Blanc-Sablon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blanc-Sablon clear sky chart from 2005-11-06 to 2026-03-18.

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	23% 13% 4 8% 5% 4 4 3 5% 6% 25%	132148
	Night	20% 14% 4 9% 5% 4 4 3 5% 6% 25%	129599
Transparency	Day	59% 6% 12% 16% 6% 1	135520
	Night	60% 5% 12% 16% 7% 1	134335
Seeing	Day	28% 10% 24% 24% 11% 2	19932
	Night	28% 10% 28% 24% 9% 1	26490

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	13% 16% 6% 13% 7% 5% 6% 4 5% 4 20%	4122
	11th to 20th	Day	21% 18% 6% 11% 5% 5% 3 2 3 4 20%	4599
	21st to end	Day	6% 14% 3 9% 5% 5% 9% 7% 8% 10% 24%	5157
February	1st to 10th	Day	11% 16% 4 9% 5% 4 4 4 5% 7% 32%	1680
	11th to 20th	Day	10% 19% 5% 9% 6% 4 5% 4 4 5% 30%	1794
	21st to end	Day	11% 15% 5% 9% 4 4 4 3 4 6% 35%	1730
March	1st to 10th	Day	13% 12% 4 10% 5% 5% 5% 3 4 5% 32%	4574
	11th to 20th	Day	17% 20% 7% 13% 5% 4 4 2 3 4 22%	4723
	21st to end	Day	24% 15% 4 9% 5% 5% 5% 3 4 5% 22%	5943
April	1st to 10th	Day	20% 16% 5% 10% 6% 4 5% 3 5% 6% 20%	2400
	11th to 20th	Day	19% 15% 4 8% 5% 4 4 4 4 6% 27%	2512
	21st to end	Day	20% 13% 5% 9% 5% 5% 4 3 5% 6% 26%	2681
May	1st to 10th	Day	30% 13% 4 8% 4 4 4 3 4 4 22%	6345
	11th to 20th	Day	21% 11% 4 9% 5% 5% 4 4 5% 6% 28%	6527
	21st to end	Day	28% 13% 4 7% 5% 4 4 3 4 5% 23%	7428
June	1st to 10th	Day	30% 11% 3 9% 6% 4 4 4 5% 6% 19%	3000
	11th to 20th	Day	31% 10% 3 7% 4 4 4 4 5% 6% 21%	3183
	21st to end	Day	30% 11% 3 7% 5% 4 4 4 4 8% 20%	3200
July	1st to 10th	Day	29% 15% 4 7% 4 3 3 3 3 5% 25%	7131
	11th to 20th	Day	31% 10% 3 6% 4 4 3 3 4 7% 27%	6762
	21st to end	Day	23% 10% 3 8% 5% 5% 5% 4 6% 8% 24%	6927
August	1st to 10th	Day	28% 9% 3 6% 4 4 3 4 6% 8% 25%	4564
	11th to 20th	Day	29% 12% 3 7% 4 4 4 3 5% 6% 24%	4415
	21st to end	Day	22% 10% 3 7% 4 4 4 3 5% 7% 31%	4581
September	1st to 10th	Day	28% 8% 2 5% 4 3 3 3 6% 7% 31%	2400
	11th to 20th	Day	28% 9% 3 7% 5% 4 5% 3 4 6% 27%	2280
	21st to end	Day	27% 9% 2 6% 4 4 5% 3 5% 6% 30%	2200
October	1st to 10th	Day	26% 10% 2 6% 5% 3 4 2 4 7% 33%	2095
	11th to 20th	Day	27% 12% 3 7% 4 4 4 2 5% 5% 28%	1810
	21st to end	Day	23% 14% 3 6% 3 4 4 3 4 6% 30%	1980
November	1st to 10th	Day	23% 12% 3 6% 4 4 3 3 4 4 33%	1813
	11th to 20th	Day	23% 16% 3 7% 5% 4 3 2 3 4 30%	1489
	21st to end	Day	24% 17% 6% 7% 4 3 3 2 3 5% 27%	1470
December	1st to 10th	Day	13% 16% 4 12% 4 4 3 3 5% 7% 27%	2360
	11th to 20th	Day	22% 17% 6% 9% 4 4 4 3 5% 6% 20%	2698
	21st to end	Day	15% 13% 4 12% 6% 4 3 3 5% 7% 29%	3575
January	1st to 10th	Night	13% 18% 7% 12% 6% 5% 5% 4 4 5% 20%	8802
	11th to 20th	Night	16% 20% 7% 13% 6% 4 4 3 3 4 21%	8313
	21st to end	Night	7% 12% 4 10% 5% 4 5% 6% 12% 8% 27%	9056
February	1st to 10th	Night	11% 14% 5% 10% 6% 5% 3 4 5% 6% 31%	2940
	11th to 20th	Night	11% 17% 6% 11% 6% 4 4 3 4 5% 28%	2709
