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 2025-03-12.

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% 14% 5% 11% 7% 5% 5% 4 5% 6% 21%	108577
	Night	18% 13% 5% 12% 7% 6% 5% 4 5% 6% 18%	110609
Transparency	Day	64% 7% 10% 13% 5%	112043
	Night	67% 7% 10% 12% 4	115326
Seeing	Day	28% 17% 27% 19% 8% 2	18395
	Night	27% 15% 28% 23% 7% 1	25562

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% 25% 8% 16% 8% 7% 4 3 3 4 9%	3501
	11th to 20th	Day	14% 15% 7% 24% 10% 7% 5% 4 4 3 7%	3591
	21st to end	Day	5% 11% 7% 16% 16% 12% 9% 5% 6% 4 9%	3982
February	1st to 10th	Day	16% 13% 6% 14% 15% 9% 7% 3 5% 4 9%	1600
	11th to 20th	Day	15% 20% 6% 13% 10% 7% 6% 3 5% 4 11%	1812
	21st to end	Day	13% 14% 6% 14% 9% 9% 7% 4 6% 5% 14%	1650
March	1st to 10th	Day	11% 20% 5% 12% 8% 7% 5% 3 5% 6% 19%	3214
	11th to 20th	Day	17% 26% 9% 12% 7% 6% 4 3 3 3 9%	3253
	21st to end	Day	25% 15% 7% 12% 6% 4 4 2 4 4 17%	4163
April	1st to 10th	Day	21% 21% 6% 13% 7% 6% 4 3 4 4 13%	2280
	11th to 20th	Day	18% 16% 4 10% 5% 4 4 3 5% 6% 26%	2337
	21st to end	Day	22% 19% 6% 10% 4 3 4 3 3 4 22%	2489
May	1st to 10th	Day	25% 20% 5% 9% 4 3 3 2 3 4 21%	4425
	11th to 20th	Day	18% 13% 4 9% 5% 5% 5% 4 5% 7% 26%	4398
	21st to end	Day	29% 12% 3 7% 4 4 4 3 5% 6% 22%	5051
June	1st to 10th	Day	32% 12% 4 8% 5% 4 4 3 4 6% 17%	2850
	11th to 20th	Day	23% 10% 3 7% 5% 4 5% 4 6% 7% 28%	2850
	21st to end	Day	25% 11% 3 7% 5% 4 4 4 6% 6% 26%	2850
July	1st to 10th	Day	16% 12% 4 10% 6% 6% 5% 5% 6% 6% 24%	4721
	11th to 20th	Day	14% 9% 3 8% 7% 7% 7% 5% 6% 7% 27%	4440
	21st to end	Day	16% 6% 3 6% 5% 5% 5% 4 7% 8% 35%	4815
August	1st to 10th	Day	20% 8% 3 8% 5% 5% 5% 4 6% 8% 27%	4424
	11th to 20th	Day	19% 8% 3 6% 4 4 4 3 5% 6% 38%	4210
	21st to end	Day	22% 7% 3 7% 5% 4 5% 4 6% 7% 30%	4322
September	1st to 10th	Day	23% 9% 3 6% 4 4 5% 3 5% 7% 31%	2280
	11th to 20th	Day	24% 9% 3 8% 6% 5% 5% 4 5% 7% 24%	2166
	21st to end	Day	20% 11% 5% 10% 5% 5% 4 4 5% 8% 25%	2090
October	1st to 10th	Day	22% 11% 3 7% 4 5% 4 3 5% 7% 30%	1999
	11th to 20th	Day	24% 14% 5% 9% 5% 5% 5% 4 5% 5% 20%	1757
	21st to end	Day	23% 15% 5% 12% 7% 4 4 3 4 5% 18%	1881
November	1st to 10th	Day	23% 19% 6% 12% 6% 6% 5% 3 4 5% 11%	1760
	11th to 20th	Day	23% 19% 6% 12% 6% 5% 5% 3 4 5% 13%	1600
	21st to end	Day	22% 19% 6% 15% 6% 6% 6% 3 4 4 10%	1400
December	1st to 10th	Day	12% 14% 6% 17% 9% 7% 6% 4 6% 7% 11%	2290
	11th to 20th	Day	24% 15% 6% 15% 9% 5% 6% 3 5% 4 8%	2628
	21st to end	Day	18% 14% 6% 18% 10% 6% 5% 3 4 4 11%	3498
January	1st to 10th	Night	14% 22% 9% 15% 10% 6% 5% 3 4 4 8%	6462
	11th to 20th	Night	13% 13% 6% 24% 9% 7% 6% 5% 5% 4 8%	6314
	21st to end	Night	5% 9% 7% 19% 11% 11% 9% 5% 6% 6% 12%	6996
February	1st to 10th	Night	14% 14% 5% 15% 14% 10% 6% 4 5% 5% 8%	2800
	11th to 20th	Night	14% 18% 6% 15% 11% 8% 5% 4 4 4 10%	2470
