South Bruce Peninsula
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the South Bruce Peninsula clear sky chart from 2005-11-06 to 2026-07-01.

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	15% 12% 4 9% 5% 4 4 3 5% 6% 32%	137779
	Night	16% 14% 5% 11% 6% 5% 4 3 4 5% 26%	134661
Transparency	Day	52% 5% 11% 20% 10% 1	141313
	Night	58% 5% 10% 16% 9% 1	139203
Seeing	Day	20% 12% 27% 26% 13% 3	17305
	Night	22% 11% 27% 26% 12% 2	26521

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	13% 21% 11% 18% 10% 4 4 2 3 4 10%	4131
	11th to 20th	Day	10% 23% 12% 29% 10% 4 3 2 2 2 3	4775
	21st to end	Day	11% 16% 10% 21% 10% 8% 5% 3 3 3 9%	5780
February	1st to 10th	Day	13% 20% 7% 20% 9% 5% 4 3 3 4 12%	1890
	11th to 20th	Day	13% 16% 8% 15% 9% 6% 5% 4 4 5% 16%	1843
	21st to end	Day	14% 18% 6% 14% 6% 6% 5% 4 5% 4 18%	1688
March	1st to 10th	Day	16% 12% 5% 11% 5% 5% 4 3 5% 5% 28%	4894
	11th to 20th	Day	13% 16% 7% 11% 5% 5% 5% 4 5% 6% 24%	5090
	21st to end	Day	19% 15% 5% 10% 4 3 4 3 4 5% 27%	5586
April	1st to 10th	Day	19% 12% 4 8% 5% 4 4 3 4 7% 30%	2423
	11th to 20th	Day	20% 10% 3 6% 4 3 3 3 4 6% 38%	2702
	21st to end	Day	20% 9% 3 7% 4 3 4 3 5% 7% 35%	2730
May	1st to 10th	Day	15% 7% 2 6% 4 4 4 4 6% 8% 40%	7642
	11th to 20th	Day	15% 9% 3 7% 4 4 4 4 5% 7% 39%	7957
	21st to end	Day	18% 8% 2 5% 3 3 3 3 4 7% 44%	9060
June	1st to 10th	Day	14% 8% 2 5% 4 5% 5% 5% 6% 8% 40%	3103
	11th to 20th	Day	12% 5% 2 5% 5% 4 5% 4 6% 9% 42%	3150
	21st to end	Day	15% 6% 2 5% 4 3 5% 4 6% 7% 41%	3150
July	1st to 10th	Day	14% 8% 2 6% 4 4 4 4 6% 8% 40%	6820
	11th to 20th	Day	12% 5% 2 5% 3 3 3 3 5% 7% 52%	6691
	21st to end	Day	8% 6% 2 5% 3 3 4 4 5% 8% 53%	6425
August	1st to 10th	Day	12% 5% 2 5% 4 5% 4 4 7% 9% 44%	4234
	11th to 20th	Day	16% 6% 2 5% 3 4 4 3 6% 8% 42%	4174
	21st to end	Day	10% 5% 2 5% 5% 4 4 3 6% 9% 47%	4649
September	1st to 10th	Day	13% 6% 3 7% 4 5% 4 4 5% 8% 41%	2371
	11th to 20th	Day	12% 5% 2 5% 4 4 4 3 6% 9% 45%	2200
	21st to end	Day	18% 8% 3 7% 5% 5% 5% 4 5% 5% 36%	2200
October	1st to 10th	Day	19% 8% 3 8% 4 4 4 3 4 6% 36%	2030
	11th to 20th	Day	24% 14% 3 10% 5% 4 5% 3 5% 5% 22%	2000
	21st to end	Day	28% 14% 5% 10% 5% 5% 3 3 4 5% 19%	2117
November	1st to 10th	Day	20% 18% 4 9% 5% 4 4 4 5% 6% 21%	1807
	11th to 20th	Day	17% 23% 6% 9% 5% 5% 5% 4 4 5% 17%	1680
	21st to end	Day	21% 28% 6% 10% 5% 5% 4 3 4 4 10%	1680
December	1st to 10th	Day	16% 32% 9% 11% 5% 4 4 3 4 4 7%	2680
	11th to 20th	Day	21% 24% 7% 16% 5% 4 3 3 3 4 10%	2874
	21st to end	Day	28% 22% 5% 14% 5% 5% 3 2 3 3 9%	3553
January	1st to 10th	Night	13% 21% 12% 21% 7% 4 3 3 3 3 11%	8789
	11th to 20th	Night	11% 24% 11% 22% 9% 5% 4 3 3 3 6%	8118
	21st to end	Night	11% 17% 9% 19% 11% 8% 4 3 3 3 12%	8401
February	1st to 10th	Night	13% 20% 6% 16% 9% 6% 5% 4 5% 4 14%	2730
	11th to 20th	Night	14% 15% 7% 16% 8% 5% 4 3 4 5% 19%	2663