	21st to end	Night	11% 15% 6% 10% 5% 4 3 3 4 5% 33%	2076
March	1st to 10th	Night	14% 13% 5% 11% 7% 5% 5% 3 5% 5% 27%	5486
	11th to 20th	Night	14% 21% 7% 11% 6% 4 4 2 3 4 24%	5391
	21st to end	Night	21% 16% 4 9% 5% 4 5% 4 5% 5% 22%	4974
April	1st to 10th	Night	20% 20% 6% 10% 6% 4 3 3 4 4 21%	2000
	11th to 20th	Night	21% 14% 4 8% 5% 3 4 4 4 5% 27%	1838
	21st to end	Night	23% 11% 4 9% 5% 4 3 3 4 5% 28%	1715
May	1st to 10th	Night	27% 16% 4 9% 5% 4 5% 4 6% 6% 16%	3615
	11th to 20th	Night	24% 11% 4 7% 4 4 4 3 4 6% 30%	3385
	21st to end	Night	29% 14% 3 7% 4 4 3 3 4 5% 24%	3468
June	1st to 10th	Night	32% 12% 3 8% 7% 4 3 4 5% 5% 19%	1400
	11th to 20th	Night	33% 11% 3 7% 3 4 4 4 5% 6% 19%	1231
	21st to end	Night	33% 12% 3 7% 5% 4 4 4 5% 5% 19%	1200
July	1st to 10th	Night	31% 18% 4 7% 4 3 3 2 3 4 20%	2802
	11th to 20th	Night	32% 11% 3 6% 3 4 4 3 6% 5% 24%	3214
	21st to end	Night	26% 8% 3 7% 4 4 5% 4 6% 7% 26%	3948
August	1st to 10th	Night	27% 11% 3 7% 5% 4 4 2 5% 7% 25%	2596
	11th to 20th	Night	33% 10% 3 6% 5% 4 3 3 4 5% 27%	2641
	21st to end	Night	23% 7% 2 5% 3 5% 4 4 6% 7% 34%	3323
September	1st to 10th	Night	28% 9% 3 5% 4 4 4 4 5% 6% 30%	2000
	11th to 20th	Night	29% 8% 3 6% 4 3 4 3 5% 5% 30%	2119
	21st to end	Night	26% 9% 3 7% 4 4 4 3 5% 6% 31%	2200
October	1st to 10th	Night	24% 10% 2 7% 4 5% 5% 3 5% 5% 30%	2302
	11th to 20th	Night	25% 11% 3 7% 4 4 3 3 4 6% 30%	2590
	21st to end	Night	26% 13% 3 8% 4 3 3 3 4 6% 27%	2860
November	1st to 10th	Night	26% 11% 3 8% 4 3 4 3 4 5% 29%	2700
	11th to 20th	Night	27% 15% 3 8% 4 3 3 2 4 5% 26%	3129
	21st to end	Night	24% 19% 4 8% 4 3 3 3 4 4 24%	3150
December	1st to 10th	Night	13% 19% 6% 13% 6% 4 4 3 4 5% 23%	5050
	11th to 20th	Night	24% 14% 5% 11% 5% 4 4 3 5% 7% 19%	5731
	21st to end	Night	15% 15% 4 11% 5% 4 4 3 5% 7% 27%	7645

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	64% 6% 10% 13% 5% 2	4123
	11th to 20th	Day	67% 6% 11% 12% 4	4628
	21st to end	Day	48% 10% 11% 19% 10% 1	5157
February	1st to 10th	Day	51% 5% 11% 21% 9% 2	1680
	11th to 20th	Day	57% 5% 11% 16% 11% 1	1801
	21st to end	Day	51% 3 9% 19% 16% 1	1730
March	1st to 10th	Day	54% 4 8% 15% 17% 1	4578
	11th to 20th	Day	68% 4 7% 10% 9% 3	4723
	21st to end	Day	64% 6% 7% 12% 10% 1	5943
April	1st to 10th	Day	63% 7% 8% 12% 9% 1	2400
	11th to 20th	Day	57% 6% 12% 14% 9% 1	2512
	21st to end	Day	59% 7% 10% 16% 7% 1	2681
May	1st to 10th	Day	65% 7% 10% 14% 5%	6357
	11th to 20th	Day	55% 7% 15% 18% 6%	6531
	21st to end	Day	62% 8% 13% 15% 3	7428
June	1st to 10th	Day	65% 7% 12% 10% 5%	3000
	11th to 20th	Day	63% 9% 12% 13% 3	3183
	21st to end	Day	61% 7% 12% 16% 3	3200
July	1st to 10th	Day	62% 4 8% 21% 5%	7053
	11th to 20th	Day	59% 3 14% 20% 4	6680
	21st to end	Day	58% 5% 15% 19% 2	6730
August	1st to 10th	Day	58% 6% 16% 17% 2	4550
	11th to 20th	Day	62% 6% 14% 15% 3	4457
