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 2025-11-03.

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	18% 7% 2 6% 4 4 4 3 5% 7% 40%	126506
	Night	19% 8% 2 6% 4 4 4 3 5% 6% 41%	123540
Transparency	Day	28% 38% 8% 14% 10% 2	130037
	Night	28% 38% 7% 14% 11% 2	128096
Seeing	Day	21% 15% 32% 21% 9% 2	16346
	Night	21% 13% 31% 25% 9% 1	25329

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% 8% 2 6% 4 4 4 3 5% 5% 46%	3597
	11th to 20th	Day	14% 9% 2 5% 3 4 3 3 5% 5% 45%	3570
	21st to end	Day	19% 8% 3 7% 4 3 3 3 4 4 41%	4049
February	1st to 10th	Day	18% 8% 2 5% 5% 4 5% 4 4 6% 38%	1893
	11th to 20th	Day	15% 7% 2 6% 5% 4 4 3 5% 6% 42%	1948
	21st to end	Day	20% 9% 3 5% 5% 4 3 4 5% 6% 37%	1650
March	1st to 10th	Day	24% 9% 2 5% 4 3 3 2 4 5% 40%	4476
	11th to 20th	Day	14% 8% 2 6% 5% 5% 4 3 5% 7% 41%	4648
	21st to end	Day	22% 7% 2 6% 4 4 4 4 5% 7% 35%	5968
April	1st to 10th	Day	20% 7% 2 5% 4 4 4 3 5% 6% 39%	2400
	11th to 20th	Day	21% 6% 2 5% 4 3 3 3 5% 6% 41%	2374
	21st to end	Day	21% 6% 2 5% 4 4 4 4 5% 5% 41%	2523
May	1st to 10th	Day	31% 8% 2 5% 3 4 4 3 5% 8% 27%	5886
	11th to 20th	Day	22% 8% 3 7% 4 4 4 3 5% 6% 35%	6061
	21st to end	Day	22% 6% 3 6% 4 4 4 4 5% 7% 35%	6949
June	1st to 10th	Day	18% 6% 2 5% 4 4 5% 4 7% 9% 36%	2800
	11th to 20th	Day	18% 6% 2 5% 3 4 5% 4 6% 9% 39%	2800
	21st to end	Day	14% 6% 2 6% 4 4 5% 4 6% 8% 40%	2800
July	1st to 10th	Day	17% 7% 3 6% 5% 4 5% 3 6% 9% 34%	6360
	11th to 20th	Day	14% 6% 2 7% 4 4 5% 4 7% 10% 36%	6360
	21st to end	Day	16% 7% 2 6% 4 3 4 3 6% 8% 41%	6926
August	1st to 10th	Day	20% 7% 2 7% 4 4 5% 4 6% 8% 33%	4349
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 6% 8% 43%	3893
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 4 7% 9% 44%	4312
September	1st to 10th	Day	14% 6% 2 6% 4 3 4 4 5% 6% 46%	2400
	11th to 20th	Day	13% 5% 2 5% 3 3 3 3 4 7% 52%	2247
	21st to end	Day	20% 6% 2 6% 3 4 4 4 5% 6% 40%	2200
October	1st to 10th	Day	21% 5% 2 5% 3 3 4 3 4 5% 44%	2192
	11th to 20th	Day	15% 5% 2 4 3 3 5% 3 5% 8% 47%	1970
	21st to end	Day	18% 6% 2 5% 4 4 4 3 5% 6% 42%	1980
November	1st to 10th	Day	14% 6% 3 5% 4 4 3 3 4 6% 49%	1779
	11th to 20th	Day	19% 5% 2 4 3 3 3 3 4 6% 49%	1800
	21st to end	Day	17% 7% 2 4 3 4 4 3 4 7% 45%	1800
December	1st to 10th	Day	16% 6% 2 6% 4 4 3 3 4 6% 46%	2600
	11th to 20th	Day	21% 7% 2 5% 3 2 2 3 3 5% 46%	2986
	21st to end	Day	21% 9% 3 6% 4 3 3 2 4 5% 40%	3960
January	1st to 10th	Night	14% 5% 2 5% 3 3 4 3 5% 6% 49%	6349
	11th to 20th	Night	15% 7% 3 7% 4 3 3 3 4 5% 47%	6315
	21st to end	Night	18% 9% 3 7% 4 4 4 3 4 5% 38%	6904
February	1st to 10th	Night	17% 9% 3 6% 4 4 3 3 4 6% 40%	2505
	11th to 20th	Night	18% 8% 2 6% 4 3 3 3 5% 6% 41%	2338
	21st to end	Night	21% 8% 2 6% 4 4 4 3 5% 5% 40%	1980
March	1st to 10th	Night	22% 10% 2 5% 3 3 3 3 4 5% 40%	5364
