Sault Ste Marie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sault Ste Marie clear sky chart from 2005-11-06 to 2026-08-15.

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	14% 10% 4 8% 5% 5% 4 3 5% 7% 34%	143841
	Night	14% 12% 4 10% 6% 5% 5% 3 5% 6% 30%	138320
Transparency	Day	33% 35% 8% 16% 8% 1	147301
	Night	36% 35% 8% 14% 6% 1	142947
Seeing	Day	21% 17% 31% 20% 8% 2	17959
	Night	21% 12% 28% 28% 10% 1	27287

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% 19% 7% 17% 9% 6% 4 4 4 5% 16%	4454
	11th to 20th	Day	10% 15% 7% 13% 8% 7% 6% 4 5% 5% 19%	4679
	21st to end	Day	7% 16% 8% 15% 9% 8% 6% 4 5% 5% 17%	5156
February	1st to 10th	Day	10% 13% 6% 13% 10% 6% 5% 4 7% 6% 20%	1803
	11th to 20th	Day	12% 14% 5% 11% 7% 7% 5% 4 4 6% 23%	1942
	21st to end	Day	10% 13% 6% 14% 7% 5% 4 4 6% 7% 25%	1730
March	1st to 10th	Day	14% 12% 4 9% 5% 5% 5% 4 5% 7% 31%	4578
	11th to 20th	Day	14% 14% 4 9% 6% 5% 4 4 6% 7% 28%	5043
	21st to end	Day	19% 12% 7% 10% 5% 5% 4 3 4 5% 25%	5669
April	1st to 10th	Day	17% 12% 4 8% 5% 4 5% 3 5% 6% 31%	2520
	11th to 20th	Day	19% 11% 4 7% 4 5% 4 3 5% 5% 34%	2681
	21st to end	Day	17% 10% 4 6% 4 4 4 5% 5% 7% 34%	2730
May	1st to 10th	Day	14% 9% 3 7% 5% 4 4 4 5% 6% 40%	7642
	11th to 20th	Day	18% 8% 2 6% 4 3 3 3 4 6% 42%	7924
	21st to end	Day	14% 8% 3 5% 3 3 4 3 5% 7% 46%	9652
June	1st to 10th	Day	15% 6% 2 5% 4 4 5% 4 6% 8% 40%	3150
	11th to 20th	Day	12% 7% 3 7% 5% 5% 5% 5% 7% 8% 37%	3150
	21st to end	Day	16% 7% 3 6% 4 4 4 4 6% 7% 39%	3150
July	1st to 10th	Day	12% 7% 2 5% 4 4 4 4 6% 9% 43%	8879
	11th to 20th	Day	10% 6% 2 7% 4 4 4 4 6% 10% 44%	8306
	21st to end	Day	12% 6% 2 5% 3 3 3 3 5% 9% 48%	8992
August	1st to 10th	Day	8% 5% 2 7% 4 5% 5% 4 6% 9% 45%	4511
	11th to 20th	Day	14% 5% 2 5% 4 4 4 3 5% 8% 45%	4226
	21st to end	Day	15% 7% 3 6% 4 4 4 3 4 6% 44%	4657
September	1st to 10th	Day	15% 6% 2 6% 5% 5% 4 3 6% 7% 40%	2340
	11th to 20th	Day	14% 7% 3 6% 4 4 3 4 5% 9% 41%	2200
	21st to end	Day	17% 9% 3 7% 4 5% 3 3 6% 7% 35%	2200
October	1st to 10th	Day	19% 7% 3 7% 5% 5% 4 4 5% 7% 34%	2150
	11th to 20th	Day	23% 11% 4 11% 7% 6% 4 4 5% 6% 20%	1913
	21st to end	Day	24% 11% 3 9% 6% 6% 6% 3 5% 5% 20%	1980
November	1st to 10th	Day	21% 14% 4 9% 7% 5% 5% 3 5% 6% 22%	1852
	11th to 20th	Day	16% 16% 4 13% 7% 5% 5% 4 7% 7% 18%	1776
	21st to end	Day	18% 20% 6% 13% 7% 6% 4 3 4 5% 14%	1612
December	1st to 10th	Day	15% 18% 5% 11% 7% 6% 7% 3 6% 5% 16%	2350
	11th to 20th	Day	17% 15% 6% 18% 9% 6% 4 3 5% 4 12%	2691
	21st to end	Day	25% 21% 6% 11% 5% 4 3 2 3 4 16%	3553
January	1st to 10th	Night	12% 15% 8% 16% 7% 5% 5% 4 4 5% 19%	8453
	11th to 20th	Night	8% 19% 8% 15% 9% 9% 5% 3 4 4 15%	8236
	21st to end	Night	7% 12% 7% 17% 9% 9% 8% 5% 6% 6% 15%	9058
February	1st to 10th	Night	9% 16% 6% 14% 9% 6% 5% 5% 6% 6% 18%	2815
