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 2025-10-04.

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% 12% 4 9% 5% 4 4 3 5% 6% 31%	127667
	Night	16% 14% 5% 10% 5% 4 4 3 5% 6% 28%	121718
Transparency	Day	54% 5% 10% 20% 10% 1	131243
	Night	57% 5% 10% 18% 10% 1	126230
Seeing	Day	24% 15% 30% 20% 8% 3	16037
	Night	24% 13% 29% 24% 10% 1	24727

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	12% 18% 8% 13% 6% 6% 4 3 3 4 23%	3597
	11th to 20th	Day	9% 22% 10% 16% 9% 7% 5% 3 3 3 13%	3681
	21st to end	Day	13% 20% 9% 16% 7% 6% 4 3 3 4 16%	4466
February	1st to 10th	Day	12% 21% 7% 16% 7% 5% 3 2 4 4 19%	1800
	11th to 20th	Day	14% 15% 8% 14% 6% 5% 4 3 4 5% 23%	1753
	21st to end	Day	16% 19% 6% 13% 6% 5% 4 3 3 4 21%	1505
March	1st to 10th	Day	18% 15% 4 11% 6% 5% 3 3 4 5% 25%	4922
	11th to 20th	Day	12% 15% 6% 11% 6% 5% 5% 4 6% 7% 24%	4980
	21st to end	Day	17% 16% 5% 8% 4 4 3 3 4 5% 32%	5465
April	1st to 10th	Day	20% 14% 4 7% 5% 5% 4 3 5% 6% 27%	2392
	11th to 20th	Day	22% 12% 3 6% 4 4 4 3 4 5% 34%	2458
	21st to end	Day	22% 13% 3 7% 4 4 3 3 4 5% 33%	2600
May	1st to 10th	Day	19% 9% 3 7% 5% 4 4 3 5% 8% 32%	6062
	11th to 20th	Day	14% 10% 3 7% 4 4 4 3 5% 7% 37%	6318
	21st to end	Day	20% 10% 3 7% 4 4 4 3 5% 6% 33%	6949
June	1st to 10th	Day	21% 9% 3 6% 6% 4 4 3 6% 7% 32%	2800
	11th to 20th	Day	15% 7% 2 6% 5% 5% 4 4 6% 8% 37%	2951
	21st to end	Day	20% 8% 2 6% 5% 4 4 4 5% 8% 34%	3000
July	1st to 10th	Day	15% 6% 2 7% 4 5% 6% 4 6% 9% 36%	6819
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 3 5% 7% 45%	6366
	21st to end	Day	9% 5% 2 5% 4 4 4 4 5% 9% 48%	6753
August	1st to 10th	Day	14% 7% 4 7% 5% 5% 6% 4 6% 8% 33%	4234
	11th to 20th	Day	18% 7% 3 7% 4 3 5% 5% 6% 9% 34%	4174
	21st to end	Day	10% 5% 2 6% 4 4 6% 5% 7% 9% 42%	4495
September	1st to 10th	Day	17% 7% 2 7% 4 4 5% 4 6% 7% 39%	2400
	11th to 20th	Day	15% 6% 2 5% 4 4 4 3 6% 7% 44%	2322
	21st to end	Day	20% 9% 3 7% 4 4 4 4 4 5% 36%	2135
October	1st to 10th	Day	21% 8% 3 8% 5% 4 4 3 5% 6% 34%	1930
	11th to 20th	Day	27% 12% 3 9% 5% 4 5% 3 5% 6% 22%	1900
	21st to end	Day	30% 13% 4 8% 5% 3 3 3 5% 5% 20%	2090
November	1st to 10th	Day	20% 13% 3 7% 7% 3 3 4 4 6% 28%	1604
	11th to 20th	Day	17% 18% 6% 11% 5% 5% 4 3 4 5% 22%	1600
	21st to end	Day	20% 23% 6% 11% 6% 4 4 3 4 4 14%	1600
December	1st to 10th	Day	17% 25% 9% 13% 4 4 4 3 4 4 12%	2600
	11th to 20th	Day	18% 25% 6% 14% 5% 3 2 2 3 4 18%	2986
	21st to end	Day	21% 21% 7% 15% 5% 3 3 2 3 4 15%	3960
January	1st to 10th	Night	13% 19% 8% 15% 6% 5% 4 3 4 5% 17%	6349
	11th to 20th	Night	11% 18% 8% 23% 8% 5% 4 3 4 4 11%	6200
	21st to end	Night	12% 20% 10% 15% 6% 8% 4 3 4 4 15%	6490
February	1st to 10th	Night	12% 19% 7% 13% 8% 5% 4 3 5% 4 19%	2600
	11th to 20th	Night	12% 17% 7% 13% 6% 5% 4 3 4 4 24%	2533