	21st to end	Night	15% 15% 6% 12% 6% 5% 5% 3 5% 6% 21%	2116
March	1st to 10th	Night	15% 12% 5% 10% 5% 4 4 3 5% 7% 30%	5165
	11th to 20th	Night	11% 14% 5% 9% 6% 4 5% 4 5% 7% 31%	5089
	21st to end	Night	21% 12% 5% 9% 4 4 4 3 4 5% 29%	5588
April	1st to 10th	Night	20% 10% 3 8% 6% 4 4 3 5% 6% 31%	2210
	11th to 20th	Night	19% 9% 3 7% 4 3 4 3 5% 6% 36%	1872
	21st to end	Night	20% 9% 3 8% 5% 4 4 4 5% 5% 33%	1890
May	1st to 10th	Night	15% 7% 3 8% 5% 4 4 3 6% 7% 38%	5257
	11th to 20th	Night	17% 7% 3 7% 4 3 4 3 5% 6% 41%	4901
	21st to end	Night	18% 6% 2 6% 3 3 4 3 5% 7% 43%	5114
June	1st to 10th	Night	14% 7% 2 7% 6% 5% 3 3 5% 7% 42%	1512
	11th to 20th	Night	12% 5% 2 6% 4 5% 5% 5% 7% 9% 41%	1470
	21st to end	Night	15% 6% 3 6% 4 4 4 4 7% 7% 40%	1470
July	1st to 10th	Night	14% 8% 4 6% 4 4 3 3 5% 8% 42%	3160
	11th to 20th	Night	12% 5% 2 5% 4 3 4 4 5% 7% 49%	3286
	21st to end	Night	9% 6% 2 5% 4 4 3 3 6% 8% 49%	4423
August	1st to 10th	Night	12% 7% 2 7% 4 4 3 4 5% 8% 44%	2915
	11th to 20th	Night	13% 6% 3 6% 4 5% 5% 4 6% 8% 41%	2875
	21st to end	Night	11% 6% 2 7% 4 4 4 4 5% 7% 46%	3223
September	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 7% 8% 46%	2017
	11th to 20th	Night	11% 5% 2 5% 4 4 4 4 5% 7% 49%	2200
	21st to end	Night	17% 7% 3 8% 5% 5% 5% 3 5% 6% 37%	2200
October	1st to 10th	Night	18% 7% 3 7% 5% 4 4 4 5% 7% 36%	2370
	11th to 20th	Night	25% 11% 4 9% 5% 4 4 3 5% 5% 24%	2400
	21st to end	Night	26% 13% 4 10% 5% 4 5% 3 3 6% 21%	2720
November	1st to 10th	Night	19% 18% 4 9% 5% 4 5% 3 4 5% 25%	2708
	11th to 20th	Night	18% 21% 5% 10% 5% 5% 5% 3 5% 6% 17%	2940
	21st to end	Night	24% 26% 6% 8% 5% 4 4 3 4 5% 12%	2940
December	1st to 10th	Night	17% 28% 8% 12% 6% 4 4 3 5% 5% 8%	4720
	11th to 20th	Night	16% 26% 9% 17% 6% 4 4 3 3 3 9%	5542
	21st to end	Night	23% 23% 7% 14% 6% 6% 3 2 3 3 8%	7667

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	78% 4 8% 6% 4	4132
	11th to 20th	Day	90% 2 4 3 1	4806
	21st to end	Day	81% 4 8% 5% 2	5780
February	1st to 10th	Day	77% 5% 7% 9% 2	1890
	11th to 20th	Day	70% 6% 11% 9% 3	1852
	21st to end	Day	68% 6% 9% 13% 4	1688
March	1st to 10th	Day	58% 5% 14% 13% 9% 1	4897
	11th to 20th	Day	59% 6% 12% 16% 6% 1	5090
	21st to end	Day	58% 6% 11% 18% 7% 1	5586
April	1st to 10th	Day	56% 5% 11% 18% 10%	2423
	11th to 20th	Day	49% 4 8% 23% 15% 1	2702
	21st to end	Day	48% 6% 12% 20% 11% 2	2730
May	1st to 10th	Day	42% 6% 12% 23% 14% 3	7651
	11th to 20th	Day	44% 6% 11% 22% 17% 1	7961
	21st to end	Day	42% 4 10% 26% 15% 4	9061
June	1st to 10th	Day	41% 7% 10% 25% 16% 1	3103
	11th to 20th	Day	37% 7% 11% 26% 17% 1	3150
	21st to end	Day	41% 6% 12% 25% 14% 2	3150
July	1st to 10th	Day	41% 6% 15% 23% 14% 1	6747
	11th to 20th	Day	31% 5% 12% 36% 15% 1	6610
	21st to end	Day	29% 5% 13% 35% 16% 1	6241
August	1st to 10th	Day	36% 6% 15% 27% 14% 1	4221
