Deer Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deer Lake clear sky chart from 2005-11-06 to 2026-07-16.

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% 11% 7% 6% 5% 4 5% 6% 21%	138407
	Night	18% 13% 5% 12% 7% 6% 5% 4 5% 6% 18%	134568
Transparency	Day	63% 7% 11% 14% 5%	141828
	Night	67% 7% 10% 12% 4	139256
Seeing	Day	27% 17% 27% 18% 8% 2	20384
	Night	27% 15% 28% 23% 7% 1	27325

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	15% 21% 7% 17% 9% 7% 5% 3 3 4 9%	4538
	11th to 20th	Day	18% 16% 7% 24% 9% 6% 5% 3 4 2 5%	4681
	21st to end	Day	4 14% 7% 16% 14% 13% 9% 5% 5% 4 8%	5157
February	1st to 10th	Day	15% 13% 5% 14% 14% 9% 7% 4 5% 4 9%	1680
	11th to 20th	Day	15% 20% 6% 13% 10% 7% 7% 3 5% 4 11%	1905
	21st to end	Day	12% 15% 6% 14% 9% 8% 7% 4 6% 5% 14%	1730
March	1st to 10th	Day	14% 16% 5% 14% 10% 8% 5% 4 5% 5% 15%	4574
	11th to 20th	Day	16% 22% 8% 12% 7% 6% 4 3 3 4 16%	4747
	21st to end	Day	24% 17% 7% 13% 7% 4 4 3 3 4 15%	6099
April	1st to 10th	Day	20% 20% 6% 13% 7% 6% 4 3 4 4 14%	2520
	11th to 20th	Day	18% 16% 4 10% 5% 4 4 3 4 6% 26%	2586
	21st to end	Day	22% 18% 6% 9% 5% 4 4 3 3 4 22%	2751
May	1st to 10th	Day	27% 17% 5% 8% 4 4 4 2 3 5% 21%	8236
	11th to 20th	Day	21% 13% 4 8% 5% 5% 5% 3 4 6% 26%	8220
	21st to end	Day	24% 12% 3 6% 4 4 4 3 5% 7% 28%	9456
June	1st to 10th	Day	31% 11% 4 8% 5% 4 4 3 4 6% 19%	3150
	11th to 20th	Day	23% 10% 3 7% 5% 4 4 3 6% 6% 28%	3150
	21st to end	Day	24% 11% 3 7% 5% 4 4 4 5% 6% 27%	3150
July	1st to 10th	Day	13% 11% 4 9% 6% 6% 5% 5% 6% 7% 27%	6907
	11th to 20th	Day	12% 8% 3 8% 7% 7% 7% 6% 7% 8% 28%	6430
	21st to end	Day	17% 7% 3 7% 5% 5% 5% 4 7% 8% 33%	6927
August	1st to 10th	Day	19% 8% 3 8% 5% 5% 5% 4 6% 8% 29%	4564
	11th to 20th	Day	19% 8% 3 6% 4 4 4 3 4 6% 38%	4345
	21st to end	Day	22% 7% 3 7% 5% 4 5% 4 6% 7% 30%	4458
September	1st to 10th	Day	23% 8% 3 6% 4 4 5% 3 5% 7% 32%	2400
	11th to 20th	Day	23% 9% 3 8% 6% 5% 5% 4 5% 7% 24%	2280
	21st to end	Day	19% 11% 5% 10% 5% 5% 4 4 5% 8% 25%	2200
October	1st to 10th	Day	21% 11% 3 7% 4 5% 4 3 5% 7% 30%	2104
	11th to 20th	Day	23% 15% 4 9% 5% 5% 5% 4 5% 5% 21%	1849
	21st to end	Day	22% 15% 5% 11% 7% 5% 4 3 4 5% 18%	1980
November	1st to 10th	Day	22% 19% 5% 13% 6% 6% 5% 3 4 5% 11%	1850
	11th to 20th	Day	23% 19% 6% 12% 5% 5% 5% 3 5% 5% 13%	1680
	21st to end	Day	22% 19% 6% 15% 7% 6% 6% 3 4 4 9%	1470
December	1st to 10th	Day	12% 14% 6% 17% 8% 7% 6% 4 6% 7% 11%	2360
	11th to 20th	Day	24% 15% 6% 15% 9% 5% 6% 3 5% 4 8%	2698
	21st to end	Day	17% 14% 6% 18% 10% 6% 5% 3 4 4 11%	3575
January	1st to 10th	Night	14% 20% 8% 17% 10% 7% 5% 3 4 4 8%	8371
	11th to 20th	Night	14% 13% 6% 24% 10% 8% 6% 5% 5% 3 6%	8234
	21st to end	Night	5% 13% 7% 17% 10% 12% 9% 5% 6% 5% 10%	9056
February	1st to 10th	Night	14% 15% 5% 16% 14% 10% 6% 4 5% 4 8%	2940