	21st to end	Night	16% 17% 6% 12% 6% 6% 4 3 4 5% 21%	2124
March	1st to 10th	Night	16% 15% 5% 11% 5% 4 4 3 5% 5% 28%	4915
	11th to 20th	Night	10% 14% 7% 10% 5% 5% 5% 4 6% 8% 26%	4979
	21st to end	Night	20% 12% 5% 7% 5% 4 4 3 5% 4 30%	5467
April	1st to 10th	Night	21% 14% 4 7% 4 4 4 3 4 5% 29%	2007
	11th to 20th	Night	19% 12% 3 6% 5% 4 4 2 5% 6% 35%	1907
	21st to end	Night	20% 10% 3 9% 5% 5% 4 4 5% 5% 30%	1800
May	1st to 10th	Night	19% 8% 2 7% 4 4 5% 4 6% 7% 34%	3876
	11th to 20th	Night	14% 8% 2 5% 4 3 3 4 5% 7% 43%	3575
	21st to end	Night	18% 9% 3 6% 4 4 4 4 6% 7% 35%	3926
June	1st to 10th	Night	17% 9% 3 6% 5% 5% 5% 4 6% 7% 35%	1600
	11th to 20th	Night	14% 8% 1 5% 4 3 4 3 6% 7% 43%	1442
	21st to end	Night	17% 7% 2 6% 6% 4 4 5% 6% 8% 37%	1400
July	1st to 10th	Night	14% 6% 3 7% 5% 4 5% 4 5% 7% 40%	3160
	11th to 20th	Night	16% 6% 2 5% 3 3 3 3 5% 6% 47%	3590
	21st to end	Night	10% 6% 2 5% 3 3 4 3 5% 7% 52%	4097
August	1st to 10th	Night	11% 5% 2 6% 4 3 5% 4 6% 8% 46%	2915
	11th to 20th	Night	17% 7% 3 6% 3 3 5% 3 5% 7% 41%	2875
	21st to end	Night	15% 5% 2 5% 3 3 4 3 5% 7% 48%	3369
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 6% 8% 44%	2000
	11th to 20th	Night	13% 7% 2 5% 4 3 3 4 5% 7% 48%	2075
	21st to end	Night	19% 8% 3 6% 3 4 3 3 4 6% 40%	2265
October	1st to 10th	Night	20% 9% 3 6% 4 4 4 3 5% 6% 37%	2317
	11th to 20th	Night	24% 12% 3 8% 4 4 3 4 4 6% 27%	2280
	21st to end	Night	27% 16% 4 8% 5% 4 4 3 4 4 22%	2508
November	1st to 10th	Night	21% 15% 3 7% 4 4 4 3 4 6% 29%	2693
	11th to 20th	Night	18% 17% 4 8% 4 4 5% 3 4 6% 26%	2800
	21st to end	Night	22% 20% 6% 10% 6% 5% 4 4 4 5% 16%	2800
December	1st to 10th	Night	19% 25% 8% 13% 5% 4 4 3 4 4 11%	4580
	11th to 20th	Night	17% 22% 8% 17% 5% 5% 3 2 3 4 13%	5208
	21st to end	Night	21% 22% 7% 14% 5% 4 3 2 3 3 15%	6996

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	67% 3 6% 17% 7%	3598
	11th to 20th	Day	78% 3 5% 8% 6% 1	3711
	21st to end	Day	73% 3 5% 9% 8% 1	4466
February	1st to 10th	Day	71% 4 6% 13% 5% 1	1800
	11th to 20th	Day	64% 5% 9% 11% 9% 2	1762
	21st to end	Day	69% 4 8% 12% 7%	1505
March	1st to 10th	Day	62% 6% 10% 8% 14% 1	4925
	11th to 20th	Day	59% 5% 13% 15% 7% 2	4980
	21st to end	Day	55% 4 8% 19% 13% 2	5465
April	1st to 10th	Day	58% 5% 9% 17% 10% 2	2392
	11th to 20th	Day	53% 5% 7% 21% 12% 1	2458
	21st to end	Day	55% 4 8% 18% 12% 3	2600
May	1st to 10th	Day	51% 5% 10% 19% 9% 6%	6071
	11th to 20th	Day	45% 6% 10% 20% 17% 1	6322
	21st to end	Day	52% 5% 10% 18% 12% 3	6949
June	1st to 10th	Day	51% 7% 9% 20% 12%	2800
	11th to 20th	Day	44% 7% 11% 24% 13% 1	2951
	21st to end	Day	48% 7% 14% 20% 10% 1	3000
July	1st to 10th	Day	45% 4 14% 27% 10% 1	6746
	11th to 20th	Day	39% 3 11% 34% 13%	6290
	21st to end	Day	35% 3 14% 34% 13%	6558
August	1st to 10th	Day	48% 5% 13% 25% 9% 1	4221
