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 2024-02-05.

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% 5% 8% 6% 3 4 4 5% 6% 31%	78035
	Night	17% 14% 6% 10% 7% 3 4 4 4 5% 25%	80819
Transparency	Day	54% 6% 11% 18% 9% 1	77741
	Night	61% 6% 11% 15% 7% 1	80648
Seeing	Day	19% 10% 26% 27% 14% 4	14081
	Night	22% 11% 27% 27% 12% 2	23490

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	16% 24% 16% 15% 9% 3 4 3 2 3 6%	2217
	11th to 20th	Day	12% 20% 11% 23% 13% 3 4 3 3 2 5%	2574
	21st to end	Day	19% 20% 12% 13% 7% 4 4 4 3 3 10%	3124
February	1st to 10th	Day	14% 19% 9% 17% 10% 4 4 4 3 3 12%	1656
	11th to 20th	Day	13% 15% 8% 13% 10% 5% 6% 5% 5% 6% 17%	1573
	21st to end	Day	15% 18% 7% 11% 6% 4 6% 5% 5% 5% 19%	1444
March	1st to 10th	Day	14% 11% 4 8% 8% 4 5% 5% 5% 6% 30%	1912
	11th to 20th	Day	13% 12% 5% 10% 6% 3 5% 5% 4 6% 30%	1980
	21st to end	Day	17% 9% 4 6% 7% 3 4 4 5% 6% 35%	2178
April	1st to 10th	Day	20% 11% 4 8% 6% 3 4 4 5% 7% 30%	2075
	11th to 20th	Day	19% 9% 3 6% 4 3 3 3 4 6% 39%	2312
	21st to end	Day	20% 8% 4 6% 4 2 4 4 5% 7% 35%	2340
May	1st to 10th	Day	18% 7% 3 5% 5% 3 5% 4 5% 8% 38%	2340
	11th to 20th	Day	16% 7% 3 5% 4 3 4 4 4 6% 43%	2394
	21st to end	Day	11% 5% 3 5% 4 3 4 5% 5% 9% 46%	2725
June	1st to 10th	Day	13% 7% 3 4 4 3 5% 6% 6% 8% 41%	2659
	11th to 20th	Day	12% 5% 2 5% 5% 3 5% 5% 6% 9% 43%	2700
	21st to end	Day	15% 6% 2 5% 5% 2 4 5% 6% 8% 43%	2700
July	1st to 10th	Day	10% 4 2 4 4 3 4 5% 7% 8% 50%	2700
	11th to 20th	Day	11% 5% 3 5% 5% 2 4 5% 6% 8% 46%	2655
	21st to end	Day	10% 5% 2 5% 5% 3 4 5% 6% 9% 45%	2548
August	1st to 10th	Day	12% 5% 2 4 4 2 4 5% 6% 9% 47%	2327
	11th to 20th	Day	12% 5% 2 4 4 3 5% 4 6% 8% 46%	2303
	21st to end	Day	13% 6% 2 5% 5% 3 5% 5% 6% 9% 41%	2563
September	1st to 10th	Day	13% 5% 3 7% 5% 3 4 5% 5% 8% 41%	2135
	11th to 20th	Day	14% 5% 3 5% 5% 3 4 4 6% 9% 41%	1980
	21st to end	Day	18% 7% 3 6% 6% 4 6% 4 5% 6% 36%	1980
October	1st to 10th	Day	21% 8% 3 8% 5% 3 5% 4 4 6% 33%	1828
	11th to 20th	Day	26% 14% 4 9% 7% 3 4 4 5% 5% 20%	1800
	21st to end	Day	30% 14% 5% 8% 6% 3 3 3 4 5% 17%	1906
November	1st to 10th	Day	19% 18% 5% 8% 7% 3 4 4 5% 6% 21%	1632
	11th to 20th	Day	19% 20% 6% 9% 5% 4 5% 5% 4 5% 17%	1520
	21st to end	Day	22% 24% 8% 9% 6% 4 4 4 4 4 10%	1520
December	1st to 10th	Day	17% 28% 10% 13% 7% 3 5% 3 4 3 7%	1520
	11th to 20th	Day	19% 24% 8% 15% 8% 3 3 4 3 4 10%	1784
	21st to end	Day	28% 23% 7% 13% 6% 2 4 3 3 3 7%	2431
January	1st to 10th	Night	16% 25% 12% 16% 9% 3 4 3 3 3 7%	4734
	11th to 20th	Night	15% 18% 10% 20% 13% 4 5% 3 3 3 6%	4378
	21st to end	Night	18% 20% 10% 13% 8% 4 4 4 4 4 12%	4532
February	1st to 10th	Night	13% 19% 8% 14% 11% 5% 5% 4 4 3 13%	2399
	11th to 20th	Night	14% 14% 9% 15% 8% 4 4 4 4 5% 20%	2273
	21st to end	Night	16% 14% 7% 11% 7% 4 5% 4 5% 6% 22%	1811
March	1st to 10th	Night	13% 12% 5% 10% 7% 3 5% 3 5% 5% 32%	2034
	11th to 20th	Night	14% 12% 5% 9% 8% 3 3 4 3 5% 33%	1979
	21st to end	Night	17% 11% 4 7% 5% 3 4 4 4 6% 35%	2178
April	1st to 10th	Night	21% 10% 3 6% 6% 3 4 4 4 6% 32%	1895
