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 2024-02-25.

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	20% 10% 4 7% 6% 3 5% 5% 5% 6% 29%	78017
	Night	19% 12% 4 7% 6% 3 4 4 5% 6% 30%	81273
Transparency	Day	54% 8% 12% 17% 8% 1	77722
	Night	55% 7% 12% 17% 9% 1	81103
Seeing	Day	25% 18% 29% 19% 7% 1	14123
	Night	25% 13% 27% 26% 8% 1	22881

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% 17% 5% 11% 8% 4 4 4 4 5% 21%	2517
	11th to 20th	Day	11% 14% 7% 16% 10% 3 5% 4 3 4 24%	2520
	21st to end	Day	11% 13% 5% 10% 6% 3 5% 5% 5% 6% 31%	2772
February	1st to 10th	Day	11% 15% 6% 12% 8% 5% 5% 5% 4 4 25%	1522
	11th to 20th	Day	14% 16% 7% 11% 6% 4 4 5% 4 6% 24%	1827
	21st to end	Day	13% 15% 6% 11% 7% 3 4 4 4 6% 26%	1520
March	1st to 10th	Day	16% 12% 5% 8% 7% 3 6% 3 5% 5% 30%	1797
	11th to 20th	Day	17% 14% 5% 7% 6% 3 5% 5% 4 5% 30%	1874
	21st to end	Day	15% 12% 4 8% 7% 4 6% 5% 4 5% 32%	2329
April	1st to 10th	Day	24% 11% 4 8% 6% 3 4 3 4 4 28%	2160
	11th to 20th	Day	22% 8% 3 5% 5% 3 3 4 4 5% 36%	2208
	21st to end	Day	24% 10% 3 7% 6% 3 4 4 3 6% 30%	2340
May	1st to 10th	Day	23% 7% 4 6% 4 3 4 4 5% 6% 33%	2416
	11th to 20th	Day	21% 7% 3 6% 5% 4 5% 5% 5% 6% 33%	2478
	21st to end	Day	23% 7% 3 6% 6% 4 5% 5% 5% 6% 32%	2725
June	1st to 10th	Day	22% 7% 4 7% 6% 4 6% 5% 6% 8% 25%	2695
	11th to 20th	Day	21% 7% 3 5% 5% 3 5% 5% 5% 7% 33%	2700
	21st to end	Day	25% 8% 3 7% 6% 4 5% 4 5% 6% 26%	2700
July	1st to 10th	Day	17% 7% 2 7% 6% 4 6% 5% 7% 8% 31%	2525
	11th to 20th	Day	17% 7% 2 6% 5% 5% 5% 6% 8% 9% 29%	2520
	21st to end	Day	18% 6% 3 6% 7% 4 6% 6% 6% 9% 29%	2744
August	1st to 10th	Day	19% 7% 3 6% 6% 4 6% 6% 7% 9% 27%	2506
	11th to 20th	Day	19% 6% 3 5% 6% 4 4 6% 6% 8% 33%	2312
	21st to end	Day	19% 6% 3 6% 5% 3 5% 6% 5% 8% 34%	2448
September	1st to 10th	Day	21% 7% 3 4 4 3 4 5% 5% 8% 35%	2160
	11th to 20th	Day	20% 5% 2 5% 3 3 3 4 5% 6% 43%	2013
	21st to end	Day	25% 6% 3 5% 4 2 3 4 5% 6% 37%	1980
October	1st to 10th	Day	23% 7% 3 5% 5% 3 6% 4 5% 6% 32%	1958
	11th to 20th	Day	28% 10% 4 7% 6% 4 5% 5% 5% 6% 22%	1660
	21st to end	Day	30% 10% 3 7% 6% 3 4 4 4 5% 25%	1782
November	1st to 10th	Day	22% 10% 4 7% 6% 3 4 4 4 5% 31%	1671
	11th to 20th	Day	23% 13% 5% 9% 6% 3 5% 3 4 5% 24%	1691
	21st to end	Day	21% 17% 5% 8% 6% 4 5% 5% 3 5% 20%	1390
December	1st to 10th	Day	26% 16% 4 9% 6% 3 3 4 3 4 22%	1330
	11th to 20th	Day	22% 13% 5% 10% 6% 3 4 3 3 4 27%	1668
	21st to end	Day	21% 19% 5% 7% 5% 2 3 4 4 5% 25%	2559
January	1st to 10th	Night	16% 19% 7% 11% 8% 3 4 3 4 4 22%	4429
	11th to 20th	Night	13% 16% 6% 11% 9% 4 4 4 4 5% 24%	4440
	21st to end	Night	10% 15% 6% 10% 8% 4 5% 5% 6% 6% 25%	4884
February	1st to 10th	Night	12% 13% 6% 9% 9% 4 5% 5% 4 5% 28%	2656
	11th to 20th	Night	13% 15% 6% 11% 7% 3 5% 4 4 5% 27%	2237
	21st to end	Night	15% 13% 5% 9% 6% 3 5% 4 5% 6% 28%	1831
