Chibougamau
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chibougamau clear sky chart from 2005-11-06 to 2025-10-19.

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% 13% 5% 11% 7% 6% 5% 4 5% 6% 22%	127506
	Night	16% 14% 5% 12% 7% 6% 5% 4 5% 5% 20%	122225
Transparency	Day	61% 6% 9% 16% 7% 1	130882
	Night	66% 5% 9% 14% 6%	126939
Seeing	Day	23% 13% 30% 22% 10% 3	16700
	Night	23% 11% 29% 26% 10% 1	24569

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% 22% 9% 22% 11% 7% 5% 3 3 3 5%	3597
	11th to 20th	Day	8% 14% 8% 18% 14% 10% 8% 4 7% 4 5%	3570
	21st to end	Day	5% 10% 5% 20% 9% 7% 8% 8% 8% 7% 13%	3960
February	1st to 10th	Day	6% 13% 5% 14% 11% 10% 9% 6% 7% 6% 13%	1648
	11th to 20th	Day	9% 16% 5% 18% 9% 6% 7% 7% 6% 6% 10%	1753
	21st to end	Day	7% 16% 7% 12% 10% 8% 7% 4 6% 7% 16%	1636
March	1st to 10th	Day	14% 18% 6% 15% 6% 4 4 4 5% 4 20%	4476
	11th to 20th	Day	17% 17% 6% 15% 11% 7% 5% 3 4 4 12%	4745
	21st to end	Day	9% 15% 6% 15% 7% 8% 7% 3 4 5% 20%	5920
April	1st to 10th	Day	16% 17% 6% 12% 6% 5% 4 3 4 5% 23%	2400
	11th to 20th	Day	17% 11% 4 12% 5% 5% 5% 3 5% 6% 26%	2400
	21st to end	Day	17% 14% 4 12% 6% 5% 4 3 4 6% 26%	2745
May	1st to 10th	Day	16% 12% 5% 8% 5% 5% 4 3 5% 6% 32%	6346
	11th to 20th	Day	21% 10% 3 9% 6% 4 5% 4 5% 6% 26%	6318
	21st to end	Day	16% 10% 3 9% 5% 5% 5% 4 5% 6% 33%	7036
June	1st to 10th	Day	21% 10% 4 8% 6% 4 5% 4 5% 7% 27%	3000
	11th to 20th	Day	17% 9% 3 7% 6% 5% 5% 4 7% 7% 29%	3194
	21st to end	Day	20% 8% 3 8% 6% 5% 6% 4 6% 7% 28%	3200
July	1st to 10th	Day	19% 8% 3 8% 5% 6% 5% 5% 6% 8% 26%	6970
	11th to 20th	Day	17% 7% 2 7% 5% 6% 6% 5% 7% 9% 29%	6370
	21st to end	Day	18% 7% 2 7% 5% 5% 6% 5% 7% 9% 29%	6926
August	1st to 10th	Day	18% 8% 4 8% 6% 5% 7% 5% 7% 8% 23%	4563
	11th to 20th	Day	18% 9% 3 8% 5% 5% 5% 4 6% 8% 31%	4499
	21st to end	Day	15% 8% 3 6% 4 4 5% 4 6% 8% 37%	4323
September	1st to 10th	Day	23% 10% 3 9% 5% 5% 5% 3 4 6% 27%	2400
	11th to 20th	Day	20% 12% 3 9% 5% 5% 5% 4 5% 7% 26%	2353
	21st to end	Day	24% 13% 3 8% 4 4 4 3 4 5% 28%	2195
October	1st to 10th	Day	23% 12% 5% 8% 5% 4 4 3 4 6% 27%	2000
	11th to 20th	Day	29% 21% 5% 10% 5% 4 4 2 3 3 14%	1896
	21st to end	Day	27% 18% 7% 12% 6% 5% 3 2 2 5% 12%	1881
November	1st to 10th	Day	21% 26% 7% 13% 6% 3 3 2 3 3 13%	1681
	11th to 20th	Day	21% 24% 8% 14% 8% 4 4 2 3 3 9%	1600
	21st to end	Day	20% 26% 9% 17% 7% 5% 4 2 3 2 4	1460
December	1st to 10th	Day	11% 22% 10% 19% 8% 11% 4 3 3 3 6%	2280
	11th to 20th	Day	14% 17% 8% 16% 9% 8% 9% 3 4 3 8%	2618
	21st to end	Day	15% 18% 9% 14% 9% 9% 6% 4 4 5% 7%	3547
January	1st to 10th	Night	12% 22% 10% 21% 8% 8% 5% 3 3 3 6%	6349
	11th to 20th	Night	8% 17% 8% 22% 11% 8% 7% 4 6% 4 6%	6315
	21st to end	Night	5% 11% 7% 16% 8% 10% 9% 7% 8% 5% 14%	6996
February	1st to 10th	Night	7% 13% 5% 11% 9% 10% 10% 7% 7% 6% 13%	2750
