Owen Sound
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Owen Sound clear sky chart from 2005-11-06 to 2024-03-23.

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% 12% 5% 9% 6% 3 4 4 5% 6% 29%	78579
	Night	16% 14% 6% 11% 7% 3 4 4 4 5% 25%	81293
Transparency	Day	55% 7% 11% 17% 9% 1	78286
	Night	61% 7% 10% 14% 7% 1	81121
Seeing	Day	19% 13% 29% 25% 11% 3	14193
	Night	21% 12% 29% 26% 11% 1	23595

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	14% 22% 13% 17% 11% 3 3 3 3 3 7%	2212
	11th to 20th	Day	10% 21% 11% 20% 16% 5% 4 3 3 2 6%	2654
	21st to end	Day	16% 21% 12% 15% 9% 4 6% 3 3 3 8%	3124
February	1st to 10th	Day	13% 19% 10% 17% 11% 5% 4 4 4 4 11%	1710
	11th to 20th	Day	14% 14% 8% 15% 11% 5% 5% 3 5% 5% 15%	1663
	21st to end	Day	14% 18% 8% 12% 9% 5% 6% 4 4 5% 16%	1519
March	1st to 10th	Day	14% 13% 4 11% 9% 4 4 4 4 5% 27%	2030
	11th to 20th	Day	13% 14% 7% 10% 6% 3 6% 5% 4 5% 28%	2090
	21st to end	Day	17% 11% 5% 8% 7% 3 4 4 4 7% 31%	2200
April	1st to 10th	Day	20% 13% 5% 7% 6% 4 3 4 4 7% 27%	2073
	11th to 20th	Day	19% 11% 4 6% 5% 2 3 4 5% 6% 36%	2306
	21st to end	Day	21% 10% 4 6% 4 3 4 4 5% 6% 32%	2340
May	1st to 10th	Day	18% 9% 3 6% 5% 3 4 4 5% 7% 37%	2340
	11th to 20th	Day	16% 8% 3 6% 5% 3 4 4 5% 5% 40%	2402
	21st to end	Day	13% 6% 2 5% 5% 3 4 4 6% 8% 43%	2725
June	1st to 10th	Day	15% 7% 2 5% 5% 3 5% 5% 6% 7% 40%	2622
	11th to 20th	Day	12% 5% 2 5% 4 3 4 6% 6% 9% 43%	2700
	21st to end	Day	16% 6% 2 6% 4 4 4 5% 6% 8% 41%	2700
July	1st to 10th	Day	12% 5% 2 4 4 3 4 5% 7% 8% 47%	2700
	11th to 20th	Day	12% 6% 3 5% 5% 3 4 5% 6% 9% 41%	2632
	21st to end	Day	13% 5% 2 5% 5% 3 5% 5% 6% 9% 42%	2547
August	1st to 10th	Day	13% 6% 2 5% 6% 2 5% 5% 6% 9% 42%	2327
	11th to 20th	Day	13% 6% 2 5% 5% 3 5% 5% 7% 8% 42%	2303
	21st to end	Day	14% 8% 2 5% 6% 3 5% 6% 6% 8% 38%	2552
September	1st to 10th	Day	15% 7% 3 6% 5% 3 5% 5% 6% 7% 39%	2148
	11th to 20th	Day	14% 5% 3 5% 4 3 5% 5% 6% 8% 41%	1980
	21st to end	Day	19% 8% 2 6% 6% 3 5% 5% 5% 7% 34%	1980
October	1st to 10th	Day	21% 9% 3 7% 6% 3 5% 5% 5% 7% 30%	1818
	11th to 20th	Day	25% 14% 5% 7% 7% 4 5% 5% 5% 5% 20%	1800
	21st to end	Day	31% 14% 5% 8% 7% 3 3 4 3 5% 17%	1922
November	1st to 10th	Day	17% 19% 5% 7% 5% 4 4 4 5% 7% 22%	1623
	11th to 20th	Day	17% 18% 6% 10% 6% 3 6% 4 5% 6% 18%	1520
	21st to end	Day	20% 22% 7% 11% 7% 3 5% 4 5% 5% 12%	1520
December	1st to 10th	Day	14% 28% 12% 14% 8% 3 3 3 3 4 7%	1520
	11th to 20th	Day	18% 22% 9% 15% 7% 3 4 4 4 4 10%	1846
	21st to end	Day	25% 22% 8% 15% 6% 3 4 3 3 4 7%	2431
January	1st to 10th	Night	14% 25% 11% 21% 10% 3 4 2 2 3 5%	4742
	11th to 20th	Night	14% 15% 10% 23% 13% 4 5% 3 3 3 6%	4308
	21st to end	Night	15% 20% 12% 14% 9% 5% 5% 4 3 4 9%	4532
February	1st to 10th	Night	13% 18% 7% 17% 12% 5% 5% 4 4 3 13%	2470
	11th to 20th	Night	12% 15% 10% 14% 9% 5% 5% 5% 3 5% 18%	2403