	11th to 20th	Night	11% 14% 5% 13% 7% 7% 5% 4 6% 6% 22%	2564
	21st to end	Night	10% 15% 6% 13% 8% 5% 5% 4 6% 6% 23%	2076
March	1st to 10th	Night	16% 11% 3 8% 5% 4 4 3 5% 7% 33%	5482
	11th to 20th	Night	13% 12% 5% 9% 6% 5% 5% 4 5% 7% 29%	5136
	21st to end	Night	17% 12% 5% 10% 5% 4 4 3 4 6% 29%	5547
April	1st to 10th	Night	17% 12% 3 10% 4 4 4 3 6% 6% 30%	2100
	11th to 20th	Night	21% 9% 3 7% 4 3 3 3 5% 7% 36%	1888
	21st to end	Night	18% 9% 2 8% 5% 4 4 4 4 7% 35%	1890
May	1st to 10th	Night	13% 7% 2 7% 4 4 5% 4 5% 7% 43%	5257
	11th to 20th	Night	20% 7% 3 6% 4 4 3 3 4 5% 41%	4938
	21st to end	Night	12% 9% 3 7% 3 3 3 3 4 7% 45%	4555
June	1st to 10th	Night	13% 6% 2 6% 4 4 5% 4 7% 8% 40%	1470
	11th to 20th	Night	14% 6% 3 6% 5% 4 5% 4 6% 9% 39%	1470
	21st to end	Night	14% 6% 2 6% 6% 4 4 4 5% 8% 41%	1470
July	1st to 10th	Night	14% 5% 2 6% 4 5% 5% 4 7% 9% 39%	4110
	11th to 20th	Night	9% 5% 2 6% 4 4 4 3 6% 8% 48%	4667
	21st to end	Night	11% 5% 2 5% 4 4 4 3 6% 9% 48%	5118
August	1st to 10th	Night	11% 8% 3 7% 4 4 5% 4 6% 8% 40%	2860
	11th to 20th	Night	12% 5% 2 6% 4 4 4 4 5% 7% 47%	2911
	21st to end	Night	13% 5% 2 6% 4 3 4 3 5% 6% 50%	3238
September	1st to 10th	Night	12% 7% 3 6% 4 4 5% 3 5% 7% 45%	2040
	11th to 20th	Night	15% 6% 3 5% 4 4 5% 3 5% 8% 43%	2200
	21st to end	Night	19% 8% 2 7% 4 4 4 3 6% 6% 36%	2200
October	1st to 10th	Night	18% 8% 2 6% 3 4 4 4 6% 6% 36%	2250
	11th to 20th	Night	24% 11% 3 7% 4 5% 4 4 6% 6% 26%	2485
	21st to end	Night	24% 13% 3 8% 4 4 5% 4 5% 7% 24%	2860
November	1st to 10th	Night	20% 15% 4 7% 6% 4 4 3 5% 6% 26%	2666
	11th to 20th	Night	18% 16% 5% 12% 6% 5% 4 4 5% 6% 18%	2841
	21st to end	Night	19% 16% 7% 11% 5% 5% 5% 4 5% 6% 17%	3006
December	1st to 10th	Night	12% 18% 6% 13% 7% 6% 5% 4 6% 5% 17%	5060
	11th to 20th	Night	15% 17% 5% 14% 6% 6% 4 3 4 6% 20%	5736
	21st to end	Night	25% 22% 7% 13% 4 3 3 2 3 3 15%	7667

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	56% 23% 8% 7% 4 2	4455
	11th to 20th	Day	53% 23% 7% 12% 6%	4710
	21st to end	Day	52% 25% 6% 10% 7%	5156
February	1st to 10th	Day	25% 60% 5% 6% 3	1803
	11th to 20th	Day	26% 59% 5% 5% 5%	1951
	21st to end	Day	24% 60% 5% 7% 4	1730
March	1st to 10th	Day	38% 30% 10% 9% 10% 2	4580
	11th to 20th	Day	44% 28% 8% 11% 8% 1	5043
	21st to end	Day	48% 28% 5% 11% 8% 1	5669
April	1st to 10th	Day	23% 60% 4 8% 4 1	2520
	11th to 20th	Day	23% 59% 3 9% 6% 1	2681
	21st to end	Day	20% 59% 6% 9% 5% 1	2730
May	1st to 10th	Day	35% 24% 5% 20% 15% 2	7651
	11th to 20th	Day	35% 22% 6% 21% 13% 2	7928
	21st to end	Day	32% 23% 7% 19% 16% 4	9652
June	1st to 10th	Day	17% 59% 4 11% 7% 2	3150
	11th to 20th	Day	20% 60% 5% 10% 5% 1	3150
	21st to end	Day	18% 59% 5% 11% 6%	3150
July	1st to 10th	Day	31% 24% 12% 23% 10%	8806
	11th to 20th	Day	28% 23% 14% 30% 5%	8230
	21st to end	Day	26% 22% 12% 29% 11%	8794
