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 2026-07-01.

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% 6% 4 5% 5% 22%	137862
	Night	14% 15% 6% 13% 8% 7% 6% 4 5% 4 17%	134703
Transparency	Day	64% 4 8% 16% 7% 1	141239
	Night	69% 4 8% 13% 6%	139418
Seeing	Day	25% 13% 30% 21% 9% 2	18045
	Night	24% 11% 30% 25% 9% 1	26341

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% 19% 7% 21% 12% 10% 7% 4 4 2 3	4072
	11th to 20th	Day	4 17% 7% 20% 13% 11% 6% 6% 8% 3 4	4083
	21st to end	Day	4 10% 4 13% 11% 12% 12% 10% 9% 5% 10%	4987
February	1st to 10th	Day	5% 12% 5% 14% 10% 9% 12% 10% 8% 4 9%	1750
	11th to 20th	Day	5% 17% 6% 14% 10% 9% 9% 8% 8% 5% 9%	1843
	21st to end	Day	6% 13% 6% 12% 10% 8% 9% 7% 9% 7% 13%	1615
March	1st to 10th	Day	13% 15% 5% 12% 7% 8% 7% 6% 7% 5% 14%	4576
	11th to 20th	Day	11% 16% 7% 16% 10% 8% 7% 4 5% 5% 11%	5032
	21st to end	Day	9% 15% 5% 14% 8% 8% 10% 4 6% 6% 16%	5914
April	1st to 10th	Day	15% 16% 5% 14% 6% 6% 5% 3 4 5% 21%	2520
	11th to 20th	Day	14% 13% 5% 12% 7% 5% 4 3 5% 5% 27%	2576
	21st to end	Day	17% 14% 5% 9% 6% 5% 4 3 5% 4 29%	2939
May	1st to 10th	Day	15% 19% 7% 11% 4 4 4 3 4 4 27%	8237
	11th to 20th	Day	15% 14% 5% 9% 5% 5% 5% 3 5% 6% 28%	8221
	21st to end	Day	16% 12% 4 8% 4 4 4 3 5% 5% 34%	9628
June	1st to 10th	Day	21% 11% 2 7% 5% 5% 4 4 5% 6% 31%	3360
	11th to 20th	Day	16% 9% 3 8% 5% 6% 5% 5% 6% 6% 31%	3360
	21st to end	Day	19% 8% 2 7% 5% 5% 5% 4 6% 6% 33%	3360
July	1st to 10th	Day	22% 8% 2 7% 5% 5% 5% 4 6% 7% 30%	7105
	11th to 20th	Day	22% 10% 3 8% 6% 5% 5% 4 5% 7% 25%	6820
	21st to end	Day	20% 10% 3 8% 6% 5% 6% 5% 6% 6% 27%	7136
August	1st to 10th	Day	23% 9% 3 8% 6% 5% 5% 4 6% 7% 23%	4563
	11th to 20th	Day	21% 9% 3 7% 4 4 5% 3 6% 6% 33%	4446
	21st to end	Day	20% 9% 2 6% 3 4 4 3 5% 7% 36%	4486
September	1st to 10th	Day	28% 12% 4 7% 5% 3 4 3 4 4 26%	2400
	11th to 20th	Day	28% 13% 3 9% 5% 4 4 3 4 5% 23%	2400
	21st to end	Day	29% 14% 4 7% 4 3 3 3 5% 6% 23%	2116
October	1st to 10th	Day	25% 19% 5% 7% 4 4 4 3 3 5% 20%	2000
	11th to 20th	Day	31% 23% 6% 8% 4 3 3 2 3 3 13%	1950
	21st to end	Day	26% 24% 7% 9% 5% 3 4 2 2 3 14%	1960
November	1st to 10th	Day	26% 32% 9% 11% 4 3 2 1 2 2 7%	1646
	11th to 20th	Day	21% 28% 8% 17% 6% 5% 4 2 3 3 4	1680
	21st to end	Day	20% 26% 9% 19% 7% 5% 2 2 3 2 6%	1515
December	1st to 10th	Day	8% 21% 10% 19% 10% 7% 5% 4 3 4 9%	2195
	11th to 20th	Day	10% 22% 7% 15% 10% 10% 9% 4 2 2 8%	2313
	21st to end	Day	16% 19% 8% 16% 10% 11% 5% 3 4 2 5%	3058
January	1st to 10th	Night	7% 21% 10% 21% 10% 10% 8% 4 4 2 2	8851
	11th to 20th	Night	6% 16% 9% 22% 12% 8% 6% 6% 6% 3 7%	8832
	21st to end	Night	4 9% 4 13% 13% 14% 13% 8% 9% 5% 8%	9200
February	1st to 10th	Night	6% 12% 5% 13% 11% 11% 11% 9% 7% 5% 9%	2866
	11th to 20th	Night	7% 18% 5% 13% 9% 9% 9% 8% 7% 5% 11%	2663
