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 2025-02-25.

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% 31%	108489
	Night	15% 15% 6% 11% 6% 5% 4 3 4 5% 26%	110232
Transparency	Day	53% 6% 12% 19% 10% 1	112066
	Night	59% 5% 11% 16% 8% 1	114806
Seeing	Day	19% 11% 27% 27% 13% 3	15461
	Night	21% 11% 27% 26% 12% 2	24861

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% 21% 13% 18% 12% 4 4 2 3 3 9%	3181
	11th to 20th	Day	10% 22% 12% 29% 9% 4 3 2 3 2 4	3659
	21st to end	Day	14% 18% 12% 22% 7% 7% 4 3 3 3 9%	4466
February	1st to 10th	Day	13% 21% 7% 20% 9% 5% 4 3 3 4 11%	1800
	11th to 20th	Day	13% 16% 8% 15% 8% 6% 5% 4 5% 5% 16%	1753
	21st to end	Day	14% 18% 6% 12% 5% 5% 5% 4 5% 5% 19%	1570
March	1st to 10th	Day	17% 15% 4 8% 5% 5% 4 3 4 5% 29%	3330
	11th to 20th	Day	12% 18% 7% 12% 5% 5% 4 4 4 5% 25%	3480
	21st to end	Day	15% 13% 5% 8% 5% 4 4 4 5% 6% 31%	3815
April	1st to 10th	Day	19% 12% 4 8% 5% 4 4 3 5% 7% 30%	2191
	11th to 20th	Day	20% 10% 3 7% 4 3 4 3 4 6% 38%	2442
	21st to end	Day	21% 9% 3 7% 3 3 4 3 5% 7% 35%	2470
May	1st to 10th	Day	17% 7% 2 6% 4 4 4 3 5% 7% 40%	4108
	11th to 20th	Day	15% 7% 2 6% 3 4 4 3 6% 8% 42%	4258
	21st to end	Day	15% 5% 2 5% 3 3 4 3 5% 8% 46%	4837
June	1st to 10th	Day	14% 8% 2 5% 4 5% 4 5% 6% 8% 40%	2807
	11th to 20th	Day	11% 5% 2 5% 5% 5% 5% 4 6% 9% 43%	2850
	21st to end	Day	16% 6% 2 5% 4 3 4 4 6% 7% 42%	2850
July	1st to 10th	Day	14% 7% 2 6% 5% 4 4 5% 6% 8% 39%	4760
	11th to 20th	Day	11% 5% 2 5% 4 3 4 4 6% 8% 49%	4673
	21st to end	Day	9% 6% 2 5% 3 3 4 4 5% 9% 50%	4467
August	1st to 10th	Day	12% 6% 2 5% 4 5% 4 4 7% 9% 43%	4104
	11th to 20th	Day	16% 6% 2 5% 3 4 4 3 6% 8% 42%	4044
	21st to end	Day	10% 5% 2 5% 5% 4 5% 3 6% 9% 47%	4507
September	1st to 10th	Day	13% 6% 3 7% 4 5% 4 4 5% 8% 41%	2253
	11th to 20th	Day	13% 5% 3 6% 4 4 4 3 6% 9% 43%	2090
	21st to end	Day	18% 8% 3 7% 5% 5% 5% 4 5% 6% 36%	2090
October	1st to 10th	Day	20% 8% 3 8% 4 4 4 3 4 6% 34%	1929
	11th to 20th	Day	24% 14% 3 10% 5% 4 5% 3 5% 5% 21%	1900
	21st to end	Day	29% 14% 5% 10% 5% 4 3 2 4 5% 18%	2011
November	1st to 10th	Day	19% 19% 4 9% 6% 4 4 4 5% 6% 21%	1719
	11th to 20th	Day	17% 22% 6% 9% 5% 5% 5% 4 4 5% 18%	1600
	21st to end	Day	21% 27% 6% 10% 5% 5% 4 3 4 4 10%	1600
December	1st to 10th	Day	16% 32% 9% 11% 6% 4 4 3 4 4 7%	2600
	11th to 20th	Day	21% 24% 7% 16% 5% 4 3 3 3 4 10%	2799
	21st to end	Day	28% 23% 5% 14% 5% 5% 3 2 3 3 9%	3476
January	1st to 10th	Night	13% 22% 11% 21% 7% 4 3 2 3 3 11%	6780
	11th to 20th	Night	12% 20% 11% 23% 9% 5% 4 3 3 3 7%	6226
	21st to end	Night	13% 19% 10% 17% 8% 8% 4 3 3 3 12%	6490
February	1st to 10th	Night	12% 20% 7% 16% 9% 6% 5% 4 5% 3 13%	2600
	11th to 20th	Night	14% 15% 7% 17% 8% 5% 4 3 4 5% 19%	2533
	21st to end	Night	15% 15% 6% 12% 6% 5% 5% 3 5% 6% 22%	1977
