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 2025-07-06.

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% 13% 5% 10% 5% 4 4 3 5% 6% 29%	119897
	Night	15% 14% 6% 12% 6% 5% 4 3 4 6% 26%	118895
Transparency	Day	54% 6% 12% 18% 10% 1	123487
	Night	58% 6% 11% 15% 8% 1	123453
Seeing	Day	20% 13% 29% 24% 11% 3	15959
	Night	21% 12% 29% 26% 11% 1	25159

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	11% 20% 11% 21% 12% 4 3 2 3 3 9%	3176
	11th to 20th	Day	9% 22% 11% 26% 13% 6% 4 2 2 1 5%	3776
	21st to end	Day	12% 19% 10% 22% 9% 7% 5% 3 3 4 7%	4466
February	1st to 10th	Day	12% 20% 9% 19% 10% 6% 4 3 4 4 10%	1800
	11th to 20th	Day	14% 15% 7% 17% 10% 6% 5% 2 4 4 14%	1753
	21st to end	Day	13% 20% 7% 14% 8% 7% 5% 3 4 4 16%	1597
March	1st to 10th	Day	15% 14% 5% 12% 6% 5% 4 3 4 5% 25%	4799
	11th to 20th	Day	11% 17% 8% 12% 5% 4 5% 4 5% 6% 23%	4980
	21st to end	Day	17% 17% 6% 9% 5% 4 3 3 4 5% 25%	5465
April	1st to 10th	Day	19% 15% 4 8% 5% 4 4 3 4 6% 27%	2304
	11th to 20th	Day	19% 12% 3 7% 4 3 3 3 5% 5% 36%	2566
	21st to end	Day	21% 10% 4 7% 4 4 4 3 6% 6% 33%	2600
May	1st to 10th	Day	16% 10% 3 7% 4 4 4 3 5% 7% 37%	5888
	11th to 20th	Day	14% 10% 3 8% 5% 4 4 3 5% 6% 38%	6130
	21st to end	Day	21% 8% 2 5% 4 3 4 3 5% 7% 38%	6949
June	1st to 10th	Day	16% 7% 2 6% 4 4 5% 5% 6% 7% 38%	2914
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 5% 6% 9% 41%	3000
	21st to end	Day	17% 7% 2 6% 4 5% 4 4 5% 8% 39%	3000
July	1st to 10th	Day	14% 6% 3 6% 5% 5% 5% 4 7% 8% 37%	4836
	11th to 20th	Day	13% 6% 2 5% 4 3 4 4 6% 8% 46%	4622
	21st to end	Day	11% 6% 2 5% 4 4 4 4 6% 8% 45%	4466
August	1st to 10th	Day	13% 6% 2 6% 5% 4 6% 4 7% 8% 39%	4104
	11th to 20th	Day	15% 7% 3 7% 4 5% 5% 4 6% 8% 37%	4044
	21st to end	Day	11% 6% 2 5% 4 4 5% 5% 6% 8% 44%	4482
September	1st to 10th	Day	15% 7% 3 7% 4 4 4 4 6% 7% 39%	2267
	11th to 20th	Day	14% 5% 3 6% 3 4 4 4 6% 8% 43%	2090
	21st to end	Day	18% 9% 2 7% 5% 5% 5% 4 5% 7% 34%	2090
October	1st to 10th	Day	20% 9% 3 8% 5% 4 4 4 6% 7% 31%	1919
	11th to 20th	Day	24% 14% 4 8% 5% 5% 4 4 5% 5% 21%	1900
	21st to end	Day	30% 15% 5% 9% 5% 4 4 3 3 6% 17%	2028
November	1st to 10th	Day	18% 20% 4 8% 6% 4 4 3 5% 6% 22%	1710
	11th to 20th	Day	16% 20% 6% 11% 5% 5% 5% 3 5% 6% 18%	1600
	21st to end	Day	19% 25% 6% 12% 6% 4 4 3 5% 5% 11%	1600
December	1st to 10th	Day	13% 30% 11% 15% 6% 4 3 3 3 4 10%	2600
	11th to 20th	Day	18% 25% 8% 17% 5% 4 3 2 3 4 11%	2900
	21st to end	Day	24% 20% 7% 16% 7% 4 3 2 3 4 9%	3476
January	1st to 10th	Night	12% 21% 10% 27% 7% 4 3 2 3 4 8%	6788
	11th to 20th	Night	10% 17% 10% 26% 10% 6% 4 3 3 3 7%	6116
	21st to end	Night	11% 20% 11% 18% 8% 7% 4 3 4 5% 10%	6490
February	1st to 10th	Night	12% 19% 7% 19% 9% 6% 5% 3 4 3 13%	2600
	11th to 20th	Night	12% 17% 8% 15% 8% 6% 4 4 3 5% 17%	2533