	21st to end	Day	53% 5% 15% 20% 5%	4581
September	1st to 10th	Day	52% 7% 15% 19% 7%	2400
	11th to 20th	Day	58% 6% 15% 15% 6% 1	2280
	21st to end	Day	55% 7% 14% 17% 7%	2200
October	1st to 10th	Day	48% 3 17% 26% 6%	3407
	11th to 20th	Day	58% 5% 17% 14% 6%	2932
	21st to end	Day	62% 3 10% 16% 7% 1	3191
November	1st to 10th	Day	55% 5% 14% 17% 8% 1	1813
	11th to 20th	Day	60% 3 14% 17% 6%	1489
	21st to end	Day	61% 5% 11% 16% 7%	1470
December	1st to 10th	Day	57% 4 12% 20% 6%	2360
	11th to 20th	Day	64% 6% 13% 12% 5%	2697
	21st to end	Day	54% 4 14% 17% 10%	3575
January	1st to 10th	Night	64% 5% 10% 13% 5% 2	8802
	11th to 20th	Night	65% 7% 13% 10% 5%	8359
	21st to end	Night	45% 9% 8% 23% 13% 2	9056
February	1st to 10th	Night	53% 5% 11% 19% 10% 2	2940
	11th to 20th	Night	60% 4 12% 14% 9% 1	2713
	21st to end	Night	53% 4 10% 20% 11% 1	2076
March	1st to 10th	Night	58% 5% 8% 15% 13% 1	5495
	11th to 20th	Night	65% 3 7% 11% 12% 1	5392
	21st to end	Night	63% 5% 9% 15% 7% 1	4974
April	1st to 10th	Night	66% 5% 8% 11% 8% 2	2000
	11th to 20th	Night	57% 5% 12% 16% 8% 1	1838
	21st to end	Night	59% 6% 11% 14% 8% 2	1715
May	1st to 10th	Night	68% 8% 13% 9% 3	3620
	11th to 20th	Night	55% 6% 11% 19% 8%	3386
	21st to end	Night	63% 5% 12% 18% 2	3469
June	1st to 10th	Night	67% 8% 11% 10% 5% 1	1400
	11th to 20th	Night	65% 8% 14% 10% 3	1231
	21st to end	Night	65% 7% 12% 13% 4	1200
July	1st to 10th	Night	69% 3 8% 16% 4	2771
	11th to 20th	Night	61% 4 12% 19% 4	3172
	21st to end	Night	57% 5% 17% 19% 2	3831
August	1st to 10th	Night	60% 5% 18% 16% 2	2585
	11th to 20th	Night	62% 5% 17% 13% 3	2665
	21st to end	Night	49% 6% 18% 22% 5%	3322
September	1st to 10th	Night	54% 7% 16% 17% 7%	2000
	11th to 20th	Night	55% 6% 15% 17% 6%	2119
	21st to end	Night	55% 6% 15% 17% 7% 1	2200
October	1st to 10th	Night	54% 4 13% 22% 7%	3770
	11th to 20th	Night	56% 5% 13% 17% 9%	4217
	21st to end	Night	62% 4 11% 15% 8%	4610
November	1st to 10th	Night	59% 5% 11% 17% 7%	2700
	11th to 20th	Night	61% 5% 12% 16% 5%	3129
	21st to end	Night	65% 5% 11% 14% 5%	3150
December	1st to 10th	Night	63% 5% 10% 17% 5% 1	5050
	11th to 20th	Night	65% 5% 13% 12% 5%	5733
	21st to end	Night	56% 5% 15% 19% 5%	7645

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	22% 13% 31% 22% 10% 2	430
	11th to 20th	Day	26% 11% 32% 20% 9% 3	430
	21st to end	Day	19% 15% 30% 27% 8% 1	473
February	1st to 10th	Day	19% 10% 30% 28% 10% 3	430
	11th to 20th	Day	18% 14% 33% 25% 8% 2	426
	21st to end	Day	19% 14% 31% 23% 10% 3	355
March	1st to 10th	Day	17% 14% 35% 23% 8% 2	430
	11th to 20th	Day	24% 12% 24% 22% 14% 3	421
	21st to end	Day	23% 13% 28% 25% 8% 2	543
April	1st to 10th	Day	24% 14% 27% 24% 10% 2	500
	11th to 20th	Day	25% 10% 24% 26% 12% 3	630
	21st to end	Day	25% 9% 26% 24% 13% 3	700
May	1st to 10th	Day	29% 9% 24% 24% 10% 3	703