	11th to 20th	Night	18% 8% 4 6% 4 2 4 4 5% 7% 38%	1602
	21st to end	Night	21% 9% 4 7% 6% 3 4 4 5% 5% 33%	1620
May	1st to 10th	Night	16% 6% 4 7% 6% 3 4 5% 5% 8% 38%	1620
	11th to 20th	Night	14% 7% 3 6% 5% 3 4 4 5% 6% 42%	1497
	21st to end	Night	10% 5% 2 5% 5% 3 5% 5% 6% 8% 46%	1550
June	1st to 10th	Night	14% 6% 3 6% 7% 4 5% 4 5% 7% 41%	1296
	11th to 20th	Night	12% 4 2 5% 4 3 5% 5% 6% 10% 43%	1260
	21st to end	Night	15% 6% 3 4 5% 3 4 5% 7% 7% 41%	1260
July	1st to 10th	Night	10% 3 3 3 4 3 3 4 5% 10% 53%	1260
	11th to 20th	Night	9% 5% 3 5% 5% 3 5% 5% 6% 9% 46%	1302
	21st to end	Night	9% 4 2 5% 5% 3 5% 6% 6% 7% 48%	1766
August	1st to 10th	Night	10% 4 3 5% 4 3 3 5% 5% 9% 49%	1611
	11th to 20th	Night	9% 4 2 5% 6% 4 4 4 6% 8% 48%	1598
	21st to end	Night	12% 7% 2 6% 5% 3 4 5% 5% 7% 43%	1782
September	1st to 10th	Night	11% 4 2 5% 4 3 4 6% 7% 8% 46%	1814
	11th to 20th	Night	12% 5% 2 5% 5% 3 4 5% 5% 7% 46%	1980
	21st to end	Night	17% 7% 3 7% 6% 3 5% 4 5% 6% 37%	1980
October	1st to 10th	Night	19% 8% 3 7% 6% 3 5% 5% 5% 6% 34%	2132
	11th to 20th	Night	26% 11% 5% 8% 6% 3 4 5% 5% 5% 21%	2160
	21st to end	Night	28% 13% 4 9% 6% 3 5% 4 3 6% 19%	2448
November	1st to 10th	Night	20% 16% 4 7% 6% 3 5% 4 4 5% 25%	2444
	11th to 20th	Night	19% 19% 6% 9% 6% 4 5% 4 5% 6% 17%	2660
	21st to end	Night	24% 23% 7% 7% 6% 3 4 4 5% 5% 13%	2660
December	1st to 10th	Night	21% 26% 11% 11% 6% 3 5% 4 3 4 8%	2660
	11th to 20th	Night	16% 23% 9% 15% 7% 3 5% 4 4 4 11%	3408
	21st to end	Night	26% 21% 9% 14% 7% 3 4 3 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% 5% 7% 8% 2	1656
	11th to 20th	Day	69% 7% 11% 10% 4	1582
	21st to end	Day	67% 6% 9% 12% 5%	1444
March	1st to 10th	Day	56% 7% 12% 16% 8% 1	1915
	11th to 20th	Day	54% 6% 11% 17% 9% 2	1980
	21st to end	Day	51% 4 11% 20% 12% 2	2178
April	1st to 10th	Day	55% 5% 11% 18% 10%	2075
	11th to 20th	Day	48% 5% 8% 23% 16% 1	2312
	21st to end	Day	49% 7% 12% 19% 11% 3	2340
May	1st to 10th	Day	44% 6% 9% 25% 13% 3	2340
	11th to 20th	Day	43% 6% 9% 24% 17% 2	2398
	21st to end	Day	36% 6% 15% 24% 15% 3	2725
June	1st to 10th	Day	40% 7% 11% 25% 16% 1	2659
	11th to 20th	Day	36% 7% 11% 26% 18% 1	2700
	21st to end	Day	39% 6% 13% 25% 15% 2	2700
July	1st to 10th	Day	30% 7% 15% 26% 20% 2	2626
	11th to 20th	Day	35% 6% 14% 32% 12% 2	2574
	21st to end	Day	35% 7% 14% 27% 15% 1	2406
August	1st to 10th	Day	34% 7% 16% 28% 14% 2	2314
	11th to 20th	Day	36% 7% 16% 28% 13%	2303
	21st to end	Day	40% 6% 15% 25% 12% 1	2563
September	1st to 10th	Day	41% 8% 12% 25% 13% 1	2135
	11th to 20th	Day	38% 6% 16% 28% 11%	1980
	21st to end	Day	49% 6% 13% 23% 7%	1980
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	75% 6% 7% 9% 2	2399
	11th to 20th	Night	68% 6% 10% 12% 4	2275
	21st to end	Night	64% 5% 12% 12% 6%	1811
March	1st to 10th	Night	56% 7% 11% 17% 9% 1	2044
	11th to 20th	Night	55% 5% 9% 18% 11% 2	1980
	21st to end	Night	50% 6% 9% 19% 13% 2	2178
April	1st to 10th	Night	54% 5% 9% 21% 10% 1	1895
	11th to 20th	Night	46% 5% 8% 21% 19% 2	1602
	21st to end	Night	53% 5% 8% 16% 14% 2	1620
May	1st to 10th	Night	46% 5% 9% 21% 16% 3	1620