	21st to end	Night	13% 16% 6% 13% 7% 6% 5% 4 4 5% 21%	2030
March	1st to 10th	Night	14% 14% 6% 10% 5% 4 4 3 5% 7% 27%	5028
	11th to 20th	Night	8% 15% 5% 9% 5% 4 5% 4 5% 7% 31%	4979
	21st to end	Night	20% 12% 7% 9% 4 4 4 3 4 5% 29%	5467
April	1st to 10th	Night	19% 13% 3 9% 5% 4 4 3 5% 6% 29%	2095
	11th to 20th	Night	18% 11% 3 6% 4 4 4 3 5% 6% 37%	1801
	21st to end	Night	19% 12% 4 9% 4 4 3 3 4 6% 32%	1800
May	1st to 10th	Night	15% 9% 3 7% 5% 4 4 3 5% 8% 36%	4053
	11th to 20th	Night	14% 6% 2 7% 5% 4 4 3 5% 7% 43%	3759
	21st to end	Night	19% 7% 3 6% 4 3 4 4 5% 5% 40%	3926
June	1st to 10th	Night	14% 8% 2 6% 5% 4 4 3 6% 7% 40%	1481
	11th to 20th	Night	11% 6% 2 6% 5% 5% 5% 5% 6% 9% 41%	1400
	21st to end	Night	14% 6% 3 6% 4 4 4 4 6% 8% 41%	1400
July	1st to 10th	Night	9% 7% 4 7% 4 3 3 3 5% 7% 46%	2245
	11th to 20th	Night	13% 5% 2 4 4 3 3 3 5% 7% 51%	2325
	21st to end	Night	8% 7% 2 6% 4 4 4 4 6% 8% 47%	3087
August	1st to 10th	Night	11% 7% 3 7% 4 4 4 4 6% 6% 44%	2825
	11th to 20th	Night	15% 8% 2 7% 4 4 5% 4 5% 6% 40%	2785
	21st to end	Night	13% 6% 2 6% 4 4 4 4 5% 7% 45%	3142
September	1st to 10th	Night	11% 6% 2 5% 5% 4 3 4 6% 8% 46%	1909
	11th to 20th	Night	13% 5% 2 5% 3 3 4 4 6% 8% 48%	2090
	21st to end	Night	17% 8% 2 7% 5% 5% 4 4 5% 7% 36%	2090
October	1st to 10th	Night	19% 8% 3 7% 5% 5% 4 3 5% 6% 34%	2261
	11th to 20th	Night	25% 13% 3 8% 5% 4 4 3 4 6% 24%	2280
	21st to end	Night	26% 16% 4 8% 6% 4 4 4 4 5% 20%	2565
November	1st to 10th	Night	18% 19% 4 8% 6% 4 4 3 5% 5% 25%	2586
	11th to 20th	Night	17% 18% 5% 11% 6% 5% 5% 4 5% 6% 19%	2800
	21st to end	Night	21% 21% 7% 11% 6% 4 4 3 5% 5% 14%	2800
December	1st to 10th	Night	15% 27% 8% 16% 6% 5% 4 3 4 5% 8%	4580
	11th to 20th	Night	12% 25% 9% 19% 6% 5% 4 3 3 4 11%	5277
	21st to end	Night	20% 23% 7% 17% 7% 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	79% 6% 8% 5% 2	3177
	11th to 20th	Day	88% 4 3 3 1	3809
	21st to end	Day	79% 6% 7% 6% 2	4466
February	1st to 10th	Day	78% 6% 8% 7% 1	1800
	11th to 20th	Day	72% 7% 9% 7% 4	1762
	21st to end	Day	71% 5% 9% 12% 3	1597
March	1st to 10th	Day	59% 6% 14% 12% 9%	4802
	11th to 20th	Day	60% 5% 11% 17% 5% 1	4980
	21st to end	Day	59% 5% 11% 17% 7% 1	5465
April	1st to 10th	Day	57% 5% 11% 17% 9%	2304
	11th to 20th	Day	49% 4 9% 22% 15% 1	2566
	21st to end	Day	50% 6% 12% 18% 12% 2	2600
May	1st to 10th	Day	45% 6% 12% 18% 14% 4	5897
	11th to 20th	Day	45% 7% 12% 16% 19% 1	6134
	21st to end	Day	45% 5% 11% 19% 15% 5%	6949
June	1st to 10th	Day	42% 8% 10% 23% 16% 1	2914
	11th to 20th	Day	38% 7% 13% 24% 17% 1	3000
	21st to end	Day	42% 7% 12% 24% 13% 2	3000
July	1st to 10th	Day	42% 5% 16% 19% 15% 2	4762
	11th to 20th	Day	33% 6% 14% 34% 13% 1	4541
	21st to end	Day	34% 6% 12% 29% 18% 1	4324
August	1st to 10th	Day	38% 7% 16% 23% 14% 1	4091
	11th to 20th	Day	43% 6% 17% 23% 11%	4083
