night	15% 7% 2 7% 4 4 5% 4 6% 8% 37%	3421
September	1st to 10th	Night	16% 7% 3 7% 5% 4 5% 3 6% 7% 38%	2000
	11th to 20th	Night	19% 6% 3 7% 4 4 4 4 5% 6% 37%	2130
	21st to end	Night	20% 6% 3 8% 4 5% 4 4 5% 5% 36%	2200
October	1st to 10th	Night	19% 8% 2 6% 5% 4 4 4 5% 7% 36%	2280
	11th to 20th	Night	27% 12% 4 7% 4 5% 5% 3 5% 6% 22%	2555
	21st to end	Night	28% 12% 3 8% 5% 5% 5% 4 5% 5% 20%	2860
November	1st to 10th	Night	23% 14% 4 8% 5% 4 4 4 5% 6% 21%	2667
	11th to 20th	Night	20% 17% 5% 11% 5% 5% 4 3 5% 6% 20%	2910
	21st to end	Night	22% 18% 5% 13% 6% 5% 4 3 4 4 15%	3150
December	1st to 10th	Night	13% 16% 7% 18% 10% 7% 5% 3 4 4 14%	5060
	11th to 20th	Night	21% 15% 5% 12% 8% 4 4 3 5% 5% 18%	5741
	21st to end	Night	15% 18% 8% 12% 6% 6% 4 4 5% 4 19%	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	75% 2 8% 13% 2	4533
	11th to 20th	Day	74% 2 7% 12% 5%	4680
	21st to end	Day	56% 2 11% 22% 8%	5124
February	1st to 10th	Day	59% 3 9% 19% 9% 1	1680
	11th to 20th	Day	64% 3 8% 17% 8%	1931
	21st to end	Day	57% 3 8% 21% 9% 1	1730
March	1st to 10th	Day	60% 2 9% 13% 14% 1	4579
	11th to 20th	Day	66% 3 9% 14% 8%	4723
	21st to end	Day	55% 2 8% 17% 16% 2	5956
April	1st to 10th	Day	61% 2 10% 16% 9% 2	2400
	11th to 20th	Day	52% 2 9% 24% 12% 1	2467
	21st to end	Day	56% 2 8% 21% 13% 1	2600
May	1st to 10th	Day	57% 2 9% 18% 12% 1	6355
	11th to 20th	Day	57% 2 7% 21% 11% 2	6322
	21st to end	Day	51% 3 8% 21% 16% 2	7264
June	1st to 10th	Day	53% 3 8% 22% 13% 1	3000
	11th to 20th	Day	47% 4 12% 22% 13% 2	3000
	21st to end	Day	55% 3 11% 20% 11% 1	3000
July	1st to 10th	Day	51% 5% 13% 27% 4	6664
	11th to 20th	Day	48% 6% 17% 25% 4	6285
	21st to end	Day	43% 4 17% 27% 8%	6728
August	1st to 10th	Day	51% 5% 18% 23% 3	4549
	11th to 20th	Day	50% 5% 19% 21% 4	4356
	21st to end	Day	49% 5% 14% 20% 11%	4460
September	1st to 10th	Day	51% 4 16% 22% 7%	2400
	11th to 20th	Day	47% 4 19% 23% 6%	2270
	21st to end	Day	54% 4 13% 22% 6%	2200
October	1st to 10th	Day	54% 4 13% 24% 4 1	3441
	11th to 20th	Day	66% 4 14% 15% 2	2982
	21st to end	Day	64% 4 15% 14% 3	3180
November	1st to 10th	Day	67% 2 10% 15% 4 1	1851
	11th to 20th	Day	67% 3 10% 16% 4	1706
	21st to end	Day	73% 3 10% 12% 3	1470
December	1st to 10th	Day	71% 4 12% 12% 2	2350
	11th to 20th	Day	69% 4 7% 14% 7%	2688
	21st to end	Day	71% 3 7% 13% 6%	3553
January	1st to 10th	Night	75% 2 7% 13% 3	8353
	11th to 20th	Night	78% 2 5% 11% 4	8280
	21st to end	Night	61% 2 10% 19% 7%	9057
