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 2024-09-29.

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% 11% 4 8% 5% 4 4 3 5% 6% 33%	101166
	Night	16% 14% 5% 10% 5% 4 4 3 5% 5% 28%	97090
Transparency	Day	51% 6% 12% 20% 10% 1	100923
	Night	58% 6% 11% 16% 9% 1	96953
Seeing	Day	19% 10% 27% 27% 14% 4	15050
	Night	21% 11% 27% 27% 13% 2	24232

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	15% 24% 16% 16% 8% 3 4 2 2 3 6%	2217
	11th to 20th	Day	11% 21% 11% 29% 8% 4 4 3 3 2 5%	2574
	21st to end	Day	19% 21% 12% 15% 6% 5% 4 3 3 3 10%	3124
February	1st to 10th	Day	13% 21% 7% 19% 10% 5% 4 3 3 4 11%	1710
	11th to 20th	Day	12% 17% 8% 14% 8% 6% 5% 4 5% 6% 17%	1663
	21st to end	Day	14% 18% 6% 12% 5% 6% 5% 4 5% 5% 19%	1532
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 6% 6% 35%	2069
October	1st to 10th	Day	21% 8% 3 8% 4 4 4 3 4 6% 33%	1828
	11th to 20th	Day	26% 15% 3 10% 5% 4 5% 3 5% 5% 20%	1800
	21st to end	Day	30% 15% 5% 10% 5% 4 3 2 4 5% 17%	1906
November	1st to 10th	Day	19% 19% 4 9% 6% 4 4 4 5% 6% 21%	1632
	11th to 20th	Day	17% 23% 6% 9% 5% 5% 5% 4 4 5% 17%	1520
	21st to end	Day	22% 26% 7% 10% 5% 5% 4 3 4 4 10%	1520
December	1st to 10th	Day	16% 31% 8% 13% 6% 4 4 3 4 3 7%	1520
	11th to 20th	Day	19% 25% 7% 16% 7% 4 3 3 3 4 10%	1784
	21st to end	Day	28% 24% 6% 14% 5% 3 3 2 3 3 7%	2431
January	1st to 10th	Night	15% 26% 12% 18% 7% 4 4 2 3 3 7%	4734
	11th to 20th	Night	15% 19% 9% 24% 9% 5% 4 3 3 3 6%	4378
	21st to end	Night	18% 21% 9% 15% 7% 5% 4 3 4 3 12%	4532
February	1st to 10th	Night	13% 20% 7% 15% 10% 6% 4 4 5% 3 13%	2470
	11th to 20th	Night	13% 16% 7% 16% 7% 5% 4 3 4 5% 20%	2403
	21st to end	Night	15% 15% 5% 12% 6% 5% 5% 3 5% 6% 22%	1921
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% 4 3 5% 6% 37%	2079
October	1st to 10th	Night	19% 8% 3 8% 5% 4 5% 3 5% 6% 33%	2132
	11th to 20th	Night	26% 12% 4 9% 5% 4 4 4 5% 5% 21%	2160
	21st to end	Night	28% 13% 4 10% 5% 4 5% 3 3 6% 19%	2448
November	1st to 10th	Night	19% 18% 4 9% 5% 4 5% 3 4 5% 25%	2444
	11th to 20th	Night	18% 20% 5% 10% 5% 5% 5% 3 5% 6% 17%	2660
	21st to end	Night	23% 24% 6% 8% 5% 4 4 3 4 5% 13%	2660
December	1st to 10th	Night	20% 29% 9% 11% 6% 4 4 3 3 3 8%	2660
	11th to 20th	Night	16% 25% 8% 16% 6% 4 4 3 4 4 11%	3408
	21st to end	Night	25% 22% 9% 15% 6% 4 3 2 3 3 8%	5236

