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 2025-04-11.

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	15% 10% 4 9% 5% 5% 4 4 5% 7% 33%	112852
	Night	15% 12% 5% 10% 6% 5% 4 3 5% 6% 28%	115591
Transparency	Day	31% 42% 7% 13% 7% 1	116360
	Night	35% 41% 7% 11% 6% 1	120246
Seeing	Day	21% 17% 31% 21% 9% 2	16030
	Night	21% 12% 28% 28% 10% 1	25646

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	9% 17% 6% 16% 7% 6% 4 4 5% 5% 20%	3434
	11th to 20th	Day	12% 13% 6% 12% 8% 8% 7% 4 6% 6% 19%	3589
	21st to end	Day	9% 19% 9% 16% 8% 7% 6% 4 4 5% 14%	3982
February	1st to 10th	Day	9% 13% 6% 14% 11% 6% 5% 3 7% 6% 19%	1717
	11th to 20th	Day	12% 13% 5% 11% 8% 8% 5% 4 4 6% 24%	1847
	21st to end	Day	10% 13% 6% 14% 7% 5% 4 4 6% 7% 25%	1650
March	1st to 10th	Day	14% 12% 4 9% 5% 5% 5% 4 5% 7% 31%	4478
	11th to 20th	Day	14% 14% 4 9% 6% 5% 4 4 6% 7% 28%	4934
	21st to end	Day	19% 12% 7% 10% 5% 5% 4 3 4 5% 26%	5546
April	1st to 10th	Day	16% 12% 4 8% 5% 4 5% 3 5% 6% 31%	2400
	11th to 20th	Day	20% 11% 4 7% 3 5% 4 3 5% 5% 35%	2423
	21st to end	Day	18% 10% 3 6% 4 4 4 5% 5% 7% 34%	2470
May	1st to 10th	Day	17% 8% 3 7% 5% 4 4 3 4 6% 38%	4108
	11th to 20th	Day	13% 7% 2 6% 4 4 4 3 5% 8% 43%	4239
	21st to end	Day	17% 6% 2 5% 3 4 4 4 6% 7% 42%	5148
June	1st to 10th	Day	15% 7% 2 6% 4 4 5% 4 6% 8% 39%	2850
	11th to 20th	Day	13% 6% 2 7% 5% 5% 5% 4 7% 8% 38%	2850
	21st to end	Day	15% 8% 2 6% 4 4 4 4 6% 7% 40%	2850
July	1st to 10th	Day	16% 8% 2 6% 4 4 4 3 5% 8% 40%	4760
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 7% 10% 44%	4452
	21st to end	Day	12% 5% 2 5% 3 3 3 3 5% 9% 49%	4814
August	1st to 10th	Day	9% 6% 2 7% 4 5% 5% 4 6% 9% 44%	4242
	11th to 20th	Day	14% 5% 2 5% 4 4 4 3 5% 8% 46%	4044
	21st to end	Day	16% 7% 3 6% 4 3 4 3 4 6% 44%	4514
September	1st to 10th	Day	15% 6% 2 6% 5% 5% 4 3 6% 6% 41%	2223
	11th to 20th	Day	14% 7% 3 6% 4 4 3 4 5% 9% 40%	2090
	21st to end	Day	17% 9% 3 7% 4 5% 3 3 6% 7% 35%	2090
October	1st to 10th	Day	19% 8% 3 7% 5% 5% 4 4 5% 7% 34%	2043
	11th to 20th	Day	23% 12% 4 10% 7% 6% 4 4 5% 6% 20%	1818
	21st to end	Day	25% 11% 3 10% 7% 6% 6% 3 5% 5% 19%	1881
November	1st to 10th	Day	22% 14% 4 8% 7% 5% 5% 3 4 6% 22%	1762
	11th to 20th	Day	16% 16% 4 12% 7% 5% 5% 4 7% 7% 18%	1692
	21st to end	Day	18% 20% 6% 12% 7% 6% 4 3 4 5% 15%	1535
December	1st to 10th	Day	15% 18% 6% 11% 7% 6% 7% 3 6% 5% 16%	2280
	11th to 20th	Day	17% 16% 6% 18% 9% 6% 5% 3 5% 4 12%	2621
	21st to end	Day	25% 21% 6% 11% 5% 3 3 2 3 4 16%	3476
January	1st to 10th	Night	12% 15% 6% 14% 7% 5% 5% 4 5% 5% 22%	6514
	11th to 20th	Night	9% 17% 6% 14% 10% 8% 5% 3 5% 5% 17%	6316
	21st to end	Night	9% 15% 8% 19% 9% 8% 6% 4 4 4 13%	6996
February	1st to 10th	Night	9% 16% 6% 14% 10% 6% 5% 5% 6% 6% 17%	2681
	11th to 20th	Night	11% 14% 5% 12% 7% 7% 5% 4 6% 6% 22%	2439