	21st to end	Night	11% 14% 4 13% 10% 8% 8% 4 6% 5% 17%	1980
March	1st to 10th	Night	14% 17% 5% 11% 9% 8% 6% 4 5% 6% 16%	3846
	11th to 20th	Night	15% 24% 8% 14% 6% 6% 4 3 4 4 11%	3734
	21st to end	Night	22% 15% 8% 12% 5% 4 4 3 4 5% 18%	3465
April	1st to 10th	Night	23% 18% 5% 11% 5% 5% 4 3 4 6% 17%	1900
	11th to 20th	Night	18% 14% 5% 8% 7% 5% 5% 4 5% 6% 22%	1793
	21st to end	Night	23% 15% 5% 9% 5% 4 4 4 4 5% 22%	1689
May	1st to 10th	Night	23% 19% 5% 10% 5% 4 3 3 4 5% 19%	2525
	11th to 20th	Night	19% 12% 3 8% 4 4 4 4 6% 7% 29%	2506
	21st to end	Night	31% 9% 3 6% 4 4 4 4 6% 5% 23%	2517
June	1st to 10th	Night	31% 11% 4 8% 5% 4 4 3 4 6% 20%	1330
	11th to 20th	Night	21% 7% 3 5% 5% 5% 4 4 7% 8% 31%	1330
	21st to end	Night	24% 10% 2 8% 5% 5% 5% 4 5% 8% 24%	1330
July	1st to 10th	Night	22% 9% 3 8% 5% 5% 4 4 6% 7% 27%	2244
	11th to 20th	Night	15% 9% 3 8% 5% 6% 6% 4 7% 9% 28%	2530
	21st to end	Night	17% 7% 3 6% 4 4 4 3 5% 7% 41%	2750
August	1st to 10th	Night	13% 8% 3 9% 6% 6% 6% 5% 7% 8% 30%	2516
	11th to 20th	Night	19% 6% 3 6% 4 4 5% 4 4 7% 38%	2627
	21st to end	Night	20% 6% 2 6% 4 4 5% 4 6% 7% 36%	3337
September	1st to 10th	Night	20% 9% 3 7% 4 4 5% 4 5% 6% 33%	1900
	11th to 20th	Night	24% 9% 4 7% 5% 5% 5% 4 4 6% 28%	2013
	21st to end	Night	22% 9% 3 7% 4 5% 5% 4 6% 8% 27%	2090
October	1st to 10th	Night	21% 10% 3 7% 5% 5% 5% 3 6% 9% 26%	2179
	11th to 20th	Night	22% 11% 4 9% 5% 6% 5% 3 5% 7% 22%	2422
	21st to end	Night	24% 13% 3 10% 5% 5% 4 3 4 6% 21%	2717
November	1st to 10th	Night	22% 16% 5% 11% 7% 6% 5% 4 5% 5% 15%	2538
	11th to 20th	Night	24% 17% 6% 10% 6% 6% 4 4 5% 6% 12%	2798
	21st to end	Night	22% 18% 8% 14% 7% 5% 4 3 4 4 11%	3000
December	1st to 10th	Night	15% 15% 7% 14% 8% 7% 7% 5% 7% 7% 10%	4900
	11th to 20th	Night	23% 12% 6% 14% 8% 6% 5% 4 5% 6% 12%	5581
	21st to end	Night	16% 15% 7% 18% 10% 6% 5% 4 4 4 10%	7480

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	79% 6% 6% 6% 3	3502
	11th to 20th	Day	80% 7% 8% 3 1	3620
	21st to end	Day	73% 10% 5% 6% 4 2	3982
February	1st to 10th	Day	76% 8% 7% 6% 3 1	1600
	11th to 20th	Day	78% 7% 5% 7% 3	1820
	21st to end	Day	70% 8% 6% 10% 5% 1	1650
March	1st to 10th	Day	66% 6% 8% 12% 7% 1	3218
	11th to 20th	Day	80% 5% 4 7% 4	3253
	21st to end	Day	71% 5% 5% 13% 5%	4163
April	1st to 10th	Day	76% 5% 6% 8% 4 1	2280
	11th to 20th	Day	61% 5% 9% 16% 8% 1	2337
	21st to end	Day	67% 5% 7% 13% 8% 1	2489
May	1st to 10th	Day	68% 4 9% 14% 4	4440
	11th to 20th	Day	57% 7% 13% 16% 7%	4402
	21st to end	Day	62% 5% 10% 14% 8%	5051
June	1st to 10th	Day	69% 5% 10% 11% 5%	2850
	11th to 20th	Day	56% 5% 13% 21% 5%	2850
	21st to end	Day	59% 7% 11% 15% 7% 1	2850
July	1st to 10th	Day	59% 7% 10% 18% 5%	4646
	11th to 20th	Day	52% 10% 15% 19% 4	4364
	21st to end	Day	43% 8% 21% 23% 4	4662