	11th to 20th	Night	13% 19% 6% 15% 11% 8% 5% 4 4 4 10%	2597
	21st to end	Night	11% 15% 4 13% 10% 8% 8% 4 6% 5% 17%	2076
March	1st to 10th	Night	13% 16% 4 13% 10% 10% 7% 4 5% 5% 12%	5486
	11th to 20th	Night	16% 20% 7% 14% 6% 6% 5% 3 4 4 15%	5431
	21st to end	Night	20% 16% 7% 13% 7% 5% 4 3 4 5% 14%	5071
April	1st to 10th	Night	22% 17% 5% 11% 5% 5% 4 3 4 6% 17%	2100
	11th to 20th	Night	18% 14% 5% 9% 6% 5% 5% 4 5% 6% 23%	1983
	21st to end	Night	23% 15% 5% 9% 5% 4 4 3 4 5% 22%	1867
May	1st to 10th	Night	28% 16% 4 8% 4 4 3 3 4 5% 19%	4692
	11th to 20th	Night	21% 11% 3 8% 4 5% 5% 4 5% 7% 28%	4670
	21st to end	Night	25% 13% 4 7% 4 4 3 3 5% 5% 27%	4733
June	1st to 10th	Night	30% 11% 4 7% 5% 4 3 3 4 6% 23%	1470
	11th to 20th	Night	22% 7% 3 5% 5% 5% 4 4 6% 8% 30%	1470
	21st to end	Night	23% 10% 2 8% 5% 4 4 4 5% 8% 25%	1470
July	1st to 10th	Night	20% 9% 3 8% 5% 5% 4 4 7% 8% 26%	3287
	11th to 20th	Night	12% 9% 3 9% 5% 5% 6% 4 7% 9% 32%	3661
	21st to end	Night	22% 7% 3 7% 5% 4 4 3 5% 7% 34%	3948
August	1st to 10th	Night	12% 7% 3 9% 6% 5% 6% 5% 7% 8% 32%	2596
	11th to 20th	Night	19% 6% 3 6% 4 4 5% 4 4 7% 38%	2712
	21st to end	Night	20% 6% 2 6% 4 4 5% 4 6% 7% 36%	3442
September	1st to 10th	Night	20% 9% 3 7% 4 4 5% 4 5% 7% 34%	2000
	11th to 20th	Night	23% 9% 4 7% 5% 5% 5% 4 5% 7% 27%	2119
	21st to end	Night	22% 9% 3 7% 5% 5% 5% 4 5% 7% 28%	2200
October	1st to 10th	Night	20% 10% 3 7% 5% 5% 5% 3 6% 9% 27%	2294
	11th to 20th	Night	21% 11% 4 9% 5% 6% 5% 3 5% 7% 23%	2550
	21st to end	Night	24% 13% 3 9% 5% 5% 5% 3 5% 6% 22%	2860
November	1st to 10th	Night	22% 16% 5% 11% 7% 6% 5% 4 5% 5% 15%	2668
	11th to 20th	Night	24% 18% 6% 10% 6% 6% 4 4 5% 6% 12%	2938
	21st to end	Night	22% 18% 8% 14% 7% 6% 4 3 4 4 10%	3150
December	1st to 10th	Night	14% 15% 7% 14% 8% 7% 7% 5% 7% 7% 10%	5050
	11th to 20th	Night	22% 12% 6% 14% 8% 6% 5% 4 5% 6% 12%	5731
	21st to end	Night	16% 15% 7% 18% 10% 6% 5% 4 4 4 10%	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	78% 6% 8% 6% 3	4539
	11th to 20th	Day	82% 7% 7% 3 1	4710
	21st to end	Day	75% 9% 5% 6% 3 2	5157
February	1st to 10th	Day	77% 8% 7% 6% 3	1680
	11th to 20th	Day	78% 7% 5% 7% 3	1913
	21st to end	Day	71% 8% 6% 10% 5% 1	1730
March	1st to 10th	Day	68% 8% 8% 11% 6%	4578
	11th to 20th	Day	71% 6% 7% 10% 6% 1	4747
	21st to end	Day	71% 7% 5% 11% 5%	6099
April	1st to 10th	Day	76% 5% 6% 8% 4 1	2520
	11th to 20th	Day	61% 5% 9% 16% 8%	2586
	21st to end	Day	67% 4 7% 13% 7% 1	2751
May	1st to 10th	Day	65% 6% 10% 16% 3	8249
	11th to 20th	Day	58% 6% 11% 17% 7%	8224
	21st to end	Day	56% 5% 12% 21% 6%	9457
June	1st to 10th	Day	67% 5% 10% 13% 5%	3150
	11th to 20th	Day	56% 5% 13% 21% 5%	3150
	21st to end	Day	57% 7% 11% 17% 7% 1	3150
July	1st to 10th	Day	55% 8% 11% 20% 6%	6832
	11th to 20th	Day	49% 10% 16% 22% 4	6354
	21st to end	Day	47% 8% 18% 22% 5%	6730