	21st to end	Night	11% 15% 5% 12% 8% 5% 5% 4 6% 6% 24%	1980
March	1st to 10th	Night	16% 11% 3 7% 5% 4 4 3 5% 7% 33%	5362
	11th to 20th	Night	13% 12% 5% 9% 5% 5% 5% 4 5% 7% 30%	5025
	21st to end	Night	18% 12% 5% 10% 5% 4 4 3 4 6% 29%	5427
April	1st to 10th	Night	17% 12% 3 10% 4 4 4 4 6% 6% 31%	2000
	11th to 20th	Night	20% 9% 3 7% 4 4 4 3 5% 7% 36%	1712
	21st to end	Night	17% 9% 2 8% 5% 4 4 4 4 6% 36%	1710
May	1st to 10th	Night	18% 8% 3 7% 4 4 4 3 5% 6% 38%	2833
	11th to 20th	Night	13% 8% 3 8% 5% 5% 5% 4 6% 6% 37%	2646
	21st to end	Night	16% 9% 3 7% 3 4 4 3 5% 7% 40%	2437
June	1st to 10th	Night	12% 6% 2 7% 4 5% 5% 4 7% 8% 40%	1330
	11th to 20th	Night	14% 7% 3 5% 5% 4 5% 4 6% 9% 40%	1330
	21st to end	Night	15% 6% 2 6% 6% 4 4 4 5% 7% 41%	1330
July	1st to 10th	Night	16% 5% 2 5% 4 5% 5% 4 7% 8% 38%	2210
	11th to 20th	Night	9% 6% 3 6% 4 4 4 3 6% 7% 49%	2515
	21st to end	Night	12% 5% 2 4 4 4 5% 3 5% 8% 48%	2750
August	1st to 10th	Night	10% 8% 3 7% 4 4 5% 4 6% 8% 40%	2689
	11th to 20th	Night	12% 5% 2 6% 4 4 4 4 5% 7% 47%	2785
	21st to end	Night	12% 6% 2 6% 4 3 4 3 5% 6% 50%	3139
September	1st to 10th	Night	13% 6% 3 6% 4 4 5% 3 5% 7% 45%	1938
	11th to 20th	Night	15% 5% 2 5% 4 4 5% 3 5% 8% 43%	2090
	21st to end	Night	18% 8% 2 7% 4 4 4 3 6% 7% 36%	2090
October	1st to 10th	Night	19% 9% 2 7% 3 4 4 4 6% 6% 35%	2137
	11th to 20th	Night	23% 11% 3 7% 4 5% 5% 4 5% 6% 27%	2361
	21st to end	Night	25% 14% 3 8% 4 4 5% 4 5% 7% 22%	2717
November	1st to 10th	Night	20% 15% 4 7% 6% 4 4 3 4 6% 27%	2536
	11th to 20th	Night	19% 16% 5% 11% 6% 5% 4 4 5% 6% 18%	2705
	21st to end	Night	19% 16% 7% 10% 5% 5% 5% 4 5% 6% 17%	2863
December	1st to 10th	Night	12% 18% 6% 12% 7% 6% 6% 4 6% 6% 18%	4910
	11th to 20th	Night	15% 17% 5% 14% 6% 6% 4 3 4 6% 20%	5586
	21st to end	Night	25% 22% 7% 12% 4 3 3 2 3 3 15%	7502

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	46% 28% 9% 9% 5% 3	3435
	11th to 20th	Day	47% 28% 8% 11% 6%	3620
	21st to end	Day	53% 30% 6% 6% 6%	3982
February	1st to 10th	Day	24% 63% 5% 5% 2	1717
	11th to 20th	Day	24% 61% 5% 5% 5%	1856
	21st to end	Day	23% 62% 4 7% 4	1650
March	1st to 10th	Day	38% 30% 10% 9% 10% 2	4480
	11th to 20th	Day	44% 29% 8% 11% 7% 1	4934
	21st to end	Day	47% 29% 5% 11% 8% 1	5546
April	1st to 10th	Day	22% 62% 4 7% 4	2400
	11th to 20th	Day	20% 65% 2 8% 5% 1	2423
	21st to end	Day	17% 65% 4 8% 5% 1	2470
May	1st to 10th	Day	31% 39% 3 16% 10% 1	4120
	11th to 20th	Day	25% 38% 7% 20% 10%	4243
	21st to end	Day	27% 39% 6% 13% 12% 3	5148
June	1st to 10th	Day	15% 65% 3 10% 6% 1	2850
	11th to 20th	Day	17% 65% 4 8% 5% 1	2850
	21st to end	Day	15% 64% 5% 10% 6%	2850
July	1st to 10th	Day	31% 37% 9% 14% 8% 1	4686
	11th to 20th	Day	21% 39% 11% 23% 5%	4376
	21st to end	Day	18% 37% 7% 23% 14%	4662
August	1st to 10th	Day	21% 39% 8% 23% 8%	4227