	11th to 20th	Night	8% 19% 6% 14% 10% 7% 8% 6% 5% 5% 12%	2533
	21st to end	Night	8% 15% 5% 14% 10% 6% 6% 6% 6% 6% 18%	1993
March	1st to 10th	Night	13% 15% 5% 12% 6% 5% 5% 6% 6% 5% 20%	5364
	11th to 20th	Night	16% 17% 6% 15% 8% 6% 6% 4 5% 5% 14%	5211
	21st to end	Night	13% 15% 5% 12% 5% 5% 7% 4 5% 4 25%	5011
April	1st to 10th	Night	16% 15% 5% 10% 7% 5% 5% 3 4 5% 25%	2000
	11th to 20th	Night	13% 13% 5% 10% 6% 5% 4 4 4 6% 30%	1947
	21st to end	Night	18% 11% 5% 9% 6% 4 4 3 4 4 32%	1672
May	1st to 10th	Night	17% 12% 3 8% 5% 4 4 3 5% 5% 34%	3594
	11th to 20th	Night	24% 13% 4 7% 4 4 4 3 4 5% 28%	3575
	21st to end	Night	20% 12% 3 9% 4 4 4 3 5% 6% 29%	3838
June	1st to 10th	Night	22% 9% 2 8% 5% 4 4 4 5% 6% 30%	1400
	11th to 20th	Night	18% 8% 3 9% 4 4 5% 4 6% 7% 31%	1200
	21st to end	Night	18% 7% 3 7% 5% 5% 4 4 6% 6% 36%	1200
July	1st to 10th	Night	19% 10% 3 9% 5% 5% 4 4 4 6% 30%	2998
	11th to 20th	Night	21% 8% 3 8% 5% 5% 4 3 5% 7% 30%	3588
	21st to end	Night	16% 5% 2 6% 4 4 5% 4 6% 8% 38%	3926
August	1st to 10th	Night	17% 6% 3 7% 5% 4 5% 5% 6% 8% 34%	2586
	11th to 20th	Night	15% 8% 3 7% 5% 4 4 4 6% 7% 35%	2550
	21st to end	Night	16% 8% 2 7% 5% 4 4 4 5% 7% 38%	3538
September	1st to 10th	Night	23% 8% 3 7% 5% 5% 4 3 4 6% 33%	2000
	11th to 20th	Night	21% 10% 3 8% 5% 4 5% 3 5% 6% 29%	2046
	21st to end	Night	21% 11% 3 8% 5% 5% 3 3 4 5% 32%	2202
October	1st to 10th	Night	20% 12% 4 7% 4 4 5% 4 5% 6% 30%	2400
	11th to 20th	Night	27% 18% 5% 9% 5% 4 4 3 4 4 17%	2460
	21st to end	Night	29% 18% 6% 10% 5% 4 4 3 3 4 14%	2717
November	1st to 10th	Night	25% 22% 7% 13% 5% 5% 4 3 3 3 11%	2617
	11th to 20th	Night	18% 21% 7% 16% 8% 5% 5% 3 4 3 10%	2800
	21st to end	Night	18% 26% 9% 16% 9% 6% 4 3 2 2 6%	2938
December	1st to 10th	Night	11% 19% 8% 21% 11% 9% 5% 3 3 3 6%	4910
	11th to 20th	Night	17% 17% 7% 13% 10% 9% 6% 4 5% 4 10%	5591
	21st to end	Night	15% 16% 6% 17% 10% 9% 6% 3 4 4 10%	7410

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	86% 2 4 7% 1	3598
	11th to 20th	Day	80% 5% 3 5% 7%	3600
	21st to end	Day	65% 4 7% 14% 9%	3960
February	1st to 10th	Day	68% 5% 5% 13% 8%	1648
	11th to 20th	Day	72% 5% 7% 9% 6%	1762
	21st to end	Day	66% 5% 7% 12% 8% 1	1636
March	1st to 10th	Day	67% 4 4 13% 12% 1	4479
	11th to 20th	Day	74% 6% 5% 9% 5% 1	4745
	21st to end	Day	66% 5% 5% 11% 11% 2	5920
April	1st to 10th	Day	64% 5% 8% 13% 8% 1	2400
	11th to 20th	Day	58% 6% 9% 16% 11% 1	2400
	21st to end	Day	59% 6% 7% 15% 12% 1	2745
May	1st to 10th	Day	52% 8% 8% 16% 13% 3	6357
	11th to 20th	Day	56% 8% 10% 19% 7% 1	6322
	21st to end	Day	49% 7% 9% 20% 13% 2	7036
June	1st to 10th	Day	55% 6% 8% 19% 11%	3000
	11th to 20th	Day	51% 7% 10% 17% 12% 2	3194
	21st to end	Day	53% 8% 10% 18% 10%	3200
July	1st to 10th	Day	53% 7% 13% 21% 5%	6897
	11th to 20th	Day	48% 8% 15% 23% 6%	6294
	21st to end	Day	48% 8% 14% 24% 6%	6728