	21st to end	Day	35% 6% 15% 32% 12% 1	4482
September	1st to 10th	Day	42% 8% 13% 24% 12% 1	2267
	11th to 20th	Day	38% 7% 15% 27% 13%	2090
	21st to end	Day	49% 7% 12% 23% 9% 1	2090
October	1st to 10th	Day	45% 7% 13% 24% 11% 1	3192
	11th to 20th	Day	55% 5% 11% 20% 8%	3140
	21st to end	Day	61% 5% 13% 17% 4	3317
November	1st to 10th	Day	63% 7% 11% 14% 5%	1710
	11th to 20th	Day	67% 7% 12% 8% 5%	1600
	21st to end	Day	76% 7% 11% 6% 1	1600
December	1st to 10th	Day	79% 5% 11% 4 1	2600
	11th to 20th	Day	77% 7% 8% 7% 1	2900
	21st to end	Day	80% 6% 7% 5% 2	3476
January	1st to 10th	Night	80% 6% 7% 6% 2	6788
	11th to 20th	Night	82% 5% 6% 6% 2	6158
	21st to end	Night	76% 6% 9% 5% 3	6490
February	1st to 10th	Night	76% 6% 8% 9% 2	2600
	11th to 20th	Night	69% 6% 10% 11% 4	2535
	21st to end	Night	64% 7% 11% 11% 6%	2030
March	1st to 10th	Night	55% 5% 15% 14% 10% 1	5038
	11th to 20th	Night	51% 6% 17% 17% 8% 1	4980
	21st to end	Night	57% 6% 10% 15% 11% 1	5467
April	1st to 10th	Night	55% 5% 10% 18% 11% 1	2095
	11th to 20th	Night	49% 5% 8% 20% 17% 1	1801
	21st to end	Night	54% 6% 8% 16% 15% 2	1800
May	1st to 10th	Night	46% 6% 11% 16% 15% 6%	4060
	11th to 20th	Night	40% 7% 11% 22% 18% 2	3760
	21st to end	Night	44% 6% 10% 23% 15% 2	3927
June	1st to 10th	Night	41% 6% 11% 21% 18% 3	1481
	11th to 20th	Night	37% 7% 12% 25% 18% 1	1400
	21st to end	Night	39% 8% 13% 25% 14% 2	1400
July	1st to 10th	Night	38% 4 13% 22% 18% 5%	2210
	11th to 20th	Night	32% 5% 12% 36% 14% 1	2283
	21st to end	Night	33% 6% 14% 26% 20% 2	2988
August	1st to 10th	Night	39% 5% 13% 26% 15% 1	2814
	11th to 20th	Night	41% 8% 17% 20% 13% 1	2812
	21st to end	Night	36% 6% 13% 30% 14% 1	3142
September	1st to 10th	Night	34% 8% 14% 29% 14% 2	1909
	11th to 20th	Night	34% 7% 16% 29% 15%	2090
	21st to end	Night	47% 7% 13% 24% 9%	2090
October	1st to 10th	Night	40% 8% 10% 26% 16% 1	3768
	11th to 20th	Night	53% 5% 14% 17% 11%	3779
	21st to end	Night	54% 7% 15% 19% 5%	4213
November	1st to 10th	Night	60% 7% 11% 17% 5%	2586
	11th to 20th	Night	66% 8% 13% 9% 4 1	2800
	21st to end	Night	73% 7% 12% 7% 1	2800
December	1st to 10th	Night	79% 6% 11% 3 1	4580
	11th to 20th	Night	77% 7% 9% 7% 1	5277
	21st to end	Night	83% 4 7% 5% 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	20% 22% 36% 17% 4 1	203
	11th to 20th	Day	19% 23% 37% 17% 5%	300
	21st to end	Day	27% 19% 29% 21% 5%	330
February	1st to 10th	Day	24% 28% 31% 16% 2	300
	11th to 20th	Day	22% 26% 37% 14% 1	300
	21st to end	Day	24% 28% 35% 12% 1	249
March	1st to 10th	Day	22% 17% 37% 18% 6%	440
	11th to 20th	Day	22% 17% 36% 20% 6%	500
	21st to end	Day	27% 15% 31% 21% 5% 1	550
April	1st to 10th	Day	24% 16% 33% 19% 8% 1	500
	11th to 20th	Day	29% 15% 27% 16% 8% 5%	492
	21st to end	Day	29% 11% 31% 20% 9% 1	500
May	1st to 10th	Day	21% 10% 32% 26% 9% 2	503