March	1st to 10th	Night	13% 13% 4 8% 5% 4 4 3 5% 6% 35%	3509
	11th to 20th	Night	11% 16% 5% 9% 6% 3 3 3 4 6% 33%	3479
	21st to end	Night	14% 11% 6% 10% 5% 4 4 4 5% 6% 31%	3817
April	1st to 10th	Night	21% 11% 3 7% 5% 4 4 3 5% 6% 31%	2000
	11th to 20th	Night	19% 9% 3 6% 4 3 4 3 5% 6% 37%	1692
	21st to end	Night	21% 9% 3 8% 5% 4 4 4 5% 5% 32%	1710
May	1st to 10th	Night	16% 6% 3 8% 5% 4 4 3 6% 7% 39%	2833
	11th to 20th	Night	14% 7% 2 7% 5% 4 4 4 5% 7% 40%	2633
	21st to end	Night	12% 6% 2 7% 3 4 4 3 5% 7% 47%	2738
June	1st to 10th	Night	14% 7% 3 7% 6% 5% 4 3 5% 6% 40%	1368
	11th to 20th	Night	11% 5% 2 6% 4 4 5% 5% 7% 9% 43%	1330
	21st to end	Night	15% 6% 2 6% 4 4 4 5% 7% 7% 40%	1330
July	1st to 10th	Night	12% 7% 4 6% 4 4 3 3 4 7% 46%	2210
	11th to 20th	Night	12% 5% 2 4 4 3 4 3 5% 6% 51%	2294
	21st to end	Night	8% 6% 2 5% 5% 4 4 4 6% 7% 49%	3082
August	1st to 10th	Night	12% 7% 2 7% 4 4 3 4 5% 8% 43%	2825
	11th to 20th	Night	13% 6% 3 6% 4 5% 5% 4 6% 8% 41%	2785
	21st to end	Night	11% 6% 2 6% 4 4 4 4 5% 7% 46%	3124
September	1st to 10th	Night	10% 5% 2 6% 4 4 4 4 7% 8% 46%	1916
	11th to 20th	Night	11% 5% 2 6% 4 4 4 4 5% 7% 48%	2090
	21st to end	Night	17% 7% 3 8% 5% 5% 5% 3 5% 6% 37%	2090
October	1st to 10th	Night	18% 8% 3 8% 5% 4 4 4 5% 6% 35%	2251
	11th to 20th	Night	25% 11% 4 9% 5% 4 4 4 5% 5% 23%	2280
	21st to end	Night	27% 13% 4 10% 5% 5% 5% 3 4 6% 20%	2584
November	1st to 10th	Night	19% 17% 4 9% 5% 4 5% 3 4 5% 25%	2576
	11th to 20th	Night	18% 20% 5% 10% 5% 5% 5% 3 5% 6% 17%	2800
	21st to end	Night	23% 25% 6% 8% 5% 4 4 3 4 5% 12%	2800
December	1st to 10th	Night	18% 27% 8% 12% 6% 4 4 3 5% 5% 8%	4580
	11th to 20th	Night	16% 27% 9% 17% 6% 4 4 3 3 3 9%	5398
	21st to end	Night	24% 23% 7% 14% 6% 6% 4 2 3 3 8%	7502

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	80% 5% 7% 4 4 1	3182
	11th to 20th	Day	88% 2 5% 3 1	3690
	21st to end	Day	82% 4 7% 5% 1	4466
February	1st to 10th	Day	78% 5% 7% 8% 1	1800
	11th to 20th	Day	70% 6% 11% 9% 4	1762
	21st to end	Day	67% 6% 10% 13% 4	1570
March	1st to 10th	Day	58% 5% 13% 15% 8% 1	3333
	11th to 20th	Day	59% 8% 11% 16% 6% 1	3480
	21st to end	Day	51% 7% 13% 19% 9% 1	3815
April	1st to 10th	Day	55% 5% 11% 18% 10%	2191
	11th to 20th	Day	48% 5% 7% 23% 16% 1	2442
	21st to end	Day	49% 6% 12% 19% 11% 3	2470
May	1st to 10th	Day	43% 7% 11% 21% 17% 2	4120
	11th to 20th	Day	40% 8% 15% 25% 12% 1	4262
	21st to end	Day	37% 5% 12% 22% 19% 6%	4837
June	1st to 10th	Day	41% 7% 11% 25% 15% 1	2807
	11th to 20th	Day	36% 7% 11% 26% 18% 1	2850
	21st to end	Day	41% 6% 12% 25% 14% 2	2850
July	1st to 10th	Day	42% 6% 16% 20% 15% 1	4686
	11th to 20th	Day	32% 6% 14% 36% 12% 1	4592
	21st to end	Day	31% 6% 12% 32% 18% 1	4325
August	1st to 10th	Day	37% 6% 15% 27% 14% 1	4091
	11th to 20th	Day	40% 6% 16% 26% 11%	4083