February	1st to 10th	Night	58% 3 9% 19% 10%	2940
	11th to 20th	Night	66% 2 8% 15% 8%	2582
	21st to end	Night	58% 3 9% 22% 8%	2076
March	1st to 10th	Night	65% 2 8% 15% 9%	5494
	11th to 20th	Night	65% 2 8% 14% 9% 1	5391
	21st to end	Night	57% 1 6% 23% 11% 1	4972
April	1st to 10th	Night	62% 3 7% 18% 8% 3	2000
	11th to 20th	Night	53% 2 7% 25% 13%	1882
	21st to end	Night	53% 3 8% 21% 13% 2	1800
May	1st to 10th	Night	53% 2 7% 22% 15% 1	3646
	11th to 20th	Night	60% 1 5% 22% 10% 1	3576
	21st to end	Night	53% 3 8% 18% 17% 1	3626
June	1st to 10th	Night	54% 4 9% 23% 10% 1	1400
	11th to 20th	Night	47% 4 9% 21% 14% 3	1400
	21st to end	Night	52% 4 12% 21% 11% 1	1400
July	1st to 10th	Night	51% 5% 13% 23% 8%	3198
	11th to 20th	Night	49% 6% 18% 23% 4	3552
	21st to end	Night	41% 5% 16% 29% 9%	3809
August	1st to 10th	Night	47% 6% 19% 23% 6%	2576
	11th to 20th	Night	45% 5% 24% 20% 5%	2725
	21st to end	Night	44% 4 16% 28% 8%	3421
September	1st to 10th	Night	45% 4 16% 27% 8% 1	2000
	11th to 20th	Night	49% 2 18% 25% 6%	2130
	21st to end	Night	51% 3 12% 26% 8%	2200
October	1st to 10th	Night	51% 4 14% 24% 6% 1	3722
	11th to 20th	Night	61% 3 12% 19% 4	4156
	21st to end	Night	65% 4 12% 14% 4	4610
November	1st to 10th	Night	65% 3 12% 15% 5%	2667
	11th to 20th	Night	66% 3 11% 15% 4	2910
	21st to end	Night	75% 2 8% 12% 3	3150
December	1st to 10th	Night	75% 3 10% 10% 2	5060
	11th to 20th	Night	69% 2 7% 18% 4	5742
	21st to end	Night	68% 2 8% 16% 6% 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	22% 9% 28% 31% 9% 1	220
	11th to 20th	Day	17% 7% 31% 25% 16% 3	220
	21st to end	Day	15% 5% 27% 31% 17% 5%	242
February	1st to 10th	Day	13% 9% 35% 25% 13% 5%	220
	11th to 20th	Day	21% 12% 31% 28% 9%	421
	21st to end	Day	20% 10% 36% 24% 10% 1	446
March	1st to 10th	Day	22% 11% 28% 25% 12% 1	540
	11th to 20th	Day	26% 9% 29% 23% 10% 2	528
	21st to end	Day	25% 11% 27% 26% 9% 3	550
April	1st to 10th	Day	25% 12% 24% 28% 10% 1	500
	11th to 20th	Day	21% 10% 27% 26% 13% 3	492
	21st to end	Day	26% 10% 32% 19% 11% 2	500
May	1st to 10th	Day	28% 12% 24% 23% 10% 3	503
	11th to 20th	Day	21% 10% 27% 25% 13% 4	527
	21st to end	Day	22% 10% 29% 27% 9% 2	706
June	1st to 10th	Day	25% 6% 28% 26% 12% 2	730
	11th to 20th	Day	20% 6% 28% 30% 13% 3	730
	21st to end	Day	24% 6% 23% 28% 15% 3	730
July	1st to 10th	Day	19% 7% 24% 34% 15% 3	691
	11th to 20th	Day	20% 5% 26% 29% 15% 6%	524
	21st to end	Day	18% 4 26% 25% 22% 6%	576
