Corner Brook
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Corner Brook clear sky chart from 2005-11-06 to 2025-11-03.

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% 16% 6% 13% 7% 5% 4 3 4 5% 20%	126924
	Night	16% 16% 7% 16% 8% 6% 4 3 4 4 16%	123349
Transparency	Day	66% 6% 10% 14% 4	130333
	Night	71% 5% 9% 11% 3	128033
Seeing	Day	30% 21% 27% 15% 6% 1	19377
	Night	29% 18% 25% 21% 7% 1	26342

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	11% 24% 9% 22% 13% 7% 3 2 3 2 4	3616
	11th to 20th	Day	8% 18% 8% 31% 10% 7% 4 3 3 3 6%	3591
	21st to end	Day	5% 11% 8% 27% 22% 8% 4 3 3 2 8%	3982
February	1st to 10th	Day	14% 15% 6% 21% 17% 11% 4 3 3 2 5%	1609
	11th to 20th	Day	14% 20% 8% 21% 14% 7% 4 3 2 2 7%	1818
	21st to end	Day	10% 16% 8% 19% 14% 10% 5% 3 3 2 11%	1650
March	1st to 10th	Day	9% 18% 6% 18% 13% 9% 4 3 4 3 13%	4474
	11th to 20th	Day	15% 26% 9% 13% 7% 5% 4 2 3 4 11%	4663
	21st to end	Day	18% 19% 9% 16% 7% 4 4 2 3 4 13%	5971
April	1st to 10th	Day	16% 21% 9% 18% 7% 4 3 3 4 4 12%	2400
	11th to 20th	Day	15% 17% 6% 12% 5% 4 4 3 4 6% 23%	2437
	21st to end	Day	19% 19% 6% 11% 6% 4 3 2 4 4 22%	2640
May	1st to 10th	Day	20% 22% 6% 10% 4 4 3 2 3 3 23%	6345
	11th to 20th	Day	14% 15% 4 8% 5% 5% 4 4 6% 6% 29%	6318
	21st to end	Day	21% 13% 4 8% 5% 4 4 3 5% 7% 27%	7119
June	1st to 10th	Day	27% 14% 3 8% 6% 4 5% 3 5% 6% 19%	3000
	11th to 20th	Day	19% 10% 3 8% 5% 4 4 3 6% 7% 30%	3000
	21st to end	Day	24% 13% 3 7% 5% 4 4 3 5% 6% 26%	3000
July	1st to 10th	Day	17% 13% 4 8% 5% 5% 5% 4 5% 7% 26%	6590
	11th to 20th	Day	13% 8% 3 9% 7% 6% 6% 5% 8% 8% 28%	6360
	21st to end	Day	19% 9% 3 7% 5% 4 5% 4 5% 7% 32%	6927
August	1st to 10th	Day	19% 8% 3 8% 5% 5% 5% 5% 7% 9% 26%	4564
	11th to 20th	Day	18% 9% 3 7% 4 4 4 3 6% 8% 35%	4374
	21st to end	Day	22% 8% 3 8% 5% 4 5% 3 5% 7% 31%	4397
September	1st to 10th	Day	22% 8% 3 8% 4 4 4 3 6% 7% 31%	2400
	11th to 20th	Day	26% 12% 3 8% 6% 4 4 3 5% 6% 23%	2300
	21st to end	Day	21% 13% 4 9% 5% 4 4 4 5% 7% 23%	2200
October	1st to 10th	Day	22% 14% 3 8% 5% 3 4 3 5% 6% 28%	2078
	11th to 20th	Day	23% 19% 5% 9% 4 4 3 3 4 6% 20%	1871
	21st to end	Day	23% 24% 7% 10% 5% 4 3 2 3 4 17%	1980
November	1st to 10th	Day	22% 29% 9% 12% 5% 3 4 3 3 3 8%	1778
	11th to 20th	Day	20% 28% 9% 12% 5% 3 3 2 3 4 11%	1623
	21st to end	Day	16% 26% 12% 18% 5% 4 4 2 4 4 6%	1416
December	1st to 10th	Day	11% 19% 9% 24% 8% 7% 5% 3 4 4 6%	2290
	11th to 20th	Day	17% 22% 10% 24% 9% 4 4 2 2 2 3	2628
	21st to end	Day	15% 21% 9% 23% 10% 4 3 2 2 2 8%	3515
January	1st to 10th	Night	11% 22% 10% 21% 15% 7% 4 2 3 2 3	6349
	11th to 20th	Night	10% 16% 9% 31% 10% 6% 5% 3 3 3 6%	6314
	21st to end	Night	4 11% 9% 28% 16% 11% 6% 2 3 3 7%	6996
February	1st to 10th	Night	12% 17% 6% 23% 18% 10% 5% 2 2 2 4	2790