August	1st to 10th	Day	51% 9% 15% 21% 5%	4550
	11th to 20th	Day	46% 6% 15% 20% 10% 2	4387
	21st to end	Day	53% 6% 15% 21% 5%	4458
September	1st to 10th	Day	50% 6% 12% 24% 8% 1	2400
	11th to 20th	Day	59% 7% 13% 16% 5% 1	2280
	21st to end	Day	57% 6% 15% 15% 7%	2200
October	1st to 10th	Day	57% 9% 12% 16% 5% 1	3429
	11th to 20th	Day	64% 8% 14% 11% 3	2995
	21st to end	Day	63% 8% 10% 14% 5%	3191
November	1st to 10th	Day	77% 5% 9% 7% 1	1850
	11th to 20th	Day	73% 7% 7% 11% 3	1680
	21st to end	Day	77% 7% 8% 5% 2	1470
December	1st to 10th	Day	69% 9% 11% 9% 2	2360
	11th to 20th	Day	79% 9% 8% 3 2	2697
	21st to end	Day	77% 7% 7% 7% 1	3575
January	1st to 10th	Night	78% 7% 5% 6% 3	8371
	11th to 20th	Night	81% 8% 5% 4 1	8280
	21st to end	Night	74% 8% 7% 5% 5% 1	9056
February	1st to 10th	Night	80% 6% 6% 5% 2	2940
	11th to 20th	Night	80% 7% 7% 6% 1	2600
	21st to end	Night	71% 5% 8% 10% 5% 1	2076
March	1st to 10th	Night	71% 9% 8% 9% 3	5495
	11th to 20th	Night	74% 5% 7% 9% 5%	5432
	21st to end	Night	70% 7% 9% 11% 4	5071
April	1st to 10th	Night	72% 5% 7% 10% 6% 1	2100
	11th to 20th	Night	62% 6% 9% 16% 7%	1983
	21st to end	Night	66% 5% 8% 13% 7% 1	1867
May	1st to 10th	Night	66% 6% 11% 14% 3	4697
	11th to 20th	Night	58% 7% 11% 18% 5%	4671
	21st to end	Night	59% 5% 10% 21% 5%	4734
June	1st to 10th	Night	64% 5% 9% 16% 7%	1470
	11th to 20th	Night	53% 7% 16% 18% 6%	1470
	21st to end	Night	56% 9% 13% 16% 7%	1470
July	1st to 10th	Night	56% 7% 14% 19% 5%	3254
	11th to 20th	Night	47% 10% 15% 22% 6%	3613
	21st to end	Night	50% 7% 16% 24% 3	3831
August	1st to 10th	Night	48% 10% 18% 23% 2	2585
	11th to 20th	Night	46% 8% 18% 20% 5% 2	2736
	21st to end	Night	47% 9% 18% 22% 4	3441
September	1st to 10th	Night	50% 7% 14% 23% 6%	2000
	11th to 20th	Night	57% 8% 13% 15% 6%	2119
	21st to end	Night	57% 5% 15% 18% 6%	2200
October	1st to 10th	Night	57% 9% 15% 15% 5%	3749
	11th to 20th	Night	62% 9% 13% 12% 4	4151
	21st to end	Night	60% 6% 13% 16% 4	4610
November	1st to 10th	Night	72% 8% 9% 9% 2	2668
	11th to 20th	Night	75% 6% 8% 9% 2	2938
	21st to end	Night	79% 6% 7% 5% 3	3150
December	1st to 10th	Night	70% 10% 9% 8% 3	5050
	11th to 20th	Night	74% 8% 11% 5% 2	5733
	21st to end	Night	78% 8% 7% 7% 1	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	27% 20% 30% 16% 7% 1	430
	11th to 20th	Day	27% 20% 26% 18% 7% 3	430
	21st to end	Day	21% 21% 31% 21% 6%	473
February	1st to 10th	Day	26% 21% 27% 17% 7% 3	430
	11th to 20th	Day	26% 29% 24% 17% 3 1	426
	21st to end	Day	21% 21% 31% 17% 7% 3	355
March	1st to 10th	Day	25% 25% 30% 13% 5% 2	430
	11th to 20th	Day	28% 21% 23% 15% 9% 3	430
	21st to end	Day	31% 18% 28% 15% 6% 1	593
April	1st to 10th	Day	28% 29% 25% 13% 4	540
	11th to 20th	Day	29% 18% 29% 17% 5% 2	624
	21st to end	Day	32% 17% 24% 17% 8% 3	750
