Bracebridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bracebridge 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	17% 12% 4 9% 5% 4 4 3 5% 6% 31%	127688
	Night	17% 13% 5% 10% 5% 4 4 3 4 6% 29%	121688
Transparency	Day	52% 6% 11% 20% 10% 1	131268
	Night	55% 6% 11% 18% 10% 1	126197
Seeing	Day	25% 13% 31% 20% 9% 3	16067
	Night	24% 11% 29% 25% 10% 1	24760

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% 17% 9% 11% 5% 5% 4 3 4 5% 25%	3597
	11th to 20th	Day	10% 21% 9% 17% 9% 7% 5% 3 4 3 12%	3733
	21st to end	Day	13% 19% 8% 16% 6% 6% 5% 3 4 4 16%	4466
February	1st to 10th	Day	12% 21% 7% 16% 7% 6% 4 2 4 3 19%	1800
	11th to 20th	Day	14% 16% 6% 13% 7% 5% 4 3 4 5% 23%	1753
	21st to end	Day	17% 19% 6% 12% 6% 5% 5% 2 4 4 19%	1505
March	1st to 10th	Day	18% 15% 5% 10% 6% 4 3 3 4 5% 27%	4932
	11th to 20th	Day	12% 16% 6% 9% 5% 5% 5% 4 6% 7% 25%	4980
	21st to end	Day	19% 16% 5% 7% 4 3 3 3 3 4 33%	5465
April	1st to 10th	Day	20% 14% 3 8% 5% 4 4 3 4 6% 29%	2380
	11th to 20th	Day	22% 11% 3 6% 5% 4 4 3 4 5% 34%	2471
	21st to end	Day	23% 11% 4 6% 4 4 3 3 4 5% 33%	2600
May	1st to 10th	Day	20% 9% 2 8% 4 4 5% 3 5% 6% 33%	6014
	11th to 20th	Day	16% 9% 3 7% 4 4 4 4 5% 7% 37%	6318
	21st to end	Day	22% 9% 3 6% 4 5% 4 3 4 6% 34%	6949
June	1st to 10th	Day	19% 9% 3 7% 5% 4 4 4 6% 7% 34%	2800
	11th to 20th	Day	15% 6% 3 6% 5% 5% 5% 5% 7% 8% 36%	2964
	21st to end	Day	19% 7% 2 6% 5% 4 4 4 5% 7% 35%	3000
July	1st to 10th	Day	15% 6% 3 6% 4 5% 5% 4 6% 9% 37%	6819
	11th to 20th	Day	13% 5% 2 6% 4 4 4 3 5% 7% 47%	6406
	21st to end	Day	9% 5% 2 6% 4 4 4 4 6% 8% 49%	6682
August	1st to 10th	Day	14% 7% 3 7% 5% 4 5% 4 6% 8% 36%	4234
	11th to 20th	Day	17% 7% 3 6% 4 4 5% 5% 7% 9% 34%	4174
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 4 6% 9% 44%	4516
September	1st to 10th	Day	15% 7% 2 7% 4 4 6% 3 6% 7% 39%	2400
	11th to 20th	Day	14% 6% 2 5% 4 4 4 4 5% 7% 45%	2303
	21st to end	Day	19% 9% 3 7% 4 4 4 3 4 6% 35%	2148
October	1st to 10th	Day	22% 7% 2 7% 5% 4 4 4 4 6% 34%	1930
	11th to 20th	Day	26% 10% 4 9% 6% 4 5% 3 4 7% 23%	1900
	21st to end	Day	31% 11% 4 9% 5% 4 3 3 4 5% 22%	2090
November	1st to 10th	Day	20% 14% 3 8% 5% 4 5% 3 5% 6% 27%	1613
	11th to 20th	Day	18% 17% 5% 10% 6% 4 5% 4 5% 5% 22%	1600
	21st to end	Day	20% 23% 5% 10% 6% 4 4 4 5% 4 16%	1600
December	1st to 10th	Day	18% 28% 6% 11% 4 4 4 3 4 5% 13%	2600
	11th to 20th	Day	19% 23% 6% 15% 5% 4 3 2 2 3 18%	2986
	21st to end	Day	23% 21% 6% 14% 5% 4 3 2 3 4 17%	3960
January	1st to 10th	Night	14% 19% 9% 13% 6% 5% 4 3 4 5% 18%	6349
	11th to 20th	Night	12% 18% 8% 21% 8% 6% 5% 3 4 4 12%	6150
	21st to end	Night	13% 19% 9% 14% 6% 7% 5% 3 4 4 17%	6490
February	1st to 10th	Night	12% 19% 7% 14% 8% 6% 4 3 4 5% 19%	2600
	11th to 20th	Night	13% 16% 7% 12% 7% 5% 4 3 4 4 24%	2533