	11th to 20th	Day	40% 6% 16% 26% 11%	4213
	21st to end	Day	34% 6% 15% 33% 11% 1	4649
September	1st to 10th	Day	41% 8% 12% 26% 12% 1	2371
	11th to 20th	Day	35% 6% 16% 30% 13%	2200
	21st to end	Day	50% 6% 12% 23% 9%	2200
October	1st to 10th	Day	42% 6% 14% 26% 12% 1	3303
	11th to 20th	Day	54% 5% 12% 21% 8%	3240
	21st to end	Day	61% 5% 12% 17% 5%	3393
November	1st to 10th	Day	63% 4 12% 15% 5%	1807
	11th to 20th	Day	67% 7% 13% 8% 5%	1680
	21st to end	Day	76% 6% 10% 7%	1680
December	1st to 10th	Day	79% 6% 11% 4 1	2680
	11th to 20th	Day	78% 4 11% 6% 1	2873
	21st to end	Day	82% 3 8% 5% 2	3553
January	1st to 10th	Night	78% 6% 6% 6% 4	8789
	11th to 20th	Night	84% 4 5% 5% 2	8162
	21st to end	Night	77% 4 8% 6% 5%	8401
February	1st to 10th	Night	73% 6% 7% 10% 3	2730
	11th to 20th	Night	68% 6% 10% 12% 4	2665
	21st to end	Night	64% 5% 13% 12% 6%	2116
March	1st to 10th	Night	54% 5% 14% 15% 11% 1	5175
	11th to 20th	Night	52% 6% 15% 18% 8% 1	5090
	21st to end	Night	57% 6% 7% 17% 11% 1	5588
April	1st to 10th	Night	54% 5% 9% 21% 10% 1	2210
	11th to 20th	Night	48% 5% 8% 21% 17% 1	1872
	21st to end	Night	52% 6% 9% 17% 15% 2	1890
May	1st to 10th	Night	45% 5% 8% 22% 15% 5%	5264
	11th to 20th	Night	43% 5% 9% 23% 18% 1	4902
	21st to end	Night	41% 4 8% 27% 18% 2	5115
June	1st to 10th	Night	41% 5% 10% 22% 19% 3	1512
	11th to 20th	Night	37% 6% 13% 25% 18% 1	1470
	21st to end	Night	41% 6% 11% 26% 13% 2	1470
July	1st to 10th	Night	41% 4 12% 24% 15% 4	3125
	11th to 20th	Night	34% 5% 11% 31% 18% 1	3244
	21st to end	Night	33% 5% 10% 32% 19% 1	4293
August	1st to 10th	Night	39% 5% 13% 27% 15% 1	2904
	11th to 20th	Night	41% 6% 18% 21% 13% 1	2902
	21st to end	Night	36% 6% 13% 31% 13% 1	3223
September	1st to 10th	Night	34% 8% 14% 29% 14% 2	2017
	11th to 20th	Night	34% 5% 16% 30% 15%	2200
	21st to end	Night	48% 6% 13% 23% 10% 1	2200
October	1st to 10th	Night	38% 6% 11% 28% 17%	3877
	11th to 20th	Night	53% 4 14% 19% 9%	3899
	21st to end	Night	54% 7% 15% 19% 5%	4381
November	1st to 10th	Night	61% 6% 12% 16% 5%	2708
	11th to 20th	Night	66% 7% 14% 9% 4 1	2940
	21st to end	Night	73% 6% 13% 6% 1	2940
December	1st to 10th	Night	78% 6% 12% 3 1	4720
	11th to 20th	Night	78% 5% 10% 6% 1	5542
	21st to end	Night	83% 3 8% 4 1	7667

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% 20% 34% 16% 3 1	226
	11th to 20th	Day	22% 20% 37% 16% 5%	330
	21st to end	Day	27% 18% 29% 20% 6%	363
February	1st to 10th	Day	22% 25% 33% 16% 4	330
	11th to 20th	Day	26% 18% 35% 18% 2	330
	21st to end	Day	23% 26% 35% 15% 1	273
March	1st to 10th	Day	22% 17% 35% 19% 6% 1	465
	11th to 20th	Day	24% 16% 30% 24% 5% 1	540
	21st to end	Day	27% 14% 29% 23% 5% 1	594
April	1st to 10th	Day	24% 15% 31% 22% 9% 1	540
	11th to 20th	Day	28% 13% 28% 16% 11% 5%	532
	21st to end	Day	25% 12% 28% 25% 9% 1	540