	21st to end	Night	7% 14% 5% 12% 9% 10% 8% 7% 6% 6% 16%	2191
March	1st to 10th	Night	11% 16% 5% 10% 6% 7% 8% 7% 9% 6% 15%	5484
	11th to 20th	Night	15% 15% 8% 17% 10% 7% 5% 5% 5% 3 12%	5145
	21st to end	Night	10% 12% 5% 13% 7% 8% 9% 5% 6% 4 20%	5260
April	1st to 10th	Night	14% 15% 4 10% 7% 6% 5% 3 4 5% 26%	2100
	11th to 20th	Night	12% 14% 5% 12% 7% 5% 5% 3 5% 5% 27%	2012
	21st to end	Night	14% 13% 4 10% 6% 4 5% 2 4 5% 31%	1680
May	1st to 10th	Night	18% 17% 7% 12% 5% 3 3 2 3 4 27%	4660
	11th to 20th	Night	15% 13% 4 9% 5% 4 4 3 5% 6% 31%	4639
	21st to end	Night	20% 13% 4 8% 4 3 3 3 4 6% 32%	4559
June	1st to 10th	Night	23% 10% 2 6% 4 4 3 4 5% 5% 36%	1260
	11th to 20th	Night	15% 9% 3 6% 5% 5% 5% 4 6% 7% 35%	1260
	21st to end	Night	16% 8% 3 6% 4 3 4 3 6% 9% 37%	1260
July	1st to 10th	Night	20% 11% 2 6% 4 5% 4 2 5% 6% 35%	2884
	11th to 20th	Night	20% 10% 3 7% 5% 5% 5% 4 6% 6% 29%	3160
	21st to end	Night	21% 8% 2 6% 5% 3 4 4 5% 8% 33%	3725
August	1st to 10th	Night	17% 10% 3 7% 4 4 5% 4 6% 8% 31%	2586
	11th to 20th	Night	21% 8% 2 6% 4 5% 4 3 5% 6% 37%	2601
	21st to end	Night	21% 8% 2 7% 4 4 4 3 4 6% 39%	3379
September	1st to 10th	Night	23% 11% 4 7% 5% 4 4 3 6% 6% 27%	2000
	11th to 20th	Night	27% 13% 3 6% 4 4 4 3 4 5% 27%	2000
	21st to end	Night	26% 15% 3 8% 4 3 3 2 4 5% 27%	2279
October	1st to 10th	Night	23% 15% 4 7% 5% 4 4 3 4 6% 25%	2400
	11th to 20th	Night	30% 21% 5% 9% 4 4 4 2 3 3 15%	2450
	21st to end	Night	28% 20% 7% 11% 5% 4 3 2 3 4 13%	2875
November	1st to 10th	Night	27% 24% 7% 13% 5% 4 3 2 3 3 10%	2872
	11th to 20th	Night	22% 25% 9% 18% 7% 4 3 2 2 3 7%	2940
	21st to end	Night	17% 25% 9% 18% 9% 6% 4 2 2 2 5%	3103
December	1st to 10th	Night	8% 20% 10% 22% 11% 9% 6% 4 3 2 5%	5214
	11th to 20th	Night	12% 19% 7% 16% 11% 9% 8% 5% 3 3 9%	6129
	21st to end	Night	14% 18% 8% 17% 11% 10% 6% 4 4 3 6%	8184

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	88% 2 4 5% 1	4073
	11th to 20th	Day	80% 2 3 10% 5%	4110
	21st to end	Day	70% 4 7% 12% 8%	4987
February	1st to 10th	Day	70% 6% 6% 11% 7%	1750
	11th to 20th	Day	71% 4 8% 12% 6%	1852
	21st to end	Day	65% 4 8% 15% 8%	1615
March	1st to 10th	Day	69% 4 5% 11% 9% 2	4579
	11th to 20th	Day	75% 4 6% 10% 5%	5032
	21st to end	Day	69% 3 5% 13% 9% 1	5914
April	1st to 10th	Day	67% 3 6% 13% 8% 2	2520
	11th to 20th	Day	59% 4 7% 19% 10% 1	2576
	21st to end	Day	60% 4 5% 18% 12% 1	2939
May	1st to 10th	Day	62% 4 5% 16% 12% 1	8249
	11th to 20th	Day	56% 5% 9% 23% 6%	8225
	21st to end	Day	51% 4 6% 21% 15% 2	9629
June	1st to 10th	Day	53% 5% 8% 20% 12% 1	3360
	11th to 20th	Day	52% 7% 9% 19% 12% 1	3360
	21st to end	Day	51% 6% 9% 20% 13% 1	3360
July	1st to 10th	Day	52% 5% 11% 23% 8%	7030
	11th to 20th	Day	57% 6% 10% 17% 9%	6739
	21st to end	Day	56% 6% 11% 21% 5%	6933
August	1st to 10th	Day	59% 7% 16% 15% 3	4549