	11th to 20th	Day	26% 38% 9% 20% 6%	4083
	21st to end	Day	27% 39% 10% 16% 7%	4513
September	1st to 10th	Day	18% 60% 6% 10% 5%	2223
	11th to 20th	Day	15% 60% 6% 15% 4	2090
	21st to end	Day	17% 61% 8% 10% 4	2090
October	1st to 10th	Day	20% 39% 10% 20% 11%	3394
	11th to 20th	Day	28% 38% 9% 23% 2	2995
	21st to end	Day	42% 39% 7% 9% 3	3081
November	1st to 10th	Day	30% 57% 5% 8% 2	1762
	11th to 20th	Day	28% 58% 5% 6% 2	1692
	21st to end	Day	33% 58% 3 3 3	1535
December	1st to 10th	Day	46% 40% 7% 6% 2	2280
	11th to 20th	Day	53% 34% 5% 5% 3	2621
	21st to end	Day	56% 27% 4 8% 5%	3476
January	1st to 10th	Night	45% 29% 7% 9% 6% 3	6514
	11th to 20th	Night	52% 27% 7% 10% 4	6360
	21st to end	Night	54% 30% 6% 5% 4 1	6996
February	1st to 10th	Night	25% 63% 5% 6% 2	2681
	11th to 20th	Night	23% 61% 5% 8% 3	2441
	21st to end	Night	23% 62% 5% 6% 4	1980
March	1st to 10th	Night	37% 30% 11% 12% 8% 2	5373
	11th to 20th	Night	41% 29% 12% 12% 6% 1	5026
	21st to end	Night	45% 28% 5% 11% 10% 1	5427
April	1st to 10th	Night	23% 62% 3 8% 5%	2000
	11th to 20th	Night	18% 65% 3 8% 5% 1	1712
	21st to end	Night	18% 65% 3 7% 5% 1	1710
May	1st to 10th	Night	32% 39% 4 16% 8% 1	2840
	11th to 20th	Night	30% 39% 4 20% 7%	2647
	21st to end	Night	31% 39% 7% 11% 8% 4	2438
June	1st to 10th	Night	15% 65% 4 8% 7% 1	1330
	11th to 20th	Night	18% 65% 3 7% 5% 1	1330
	21st to end	Night	15% 64% 3 11% 6% 1	1330
July	1st to 10th	Night	30% 38% 9% 15% 8%	2175
	11th to 20th	Night	20% 37% 11% 23% 8%	2468
	21st to end	Night	20% 37% 7% 19% 16% 1	2662
August	1st to 10th	Night	27% 39% 6% 19% 8%	2680
	11th to 20th	Night	25% 40% 8% 19% 7%	2812
	21st to end	Night	22% 38% 7% 24% 8%	3139
September	1st to 10th	Night	16% 61% 7% 10% 6%	1938
	11th to 20th	Night	14% 60% 7% 14% 4 1	2090
	21st to end	Night	19% 60% 7% 10% 4	2090
October	1st to 10th	Night	23% 40% 8% 22% 6%	3566
	11th to 20th	Night	23% 39% 11% 22% 5%	3923
	21st to end	Night	36% 42% 12% 7% 2	4467
November	1st to 10th	Night	29% 56% 6% 7% 3	2536
	11th to 20th	Night	28% 58% 5% 7% 2	2705
	21st to end	Night	31% 59% 5% 3 2	2863
December	1st to 10th	Night	43% 39% 10% 6% 1	4910
	11th to 20th	Night	44% 34% 8% 7% 5% 1	5585
	21st to end	Night	58% 26% 4 9% 4	7502

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	20% 18% 35% 17% 9% 1	260
	11th to 20th	Day	19% 16% 35% 23% 6% 1	300
	21st to end	Day	20% 18% 31% 25% 5%	330
February	1st to 10th	Day	21% 24% 35% 16% 4 1	300
	11th to 20th	Day	22% 29% 35% 10% 3	300
	21st to end	Day	24% 31% 32% 11% 3	249
March	1st to 10th	Day	21% 28% 35% 13% 3	300
	11th to 20th	Day	24% 20% 28% 20% 5% 2	480
	21st to end	Day	26% 18% 29% 19% 8% 1	550
April	1st to 10th	Day	24% 19% 31% 20% 5% 1	500
	11th to 20th	Day	27% 20% 24% 17% 12% 1	452
	21st to end	Day	26% 18% 27% 18% 9% 3	460
May	1st to 10th	Day	24% 20% 27% 17% 8% 5%	463