	11th to 20th	Day	46% 5% 14% 26% 8%	4213
	21st to end	Day	37% 6% 12% 35% 10%	4495
September	1st to 10th	Day	44% 7% 13% 25% 11% 1	2400
	11th to 20th	Day	38% 8% 12% 30% 13%	2322
	21st to end	Day	51% 6% 11% 24% 9%	2135
October	1st to 10th	Day	50% 4 12% 25% 9% 1	3190
	11th to 20th	Day	55% 6% 11% 21% 8%	3140
	21st to end	Day	64% 4 11% 16% 5%	3428
November	1st to 10th	Day	56% 8% 13% 18% 6%	1604
	11th to 20th	Day	64% 8% 9% 12% 6% 1	1600
	21st to end	Day	74% 6% 9% 8% 3	1600
December	1st to 10th	Day	77% 3 9% 8% 2	2600
	11th to 20th	Day	74% 3 5% 12% 6%	2986
	21st to end	Day	75% 3 4 12% 7%	3960
January	1st to 10th	Night	71% 4 6% 13% 5%	6349
	11th to 20th	Night	76% 6% 5% 5% 6% 1	6245
	21st to end	Night	74% 5% 5% 7% 9% 1	6490
February	1st to 10th	Night	67% 5% 9% 12% 5% 1	2600
	11th to 20th	Night	64% 4 8% 16% 7%	2535
	21st to end	Night	66% 4 8% 15% 6% 1	2124
March	1st to 10th	Night	58% 4 9% 11% 12% 5%	4925
	11th to 20th	Night	55% 6% 15% 16% 8% 1	4980
	21st to end	Night	55% 5% 8% 18% 12% 2	5467
April	1st to 10th	Night	57% 5% 9% 17% 11% 2	2007
	11th to 20th	Night	50% 5% 7% 22% 14% 1	1907
	21st to end	Night	54% 6% 9% 16% 14% 2	1800
May	1st to 10th	Night	48% 7% 9% 20% 12% 4	3883
	11th to 20th	Night	38% 7% 13% 22% 18% 2	3576
	21st to end	Night	47% 6% 10% 23% 13% 1	3927
June	1st to 10th	Night	47% 8% 11% 19% 14% 2	1600
	11th to 20th	Night	38% 5% 14% 25% 17%	1442
	21st to end	Night	44% 8% 14% 22% 11% 1	1400
July	1st to 10th	Night	44% 3 13% 27% 11% 1	3125
	11th to 20th	Night	40% 3 10% 34% 13%	3543
	21st to end	Night	33% 4 9% 39% 14% 1	3977
August	1st to 10th	Night	37% 4 16% 27% 15% 1	2904
	11th to 20th	Night	43% 6% 17% 23% 10% 1	2902
	21st to end	Night	37% 4 12% 34% 12% 1	3369
September	1st to 10th	Night	37% 8% 17% 25% 12% 1	2000
	11th to 20th	Night	35% 7% 14% 30% 14%	2075
	21st to end	Night	45% 5% 12% 26% 11%	2265
October	1st to 10th	Night	41% 4 8% 28% 17%	3837
	11th to 20th	Night	52% 5% 14% 21% 9%	3779
	21st to end	Night	61% 4 15% 15% 6%	4120
November	1st to 10th	Night	56% 6% 12% 19% 7%	2693
	11th to 20th	Night	59% 7% 11% 15% 7% 1	2800
	21st to end	Night	70% 6% 9% 11% 3	2800
December	1st to 10th	Night	78% 4 9% 7% 2	4580
	11th to 20th	Night	76% 4 5% 8% 6%	5208
	21st to end	Night	75% 3 5% 9% 7%	6996

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	19% 26% 35% 15% 5% 1	200
	11th to 20th	Day	29% 17% 36% 13% 4 1	224
	21st to end	Day	29% 16% 34% 15% 6%	330
February	1st to 10th	Day	28% 29% 33% 7% 3 1	300
	11th to 20th	Day	29% 26% 37% 6% 1	300
	21st to end	Day	34% 24% 34% 8%	269
March	1st to 10th	Day	25% 22% 34% 17% 1 1	500
	11th to 20th	Day	23% 23% 35% 14% 5% 1	500
	21st to end	Day	32% 15% 31% 17% 4 1	550
April	1st to 10th	Day	27% 22% 29% 15% 6% 1	500
	11th to 20th	Day	36% 19% 20% 13% 9% 3	492
	21st to end	Day	33% 14% 31% 14% 6% 2	500
