Louiseville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Louiseville clear sky chart from 2005-11-06 to 2026-03-18.

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	16% 9% 3 8% 5% 5% 5% 4 5% 7% 32%	131225
	Night	17% 11% 4 9% 5% 5% 4 4 5% 6% 30%	130277
Transparency	Day	49% 7% 13% 20% 10% 1	134669
	Night	54% 6% 11% 18% 10% 1	134920
Seeing	Day	20% 8% 26% 27% 15% 4	16166
	Night	22% 6% 27% 32% 11% 1	25204

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	15% 16% 5% 11% 5% 3 3 2 4 6% 30%	4661
	11th to 20th	Day	12% 16% 6% 12% 7% 6% 5% 4 5% 5% 23%	4650
	21st to end	Day	8% 12% 5% 11% 7% 5% 5% 4 5% 7% 30%	5124
February	1st to 10th	Day	13% 16% 4 9% 7% 6% 5% 3 4 6% 28%	1775
	11th to 20th	Day	14% 14% 5% 10% 6% 4 5% 4 5% 5% 28%	1974
	21st to end	Day	15% 15% 4 9% 7% 5% 4 3 4 5% 29%	1730
March	1st to 10th	Day	21% 12% 5% 9% 6% 4 5% 4 4 5% 27%	4576
	11th to 20th	Day	10% 13% 4 9% 5% 4 5% 4 5% 6% 34%	4736
	21st to end	Day	17% 11% 4 9% 5% 5% 4 3 4 5% 34%	5970
April	1st to 10th	Day	21% 10% 3 7% 5% 4 4 3 6% 5% 32%	2400
	11th to 20th	Day	20% 7% 2 6% 4 4 4 4 4 5% 38%	2388
	21st to end	Day	21% 10% 3 6% 5% 3 4 4 5% 6% 32%	2600
May	1st to 10th	Day	26% 8% 3 8% 5% 4 5% 3 5% 6% 27%	6207
	11th to 20th	Day	19% 8% 3 7% 4 4 5% 3 5% 7% 34%	6318
	21st to end	Day	19% 9% 3 7% 5% 5% 5% 4 5% 8% 31%	6949
June	1st to 10th	Day	19% 8% 3 7% 5% 5% 5% 4 6% 8% 30%	2800
	11th to 20th	Day	15% 6% 2 7% 5% 5% 5% 4 6% 9% 37%	2800
	21st to end	Day	19% 7% 3 8% 6% 6% 5% 4 6% 8% 29%	2800
July	1st to 10th	Day	14% 6% 2 8% 6% 5% 5% 5% 7% 9% 33%	6360
	11th to 20th	Day	11% 6% 2 7% 5% 5% 6% 5% 7% 10% 36%	6360
	21st to end	Day	9% 5% 2 6% 4 4 5% 5% 7% 9% 44%	6926
August	1st to 10th	Day	13% 6% 2 7% 5% 5% 6% 6% 8% 11% 32%	4563
	11th to 20th	Day	17% 5% 2 6% 5% 4 5% 3 6% 10% 36%	4219
	21st to end	Day	17% 5% 2 6% 4 4 5% 4 6% 8% 40%	4312
September	1st to 10th	Day	12% 5% 2 5% 5% 4 5% 4 6% 9% 42%	2400
	11th to 20th	Day	13% 6% 2 5% 4 4 3 4 5% 6% 48%	2286
	21st to end	Day	18% 6% 3 6% 4 4 4 4 5% 7% 41%	2200
October	1st to 10th	Day	18% 6% 3 7% 5% 4 5% 3 5% 7% 38%	2105
	11th to 20th	Day	19% 8% 3 8% 5% 6% 6% 4 6% 7% 29%	1910
	21st to end	Day	23% 10% 3 8% 4 4 4 3 4 6% 30%	1980
November	1st to 10th	Day	16% 10% 3 8% 5% 5% 4 4 5% 7% 33%	1851
	11th to 20th	Day	19% 10% 4 8% 5% 4 5% 4 5% 6% 30%	1821
	21st to end	Day	21% 14% 3 8% 5% 5% 4 4 5% 5% 26%	1680
December	1st to 10th	Day	20% 16% 4 10% 7% 5% 4 3 4 4 23%	2680
	11th to 20th	Day	19% 12% 4 9% 6% 4 4 3 5% 5% 29%	3066
	21st to end	Day	22% 13% 4 9% 6% 4 4 3 5% 7% 23%	4048
January	1st to 10th	Night	14% 18% 6% 13% 6% 5% 5% 3 4 4 23%	8234
	11th to 20th	Night	12% 18% 7% 15% 6% 5% 4 3 4 5% 19%	8235
	21st to end	Night	8% 13% 5% 14% 8% 6% 6% 4 5% 6% 25%	9057
February	1st to 10th	Night	12% 15% 6% 10% 6% 5% 5% 4 5% 6% 27%	2841
	11th to 20th	Night	14% 12% 5% 11% 6% 5% 4 4 5% 4 29%	2531