	11th to 20th	Day	20% 17% 35% 17% 9% 3	580
	21st to end	Day	18% 17% 34% 22% 7% 2	734
June	1st to 10th	Day	19% 18% 36% 18% 8% 1	680
	11th to 20th	Day	17% 18% 35% 22% 7% 2	680
	21st to end	Day	21% 12% 33% 25% 7% 3	680
July	1st to 10th	Day	11% 13% 37% 25% 11% 3	671
	11th to 20th	Day	12% 11% 36% 24% 12% 4	668
	21st to end	Day	13% 12% 33% 26% 12% 4	739
August	1st to 10th	Day	13% 12% 26% 30% 14% 4	573
	11th to 20th	Day	17% 8% 17% 31% 17% 10%	479
	21st to end	Day	19% 12% 26% 23% 15% 5%	539
September	1st to 10th	Day	20% 12% 24% 23% 16% 4	490
	11th to 20th	Day	19% 10% 26% 28% 14% 3	490
	21st to end	Day	22% 14% 23% 27% 12% 2	490
October	1st to 10th	Day	22% 20% 23% 23% 10% 1	490
	11th to 20th	Day	26% 18% 34% 17% 3	408
	21st to end	Day	35% 23% 28% 12% 2	330
November	1st to 10th	Day	29% 23% 33% 12% 3	300
	11th to 20th	Day	28% 24% 32% 11% 5%	245
	21st to end	Day	26% 24% 37% 12% 2	200
December	1st to 10th	Day	25% 16% 33% 16% 9% 2	200
	11th to 20th	Day	29% 22% 34% 12% 4 1	200
	21st to end	Day	32% 24% 27% 10% 7%	220
January	1st to 10th	Night	23% 16% 31% 26% 6%	1000
	11th to 20th	Night	21% 14% 32% 23% 9% 1	1000
	21st to end	Night	20% 12% 32% 27% 8% 1	1100
February	1st to 10th	Night	18% 16% 33% 27% 4 1	881
	11th to 20th	Night	19% 18% 31% 25% 7%	783
	21st to end	Night	17% 18% 35% 25% 5%	660
March	1st to 10th	Night	18% 14% 35% 25% 8% 1	800
	11th to 20th	Night	21% 16% 33% 23% 8% 1	800
	21st to end	Night	19% 12% 34% 28% 6% 1	865
April	1st to 10th	Night	24% 12% 28% 29% 6% 1	600
	11th to 20th	Night	25% 10% 27% 28% 10% 1	565
	21st to end	Night	21% 9% 28% 30% 11% 1	570
May	1st to 10th	Night	18% 9% 26% 36% 9% 1	570
	11th to 20th	Night	19% 8% 27% 32% 12% 1	561
	21st to end	Night	15% 9% 28% 38% 10%	434
June	1st to 10th	Night	14% 9% 30% 38% 9%	380
	11th to 20th	Night	18% 9% 25% 35% 12%	380
	21st to end	Night	18% 6% 24% 35% 16% 1	380
July	1st to 10th	Night	12% 4 25% 44% 14%	370
	11th to 20th	Night	13% 6% 17% 41% 21% 2	538
	21st to end	Night	15% 5% 19% 39% 20% 2	624
August	1st to 10th	Night	14% 4 23% 35% 23% 1	567
	11th to 20th	Night	10% 4 17% 37% 28% 4	564
	21st to end	Night	18% 7% 20% 33% 22% 1	627
September	1st to 10th	Night	17% 6% 25% 30% 17% 4	608
	11th to 20th	Night	18% 7% 25% 32% 15% 3	760
	21st to end	Night	23% 10% 20% 31% 13% 3	760
October	1st to 10th	Night	24% 12% 24% 26% 13% 1	760
	11th to 20th	Night	30% 14% 24% 26% 6%	760
	21st to end	Night	32% 12% 26% 26% 4	836
November	1st to 10th	Night	30% 13% 29% 21% 7% 1	780
	11th to 20th	Night	26% 15% 32% 22% 5%	800
	21st to end	Night	26% 17% 31% 21% 4	863
December	1st to 10th	Night	24% 16% 30% 22% 7%	1000
	11th to 20th	Night	26% 18% 30% 19% 5% 1	1000
	21st to end	Night	31% 12% 30% 20% 7%	1100

Page generated at 2025-04-08 09:17:24. Version ac07

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