Baie-James
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Baie-James 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	17% 14% 5% 11% 7% 6% 5% 4 5% 5% 21%	107904
	Night	15% 16% 6% 13% 8% 7% 6% 4 5% 4 17%	110923
Transparency	Day	65% 5% 8% 15% 7%	111327
	Night	70% 4 8% 13% 5%	115666
Seeing	Day	25% 12% 30% 22% 9% 2	16141
	Night	24% 11% 30% 25% 9% 1	24691

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	10% 23% 8% 21% 12% 8% 4 3 4 3 3	3136
	11th to 20th	Day	6% 20% 8% 20% 12% 11% 6% 5% 7% 2 3	3133
	21st to end	Day	5% 12% 4 13% 9% 10% 13% 10% 8% 5% 10%	3849
February	1st to 10th	Day	6% 12% 5% 14% 10% 9% 12% 10% 9% 4 9%	1666
	11th to 20th	Day	6% 18% 6% 14% 10% 8% 8% 8% 8% 5% 9%	1753
	21st to end	Day	7% 13% 6% 12% 10% 7% 9% 7% 9% 7% 13%	1501
March	1st to 10th	Day	17% 15% 4 11% 6% 7% 8% 6% 6% 4 17%	3116
	11th to 20th	Day	7% 14% 7% 19% 13% 8% 7% 4 5% 5% 12%	3438
	21st to end	Day	11% 15% 6% 17% 10% 6% 6% 4 6% 5% 15%	4038
April	1st to 10th	Day	15% 17% 5% 14% 5% 6% 5% 3 4 6% 21%	2280
	11th to 20th	Day	14% 13% 4 12% 6% 5% 5% 3 5% 5% 28%	2328
	21st to end	Day	17% 14% 4 8% 7% 5% 4 3 5% 4 30%	2659
May	1st to 10th	Day	16% 17% 5% 9% 5% 4 5% 3 5% 5% 27%	4426
	11th to 20th	Day	16% 16% 5% 9% 5% 5% 5% 3 5% 6% 25%	4398
	21st to end	Day	15% 11% 4 9% 5% 5% 5% 4 6% 7% 31%	5139
June	1st to 10th	Day	21% 11% 2 7% 5% 5% 4 4 5% 6% 30%	3040
	11th to 20th	Day	15% 9% 3 8% 5% 5% 5% 5% 6% 6% 32%	3040
	21st to end	Day	19% 7% 2 7% 6% 5% 5% 4 6% 6% 33%	3040
July	1st to 10th	Day	23% 7% 2 6% 4 4 4 4 6% 7% 32%	4961
	11th to 20th	Day	24% 10% 3 7% 6% 5% 4 4 5% 7% 25%	4760
	21st to end	Day	22% 10% 3 7% 5% 4 5% 5% 5% 6% 27%	4954
August	1st to 10th	Day	23% 9% 3 8% 6% 5% 5% 4 6% 7% 22%	4423
	11th to 20th	Day	21% 8% 3 7% 4 4 5% 3 5% 6% 33%	4308
	21st to end	Day	20% 9% 2 6% 3 4 4 3 5% 7% 37%	4349
September	1st to 10th	Day	28% 12% 4 7% 5% 3 3 3 4 4 26%	2280
	11th to 20th	Day	28% 12% 3 9% 5% 4 4 3 4 5% 22%	2280
	21st to end	Day	30% 14% 4 7% 4 3 3 3 4 5% 23%	2010
October	1st to 10th	Day	26% 19% 4 8% 4 4 4 3 3 5% 20%	1900
	11th to 20th	Day	31% 24% 6% 8% 4 3 3 2 3 3 12%	1853
	21st to end	Day	26% 25% 7% 9% 5% 3 4 2 3 3 13%	1862
November	1st to 10th	Day	27% 32% 9% 11% 4 3 2 1 2 2 7%	1566
	11th to 20th	Day	22% 27% 8% 16% 6% 5% 4 2 3 3 5%	1600
	21st to end	Day	20% 26% 9% 19% 7% 5% 2 2 3 2 6%	1443
December	1st to 10th	Day	9% 21% 10% 19% 10% 7% 5% 4 3 4 9%	2130
	11th to 20th	Day	10% 21% 7% 15% 10% 10% 9% 4 2 2 9%	2253
	21st to end	Day	16% 19% 8% 16% 10% 11% 5% 3 4 2 4	2992
January	1st to 10th	Night	8% 23% 11% 21% 9% 8% 7% 4 4 3 3	6828
	11th to 20th	Night	7% 18% 10% 22% 11% 8% 7% 5% 7% 2 3	6772
	21st to end	Night	6% 11% 4 13% 11% 12% 12% 9% 8% 5% 10%	7111
February	1st to 10th	Night	6% 13% 5% 13% 11% 11% 12% 9% 7% 5% 10%	2730
	11th to 20th	Night	7% 18% 5% 12% 9% 9% 9% 8% 8% 5% 10%	2533
