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 2024-02-10.

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	19% 13% 5% 9% 8% 4 6% 5% 5% 5% 21%	77545
	Night	16% 15% 6% 11% 9% 5% 6% 5% 5% 5% 17%	81459
Transparency	Day	66% 5% 8% 15% 7%	77234
	Night	70% 5% 7% 12% 6%	81306
Seeing	Day	26% 12% 29% 22% 9% 2	14763
	Night	24% 11% 30% 25% 9% 1	23332

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	14% 16% 5% 15% 16% 8% 6% 6% 5% 4 5%	2186
	11th to 20th	Day	7% 18% 7% 17% 16% 9% 7% 5% 6% 4 4	2210
	21st to end	Day	8% 16% 6% 13% 11% 5% 8% 7% 6% 6% 14%	2687
February	1st to 10th	Day	7% 9% 6% 12% 11% 7% 10% 13% 9% 4 10%	1573
	11th to 20th	Day	6% 16% 8% 13% 10% 6% 9% 9% 8% 6% 8%	1573
	21st to end	Day	6% 12% 7% 11% 11% 6% 8% 10% 9% 6% 15%	1381
March	1st to 10th	Day	10% 11% 5% 10% 10% 6% 10% 10% 7% 4 18%	1797
	11th to 20th	Day	11% 12% 7% 9% 10% 6% 9% 7% 5% 5% 19%	1952
	21st to end	Day	11% 14% 6% 9% 9% 5% 7% 7% 5% 6% 21%	2304
April	1st to 10th	Day	16% 16% 6% 12% 7% 5% 5% 4 4 6% 19%	2160
	11th to 20th	Day	13% 12% 4 11% 7% 4 5% 5% 5% 6% 29%	2204
	21st to end	Day	17% 13% 5% 7% 7% 3 5% 4 4 4 30%	2519
May	1st to 10th	Day	20% 13% 6% 8% 6% 2 4 4 4 5% 29%	2520
	11th to 20th	Day	18% 10% 4 7% 7% 3 4 4 4 6% 32%	2478
	21st to end	Day	18% 11% 4 9% 6% 3 5% 5% 5% 7% 27%	2887
June	1st to 10th	Day	22% 11% 2 5% 5% 4 4 5% 5% 6% 30%	2880
	11th to 20th	Day	15% 8% 3 7% 7% 4 6% 5% 6% 7% 32%	2880
	21st to end	Day	20% 7% 3 6% 6% 3 5% 5% 6% 6% 33%	2880
July	1st to 10th	Day	23% 8% 3 6% 5% 3 5% 5% 6% 8% 27%	2817
	11th to 20th	Day	22% 8% 4 6% 6% 3 5% 5% 6% 7% 27%	2700
	21st to end	Day	30% 10% 4 7% 6% 4 5% 5% 4 5% 21%	2828
August	1st to 10th	Day	29% 10% 3 6% 7% 3 5% 4 5% 5% 23%	2506
	11th to 20th	Day	25% 11% 4 7% 5% 3 5% 5% 5% 6% 25%	2458
	21st to end	Day	27% 10% 3 6% 5% 3 5% 4 5% 6% 26%	2475
September	1st to 10th	Day	27% 12% 4 6% 6% 3 4 4 4 4 27%	2160
	11th to 20th	Day	29% 12% 4 7% 6% 3 4 4 4 5% 21%	2160
	21st to end	Day	30% 14% 4 6% 6% 2 3 3 4 6% 23%	1905
October	1st to 10th	Day	27% 18% 5% 7% 5% 3 4 4 3 5% 20%	1800
	11th to 20th	Day	32% 23% 6% 7% 5% 2 4 2 3 3 12%	1756
	21st to end	Day	26% 23% 8% 9% 5% 3 4 2 3 3 13%	1764
November	1st to 10th	Day	27% 30% 9% 10% 5% 2 3 2 2 2 7%	1486
	11th to 20th	Day	23% 26% 9% 15% 7% 4 5% 3 2 3 4	1520
	21st to end	Day	20% 24% 9% 16% 9% 4 3 3 2 3 6%	1371
December	1st to 10th	Day	13% 18% 12% 19% 11% 6% 5% 5% 2 3 7%	1245
	11th to 20th	Day	12% 17% 8% 12% 12% 8% 9% 5% 3 3 11%	1433
	21st to end	Day	14% 16% 10% 14% 14% 9% 8% 4 3 2 6%	2090
January	1st to 10th	Night	10% 16% 8% 16% 12% 7% 10% 8% 6% 4 4	4768
	11th to 20th	Night	10% 15% 8% 18% 15% 7% 8% 6% 6% 3 4	4760
	21st to end	Night	8% 15% 7% 12% 11% 7% 9% 8% 7% 6% 9%	4971
February	1st to 10th	Night	7% 11% 6% 10% 12% 7% 12% 11% 8% 5% 10%	2588
