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 2024-11-03.

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%	101542
	Night	15% 14% 5% 11% 6% 4 4 3 4 6% 27%	97434
Transparency	Day	52% 6% 12% 18% 10% 1	101300
	Night	58% 6% 11% 16% 8% 1	97296
Seeing	Day	19% 13% 29% 25% 11% 3	15131
	Night	21% 12% 29% 27% 11% 1	24289

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% 23% 13% 19% 10% 4 3 2 3 3 7%	2212
	11th to 20th	Day	10% 22% 10% 23% 13% 6% 4 2 3 1 6%	2654
	21st to end	Day	16% 23% 11% 17% 7% 6% 4 3 3 3 8%	3124
February	1st to 10th	Day	12% 20% 9% 18% 10% 5% 4 3 4 4 11%	1710
	11th to 20th	Day	14% 15% 8% 17% 10% 6% 5% 3 5% 5% 15%	1663
	21st to end	Day	13% 20% 7% 14% 8% 6% 5% 3 4 4 16%	1519
March	1st to 10th	Day	16% 17% 5% 10% 6% 4 3 3 4 5% 27%	3341
	11th to 20th	Day	11% 19% 10% 12% 5% 4 5% 3 4 5% 23%	3480
	21st to end	Day	15% 15% 6% 9% 6% 4 4 3 5% 6% 28%	3815
April	1st to 10th	Day	19% 15% 4 8% 5% 4 4 3 4 6% 27%	2189
	11th to 20th	Day	19% 12% 3 7% 4 3 3 3 5% 5% 36%	2436
	21st to end	Day	21% 10% 4 6% 4 4 4 3 6% 6% 33%	2470
May	1st to 10th	Day	17% 9% 3 7% 4 4 4 3 5% 7% 38%	4108
	11th to 20th	Day	15% 8% 3 7% 5% 4 5% 4 6% 8% 37%	4266
	21st to end	Day	15% 6% 2 5% 4 3 4 3 6% 8% 45%	4837
June	1st to 10th	Day	16% 7% 2 6% 4 4 5% 5% 6% 7% 38%	2768
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 5% 6% 9% 42%	2850
	21st to end	Day	16% 7% 2 6% 4 5% 4 4 5% 7% 39%	2850
July	1st to 10th	Day	15% 6% 3 6% 4 5% 5% 4 7% 8% 36%	4760
	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 3 3 3 6% 17%	2028
November	1st to 10th	Day	17% 21% 4 8% 5% 5% 4 3 5% 6% 22%	1641
	11th to 20th	Day	16% 21% 6% 11% 5% 5% 5% 3 5% 6% 18%	1520
	21st to end	Day	19% 24% 6% 12% 6% 4 4 3 5% 5% 12%	1520
December	1st to 10th	Day	14% 31% 9% 16% 7% 4 3 3 3 3 7%	1520
	11th to 20th	Day	17% 24% 8% 16% 6% 4 4 3 4 4 10%	1846
	21st to end	Day	25% 23% 8% 16% 5% 4 3 2 4 4 7%	2431
January	1st to 10th	Night	14% 26% 11% 23% 7% 4 3 2 2 3 5%	4742
	11th to 20th	Night	14% 16% 10% 25% 11% 6% 4 2 3 3 6%	4308
	21st to end	Night	14% 21% 11% 16% 7% 6% 4 3 3 4 9%	4532
February	1st to 10th	Night	13% 19% 7% 19% 9% 6% 5% 3 4 3 13%	2470
	11th to 20th	Night	12% 17% 8% 15% 8% 6% 4 4 4 5% 18%	2403
	21st to end	Night	14% 16% 6% 13% 7% 5% 5% 4 4 4 21%	1932
March	1st to 10th	Night	13% 14% 5% 9% 6% 4 4 3 4 7% 32%	3486
	11th to 20th	Night	10% 18% 6% 10% 5% 3 3 3 4 6% 32%	3479
	21st to end	Night	13% 10% 7% 10% 5% 4 4 3 5% 6% 31%	3817
April	1st to 10th	Night	19% 13% 3 9% 5% 4 4 3 5% 6% 29%	1990
	11th to 20th	Night	18% 11% 3 6% 4 3 4 3 5% 6% 37%	1710
	21st to end	Night	20% 12% 4 9% 4 4 3 3 4 6% 32%	1710
May	1st to 10th	Night	15% 7% 3 6% 5% 4 4 4 5% 8% 39%	2833
	11th to 20th	Night	16% 6% 2 6% 5% 4 4 3 5% 7% 41%	2623
	21st to end	Night	11% 6% 3 6% 4 3 4 4 5% 6% 48%	2738
June	1st to 10th	Night	14% 8% 2 7% 5% 4 4 3 6% 7% 39%	1407
	11th to 20th	Night	11% 6% 2 5% 5% 4 5% 5% 6% 9% 42%	1330
	21st to end	Night	14% 6% 3 6% 4 4 4 4 7% 8% 41%	1330
July	1st to 10th	Night	10% 7% 4 7% 4 3 3 3 5% 7% 46%	2210
	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% 20% 4 8% 6% 4 4 3 5% 5% 24%	2480
	11th to 20th	Night	17% 18% 5% 11% 6% 5% 6% 4 4 6% 19%	2660
	21st to end	Night	21% 20% 6% 10% 6% 4 4 3 5% 6% 14%	2660
