Lake of Bays
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake of Bays clear sky chart from 2005-11-06 to 2024-01-12.

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	18% 11% 4 8% 6% 3 5% 4 5% 6% 30%	75168
	Night	18% 13% 5% 8% 6% 3 4 4 4 6% 29%	74528
Transparency	Day	54% 7% 10% 18% 10% 1	74872
	Night	56% 6% 10% 17% 9% 1	74359
Seeing	Day	24% 15% 30% 19% 8% 3	13708
	Night	24% 13% 29% 24% 9% 1	22634

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% 20% 11% 12% 8% 3 3 3 4 4 17%	1517
	11th to 20th	Day	16% 20% 10% 9% 6% 4 4 3 3 4 20%	1489
	21st to end	Day	14% 17% 8% 13% 8% 4 4 4 3 6% 19%	1782
February	1st to 10th	Day	12% 20% 8% 15% 9% 4 4 3 3 5% 17%	1620
	11th to 20th	Day	15% 14% 8% 13% 6% 3 5% 3 4 5% 24%	1573
	21st to end	Day	17% 18% 7% 11% 7% 3 5% 4 3 4 21%	1350
March	1st to 10th	Day	15% 14% 4 9% 8% 4 5% 4 5% 5% 27%	1967
	11th to 20th	Day	12% 14% 6% 10% 7% 4 5% 3 5% 6% 27%	1980
	21st to end	Day	18% 10% 4 6% 6% 3 4 5% 4 6% 35%	2178
April	1st to 10th	Day	21% 13% 5% 7% 5% 4 4 4 5% 6% 27%	2152
	11th to 20th	Day	22% 10% 3 5% 5% 3 4 4 4 5% 35%	2208
	21st to end	Day	21% 12% 3 6% 5% 3 4 3 4 5% 33%	2340
May	1st to 10th	Day	19% 7% 3 6% 5% 3 5% 4 5% 8% 33%	2402
	11th to 20th	Day	16% 10% 3 5% 5% 3 5% 4 5% 6% 37%	2478
	21st to end	Day	14% 7% 3 6% 5% 3 5% 5% 6% 8% 40%	2725
June	1st to 10th	Day	21% 8% 3 6% 6% 3 4 4 5% 7% 33%	2520
	11th to 20th	Day	16% 6% 2 5% 5% 4 5% 5% 6% 8% 38%	2655
	21st to end	Day	19% 7% 3 5% 6% 3 5% 5% 5% 8% 34%	2700
July	1st to 10th	Day	14% 5% 2 5% 5% 3 6% 5% 6% 9% 41%	2700
	11th to 20th	Day	13% 6% 3 6% 6% 3 5% 4 5% 8% 39%	2526
	21st to end	Day	14% 6% 2 6% 6% 4 5% 5% 6% 9% 37%	2680
August	1st to 10th	Day	14% 6% 3 6% 6% 3 6% 6% 5% 9% 37%	2327
	11th to 20th	Day	15% 6% 3 6% 6% 3 5% 5% 6% 8% 37%	2303
	21st to end	Day	15% 6% 2 6% 5% 4 5% 6% 6% 8% 35%	2483
September	1st to 10th	Day	17% 6% 2 6% 5% 3 5% 5% 6% 7% 38%	2160
	11th to 20th	Day	17% 6% 2 5% 5% 3 4 4 6% 7% 41%	2090
	21st to end	Day	20% 8% 3 6% 5% 3 5% 5% 4 5% 35%	1922
October	1st to 10th	Day	22% 8% 4 7% 6% 3 4 4 4 6% 33%	1800
	11th to 20th	Day	28% 11% 3 8% 6% 3 4 4 5% 6% 21%	1800
	21st to end	Day	31% 13% 4 7% 7% 2 3 4 5% 5% 20%	1980
November	1st to 10th	Day	20% 12% 4 7% 7% 2 4 5% 4 7% 28%	1523
	11th to 20th	Day	19% 16% 7% 10% 6% 3 4 5% 4 5% 21%	1520
	21st to end	Day	22% 21% 6% 10% 7% 3 5% 3 4 5% 14%	1520
December	1st to 10th	Day	19% 24% 8% 10% 5% 3 4 3 3 5% 16%	1520
	11th to 20th	Day	18% 24% 7% 11% 6% 2 3 3 3 3 19%	1906
	21st to end	Day	24% 22% 7% 12% 7% 2 3 3 4 3 13%	2772
January	1st to 10th	Night	19% 20% 9% 12% 8% 3 4 3 4 4 15%	2649
	11th to 20th	Night	18% 21% 9% 11% 7% 3 4 3 3 5% 17%	2496
	21st to end	Night	13% 15% 7% 12% 8% 5% 5% 4 4 5% 23%	2574
February	1st to 10th	Night	13% 19% 8% 12% 9% 4 4 4 5% 5% 17%	2340
	11th to 20th	Night	13% 16% 8% 12% 8% 3 5% 4 4 4 25%	2273