	11th to 20th	Night	8% 16% 6% 11% 10% 6% 10% 10% 7% 5% 10%	2273
	21st to end	Night	7% 13% 5% 11% 10% 8% 9% 9% 6% 6% 17%	1875
March	1st to 10th	Night	8% 12% 5% 11% 8% 5% 8% 8% 7% 5% 21%	2150
	11th to 20th	Night	11% 13% 7% 12% 9% 7% 7% 6% 4 5% 18%	2006
	21st to end	Night	13% 13% 6% 10% 8% 6% 7% 6% 4 4 23%	2052
April	1st to 10th	Night	17% 14% 5% 9% 7% 4 5% 4 4 5% 25%	1800
	11th to 20th	Night	11% 12% 7% 10% 9% 4 5% 4 5% 6% 27%	1722
	21st to end	Night	15% 13% 5% 9% 8% 3 5% 3 4 5% 31%	1440
May	1st to 10th	Night	21% 11% 5% 7% 4 3 3 3 5% 7% 31%	1440
	11th to 20th	Night	16% 8% 4 6% 7% 3 5% 4 4 6% 37%	1415
	21st to end	Night	20% 10% 4 7% 5% 3 4 4 4 8% 29%	1385
June	1st to 10th	Night	24% 9% 3 5% 5% 2 3 4 4 5% 36%	1080
	11th to 20th	Night	15% 7% 3 5% 6% 3 6% 5% 6% 7% 37%	1080
	21st to end	Night	15% 6% 3 5% 5% 3 4 5% 5% 11% 37%	1080
July	1st to 10th	Night	22% 9% 3 6% 6% 4 5% 3 5% 5% 33%	1140
	11th to 20th	Night	20% 8% 3 6% 6% 4 5% 6% 6% 6% 31%	1260
	21st to end	Night	22% 9% 3 7% 6% 3 5% 5% 6% 7% 27%	1490
August	1st to 10th	Night	21% 9% 3 5% 5% 4 5% 6% 5% 8% 28%	1432
	11th to 20th	Night	24% 8% 3 5% 5% 4 5% 4 5% 6% 32%	1442
	21st to end	Night	23% 8% 3 7% 6% 4 5% 5% 4 7% 30%	1863
September	1st to 10th	Night	22% 10% 4 7% 6% 3 5% 4 6% 6% 27%	1800
	11th to 20th	Night	28% 13% 4 6% 5% 3 4 4 4 5% 25%	1800
	21st to end	Night	27% 14% 4 7% 4 2 3 3 4 5% 27%	2050
October	1st to 10th	Night	24% 15% 4 7% 5% 3 4 4 4 5% 25%	2160
	11th to 20th	Night	31% 20% 5% 8% 6% 3 4 4 3 3 14%	2204
	21st to end	Night	29% 19% 7% 10% 6% 3 3 3 3 4 13%	2587
November	1st to 10th	Night	28% 23% 7% 11% 6% 3 4 3 2 3 10%	2592
	11th to 20th	Night	24% 23% 11% 16% 8% 3 3 2 2 3 6%	2660
	21st to end	Night	18% 22% 10% 17% 11% 4 5% 3 2 3 6%	2807
December	1st to 10th	Night	13% 21% 11% 16% 11% 6% 6% 5% 3 3 5%	2930
	11th to 20th	Night	11% 16% 8% 15% 12% 6% 7% 6% 4 3 11%	3769
	21st to end	Night	11% 17% 10% 15% 14% 8% 7% 5% 4 3 7%	5588

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	83% 3 6% 7% 1	2187
	11th to 20th	Day	83% 3 3 8% 3	2210
	21st to end	Day	69% 4 5% 13% 9%	2687
February	1st to 10th	Day	67% 6% 7% 12% 8%	1573
	11th to 20th	Day	72% 4 7% 11% 6%	1582
	21st to end	Day	64% 4 9% 15% 7%	1381
March	1st to 10th	Day	65% 6% 8% 12% 9%	1800
	11th to 20th	Day	67% 4 7% 12% 9% 1	1952
	21st to end	Day	64% 4 8% 15% 7% 1	2304
April	1st to 10th	Day	69% 4 6% 12% 7% 2	2160
	11th to 20th	Day	57% 4 8% 20% 11%	2204
	21st to end	Day	60% 4 5% 17% 13% 1	2519
May	1st to 10th	Day	59% 3 5% 21% 10% 2	2520
	11th to 20th	Day	54% 5% 9% 22% 10% 1	2482
	21st to end	Day	57% 5% 8% 22% 7%	2887
June	1st to 10th	Day	54% 5% 9% 19% 11% 2	2880
	11th to 20th	Day	51% 7% 9% 20% 12% 1	2880
	21st to end	Day	50% 6% 10% 20% 13% 1	2880
July	1st to 10th	Day	54% 6% 10% 21% 9%	2741
	11th to 20th	Day	54% 8% 11% 19% 9%	2619
	21st to end	Day	66% 6% 9% 15% 3	2671
