Canadian Lakes
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canadian Lakes clear sky chart from 2005-11-06 to 2024-11-05.

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	13% 10% 4 8% 6% 5% 5% 4 5% 7% 33%	101294
	Night	14% 11% 4 9% 5% 5% 4 3 5% 6% 33%	97812
Transparency	Day	48% 7% 12% 20% 12% 1	104865
	Night	49% 6% 12% 21% 12% 1	102382
Seeing	Day	18% 13% 29% 23% 12% 4	15858
	Night	18% 10% 30% 29% 11% 1	25716

By Month

Percentage Cloud Cover SE (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	14% 22% 8% 13% 7% 6% 5% 3 4 5% 13%	2527
	11th to 20th	Day	13% 17% 7% 19% 13% 10% 5% 3 4 4 6%	2530
	21st to end	Day	20% 23% 10% 13% 7% 5% 4 3 4 3 9%	2783
February	1st to 10th	Day	11% 14% 6% 12% 10% 7% 7% 3 5% 6% 18%	1703
	11th to 20th	Day	12% 14% 6% 13% 10% 5% 5% 3 4 6% 21%	1848
	21st to end	Day	12% 16% 7% 11% 6% 5% 5% 3 5% 6% 22%	1570
March	1st to 10th	Day	14% 13% 4 9% 5% 6% 4 4 4 6% 31%	3120
	11th to 20th	Day	11% 8% 6% 10% 6% 6% 6% 4 5% 6% 31%	3406
	21st to end	Day	19% 12% 6% 9% 5% 4 4 3 5% 5% 29%	3930
April	1st to 10th	Day	18% 13% 3 7% 5% 5% 4 4 5% 6% 30%	2280
	11th to 20th	Day	18% 10% 3 7% 4 5% 4 3 5% 5% 35%	2337
	21st to end	Day	16% 10% 3 8% 6% 5% 4 3 5% 7% 33%	2470
May	1st to 10th	Day	16% 8% 2 7% 5% 4 4 4 5% 7% 38%	4082
	11th to 20th	Day	13% 7% 2 6% 4 4 5% 4 6% 8% 40%	4101
	21st to end	Day	11% 6% 3 6% 5% 4 4 4 6% 8% 44%	4824
June	1st to 10th	Day	11% 6% 2 5% 5% 4 4 5% 5% 8% 43%	2660
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 6% 8% 43%	2660
	21st to end	Day	11% 6% 2 6% 4 6% 5% 5% 6% 8% 41%	2660
July	1st to 10th	Day	12% 6% 3 8% 5% 5% 5% 4 7% 9% 36%	4440
	11th to 20th	Day	6% 4 2 5% 4 4 6% 5% 7% 10% 48%	4440
	21st to end	Day	7% 5% 2 7% 5% 5% 4 4 7% 9% 44%	4813
August	1st to 10th	Day	11% 5% 2 7% 5% 6% 6% 5% 7% 8% 39%	4145
	11th to 20th	Day	12% 5% 2 6% 4 4 5% 4 5% 7% 47%	4044
	21st to end	Day	9% 6% 3 7% 5% 5% 5% 5% 6% 8% 43%	4308
September	1st to 10th	Day	11% 6% 2 6% 5% 5% 5% 4 6% 7% 43%	2238
	11th to 20th	Day	12% 4 2 5% 4 5% 5% 3 6% 8% 46%	2090
	21st to end	Day	13% 7% 2 8% 5% 5% 4 3 6% 7% 40%	2090
October	1st to 10th	Day	17% 7% 3 6% 5% 4 3 3 5% 5% 42%	2090
	11th to 20th	Day	19% 10% 4 9% 5% 6% 5% 4 4 7% 26%	1837
	21st to end	Day	20% 11% 3 9% 7% 7% 5% 3 5% 7% 23%	1881
November	1st to 10th	Day	13% 11% 4 8% 5% 4 4 3 6% 6% 35%	1708
	11th to 20th	Day	12% 18% 6% 11% 6% 5% 4 3 5% 6% 23%	1710