March	1st to 10th	Night	15% 11% 5% 9% 7% 4 5% 4 5% 6% 30%	2150
	11th to 20th	Night	18% 12% 4 7% 7% 4 5% 4 5% 6% 28%	2084
	21st to end	Night	17% 11% 4 7% 5% 2 4 4 5% 6% 35%	2026
April	1st to 10th	Night	23% 13% 5% 6% 5% 3 4 4 5% 6% 27%	1800
	11th to 20th	Night	20% 9% 3 6% 5% 3 4 5% 5% 6% 34%	1701
	21st to end	Night	22% 10% 4 5% 4 3 4 4 3 7% 33%	1620
May	1st to 10th	Night	25% 6% 3 6% 5% 3 5% 4 5% 5% 33%	1561
	11th to 20th	Night	22% 7% 4 5% 5% 4 4 4 5% 6% 36%	1415
	21st to end	Night	24% 5% 3 5% 4 3 5% 4 5% 6% 37%	1550
June	1st to 10th	Night	22% 7% 3 7% 5% 3 5% 6% 5% 8% 29%	1260
	11th to 20th	Night	21% 6% 3 5% 4 3 5% 5% 6% 7% 37%	1260
	21st to end	Night	23% 6% 3 6% 6% 3 5% 5% 5% 7% 31%	1260
July	1st to 10th	Night	19% 5% 2 6% 5% 3 5% 5% 5% 8% 37%	1430
	11th to 20th	Night	17% 6% 3 6% 4 4 5% 5% 6% 8% 36%	1440
	21st to end	Night	17% 6% 2 6% 5% 3 5% 5% 7% 7% 36%	1574
August	1st to 10th	Night	17% 4 2 5% 4 4 5% 5% 7% 9% 38%	1432
	11th to 20th	Night	17% 7% 2 6% 5% 4 5% 5% 5% 8% 35%	1570
	21st to end	Night	18% 6% 2 5% 5% 3 4 5% 4 8% 40%	1903
September	1st to 10th	Night	19% 7% 2 5% 5% 2 3 4 6% 6% 41%	1800
	11th to 20th	Night	20% 6% 2 5% 4 3 3 4 5% 5% 44%	1946
	21st to end	Night	22% 6% 2 5% 4 3 4 3 4 6% 42%	1980
October	1st to 10th	Night	21% 8% 2 5% 4 3 5% 4 5% 6% 38%	1999
	11th to 20th	Night	26% 8% 3 5% 6% 3 4 5% 4 5% 30%	2299
	21st to end	Night	29% 11% 3 5% 4 3 4 4 5% 6% 28%	2574
November	1st to 10th	Night	20% 12% 3 6% 6% 3 4 3 5% 6% 30%	2407
	11th to 20th	Night	22% 11% 4 6% 5% 3 5% 4 4 6% 30%	2488
	21st to end	Night	24% 14% 5% 7% 5% 3 4 4 4 5% 25%	2787
December	1st to 10th	Night	24% 17% 5% 8% 7% 3 5% 4 4 4 20%	2850
	11th to 20th	Night	22% 15% 5% 9% 6% 3 3 3 4 5% 24%	3531
	21st to end	Night	24% 20% 5% 8% 5% 2 3 3 3 3 24%	5099

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	63% 8% 11% 13% 5%	2518
	11th to 20th	Day	62% 8% 9% 15% 6% 1	2520
	21st to end	Day	50% 9% 10% 21% 10% 1	2772
February	1st to 10th	Day	61% 6% 8% 14% 8% 2	1522
	11th to 20th	Day	61% 7% 10% 12% 9% 1	1836
	21st to end	Day	59% 4 9% 16% 9% 3	1520
March	1st to 10th	Day	55% 7% 9% 15% 12% 2	1800
	11th to 20th	Day	54% 8% 8% 15% 13% 1	1874
	21st to end	Day	53% 7% 9% 17% 11% 3	2329
April	1st to 10th	Day	60% 6% 10% 11% 9% 4	2160
	11th to 20th	Day	49% 7% 10% 21% 11% 3	2208
	21st to end	Day	57% 6% 9% 15% 12% 2	2340
May	1st to 10th	Day	52% 6% 10% 16% 13% 3	2416
	11th to 20th	Day	50% 8% 11% 18% 12% 1	2482
	21st to end	Day	52% 9% 9% 17% 12% 1	2725
June	1st to 10th	Day	54% 10% 11% 17% 7% 2	2695
	11th to 20th	Day	48% 8% 14% 17% 11% 1	2700
	21st to end	Day	58% 7% 11% 15% 8%	2700
July	1st to 10th	Day	47% 11% 16% 20% 6%	2455
	11th to 20th	Day	47% 12% 15% 19% 6%	2445
	21st to end	Day	50% 13% 15% 17% 6%	2591
August	1st to 10th	Day	51% 13% 17% 16% 3	2492
	11th to 20th	Day	46% 12% 16% 19% 6%	2312