	11th to 20th	Day	27% 8% 25% 22% 14% 5%	724
	21st to end	Day	32% 7% 22% 27% 10% 2	790
June	1st to 10th	Day	33% 8% 21% 23% 11% 3	730
	11th to 20th	Day	36% 8% 18% 26% 10% 2	730
	21st to end	Day	36% 7% 17% 26% 10% 5%	730
July	1st to 10th	Day	38% 7% 18% 21% 14% 3	720
	11th to 20th	Day	33% 6% 19% 25% 15% 2	718
	21st to end	Day	33% 6% 17% 29% 13% 2	795
August	1st to 10th	Day	30% 6% 18% 28% 15% 3	725
	11th to 20th	Day	34% 7% 17% 26% 13% 2	717
	21st to end	Day	29% 7% 21% 27% 13% 3	748
September	1st to 10th	Day	31% 11% 26% 20% 11% 2	530
	11th to 20th	Day	28% 9% 27% 29% 6% 2	464
	21st to end	Day	30% 10% 25% 25% 7% 3	420
October	1st to 10th	Day	29% 9% 34% 21% 7% 1	420
	11th to 20th	Day	31% 9% 20% 29% 11%	420
	21st to end	Day	29% 14% 22% 22% 11% 2	462
November	1st to 10th	Day	29% 16% 34% 17% 3 1	425
	11th to 20th	Day	31% 13% 26% 18% 10%	430
	21st to end	Day	30% 16% 28% 19% 6%	430
December	1st to 10th	Day	27% 11% 30% 24% 8%	430
	11th to 20th	Day	25% 17% 35% 18% 4 1	430
	21st to end	Day	22% 15% 27% 24% 10% 3	473
January	1st to 10th	Night	23% 15% 34% 21% 7% 1	950
	11th to 20th	Night	23% 15% 33% 22% 6%	950
	21st to end	Night	21% 15% 33% 26% 5%	1045
February	1st to 10th	Night	19% 11% 34% 27% 8% 1	950
	11th to 20th	Night	19% 13% 37% 24% 6% 1	873
	21st to end	Night	18% 7% 34% 27% 11% 2	692
March	1st to 10th	Night	18% 14% 35% 24% 8% 1	840
	11th to 20th	Night	23% 10% 27% 28% 10% 1	774
	21st to end	Night	25% 11% 31% 25% 7% 1	660
April	1st to 10th	Night	28% 11% 29% 23% 9% 1	600
	11th to 20th	Night	27% 10% 27% 24% 11% 1	594
	21st to end	Night	29% 7% 22% 31% 11% 2	600
May	1st to 10th	Night	30% 8% 22% 26% 12% 3	600
	11th to 20th	Night	28% 7% 26% 25% 11% 2	592
	21st to end	Night	36% 7% 21% 26% 9% 1	649
June	1st to 10th	Night	36% 6% 22% 25% 10% 1	600
	11th to 20th	Night	36% 5% 18% 29% 11% 1	431
	21st to end	Night	37% 6% 15% 24% 16% 2	400
July	1st to 10th	Night	41% 7% 16% 24% 11% 1	419
	11th to 20th	Night	39% 6% 15% 29% 11%	582
	21st to end	Night	33% 4 18% 32% 11% 1	656
August	1st to 10th	Night	30% 6% 17% 32% 14% 1	598
	11th to 20th	Night	35% 8% 15% 27% 14% 1	592
	21st to end	Night	30% 4 20% 28% 16% 1	660
September	1st to 10th	Night	29% 9% 25% 26% 9% 1	600
	11th to 20th	Night	32% 8% 31% 22% 7%	600
	21st to end	Night	33% 7% 29% 23% 7% 1	600
October	1st to 10th	Night	28% 9% 31% 25% 6% 1	702
	11th to 20th	Night	31% 8% 24% 26% 10% 1	905
	21st to end	Night	32% 11% 24% 23% 9% 1	1001
November	1st to 10th	Night	32% 14% 32% 18% 4 1	930
	11th to 20th	Night	35% 14% 27% 18% 6% 1	950
	21st to end	Night	33% 16% 31% 17% 3	950
December	1st to 10th	Night	27% 13% 32% 21% 6% 1	950
	11th to 20th	Night	28% 17% 31% 20% 4	950
	21st to end	Night	22% 14% 30% 24% 9% 1	1045

Page generated at 2026-03-15 02:23:52. Version ac07

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