	21st to end	Night	15% 17% 5% 11% 7% 6% 4 4 4 4 22%	2124
March	1st to 10th	Night	17% 14% 4 11% 5% 4 4 3 5% 5% 29%	4908
	11th to 20th	Night	10% 14% 7% 9% 6% 5% 5% 4 5% 7% 27%	4979
	21st to end	Night	22% 11% 5% 7% 5% 4 4 4 4 5% 31%	5467
April	1st to 10th	Night	21% 14% 4 7% 5% 3 4 3 4 6% 28%	2020
	11th to 20th	Night	20% 10% 3 7% 4 4 4 3 5% 5% 35%	1896
	21st to end	Night	20% 10% 3 8% 6% 5% 4 4 4 6% 31%	1800
May	1st to 10th	Night	20% 7% 3 6% 4 5% 5% 3 5% 8% 34%	3925
	11th to 20th	Night	14% 7% 2 5% 4 4 4 4 6% 8% 42%	3575
	21st to end	Night	19% 8% 2 6% 5% 4 4 4 4 8% 36%	3926
June	1st to 10th	Night	16% 9% 3 6% 5% 4 4 4 6% 7% 37%	1600
	11th to 20th	Night	13% 7% 2 6% 4 4 3 5% 6% 9% 41%	1430
	21st to end	Night	16% 8% 3 6% 5% 4 4 5% 5% 8% 37%	1400
July	1st to 10th	Night	14% 7% 2 6% 5% 5% 4 4 6% 7% 40%	3160
	11th to 20th	Night	15% 5% 2 5% 3 4 4 3 5% 6% 47%	3551
	21st to end	Night	11% 6% 2 5% 3 3 4 3 5% 7% 51%	4153
August	1st to 10th	Night	11% 6% 2 5% 4 4 4 4 7% 7% 46%	2915
	11th to 20th	Night	16% 7% 3 6% 4 4 4 3 4 6% 44%	2875
	21st to end	Night	15% 5% 2 5% 4 4 4 3 5% 7% 48%	3347
September	1st to 10th	Night	12% 6% 2 6% 4 3 3 4 6% 8% 45%	2000
	11th to 20th	Night	13% 5% 2 4 4 4 3 4 4 7% 51%	2094
	21st to end	Night	18% 7% 3 6% 4 3 4 3 5% 6% 41%	2251
October	1st to 10th	Night	18% 8% 2 7% 5% 4 5% 3 5% 6% 37%	2317
	11th to 20th	Night	24% 11% 3 8% 5% 4 4 3 5% 5% 27%	2280
	21st to end	Night	26% 14% 4 9% 5% 4 3 3 3 5% 24%	2508
November	1st to 10th	Night	21% 13% 3 7% 4 4 4 3 4 6% 31%	2681
	11th to 20th	Night	18% 17% 5% 8% 5% 4 4 3 5% 6% 25%	2800
	21st to end	Night	23% 19% 6% 9% 5% 4 4 4 4 5% 16%	2800
December	1st to 10th	Night	21% 25% 6% 12% 5% 4 3 2 4 5% 14%	4580
	11th to 20th	Night	17% 23% 8% 17% 5% 4 4 2 3 4 12%	5208
	21st to end	Night	23% 21% 6% 14% 6% 4 3 2 3 4 14%	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	62% 4 7% 18% 8%	3598
	11th to 20th	Day	76% 5% 6% 7% 5%	3764
	21st to end	Day	73% 4 7% 8% 7% 1	4466
February	1st to 10th	Day	72% 4 7% 12% 5% 1	1800
	11th to 20th	Day	64% 5% 9% 12% 8% 1	1762
	21st to end	Day	69% 4 7% 14% 7%	1505
March	1st to 10th	Day	60% 5% 12% 8% 14% 1	4935
	11th to 20th	Day	58% 6% 13% 16% 7% 2	4980
	21st to end	Day	54% 4 8% 19% 13% 2	5465
April	1st to 10th	Day	56% 5% 9% 19% 10% 1	2380
	11th to 20th	Day	53% 5% 7% 21% 13% 1	2471
	21st to end	Day	55% 5% 8% 19% 12% 3	2600
May	1st to 10th	Day	49% 7% 10% 19% 9% 6%	6023
	11th to 20th	Day	45% 7% 11% 19% 17% 1	6322
	21st to end	Day	51% 5% 11% 18% 12% 3	6949
June	1st to 10th	Day	49% 7% 9% 22% 13%	2800
	11th to 20th	Day	42% 8% 11% 24% 13% 2	2964
	21st to end	Day	47% 7% 13% 21% 11% 1	3000
July	1st to 10th	Day	42% 7% 15% 26% 10% 1	6746
	11th to 20th	Day	36% 6% 12% 31% 14%	6330
	21st to end	Day	33% 6% 13% 34% 14%	6490
August	1st to 10th	Day	44% 7% 14% 24% 10% 1	4221
	11th to 20th	Day	44% 8% 15% 25% 8%	4213