	21st to end	Night	15% 13% 4 9% 6% 4 4 3 5% 5% 31%	2076
March	1st to 10th	Night	24% 12% 3 10% 6% 4 3 3 4 4 26%	5484
	11th to 20th	Night	15% 13% 4 8% 5% 5% 5% 4 6% 7% 29%	5364
	21st to end	Night	16% 11% 4 10% 5% 4 5% 3 5% 5% 32%	4962
April	1st to 10th	Night	23% 11% 3 7% 4 4 4 3 4 6% 31%	2000
	11th to 20th	Night	20% 9% 2 6% 5% 5% 4 3 5% 6% 35%	1960
	21st to end	Night	23% 9% 3 6% 4 3 3 3 4 7% 35%	1800
May	1st to 10th	Night	26% 10% 4 7% 5% 4 4 4 6% 5% 25%	3763
	11th to 20th	Night	22% 7% 3 8% 5% 4 5% 4 5% 7% 31%	3575
	21st to end	Night	19% 9% 3 8% 5% 4 4 4 5% 7% 31%	3926
June	1st to 10th	Night	20% 8% 2 5% 4 4 4 4 7% 8% 34%	1600
	11th to 20th	Night	16% 8% 3 6% 4 4 5% 4 6% 8% 36%	1600
	21st to end	Night	20% 7% 2 6% 4 4 5% 5% 5% 8% 33%	1600
July	1st to 10th	Night	12% 5% 3 8% 5% 6% 6% 5% 8% 10% 32%	3600
	11th to 20th	Night	15% 6% 2 7% 4 5% 5% 4 5% 7% 40%	3600
	21st to end	Night	10% 5% 2 6% 5% 4 5% 4 7% 9% 44%	3926
August	1st to 10th	Night	13% 6% 3 8% 6% 5% 5% 4 6% 8% 36%	2586
	11th to 20th	Night	17% 6% 2 6% 4 4 5% 4 6% 7% 39%	2794
	21st to end	Night	19% 7% 3 7% 4 4 3 3 5% 6% 39%	3586
September	1st to 10th	Night	12% 4 2 6% 5% 5% 4 4 5% 7% 46%	2000
	11th to 20th	Night	14% 5% 2 5% 3 4 4 3 5% 7% 50%	2113
	21st to end	Night	17% 5% 2 6% 4 5% 4 3 5% 7% 44%	2200
October	1st to 10th	Night	17% 7% 2 7% 4 4 4 3 4 5% 42%	2291
	11th to 20th	Night	20% 8% 2 8% 4 4 4 3 5% 6% 36%	2490
	21st to end	Night	24% 7% 3 7% 4 4 4 3 4 6% 32%	2860
November	1st to 10th	Night	19% 9% 4 8% 4 4 4 3 4 6% 33%	2667
	11th to 20th	Night	20% 9% 4 7% 5% 4 4 4 5% 6% 32%	2798
	21st to end	Night	23% 13% 4 8% 5% 4 5% 3 3 5% 27%	2940
December	1st to 10th	Night	17% 15% 5% 10% 8% 6% 4 4 5% 5% 21%	4720
	11th to 20th	Night	24% 12% 4 8% 5% 4 4 3 4 6% 26%	5348
	21st to end	Night	24% 15% 5% 9% 4 3 3 3 4 5% 25%	7150

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	58% 4 13% 19% 5%	4662
	11th to 20th	Day	62% 5% 9% 14% 8% 1	4680
	21st to end	Day	53% 6% 9% 18% 13% 1	5124
February	1st to 10th	Day	58% 6% 9% 18% 8% 2	1775
	11th to 20th	Day	57% 6% 12% 14% 10% 1	1983
	21st to end	Day	57% 5% 9% 16% 10% 2	1730
March	1st to 10th	Day	59% 7% 8% 12% 11% 3	4579
	11th to 20th	Day	50% 7% 17% 12% 12% 2	4736
	21st to end	Day	53% 4 8% 17% 15% 3	5970
April	1st to 10th	Day	52% 6% 10% 17% 13% 2	2400
	11th to 20th	Day	47% 6% 10% 22% 13% 3	2388
	21st to end	Day	53% 6% 10% 16% 13% 3	2600
May	1st to 10th	Day	57% 6% 9% 18% 10% 1	6218
	11th to 20th	Day	48% 8% 17% 16% 8% 2	6322
	21st to end	Day	50% 8% 11% 16% 13% 2	6949
June	1st to 10th	Day	50% 8% 11% 19% 10% 2	2800
	11th to 20th	Day	42% 8% 14% 23% 12% 2	2800
	21st to end	Day	51% 10% 10% 19% 10% 1	2800
July	1st to 10th	Day	45% 8% 15% 24% 8%	6290
	11th to 20th	Day	40% 8% 16% 27% 9%	6285
	21st to end	Day	34% 8% 15% 32% 10%	6728
August	1st to 10th	Day	42% 10% 18% 22% 8%	4549