May	1st to 10th	Day	26% 14% 30% 21% 6% 3	503
	11th to 20th	Day	22% 15% 32% 19% 10% 2	527
	21st to end	Day	23% 15% 31% 19% 10% 3	573
June	1st to 10th	Day	23% 13% 35% 24% 4 1	530
	11th to 20th	Day	17% 14% 31% 26% 11% 2	681
	21st to end	Day	23% 12% 35% 20% 8% 2	730
July	1st to 10th	Day	13% 10% 32% 32% 11% 2	721
	11th to 20th	Day	17% 10% 27% 29% 13% 4	529
	21st to end	Day	13% 10% 34% 27% 11% 5%	576
August	1st to 10th	Day	16% 8% 25% 30% 16% 6%	526
	11th to 20th	Day	18% 5% 24% 31% 15% 7%	519
	21st to end	Day	18% 9% 29% 25% 15% 6%	583
September	1st to 10th	Day	19% 12% 26% 24% 13% 6%	530
	11th to 20th	Day	14% 9% 22% 23% 20% 11%	530
	21st to end	Day	23% 11% 26% 24% 12% 3	530
October	1st to 10th	Day	25% 14% 26% 17% 13% 4	502
	11th to 20th	Day	30% 17% 31% 16% 4 1	490
	21st to end	Day	38% 15% 28% 15% 3	539
November	1st to 10th	Day	33% 19% 30% 15% 3	233
	11th to 20th	Day	34% 19% 34% 9% 5%	200
	21st to end	Day	34% 23% 33% 9% 2	200
December	1st to 10th	Day	33% 17% 36% 12% 3 1	200
	11th to 20th	Day	37% 27% 21% 13% 2 1	200
	21st to end	Day	29% 25% 29% 12% 3 2	220
January	1st to 10th	Night	28% 17% 33% 18% 4	800
	11th to 20th	Night	29% 17% 32% 18% 4 1	800
	21st to end	Night	20% 14% 35% 22% 8% 1	880
February	1st to 10th	Night	23% 21% 34% 20% 3	800
	11th to 20th	Night	23% 18% 34% 19% 4	783
	21st to end	Night	26% 21% 28% 21% 4	660
March	1st to 10th	Night	23% 19% 34% 21% 4	800
	11th to 20th	Night	20% 19% 34% 21% 4 1	800
	21st to end	Night	22% 14% 32% 24% 8%	880
April	1st to 10th	Night	28% 14% 31% 22% 5%	800
	11th to 20th	Night	25% 14% 29% 23% 9% 1	723
	21st to end	Night	26% 10% 29% 25% 10%	600
May	1st to 10th	Night	24% 6% 27% 32% 10% 1	527
	11th to 20th	Night	20% 8% 32% 31% 9%	394
	21st to end	Night	14% 8% 33% 35% 10%	433
June	1st to 10th	Night	20% 8% 30% 33% 9% 1	400
	11th to 20th	Night	18% 9% 25% 37% 12%	400
	21st to end	Night	21% 6% 23% 37% 13% 1	400
July	1st to 10th	Night	12% 5% 23% 43% 17% 1	390
	11th to 20th	Night	15% 5% 24% 37% 19%	388
	21st to end	Night	11% 4 23% 42% 19% 1	508
August	1st to 10th	Night	14% 3 18% 37% 26% 2	597
	11th to 20th	Night	15% 5% 16% 38% 24% 3	594
	21st to end	Night	18% 7% 25% 29% 20% 2	741
September	1st to 10th	Night	16% 6% 26% 31% 18% 3	800
	11th to 20th	Night	16% 6% 23% 27% 24% 4	800
	21st to end	Night	23% 8% 21% 28% 18% 2	800
October	1st to 10th	Night	23% 10% 28% 24% 14% 1	773
	11th to 20th	Night	30% 13% 29% 19% 8% 1	760
	21st to end	Night	35% 13% 31% 17% 4	836
November	1st to 10th	Night	31% 13% 26% 23% 7% 1	780
	11th to 20th	Night	28% 17% 31% 17% 6%	800
	21st to end	Night	35% 16% 27% 18% 5%	800
December	1st to 10th	Night	33% 18% 30% 15% 4	800
	11th to 20th	Night	27% 20% 35% 14% 3 1	800
	21st to end	Night	34% 17% 28% 18% 3	880

Page generated at 2025-10-01 01:39:07. Version ac07

Copyright © 2025 Attilla Danko.