	21st to end	Night	14% 15% 7% 12% 8% 4 5% 5% 4 5% 21%	1932
March	1st to 10th	Night	13% 12% 7% 11% 8% 3 4 4 4 5% 28%	2136
	11th to 20th	Night	12% 14% 5% 9% 8% 2 4 4 4 6% 32%	2089
	21st to end	Night	16% 11% 5% 8% 5% 3 5% 4 5% 5% 34%	2201
April	1st to 10th	Night	19% 12% 4 8% 5% 3 5% 4 5% 6% 30%	1886
	11th to 20th	Night	18% 10% 4 5% 4 3 4 3 5% 6% 38%	1619
	21st to end	Night	19% 11% 4 8% 5% 3 4 4 4 6% 32%	1620
May	1st to 10th	Night	17% 7% 3 5% 5% 4 5% 4 4 9% 37%	1620
	11th to 20th	Night	16% 6% 2 5% 5% 4 4 5% 5% 6% 42%	1487
	21st to end	Night	10% 5% 2 5% 5% 2 5% 6% 6% 7% 47%	1550
June	1st to 10th	Night	14% 7% 3 6% 5% 3 5% 4 6% 7% 41%	1333
	11th to 20th	Night	12% 5% 2 4 5% 3 5% 6% 5% 9% 43%	1260
	21st to end	Night	14% 5% 2 5% 5% 2 5% 5% 6% 8% 42%	1260
July	1st to 10th	Night	9% 4 2 4 4 2 3 4 6% 8% 54%	1260
	11th to 20th	Night	10% 4 3 5% 5% 2 5% 6% 6% 9% 45%	1321
	21st to end	Night	9% 5% 2 5% 5% 3 5% 6% 6% 8% 47%	1771
August	1st to 10th	Night	10% 5% 2 5% 4 3 5% 4 6% 7% 49%	1611
	11th to 20th	Night	9% 5% 2 5% 5% 2 5% 5% 7% 7% 48%	1598
	21st to end	Night	12% 6% 3 6% 6% 3 4 5% 5% 7% 43%	1786
September	1st to 10th	Night	12% 5% 2 4 6% 3 4 4 7% 8% 46%	1808
	11th to 20th	Night	14% 5% 2 4 4 2 4 6% 6% 8% 46%	1980
	21st to end	Night	18% 7% 3 6% 6% 3 4 4 5% 7% 36%	1980
October	1st to 10th	Night	20% 8% 3 7% 6% 4 4 4 5% 7% 33%	2142
	11th to 20th	Night	26% 12% 3 7% 6% 4 4 4 4 6% 23%	2160
	21st to end	Night	27% 16% 4 7% 7% 3 4 5% 4 5% 19%	2430
November	1st to 10th	Night	19% 18% 4 7% 7% 3 4 4 5% 6% 24%	2453
	11th to 20th	Night	18% 16% 5% 10% 7% 4 5% 5% 4 6% 19%	2660
	21st to end	Night	21% 19% 7% 10% 7% 3 4 4 5% 6% 14%	2660
December	1st to 10th	Night	18% 25% 11% 12% 7% 3 4 4 3 4 9%	2660
	11th to 20th	Night	13% 22% 10% 16% 7% 3 4 5% 4 4 11%	3329
	21st to end	Night	23% 21% 9% 16% 8% 4 4 3 2 3 7%	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	83% 7% 7% 3	2213
	11th to 20th	Day	88% 4 4 3 1	2654
	21st to end	Day	82% 6% 7% 4 1	3124
February	1st to 10th	Day	77% 6% 8% 7% 1	1710
	11th to 20th	Day	71% 7% 9% 8% 4	1672
	21st to end	Day	70% 5% 9% 12% 3	1519
March	1st to 10th	Day	58% 7% 13% 14% 7% 1	2033
	11th to 20th	Day	57% 6% 10% 17% 8% 2	2090
	21st to end	Day	52% 5% 12% 17% 12% 2	2200
April	1st to 10th	Day	58% 5% 12% 16% 9%	2073
	11th to 20th	Day	49% 4 9% 21% 15% 1	2306
	21st to end	Day	50% 7% 12% 18% 11% 2	2340
May	1st to 10th	Day	46% 6% 10% 23% 13% 2	2340
	11th to 20th	Day	45% 6% 9% 22% 16% 1	2406
	21st to end	Day	38% 6% 15% 24% 14% 3	2725
June	1st to 10th	Day	41% 8% 11% 24% 16% 1	2622
	11th to 20th	Day	37% 7% 13% 24% 18% 1	2700
	21st to end	Day	40% 7% 13% 24% 14% 2	2700
July	1st to 10th	Day	33% 7% 15% 24% 19% 2	2626
	11th to 20th	Day	37% 7% 14% 30% 11% 2	2551
	21st to end	Day	38% 7% 15% 25% 14% 1	2405
August	1st to 10th	Day	35% 7% 19% 25% 12% 2	2314