	11th to 20th	Day	42% 9% 20% 23% 6%	4260
	21st to end	Day	41% 8% 14% 22% 14% 1	4312
September	1st to 10th	Day	37% 8% 17% 26% 11% 1	2400
	11th to 20th	Day	35% 7% 15% 31% 13% 1	2286
	21st to end	Day	42% 8% 13% 26% 11%	2200
October	1st to 10th	Day	46% 6% 14% 26% 8%	3430
	11th to 20th	Day	46% 8% 17% 24% 5%	3087
	21st to end	Day	45% 5% 20% 21% 8% 1	3180
November	1st to 10th	Day	50% 8% 12% 20% 9% 1	1851
	11th to 20th	Day	54% 5% 12% 17% 11%	1821
	21st to end	Day	61% 6% 13% 15% 5% 1	1680
December	1st to 10th	Day	66% 4 9% 16% 5%	2680
	11th to 20th	Day	58% 5% 8% 17% 12%	3066
	21st to end	Day	62% 7% 9% 14% 8%	4048
January	1st to 10th	Night	65% 5% 10% 14% 6% 1	8234
	11th to 20th	Night	68% 4 9% 13% 5%	8280
	21st to end	Night	59% 5% 9% 14% 13%	9057
February	1st to 10th	Night	58% 5% 10% 17% 9% 1	2841
	11th to 20th	Night	57% 6% 10% 16% 11% 1	2533
	21st to end	Night	55% 5% 8% 18% 13% 2	2076
March	1st to 10th	Night	62% 5% 8% 12% 10% 3	5494
	11th to 20th	Night	54% 5% 13% 15% 11% 2	5365
	21st to end	Night	54% 4 8% 22% 10% 2	4962
April	1st to 10th	Night	54% 4 10% 16% 15% 2	2000
	11th to 20th	Night	49% 6% 9% 19% 15% 3	1960
	21st to end	Night	51% 4 8% 19% 15% 3	1800
May	1st to 10th	Night	59% 7% 10% 14% 8% 2	3769
	11th to 20th	Night	52% 7% 13% 17% 10% 2	3576
	21st to end	Night	51% 6% 11% 16% 14% 1	3927
June	1st to 10th	Night	45% 7% 13% 20% 14% 1	1600
	11th to 20th	Night	43% 8% 12% 20% 14% 3	1600
	21st to end	Night	48% 9% 11% 18% 14% 1	1600
July	1st to 10th	Night	45% 8% 19% 21% 7%	3560
	11th to 20th	Night	41% 8% 16% 26% 8%	3552
	21st to end	Night	36% 7% 17% 28% 11%	3809
August	1st to 10th	Night	45% 8% 15% 25% 7%	2576
	11th to 20th	Night	43% 8% 18% 23% 8%	2819
	21st to end	Night	45% 7% 12% 22% 12% 1	3586
September	1st to 10th	Night	36% 7% 15% 27% 14% 1	2000
	11th to 20th	Night	35% 6% 15% 32% 11% 1	2113
	21st to end	Night	40% 7% 10% 28% 14%	2200
October	1st to 10th	Night	49% 5% 13% 24% 9%	3746
	11th to 20th	Night	44% 7% 15% 28% 7%	4052
	21st to end	Night	46% 5% 17% 19% 11% 2	4610
November	1st to 10th	Night	52% 5% 13% 20% 7% 1	2667
	11th to 20th	Night	53% 6% 12% 18% 10% 1	2798
	21st to end	Night	62% 5% 12% 14% 7%	2940
December	1st to 10th	Night	66% 5% 12% 12% 5%	4720
	11th to 20th	Night	62% 6% 7% 15% 10%	5348
	21st to end	Night	64% 7% 7% 14% 8%	7150

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% 10% 26% 29% 8%	220
	11th to 20th	Day	25% 12% 27% 26% 9% 2	220
	21st to end	Day	16% 7% 30% 31% 12% 4	242
February	1st to 10th	Day	22% 9% 36% 24% 8% 1	270
	11th to 20th	Day	23% 7% 33% 27% 9%	462
	21st to end	Day	23% 10% 28% 30% 9%	446
March	1st to 10th	Day	24% 8% 28% 31% 9% 1	540
	11th to 20th	Day	21% 14% 27% 27% 10% 1	528
	21st to end	Day	26% 10% 27% 24% 11% 3	550
April	1st to 10th	Day	24% 11% 25% 27% 12% 1	500
	11th to 20th	Day	26% 13% 26% 23% 10% 2	492
	21st to end	Day	28% 11% 30% 20% 9% 2	500