	21st to end	Day	21% 16% 5% 10% 5% 4 3 3 5% 6% 21%	1710
December	1st to 10th	Day	14% 18% 9% 13% 7% 6% 5% 4 4 5% 17%	1558
	11th to 20th	Day	13% 18% 6% 13% 7% 6% 5% 4 5% 6% 16%	1918
	21st to end	Day	23% 21% 7% 12% 6% 5% 4 3 4 4 10%	2783
January	1st to 10th	Night	15% 19% 9% 13% 6% 5% 4 3 4 4 17%	4428
	11th to 20th	Night	12% 17% 8% 17% 9% 12% 5% 3 4 4 10%	4440
	21st to end	Night	19% 20% 9% 13% 5% 5% 4 3 5% 5% 12%	4884
February	1st to 10th	Night	12% 15% 6% 11% 10% 6% 5% 5% 5% 5% 20%	2472
	11th to 20th	Night	12% 13% 5% 12% 8% 5% 5% 4 6% 6% 25%	2218
	21st to end	Night	15% 14% 5% 12% 6% 5% 4 4 5% 6% 25%	1884
March	1st to 10th	Night	15% 8% 4 7% 5% 4 4 3 5% 6% 37%	3733
	11th to 20th	Night	10% 9% 3 6% 5% 5% 4 3 5% 8% 42%	3554
	21st to end	Night	15% 12% 5% 9% 6% 5% 4 3 5% 6% 30%	3732
April	1st to 10th	Night	16% 12% 3 6% 6% 4 4 3 4 6% 36%	1900
	11th to 20th	Night	19% 9% 3 6% 4 4 4 3 5% 6% 36%	1792
	21st to end	Night	17% 8% 2 7% 4 4 4 4 6% 7% 37%	1710
May	1st to 10th	Night	12% 8% 3 8% 5% 5% 5% 3 6% 7% 38%	2813
	11th to 20th	Night	15% 7% 2 6% 4 4 4 3 6% 8% 41%	2790
	21st to end	Night	15% 7% 2 6% 4 4 3 3 4 6% 45%	2743
June	1st to 10th	Night	11% 7% 2 6% 4 4 3 4 6% 10% 43%	1520
	11th to 20th	Night	10% 6% 2 7% 5% 3 3 4 6% 10% 45%	1520
	21st to end	Night	8% 6% 2 6% 5% 3 5% 4 6% 8% 48%	1520
July	1st to 10th	Night	10% 7% 3 7% 5% 5% 5% 4 6% 7% 42%	2530
	11th to 20th	Night	6% 4 2 4 4 4 4 4 5% 7% 57%	2530
	21st to end	Night	8% 4 2 5% 4 4 4 4 5% 7% 51%	2750
August	1st to 10th	Night	11% 5% 2 6% 4 3 3 3 5% 8% 50%	2782
	11th to 20th	Night	11% 4 2 5% 3 4 4 3 6% 8% 51%	2785
	21st to end	Night	9% 5% 2 6% 4 4 5% 3 5% 7% 49%	3344
September	1st to 10th	Night	9% 5% 2 4 4 4 4 4 5% 8% 51%	1922
	11th to 20th	Night	11% 5% 1 4 3 3 3 3 5% 7% 54%	2090
	21st to end	Night	14% 6% 3 6% 4 4 5% 3 5% 9% 41%	2090
October	1st to 10th	Night	17% 7% 2 4 3 3 3 3 4 7% 47%	2090
	11th to 20th	Night	18% 9% 4 7% 5% 4 4 4 4 7% 34%	2337
	21st to end	Night	21% 11% 3 8% 5% 4 4 3 4 7% 31%	2717
November	1st to 10th	Night	13% 11% 3 7% 5% 4 4 3 6% 7% 38%	2470
	11th to 20th	Night	14% 14% 4 10% 5% 5% 5% 4 7% 6% 25%	2470
	21st to end	Night	17% 15% 5% 10% 5% 5% 5% 4 5% 6% 25%	2470
December	1st to 10th	Night	15% 17% 6% 12% 7% 7% 5% 5% 4 5% 17%	2619
	11th to 20th	Night	15% 19% 6% 13% 7% 5% 5% 4 5% 5% 17%	3279
	21st to end	Night	25% 21% 6% 11% 5% 4 3 3 4 4 13%	4884

