Lac St-Joseph
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac St-Joseph clear sky chart from 2005-11-06 to 2026-08-30.

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% 10% 3 8% 5% 4 5% 4 5% 6% 30%	143730
	Night	18% 12% 4 9% 5% 4 4 3 5% 5% 29%	138516
Transparency	Day	53% 7% 12% 17% 9% 1	147174
	Night	55% 6% 12% 17% 9% 1	143162
Seeing	Day	26% 18% 29% 19% 7% 1	17472
	Night	24% 13% 27% 27% 8% 1	25932

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	16% 16% 5% 12% 6% 4 4 3 4 5% 24%	4661
	11th to 20th	Day	11% 17% 7% 19% 8% 6% 4 2 3 4 18%	4650
	21st to end	Day	6% 13% 6% 12% 6% 5% 5% 5% 7% 7% 30%	5124
February	1st to 10th	Day	10% 15% 5% 13% 7% 6% 5% 4 4 4 27%	1683
	11th to 20th	Day	13% 17% 6% 11% 5% 5% 4 3 5% 5% 25%	2025
	21st to end	Day	12% 16% 5% 12% 6% 4 4 4 4 6% 26%	1730
March	1st to 10th	Day	23% 15% 5% 10% 5% 4 4 2 4 3 25%	4576
	11th to 20th	Day	16% 17% 4 9% 5% 4 4 3 4 6% 28%	4824
	21st to end	Day	19% 15% 3 8% 4 4 4 3 3 4 33%	5996
April	1st to 10th	Day	23% 13% 3 8% 6% 4 4 2 4 4 29%	2520
	11th to 20th	Day	23% 9% 3 7% 5% 4 4 3 4 5% 34%	2581
	21st to end	Day	23% 10% 3 8% 5% 5% 4 3 4 6% 30%	2730
May	1st to 10th	Day	28% 9% 3 6% 4 4 4 3 5% 6% 27%	7895
	11th to 20th	Day	22% 7% 2 7% 4 4 5% 4 5% 7% 32%	8221
	21st to end	Day	22% 9% 3 7% 5% 5% 5% 4 5% 6% 28%	9060
June	1st to 10th	Day	21% 7% 3 7% 6% 6% 6% 5% 6% 8% 26%	3145
	11th to 20th	Day	20% 8% 2 7% 5% 5% 5% 4 6% 7% 33%	3150
	21st to end	Day	25% 9% 3 7% 6% 5% 5% 4 5% 6% 25%	3150
July	1st to 10th	Day	18% 7% 3 7% 4 5% 5% 4 7% 8% 32%	8285
	11th to 20th	Day	17% 6% 2 7% 4 5% 5% 4 8% 8% 34%	8280
	21st to end	Day	14% 5% 2 6% 5% 6% 5% 4 6% 9% 36%	8993
August	1st to 10th	Day	17% 6% 3 7% 5% 5% 6% 4 8% 9% 30%	4703
	11th to 20th	Day	22% 6% 3 6% 5% 5% 5% 5% 6% 8% 29%	4313
	21st to end	Day	23% 7% 3 6% 4 4 4 4 5% 7% 34%	4556
September	1st to 10th	Day	20% 7% 3 5% 4 4 5% 4 6% 8% 36%	2400
	11th to 20th	Day	19% 5% 2 5% 3 4 3 3 5% 6% 45%	2236
	21st to end	Day	24% 7% 3 6% 4 3 3 3 5% 6% 37%	2200
October	1st to 10th	Day	22% 8% 3 6% 4 5% 5% 3 5% 6% 34%	2175
	11th to 20th	Day	26% 9% 4 8% 5% 5% 5% 4 5% 6% 24%	1844
	21st to end	Day	29% 10% 3 9% 5% 4 4 3 4 6% 25%	1980
November	1st to 10th	Day	22% 12% 3 8% 5% 4 4 3 4 5% 29%	1851
	11th to 20th	Day	21% 15% 6% 10% 5% 4 4 3 4 5% 25%	1869
	21st to end	Day	20% 19% 5% 9% 6% 5% 4 4 3 5% 19%	1536
December	1st to 10th	Day	20% 16% 6% 11% 5% 5% 4 4 5% 5% 20%	2350
	11th to 20th	Day	21% 15% 6% 10% 5% 4 3 2 3 4 27%	2688
	21st to end	Day	20% 18% 5% 8% 4 4 5% 3 4 5% 26%	3750
January	1st to 10th	Night	14% 19% 7% 14% 6% 5% 4 3 4 4 21%	8234
	11th to 20th	Night	11% 23% 9% 16% 6% 4 4 2 3 4 17%	8235
	21st to end	Night	6% 12% 6% 14% 8% 7% 5% 4 6% 7% 26%	9057
February	1st to 10th	Night	11% 14% 5% 12% 8% 5% 4 4 4 5% 29%	2935
	11th to 20th	Night	13% 17% 5% 12% 6% 5% 4 3 4 5% 27%	2479