	11th to 20th	Day	51% 5% 12% 26% 5%	4488
	21st to end	Day	48% 5% 13% 26% 9%	4486
September	1st to 10th	Day	62% 5% 11% 19% 4	2400
	11th to 20th	Day	64% 6% 13% 13% 3	2400
	21st to end	Day	64% 4 11% 17% 3	2116
October	1st to 10th	Day	63% 5% 13% 15% 4	3260
	11th to 20th	Day	80% 3 6% 9% 1	3153
	21st to end	Day	83% 3 5% 6% 2	3148
November	1st to 10th	Day	88% 3 4 4 1	1646
	11th to 20th	Day	88% 3 5% 3 1	1680
	21st to end	Day	86% 3 5% 5% 1	1515
December	1st to 10th	Day	81% 4 6% 8% 1	2195
	11th to 20th	Day	83% 3 7% 5% 2	2313
	21st to end	Day	86% 2 4 6% 2	3058
January	1st to 10th	Night	89% 3 3 5% 1	8851
	11th to 20th	Night	79% 3 5% 9% 4	8880
	21st to end	Night	72% 4 7% 12% 5%	9200
February	1st to 10th	Night	71% 5% 6% 10% 8%	2866
	11th to 20th	Night	71% 4 8% 11% 6%	2665
	21st to end	Night	66% 6% 8% 13% 8%	2191
March	1st to 10th	Night	63% 4 6% 14% 12%	5494
	11th to 20th	Night	76% 3 4 11% 5% 1	5146
	21st to end	Night	64% 3 6% 14% 12% 1	5260
April	1st to 10th	Night	60% 4 7% 14% 12% 2	2100
	11th to 20th	Night	58% 6% 7% 18% 10% 1	2012
	21st to end	Night	56% 5% 6% 19% 13% 1	1680
May	1st to 10th	Night	62% 4 4 17% 12% 1	4666
	11th to 20th	Night	53% 6% 10% 23% 8% 1	4640
	21st to end	Night	53% 4 8% 21% 12% 1	4560
June	1st to 10th	Night	48% 5% 8% 24% 12% 3	1260
	11th to 20th	Night	46% 6% 9% 22% 15% 2	1260
	21st to end	Night	43% 6% 13% 24% 13%	1260
July	1st to 10th	Night	51% 4 10% 31% 4	2851
	11th to 20th	Night	53% 6% 12% 19% 9% 1	3118
	21st to end	Night	50% 6% 14% 26% 3	3614
August	1st to 10th	Night	50% 7% 19% 23% 2	2576
	11th to 20th	Night	49% 5% 11% 26% 8%	2625
	21st to end	Night	49% 5% 12% 26% 8%	3379
September	1st to 10th	Night	58% 6% 13% 19% 4	2000
	11th to 20th	Night	61% 5% 12% 18% 4	2000
	21st to end	Night	61% 5% 10% 19% 5%	2279
October	1st to 10th	Night	61% 5% 14% 17% 4	3920
	11th to 20th	Night	75% 3 12% 7% 2	3986
	21st to end	Night	78% 4 7% 9% 1	4637
November	1st to 10th	Night	83% 4 6% 6% 1	2872
	11th to 20th	Night	87% 3 4 5% 1	2940
	21st to end	Night	88% 4 5% 4	3103
December	1st to 10th	Night	86% 3 4 5% 2	5214
	11th to 20th	Night	82% 3 7% 7% 1	6129
	21st to end	Night	84% 2 5% 6% 3	8184

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% 12% 38% 23% 6% 3	220
	11th to 20th	Day	15% 13% 30% 30% 8% 5%	220
	21st to end	Day	11% 12% 35% 30% 9% 3	242
February	1st to 10th	Day	9% 13% 42% 26% 8% 2	258
	11th to 20th	Day	11% 15% 42% 23% 9%	330
	21st to end	Day	15% 17% 40% 18% 9% 2	331
March	1st to 10th	Day	17% 17% 31% 23% 11% 2	540
	11th to 20th	Day	15% 14% 29% 28% 11% 2	540
	21st to end	Day	14% 17% 41% 19% 7% 2	594
April	1st to 10th	Day	17% 16% 34% 24% 7% 2	540
	11th to 20th	Day	22% 13% 35% 20% 9% 2	532
	21st to end	Day	24% 12% 35% 20% 7% 3	540
May	1st to 10th	Day	25% 16% 27% 22% 7% 2	543
	11th to 20th	Day	24% 13% 32% 22% 8% 1	567