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	72% 6% 12% 8% 2	2528
	11th to 20th	Day	84% 5% 5% 4 1	2530
	21st to end	Day	79% 6% 7% 6% 2	2783
February	1st to 10th	Day	65% 7% 10% 13% 5%	1703
	11th to 20th	Day	63% 5% 9% 13% 8%	1858
	21st to end	Day	62% 7% 11% 14% 6%	1570
March	1st to 10th	Day	53% 6% 12% 20% 9% 1	3120
	11th to 20th	Day	51% 6% 14% 18% 10% 1	3406
	21st to end	Day	58% 5% 9% 17% 10% 1	3930
April	1st to 10th	Day	54% 5% 11% 18% 11%	2280
	11th to 20th	Day	50% 6% 11% 19% 13% 2	2337
	21st to end	Day	50% 6% 11% 17% 13% 2	2470
May	1st to 10th	Day	43% 7% 11% 21% 16% 2	4120
	11th to 20th	Day	38% 9% 14% 24% 13% 2	4105
	21st to end	Day	37% 6% 12% 21% 22% 2	4837
June	1st to 10th	Day	37% 7% 11% 28% 15% 2	2660
	11th to 20th	Day	38% 7% 12% 23% 19% 1	2660
	21st to end	Day	39% 9% 12% 23% 15% 2	2660
July	1st to 10th	Day	43% 7% 13% 20% 15% 3	4371
	11th to 20th	Day	29% 7% 15% 31% 16% 2	4365
	21st to end	Day	33% 9% 13% 23% 21% 2	4662
August	1st to 10th	Day	40% 7% 10% 27% 15% 1	4130
	11th to 20th	Day	35% 7% 12% 28% 17% 1	4083
	21st to end	Day	37% 7% 14% 26% 15% 1	4307
September	1st to 10th	Day	38% 7% 14% 26% 13% 2	2238
	11th to 20th	Day	34% 7% 14% 30% 15% 1	2090
	21st to end	Day	42% 6% 13% 25% 13%	2090
October	1st to 10th	Day	31% 4 9% 33% 20% 3	3480
	11th to 20th	Day	44% 5% 12% 25% 14%	3027
	21st to end	Day	54% 5% 14% 20% 7%	3081
November	1st to 10th	Day	48% 6% 13% 21% 11%	1708
	11th to 20th	Day	60% 6% 13% 14% 5%	1710
	21st to end	Day	63% 7% 12% 13% 5%	1710
December	1st to 10th	Day	70% 6% 9% 12% 3	1558
	11th to 20th	Day	66% 7% 14% 11% 2	1915
	21st to end	Day	77% 6% 8% 6% 3	2783
January	1st to 10th	Night	67% 6% 11% 10% 5%	4428
	11th to 20th	Night	77% 6% 7% 6% 3	4440
	21st to end	Night	72% 7% 11% 7% 3	4884
February	1st to 10th	Night	63% 6% 11% 13% 6% 1	2472
	11th to 20th	Night	59% 7% 9% 16% 8% 1	2219
	21st to end	Night	58% 6% 12% 15% 8% 1	1884
March	1st to 10th	Night	46% 6% 15% 24% 8% 1	3733
	11th to 20th	Night	38% 6% 16% 24% 15% 2	3554
	21st to end	Night	53% 6% 12% 19% 9% 1	3732
April	1st to 10th	Night	49% 5% 10% 21% 15% 1	1900
	11th to 20th	Night	47% 5% 10% 20% 16% 2	1792
	21st to end	Night	44% 7% 12% 21% 14% 3	1710
May	1st to 10th	Night	43% 8% 13% 19% 16% 3	2840
	11th to 20th	Night	40% 7% 9% 25% 17% 1	2791
	21st to end	Night	41% 5% 10% 21% 20% 3	2751
June	1st to 10th	Night	36% 6% 12% 27% 18% 2	1520
	11th to 20th	Night	35% 6% 13% 23% 22% 1	1520
	21st to end	Night	34% 7% 13% 27% 17% 2	1520
July	1st to 10th	Night	39% 7% 10% 25% 12% 7%	2490
	11th to 20th	Night	26% 6% 13% 31% 23% 2	2482
	21st to end	Night	31% 7% 17% 21% 22% 2	2662
August	1st to 10th	Night	32% 6% 13% 30% 18% 1	2773
	11th to 20th	Night	32% 6% 10% 36% 16% 1	2812
	21st to end	Night	34% 6% 12% 28% 18% 1	3344
September	1st to 10th	Night	31% 7% 11% 31% 18% 1	1922
	11th to 20th	Night	29% 5% 12% 36% 17% 1	2090
	21st to end	Night	40% 6% 14% 26% 13% 1	2090
October	1st to 10th	Night	29% 4 10% 38% 18% 2	3480
	11th to 20th	Night	42% 5% 11% 24% 17% 1	3886
	21st to end	Night	46% 4 10% 29% 11%	4467
November	1st to 10th	Night	45% 6% 13% 22% 13% 1	2470
	11th to 20th	Night	55% 7% 16% 17% 6% 1	2470
	21st to end	Night	59% 5% 16% 16% 4	2470
December	1st to 10th	Night	67% 7% 10% 11% 4	2619
	11th to 20th	Night	66% 6% 14% 10% 3	3281
	21st to end	Night	74% 6% 10% 7% 3	4884