May	1st to 10th	Day	19% 11% 31% 26% 11% 2	543
	11th to 20th	Day	16% 9% 26% 30% 16% 3	567
	21st to end	Day	15% 8% 26% 27% 19% 4	617
June	1st to 10th	Day	13% 7% 28% 34% 15% 2	733
	11th to 20th	Day	14% 9% 27% 32% 15% 3	780
	21st to end	Day	17% 6% 28% 32% 14% 3	780
July	1st to 10th	Day	10% 5% 24% 34% 25% 4	722
	11th to 20th	Day	11% 6% 24% 34% 19% 6%	718
	21st to end	Day	11% 6% 21% 38% 19% 6%	577
August	1st to 10th	Day	12% 5% 22% 32% 21% 8%	526
	11th to 20th	Day	14% 5% 15% 35% 22% 8%	519
	21st to end	Day	15% 7% 23% 30% 20% 6%	583
September	1st to 10th	Day	16% 7% 21% 33% 17% 6%	530
	11th to 20th	Day	10% 5% 20% 27% 26% 12%	530
	21st to end	Day	18% 11% 23% 25% 19% 5%	530
October	1st to 10th	Day	20% 12% 25% 24% 15% 4	530
	11th to 20th	Day	23% 18% 32% 22% 4 1	530
	21st to end	Day	31% 17% 29% 18% 4	500
November	1st to 10th	Day	33% 16% 27% 17% 6%	305
	11th to 20th	Day	29% 21% 30% 15% 3 1	220
	21st to end	Day	30% 24% 33% 12% 2	220
December	1st to 10th	Day	33% 19% 30% 15% 4	220
	11th to 20th	Day	32% 22% 29% 14% 4	220
	21st to end	Day	37% 18% 33% 10% 2	242
January	1st to 10th	Night	24% 18% 32% 20% 5% 1	1050
	11th to 20th	Night	29% 16% 30% 19% 5%	1010
	21st to end	Night	21% 12% 33% 25% 7% 1	924
February	1st to 10th	Night	21% 17% 36% 22% 5%	840
	11th to 20th	Night	19% 13% 35% 26% 6%	823
	21st to end	Night	22% 16% 35% 23% 4	692
March	1st to 10th	Night	20% 12% 37% 25% 7%	840
	11th to 20th	Night	20% 14% 34% 24% 7% 1	840
	21st to end	Night	22% 10% 30% 27% 10% 1	924
April	1st to 10th	Night	24% 13% 30% 27% 6% 1	840
	11th to 20th	Night	22% 10% 27% 27% 12% 2	628
	21st to end	Night	24% 8% 26% 28% 13% 1	630
May	1st to 10th	Night	16% 6% 23% 38% 15% 2	630
	11th to 20th	Night	18% 4 20% 38% 18% 1	509
	21st to end	Night	14% 3 23% 37% 20% 3	455
June	1st to 10th	Night	15% 7% 22% 37% 17% 2	420
	11th to 20th	Night	11% 6% 25% 38% 20%	420
	21st to end	Night	16% 4 21% 36% 23% 1	420
July	1st to 10th	Night	10% 4 15% 46% 23% 2	390
	11th to 20th	Night	11% 3 19% 35% 30% 3	436
	21st to end	Night	9% 3 18% 42% 28% 1	657
August	1st to 10th	Night	11% 3 16% 37% 31% 2	597
	11th to 20th	Night	10% 4 16% 34% 30% 6%	594
	21st to end	Night	13% 5% 21% 30% 28% 3	660
September	1st to 10th	Night	11% 7% 20% 34% 21% 6%	792
	11th to 20th	Night	12% 5% 18% 33% 26% 6%	800
	21st to end	Night	18% 8% 21% 28% 20% 6%	800
October	1st to 10th	Night	20% 9% 25% 29% 15% 2	800
	11th to 20th	Night	29% 15% 23% 25% 7% 2	800
	21st to end	Night	31% 14% 28% 22% 5% 1	880
November	1st to 10th	Night	31% 14% 27% 21% 8% 1	820
	11th to 20th	Night	28% 19% 28% 18% 8%	840
	21st to end	Night	37% 16% 28% 17% 3	840
December	1st to 10th	Night	32% 21% 30% 13% 4	840
	11th to 20th	Night	26% 20% 34% 15% 3	925
	21st to end	Night	34% 15% 33% 15% 3	1155

Page generated at 2026-06-28 02:10:43. Version ac07

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