August	1st to 10th	Day	22% 37% 9% 24% 8%	4496
	11th to 20th	Day	27% 36% 10% 21% 6%	4265
	21st to end	Day	27% 38% 11% 16% 7%	4656
September	1st to 10th	Day	20% 58% 7% 10% 5%	2340
	11th to 20th	Day	16% 58% 7% 16% 4	2200
	21st to end	Day	19% 58% 8% 11% 4	2200
October	1st to 10th	Day	21% 38% 10% 20% 11%	3501
	11th to 20th	Day	29% 37% 9% 23% 2	3090
	21st to end	Day	41% 38% 7% 10% 3	3180
November	1st to 10th	Day	31% 54% 5% 8% 2	1852
	11th to 20th	Day	30% 56% 6% 6% 3	1776
	21st to end	Day	36% 55% 3 3 3	1612
December	1st to 10th	Day	46% 39% 7% 6% 2	2350
	11th to 20th	Day	53% 33% 5% 5% 3	2691
	21st to end	Day	57% 26% 4 8% 5%	3553
January	1st to 10th	Night	52% 23% 7% 10% 6% 2	8453
	11th to 20th	Night	59% 21% 6% 8% 5%	8280
	21st to end	Night	53% 25% 7% 9% 5% 1	9058
February	1st to 10th	Night	26% 60% 5% 6% 3	2815
	11th to 20th	Night	24% 58% 5% 9% 3	2566
	21st to end	Night	25% 59% 5% 7% 4	2076
March	1st to 10th	Night	37% 29% 12% 12% 8% 2	5493
	11th to 20th	Night	41% 28% 12% 12% 6% 1	5137
	21st to end	Night	45% 28% 5% 11% 10% 1	5547
April	1st to 10th	Night	25% 59% 3 8% 5%	2100
	11th to 20th	Night	21% 59% 3 9% 6% 1	1888
	21st to end	Night	21% 59% 4 8% 6% 1	1890
May	1st to 10th	Night	32% 24% 6% 23% 13% 3	5264
	11th to 20th	Night	36% 23% 4 24% 11% 1	4939
	21st to end	Night	33% 22% 7% 21% 12% 5%	4556
June	1st to 10th	Night	17% 59% 4 9% 10% 1	1470
	11th to 20th	Night	21% 60% 4 10% 4 1	1470
	21st to end	Night	16% 59% 5% 12% 6% 1	1470
July	1st to 10th	Night	32% 25% 12% 17% 13% 1	4075
	11th to 20th	Night	25% 22% 13% 32% 7%	4620
	21st to end	Night	24% 24% 12% 29% 11%	5002
August	1st to 10th	Night	28% 37% 7% 19% 9%	2851
	11th to 20th	Night	26% 39% 9% 19% 7%	2938
	21st to end	Night	22% 37% 8% 24% 8%	3238
September	1st to 10th	Night	18% 58% 8% 11% 5%	2040
	11th to 20th	Night	15% 58% 7% 15% 4 1	2200
	21st to end	Night	20% 58% 7% 11% 5%	2200
October	1st to 10th	Night	23% 39% 9% 23% 6%	3679
	11th to 20th	Night	24% 38% 11% 22% 5%	4047
	21st to end	Night	36% 41% 12% 8% 2	4610
November	1st to 10th	Night	30% 54% 6% 7% 3	2666
	11th to 20th	Night	29% 56% 6% 7% 3	2841
	21st to end	Night	33% 56% 5% 3 2	3006
December	1st to 10th	Night	44% 38% 10% 7% 1	5060
	11th to 20th	Night	44% 34% 8% 8% 5% 1	5735
	21st to end	Night	58% 26% 4 9% 4	7667

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% 19% 34% 16% 8% 1	286
	11th to 20th	Day	19% 17% 35% 22% 6% 1	330
	21st to end	Day	19% 18% 32% 26% 5%	363
February	1st to 10th	Day	22% 24% 34% 15% 4 1	330
	11th to 20th	Day	22% 30% 34% 10% 4	330
	21st to end	Day	23% 30% 32% 12% 3	273
March	1st to 10th	Day	21% 28% 35% 13% 3	330
	11th to 20th	Day	25% 21% 28% 19% 5% 2	519
	21st to end	Day	27% 19% 28% 18% 7% 1	594
April	1st to 10th	Day	25% 19% 31% 19% 5% 1	540
	11th to 20th	Day	27% 20% 26% 15% 11% 1	532
	21st to end	Day	25% 19% 27% 18% 8% 3	540