	11th to 20th	Day	17% 8% 30% 27% 15% 3	527
	21st to end	Day	18% 8% 27% 27% 16% 4	573
June	1st to 10th	Day	15% 11% 32% 27% 13% 2	644
	11th to 20th	Day	13% 9% 33% 31% 11% 3	730
	21st to end	Day	18% 8% 32% 28% 12% 3	730
July	1st to 10th	Day	12% 8% 25% 34% 18% 3	697
	11th to 20th	Day	14% 7% 29% 28% 16% 6%	635
	21st to end	Day	12% 5% 25% 37% 16% 5%	532
August	1st to 10th	Day	13% 6% 22% 35% 16% 8%	486
	11th to 20th	Day	15% 4 17% 33% 23% 8%	479
	21st to end	Day	14% 10% 22% 29% 18% 6%	539
September	1st to 10th	Day	15% 10% 25% 28% 16% 7%	490
	11th to 20th	Day	12% 6% 22% 28% 21% 11%	490
	21st to end	Day	16% 11% 27% 25% 18% 4	490
October	1st to 10th	Day	21% 14% 26% 21% 13% 4	490
	11th to 20th	Day	21% 22% 32% 20% 4 1	490
	21st to end	Day	34% 19% 27% 16% 4	477
November	1st to 10th	Day	32% 16% 29% 18% 5%	273
	11th to 20th	Day	26% 23% 31% 17% 3 2	200
	21st to end	Day	30% 20% 35% 14% 2	200
December	1st to 10th	Day	28% 23% 31% 15% 4 1	200
	11th to 20th	Day	29% 27% 28% 12% 5%	200
	21st to end	Day	35% 19% 32% 9% 5%	220
January	1st to 10th	Night	22% 19% 34% 21% 4	1000
	11th to 20th	Night	25% 18% 32% 19% 6% 1	915
	21st to end	Night	18% 15% 34% 26% 7% 1	880
February	1st to 10th	Night	20% 19% 37% 21% 4	800
	11th to 20th	Night	20% 16% 34% 23% 6%	783
	21st to end	Night	22% 17% 36% 22% 4	660
March	1st to 10th	Night	18% 15% 38% 22% 7%	800
	11th to 20th	Night	19% 15% 35% 24% 6% 1	800
	21st to end	Night	21% 12% 31% 27% 9% 1	880
April	1st to 10th	Night	23% 13% 33% 26% 6%	800
	11th to 20th	Night	23% 11% 30% 24% 11% 1	617
	21st to end	Night	24% 9% 29% 26% 12%	600
May	1st to 10th	Night	18% 5% 26% 36% 14% 2	600
	11th to 20th	Night	18% 4 23% 39% 14% 1	474
	21st to end	Night	14% 3 27% 37% 18%	433
June	1st to 10th	Night	15% 7% 27% 38% 11% 2	400
	11th to 20th	Night	12% 7% 23% 42% 17%	400
	21st to end	Night	15% 4 25% 37% 19%	400
July	1st to 10th	Night	9% 4 17% 51% 18% 1	380
	11th to 20th	Night	10% 3 24% 34% 26% 2	404
	21st to end	Night	9% 3 20% 43% 23% 1	624
August	1st to 10th	Night	13% 3 18% 37% 28% 2	567
	11th to 20th	Night	12% 3 13% 38% 28% 5%	564
	21st to end	Night	15% 5% 20% 34% 23% 3	632
September	1st to 10th	Night	12% 6% 24% 34% 19% 6%	760
	11th to 20th	Night	13% 5% 18% 37% 22% 5%	760
	21st to end	Night	18% 8% 23% 28% 18% 4	760
October	1st to 10th	Night	22% 7% 28% 28% 13% 2	760
	11th to 20th	Night	31% 14% 23% 25% 6% 2	760
	21st to end	Night	31% 16% 27% 22% 4	836
November	1st to 10th	Night	29% 13% 30% 20% 7% 1	780
	11th to 20th	Night	25% 18% 32% 18% 6% 1	800
	21st to end	Night	30% 17% 32% 17% 3	800
December	1st to 10th	Night	29% 21% 32% 13% 5%	800
	11th to 20th	Night	23% 21% 38% 15% 3	830
	21st to end	Night	30% 17% 35% 16% 3	1100

Page generated at 2025-07-03 01:30:11. Version ac07

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