	11th to 20th	Night	13% 19% 8% 21% 14% 7% 6% 2 2 3 5%	2468
	21st to end	Night	8% 16% 6% 19% 14% 8% 6% 2 3 3 14%	1980
March	1st to 10th	Night	9% 17% 8% 19% 15% 8% 4 3 4 4 10%	5366
	11th to 20th	Night	12% 22% 10% 18% 8% 6% 4 3 3 3 11%	5280
	21st to end	Night	15% 18% 9% 18% 7% 4 4 3 3 4 13%	4961
April	1st to 10th	Night	18% 20% 8% 16% 7% 4 4 3 4 5% 12%	2000
	11th to 20th	Night	14% 18% 7% 11% 6% 5% 4 3 4 5% 21%	1913
	21st to end	Night	17% 15% 7% 12% 7% 5% 4 4 6% 5% 20%	1758
May	1st to 10th	Night	20% 22% 6% 10% 5% 4 4 3 4 5% 17%	3615
	11th to 20th	Night	17% 15% 4 7% 5% 5% 5% 4 5% 6% 28%	3596
	21st to end	Night	23% 11% 3 7% 3 4 5% 4 5% 7% 27%	3773
June	1st to 10th	Night	25% 15% 5% 9% 6% 4 3 4 4 5% 21%	1400
	11th to 20th	Night	20% 8% 3 6% 4 5% 5% 6% 8% 7% 30%	1400
	21st to end	Night	20% 9% 4 7% 5% 5% 6% 5% 6% 6% 25%	1400
July	1st to 10th	Night	22% 13% 4 9% 5% 4 4 3 6% 7% 23%	3385
	11th to 20th	Night	12% 10% 4 8% 5% 5% 6% 4 7% 9% 29%	3620
	21st to end	Night	21% 9% 3 7% 5% 4 4 4 5% 6% 31%	3948
August	1st to 10th	Night	13% 8% 3 8% 6% 6% 5% 6% 7% 8% 30%	2596
	11th to 20th	Night	18% 7% 2 7% 5% 4 6% 4 5% 6% 35%	2682
	21st to end	Night	19% 9% 3 8% 4 4 5% 4 5% 6% 33%	3489
September	1st to 10th	Night	22% 9% 3 7% 4 4 5% 4 4 6% 32%	2000
	11th to 20th	Night	25% 12% 4 8% 5% 4 4 3 5% 6% 25%	2100
	21st to end	Night	23% 11% 4 8% 5% 4 4 3 5% 6% 26%	2200
October	1st to 10th	Night	21% 14% 3 7% 5% 4 4 4 5% 6% 26%	2320
	11th to 20th	Night	22% 19% 4 10% 6% 4 4 3 4 4 20%	2528
	21st to end	Night	23% 21% 5% 9% 5% 4 4 3 4 5% 17%	2860
November	1st to 10th	Night	20% 28% 6% 11% 6% 4 3 2 4 4 10%	2565
	11th to 20th	Night	20% 25% 8% 14% 5% 5% 4 3 3 4 10%	2775
	21st to end	Night	19% 24% 11% 16% 7% 4 3 3 3 4 7%	2981
December	1st to 10th	Night	10% 19% 10% 26% 8% 6% 5% 3 3 4 5%	4900
	11th to 20th	Night	16% 21% 11% 23% 8% 4 3 2 2 2 7%	5581
	21st to end	Night	15% 17% 10% 27% 9% 4 3 2 3 3 7%	7460

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% 3 4 5%	3617
	11th to 20th	Day	82% 6% 6% 5% 1	3620
	21st to end	Day	83% 4 4 4 3 2	3982
February	1st to 10th	Day	87% 3 4 5% 2	1609
	11th to 20th	Day	86% 2 4 6% 2	1826
	21st to end	Day	81% 3 4 7% 4	1650
March	1st to 10th	Day	76% 4 6% 8% 6%	4478
	11th to 20th	Day	78% 4 7% 9% 2	4663
	21st to end	Day	76% 4 4 12% 4	5971
April	1st to 10th	Day	77% 5% 6% 8% 4 1	2400
	11th to 20th	Day	64% 4 8% 16% 7%	2437
	21st to end	Day	66% 6% 7% 12% 7% 1	2640
May	1st to 10th	Day	66% 6% 7% 17% 4	6357
	11th to 20th	Day	54% 6% 13% 19% 7%	6322
	21st to end	Day	57% 6% 12% 20% 5%	7119
June	1st to 10th	Day	66% 6% 8% 14% 6%	3000
	11th to 20th	Day	54% 7% 14% 21% 5%	3000
	21st to end	Day	59% 6% 11% 16% 7% 1	3000
July	1st to 10th	Day	57% 7% 11% 20% 5%	6519
	11th to 20th	Day	51% 8% 17% 20% 3	6284
	21st to end	Day	51% 7% 19% 19% 4	6730