August	1st to 10th	Day	54% 9% 14% 20% 3	4549
	11th to 20th	Day	51% 7% 15% 22% 5%	4541
	21st to end	Day	44% 7% 11% 28% 10%	4323
September	1st to 10th	Day	57% 7% 13% 16% 7%	2400
	11th to 20th	Day	56% 7% 15% 17% 4	2353
	21st to end	Day	58% 6% 13% 18% 5%	2195
October	1st to 10th	Day	59% 6% 13% 17% 4	3260
	11th to 20th	Day	71% 4 10% 13% 1	3073
	21st to end	Day	80% 5% 8% 5% 2	3081
November	1st to 10th	Day	78% 4 8% 7% 2 1	1681
	11th to 20th	Day	83% 4 6% 6% 1	1600
	21st to end	Day	88% 3 6% 3	1460
December	1st to 10th	Day	86% 2 4 8% 1	2280
	11th to 20th	Day	81% 4 4 8% 3	2618
	21st to end	Day	79% 4 4 9% 3 1	3547
January	1st to 10th	Night	85% 3 5% 6% 1	6349
	11th to 20th	Night	80% 4 4 7% 4	6360
	21st to end	Night	67% 4 7% 16% 5%	6996
February	1st to 10th	Night	67% 6% 8% 11% 8%	2750
	11th to 20th	Night	72% 6% 8% 10% 4	2535
	21st to end	Night	65% 6% 7% 15% 7%	1993
March	1st to 10th	Night	63% 4 5% 14% 12% 1	5374
	11th to 20th	Night	71% 5% 5% 11% 7% 1	5212
	21st to end	Night	61% 5% 7% 19% 8% 1	5011
April	1st to 10th	Night	61% 5% 8% 14% 9% 2	2000
	11th to 20th	Night	55% 5% 8% 20% 11% 1	1947
	21st to end	Night	56% 5% 8% 17% 12% 1	1672
May	1st to 10th	Night	48% 7% 9% 21% 13% 2	3600
	11th to 20th	Night	56% 7% 9% 19% 9% 1	3576
	21st to end	Night	55% 5% 7% 17% 14% 2	3839
June	1st to 10th	Night	53% 6% 9% 19% 12% 1	1400
	11th to 20th	Night	49% 8% 10% 20% 12% 2	1200
	21st to end	Night	47% 7% 13% 24% 9% 1	1200
July	1st to 10th	Night	55% 5% 10% 22% 8%	2963
	11th to 20th	Night	52% 6% 15% 19% 8%	3541
	21st to end	Night	44% 6% 13% 33% 4	3809
August	1st to 10th	Night	46% 8% 17% 24% 4	2576
	11th to 20th	Night	46% 7% 18% 23% 6%	2574
	21st to end	Night	45% 7% 13% 28% 8%	3538
September	1st to 10th	Night	55% 6% 12% 20% 8%	2000
	11th to 20th	Night	54% 8% 16% 17% 5%	2046
	21st to end	Night	55% 5% 14% 20% 6%	2202
October	1st to 10th	Night	58% 7% 13% 17% 4 1	3920
	11th to 20th	Night	71% 4 11% 11% 3	4022
	21st to end	Night	75% 4 11% 7% 2	4467
November	1st to 10th	Night	79% 5% 6% 7% 3	2617
	11th to 20th	Night	80% 4 8% 7% 1	2800
	21st to end	Night	87% 3 5% 4	2938
December	1st to 10th	Night	85% 4 5% 6% 1	4910
	11th to 20th	Night	77% 4 7% 11% 2	5592
	21st to end	Night	78% 3 6% 9% 2	7410

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	14% 17% 39% 26% 5% 1	200
	11th to 20th	Day	18% 11% 34% 19% 15% 5%	200
	21st to end	Day	15% 10% 33% 29% 12% 2	220
February	1st to 10th	Day	7% 17% 41% 26% 7% 1	225
	11th to 20th	Day	17% 13% 41% 22% 7% 1	300
	21st to end	Day	17% 15% 40% 21% 7% 1	400
March	1st to 10th	Day	17% 15% 32% 24% 10% 1	500
	11th to 20th	Day	21% 14% 35% 20% 8% 1	500
	21st to end	Day	23% 14% 30% 25% 6% 2	550
April	1st to 10th	Day	21% 17% 31% 19% 10% 2	500
	11th to 20th	Day	21% 16% 28% 23% 6% 5%	492
	21st to end	Day	24% 14% 36% 18% 7% 2	500
May	1st to 10th	Day	22% 13% 32% 21% 9% 2	503