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	84% 4 8% 3	2218
	11th to 20th	Day	88% 3 5% 4 1	2574
	21st to end	Day	82% 4 8% 5% 1	3124
February	1st to 10th	Day	78% 6% 7% 8% 1	1710
	11th to 20th	Day	68% 7% 11% 10% 4	1672
	21st to end	Day	66% 7% 10% 13% 4	1532
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	50% 6% 12% 23% 8%	2069
October	1st to 10th	Day	51% 7% 12% 19% 9% 1	1828
	11th to 20th	Day	66% 6% 11% 12% 5% 1	1800
	21st to end	Day	71% 5% 9% 12% 3	1906
November	1st to 10th	Day	64% 5% 13% 14% 5%	1632
	11th to 20th	Day	68% 8% 12% 8% 5%	1520
	21st to end	Day	75% 6% 11% 6%	1520
December	1st to 10th	Day	83% 6% 7% 3 1	1520
	11th to 20th	Day	79% 5% 10% 6%	1783
	21st to end	Day	84% 3 9% 3	2431
January	1st to 10th	Night	85% 5% 6% 4	4734
	11th to 20th	Night	86% 4 6% 3 1	4378
	21st to end	Night	78% 6% 10% 6% 1	4532
February	1st to 10th	Night	74% 7% 7% 10% 2	2470
	11th to 20th	Night	68% 6% 10% 12% 4	2405
	21st to end	Night	63% 5% 13% 12% 6%	1921
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%	2079
October	1st to 10th	Night	52% 6% 11% 20% 11% 1	2132
	11th to 20th	Night	62% 6% 12% 16% 4	2160
	21st to end	Night	68% 6% 10% 12% 5%	2448
November	1st to 10th	Night	61% 5% 12% 17% 5%	2444
	11th to 20th	Night	66% 7% 14% 9% 3 1	2660
	21st to end	Night	72% 6% 14% 6% 1	2660
December	1st to 10th	Night	82% 6% 7% 3 1	2660
	11th to 20th	Night	77% 6% 11% 5%	3408
	21st to end	Night	84% 4 9% 3	5236

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	25% 20% 32% 18% 4 2	184
	11th to 20th	Day	20% 16% 39% 19% 6%	270
	21st to end	Day	28% 13% 30% 22% 7%	297
February	1st to 10th	Day	22% 23% 34% 17% 3	270
	11th to 20th	Day	23% 17% 39% 20% 2	270
	21st to end	Day	20% 28% 36% 15% 1	225
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% 10% 23% 25% 19% 5%	483
October	1st to 10th	Day	21% 12% 24% 24% 15% 4	450
	11th to 20th	Day	26% 17% 30% 22% 4 1	450
	21st to end	Day	33% 16% 29% 17% 5%	421
November	1st to 10th	Day	30% 16% 28% 19% 8%	250
	11th to 20th	Day	30% 19% 28% 18% 3 2	180
	21st to end	Day	28% 22% 34% 14% 2	180
December	1st to 10th	Day	30% 19% 31% 17% 4	180
	11th to 20th	Day	29% 22% 29% 16% 4	180
	21st to end	Day	34% 21% 35% 8% 2 1	198
January	1st to 10th	Night	24% 18% 31% 21% 5% 1	950
	11th to 20th	Night	29% 15% 31% 19% 6% 1	914
	21st to end	Night	21% 10% 33% 27% 8% 1	836
February	1st to 10th	Night	21% 16% 36% 22% 4	760
	11th to 20th	Night	19% 12% 36% 26% 6% 1	743
	21st to end	Night	22% 15% 35% 23% 4	628
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% 22% 26% 20% 6%	756
October	1st to 10th	Night	22% 9% 24% 28% 16% 2	720
	11th to 20th	Night	30% 15% 22% 23% 8% 2	720
	21st to end	Night	33% 13% 27% 22% 4 1	792
November	1st to 10th	Night	30% 13% 27% 21% 8% 1	740
	11th to 20th	Night	27% 19% 29% 17% 8%	760
	21st to end	Night	36% 15% 29% 18% 3	760
December	1st to 10th	Night	33% 20% 30% 12% 4	760
	11th to 20th	Night	25% 20% 35% 16% 3	836
	21st to end	Night	33% 14% 34% 15% 3	1045

Page generated at 2024-09-26 09:52:25. Version ac07

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