August	1st to 10th	Day	53% 8% 15% 19% 4	4550
	11th to 20th	Day	47% 6% 16% 20% 8% 2	4416
	21st to end	Day	52% 6% 16% 21% 5%	4397
September	1st to 10th	Day	52% 6% 14% 21% 7%	2400
	11th to 20th	Day	61% 6% 13% 15% 4 1	2300
	21st to end	Day	61% 6% 14% 14% 4	2200
October	1st to 10th	Day	57% 7% 11% 19% 4	3377
	11th to 20th	Day	70% 6% 12% 9% 3	3029
	21st to end	Day	68% 6% 11% 13% 3	3191
November	1st to 10th	Day	83% 4 7% 5% 1	1778
	11th to 20th	Day	79% 4 6% 9% 2	1623
	21st to end	Day	83% 5% 7% 4 1	1416
December	1st to 10th	Day	79% 6% 7% 6% 1	2290
	11th to 20th	Day	90% 3 4 2 1	2627
	21st to end	Day	83% 3 6% 8% 1	3515
January	1st to 10th	Night	86% 4 5% 3 1	6349
	11th to 20th	Night	83% 6% 6% 5% 1	6360
	21st to end	Night	82% 4 4 4 4 2	6996
February	1st to 10th	Night	89% 3 3 3 1	2790
	11th to 20th	Night	87% 4 5% 4 1	2471
	21st to end	Night	76% 3 6% 9% 5%	1980
March	1st to 10th	Night	77% 6% 5% 8% 3	5375
	11th to 20th	Night	80% 3 5% 9% 3	5281
	21st to end	Night	74% 4 6% 11% 4	4961
April	1st to 10th	Night	74% 7% 6% 10% 3 1	2000
	11th to 20th	Night	65% 5% 8% 14% 7%	1913
	21st to end	Night	64% 7% 9% 13% 7% 1	1758
May	1st to 10th	Night	68% 6% 7% 15% 3	3620
	11th to 20th	Night	56% 6% 12% 21% 6%	3597
	21st to end	Night	54% 8% 12% 22% 4	3774
June	1st to 10th	Night	66% 6% 8% 15% 5%	1400
	11th to 20th	Night	50% 7% 16% 20% 7%	1400
	21st to end	Night	57% 7% 13% 16% 6%	1400
July	1st to 10th	Night	61% 6% 12% 17% 5%	3348
	11th to 20th	Night	50% 8% 15% 22% 6%	3572
	21st to end	Night	53% 6% 15% 24% 3	3831
August	1st to 10th	Night	48% 10% 19% 21% 2	2585
	11th to 20th	Night	48% 6% 20% 19% 5% 2	2706
	21st to end	Night	50% 7% 19% 21% 3	3488
September	1st to 10th	Night	54% 6% 15% 20% 5%	2000
	11th to 20th	Night	60% 6% 13% 13% 6%	2100
	21st to end	Night	59% 6% 13% 17% 6%	2200
October	1st to 10th	Night	55% 9% 13% 18% 5% 1	3788
	11th to 20th	Night	69% 5% 12% 11% 2	4116
	21st to end	Night	65% 7% 11% 14% 3 1	4610
November	1st to 10th	Night	79% 5% 8% 7% 1	2565
	11th to 20th	Night	80% 4 7% 7% 2	2775
	21st to end	Night	83% 3 6% 6% 1	2981
December	1st to 10th	Night	82% 6% 6% 5% 1	4900
	11th to 20th	Night	86% 3 6% 4 1	5583
	21st to end	Night	83% 5% 5% 7%	7460

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	28% 30% 27% 11% 4 2	400
	11th to 20th	Day	29% 24% 27% 14% 5% 2	400
	21st to end	Day	28% 27% 26% 15% 4	440
February	1st to 10th	Day	29% 27% 25% 12% 6% 1	400
	11th to 20th	Day	35% 28% 24% 10% 3 1	396
	21st to end	Day	24% 27% 33% 8% 5% 2	331
March	1st to 10th	Day	24% 29% 31% 12% 3 2	400
	11th to 20th	Day	32% 25% 21% 13% 7% 1	413
	21st to end	Day	34% 26% 24% 10% 4 1	550
April	1st to 10th	Day	36% 29% 24% 10% 2	500
	11th to 20th	Day	29% 26% 27% 12% 5% 1	555
	21st to end	Day	30% 20% 27% 16% 5% 2	700
May	1st to 10th	Day	35% 17% 25% 15% 6% 2	703