	21st to end	Day	35% 7% 13% 35% 10% 1	4516
September	1st to 10th	Day	43% 7% 14% 25% 10% 1	2400
	11th to 20th	Day	37% 7% 13% 30% 12% 1	2303
	21st to end	Day	50% 6% 11% 24% 9%	2148
October	1st to 10th	Day	46% 5% 13% 25% 10% 1	3190
	11th to 20th	Day	52% 7% 12% 21% 8%	3140
	21st to end	Day	60% 6% 12% 17% 5%	3428
November	1st to 10th	Day	56% 7% 12% 19% 5%	1613
	11th to 20th	Day	62% 8% 10% 13% 5% 1	1600
	21st to end	Day	71% 5% 11% 10% 3	1600
December	1st to 10th	Day	73% 5% 11% 9% 2	2600
	11th to 20th	Day	73% 4 6% 12% 4	2986
	21st to end	Day	75% 4 4 11% 7%	3960
January	1st to 10th	Night	68% 4 7% 13% 7%	6349
	11th to 20th	Night	75% 6% 7% 6% 5% 1	6194
	21st to end	Night	70% 6% 7% 8% 8% 1	6490
February	1st to 10th	Night	68% 5% 9% 13% 5% 1	2600
	11th to 20th	Night	63% 6% 9% 15% 7% 1	2535
	21st to end	Night	64% 5% 9% 15% 7%	2124
March	1st to 10th	Night	57% 4 11% 12% 12% 4	4918
	11th to 20th	Night	55% 7% 16% 15% 7% 1	4980
	21st to end	Night	53% 6% 8% 19% 13% 2	5467
April	1st to 10th	Night	57% 4 9% 17% 10% 2	2020
	11th to 20th	Night	50% 6% 7% 22% 15% 1	1896
	21st to end	Night	54% 6% 8% 15% 15% 2	1800
May	1st to 10th	Night	47% 6% 12% 18% 13% 4	3932
	11th to 20th	Night	39% 7% 13% 21% 18% 1	3576
	21st to end	Night	46% 7% 9% 23% 13% 1	3927
June	1st to 10th	Night	45% 8% 10% 21% 15% 2	1600
	11th to 20th	Night	38% 6% 13% 24% 18% 1	1430
	21st to end	Night	45% 6% 14% 23% 11% 1	1400
July	1st to 10th	Night	42% 6% 13% 25% 12% 2	3125
	11th to 20th	Night	37% 5% 11% 32% 14%	3505
	21st to end	Night	33% 5% 9% 38% 15% 1	4030
August	1st to 10th	Night	35% 6% 16% 26% 16% 1	2904
	11th to 20th	Night	41% 6% 17% 24% 12% 1	2902
	21st to end	Night	35% 6% 13% 34% 11% 1	3347
September	1st to 10th	Night	37% 7% 17% 27% 12% 1	2000
	11th to 20th	Night	33% 6% 15% 32% 13%	2094
	21st to end	Night	44% 6% 12% 27% 12%	2251
October	1st to 10th	Night	39% 5% 11% 27% 18%	3837
	11th to 20th	Night	50% 5% 15% 21% 8%	3779
	21st to end	Night	56% 5% 15% 17% 6%	4120
November	1st to 10th	Night	54% 6% 11% 21% 7%	2681
	11th to 20th	Night	59% 7% 12% 15% 7% 1	2800
	21st to end	Night	68% 7% 11% 11% 3	2800
December	1st to 10th	Night	74% 5% 11% 8% 2	4580
	11th to 20th	Night	76% 5% 7% 8% 4	5208
	21st to end	Night	76% 4 6% 9% 6%	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	24% 21% 38% 12% 6% 1	200
	11th to 20th	Day	24% 20% 39% 11% 4 1	237
	21st to end	Day	28% 15% 37% 15% 4	330
February	1st to 10th	Day	32% 26% 32% 7% 3	300
	11th to 20th	Day	29% 24% 39% 7% 2	300
	21st to end	Day	39% 23% 31% 7%	259
March	1st to 10th	Day	27% 17% 39% 13% 3	500
	11th to 20th	Day	25% 19% 35% 16% 4 1	500
	21st to end	Day	36% 13% 31% 15% 6%	550
April	1st to 10th	Day	29% 19% 30% 15% 6% 1	500
	11th to 20th	Day	38% 15% 22% 14% 8% 2	492
	21st to end	Day	35% 14% 31% 12% 7% 1	500
May	1st to 10th	Day	28% 12% 32% 19% 6% 3	503