August	1st to 10th	Day	17% 5% 22% 29% 18% 9%	526
	11th to 20th	Day	18% 4 18% 31% 19% 9%	519
	21st to end	Day	23% 6% 23% 23% 16% 8%	583
September	1st to 10th	Day	22% 7% 27% 21% 16% 7%	530
	11th to 20th	Day	19% 8% 24% 26% 17% 6%	530
	21st to end	Day	23% 8% 23% 23% 17% 6%	530
October	1st to 10th	Day	23% 9% 26% 22% 13% 5%	530
	11th to 20th	Day	31% 7% 27% 20% 11% 3	444
	21st to end	Day	36% 8% 25% 21% 10% 1	462
November	1st to 10th	Day	31% 14% 28% 21% 5% 1	425
	11th to 20th	Day	29% 11% 28% 20% 10% 2	283
	21st to end	Day	31% 10% 31% 20% 6% 3	220
December	1st to 10th	Day	20% 9% 25% 27% 15% 4	220
	11th to 20th	Day	25% 7% 34% 23% 7% 4	220
	21st to end	Day	28% 9% 25% 24% 12% 2	242
January	1st to 10th	Night	24% 6% 28% 32% 9%	862
	11th to 20th	Night	23% 9% 28% 28% 11% 1	840
	21st to end	Night	14% 5% 25% 40% 14% 1	924
February	1st to 10th	Night	13% 6% 30% 35% 13% 2	840
	11th to 20th	Night	20% 7% 32% 32% 9% 1	823
	21st to end	Night	17% 9% 29% 32% 11% 1	692
March	1st to 10th	Night	21% 8% 30% 32% 8%	840
	11th to 20th	Night	24% 10% 29% 26% 11%	829
	21st to end	Night	23% 8% 30% 30% 9% 1	880
April	1st to 10th	Night	30% 8% 25% 29% 7% 1	800
	11th to 20th	Night	25% 7% 30% 29% 9%	698
	21st to end	Night	23% 12% 33% 25% 8%	600
May	1st to 10th	Night	25% 8% 31% 28% 7% 1	420
	11th to 20th	Night	26% 7% 30% 28% 8% 1	394
	21st to end	Night	25% 6% 32% 29% 8% 1	433
June	1st to 10th	Night	24% 4 28% 36% 7% 1	400
	11th to 20th	Night	20% 4 26% 37% 13% 1	400
	21st to end	Night	22% 5% 23% 35% 14% 1	400
July	1st to 10th	Night	21% 2 24% 39% 13% 1	390
	11th to 20th	Night	16% 2 22% 41% 18%	388
	21st to end	Night	21% 3 18% 41% 18% 1	438
August	1st to 10th	Night	17% 3 16% 44% 17% 2	398
	11th to 20th	Night	20% 2 18% 36% 22% 2	482
	21st to end	Night	21% 4 21% 33% 19% 3	780
September	1st to 10th	Night	21% 5% 22% 36% 16% 1	800
	11th to 20th	Night	24% 6% 21% 31% 16% 2	800
	21st to end	Night	24% 5% 27% 31% 12% 2	800
October	1st to 10th	Night	24% 5% 26% 32% 12% 1	800
	11th to 20th	Night	34% 5% 25% 27% 9% 1	800
	21st to end	Night	36% 6% 25% 24% 8%	880
November	1st to 10th	Night	32% 10% 25% 25% 6% 2	820
	11th to 20th	Night	29% 8% 27% 26% 9% 1	859
	21st to end	Night	32% 9% 28% 23% 7% 1	950
December	1st to 10th	Night	26% 7% 26% 30% 10% 1	950
	11th to 20th	Night	26% 9% 26% 28% 10% 1	950
	21st to end	Night	27% 8% 24% 29% 10% 2	1045

Page generated at 2026-03-15 02:23:52. Version ac07

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