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	23% 16% 34% 21% 5% 1	270
	11th to 20th	Day	25% 19% 36% 15% 6%	270
	21st to end	Day	25% 15% 35% 20% 5%	297
February	1st to 10th	Day	18% 23% 36% 19% 4 1	270
	11th to 20th	Day	21% 29% 34% 13% 3	270
	21st to end	Day	28% 26% 34% 11% 1	225
March	1st to 10th	Day	21% 26% 37% 13% 3	270
	11th to 20th	Day	25% 13% 31% 22% 8% 1	412
	21st to end	Day	27% 16% 30% 20% 6% 1	506
April	1st to 10th	Day	25% 17% 32% 20% 6% 1	460
	11th to 20th	Day	27% 19% 31% 14% 6% 3	452
	21st to end	Day	22% 15% 31% 21% 10% 2	460
May	1st to 10th	Day	22% 17% 32% 19% 7% 3	463
	11th to 20th	Day	18% 12% 31% 24% 11% 4	494
	21st to end	Day	14% 11% 29% 27% 14% 4	734
June	1st to 10th	Day	12% 11% 34% 28% 11% 4	680
	11th to 20th	Day	16% 11% 30% 28% 11% 4	680
	21st to end	Day	15% 9% 32% 28% 13% 4	680
July	1st to 10th	Day	9% 6% 26% 31% 19% 8%	671
	11th to 20th	Day	8% 10% 26% 29% 19% 7%	668
	21st to end	Day	9% 6% 30% 29% 17% 8%	739
August	1st to 10th	Day	11% 6% 24% 26% 23% 10%	515
	11th to 20th	Day	12% 6% 19% 27% 23% 13%	479
	21st to end	Day	14% 6% 22% 29% 21% 9%	539
September	1st to 10th	Day	13% 9% 24% 26% 20% 9%	490
	11th to 20th	Day	10% 7% 18% 30% 23% 11%	490
	21st to end	Day	18% 11% 22% 26% 17% 6%	490
October	1st to 10th	Day	22% 12% 27% 22% 15% 3	490
	11th to 20th	Day	26% 15% 29% 24% 5%	405
	21st to end	Day	29% 18% 32% 15% 4 2	330
November	1st to 10th	Day	23% 19% 33% 19% 5% 1	282
	11th to 20th	Day	20% 23% 37% 15% 3 1	270
	21st to end	Day	31% 19% 31% 14% 5%	270
December	1st to 10th	Day	25% 24% 29% 15% 5% 1	270
	11th to 20th	Day	23% 20% 40% 14% 4	270
	21st to end	Day	27% 23% 33% 14% 3 1	297
January	1st to 10th	Night	22% 16% 33% 21% 6% 1	950
	11th to 20th	Night	23% 15% 33% 23% 5% 1	950
	21st to end	Night	20% 10% 33% 30% 6%	1045
February	1st to 10th	Night	19% 14% 36% 26% 3 1	789
	11th to 20th	Night	20% 14% 38% 24% 4	743
	21st to end	Night	23% 18% 36% 20% 3	628
March	1st to 10th	Night	19% 13% 35% 24% 9%	760
	11th to 20th	Night	17% 13% 36% 25% 7% 1	760
	21st to end	Night	22% 11% 35% 25% 6% 1	789
April	1st to 10th	Night	21% 12% 34% 27% 5% 1	570
	11th to 20th	Night	25% 10% 34% 24% 6% 1	563
	21st to end	Night	19% 14% 32% 27% 7% 1	570
May	1st to 10th	Night	17% 11% 32% 32% 8% 1	570
	11th to 20th	Night	18% 9% 32% 30% 11% 1	561
	21st to end	Night	13% 7% 28% 31% 19% 1	617
June	1st to 10th	Night	13% 9% 29% 34% 14% 1	570
	11th to 20th	Night	13% 6% 28% 37% 15% 1	570
	21st to end	Night	10% 5% 27% 42% 16% 1	570
July	1st to 10th	Night	8% 2 20% 42% 25% 3	555
	11th to 20th	Night	7% 4 21% 43% 22% 2	552
	21st to end	Night	9% 3 23% 41% 23% 1	624
August	1st to 10th	Night	9% 3 19% 45% 23% 2	567
	11th to 20th	Night	10% 3 19% 40% 24% 5%	564
	21st to end	Night	12% 4 20% 40% 23% 2	627
September	1st to 10th	Night	9% 4 23% 37% 22% 4	592
	11th to 20th	Night	12% 4 21% 36% 23% 4	760
	21st to end	Night	16% 7% 24% 32% 17% 4	760
October	1st to 10th	Night	21% 7% 23% 34% 15% 1	760
	11th to 20th	Night	21% 13% 29% 27% 9% 1	760
	21st to end	Night	27% 11% 32% 23% 6%	836
November	1st to 10th	Night	19% 11% 33% 28% 8% 1	760
	11th to 20th	Night	23% 15% 35% 22% 5% 1	760
	21st to end	Night	23% 14% 32% 27% 4 1	760
December	1st to 10th	Night	22% 15% 34% 25% 5%	909
	11th to 20th	Night	24% 14% 37% 20% 4 1	950
	21st to end	Night	31% 13% 34% 21% 2	1045

Page generated at 2024-11-03 02:11:18. Version ac07

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