	11th to 20th	Day	38% 8% 17% 25% 12%	2303
	21st to end	Day	41% 7% 16% 23% 12% 1	2552
September	1st to 10th	Day	43% 8% 13% 23% 12% 2	2148
	11th to 20th	Day	39% 7% 16% 27% 10%	1980
	21st to end	Day	49% 8% 12% 23% 7% 1	1980
October	1st to 10th	Day	52% 7% 12% 18% 9% 1	1818
	11th to 20th	Day	65% 8% 10% 11% 5% 1	1800
	21st to end	Day	71% 5% 10% 11% 3	1922
November	1st to 10th	Day	63% 7% 11% 14% 5%	1623
	11th to 20th	Day	67% 8% 12% 8% 5%	1520
	21st to end	Day	75% 7% 11% 6% 1	1520
December	1st to 10th	Day	83% 6% 7% 4 1	1520
	11th to 20th	Day	78% 8% 8% 6%	1846
	21st to end	Day	83% 6% 9% 3	2431
January	1st to 10th	Night	85% 6% 5% 3	4742
	11th to 20th	Night	85% 5% 6% 3 1	4308
	21st to end	Night	79% 6% 9% 4 1	4532
February	1st to 10th	Night	76% 6% 7% 9% 2	2470
	11th to 20th	Night	68% 7% 10% 12% 4	2405
	21st to end	Night	64% 7% 11% 11% 6%	1932
March	1st to 10th	Night	58% 5% 11% 16% 9% 1	2146
	11th to 20th	Night	54% 6% 10% 17% 11% 2	2090
	21st to end	Night	51% 5% 11% 19% 13% 2	2201
April	1st to 10th	Night	55% 5% 10% 19% 11% 1	1886
	11th to 20th	Night	47% 5% 8% 20% 18% 2	1619
	21st to end	Night	54% 6% 8% 16% 14% 2	1620
May	1st to 10th	Night	46% 5% 9% 21% 16% 3	1620
	11th to 20th	Night	42% 5% 8% 23% 19% 3	1488
	21st to end	Night	34% 7% 14% 24% 16% 3	1551
June	1st to 10th	Night	41% 6% 11% 21% 18% 2	1333
	11th to 20th	Night	36% 7% 12% 25% 18% 1	1260
	21st to end	Night	37% 9% 13% 26% 14% 2	1260
July	1st to 10th	Night	27% 6% 13% 28% 23% 4	1225
	11th to 20th	Night	33% 7% 14% 30% 14% 2	1279
	21st to end	Night	33% 8% 15% 26% 17% 1	1672
August	1st to 10th	Night	34% 7% 17% 27% 14% 1	1600
	11th to 20th	Night	33% 9% 16% 26% 15% 2	1598
	21st to end	Night	40% 7% 14% 26% 11% 2	1786
September	1st to 10th	Night	34% 9% 14% 28% 14% 2	1808
	11th to 20th	Night	35% 7% 16% 29% 13%	1980
	21st to end	Night	47% 7% 14% 24% 8%	1980
October	1st to 10th	Night	50% 8% 10% 20% 11% 1	2142
	11th to 20th	Night	62% 7% 11% 15% 5%	2160
	21st to end	Night	69% 6% 9% 11% 5%	2430
November	1st to 10th	Night	61% 7% 11% 17% 5%	2453
	11th to 20th	Night	66% 8% 13% 9% 3 1	2660
	21st to end	Night	72% 8% 12% 7% 1	2660
December	1st to 10th	Night	80% 8% 7% 4 1	2660
	11th to 20th	Night	77% 7% 11% 5% 1	3329
	21st to end	Night	84% 5% 7% 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	21% 21% 36% 16% 4 2	182
	11th to 20th	Day	19% 22% 37% 17% 5%	270
	21st to end	Day	28% 15% 30% 22% 5%	297
February	1st to 10th	Day	23% 28% 31% 16% 3	270
	11th to 20th	Day	20% 25% 39% 16% 1	270
	21st to end	Day	24% 29% 36% 11% 1	225
March	1st to 10th	Day	22% 17% 36% 19% 6%	403
	11th to 20th	Day	20% 17% 37% 20% 6%	460
	21st to end	Day	25% 14% 31% 22% 6% 1	470
April	1st to 10th	Day	22% 15% 33% 20% 9%	420
	11th to 20th	Day	27% 14% 27% 17% 9% 6%	412
	21st to end	Day	27% 10% 31% 21% 10% 1	420