	21st to end	Day	24% 14% 35% 19% 8% 1	808
June	1st to 10th	Day	27% 11% 28% 25% 8% 1	990
	11th to 20th	Day	24% 14% 27% 24% 9% 2	990
	21st to end	Day	23% 9% 28% 26% 11% 4	990
July	1st to 10th	Day	26% 12% 27% 24% 9% 2	849
	11th to 20th	Day	25% 11% 31% 24% 9% 1	718
	21st to end	Day	34% 8% 23% 19% 12% 4	669
August	1st to 10th	Day	31% 8% 26% 18% 12% 5%	526
	11th to 20th	Day	28% 11% 22% 21% 12% 7%	519
	21st to end	Day	29% 9% 26% 21% 10% 4	583
September	1st to 10th	Day	35% 13% 27% 18% 5% 2	530
	11th to 20th	Day	30% 11% 32% 18% 8% 2	530
	21st to end	Day	36% 13% 22% 17% 8% 3	530
October	1st to 10th	Day	33% 12% 29% 18% 7%	530
	11th to 20th	Day	43% 11% 28% 13% 4 1	502
	21st to end	Day	34% 15% 27% 14% 7% 2	442
November	1st to 10th	Day	47% 15% 25% 11% 2	220
	11th to 20th	Day	28% 18% 30% 17% 5% 1	220
	21st to end	Day	32% 20% 25% 15% 5% 2	220
December	1st to 10th	Day	23% 16% 24% 26% 8% 3	220
	11th to 20th	Day	20% 15% 36% 19% 8% 2	220
	21st to end	Day	19% 18% 31% 21% 9% 2	242
January	1st to 10th	Night	20% 14% 30% 25% 10% 1	1053
	11th to 20th	Night	16% 13% 35% 23% 11% 2	1050
	21st to end	Night	12% 8% 34% 31% 13% 3	976
February	1st to 10th	Night	11% 10% 36% 30% 11% 2	840
	11th to 20th	Night	14% 10% 34% 30% 10% 2	823
	21st to end	Night	14% 12% 30% 27% 14% 3	692
March	1st to 10th	Night	14% 14% 30% 28% 11% 2	840
	11th to 20th	Night	16% 14% 35% 24% 9% 2	840
	21st to end	Night	18% 12% 35% 25% 8% 2	924
April	1st to 10th	Night	21% 11% 32% 26% 9% 1	840
	11th to 20th	Night	18% 14% 27% 28% 11% 2	768
	21st to end	Night	19% 10% 30% 29% 10% 2	420
May	1st to 10th	Night	26% 7% 29% 30% 7% 1	420
	11th to 20th	Night	19% 11% 30% 29% 11% 1	414
	21st to end	Night	25% 11% 33% 25% 6%	455
June	1st to 10th	Night	27% 6% 32% 28% 7%	420
	11th to 20th	Night	19% 10% 31% 29% 10% 1	420
	21st to end	Night	19% 6% 31% 32% 11% 1	420
July	1st to 10th	Night	26% 7% 26% 28% 12% 1	390
	11th to 20th	Night	22% 6% 31% 32% 9% 1	388
	21st to end	Night	26% 5% 23% 30% 15% 2	438
August	1st to 10th	Night	25% 4 19% 34% 16% 1	398
	11th to 20th	Night	28% 5% 20% 30% 16% 2	421
	21st to end	Night	29% 7% 22% 28% 12% 2	751
September	1st to 10th	Night	32% 7% 28% 23% 9% 1	800
	11th to 20th	Night	35% 11% 22% 25% 8%	800
	21st to end	Night	37% 9% 24% 21% 8% 1	800
October	1st to 10th	Night	32% 10% 28% 22% 8% 1	800
	11th to 20th	Night	42% 9% 25% 18% 5% 1	800
	21st to end	Night	39% 11% 22% 19% 8% 1	880
November	1st to 10th	Night	40% 14% 25% 15% 5% 1	820
	11th to 20th	Night	34% 13% 30% 19% 3 1	840
	21st to end	Night	30% 15% 32% 16% 6% 1	925
December	1st to 10th	Night	21% 16% 32% 22% 8% 1	1039
	11th to 20th	Night	18% 15% 36% 23% 7% 1	1160
	21st to end	Night	21% 12% 33% 23% 9% 2	1276

Page generated at 2026-06-28 02:10:49. Version ac07

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