	11th to 20th	Night	43% 5% 7% 23% 19% 3	1498
	21st to end	Night	35% 6% 15% 24% 16% 3	1551
June	1st to 10th	Night	42% 5% 11% 22% 18% 3	1296
	11th to 20th	Night	36% 6% 13% 25% 19% 2	1260
	21st to end	Night	39% 6% 11% 27% 14% 2	1260
July	1st to 10th	Night	28% 4 13% 28% 22% 4	1225
	11th to 20th	Night	33% 7% 13% 31% 15% 2	1260
	21st to end	Night	33% 8% 14% 27% 17% 1	1668
August	1st to 10th	Night	33% 7% 16% 27% 15% 2	1600
	11th to 20th	Night	33% 7% 17% 26% 15% 2	1598
	21st to end	Night	40% 6% 14% 27% 12% 1	1782
September	1st to 10th	Night	34% 8% 13% 29% 14% 2	1814
	11th to 20th	Night	37% 6% 16% 29% 12%	1980
	21st to end	Night	48% 6% 14% 24% 8%	1980
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	24% 23% 33% 16% 4	252
	11th to 20th	Day	23% 17% 40% 19% 1	240
	21st to end	Day	22% 27% 36% 15% 1	198
March	1st to 10th	Day	21% 13% 37% 21% 7% 1	355
	11th to 20th	Day	20% 14% 32% 26% 7% 1	420
	21st to end	Day	24% 12% 29% 27% 7% 2	462
April	1st to 10th	Day	21% 12% 32% 24% 11%	420
	11th to 20th	Day	24% 12% 29% 17% 11% 6%	412
	21st to end	Day	25% 8% 28% 26% 11% 1	420
May	1st to 10th	Day	21% 7% 27% 29% 13% 2	423
	11th to 20th	Day	17% 7% 24% 32% 17% 3	447
	21st to end	Day	12% 6% 24% 30% 23% 6%	485
June	1st to 10th	Day	13% 5% 27% 35% 17% 3	589
	11th to 20th	Day	13% 6% 24% 36% 18% 4	630
	21st to end	Day	15% 4 25% 35% 16% 3	630
July	1st to 10th	Day	9% 3 21% 35% 27% 4	621
	11th to 20th	Day	11% 5% 22% 34% 20% 7%	618
	21st to end	Day	12% 4 19% 39% 20% 6%	489
August	1st to 10th	Day	14% 4 19% 33% 21% 9%	446
	11th to 20th	Day	13% 4 12% 38% 24% 9%	439
	21st to end	Day	16% 6% 20% 29% 21% 7%	495
September	1st to 10th	Day	14% 6% 22% 33% 19% 7%	450
	11th to 20th	Day	11% 6% 22% 26% 25% 9%	450
	21st to end	Day	17% 10% 22% 25% 20% 6%	450
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	22% 16% 36% 22% 4	739
	11th to 20th	Night	19% 12% 35% 27% 7% 1	703
	21st to end	Night	23% 15% 35% 23% 5%	592
March	1st to 10th	Night	19% 11% 36% 27% 8%	720
	11th to 20th	Night	19% 13% 34% 24% 8% 1	720
	21st to end	Night	21% 8% 29% 29% 12% 1	792
April	1st to 10th	Night	23% 11% 29% 29% 7% 1	720
	11th to 20th	Night	22% 9% 27% 28% 13% 2	538
	21st to end	Night	25% 6% 25% 29% 14% 1	540
May	1st to 10th	Night	17% 4 23% 38% 16% 2	540
	11th to 20th	Night	19% 3 19% 39% 19% 1	436
	21st to end	Night	12% 3 22% 39% 21% 3	389
June	1st to 10th	Night	15% 5% 22% 38% 18% 3	360
	11th to 20th	Night	11% 5% 23% 38% 23% 1	360
	21st to end	Night	15% 3 19% 36% 26% 1	360
July	1st to 10th	Night	10% 4 13% 47% 24% 2	350
	11th to 20th	Night	10% 3 19% 34% 30% 3	390
	21st to end	Night	9% 3 18% 42% 27% 1	591
August	1st to 10th	Night	12% 3 16% 36% 31% 2	537
	11th to 20th	Night	9% 3 15% 34% 32% 6%	534
	21st to end	Night	13% 5% 22% 29% 28% 4	594
September	1st to 10th	Night	11% 6% 20% 35% 21% 7%	712
	11th to 20th	Night	13% 5% 20% 33% 22% 6%	720
	21st to end	Night	18% 8% 22% 26% 20% 6%	720
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 2024-02-02 05:20:29. Version ac07

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