December	1st to 10th	Night	18% 28% 9% 13% 5% 4 4 3 3 4 8%	2660
	11th to 20th	Night	12% 24% 9% 18% 6% 5% 4 4 3 4 11%	3329
	21st to end	Night	22% 22% 8% 18% 6% 5% 3 3 3 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	59% 6% 13% 14% 8% 1	3344
	11th to 20th	Day	62% 6% 10% 16% 5% 1	3480
	21st to end	Day	53% 7% 15% 16% 9% 1	3815
April	1st to 10th	Day	57% 5% 11% 17% 9%	2189
	11th to 20th	Day	49% 5% 9% 21% 15% 1	2436
	21st to end	Day	50% 6% 11% 18% 12% 2	2470
May	1st to 10th	Day	43% 7% 12% 20% 16% 1	4120
	11th to 20th	Day	42% 9% 16% 22% 12% 1	4270
	21st to end	Day	37% 6% 12% 21% 18% 5%	4837
June	1st to 10th	Day	42% 8% 11% 23% 15% 1	2768
	11th to 20th	Day	37% 7% 13% 24% 18% 1	2850
	21st to end	Day	42% 7% 13% 24% 13% 2	2850
July	1st to 10th	Day	42% 5% 17% 19% 15% 2	4686
	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	51% 7% 12% 19% 10% 1	1919
	11th to 20th	Day	64% 7% 10% 13% 5% 1	1900
	21st to end	Day	70% 5% 10% 12% 3	2028
November	1st to 10th	Day	63% 7% 11% 13% 5%	1641
	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	52% 6% 16% 18% 9%	3496
	11th to 20th	Night	51% 7% 14% 17% 9% 2	3480
	21st to end	Night	52% 7% 12% 18% 10% 1	3817
April	1st to 10th	Night	55% 5% 10% 19% 11% 1	1990
	11th to 20th	Night	48% 5% 8% 20% 18% 1	1710
	21st to end	Night	54% 6% 8% 16% 15% 2	1710
May	1st to 10th	Night	42% 7% 12% 19% 17% 3	2840
	11th to 20th	Night	41% 7% 12% 22% 16% 2	2624
	21st to end	Night	35% 7% 12% 23% 20% 3	2739
June	1st to 10th	Night	42% 7% 11% 21% 17% 2	1407
	11th to 20th	Night	36% 7% 13% 25% 18% 1	1330
	21st to end	Night	38% 8% 12% 26% 14% 2	1330
July	1st to 10th	Night	38% 4 13% 22% 17% 5%	2175
	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	49% 8% 10% 20% 12% 1	2261
	11th to 20th	Night	61% 7% 12% 15% 6%	2280
	21st to end	Night	67% 6% 10% 12% 5%	2565
November	1st to 10th	Night	61% 7% 10% 17% 5%	2480
	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	24% 15% 32% 22% 6% 1	506
April	1st to 10th	Day	23% 15% 33% 20% 8%	460
	11th to 20th	Day	29% 15% 27% 16% 8% 5%	452
	21st to end	Day	28% 11% 30% 21% 9% 1	460
May	1st to 10th	Day	21% 9% 30% 27% 10% 3	463
	11th to 20th	Day	17% 8% 29% 28% 15% 3	487
	21st to end	Day	16% 8% 27% 28% 17% 4	529
June	1st to 10th	Day	14% 10% 31% 28% 14% 2	598
	11th to 20th	Day	12% 8% 33% 32% 11% 3	680
	21st to end	Day	18% 8% 31% 29% 12% 3	680
July	1st to 10th	Day	12% 7% 25% 34% 18% 3	671
	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	29% 17% 29% 19% 6%	252
	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	19% 12% 32% 27% 9% 1	836
April	1st to 10th	Night	23% 12% 33% 26% 6%	760
	11th to 20th	Night	23% 11% 30% 24% 11% 1	586
	21st to end	Night	24% 9% 28% 26% 13%	570
May	1st to 10th	Night	18% 5% 26% 35% 14% 2	570
	11th to 20th	Night	19% 4 21% 41% 14% 1	450
	21st to end	Night	12% 4 27% 37% 19%	411
June	1st to 10th	Night	15% 7% 26% 38% 11% 2	380
	11th to 20th	Night	12% 6% 23% 42% 17%	380
	21st to end	Night	14% 4 24% 37% 20%	380
July	1st to 10th	Night	9% 4 17% 51% 18% 1	370
	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	749
	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 2024-10-31 03:39:21. Version ac07

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