August	1st to 10th	Day	52% 9% 15% 20% 4	4410
	11th to 20th	Day	47% 7% 15% 19% 10% 2	4252
	21st to end	Day	53% 6% 15% 21% 5%	4322
September	1st to 10th	Day	51% 6% 12% 22% 8% 1	2280
	11th to 20th	Day	60% 6% 13% 16% 5% 1	2166
	21st to end	Day	58% 6% 15% 14% 7%	2090
October	1st to 10th	Day	58% 9% 12% 16% 5% 1	3324
	11th to 20th	Day	64% 8% 14% 10% 4	2903
	21st to end	Day	63% 7% 10% 14% 5%	3092
November	1st to 10th	Day	77% 5% 9% 7% 1	1760
	11th to 20th	Day	73% 7% 7% 11% 3	1600
	21st to end	Day	78% 7% 8% 5% 2	1400
December	1st to 10th	Day	69% 9% 10% 10% 2	2290
	11th to 20th	Day	79% 9% 8% 3 2	2627
	21st to end	Day	77% 7% 7% 7% 1	3498
January	1st to 10th	Night	79% 7% 5% 6% 3	6462
	11th to 20th	Night	79% 9% 6% 5% 1	6360
	21st to end	Night	71% 8% 8% 6% 5% 1	6996
February	1st to 10th	Night	80% 6% 6% 6% 2	2800
	11th to 20th	Night	80% 7% 6% 6% 1	2473
	21st to end	Night	71% 5% 8% 10% 5%	1980
March	1st to 10th	Night	69% 7% 9% 11% 4	3855
	11th to 20th	Night	79% 5% 5% 8% 3	3735
	21st to end	Night	69% 5% 9% 12% 4 1	3465
April	1st to 10th	Night	72% 5% 7% 9% 6% 1	1900
	11th to 20th	Night	63% 5% 9% 15% 7%	1793
	21st to end	Night	65% 6% 8% 12% 8% 1	1689
May	1st to 10th	Night	68% 5% 9% 13% 4	2530
	11th to 20th	Night	56% 9% 12% 18% 6%	2507
	21st to end	Night	62% 7% 10% 18% 4	2518
June	1st to 10th	Night	67% 6% 9% 13% 5%	1330
	11th to 20th	Night	52% 7% 17% 18% 6%	1330
	21st to end	Night	57% 8% 13% 15% 7%	1330
July	1st to 10th	Night	56% 7% 13% 18% 6%	2210
	11th to 20th	Night	50% 11% 15% 18% 5%	2482
	21st to end	Night	43% 7% 16% 29% 4	2663
August	1st to 10th	Night	49% 10% 18% 22% 1	2505
	11th to 20th	Night	47% 8% 18% 20% 5% 2	2651
	21st to end	Night	47% 9% 19% 22% 4	3336
September	1st to 10th	Night	51% 7% 13% 22% 6%	1900
	11th to 20th	Night	58% 7% 13% 15% 7%	2013
	21st to end	Night	57% 5% 14% 17% 6%	2090
October	1st to 10th	Night	57% 9% 15% 14% 5%	3634
	11th to 20th	Night	62% 9% 13% 11% 4	4023
	21st to end	Night	61% 6% 13% 15% 4	4467
November	1st to 10th	Night	72% 8% 9% 9% 2	2538
	11th to 20th	Night	75% 6% 8% 9% 2	2798
	21st to end	Night	79% 5% 7% 6% 3	3000
December	1st to 10th	Night	70% 10% 9% 8% 3	4900
	11th to 20th	Night	74% 8% 11% 5% 2	5583
	21st to end	Night	78% 8% 7% 7% 1	7480

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% 20% 30% 15% 7% 1	400
	11th to 20th	Day	24% 20% 27% 18% 8% 3	400
	21st to end	Day	21% 20% 30% 22% 6%	440
February	1st to 10th	Day	26% 22% 29% 16% 6% 2	400
	11th to 20th	Day	26% 29% 26% 16% 2 1	396
	21st to end	Day	20% 22% 31% 17% 8% 3	331
March	1st to 10th	Day	25% 23% 29% 15% 6% 2	400
	11th to 20th	Day	28% 21% 24% 15% 10% 3	373
	21st to end	Day	31% 17% 29% 15% 7% 2	505
April	1st to 10th	Day	27% 28% 24% 15% 5%	460
	11th to 20th	Day	29% 18% 27% 18% 6% 2	535
	21st to end	Day	31% 18% 26% 17% 6% 2	650
May	1st to 10th	Day	37% 15% 20% 20% 6% 2	653