August	1st to 10th	Day	63% 7% 12% 16% 2	2492
	11th to 20th	Day	60% 7% 12% 16% 6%	2458
	21st to end	Day	60% 6% 11% 20% 4	2475
September	1st to 10th	Day	61% 5% 11% 19% 4	2160
	11th to 20th	Day	65% 6% 12% 13% 3	2160
	21st to end	Day	65% 4 11% 17% 3	1905
October	1st to 10th	Day	69% 5% 9% 11% 6%	1800
	11th to 20th	Day	79% 4 7% 8% 1 1	1756
	21st to end	Day	80% 4 6% 7% 3 1	1764
November	1st to 10th	Day	87% 3 4 4 2	1486
	11th to 20th	Day	89% 3 5% 2 1	1520
	21st to end	Day	86% 3 5% 6% 1	1371
December	1st to 10th	Day	85% 4 4 6% 1	1245
	11th to 20th	Day	77% 3 8% 9% 3	1433
	21st to end	Day	86% 2 4 5% 3	2090
January	1st to 10th	Night	81% 4 6% 8% 1	4768
	11th to 20th	Night	82% 4 5% 6% 3	4760
	21st to end	Night	72% 4 5% 12% 7%	4971
February	1st to 10th	Night	70% 5% 6% 11% 8%	2588
	11th to 20th	Night	72% 5% 7% 10% 6%	2275
	21st to end	Night	65% 6% 8% 12% 8%	1875
March	1st to 10th	Night	61% 5% 7% 16% 11%	2160
	11th to 20th	Night	69% 4 5% 11% 10% 1	2007
	21st to end	Night	64% 4 7% 16% 9%	2052
April	1st to 10th	Night	61% 4 7% 13% 12% 3	1800
	11th to 20th	Night	58% 6% 7% 18% 11% 1	1722
	21st to end	Night	56% 5% 7% 16% 14% 2	1440
May	1st to 10th	Night	54% 5% 7% 20% 13% 2	1440
	11th to 20th	Night	49% 6% 9% 22% 13% 2	1416
	21st to end	Night	54% 5% 8% 22% 11%	1386
June	1st to 10th	Night	49% 5% 9% 23% 10% 3	1080
	11th to 20th	Night	44% 6% 9% 22% 16% 2	1080
	21st to end	Night	41% 7% 14% 24% 14%	1080
July	1st to 10th	Night	54% 6% 10% 25% 5%	1107
	11th to 20th	Night	52% 7% 11% 23% 8%	1218
	21st to end	Night	57% 8% 14% 18% 3	1407
August	1st to 10th	Night	53% 9% 17% 19% 3	1422
	11th to 20th	Night	53% 8% 15% 17% 7%	1442
	21st to end	Night	55% 7% 13% 21% 5% 1	1863
September	1st to 10th	Night	57% 6% 12% 20% 4	1800
	11th to 20th	Night	63% 5% 11% 18% 4	1800
	21st to end	Night	61% 5% 10% 19% 5%	2050
October	1st to 10th	Night	61% 6% 13% 14% 5%	2160
	11th to 20th	Night	77% 5% 8% 8% 2 1	2204
	21st to end	Night	78% 4 6% 9% 2 1	2587
November	1st to 10th	Night	83% 4 6% 6% 2	2592
	11th to 20th	Night	88% 3 4 4 1	2660
	21st to end	Night	87% 4 5% 4	2807
December	1st to 10th	Night	85% 4 5% 5% 1	2930
	11th to 20th	Night	77% 4 6% 10% 2	3769
	21st to end	Night	84% 3 5% 5% 4 1	5588

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	16% 11% 40% 23% 7% 3	180
	11th to 20th	Day	17% 13% 32% 27% 6% 5%	180
	21st to end	Day	12% 13% 32% 30% 9% 4	198
February	1st to 10th	Day	10% 12% 43% 26% 7% 2	207
	11th to 20th	Day	13% 18% 41% 20% 9%	240
	21st to end	Day	15% 17% 42% 16% 9% 2	247
March	1st to 10th	Day	14% 15% 31% 25% 12% 3	420
	11th to 20th	Day	15% 15% 29% 28% 10% 2	420
	21st to end	Day	16% 16% 38% 20% 9% 2	462
April	1st to 10th	Day	16% 14% 34% 25% 8% 2	420
	11th to 20th	Day	19% 12% 35% 21% 10% 2	412
	21st to end	Day	23% 10% 34% 22% 8% 3	420