	11th to 20th	Night	17% 10% 3 6% 4 4 4 3 4 6% 40%	5311
	21st to end	Night	21% 9% 3 7% 4 4 4 3 4 4 37%	4962
April	1st to 10th	Night	21% 8% 2 6% 4 3 4 3 5% 6% 37%	2000
	11th to 20th	Night	20% 6% 2 6% 4 4 4 3 4 5% 41%	1975
	21st to end	Night	21% 6% 2 6% 4 3 3 4 4 5% 41%	1875
May	1st to 10th	Night	28% 11% 3 7% 4 4 4 3 4 6% 26%	4054
	11th to 20th	Night	23% 10% 3 6% 4 4 4 3 5% 7% 31%	3861
	21st to end	Night	23% 9% 3 6% 4 4 4 3 5% 7% 34%	3926
June	1st to 10th	Night	19% 6% 2 6% 4 5% 4 4 5% 6% 38%	1600
	11th to 20th	Night	19% 6% 2 5% 4 3 4 4 4 10% 39%	1600
	21st to end	Night	14% 7% 2 5% 4 4 4 4 6% 9% 41%	1600
July	1st to 10th	Night	19% 8% 3 7% 4 4 4 4 6% 8% 33%	3600
	11th to 20th	Night	21% 8% 3 6% 5% 4 4 4 5% 8% 32%	3600
	21st to end	Night	15% 8% 2 5% 4 4 4 4 5% 7% 42%	3926
August	1st to 10th	Night	24% 7% 2 7% 5% 4 5% 4 6% 7% 29%	2769
	11th to 20th	Night	12% 7% 2 7% 5% 5% 5% 4 6% 7% 40%	3150
	21st to end	Night	9% 5% 2 4 3 3 4 3 4 8% 54%	3586
September	1st to 10th	Night	14% 6% 3 6% 4 4 5% 4 5% 6% 43%	2000
	11th to 20th	Night	13% 6% 2 5% 4 3 3 2 4 5% 53%	2152
	21st to end	Night	20% 6% 2 6% 4 4 5% 4 4 5% 41%	2200
October	1st to 10th	Night	19% 7% 2 6% 5% 3 3 3 4 6% 43%	2205
	11th to 20th	Night	16% 6% 2 5% 4 3 3 3 4 5% 48%	2430
	21st to end	Night	21% 7% 2 5% 3 3 4 3 5% 6% 41%	2860
November	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 6% 49%	2564
	11th to 20th	Night	18% 7% 2 5% 3 3 3 3 4 5% 48%	2600
	21st to end	Night	16% 6% 2 5% 4 3 4 3 4 8% 46%	2600
December	1st to 10th	Night	17% 7% 2 4 3 3 3 3 4 5% 48%	4575
	11th to 20th	Night	26% 7% 2 4 3 3 3 3 3 4 42%	5208
	21st to end	Night	20% 9% 3 6% 3 3 3 2 4 4 42%	6996

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	28% 27% 3 23% 15% 3	3598
	11th to 20th	Day	27% 28% 8% 18% 13% 7%	3600
	21st to end	Day	36% 29% 7% 15% 12% 1	4049
February	1st to 10th	Day	19% 62% 6% 8% 4 1	1893
	11th to 20th	Day	18% 60% 2 9% 9% 1	1957
	21st to end	Day	17% 62% 5% 8% 5% 2	1650
March	1st to 10th	Day	34% 30% 7% 11% 9% 9%	4479
	11th to 20th	Day	26% 31% 11% 23% 8% 1	4648
	21st to end	Day	35% 29% 7% 10% 14% 5%	5968
April	1st to 10th	Day	21% 62% 4 6% 6% 1	2400
	11th to 20th	Day	16% 62% 3 8% 9% 1	2374
	21st to end	Day	18% 62% 3 10% 7% 1	2523
May	1st to 10th	Day	42% 31% 14% 8% 5%	5897
	11th to 20th	Day	37% 30% 11% 13% 8% 1	6065
	21st to end	Day	37% 30% 7% 17% 9%	6949
June	1st to 10th	Day	17% 62% 3 11% 7%	2800
	11th to 20th	Day	16% 61% 5% 10% 6% 1	2800
	21st to end	Day	15% 61% 5% 11% 8% 1	2800
July	1st to 10th	Day	37% 29% 8% 15% 10% 1	6290
	11th to 20th	Day	35% 26% 15% 16% 7%	6285
	21st to end	Day	32% 25% 8% 19% 15% 1	6728
August	1st to 10th	Day	34% 36% 10% 14% 5% 1	4335
	11th to 20th	Day	24% 36% 11% 24% 5%	3930
	21st to end	Day	20% 37% 10% 22% 10% 1	4312
September	1st to 10th	Day	16% 58% 6% 12% 8%	2400