	11th to 20th	Day	28% 16% 23% 17% 12% 3	674
	21st to end	Day	32% 17% 27% 19% 4 1	735
June	1st to 10th	Day	38% 10% 24% 18% 8% 2	680
	11th to 20th	Day	31% 10% 27% 21% 9% 1	680
	21st to end	Day	27% 12% 29% 19% 8% 5%	680
July	1st to 10th	Day	26% 13% 28% 21% 9% 3	670
	11th to 20th	Day	19% 12% 33% 23% 12% 1	668
	21st to end	Day	22% 12% 29% 25% 9% 2	740
August	1st to 10th	Day	21% 10% 26% 26% 14% 3	675
	11th to 20th	Day	22% 9% 30% 25% 11% 4	667
	21st to end	Day	22% 13% 27% 24% 10% 3	629
September	1st to 10th	Day	25% 16% 32% 18% 7% 2	490
	11th to 20th	Day	31% 16% 30% 14% 8%	430
	21st to end	Day	24% 19% 33% 16% 6% 2	390
October	1st to 10th	Day	23% 22% 30% 15% 8% 3	390
	11th to 20th	Day	32% 18% 19% 20% 8% 3	390
	21st to end	Day	33% 19% 22% 17% 8% 1	429
November	1st to 10th	Day	36% 21% 25% 14% 4 1	395
	11th to 20th	Day	33% 21% 21% 15% 7% 2	400
	21st to end	Day	37% 23% 22% 15% 3	400
December	1st to 10th	Day	28% 19% 32% 16% 6%	400
	11th to 20th	Day	29% 23% 29% 15% 4	400
	21st to end	Day	24% 20% 26% 18% 8% 3	440
January	1st to 10th	Night	27% 17% 30% 19% 6% 1	900
	11th to 20th	Night	21% 21% 31% 19% 7% 1	900
	21st to end	Night	21% 22% 30% 23% 4	990
February	1st to 10th	Night	22% 20% 31% 20% 5% 1	900
	11th to 20th	Night	25% 19% 31% 20% 4	793
	21st to end	Night	20% 15% 31% 22% 11% 2	660
March	1st to 10th	Night	24% 22% 30% 18% 5% 1	800
	11th to 20th	Night	21% 16% 28% 26% 9%	722
	21st to end	Night	27% 15% 29% 22% 7%	627
April	1st to 10th	Night	29% 19% 28% 19% 5%	570
	11th to 20th	Night	24% 14% 32% 23% 6% 1	564
	21st to end	Night	31% 12% 28% 24% 6%	570
May	1st to 10th	Night	31% 11% 25% 25% 8% 1	570
	11th to 20th	Night	29% 11% 23% 27% 10%	562
	21st to end	Night	32% 10% 28% 23% 7%	616
June	1st to 10th	Night	36% 9% 23% 23% 8% 1	570
	11th to 20th	Night	27% 6% 28% 29% 9%	570
	21st to end	Night	25% 9% 29% 26% 9% 1	570
July	1st to 10th	Night	24% 9% 31% 25% 9% 1	556
	11th to 20th	Night	19% 9% 30% 32% 10%	552
	21st to end	Night	24% 7% 27% 32% 9%	623
August	1st to 10th	Night	19% 7% 28% 33% 13% 1	568
	11th to 20th	Night	23% 6% 28% 29% 12% 1	562
	21st to end	Night	20% 7% 29% 29% 15% 1	627
September	1st to 10th	Night	23% 10% 33% 25% 8%	570
	11th to 20th	Night	31% 11% 26% 27% 4	570
	21st to end	Night	27% 13% 32% 21% 7% 1	570
October	1st to 10th	Night	26% 14% 27% 25% 6%	659
	11th to 20th	Night	29% 14% 26% 23% 8% 1	835
	21st to end	Night	33% 15% 26% 19% 8%	946
November	1st to 10th	Night	34% 19% 24% 19% 4	880
	11th to 20th	Night	35% 16% 24% 18% 6% 1	900
	21st to end	Night	34% 20% 27% 17% 2	900
December	1st to 10th	Night	29% 19% 26% 20% 6%	900
	11th to 20th	Night	30% 22% 28% 17% 3	900
	21st to end	Night	23% 18% 28% 22% 8% 1	990

Page generated at 2025-03-09 09:08:49. Version ac07

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