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 2026-10-29.

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	15% 12% 4 9% 5% 4 4 3 5% 6% 31%	149957
	Night	14% 14% 5% 12% 6% 5% 4 3 4 6% 27%	142153
Transparency	Day	52% 5% 12% 20% 10% 1	153507
	Night	57% 6% 11% 17% 9% 1	146679
Seeing	Day	20% 13% 30% 24% 11% 3	17745
	Night	21% 12% 29% 27% 11% 1	26832

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	13% 20% 11% 19% 11% 4 4 2 3 4 10%	4112
	11th to 20th	Day	7% 24% 11% 26% 13% 6% 3 2 2 1 4	4918
	21st to end	Day	9% 16% 9% 21% 12% 9% 6% 3 4 4 6%	5780
February	1st to 10th	Day	12% 19% 9% 19% 10% 6% 4 3 4 4 11%	1890
	11th to 20th	Day	14% 15% 7% 18% 10% 6% 5% 3 4 4 14%	1843
	21st to end	Day	13% 20% 7% 15% 8% 7% 5% 3 4 4 15%	1675
March	1st to 10th	Day	15% 14% 5% 12% 6% 5% 4 3 4 5% 26%	4906
	11th to 20th	Day	11% 17% 8% 12% 5% 5% 5% 3 5% 6% 23%	5090
	21st to end	Day	18% 17% 6% 10% 5% 4 3 3 4 5% 25%	5586
April	1st to 10th	Day	19% 15% 4 9% 5% 4 4 3 4 6% 27%	2419
	11th to 20th	Day	20% 12% 3 7% 4 3 3 3 5% 5% 36%	2696
	21st to end	Day	20% 10% 4 7% 4 4 4 3 6% 6% 33%	2730
May	1st to 10th	Day	15% 9% 3 7% 4 4 5% 4 5% 8% 38%	7642
	11th to 20th	Day	15% 11% 3 7% 4 4 4 3 5% 7% 36%	7979
	21st to end	Day	19% 8% 2 5% 3 3 3 3 5% 7% 43%	9060
June	1st to 10th	Day	16% 7% 2 6% 4 4 5% 5% 5% 8% 39%	3060
	11th to 20th	Day	12% 5% 2 6% 4 4 5% 5% 6% 9% 41%	3150
	21st to end	Day	16% 7% 2 6% 4 5% 4 4 6% 7% 39%	3150
July	1st to 10th	Day	15% 7% 2 6% 4 4 4 4 6% 8% 40%	8879
	11th to 20th	Day	12% 4 2 4 3 3 4 4 5% 9% 50%	8630
	21st to end	Day	11% 5% 2 5% 4 4 4 3 6% 8% 47%	8340
August	1st to 10th	Day	16% 7% 2 6% 4 4 5% 4 6% 7% 39%	6014
	11th to 20th	Day	14% 6% 2 6% 3 4 4 4 6% 9% 41%	5951
	21st to end	Day	16% 7% 2 6% 4 4 4 4 6% 8% 37%	6528
September	1st to 10th	Day	14% 7% 2 7% 4 5% 4 5% 6% 7% 39%	2505
	11th to 20th	Day	13% 5% 3 6% 3 4 4 4 6% 8% 44%	2310
	21st to end	Day	17% 8% 2 7% 5% 5% 4 4 5% 6% 36%	2310
October	1st to 10th	Day	19% 8% 2 7% 4 4 4 4 6% 7% 33%	2121
	11th to 20th	Day	23% 13% 4 8% 5% 4 4 4 5% 5% 23%	2100
	21st to end	Day	27% 14% 4 10% 5% 4 3 3 4 5% 20%	2215
November	1st to 10th	Day	18% 20% 4 8% 6% 5% 4 3 5% 6% 22%	1797
	11th to 20th	Day	16% 20% 6% 11% 5% 5% 5% 3 5% 6% 18%	1680
	21st to end	Day	19% 26% 6% 12% 6% 4 4 3 4 5% 11%	1680
December	1st to 10th	Day	13% 30% 11% 15% 6% 4 3 2 3 4 10%	2680
	11th to 20th	Day	18% 25% 8% 17% 5% 4 4 3 3 4 11%	2978
	21st to end	Day	24% 20% 7% 16% 7% 4 3 2 3 4 9%	3553
January	1st to 10th	Night	12% 20% 11% 26% 7% 4 3 2 3 4 9%	8797
	11th to 20th	Night	9% 21% 11% 24% 11% 6% 4 2 3 3 6%	7980
	21st to end	Night	9% 17% 10% 19% 13% 8% 5% 3 3 4 10%	8401
February	1st to 10th	Night	12% 19% 7% 18% 9% 6% 5% 3 4 3 13%	2730
	11th to 20th	Night	12% 17% 8% 16% 8% 6% 4 4 3 5% 17%	2663
	21st to end	Night	13% 16% 6% 14% 7% 5% 5% 4 4 5% 20%	2128