May	1st to 10th	Day	22% 9% 31% 26% 10% 3	423
	11th to 20th	Day	18% 7% 29% 27% 15% 3	447
	21st to end	Day	17% 7% 27% 28% 17% 4	485
June	1st to 10th	Day	14% 9% 31% 29% 15% 2	552
	11th to 20th	Day	13% 8% 31% 33% 12% 3	630
	21st to end	Day	16% 7% 31% 30% 13% 3	630
July	1st to 10th	Day	11% 6% 24% 36% 20% 4	621
	11th to 20th	Day	14% 7% 27% 28% 17% 7%	587
	21st to end	Day	13% 5% 24% 37% 16% 5%	488
August	1st to 10th	Day	13% 6% 20% 36% 17% 9%	446
	11th to 20th	Day	14% 4 15% 35% 23% 8%	439
	21st to end	Day	15% 9% 21% 29% 18% 7%	495
September	1st to 10th	Day	14% 9% 25% 28% 16% 7%	450
	11th to 20th	Day	13% 6% 23% 28% 22% 9%	450
	21st to end	Day	15% 12% 26% 24% 17% 4	450
October	1st to 10th	Day	22% 13% 25% 22% 14% 5%	450
	11th to 20th	Day	22% 22% 31% 20% 4 1	450
	21st to end	Day	35% 18% 28% 15% 4	437
November	1st to 10th	Day	28% 17% 30% 18% 6%	246
	11th to 20th	Day	26% 22% 29% 18% 2 2	180
	21st to end	Day	27% 20% 36% 15% 2	180
December	1st to 10th	Day	28% 23% 30% 16% 4	180
	11th to 20th	Day	28% 27% 27% 12% 5%	180
	21st to end	Day	35% 21% 35% 7% 3	198
January	1st to 10th	Night	22% 20% 33% 21% 5%	950
	11th to 20th	Night	25% 18% 31% 19% 6% 1	870
	21st to end	Night	18% 14% 34% 27% 7% 1	836
February	1st to 10th	Night	20% 18% 37% 21% 4	760
	11th to 20th	Night	19% 16% 34% 24% 6%	743
	21st to end	Night	22% 17% 36% 21% 4	628
March	1st to 10th	Night	17% 14% 38% 23% 7%	760
	11th to 20th	Night	19% 15% 35% 24% 6% 1	760
	21st to end	Night	20% 11% 31% 27% 9% 1	801
April	1st to 10th	Night	23% 13% 32% 26% 6%	720
	11th to 20th	Night	22% 10% 30% 25% 12% 1	555
	21st to end	Night	24% 8% 28% 27% 13%	540
May	1st to 10th	Night	19% 5% 26% 35% 14% 2	540
	11th to 20th	Night	19% 4 22% 40% 14% 1	426
	21st to end	Night	12% 4 28% 37% 20% 1	389
June	1st to 10th	Night	15% 5% 27% 39% 11% 2	360
	11th to 20th	Night	13% 6% 22% 41% 18%	360
	21st to end	Night	14% 4 23% 38% 21%	360
July	1st to 10th	Night	9% 4 16% 51% 19% 1	350
	11th to 20th	Night	10% 3 24% 34% 26% 2	382
	21st to end	Night	9% 3 21% 44% 22% 1	591
August	1st to 10th	Night	12% 3 19% 36% 28% 2	537
	11th to 20th	Night	10% 3 13% 39% 29% 5%	534
	21st to end	Night	15% 5% 20% 33% 24% 3	598
September	1st to 10th	Night	12% 6% 23% 34% 19% 6%	720
	11th to 20th	Night	14% 5% 18% 37% 20% 5%	720
	21st to end	Night	18% 8% 24% 27% 18% 4	720
October	1st to 10th	Night	23% 7% 27% 28% 13% 2	720
	11th to 20th	Night	32% 14% 23% 24% 6% 2	720
	21st to end	Night	33% 15% 27% 21% 4	792
November	1st to 10th	Night	29% 13% 30% 20% 7% 1	740
	11th to 20th	Night	25% 19% 32% 17% 7% 1	760
	21st to end	Night	29% 17% 33% 18% 3	760
December	1st to 10th	Night	29% 21% 32% 13% 4	760
	11th to 20th	Night	23% 21% 38% 15% 4 1	788
	21st to end	Night	30% 17% 35% 15% 3	1045

Page generated at 2024-03-19 23:31:09. Version ac07

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