May	1st to 10th	Day	22% 20% 28% 17% 8% 4	543
	11th to 20th	Day	22% 17% 34% 16% 8% 2	670
	21st to end	Day	18% 18% 35% 20% 6% 2	844
June	1st to 10th	Day	18% 17% 36% 19% 8% 1	780
	11th to 20th	Day	17% 18% 36% 20% 6% 2	780
	21st to end	Day	21% 14% 33% 23% 7% 3	780
July	1st to 10th	Day	11% 13% 39% 24% 10% 2	771
	11th to 20th	Day	13% 13% 37% 22% 11% 3	768
	21st to end	Day	14% 13% 34% 25% 11% 3	849
August	1st to 10th	Day	12% 12% 28% 30% 14% 4	662
	11th to 20th	Day	18% 8% 20% 30% 16% 9%	535
	21st to end	Day	19% 11% 27% 22% 15% 5%	583
September	1st to 10th	Day	21% 13% 24% 22% 16% 4	530
	11th to 20th	Day	18% 10% 26% 28% 15% 3	530
	21st to end	Day	22% 14% 23% 27% 11% 2	530
October	1st to 10th	Day	22% 19% 25% 23% 10% 1	530
	11th to 20th	Day	26% 19% 34% 17% 3	443
	21st to end	Day	33% 21% 29% 14% 3	363
November	1st to 10th	Day	30% 22% 32% 12% 3	330
	11th to 20th	Day	29% 25% 30% 11% 5%	269
	21st to end	Day	27% 24% 36% 11% 2	220
December	1st to 10th	Day	25% 18% 31% 16% 8% 1	220
	11th to 20th	Day	30% 23% 32% 11% 4	220
	21st to end	Day	33% 24% 27% 10% 7%	242
January	1st to 10th	Night	23% 16% 31% 25% 5%	1050
	11th to 20th	Night	20% 15% 33% 23% 8% 1	1050
	21st to end	Night	19% 12% 33% 27% 8% 1	1155
February	1st to 10th	Night	18% 17% 33% 27% 4 1	925
	11th to 20th	Night	18% 18% 31% 26% 7%	823
	21st to end	Night	17% 18% 35% 25% 5%	692
March	1st to 10th	Night	18% 14% 36% 24% 7% 1	840
	11th to 20th	Night	22% 15% 32% 23% 7%	840
	21st to end	Night	19% 12% 35% 27% 6% 1	908
April	1st to 10th	Night	24% 12% 28% 28% 6% 1	630
	11th to 20th	Night	26% 11% 25% 27% 10% 1	623
	21st to end	Night	22% 9% 27% 31% 10%	630
May	1st to 10th	Night	17% 9% 26% 37% 9% 1	630
	11th to 20th	Night	20% 9% 27% 31% 11% 1	621
	21st to end	Night	14% 10% 30% 36% 9%	480
June	1st to 10th	Night	15% 9% 30% 37% 9%	420
	11th to 20th	Night	18% 9% 27% 35% 12%	420
	21st to end	Night	17% 6% 26% 34% 15% 1	420
July	1st to 10th	Night	12% 4 25% 44% 13%	410
	11th to 20th	Night	13% 6% 20% 40% 19% 2	596
	21st to end	Night	14% 5% 21% 39% 19% 2	690
August	1st to 10th	Night	14% 4 22% 36% 22% 1	627
	11th to 20th	Night	10% 4 18% 37% 27% 3	606
	21st to end	Night	18% 7% 20% 33% 22% 1	660
September	1st to 10th	Night	17% 7% 25% 29% 18% 4	640
	11th to 20th	Night	17% 7% 25% 32% 17% 3	800
	21st to end	Night	22% 10% 21% 31% 13% 3	800
October	1st to 10th	Night	24% 12% 24% 27% 13% 1	800
	11th to 20th	Night	30% 14% 25% 25% 6%	800
	21st to end	Night	31% 11% 26% 27% 5%	880
November	1st to 10th	Night	30% 13% 29% 22% 6%	820
	11th to 20th	Night	26% 16% 32% 21% 5%	840
	21st to end	Night	26% 18% 31% 21% 4	906
December	1st to 10th	Night	24% 17% 30% 22% 6%	1050
	11th to 20th	Night	26% 18% 30% 19% 5% 1	1050
	21st to end	Night	31% 13% 30% 19% 7%	1155

Page generated at 2026-08-12 03:37:19. Version ac07

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