	21st to end	Night	8% 14% 5% 12% 9% 10% 8% 7% 6% 6% 16%	2048
March	1st to 10th	Night	13% 16% 5% 10% 7% 7% 7% 7% 7% 5% 18%	3724
	11th to 20th	Night	10% 15% 7% 18% 12% 8% 6% 3 3 3 14%	3520
	21st to end	Night	12% 13% 5% 15% 8% 7% 6% 5% 6% 4 19%	3594
April	1st to 10th	Night	15% 15% 4 10% 6% 5% 5% 3 4 5% 28%	1900
	11th to 20th	Night	11% 14% 5% 12% 7% 5% 5% 3 5% 5% 27%	1818
	21st to end	Night	14% 14% 4 10% 7% 4 5% 2 4 5% 31%	1520
May	1st to 10th	Night	18% 15% 6% 10% 4 3 3 3 4 6% 29%	2514
	11th to 20th	Night	14% 13% 4 7% 6% 4 5% 3 6% 6% 32%	2495
	21st to end	Night	18% 10% 4 9% 5% 5% 4 4 6% 8% 27%	2443
June	1st to 10th	Night	24% 10% 2 6% 4 4 3 4 4 5% 35%	1140
	11th to 20th	Night	15% 9% 3 6% 5% 5% 5% 5% 6% 6% 36%	1140
	21st to end	Night	15% 8% 3 6% 4 4 4 4 6% 10% 37%	1140
July	1st to 10th	Night	22% 10% 2 6% 4 5% 4 2 5% 6% 34%	2012
	11th to 20th	Night	18% 10% 3 7% 5% 5% 5% 4 6% 6% 31%	2210
	21st to end	Night	22% 9% 3 7% 5% 3 5% 4 6% 8% 27%	2603
August	1st to 10th	Night	17% 10% 3 7% 4 4 5% 4 5% 8% 31%	2506
	11th to 20th	Night	20% 8% 2 6% 4 5% 4 3 5% 6% 38%	2520
	21st to end	Night	20% 8% 2 7% 3 4 3 3 4 6% 40%	3275
September	1st to 10th	Night	23% 11% 4 7% 5% 4 4 3 6% 6% 26%	1900
	11th to 20th	Night	27% 13% 3 6% 4 4 3 3 4 5% 26%	1900
	21st to end	Night	27% 14% 3 7% 4 3 3 3 4 5% 27%	2165
October	1st to 10th	Night	24% 15% 4 7% 5% 4 4 3 4 5% 25%	2280
	11th to 20th	Night	30% 21% 5% 9% 4 4 3 3 3 3 14%	2327
	21st to end	Night	28% 21% 7% 11% 5% 4 3 2 3 4 12%	2731
November	1st to 10th	Night	28% 23% 7% 12% 5% 4 3 2 3 3 10%	2732
	11th to 20th	Night	23% 25% 9% 18% 7% 4 3 2 2 3 7%	2800
	21st to end	Night	17% 25% 9% 18% 9% 6% 4 3 2 2 5%	2955
December	1st to 10th	Night	8% 21% 10% 22% 10% 9% 6% 4 3 2 6%	5060
	11th to 20th	Night	12% 18% 7% 15% 11% 9% 8% 5% 3 3 9%	5969
	21st to end	Night	14% 18% 8% 17% 11% 10% 6% 4 4 3 6%	8008

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	87% 2 5% 5% 1	3137
	11th to 20th	Day	83% 2 3 8% 4	3160
	21st to end	Day	71% 4 5% 12% 9%	3849
February	1st to 10th	Day	69% 6% 6% 12% 7%	1666
	11th to 20th	Day	72% 4 8% 11% 5%	1762
	21st to end	Day	65% 4 8% 14% 8%	1501
March	1st to 10th	Day	68% 5% 7% 13% 8%	3119
	11th to 20th	Day	73% 4 6% 12% 5%	3438
	21st to end	Day	71% 4 6% 11% 8%	4038
April	1st to 10th	Day	66% 4 6% 14% 8% 3	2280
	11th to 20th	Day	58% 4 8% 20% 10%	2328
	21st to end	Day	60% 4 5% 17% 13% 1	2659
May	1st to 10th	Day	58% 6% 6% 20% 9% 1	4440
	11th to 20th	Day	58% 7% 8% 19% 8%	4402
	21st to end	Day	51% 6% 8% 20% 13% 2	5139
June	1st to 10th	Day	54% 5% 9% 19% 11% 1	3040
	11th to 20th	Day	51% 7% 9% 20% 12% 1	3040
	21st to end	Day	50% 6% 10% 20% 13% 1	3040
July	1st to 10th	Day	51% 5% 10% 25% 9%	4885
	11th to 20th	Day	57% 7% 10% 14% 11% 1	4679
	21st to end	Day	57% 6% 10% 21% 6%	4797