	11th to 20th	Day	22% 15% 31% 20% 10% 3	527
	21st to end	Day	24% 13% 30% 20% 11% 2	573
June	1st to 10th	Day	25% 12% 32% 24% 5% 2	530
	11th to 20th	Day	19% 14% 29% 25% 11% 2	694
	21st to end	Day	23% 10% 37% 21% 7% 2	730
July	1st to 10th	Day	14% 8% 33% 29% 12% 3	721
	11th to 20th	Day	18% 8% 28% 28% 13% 5%	543
	21st to end	Day	13% 10% 34% 27% 11% 5%	576
August	1st to 10th	Day	16% 5% 27% 31% 14% 6%	526
	11th to 20th	Day	17% 4 26% 29% 16% 7%	519
	21st to end	Day	17% 8% 31% 25% 14% 6%	583
September	1st to 10th	Day	18% 9% 28% 22% 15% 7%	530
	11th to 20th	Day	14% 6% 25% 25% 19% 11%	530
	21st to end	Day	23% 11% 25% 26% 13% 2	530
October	1st to 10th	Day	27% 11% 25% 18% 14% 4	502
	11th to 20th	Day	30% 13% 33% 17% 5% 2	490
	21st to end	Day	39% 16% 29% 14% 3	539
November	1st to 10th	Day	36% 16% 31% 15% 3	233
	11th to 20th	Day	31% 22% 31% 12% 5%	200
	21st to end	Day	37% 19% 33% 12% 1	200
December	1st to 10th	Day	35% 14% 34% 15% 2 1	200
	11th to 20th	Day	38% 23% 22% 14% 3 1	200
	21st to end	Day	39% 19% 28% 10% 3 1	220
January	1st to 10th	Night	30% 16% 31% 18% 5%	800
	11th to 20th	Night	31% 16% 29% 18% 5% 1	800
	21st to end	Night	22% 11% 36% 23% 7% 1	880
February	1st to 10th	Night	24% 20% 35% 19% 3	800
	11th to 20th	Night	23% 18% 34% 19% 6%	783
	21st to end	Night	27% 18% 30% 20% 4	660
March	1st to 10th	Night	23% 17% 36% 21% 3	800
	11th to 20th	Night	23% 16% 35% 21% 4 1	800
	21st to end	Night	24% 13% 30% 25% 8%	880
April	1st to 10th	Night	30% 14% 31% 21% 5%	800
	11th to 20th	Night	27% 13% 29% 21% 9% 1	712
	21st to end	Night	26% 10% 30% 25% 9% 1	600
May	1st to 10th	Night	23% 4 28% 32% 11% 1	550
	11th to 20th	Night	19% 9% 31% 29% 12%	394
	21st to end	Night	15% 6% 32% 34% 13%	433
June	1st to 10th	Night	22% 6% 29% 33% 10% 1	400
	11th to 20th	Night	17% 9% 25% 38% 11%	400
	21st to end	Night	19% 5% 24% 39% 13% 1	400
July	1st to 10th	Night	12% 3 21% 47% 16% 1	390
	11th to 20th	Night	16% 3 23% 37% 19% 1	388
	21st to end	Night	12% 4 23% 40% 20% 1	538
August	1st to 10th	Night	13% 3 17% 39% 27% 2	597
	11th to 20th	Night	14% 3 17% 38% 25% 3	594
	21st to end	Night	17% 5% 25% 29% 22% 2	732
September	1st to 10th	Night	16% 6% 26% 31% 18% 3	800
	11th to 20th	Night	16% 4 23% 31% 23% 4	800
	21st to end	Night	22% 7% 20% 33% 16% 3	800
October	1st to 10th	Night	21% 10% 27% 28% 13% 1	773
	11th to 20th	Night	30% 11% 29% 20% 9% 1	760
	21st to end	Night	33% 14% 29% 20% 4	836
November	1st to 10th	Night	31% 11% 26% 25% 6% 1	780
	11th to 20th	Night	28% 17% 29% 19% 6% 1	800
	21st to end	Night	35% 13% 27% 20% 4 1	800
December	1st to 10th	Night	35% 17% 30% 14% 5%	800
	11th to 20th	Night	30% 17% 34% 15% 3 1	800
	21st to end	Night	35% 13% 30% 18% 4	880

Page generated at 2025-10-01 01:39:04. Version ac07

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