	21st to end	Night	17% 16% 8% 11% 7% 4 5% 4 3 5% 22%	1906
March	1st to 10th	Night	14% 12% 6% 8% 8% 3 4 3 4 5% 32%	1977
	11th to 20th	Night	14% 12% 7% 9% 6% 3 5% 4 5% 5% 31%	1979
	21st to end	Night	15% 11% 4 6% 6% 3 4 4 5% 5% 37%	2178
April	1st to 10th	Night	22% 13% 5% 5% 5% 3 4 4 4 6% 29%	1807
	11th to 20th	Night	19% 11% 4 5% 6% 2 5% 3 5% 6% 36%	1715
	21st to end	Night	20% 9% 3 8% 6% 4 4 5% 4 6% 30%	1620
May	1st to 10th	Night	19% 6% 2 6% 4 2 5% 4 6% 7% 38%	1555
	11th to 20th	Night	16% 8% 2 5% 5% 3 3 4 6% 7% 42%	1415
	21st to end	Night	11% 5% 3 5% 5% 3 5% 5% 6% 10% 43%	1550
June	1st to 10th	Night	17% 8% 4 6% 5% 3 5% 5% 6% 7% 36%	1440
	11th to 20th	Night	15% 7% 1 4 5% 3 4 4 6% 6% 44%	1298
	21st to end	Night	16% 6% 2 5% 6% 3 4 6% 5% 9% 37%	1260
July	1st to 10th	Night	11% 4 2 5% 5% 3 4 4 6% 7% 50%	1260
	11th to 20th	Night	13% 6% 2 6% 4 3 4 4 5% 7% 45%	1430
	21st to end	Night	11% 5% 3 4 4 3 6% 5% 6% 8% 45%	1636
August	1st to 10th	Night	12% 5% 2 5% 5% 2 4 5% 5% 8% 47%	1611
	11th to 20th	Night	12% 5% 3 5% 4 3 6% 5% 6% 7% 44%	1598
	21st to end	Night	15% 7% 2 6% 5% 3 5% 5% 6% 7% 41%	1854
September	1st to 10th	Night	13% 5% 2 5% 6% 3 4 5% 7% 8% 44%	1800
	11th to 20th	Night	15% 7% 2 4 4 3 4 4 5% 8% 44%	1867
	21st to end	Night	19% 7% 3 6% 4 3 4 4 4 7% 40%	2038
October	1st to 10th	Night	21% 8% 3 5% 5% 3 4 4 4 6% 35%	2160
	11th to 20th	Night	26% 12% 3 7% 5% 3 3 5% 4 6% 26%	2160
	21st to end	Night	28% 15% 4 7% 6% 3 4 4 4 4 22%	2376
November	1st to 10th	Night	22% 14% 3 7% 5% 3 3 4 4 6% 30%	2554
	11th to 20th	Night	18% 16% 5% 7% 5% 3 5% 5% 4 7% 25%	2660
	21st to end	Night	23% 18% 6% 8% 7% 3 5% 4 4 5% 16%	2660
December	1st to 10th	Night	21% 23% 8% 10% 6% 3 4 4 4 4 13%	2660
	11th to 20th	Night	19% 21% 8% 11% 6% 3 3 3 3 4 17%	3288
	21st to end	Night	24% 23% 8% 12% 7% 3 3 3 3 4 12%	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% 3 7% 13% 4	1518
	11th to 20th	Day	70% 3 6% 9% 9% 1	1489
	21st to end	Day	68% 4 7% 8% 11% 2	1782
February	1st to 10th	Day	73% 4 6% 11% 5% 1	1620
	11th to 20th	Day	64% 4 9% 11% 9% 2	1582
	21st to end	Day	70% 3 8% 12% 7%	1350
March	1st to 10th	Day	58% 7% 12% 12% 10% 1	1970
	11th to 20th	Day	59% 6% 8% 15% 10% 2	1980
	21st to end	Day	51% 5% 9% 17% 14% 4	2178
April	1st to 10th	Day	58% 5% 9% 16% 9% 2	2152
	11th to 20th	Day	52% 6% 8% 21% 13% 1	2208
	21st to end	Day	55% 5% 8% 18% 12% 3	2340
May	1st to 10th	Day	49% 6% 10% 20% 12% 3	2402
	11th to 20th	Day	47% 6% 9% 23% 14% 1	2482
	21st to end	Day	43% 8% 13% 20% 13% 4	2725
June	1st to 10th	Day	50% 7% 10% 20% 13%	2520
	11th to 20th	Day	43% 8% 11% 22% 14% 2	2655
	21st to end	Day	47% 8% 14% 20% 10% 2	2700
July	1st to 10th	Day	37% 8% 12% 27% 13% 2	2626
	11th to 20th	Day	42% 8% 12% 26% 11% 1	2450
	21st to end	Day	43% 8% 13% 26% 9%	2530
August	1st to 10th	Day	44% 9% 14% 22% 10% 1	2314