	21st to end	Day	34% 6% 15% 33% 11% 1	4507
September	1st to 10th	Day	41% 8% 12% 26% 13% 1	2253
	11th to 20th	Day	36% 6% 16% 28% 13%	2090
	21st to end	Day	49% 6% 12% 23% 9%	2090
October	1st to 10th	Day	43% 6% 14% 25% 12% 1	3202
	11th to 20th	Day	54% 5% 12% 21% 8%	3140
	21st to end	Day	61% 5% 12% 17% 4	3287
November	1st to 10th	Day	64% 4 12% 15% 5%	1719
	11th to 20th	Day	67% 7% 12% 8% 5%	1600
	21st to end	Day	76% 6% 11% 6%	1600
December	1st to 10th	Day	79% 6% 11% 4 1	2600
	11th to 20th	Day	78% 4 11% 6% 1	2798
	21st to end	Day	82% 3 7% 5% 2	3476
January	1st to 10th	Night	79% 6% 5% 6% 4	6780
	11th to 20th	Night	82% 4 6% 6% 3	6270
	21st to end	Night	77% 5% 10% 5% 3	6490
February	1st to 10th	Night	74% 7% 7% 10% 2	2600
	11th to 20th	Night	68% 6% 10% 12% 4	2535
	21st to end	Night	63% 5% 13% 12% 6%	1977
March	1st to 10th	Night	50% 7% 16% 19% 9% 1	3519
	11th to 20th	Night	51% 7% 13% 18% 9% 2	3480
	21st to end	Night	52% 8% 9% 21% 9% 1	3817
April	1st to 10th	Night	54% 5% 9% 21% 10% 1	2000
	11th to 20th	Night	47% 5% 8% 21% 18% 1	1692
	21st to end	Night	53% 6% 8% 16% 15% 2	1710
May	1st to 10th	Night	43% 6% 11% 19% 17% 3	2840
	11th to 20th	Night	42% 6% 10% 24% 16% 2	2634
	21st to end	Night	37% 5% 12% 23% 20% 3	2739
June	1st to 10th	Night	43% 5% 10% 22% 17% 3	1368
	11th to 20th	Night	36% 6% 13% 25% 19% 2	1330
	21st to end	Night	40% 6% 11% 27% 14% 2	1330
July	1st to 10th	Night	39% 4 13% 23% 16% 6%	2175
	11th to 20th	Night	33% 5% 11% 36% 14% 1	2252
	21st to end	Night	33% 6% 12% 26% 22% 2	2984
August	1st to 10th	Night	40% 5% 13% 26% 15% 1	2814
	11th to 20th	Night	40% 6% 18% 21% 14% 1	2812
	21st to end	Night	36% 6% 13% 31% 13% 1	3124
September	1st to 10th	Night	34% 8% 13% 29% 14% 2	1916
	11th to 20th	Night	35% 6% 16% 29% 15%	2090
	21st to end	Night	48% 6% 13% 23% 9%	2090
October	1st to 10th	Night	39% 6% 11% 27% 17%	3758
	11th to 20th	Night	53% 4 15% 19% 9%	3779
	21st to end	Night	55% 7% 15% 19% 4	4245
November	1st to 10th	Night	60% 5% 13% 17% 5%	2576
	11th to 20th	Night	66% 7% 14% 9% 3 1	2800
	21st to end	Night	73% 6% 14% 6% 1	2800
December	1st to 10th	Night	77% 6% 13% 3 1	4580
	11th to 20th	Night	78% 5% 10% 6% 1	5398
	21st to end	Night	83% 3 8% 4 1	7502

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% 20% 34% 18% 3 1	205
	11th to 20th	Day	19% 18% 39% 18% 6%	300
	21st to end	Day	27% 17% 29% 21% 6%	330
February	1st to 10th	Day	24% 24% 33% 16% 3	300
	11th to 20th	Day	25% 18% 36% 18% 2	300
	21st to end	Day	21% 28% 35% 15% 1	237
March	1st to 10th	Day	21% 14% 35% 22% 7% 1	392
	11th to 20th	Day	20% 15% 32% 26% 6% 1	460
	21st to end	Day	23% 13% 30% 26% 6% 2	506
April	1st to 10th	Day	21% 13% 32% 24% 10%	460
	11th to 20th	Day	26% 13% 29% 17% 10% 5%	452
	21st to end	Day	25% 10% 27% 26% 10% 1	460
May	1st to 10th	Day	20% 8% 27% 30% 13% 2	463