	11th to 20th	Day	15% 57% 4 10% 12% 1	2247
	21st to end	Day	22% 57% 5% 8% 7% 1	2200
October	1st to 10th	Day	21% 36% 7% 13% 18% 5%	3569
	11th to 20th	Day	15% 35% 5% 15% 27% 3	3186
	21st to end	Day	18% 36% 10% 18% 16% 2	3180
November	1st to 10th	Day	17% 56% 7% 9% 10% 1	1779
	11th to 20th	Day	15% 56% 3 10% 14% 3	1800
	21st to end	Day	16% 57% 6% 13% 6% 2	1800
December	1st to 10th	Day	25% 36% 10% 21% 9%	2600
	11th to 20th	Day	29% 31% 9% 13% 16% 3	2986
	21st to end	Day	36% 28% 4 15% 13% 5%	3960
January	1st to 10th	Night	26% 26% 6% 22% 17% 3	6349
	11th to 20th	Night	29% 26% 9% 16% 15% 5%	6360
	21st to end	Night	38% 29% 6% 12% 11% 4	6904
February	1st to 10th	Night	18% 62% 5% 10% 4 1	2505
	11th to 20th	Night	17% 60% 2 8% 10% 2	2340
	21st to end	Night	19% 61% 3 8% 7% 2	1980
March	1st to 10th	Night	36% 29% 7% 11% 10% 7%	5374
	11th to 20th	Night	32% 30% 12% 16% 7% 3	5312
	21st to end	Night	38% 30% 4 7% 18% 4	4962
April	1st to 10th	Night	20% 61% 4 8% 6% 2	2000
	11th to 20th	Night	17% 62% 5% 8% 8% 1	1975
	21st to end	Night	17% 62% 4 9% 8% 1	1875
May	1st to 10th	Night	45% 30% 11% 8% 5%	4060
	11th to 20th	Night	40% 31% 10% 10% 6% 2	3862
	21st to end	Night	39% 30% 9% 16% 5%	3927
June	1st to 10th	Night	18% 62% 2 8% 9% 1	1600
	11th to 20th	Night	16% 62% 5% 11% 6%	1600
	21st to end	Night	15% 61% 4 11% 8% 1	1600
July	1st to 10th	Night	40% 27% 8% 15% 8% 1	3560
	11th to 20th	Night	41% 26% 12% 14% 7%	3552
	21st to end	Night	32% 25% 10% 19% 14% 1	3809
August	1st to 10th	Night	41% 37% 8% 9% 5% 1	2759
	11th to 20th	Night	28% 36% 10% 21% 4	3179
	21st to end	Night	14% 36% 11% 24% 15% 1	3586
September	1st to 10th	Night	17% 58% 4 13% 8% 1	2000
	11th to 20th	Night	16% 57% 4 10% 13% 1	2152
	21st to end	Night	23% 56% 4 8% 7% 1	2200
October	1st to 10th	Night	24% 36% 7% 16% 14% 2	3608
	11th to 20th	Night	12% 35% 5% 17% 27% 4	3953
	21st to end	Night	17% 35% 9% 20% 17% 2	4610
November	1st to 10th	Night	18% 56% 5% 10% 10% 1	2564
	11th to 20th	Night	16% 56% 3 9% 11% 4	2600
	21st to end	Night	17% 56% 5% 14% 6% 2	2600
December	1st to 10th	Night	26% 35% 7% 22% 10% 1	4575
	11th to 20th	Night	34% 31% 6% 12% 15% 2	5208
	21st to end	Night	34% 28% 7% 14% 14% 4	6996

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	26% 26% 32% 14% 4	200
	11th to 20th	Day	25% 34% 28% 12% 2 1	200
	21st to end	Day	23% 23% 35% 13% 4 1	239
February	1st to 10th	Day	26% 20% 38% 16% 1	393
	11th to 20th	Day	26% 26% 36% 11% 1	496
	21st to end	Day	26% 25% 32% 12% 4	414
March	1st to 10th	Day	23% 25% 33% 16% 3	500
	11th to 20th	Day	22% 22% 39% 14% 3 1	500
	21st to end	Day	28% 21% 35% 12% 3 1	550
April	1st to 10th	Day	27% 24% 31% 13% 5%	500
	11th to 20th	Day	25% 20% 33% 15% 5% 1	492
	21st to end	Day	26% 15% 35% 17% 5% 2	500
May	1st to 10th	Day	30% 16% 32% 15% 6% 2	503