August	1st to 10th	Day	60% 7% 16% 14% 3	4409
	11th to 20th	Day	51% 5% 12% 27% 6%	4350
	21st to end	Day	48% 5% 12% 26% 9%	4349
September	1st to 10th	Day	62% 5% 11% 19% 4	2280
	11th to 20th	Day	64% 7% 13% 13% 3	2280
	21st to end	Day	65% 4 11% 17% 3	2010
October	1st to 10th	Day	64% 5% 13% 14% 4	3160
	11th to 20th	Day	80% 4 6% 9% 1	3056
	21st to end	Day	84% 3 5% 5% 2	3050
November	1st to 10th	Day	88% 3 4 4 1	1566
	11th to 20th	Day	88% 3 5% 3 1	1600
	21st to end	Day	86% 3 5% 5% 1	1443
December	1st to 10th	Day	81% 4 6% 8% 1	2130
	11th to 20th	Day	83% 3 7% 6% 2	2253
	21st to end	Day	86% 2 4 6% 2	2992
January	1st to 10th	Night	87% 3 4 5% 1	6828
	11th to 20th	Night	83% 3 5% 6% 3	6820
	21st to end	Night	70% 4 7% 13% 6%	7111
February	1st to 10th	Night	71% 5% 6% 11% 8%	2730
	11th to 20th	Night	71% 4 8% 11% 6%	2535
	21st to end	Night	66% 6% 8% 12% 8%	2048
March	1st to 10th	Night	64% 4 6% 16% 10%	3734
	11th to 20th	Night	75% 4 4 11% 6%	3521
	21st to end	Night	65% 4 7% 12% 12%	3594
April	1st to 10th	Night	59% 4 7% 15% 13% 3	1900
	11th to 20th	Night	58% 6% 7% 18% 11% 1	1818
	21st to end	Night	57% 5% 7% 16% 14% 1	1520
May	1st to 10th	Night	56% 6% 6% 20% 10% 1	2520
	11th to 20th	Night	48% 9% 9% 23% 10% 1	2496
	21st to end	Night	52% 6% 11% 18% 12% 1	2444
June	1st to 10th	Night	49% 5% 9% 24% 10% 3	1140
	11th to 20th	Night	45% 6% 9% 23% 16% 1	1140
	21st to end	Night	42% 6% 14% 25% 14%	1140
July	1st to 10th	Night	52% 5% 9% 31% 3	1979
	11th to 20th	Night	51% 6% 13% 17% 11% 1	2168
	21st to end	Night	55% 7% 13% 22% 3	2520
August	1st to 10th	Night	50% 7% 19% 22% 2	2496
	11th to 20th	Night	48% 5% 11% 27% 8%	2544
	21st to end	Night	48% 5% 12% 27% 9%	3275
September	1st to 10th	Night	58% 6% 12% 19% 4	1900
	11th to 20th	Night	62% 6% 11% 18% 4	1900
	21st to end	Night	61% 5% 11% 19% 5%	2165
October	1st to 10th	Night	61% 5% 14% 17% 4	3800
	11th to 20th	Night	76% 3 12% 7% 1	3863
	21st to end	Night	79% 4 7% 8% 1	4493
November	1st to 10th	Night	82% 4 6% 6% 1	2732
	11th to 20th	Night	87% 3 5% 5% 1	2800
	21st to end	Night	87% 4 5% 4	2955
December	1st to 10th	Night	85% 3 4 5% 2	5060
	11th to 20th	Night	81% 3 7% 7% 2	5969
	21st to end	Night	84% 2 5% 6% 3	8008

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	18% 11% 38% 24% 7% 4	200
	11th to 20th	Day	16% 14% 31% 28% 7% 6%	200
	21st to end	Day	12% 12% 35% 30% 8% 4	220
February	1st to 10th	Day	9% 13% 44% 24% 7% 2	234
	11th to 20th	Day	11% 16% 39% 23% 10%	300
	21st to end	Day	16% 17% 41% 16% 8% 2	289
March	1st to 10th	Day	17% 16% 30% 23% 12% 3	460
	11th to 20th	Day	14% 14% 28% 28% 13% 2	460
	21st to end	Day	16% 17% 39% 18% 8% 2	506
April	1st to 10th	Day	15% 14% 34% 26% 8% 3	460
	11th to 20th	Day	21% 11% 35% 21% 9% 2	452
	21st to end	Day	22% 12% 35% 20% 7% 3	460
May	1st to 10th	Day	25% 13% 28% 23% 8% 2	463
	11th to 20th	Day	23% 13% 31% 24% 8% 1	487