	11th to 20th	Day	16% 7% 24% 32% 17% 3	487
	21st to end	Day	12% 7% 24% 30% 22% 5%	529
June	1st to 10th	Day	13% 6% 27% 35% 16% 3	637
	11th to 20th	Day	12% 7% 26% 35% 17% 4	680
	21st to end	Day	17% 5% 26% 33% 15% 3	680
July	1st to 10th	Day	10% 4 22% 34% 25% 4	671
	11th to 20th	Day	11% 6% 23% 34% 19% 6%	668
	21st to end	Day	11% 4 20% 39% 19% 7%	533
August	1st to 10th	Day	13% 5% 21% 32% 20% 9%	486
	11th to 20th	Day	14% 4 14% 37% 23% 9%	479
	21st to end	Day	15% 6% 22% 29% 21% 7%	539
September	1st to 10th	Day	15% 7% 21% 33% 18% 6%	490
	11th to 20th	Day	10% 6% 21% 26% 26% 11%	490
	21st to end	Day	18% 11% 22% 25% 19% 5%	490
October	1st to 10th	Day	21% 13% 24% 23% 14% 4	490
	11th to 20th	Day	24% 17% 31% 22% 4 1	490
	21st to end	Day	32% 17% 28% 17% 5%	460
November	1st to 10th	Day	32% 16% 27% 18% 7%	277
	11th to 20th	Day	29% 20% 30% 17% 3 2	200
	21st to end	Day	29% 23% 34% 13% 2	200
December	1st to 10th	Day	31% 19% 30% 16% 5%	200
	11th to 20th	Day	30% 23% 29% 15% 4	200
	21st to end	Day	34% 19% 34% 10% 2	220
January	1st to 10th	Night	23% 18% 33% 21% 5% 1	1000
	11th to 20th	Night	29% 15% 31% 20% 6% 1	962
	21st to end	Night	21% 12% 33% 26% 7% 1	880
February	1st to 10th	Night	21% 16% 36% 22% 4	800
	11th to 20th	Night	19% 14% 35% 26% 6% 1	783
	21st to end	Night	22% 15% 35% 23% 4	647
March	1st to 10th	Night	18% 11% 37% 26% 8%	760
	11th to 20th	Night	19% 14% 34% 25% 7% 1	760
	21st to end	Night	20% 8% 31% 29% 11% 1	836
April	1st to 10th	Night	23% 11% 30% 29% 6% 1	760
	11th to 20th	Night	23% 9% 26% 28% 12% 2	568
	21st to end	Night	25% 7% 26% 28% 14% 1	570
May	1st to 10th	Night	16% 4 23% 39% 16% 2	570
	11th to 20th	Night	18% 3 19% 39% 19% 1	460
	21st to end	Night	12% 3 23% 38% 21% 3	411
June	1st to 10th	Night	14% 7% 22% 38% 17% 2	380
	11th to 20th	Night	10% 5% 23% 38% 22% 1	380
	21st to end	Night	16% 3 20% 35% 24% 1	380
July	1st to 10th	Night	10% 4 14% 46% 24% 2	370
	11th to 20th	Night	10% 3 19% 34% 30% 3	413
	21st to end	Night	9% 3 17% 42% 29% 1	624
August	1st to 10th	Night	12% 4 16% 36% 31% 2	567
	11th to 20th	Night	9% 4 16% 33% 31% 6%	564
	21st to end	Night	13% 5% 21% 30% 28% 4	627
September	1st to 10th	Night	11% 6% 20% 34% 22% 7%	752
	11th to 20th	Night	13% 5% 19% 33% 24% 6%	760
	21st to end	Night	18% 8% 21% 27% 20% 6%	760
October	1st to 10th	Night	21% 10% 24% 27% 16% 2	760
	11th to 20th	Night	29% 15% 22% 24% 8% 2	760
	21st to end	Night	32% 14% 27% 22% 4 1	836
November	1st to 10th	Night	30% 13% 27% 21% 8% 1	780
	11th to 20th	Night	28% 19% 28% 18% 8%	800
	21st to end	Night	36% 15% 28% 18% 3	800
December	1st to 10th	Night	33% 20% 30% 12% 5%	800
	11th to 20th	Night	26% 20% 34% 16% 3	881
	21st to end	Night	33% 14% 34% 16% 3	1100

Page generated at 2025-02-22 06:51:37. Version ac07

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