	21st to end	Day	46% 11% 13% 21% 9%	2448
September	1st to 10th	Day	46% 9% 15% 20% 10%	2160
	11th to 20th	Day	41% 7% 17% 25% 10%	2013
	21st to end	Day	48% 8% 12% 23% 9%	1980
October	1st to 10th	Day	53% 7% 11% 21% 8%	1958
	11th to 20th	Day	61% 9% 13% 14% 2	1660
	21st to end	Day	62% 7% 10% 15% 5% 1	1782
November	1st to 10th	Day	56% 8% 11% 17% 7%	1671
	11th to 20th	Day	62% 7% 9% 15% 6% 1	1691
	21st to end	Day	65% 7% 12% 11% 5% 1	1390
December	1st to 10th	Day	66% 6% 10% 13% 5%	1330
	11th to 20th	Day	61% 6% 7% 18% 8%	1668
	21st to end	Day	63% 6% 10% 13% 7% 2	2559
January	1st to 10th	Night	65% 5% 12% 12% 5%	4429
	11th to 20th	Night	60% 8% 11% 16% 4 1	4440
	21st to end	Night	55% 9% 10% 15% 9% 1	4884
February	1st to 10th	Night	58% 5% 9% 17% 9% 1	2656
	11th to 20th	Night	60% 5% 10% 13% 10% 1	2239
	21st to end	Night	57% 6% 8% 15% 13% 2	1831
March	1st to 10th	Night	56% 6% 10% 15% 11% 2	2160
	11th to 20th	Night	56% 7% 10% 13% 12% 2	2085
	21st to end	Night	50% 6% 10% 19% 11% 4	2026
April	1st to 10th	Night	57% 6% 9% 14% 11% 2	1800
	11th to 20th	Night	48% 7% 9% 22% 12% 2	1701
	21st to end	Night	53% 6% 10% 16% 13% 2	1620
May	1st to 10th	Night	52% 6% 11% 16% 13% 2	1561
	11th to 20th	Night	49% 7% 11% 17% 14% 2	1416
	21st to end	Night	48% 6% 11% 20% 14% 2	1551
June	1st to 10th	Night	51% 8% 13% 18% 8% 1	1260
	11th to 20th	Night	44% 7% 14% 20% 12% 3	1260
	21st to end	Night	52% 8% 13% 17% 10%	1260
July	1st to 10th	Night	42% 11% 20% 19% 7%	1390
	11th to 20th	Night	45% 8% 19% 21% 7% 1	1392
	21st to end	Night	46% 9% 16% 21% 7%	1486
August	1st to 10th	Night	40% 9% 21% 25% 5%	1422
	11th to 20th	Night	45% 11% 19% 18% 6% 1	1570
	21st to end	Night	42% 9% 13% 28% 7%	1903
September	1st to 10th	Night	42% 7% 15% 23% 11% 1	1800
	11th to 20th	Night	42% 8% 16% 25% 7% 1	1946
	21st to end	Night	45% 5% 13% 26% 11%	1980
October	1st to 10th	Night	47% 6% 11% 23% 12% 1	1999
	11th to 20th	Night	54% 9% 13% 17% 6%	2299
	21st to end	Night	58% 6% 12% 16% 7% 1	2574
November	1st to 10th	Night	54% 7% 13% 19% 7% 1	2407
	11th to 20th	Night	56% 7% 12% 16% 10%	2488
	21st to end	Night	62% 6% 11% 14% 6%	2787
December	1st to 10th	Night	68% 5% 10% 12% 4	2850
	11th to 20th	Night	62% 5% 10% 14% 8%	3532
	21st to end	Night	65% 5% 8% 15% 6% 1	5099

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% 19% 33% 19% 3	180
	11th to 20th	Day	27% 19% 34% 17% 3	180
	21st to end	Day	18% 19% 44% 13% 6% 1	198
February	1st to 10th	Day	25% 27% 36% 9% 1 1	182
	11th to 20th	Day	23% 26% 33% 15% 2	435
	21st to end	Day	26% 27% 26% 18% 3	362
March	1st to 10th	Day	25% 21% 31% 17% 5%	420
	11th to 20th	Day	27% 24% 27% 17% 5% 1	420
	21st to end	Day	23% 23% 28% 18% 7% 1	462
April	1st to 10th	Day	30% 21% 27% 17% 5%	420
	11th to 20th	Day	30% 19% 26% 18% 6% 2	412
	21st to end	Day	29% 20% 33% 13% 3 2	420