	21st to end	Night	14% 15% 5% 9% 6% 4 5% 3 4 6% 29%	2076
March	1st to 10th	Night	22% 13% 4 11% 5% 4 5% 3 4 5% 24%	5484
	11th to 20th	Night	16% 15% 3 9% 6% 6% 6% 4 5% 7% 23%	5354
	21st to end	Night	19% 15% 4 8% 4 4 4 3 4 5% 30%	5176
April	1st to 10th	Night	22% 14% 3 6% 5% 4 4 3 5% 6% 29%	2100
	11th to 20th	Night	21% 10% 3 7% 5% 4 5% 4 5% 6% 32%	1988
	21st to end	Night	22% 11% 3 7% 4 4 3 3 4 7% 33%	1890
May	1st to 10th	Night	27% 8% 3 6% 4 4 4 4 5% 5% 30%	5047
	11th to 20th	Night	25% 6% 3 7% 4 4 4 3 5% 6% 33%	4639
	21st to end	Night	21% 8% 3 7% 4 4 5% 3 5% 6% 33%	5114
June	1st to 10th	Night	22% 7% 2 7% 4 4 6% 4 5% 7% 31%	1470
	11th to 20th	Night	21% 6% 3 5% 4 4 4 5% 6% 6% 35%	1470
	21st to end	Night	23% 7% 3 7% 5% 4 4 4 5% 7% 31%	1470
July	1st to 10th	Night	18% 7% 2 7% 4 4 6% 4 6% 7% 35%	4657
	11th to 20th	Night	19% 7% 2 6% 4 4 4 3 6% 7% 38%	4680
	21st to end	Night	15% 6% 2 7% 4 4 5% 3 5% 7% 41%	5084
August	1st to 10th	Night	19% 8% 2 7% 4 4 4 3 6% 6% 36%	2666
	11th to 20th	Night	21% 6% 2 7% 4 5% 4 4 5% 7% 33%	2921
	21st to end	Night	21% 8% 3 8% 4 4 4 3 4 6% 34%	3536
September	1st to 10th	Night	19% 7% 2 5% 4 3 3 3 5% 6% 43%	2000
	11th to 20th	Night	18% 5% 2 6% 4 3 3 4 4 5% 45%	2163
	21st to end	Night	22% 7% 2 5% 4 4 4 2 4 5% 41%	2200
October	1st to 10th	Night	20% 8% 2 5% 4 4 4 3 5% 6% 39%	2222
	11th to 20th	Night	24% 9% 3 6% 5% 4 4 4 4 5% 32%	2555
	21st to end	Night	27% 10% 3 6% 4 4 4 3 5% 6% 28%	2860
November	1st to 10th	Night	21% 13% 4 7% 5% 4 4 2 5% 6% 30%	2667
	11th to 20th	Night	21% 12% 5% 7% 4 4 4 3 4 6% 30%	2750
	21st to end	Night	23% 17% 5% 9% 5% 4 4 3 4 5% 23%	3081
December	1st to 10th	Night	17% 16% 7% 12% 9% 5% 4 3 4 5% 20%	5060
	11th to 20th	Night	23% 16% 5% 10% 6% 4 4 3 4 4 22%	5741
	21st to end	Night	21% 18% 5% 9% 4 3 3 2 3 3 27%	7455

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	60% 6% 9% 16% 10%	4662
	11th to 20th	Day	70% 6% 6% 11% 6% 1	4680
	21st to end	Day	49% 6% 9% 20% 15%	5124
February	1st to 10th	Day	59% 6% 8% 16% 9% 2	1683
	11th to 20th	Day	60% 6% 10% 13% 9% 1	2034
	21st to end	Day	58% 5% 9% 16% 9% 3	1730
March	1st to 10th	Day	63% 7% 7% 11% 10% 4	4579
	11th to 20th	Day	55% 8% 13% 13% 10% 1	4824
	21st to end	Day	55% 5% 6% 16% 15% 4	5996
April	1st to 10th	Day	59% 6% 10% 12% 9% 3	2520
	11th to 20th	Day	51% 7% 10% 20% 10% 3	2581
	21st to end	Day	56% 6% 10% 15% 12% 2	2730
May	1st to 10th	Day	56% 6% 10% 16% 11% 1	7907
	11th to 20th	Day	49% 9% 15% 19% 6% 2	8225
	21st to end	Day	53% 9% 9% 16% 11% 2	9061
June	1st to 10th	Day	53% 9% 11% 18% 7% 1	3145
	11th to 20th	Day	48% 8% 15% 17% 10% 1	3150
	21st to end	Day	57% 7% 12% 15% 8% 1	3150
July	1st to 10th	Day	47% 7% 15% 21% 10%	8215
	11th to 20th	Day	44% 8% 17% 23% 7%	8205
	21st to end	Day	43% 9% 19% 23% 6%	8795
August	1st to 10th	Day	47% 10% 19% 18% 6%	4689