	11th to 20th	Day	21% 15% 38% 19% 6% 1	527
	21st to end	Day	24% 8% 27% 26% 13% 2	573
June	1st to 10th	Day	19% 9% 34% 23% 13% 2	530
	11th to 20th	Day	19% 12% 32% 26% 10% 2	530
	21st to end	Day	16% 8% 31% 29% 13% 2	530
July	1st to 10th	Day	17% 6% 28% 29% 16% 4	525
	11th to 20th	Day	14% 5% 29% 34% 15% 4	524
	21st to end	Day	15% 7% 33% 34% 10% 2	576
August	1st to 10th	Day	14% 7% 28% 33% 13% 4	526
	11th to 20th	Day	15% 5% 27% 32% 16% 5%	519
	21st to end	Day	10% 9% 34% 28% 13% 6%	583
September	1st to 10th	Day	18% 10% 28% 24% 15% 5%	530
	11th to 20th	Day	13% 7% 35% 25% 13% 7%	530
	21st to end	Day	23% 9% 34% 23% 9% 2	530
October	1st to 10th	Day	26% 10% 26% 21% 14% 4	530
	11th to 20th	Day	17% 18% 32% 23% 9% 2	513
	21st to end	Day	25% 15% 34% 17% 7% 2	462
November	1st to 10th	Day	16% 13% 36% 22% 9% 2	401
	11th to 20th	Day	22% 22% 32% 19% 5%	400
	21st to end	Day	20% 22% 30% 22% 7%	400
December	1st to 10th	Day	23% 23% 33% 17% 6% 1	200
	11th to 20th	Day	28% 26% 33% 12% 2	200
	21st to end	Day	25% 20% 30% 15% 7% 1	220
January	1st to 10th	Night	21% 23% 36% 16% 4	800
	11th to 20th	Night	28% 20% 32% 19% 2	800
	21st to end	Night	20% 24% 32% 20% 3	880
February	1st to 10th	Night	21% 20% 37% 20% 2	800
	11th to 20th	Night	25% 20% 39% 14% 2	783
	21st to end	Night	24% 21% 35% 16% 3	660
March	1st to 10th	Night	25% 17% 34% 20% 4	800
	11th to 20th	Night	23% 13% 38% 21% 5% 1	800
	21st to end	Night	22% 17% 37% 19% 5%	880
April	1st to 10th	Night	26% 15% 33% 22% 4	800
	11th to 20th	Night	23% 14% 33% 26% 5%	791
	21st to end	Night	22% 12% 35% 23% 7% 1	675
May	1st to 10th	Night	27% 10% 29% 24% 9% 1	600
	11th to 20th	Night	24% 9% 37% 23% 8%	524
	21st to end	Night	23% 5% 23% 33% 14% 1	433
June	1st to 10th	Night	23% 6% 24% 32% 14% 1	400
	11th to 20th	Night	22% 4 22% 38% 14% 1	400
	21st to end	Night	17% 5% 23% 42% 14% 1	400
July	1st to 10th	Night	16% 5% 18% 40% 19% 1	390
	11th to 20th	Night	15% 5% 16% 44% 18% 2	388
	21st to end	Night	16% 4 23% 41% 15% 1	438
August	1st to 10th	Night	12% 4 23% 43% 17% 1	503
	11th to 20th	Night	15% 3 19% 41% 20% 2	755
	21st to end	Night	15% 5% 21% 36% 19% 4	880
September	1st to 10th	Night	15% 5% 28% 32% 17% 3	800
	11th to 20th	Night	16% 4 26% 31% 18% 5%	800
	21st to end	Night	23% 7% 25% 28% 15% 2	800
October	1st to 10th	Night	22% 10% 28% 24% 13% 4	800
	11th to 20th	Night	20% 14% 31% 24% 10% 1	800
	21st to end	Night	26% 12% 36% 19% 7%	880
November	1st to 10th	Night	17% 14% 34% 23% 11% 2	789
	11th to 20th	Night	21% 20% 32% 21% 6% 1	800
	21st to end	Night	19% 22% 33% 21% 5% 1	800
December	1st to 10th	Night	26% 19% 29% 21% 5% 1	800
	11th to 20th	Night	26% 20% 30% 20% 4	800
	21st to end	Night	26% 16% 38% 18% 2	880

Page generated at 2025-10-31 02:02:40. Version ac07

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