	11th to 20th	Day	24% 12% 26% 24% 11% 3	527
	21st to end	Day	22% 13% 31% 24% 9% 1	608
June	1st to 10th	Day	27% 11% 30% 22% 9% 2	730
	11th to 20th	Day	21% 13% 31% 23% 10% 2	924
	21st to end	Day	22% 9% 27% 28% 12% 2	930
July	1st to 10th	Day	22% 9% 29% 25% 12% 2	794
	11th to 20th	Day	21% 10% 27% 26% 14% 3	533
	21st to end	Day	23% 7% 28% 23% 14% 5%	576
August	1st to 10th	Day	22% 11% 24% 23% 15% 5%	526
	11th to 20th	Day	21% 8% 25% 24% 15% 7%	519
	21st to end	Day	23% 10% 25% 22% 12% 8%	583
September	1st to 10th	Day	29% 12% 28% 18% 10% 3	530
	11th to 20th	Day	22% 13% 28% 23% 11% 3	530
	21st to end	Day	28% 13% 25% 18% 11% 4	530
October	1st to 10th	Day	26% 14% 28% 20% 10% 2	530
	11th to 20th	Day	35% 17% 22% 17% 7% 2	476
	21st to end	Day	34% 16% 28% 16% 6%	429
November	1st to 10th	Day	38% 15% 33% 12% 2	315
	11th to 20th	Day	32% 17% 28% 16% 9%	200
	21st to end	Day	37% 12% 30% 15% 6% 1	200
December	1st to 10th	Day	25% 12% 24% 23% 15% 3	200
	11th to 20th	Day	23% 22% 28% 16% 11% 2	200
	21st to end	Day	20% 15% 34% 23% 7% 2	220
January	1st to 10th	Night	21% 11% 33% 25% 9% 1	800
	11th to 20th	Night	19% 14% 34% 23% 9% 2	800
	21st to end	Night	14% 9% 31% 33% 13% 1	880
February	1st to 10th	Night	12% 12% 33% 33% 10% 2	800
	11th to 20th	Night	18% 12% 31% 29% 9% 1	783
	21st to end	Night	17% 12% 33% 25% 12% 1	660
March	1st to 10th	Night	16% 13% 31% 29% 9% 1	800
	11th to 20th	Night	19% 14% 32% 27% 8% 1	800
	21st to end	Night	21% 12% 35% 25% 7% 1	880
April	1st to 10th	Night	24% 12% 30% 26% 8%	800
	11th to 20th	Night	19% 12% 31% 26% 11%	763
	21st to end	Night	24% 7% 33% 26% 8% 1	472
May	1st to 10th	Night	27% 5% 31% 27% 10% 1	400
	11th to 20th	Night	21% 9% 33% 24% 12% 2	394
	21st to end	Night	25% 9% 29% 27% 9%	433
June	1st to 10th	Night	25% 8% 29% 29% 10%	400
	11th to 20th	Night	21% 7% 29% 32% 10% 1	400
	21st to end	Night	21% 8% 23% 36% 12% 1	400
July	1st to 10th	Night	24% 6% 26% 33% 9% 1	390
	11th to 20th	Night	19% 4 26% 36% 15% 1	388
	21st to end	Night	23% 5% 21% 36% 16% 1	438
August	1st to 10th	Night	23% 4 24% 26% 22% 2	398
	11th to 20th	Night	19% 7% 22% 30% 21% 2	396
	21st to end	Night	24% 9% 21% 28% 15% 3	845
September	1st to 10th	Night	28% 7% 25% 26% 13% 2	800
	11th to 20th	Night	27% 10% 24% 27% 10% 2	800
	21st to end	Night	26% 11% 28% 25% 10% 1	800
October	1st to 10th	Night	25% 12% 31% 23% 9% 1	800
	11th to 20th	Night	36% 11% 27% 20% 5% 2	793
	21st to end	Night	39% 11% 25% 18% 6%	836
November	1st to 10th	Night	36% 16% 25% 17% 6% 1	780
	11th to 20th	Night	28% 14% 32% 19% 7%	800
	21st to end	Night	28% 16% 30% 18% 7% 1	870
December	1st to 10th	Night	24% 11% 32% 22% 9% 1	900
	11th to 20th	Night	22% 13% 32% 21% 9% 2	900
	21st to end	Night	24% 12% 31% 24% 8% 1	970

Page generated at 2025-10-16 01:50:22. Version ac07

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