May	1st to 10th	Day	26% 12% 28% 22% 8% 2	423
	11th to 20th	Day	24% 11% 31% 24% 8% 2	447
	21st to end	Day	24% 13% 35% 20% 7%	647
June	1st to 10th	Day	28% 10% 27% 25% 9% 1	810
	11th to 20th	Day	21% 14% 28% 25% 9% 2	810
	21st to end	Day	22% 8% 28% 28% 10% 4	810
July	1st to 10th	Day	26% 12% 26% 24% 9% 2	736
	11th to 20th	Day	24% 11% 31% 24% 10% 1	618
	21st to end	Day	36% 6% 20% 21% 13% 4	572
August	1st to 10th	Day	33% 7% 24% 18% 13% 5%	446
	11th to 20th	Day	29% 9% 21% 20% 13% 7%	439
	21st to end	Day	31% 8% 26% 20% 11% 5%	495
September	1st to 10th	Day	33% 14% 27% 19% 6% 2	450
	11th to 20th	Day	31% 12% 32% 16% 6% 2	450
	21st to end	Day	37% 12% 23% 17% 8% 3	450
October	1st to 10th	Day	34% 12% 28% 18% 8%	450
	11th to 20th	Day	43% 11% 27% 13% 4 1	428
	21st to end	Day	33% 16% 26% 16% 7% 2	378
November	1st to 10th	Day	48% 13% 24% 12% 2	180
	11th to 20th	Day	31% 18% 29% 16% 5% 1	180
	21st to end	Day	33% 21% 24% 14% 5% 2	180
December	1st to 10th	Day	25% 13% 20% 30% 9% 3	180
	11th to 20th	Day	21% 14% 36% 20% 8% 2	180
	21st to end	Day	17% 17% 32% 22% 11% 2	198
January	1st to 10th	Night	20% 13% 30% 25% 11% 1	953
	11th to 20th	Night	17% 13% 35% 23% 10% 2	950
	21st to end	Night	13% 8% 32% 31% 14% 3	884
February	1st to 10th	Night	12% 10% 36% 30% 10% 2	759
	11th to 20th	Night	16% 11% 34% 29% 9% 1	703
	21st to end	Night	14% 11% 30% 27% 15% 4	592
March	1st to 10th	Night	14% 13% 31% 29% 12% 3	720
	11th to 20th	Night	16% 15% 36% 24% 8% 2	720
	21st to end	Night	19% 12% 34% 24% 8% 2	792
April	1st to 10th	Night	22% 10% 31% 27% 9% 1	720
	11th to 20th	Night	16% 14% 27% 28% 12% 2	658
	21st to end	Night	18% 9% 31% 29% 10% 3	360
May	1st to 10th	Night	28% 6% 28% 32% 6% 1	360
	11th to 20th	Night	19% 10% 28% 31% 11% 1	354
	21st to end	Night	24% 11% 33% 25% 6% 1	389
June	1st to 10th	Night	28% 7% 31% 27% 7% 1	360
	11th to 20th	Night	19% 10% 32% 30% 9% 1	360
	21st to end	Night	18% 5% 33% 33% 11% 1	360
July	1st to 10th	Night	25% 6% 26% 29% 13% 1	350
	11th to 20th	Night	22% 6% 30% 31% 9% 1	348
	21st to end	Night	26% 5% 21% 31% 15% 2	394
August	1st to 10th	Night	26% 3 18% 35% 16% 1	358
	11th to 20th	Night	28% 4 19% 31% 15% 2	378
	21st to end	Night	28% 7% 22% 28% 13% 2	675
September	1st to 10th	Night	29% 7% 29% 24% 9% 1	720
	11th to 20th	Night	36% 10% 22% 24% 7%	720
	21st to end	Night	37% 8% 24% 22% 8% 1	720
October	1st to 10th	Night	33% 9% 27% 22% 8%	720
	11th to 20th	Night	42% 8% 24% 18% 6% 2	720
	21st to end	Night	40% 10% 23% 19% 8% 1	792
November	1st to 10th	Night	41% 13% 24% 15% 5% 1	740
	11th to 20th	Night	35% 13% 30% 18% 3 1	760
	21st to end	Night	29% 15% 33% 16% 5% 1	829
December	1st to 10th	Night	22% 15% 31% 22% 9% 1	930
	11th to 20th	Night	17% 14% 36% 24% 7% 1	1040
	21st to end	Night	21% 12% 32% 23% 10% 2	1144

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