	11th to 20th	Day	26% 19% 27% 16% 11% 1	724
	21st to end	Day	31% 21% 26% 15% 6% 1	790
June	1st to 10th	Day	36% 16% 25% 15% 6% 2	730
	11th to 20th	Day	28% 16% 28% 19% 8% 1	730
	21st to end	Day	32% 16% 27% 15% 8% 2	730
July	1st to 10th	Day	26% 14% 31% 19% 7% 2	720
	11th to 20th	Day	22% 16% 34% 18% 9%	718
	21st to end	Day	28% 15% 28% 21% 7% 1	795
August	1st to 10th	Day	22% 14% 30% 23% 9% 2	725
	11th to 20th	Day	25% 14% 28% 22% 9% 2	717
	21st to end	Day	26% 18% 27% 19% 7% 2	642
September	1st to 10th	Day	25% 22% 31% 18% 5%	530
	11th to 20th	Day	36% 18% 31% 10% 4	475
	21st to end	Day	32% 21% 29% 13% 4 1	420
October	1st to 10th	Day	29% 22% 29% 12% 5% 2	420
	11th to 20th	Day	35% 18% 22% 14% 9% 1	420
	21st to end	Day	35% 21% 24% 13% 6% 1	462
November	1st to 10th	Day	44% 23% 21% 10% 2	401
	11th to 20th	Day	38% 21% 21% 12% 7% 2	400
	21st to end	Day	40% 25% 21% 12% 2	400
December	1st to 10th	Day	35% 23% 25% 13% 5%	400
	11th to 20th	Day	35% 26% 27% 10% 3	400
	21st to end	Day	28% 27% 24% 13% 7% 1	440
January	1st to 10th	Night	30% 26% 23% 17% 4	900
	11th to 20th	Night	26% 27% 27% 13% 7%	900
	21st to end	Night	24% 26% 28% 18% 4	990
February	1st to 10th	Night	26% 29% 26% 15% 4 1	895
	11th to 20th	Night	30% 23% 28% 15% 3 1	783
	21st to end	Night	22% 21% 27% 19% 8% 2	660
March	1st to 10th	Night	23% 28% 28% 17% 5% 1	800
	11th to 20th	Night	25% 20% 24% 22% 8% 1	771
	21st to end	Night	28% 18% 27% 20% 7%	660
April	1st to 10th	Night	34% 21% 24% 16% 6% 1	600
	11th to 20th	Night	26% 17% 26% 24% 6% 1	594
	21st to end	Night	27% 16% 25% 26% 6% 1	600
May	1st to 10th	Night	30% 14% 23% 25% 7% 2	600
	11th to 20th	Night	29% 13% 23% 23% 12%	592
	21st to end	Night	32% 11% 27% 22% 7% 1	649
June	1st to 10th	Night	34% 11% 20% 25% 9% 1	600
	11th to 20th	Night	23% 14% 24% 28% 11% 1	600
	21st to end	Night	26% 12% 27% 26% 8% 2	600
July	1st to 10th	Night	25% 10% 28% 24% 11% 1	586
	11th to 20th	Night	22% 10% 27% 32% 9%	582
	21st to end	Night	26% 9% 25% 31% 9%	656
August	1st to 10th	Night	22% 10% 24% 30% 14% 1	598
	11th to 20th	Night	24% 7% 26% 28% 12% 2	592
	21st to end	Night	24% 9% 24% 28% 13% 1	660
September	1st to 10th	Night	29% 16% 23% 26% 7% 1	600
	11th to 20th	Night	34% 13% 23% 24% 6%	600
	21st to end	Night	32% 15% 26% 20% 7%	600
October	1st to 10th	Night	31% 13% 27% 23% 6% 1	720
	11th to 20th	Night	36% 13% 20% 22% 7% 1	872
	21st to end	Night	36% 18% 21% 18% 7%	1001
November	1st to 10th	Night	39% 19% 23% 15% 4	891
	11th to 20th	Night	39% 18% 21% 15% 6% 1	900
	21st to end	Night	39% 24% 21% 14% 2	900
December	1st to 10th	Night	30% 23% 24% 16% 6%	900
	11th to 20th	Night	34% 26% 23% 15% 2	900
	21st to end	Night	27% 24% 25% 16% 7% 1	990

Page generated at 2025-10-31 03:02:43. Version ac07

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