March	1st to 10th	Night	14% 14% 6% 10% 5% 4 4 3 5% 7% 27%	5141
	11th to 20th	Night	9% 16% 5% 9% 5% 4 5% 4 5% 7% 30%	5089
	21st to end	Night	20% 12% 7% 9% 4 4 4 3 4 5% 29%	5588
April	1st to 10th	Night	19% 13% 3 10% 5% 4 4 3 5% 6% 29%	2200
	11th to 20th	Night	18% 11% 3 6% 4 4 4 3 5% 6% 36%	1892
	21st to end	Night	19% 11% 4 8% 4 4 3 3 4 6% 33%	1890
May	1st to 10th	Night	15% 8% 3 7% 5% 4 4 4 5% 8% 38%	5257
	11th to 20th	Night	18% 7% 2 6% 4 3 4 3 5% 6% 42%	4877
	21st to end	Night	18% 6% 2 5% 3 3 4 4 5% 6% 44%	5114
June	1st to 10th	Night	14% 8% 2 6% 5% 4 4 3 6% 7% 41%	1555
	11th to 20th	Night	11% 6% 2 6% 5% 5% 5% 5% 6% 9% 41%	1470
	21st to end	Night	14% 6% 3 6% 4 4 4 4 7% 8% 41%	1470
July	1st to 10th	Night	12% 8% 3 7% 4 3 4 3 5% 8% 44%	4110
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 5% 8% 50%	4333
	21st to end	Night	11% 6% 2 5% 3 3 4 4 6% 8% 48%	5737
August	1st to 10th	Night	13% 8% 3 7% 4 4 4 3 5% 6% 42%	4135
	11th to 20th	Night	15% 6% 2 6% 4 3 4 3 5% 6% 47%	4095
	21st to end	Night	17% 8% 3 7% 4 4 4 3 5% 7% 38%	4550
September	1st to 10th	Night	11% 6% 2 5% 5% 4 3 4 6% 8% 46%	2110
	11th to 20th	Night	12% 5% 2 5% 3 3 4 4 6% 8% 49%	2310
	21st to end	Night	16% 8% 2 7% 5% 5% 4 3 5% 6% 37%	2310
October	1st to 10th	Night	18% 8% 3 7% 5% 5% 4 3 6% 7% 35%	2499
	11th to 20th	Night	24% 14% 3 8% 5% 4 4 3 4 5% 25%	2520
	21st to end	Night	24% 15% 4 8% 6% 4 3 4 4 5% 23%	2797
November	1st to 10th	Night	18% 19% 4 8% 6% 4 4 3 5% 5% 24%	2719
	11th to 20th	Night	17% 19% 5% 11% 6% 5% 5% 4 4 6% 19%	2940
	21st to end	Night	21% 22% 7% 11% 6% 4 4 3 5% 5% 13%	2940
December	1st to 10th	Night	15% 26% 9% 16% 6% 5% 4 3 4 5% 8%	4720
	11th to 20th	Night	11% 24% 9% 19% 6% 5% 4 3 3 4 11%	5419
	21st to end	Night	20% 23% 7% 17% 7% 6% 4 2 3 3 8%	7667

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	77% 6% 9% 6% 3	4113
	11th to 20th	Day	89% 4 3 3 1	4951
	21st to end	Day	79% 6% 7% 5% 2	5780
February	1st to 10th	Day	77% 6% 8% 8% 2	1890
	11th to 20th	Day	73% 7% 9% 7% 4	1852
	21st to end	Day	71% 5% 9% 12% 3	1675
March	1st to 10th	Day	59% 6% 14% 12% 9%	4909
	11th to 20th	Day	61% 5% 11% 16% 5% 1	5090
	21st to end	Day	59% 5% 11% 17% 7% 1	5586
April	1st to 10th	Day	58% 5% 11% 17% 9%	2419
	11th to 20th	Day	49% 4 9% 22% 15% 1	2696
	21st to end	Day	49% 6% 12% 19% 11% 2	2730
May	1st to 10th	Day	42% 6% 13% 21% 14% 3	7651
	11th to 20th	Day	45% 6% 11% 20% 17% 1	7983
	21st to end	Day	42% 4 9% 25% 16% 3	9061
June	1st to 10th	Day	41% 8% 10% 23% 17% 1	3060
	11th to 20th	Day	38% 7% 13% 24% 17% 1	3150
	21st to end	Day	42% 7% 12% 25% 13% 2	3150
July	1st to 10th	Day	40% 4 17% 23% 14% 1	8806
	11th to 20th	Day	30% 5% 12% 37% 16% 1	8549
	21st to end	Day	34% 5% 13% 32% 15% 1	8156
August	1st to 10th	Day	41% 6% 16% 21% 15% 2	6001
	11th to 20th	Day	38% 5% 21% 27% 9%	5990