	21st to end	Day	24% 14% 36% 20% 7%	701
June	1st to 10th	Day	27% 10% 28% 25% 8% 1	870
	11th to 20th	Day	23% 14% 28% 24% 9% 2	870
	21st to end	Day	23% 8% 29% 28% 9% 3	870
July	1st to 10th	Day	26% 12% 26% 24% 9% 2	792
	11th to 20th	Day	25% 10% 30% 24% 10% 1	668
	21st to end	Day	35% 7% 21% 20% 13% 4	620
August	1st to 10th	Day	32% 7% 27% 18% 12% 5%	486
	11th to 20th	Day	28% 9% 21% 21% 13% 7%	479
	21st to end	Day	29% 9% 26% 21% 11% 5%	539
September	1st to 10th	Day	35% 14% 27% 18% 5% 2	490
	11th to 20th	Day	30% 12% 32% 18% 7% 2	490
	21st to end	Day	36% 12% 22% 18% 8% 3	490
October	1st to 10th	Day	34% 12% 29% 18% 7%	490
	11th to 20th	Day	43% 12% 27% 13% 4 1	465
	21st to end	Day	34% 16% 27% 14% 7% 2	410
November	1st to 10th	Day	49% 14% 25% 11% 2	200
	11th to 20th	Day	29% 17% 31% 17% 6% 2	200
	21st to end	Day	33% 20% 24% 17% 5% 2	200
December	1st to 10th	Day	24% 14% 23% 28% 9% 3	200
	11th to 20th	Day	21% 15% 38% 19% 8% 2	200
	21st to end	Day	20% 16% 30% 22% 10% 2	220
January	1st to 10th	Night	20% 13% 30% 25% 10% 1	1003
	11th to 20th	Night	17% 13% 35% 23% 11% 2	1000
	21st to end	Night	12% 8% 33% 31% 13% 3	930
February	1st to 10th	Night	12% 10% 37% 29% 10% 3	800
	11th to 20th	Night	15% 10% 33% 30% 10% 2	783
	21st to end	Night	15% 12% 30% 26% 14% 3	647
March	1st to 10th	Night	14% 13% 31% 28% 12% 2	760
	11th to 20th	Night	15% 14% 34% 24% 9% 2	760
	21st to end	Night	19% 12% 34% 24% 8% 2	836
April	1st to 10th	Night	21% 10% 31% 27% 9% 1	760
	11th to 20th	Night	18% 14% 27% 28% 11% 2	694
	21st to end	Night	18% 11% 31% 29% 9% 2	380
May	1st to 10th	Night	27% 6% 29% 32% 6% 1	380
	11th to 20th	Night	19% 11% 28% 30% 11% 1	374
	21st to end	Night	24% 11% 34% 25% 5%	411
June	1st to 10th	Night	27% 6% 32% 27% 7% 1	380
	11th to 20th	Night	19% 11% 32% 29% 9% 1	380
	21st to end	Night	18% 6% 32% 32% 11% 1	380
July	1st to 10th	Night	26% 6% 26% 29% 12% 1	370
	11th to 20th	Night	21% 6% 30% 33% 9% 1	368
	21st to end	Night	27% 6% 21% 30% 15% 2	416
August	1st to 10th	Night	25% 4 20% 35% 16% 1	378
	11th to 20th	Night	27% 5% 19% 30% 16% 2	400
	21st to end	Night	28% 7% 22% 28% 13% 2	713
September	1st to 10th	Night	31% 7% 28% 23% 9% 1	760
	11th to 20th	Night	35% 10% 22% 25% 8%	760
	21st to end	Night	36% 8% 24% 22% 8% 1	760
October	1st to 10th	Night	33% 9% 27% 22% 8% 1	760
	11th to 20th	Night	42% 8% 25% 17% 6% 1	760
	21st to end	Night	40% 11% 23% 18% 8% 1	836
November	1st to 10th	Night	41% 13% 24% 15% 5% 1	780
	11th to 20th	Night	35% 13% 30% 19% 3 1	800
	21st to end	Night	30% 14% 32% 16% 6% 1	877
December	1st to 10th	Night	22% 15% 31% 23% 9% 1	985
	11th to 20th	Night	18% 14% 37% 23% 7% 1	1100
	21st to end	Night	21% 12% 33% 23% 9% 2	1210

Page generated at 2025-02-22 06:51:36. Version ac07

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