	11th to 20th	Day	43% 9% 15% 24% 8%	2303
	21st to end	Day	44% 10% 13% 23% 10% 1	2483
September	1st to 10th	Day	43% 8% 12% 25% 11% 1	2160
	11th to 20th	Day	41% 8% 12% 28% 11% 1	2090
	21st to end	Day	50% 7% 11% 25% 7%	1922
October	1st to 10th	Day	53% 7% 12% 18% 10% 1	1800
	11th to 20th	Day	63% 8% 11% 11% 6% 1	1800
	21st to end	Day	67% 6% 8% 13% 6%	1980
November	1st to 10th	Day	55% 8% 13% 17% 6%	1523
	11th to 20th	Day	64% 8% 10% 11% 5% 1	1520
	21st to end	Day	73% 6% 9% 8% 3	1520
December	1st to 10th	Day	73% 6% 8% 9% 4 1	1520
	11th to 20th	Day	72% 4 6% 9% 7% 1	1906
	21st to end	Day	77% 4 5% 11% 4	2772
January	1st to 10th	Night	74% 5% 8% 9% 5%	2649
	11th to 20th	Night	72% 5% 6% 8% 7% 2	2496
	21st to end	Night	64% 6% 6% 12% 10% 1	2574
February	1st to 10th	Night	69% 6% 9% 11% 5% 1	2340
	11th to 20th	Night	63% 4 8% 16% 8%	2275
	21st to end	Night	66% 4 8% 14% 6% 1	1906
March	1st to 10th	Night	55% 4 12% 15% 12% 2	1987
	11th to 20th	Night	54% 6% 9% 18% 10% 2	1980
	21st to end	Night	49% 5% 9% 20% 15% 3	2178
April	1st to 10th	Night	57% 5% 9% 16% 11% 2	1807
	11th to 20th	Night	50% 5% 7% 22% 15% 1	1715
	21st to end	Night	53% 6% 9% 16% 14% 2	1620
May	1st to 10th	Night	44% 6% 12% 20% 16% 2	1555
	11th to 20th	Night	41% 6% 10% 23% 18% 2	1416
	21st to end	Night	36% 8% 16% 23% 15% 3	1551
June	1st to 10th	Night	46% 9% 11% 20% 13% 2	1440
	11th to 20th	Night	38% 6% 13% 25% 18%	1298
	21st to end	Night	43% 9% 15% 22% 11% 1	1260
July	1st to 10th	Night	31% 8% 13% 26% 20% 2	1225
	11th to 20th	Night	38% 6% 12% 30% 12% 1	1383
	21st to end	Night	35% 8% 15% 28% 13% 1	1545
August	1st to 10th	Night	35% 8% 17% 28% 12% 1	1600
	11th to 20th	Night	36% 10% 17% 24% 11% 1	1598
	21st to end	Night	41% 8% 15% 26% 10% 1	1854
September	1st to 10th	Night	37% 9% 16% 24% 13% 1	1800
	11th to 20th	Night	38% 7% 15% 29% 11%	1867
	21st to end	Night	45% 6% 13% 28% 9%	2038
October	1st to 10th	Night	49% 8% 11% 19% 13%	2160
	11th to 20th	Night	59% 8% 11% 17% 5%	2160
	21st to end	Night	66% 6% 8% 12% 8%	2376
November	1st to 10th	Night	55% 6% 13% 19% 7%	2554
	11th to 20th	Night	59% 8% 11% 14% 7% 1	2660
	21st to end	Night	70% 7% 10% 10% 4	2660
December	1st to 10th	Night	76% 6% 6% 8% 3	2660
	11th to 20th	Night	71% 6% 7% 10% 6%	3288
	21st to end	Night	78% 4 6% 8% 4	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	20% 28% 32% 14% 5% 1	180
	11th to 20th	Day	30% 15% 36% 13% 4 2	181
	21st to end	Day	31% 16% 32% 14% 8%	264
February	1st to 10th	Day	30% 30% 32% 6% 2 1	240
	11th to 20th	Day	30% 25% 37% 6% 1	240
	21st to end	Day	36% 25% 31% 8%	216
March	1st to 10th	Day	25% 22% 34% 17% 1 1	420
	11th to 20th	Day	23% 23% 33% 15% 5% 1	420
	21st to end	Day	31% 15% 32% 18% 5% 1	462
April	1st to 10th	Day	26% 22% 28% 16% 7% 1	420
	11th to 20th	Day	32% 20% 21% 14% 9% 3	412