	21st to end	Day	43% 5% 16% 27% 9%	6528
September	1st to 10th	Day	42% 7% 13% 24% 12% 1	2505
	11th to 20th	Day	36% 6% 16% 29% 12%	2310
	21st to end	Day	48% 7% 11% 22% 11% 1	2310
October	1st to 10th	Day	43% 7% 13% 26% 11% 1	3394
	11th to 20th	Day	55% 5% 10% 20% 9% 1	3340
	21st to end	Day	60% 5% 13% 17% 5%	3504
November	1st to 10th	Day	63% 7% 11% 14% 5%	1797
	11th to 20th	Day	67% 7% 12% 8% 5%	1680
	21st to end	Day	76% 7% 10% 6% 1	1680
December	1st to 10th	Day	79% 5% 10% 4 1	2680
	11th to 20th	Day	77% 7% 8% 7% 2	2978
	21st to end	Day	80% 6% 7% 5% 2	3553
January	1st to 10th	Night	79% 6% 8% 6% 2	8797
	11th to 20th	Night	84% 5% 5% 5% 2	8022
	21st to end	Night	76% 6% 8% 6% 4	8401
February	1st to 10th	Night	75% 5% 8% 9% 2	2730
	11th to 20th	Night	69% 6% 10% 12% 4	2665
	21st to end	Night	65% 7% 11% 11% 6%	2128
March	1st to 10th	Night	55% 5% 15% 14% 10% 1	5151
	11th to 20th	Night	52% 6% 17% 17% 8% 1	5090
	21st to end	Night	57% 5% 10% 15% 11% 1	5588
April	1st to 10th	Night	55% 5% 10% 18% 11% 1	2200
	11th to 20th	Night	49% 5% 8% 20% 17% 1	1892
	21st to end	Night	53% 5% 8% 18% 14% 2	1890
May	1st to 10th	Night	44% 6% 10% 21% 15% 5%	5264
	11th to 20th	Night	42% 6% 10% 23% 18% 1	4878
	21st to end	Night	41% 5% 8% 27% 17% 2	5115
June	1st to 10th	Night	40% 6% 11% 21% 20% 3	1555
	11th to 20th	Night	37% 7% 13% 25% 18% 1	1470
	21st to end	Night	39% 8% 12% 26% 13% 2	1470
July	1st to 10th	Night	39% 4 16% 23% 15% 3	4075
	11th to 20th	Night	32% 5% 12% 33% 17% 1	4291
	21st to end	Night	34% 4 11% 31% 18% 1	5606
August	1st to 10th	Night	42% 4 12% 24% 17% 1	4124
	11th to 20th	Night	37% 6% 17% 29% 10% 1	4122
	21st to end	Night	46% 5% 13% 26% 10% 1	4550
September	1st to 10th	Night	34% 8% 14% 30% 13% 1	2110
	11th to 20th	Night	33% 6% 15% 30% 15%	2310
	21st to end	Night	46% 7% 13% 23% 10% 1	2310
October	1st to 10th	Night	39% 8% 10% 26% 16% 1	4006
	11th to 20th	Night	53% 5% 14% 18% 11%	4019
	21st to end	Night	53% 6% 15% 19% 6%	4445
November	1st to 10th	Night	61% 7% 11% 17% 5%	2719
	11th to 20th	Night	66% 8% 13% 9% 4 1	2940
	21st to end	Night	73% 7% 12% 7% 1	2940
December	1st to 10th	Night	78% 6% 11% 3 1	4720
	11th to 20th	Night	77% 7% 9% 7% 1	5419
	21st to end	Night	83% 4 7% 5% 1	7667

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	22% 21% 37% 15% 4 1	223
	11th to 20th	Day	19% 25% 35% 15% 4	330
	21st to end	Day	26% 20% 29% 21% 4	363
February	1st to 10th	Day	22% 27% 32% 16% 3	330
	11th to 20th	Day	23% 24% 36% 15% 2	330
	21st to end	Day	25% 27% 34% 13% 1	273
March	1st to 10th	Day	23% 17% 37% 17% 6%	477
	11th to 20th	Day	24% 18% 34% 18% 6%	540
	21st to end	Day	28% 16% 30% 20% 5% 1	594
April	1st to 10th	Day	26% 16% 32% 18% 7% 1	540
	11th to 20th	Day	30% 15% 27% 16% 8% 5%	532
	21st to end	Day	27% 11% 31% 21% 9% 1	540