	11th to 20th	Day	50% 11% 18% 17% 4	4352
	21st to end	Day	48% 9% 14% 17% 13%	4556
September	1st to 10th	Day	44% 9% 16% 21% 9%	2400
	11th to 20th	Day	39% 7% 16% 27% 10%	2236
	21st to end	Day	48% 8% 12% 23% 9%	2200
October	1st to 10th	Day	55% 8% 11% 21% 6%	3539
	11th to 20th	Day	56% 8% 16% 19% 2	2982
	21st to end	Day	56% 8% 16% 14% 6%	3180
November	1st to 10th	Day	57% 8% 11% 18% 7%	1851
	11th to 20th	Day	62% 6% 8% 16% 7% 1	1869
	21st to end	Day	67% 6% 12% 10% 5% 1	1536
December	1st to 10th	Day	65% 6% 11% 12% 6%	2350
	11th to 20th	Day	62% 4 7% 16% 10%	2688
	21st to end	Day	61% 5% 9% 13% 11% 1	3750
January	1st to 10th	Night	66% 5% 9% 13% 7%	8234
	11th to 20th	Night	71% 5% 8% 12% 4	8280
	21st to end	Night	54% 7% 9% 16% 13%	9057
February	1st to 10th	Night	57% 5% 9% 19% 10% 1	2935
	11th to 20th	Night	60% 5% 10% 14% 10% 1	2481
	21st to end	Night	57% 5% 8% 16% 13% 2	2076
March	1st to 10th	Night	63% 5% 10% 10% 11% 1	5494
	11th to 20th	Night	59% 7% 13% 12% 8% 1	5355
	21st to end	Night	56% 5% 6% 21% 10% 2	5176
April	1st to 10th	Night	56% 6% 8% 15% 13% 2	2100
	11th to 20th	Night	50% 7% 9% 20% 11% 2	1988
	21st to end	Night	52% 6% 10% 17% 13% 2	1890
May	1st to 10th	Night	53% 6% 11% 18% 11% 1	5053
	11th to 20th	Night	49% 8% 13% 19% 9% 1	4640
	21st to end	Night	49% 7% 10% 16% 15% 2	5115
June	1st to 10th	Night	50% 7% 13% 20% 9% 1	1470
	11th to 20th	Night	46% 8% 15% 19% 11% 2	1470
	21st to end	Night	52% 7% 14% 17% 10%	1470
July	1st to 10th	Night	46% 8% 17% 19% 10%	4617
	11th to 20th	Night	45% 7% 19% 24% 6%	4632
	21st to end	Night	42% 7% 20% 25% 7%	4967
August	1st to 10th	Night	46% 7% 17% 22% 7%	2656
	11th to 20th	Night	49% 10% 19% 17% 5% 1	2948
	21st to end	Night	50% 8% 13% 21% 9%	3536
September	1st to 10th	Night	41% 7% 15% 25% 11% 1	2000
	11th to 20th	Night	40% 8% 16% 28% 7% 1	2163
	21st to end	Night	45% 5% 13% 25% 12%	2200
October	1st to 10th	Night	49% 7% 12% 24% 8%	3638
	11th to 20th	Night	51% 7% 15% 24% 3	4156
	21st to end	Night	52% 6% 17% 16% 9%	4610
November	1st to 10th	Night	55% 7% 12% 19% 6% 1	2667
	11th to 20th	Night	55% 7% 12% 17% 9%	2750
	21st to end	Night	65% 6% 10% 13% 6%	3081
December	1st to 10th	Night	66% 5% 12% 12% 4	5060
	11th to 20th	Night	65% 4 8% 16% 6%	5742
	21st to end	Night	63% 4 7% 15% 10% 1	7455

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% 34% 16% 3	220
	11th to 20th	Day	26% 20% 33% 15% 5%	220
	21st to end	Day	18% 20% 43% 13% 5%	242
February	1st to 10th	Day	23% 27% 35% 10% 3 1	223
	11th to 20th	Day	23% 27% 33% 15% 2	513
	21st to end	Day	25% 25% 30% 17% 3	446
March	1st to 10th	Day	29% 21% 30% 16% 4	540
	11th to 20th	Day	27% 24% 29% 15% 4 1	540
	21st to end	Day	27% 24% 27% 14% 6% 1	594
April	1st to 10th	Day	32% 21% 27% 15% 4	540
	11th to 20th	Day	32% 19% 27% 16% 5% 2	532
	21st to end	Day	29% 21% 31% 13% 4 2	540