May	1st to 10th	Day	36% 16% 21% 19% 6% 2	753
	11th to 20th	Day	30% 16% 23% 17% 11% 3	774
	21st to end	Day	31% 17% 27% 18% 5% 2	845
June	1st to 10th	Day	36% 11% 26% 18% 7% 2	780
	11th to 20th	Day	30% 12% 28% 21% 9% 1	780
	21st to end	Day	26% 13% 29% 18% 9% 5%	780
July	1st to 10th	Day	25% 13% 30% 21% 8% 3	770
	11th to 20th	Day	18% 13% 33% 23% 12% 1	743
	21st to end	Day	23% 13% 29% 24% 9% 2	795
August	1st to 10th	Day	20% 10% 27% 26% 14% 3	725
	11th to 20th	Day	22% 9% 29% 25% 11% 4	717
	21st to end	Day	22% 13% 27% 24% 10% 4	677
September	1st to 10th	Day	24% 16% 32% 19% 8% 2	530
	11th to 20th	Day	30% 17% 30% 14% 8% 1	464
	21st to end	Day	25% 19% 33% 16% 6% 2	420
October	1st to 10th	Day	22% 23% 29% 16% 8% 2	420
	11th to 20th	Day	31% 17% 20% 19% 9% 4	420
	21st to end	Day	31% 19% 22% 18% 9% 2	462
November	1st to 10th	Day	36% 20% 25% 14% 4	425
	11th to 20th	Day	34% 22% 21% 15% 7% 2	430
	21st to end	Day	36% 23% 23% 14% 3	430
December	1st to 10th	Day	27% 20% 32% 15% 6%	430
	11th to 20th	Day	29% 24% 28% 15% 4	430
	21st to end	Day	25% 20% 26% 18% 8% 3	473
January	1st to 10th	Night	27% 17% 31% 19% 5% 1	950
	11th to 20th	Night	22% 21% 31% 19% 6% 1	950
	21st to end	Night	22% 23% 29% 22% 4	1045
February	1st to 10th	Night	22% 20% 31% 20% 6% 1	950
	11th to 20th	Night	25% 19% 30% 20% 5% 1	834
	21st to end	Night	21% 15% 30% 22% 10% 2	692
March	1st to 10th	Night	24% 23% 30% 18% 5% 1	840
	11th to 20th	Night	22% 17% 28% 24% 8%	790
	21st to end	Night	26% 16% 29% 23% 6%	693
April	1st to 10th	Night	29% 20% 28% 19% 4	630
	11th to 20th	Night	24% 14% 33% 23% 6% 1	624
	21st to end	Night	31% 11% 27% 24% 6%	630
May	1st to 10th	Night	32% 11% 25% 24% 7% 1	630
	11th to 20th	Night	30% 10% 24% 26% 9%	622
	21st to end	Night	32% 11% 28% 23% 6%	682
June	1st to 10th	Night	35% 9% 24% 24% 7%	630
	11th to 20th	Night	28% 7% 27% 29% 9%	630
	21st to end	Night	25% 10% 28% 27% 9% 1	630
July	1st to 10th	Night	24% 10% 31% 26% 9%	616
	11th to 20th	Night	18% 9% 31% 32% 10%	598
	21st to end	Night	25% 7% 27% 32% 9%	656
August	1st to 10th	Night	18% 7% 28% 33% 13% 1	598
	11th to 20th	Night	23% 6% 28% 29% 13% 1	592
	21st to end	Night	20% 7% 28% 30% 14% 1	660
September	1st to 10th	Night	23% 10% 32% 27% 8%	600
	11th to 20th	Night	30% 12% 26% 28% 5%	600
	21st to end	Night	28% 13% 32% 21% 6% 1	600
October	1st to 10th	Night	26% 14% 27% 27% 6%	694
	11th to 20th	Night	29% 13% 25% 23% 8% 1	883
	21st to end	Night	31% 14% 26% 20% 8%	1001
November	1st to 10th	Night	35% 19% 25% 18% 4	930
	11th to 20th	Night	36% 16% 25% 17% 6% 1	950
	21st to end	Night	34% 20% 27% 16% 2	950
December	1st to 10th	Night	29% 19% 26% 19% 6%	950
	11th to 20th	Night	30% 23% 28% 16% 3	950
	21st to end	Night	24% 18% 27% 21% 8% 1	1045

Page generated at 2026-07-13 04:14:52. Version ac07

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