May	1st to 10th	Day	29% 21% 31% 14% 5% 1	423
	11th to 20th	Day	24% 20% 31% 18% 6% 1	447
	21st to end	Day	26% 24% 29% 16% 4 1	485
June	1st to 10th	Day	24% 16% 31% 22% 7%	625
	11th to 20th	Day	23% 14% 29% 21% 11% 1	630
	21st to end	Day	26% 13% 27% 24% 10% 1	630
July	1st to 10th	Day	18% 15% 33% 24% 9% 1	450
	11th to 20th	Day	20% 13% 34% 21% 9% 2	444
	21st to end	Day	21% 15% 30% 24% 8% 2	488
August	1st to 10th	Day	20% 12% 30% 24% 12% 2	446
	11th to 20th	Day	23% 10% 23% 28% 13% 3	439
	21st to end	Day	23% 18% 23% 18% 14% 5%	495
September	1st to 10th	Day	22% 14% 27% 23% 12% 2	450
	11th to 20th	Day	23% 12% 25% 24% 12% 4	450
	21st to end	Day	24% 17% 26% 17% 13% 4	450
October	1st to 10th	Day	24% 17% 27% 20% 10% 1	450
	11th to 20th	Day	31% 18% 25% 17% 8% 1	380
	21st to end	Day	36% 17% 25% 17% 5%	396
November	1st to 10th	Day	33% 18% 22% 21% 5% 1	365
	11th to 20th	Day	27% 21% 26% 18% 8% 1	351
	21st to end	Day	33% 24% 28% 14% 1 1	180
December	1st to 10th	Day	31% 15% 32% 14% 7% 1	180
	11th to 20th	Day	31% 23% 29% 12% 4 1	180
	21st to end	Day	34% 18% 31% 14% 3 1	198
January	1st to 10th	Night	27% 13% 34% 21% 4	760
	11th to 20th	Night	26% 18% 28% 23% 6%	760
	21st to end	Night	16% 14% 35% 29% 6%	836
February	1st to 10th	Night	19% 15% 35% 27% 5%	760
	11th to 20th	Night	21% 18% 36% 20% 4	743
	21st to end	Night	23% 17% 28% 26% 4	611
March	1st to 10th	Night	20% 16% 33% 25% 5%	720
	11th to 20th	Night	25% 17% 32% 20% 5% 1	720
	21st to end	Night	23% 15% 30% 24% 7% 1	792
April	1st to 10th	Night	30% 14% 27% 24% 5%	720
	11th to 20th	Night	26% 12% 30% 26% 6%	637
	21st to end	Night	28% 18% 28% 19% 7%	540
May	1st to 10th	Night	27% 12% 31% 23% 6%	481
	11th to 20th	Night	24% 12% 27% 30% 7% 1	354
	21st to end	Night	28% 7% 32% 23% 10% 1	389
June	1st to 10th	Night	24% 8% 24% 36% 7%	360
	11th to 20th	Night	23% 5% 24% 36% 13%	360
	21st to end	Night	24% 6% 19% 39% 12%	360
July	1st to 10th	Night	18% 7% 23% 40% 11% 1	350
	11th to 20th	Night	18% 5% 20% 41% 16%	348
	21st to end	Night	19% 6% 19% 38% 17% 1	394
August	1st to 10th	Night	20% 2 13% 42% 22% 1	358
	11th to 20th	Night	18% 7% 20% 36% 20%	506
	21st to end	Night	18% 9% 22% 31% 17% 2	715
September	1st to 10th	Night	21% 6% 26% 32% 15% 1	720
	11th to 20th	Night	22% 8% 21% 32% 15% 2	720
	21st to end	Night	24% 9% 24% 27% 15% 1	720
October	1st to 10th	Night	23% 13% 25% 29% 11%	720
	11th to 20th	Night	30% 11% 23% 26% 10%	720
	21st to end	Night	33% 13% 26% 23% 5%	792
November	1st to 10th	Night	28% 14% 25% 25% 7% 1	740
	11th to 20th	Night	28% 17% 23% 23% 8% 1	760
	21st to end	Night	30% 17% 26% 20% 6% 1	820
December	1st to 10th	Night	32% 12% 24% 24% 6%	850
	11th to 20th	Night	26% 20% 26% 22% 5% 1	850
	21st to end	Night	33% 16% 28% 19% 3 1	895

Page generated at 2024-02-22 06:05:43. Version ac07

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