May	1st to 10th	Day	25% 10% 34% 20% 10% 2	503
	11th to 20th	Day	18% 7% 30% 24% 17% 4	527
	21st to end	Day	20% 11% 31% 22% 14% 3	573
June	1st to 10th	Day	20% 10% 27% 27% 13% 3	530
	11th to 20th	Day	17% 7% 24% 28% 21% 3	530
	21st to end	Day	20% 7% 23% 30% 17% 3	530
July	1st to 10th	Day	14% 6% 20% 33% 22% 6%	525
	11th to 20th	Day	15% 7% 23% 32% 20% 4	524
	21st to end	Day	13% 4 20% 35% 23% 6%	576
August	1st to 10th	Day	14% 5% 18% 31% 26% 6%	526
	11th to 20th	Day	14% 3 17% 31% 21% 13%	519
	21st to end	Day	14% 7% 23% 22% 22% 12%	583
September	1st to 10th	Day	13% 7% 25% 28% 18% 9%	530
	11th to 20th	Day	13% 7% 19% 25% 23% 13%	530
	21st to end	Day	19% 5% 23% 27% 18% 7%	530
October	1st to 10th	Day	20% 8% 23% 26% 20% 3	530
	11th to 20th	Day	22% 8% 29% 26% 13% 3	480
	21st to end	Day	29% 8% 25% 23% 14% 1	462
November	1st to 10th	Day	24% 12% 30% 24% 9% 1	425
	11th to 20th	Day	26% 7% 28% 26% 12% 1	361
	21st to end	Day	30% 10% 30% 21% 8% 1	220
December	1st to 10th	Day	30% 7% 23% 26% 10% 4	220
	11th to 20th	Day	27% 10% 29% 28% 4 1	220
	21st to end	Day	29% 9% 26% 24% 10% 2	242
January	1st to 10th	Night	27% 8% 27% 31% 8%	840
	11th to 20th	Night	27% 7% 29% 28% 8% 1	840
	21st to end	Night	17% 5% 29% 38% 9% 1	924
February	1st to 10th	Night	19% 6% 33% 32% 9% 1	840
	11th to 20th	Night	20% 8% 35% 30% 7%	823
	21st to end	Night	22% 6% 29% 36% 7%	692
March	1st to 10th	Night	24% 7% 28% 34% 6%	840
	11th to 20th	Night	23% 10% 30% 31% 6% 1	829
	21st to end	Night	21% 8% 32% 29% 9%	880
April	1st to 10th	Night	27% 8% 28% 31% 7%	800
	11th to 20th	Night	25% 10% 30% 28% 7%	776
	21st to end	Night	28% 9% 29% 27% 7%	600
May	1st to 10th	Night	26% 8% 30% 28% 7%	478
	11th to 20th	Night	24% 5% 26% 36% 9% 1	394
	21st to end	Night	21% 5% 37% 27% 10%	433
June	1st to 10th	Night	22% 4 27% 35% 12% 1	400
	11th to 20th	Night	20% 4 24% 38% 14% 1	400
	21st to end	Night	24% 4 20% 39% 14%	400
July	1st to 10th	Night	13% 5% 22% 42% 17% 2	390
	11th to 20th	Night	13% 2 23% 45% 17% 1	388
	21st to end	Night	14% 2 20% 46% 17% 1	438
August	1st to 10th	Night	14% 3 14% 44% 24% 1	398
	11th to 20th	Night	16% 2 16% 41% 22% 3	537
	21st to end	Night	18% 4 20% 35% 22% 2	880
September	1st to 10th	Night	15% 4 22% 41% 18% 1	800
	11th to 20th	Night	16% 5% 20% 33% 25% 2	800
	21st to end	Night	18% 6% 23% 33% 18% 2	800
October	1st to 10th	Night	21% 6% 26% 34% 13% 1	800
	11th to 20th	Night	23% 7% 26% 33% 11% 1	800
	21st to end	Night	28% 7% 29% 28% 7%	880
November	1st to 10th	Night	24% 9% 30% 28% 9% 1	820
	11th to 20th	Night	23% 8% 31% 27% 11%	840
	21st to end	Night	31% 8% 28% 25% 7% 1	840
December	1st to 10th	Night	29% 7% 29% 28% 7% 1	840
	11th to 20th	Night	25% 9% 31% 26% 8% 1	840
	21st to end	Night	33% 8% 24% 26% 8%	924

Page generated at 2026-03-15 02:23:53. Version ac07

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