	21st to end	Day	31% 14% 31% 16% 6% 2	420
May	1st to 10th	Day	27% 14% 28% 21% 6% 4	423
	11th to 20th	Day	24% 15% 31% 18% 10% 3	447
	21st to end	Day	21% 16% 31% 19% 10% 3	485
June	1st to 10th	Day	23% 13% 35% 24% 4 2	450
	11th to 20th	Day	18% 15% 29% 24% 12% 2	585
	21st to end	Day	20% 13% 36% 20% 8% 3	630
July	1st to 10th	Day	13% 10% 32% 31% 11% 2	621
	11th to 20th	Day	18% 10% 25% 27% 14% 5%	449
	21st to end	Day	14% 11% 33% 28% 9% 5%	488
August	1st to 10th	Day	17% 8% 26% 29% 13% 6%	446
	11th to 20th	Day	18% 5% 25% 29% 15% 8%	439
	21st to end	Day	19% 9% 28% 23% 15% 6%	495
September	1st to 10th	Day	17% 12% 28% 24% 13% 6%	450
	11th to 20th	Day	16% 11% 25% 24% 18% 6%	450
	21st to end	Day	22% 13% 28% 24% 12% 3	450
October	1st to 10th	Day	26% 15% 24% 17% 13% 4	450
	11th to 20th	Day	32% 18% 31% 15% 3 1	450
	21st to end	Day	40% 14% 28% 14% 3	495
November	1st to 10th	Day	33% 19% 30% 16% 3	212
	11th to 20th	Day	33% 19% 33% 9% 5%	180
	21st to end	Day	34% 24% 34% 7% 2	180
December	1st to 10th	Day	34% 17% 36% 11% 3 1	180
	11th to 20th	Day	37% 28% 20% 13% 2 1	180
	21st to end	Day	30% 27% 29% 11% 2 2	198
January	1st to 10th	Night	28% 18% 31% 18% 5%	760
	11th to 20th	Night	30% 16% 31% 18% 4	727
	21st to end	Night	20% 13% 35% 22% 8% 1	792
February	1st to 10th	Night	24% 20% 34% 18% 3	720
	11th to 20th	Night	23% 19% 34% 19% 5%	703
	21st to end	Night	27% 21% 28% 20% 4	592
March	1st to 10th	Night	23% 18% 34% 21% 4	720
	11th to 20th	Night	21% 19% 33% 21% 5% 2	720
	21st to end	Night	21% 13% 32% 25% 8%	792
April	1st to 10th	Night	28% 14% 31% 22% 5%	720
	11th to 20th	Night	25% 13% 29% 22% 9% 1	651
	21st to end	Night	26% 10% 29% 26% 10%	540
May	1st to 10th	Night	24% 5% 27% 31% 11% 1	475
	11th to 20th	Night	21% 8% 32% 29% 10%	354
	21st to end	Night	12% 8% 35% 34% 10%	389
June	1st to 10th	Night	19% 8% 31% 33% 9% 1	360
	11th to 20th	Night	18% 9% 24% 37% 13%	360
	21st to end	Night	19% 6% 24% 37% 14% 1	360
July	1st to 10th	Night	11% 5% 22% 43% 18% 1	350
	11th to 20th	Night	16% 5% 24% 36% 18%	348
	21st to end	Night	11% 4 23% 41% 19% 1	456
August	1st to 10th	Night	14% 4 18% 36% 26% 2	537
	11th to 20th	Night	13% 5% 16% 39% 24% 3	534
	21st to end	Night	18% 7% 25% 29% 19% 2	666
September	1st to 10th	Night	16% 6% 26% 31% 18% 3	720
	11th to 20th	Night	17% 7% 25% 27% 20% 4	720
	21st to end	Night	23% 9% 21% 28% 18% 2	720
October	1st to 10th	Night	25% 11% 28% 23% 13% 1	720
	11th to 20th	Night	31% 13% 29% 19% 7% 1	720
	21st to end	Night	35% 13% 30% 17% 4	792
November	1st to 10th	Night	31% 12% 26% 24% 7% 1	740
	11th to 20th	Night	27% 18% 31% 17% 6%	760
	21st to end	Night	35% 15% 27% 18% 5%	760
December	1st to 10th	Night	33% 19% 29% 14% 4	760
	11th to 20th	Night	27% 21% 34% 13% 3 1	760
	21st to end	Night	34% 17% 28% 17% 3	836

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