May	1st to 10th	Day	21% 11% 33% 24% 8% 2	543
	11th to 20th	Day	18% 9% 31% 26% 14% 3	567
	21st to end	Day	18% 10% 29% 25% 15% 3	617
June	1st to 10th	Day	16% 10% 32% 27% 13% 2	690
	11th to 20th	Day	14% 10% 34% 30% 10% 3	780
	21st to end	Day	18% 8% 33% 27% 11% 3	780
July	1st to 10th	Day	12% 8% 26% 34% 17% 3	771
	11th to 20th	Day	13% 8% 31% 27% 15% 5%	731
	21st to end	Day	12% 5% 27% 36% 15% 5%	620
August	1st to 10th	Day	12% 6% 24% 34% 16% 8%	566
	11th to 20th	Day	15% 5% 20% 33% 20% 7%	559
	21st to end	Day	15% 10% 23% 29% 17% 6%	627
September	1st to 10th	Day	15% 10% 25% 28% 16% 7%	570
	11th to 20th	Day	11% 5% 22% 29% 20% 12%	570
	21st to end	Day	15% 10% 27% 26% 18% 4	570
October	1st to 10th	Day	21% 15% 26% 21% 13% 4	570
	11th to 20th	Day	22% 22% 32% 19% 4 1	570
	21st to end	Day	30% 18% 29% 18% 5%	550
November	1st to 10th	Day	33% 15% 29% 18% 5%	300
	11th to 20th	Day	25% 24% 31% 15% 3 1	220
	21st to end	Day	32% 19% 33% 15% 2	220
December	1st to 10th	Day	28% 23% 30% 15% 4	220
	11th to 20th	Day	30% 26% 28% 11% 4	220
	21st to end	Day	36% 20% 30% 9% 5%	242
January	1st to 10th	Night	22% 20% 33% 21% 4	1050
	11th to 20th	Night	25% 19% 31% 19% 6% 1	961
	21st to end	Night	18% 15% 34% 26% 7% 1	924
February	1st to 10th	Night	20% 19% 36% 22% 4	840
	11th to 20th	Night	20% 16% 35% 24% 6%	823
	21st to end	Night	22% 17% 36% 21% 4	692
March	1st to 10th	Night	19% 15% 38% 22% 7%	840
	11th to 20th	Night	20% 15% 35% 23% 6% 1	840
	21st to end	Night	21% 13% 31% 26% 8% 1	924
April	1st to 10th	Night	23% 13% 33% 25% 6%	840
	11th to 20th	Night	23% 11% 30% 25% 10% 1	648
	21st to end	Night	23% 9% 28% 27% 12%	630
May	1st to 10th	Night	18% 6% 26% 35% 14% 1	630
	11th to 20th	Night	19% 5% 23% 38% 14% 1	498
	21st to end	Night	15% 4 27% 37% 17%	455
June	1st to 10th	Night	15% 7% 26% 38% 11% 2	420
	11th to 20th	Night	12% 7% 25% 40% 16%	420
	21st to end	Night	15% 3 25% 39% 19%	420
July	1st to 10th	Night	10% 4 17% 51% 17% 1	410
	11th to 20th	Night	11% 4 24% 35% 25% 2	448
	21st to end	Night	9% 4 20% 44% 22% 1	690
August	1st to 10th	Night	12% 3 19% 38% 27% 2	627
	11th to 20th	Night	12% 3 14% 40% 27% 4	624
	21st to end	Night	16% 6% 19% 34% 23% 3	698
September	1st to 10th	Night	12% 6% 23% 34% 20% 5%	840
	11th to 20th	Night	13% 5% 17% 38% 22% 5%	840
	21st to end	Night	17% 8% 23% 28% 20% 4	840
October	1st to 10th	Night	21% 7% 28% 29% 13% 1	840
	11th to 20th	Night	31% 14% 23% 24% 6% 2	840
	21st to end	Night	30% 15% 27% 24% 5%	913
November	1st to 10th	Night	29% 14% 30% 20% 6% 1	820
	11th to 20th	Night	26% 18% 31% 18% 6% 1	840
	21st to end	Night	32% 17% 32% 17% 3	840
December	1st to 10th	Night	28% 22% 32% 14% 4	840
	11th to 20th	Night	23% 21% 38% 15% 3	872
	21st to end	Night	30% 17% 34% 15% 3	1155

Page generated at 2026-10-26 04:37:51. Version ac07

Copyright © 2026 Attilla Danko.