May	1st to 10th	Day	32% 20% 30% 13% 5% 1	543
	11th to 20th	Day	26% 20% 29% 19% 6% 1	567
	21st to end	Day	28% 23% 30% 16% 4 1	617
June	1st to 10th	Day	22% 14% 32% 23% 8%	775
	11th to 20th	Day	23% 15% 30% 21% 10% 1	780
	21st to end	Day	26% 14% 27% 23% 9% 1	780
July	1st to 10th	Day	20% 15% 33% 22% 9% 1	570
	11th to 20th	Day	21% 16% 35% 19% 8% 1	564
	21st to end	Day	20% 15% 31% 23% 9% 2	620
August	1st to 10th	Day	18% 14% 30% 24% 12% 2	566
	11th to 20th	Day	21% 10% 25% 29% 12% 3	559
	21st to end	Day	23% 18% 22% 20% 13% 5%	619
September	1st to 10th	Day	22% 14% 27% 22% 12% 2	530
	11th to 20th	Day	21% 11% 25% 26% 13% 4	530
	21st to end	Day	23% 16% 26% 18% 13% 4	530
October	1st to 10th	Day	24% 16% 28% 20% 10% 1	530
	11th to 20th	Day	29% 17% 27% 18% 8% 1	444
	21st to end	Day	34% 18% 25% 17% 6%	462
November	1st to 10th	Day	35% 18% 23% 19% 4 1	425
	11th to 20th	Day	27% 20% 27% 17% 8% 1	409
	21st to end	Day	32% 25% 30% 12%	220
December	1st to 10th	Day	28% 17% 32% 15% 7%	220
	11th to 20th	Day	33% 23% 28% 12% 4 1	220
	21st to end	Day	31% 19% 31% 15% 3 1	242
January	1st to 10th	Night	26% 13% 34% 21% 5%	840
	11th to 20th	Night	26% 17% 27% 23% 6%	840
	21st to end	Night	15% 14% 35% 29% 7%	924
February	1st to 10th	Night	17% 15% 35% 27% 6%	840
	11th to 20th	Night	22% 18% 36% 20% 4	823
	21st to end	Night	22% 17% 29% 27% 4	692
March	1st to 10th	Night	22% 16% 34% 24% 4	840
	11th to 20th	Night	25% 17% 32% 20% 5% 1	840
	21st to end	Night	22% 16% 32% 22% 6% 1	924
April	1st to 10th	Night	29% 15% 28% 23% 5%	840
	11th to 20th	Night	26% 13% 32% 24% 5%	744
	21st to end	Night	28% 17% 29% 19% 6%	630
May	1st to 10th	Night	27% 13% 31% 24% 5%	560
	11th to 20th	Night	23% 11% 27% 31% 7%	414
	21st to end	Night	27% 8% 32% 25% 9%	455
June	1st to 10th	Night	24% 7% 25% 38% 7%	420
	11th to 20th	Night	23% 6% 23% 35% 12%	420
	21st to end	Night	24% 6% 21% 39% 11%	420
July	1st to 10th	Night	17% 7% 24% 41% 10% 1	410
	11th to 20th	Night	19% 7% 19% 41% 14%	408
	21st to end	Night	19% 6% 20% 38% 17% 1	460
August	1st to 10th	Night	19% 3 13% 43% 21%	418
	11th to 20th	Night	18% 6% 19% 37% 20%	593
	21st to end	Night	19% 9% 21% 32% 17% 1	828
September	1st to 10th	Night	21% 6% 25% 33% 15% 1	800
	11th to 20th	Night	20% 7% 21% 33% 18% 2	800
	21st to end	Night	24% 8% 24% 28% 16% 1	800
October	1st to 10th	Night	22% 12% 26% 28% 12% 1	800
	11th to 20th	Night	29% 11% 24% 27% 10%	800
	21st to end	Night	33% 12% 26% 24% 5%	880
November	1st to 10th	Night	29% 14% 25% 25% 7% 1	820
	11th to 20th	Night	27% 16% 24% 24% 8% 1	840
	21st to end	Night	31% 17% 26% 19% 6% 1	914
December	1st to 10th	Night	30% 12% 26% 25% 6%	950
	11th to 20th	Night	27% 20% 26% 21% 5% 1	950
	21st to end	Night	32% 15% 29% 19% 4 1	995

Page generated at 2026-08-27 04:07:10. Version ac07

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