Barry's Bay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Barry's Bay clear sky chart from 2005-11-06 to 2025-09-19.

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% 11% 4 9% 5% 5% 4 3 5% 6% 31%	126756
	Night	15% 12% 4 10% 6% 5% 4 3 5% 6% 29%	122261
Transparency	Day	53% 5% 10% 20% 10% 1	130286
	Night	54% 6% 11% 19% 9% 1	126818
Seeing	Day	23% 18% 31% 18% 8% 2	15460
	Night	22% 15% 31% 23% 8% 1	24606

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% 16% 7% 15% 10% 7% 5% 4 4 4 16%	3597
	11th to 20th	Day	9% 16% 7% 18% 9% 6% 4 3 5% 6% 16%	3570
	21st to end	Day	12% 20% 8% 15% 7% 5% 4 2 3 4 20%	4356
February	1st to 10th	Day	10% 16% 6% 16% 9% 5% 5% 4 4 5% 21%	1800
	11th to 20th	Day	11% 15% 7% 13% 6% 6% 5% 3 5% 5% 24%	1753
	21st to end	Day	15% 16% 5% 10% 7% 6% 5% 4 5% 5% 22%	1565
March	1st to 10th	Day	16% 15% 5% 12% 6% 4 4 3 4 6% 25%	4740
	11th to 20th	Day	9% 14% 5% 11% 6% 5% 5% 4 6% 6% 27%	4980
	21st to end	Day	16% 13% 4 9% 5% 4 3 2 3 4 36%	5592
April	1st to 10th	Day	20% 14% 3 8% 5% 4 4 3 4 5% 29%	2400
	11th to 20th	Day	21% 12% 3 7% 4 4 3 3 4 5% 35%	2382
	21st to end	Day	21% 11% 3 7% 5% 3 5% 3 4 5% 33%	2600
May	1st to 10th	Day	20% 10% 3 7% 5% 4 4 3 5% 6% 33%	6252
	11th to 20th	Day	15% 10% 4 8% 5% 4 4 3 5% 7% 36%	6318
	21st to end	Day	20% 9% 3 8% 5% 5% 4 3 4 6% 34%	6949
June	1st to 10th	Day	20% 10% 3 7% 5% 5% 5% 3 5% 7% 31%	2800
	11th to 20th	Day	15% 6% 2 7% 4 4 5% 4 6% 9% 37%	2800
	21st to end	Day	16% 8% 3 7% 5% 5% 5% 5% 6% 7% 34%	2800
July	1st to 10th	Day	15% 7% 3 7% 5% 5% 5% 4 7% 10% 34%	6360
	11th to 20th	Day	11% 6% 2 6% 4 5% 5% 4 6% 7% 45%	6360
	21st to end	Day	9% 5% 2 6% 4 4 4 4 6% 9% 46%	6926
August	1st to 10th	Day	14% 7% 3 9% 5% 5% 5% 4 5% 7% 34%	4283
	11th to 20th	Day	17% 7% 3 6% 4 5% 5% 4 7% 9% 34%	4174
	21st to end	Day	10% 5% 2 6% 5% 5% 6% 5% 7% 9% 40%	4411
September	1st to 10th	Day	14% 7% 2 6% 4 5% 5% 4 6% 8% 40%	2400
	11th to 20th	Day	13% 7% 2 6% 5% 4 3 3 5% 7% 45%	2376
	21st to end	Day	18% 9% 3 7% 5% 4 5% 3 4 7% 35%	1986
October	1st to 10th	Day	19% 10% 3 8% 5% 4 4 4 4 6% 34%	1900
	11th to 20th	Day	22% 15% 4 9% 4 4 4 4 4 5% 25%	1900
	21st to end	Day	26% 15% 4 9% 5% 5% 4 3 4 5% 21%	2024
November	1st to 10th	Day	15% 13% 4 9% 4 4 4 3 4 7% 32%	1656
	11th to 20th	Day	15% 17% 6% 10% 7% 4 4 3 5% 5% 25%	1600
	21st to end	Day	20% 20% 6% 12% 7% 5% 4 3 4 5% 15%	1600
December	1st to 10th	Day	16% 24% 9% 14% 7% 5% 4 3 4 4 10%	2600
	11th to 20th	Day	15% 20% 7% 14% 6% 4 3 3 3 3 21%	2986
	21st to end	Day	19% 21% 7% 14% 6% 2 4 2 3 4 18%	3960
January	1st to 10th	Night	12% 17% 9% 18% 9% 5% 4 3 3 4 16%	6349
	11th to 20th	Night	8% 15% 6% 17% 9% 8% 7% 4 5% 5% 16%	6315
	21st to end	Night	11% 17% 9% 15% 7% 7% 4 3 4 4 18%	6582
February	1st to 10th	Night	11% 16% 6% 14% 8% 6% 5% 3 5% 6% 19%	2600
	11th to 20th	Night	11% 15% 6% 11% 6% 6% 6% 3 5% 5% 27%	2533
	21st to end	Night	11% 16% 5% 12% 6% 6% 4 4 5% 6% 26%	2065
March	1st to 10th	Night	17% 15% 4 11% 6% 4 4 3 4 5% 28%	5098
	11th to 20th	Night	9% 13% 4 10% 6% 6% 6% 5% 7% 8% 26%	4979
	21st to end	Night	14% 12% 4 10% 6% 4 4 3 5% 6% 30%	5339
April	1st to 10th	Night	19% 13% 4 8% 6% 4 4 4 3 5% 31%	2000
	11th to 20th	Night	18% 12% 3 6% 4 4 3 3 4 6% 37%	1975
	21st to end	Night	19% 11% 3 8% 5% 4 4 4 4 4 32%	1810
May	1st to 10th	Night	21% 9% 3 7% 4 4 5% 3 6% 6% 32%	3686
	11th to 20th	Night	14% 7% 3 7% 4 4 3 3 5% 7% 42%	3575
	21st to end	Night	18% 8% 3 7% 5% 4 4 3 5% 6% 36%	3926
June	1st to 10th	Night	16% 8% 3 7% 5% 4 5% 5% 5% 7% 36%	1600
	11th to 20th	Night	15% 5% 2 6% 3 4 5% 3 5% 8% 44%	1600
	21st to end	Night	16% 8% 2 6% 5% 5% 5% 3 7% 6% 37%	1600
July	1st to 10th	Night	13% 7% 3 6% 5% 5% 5% 4 6% 8% 38%	3600
	11th to 20th	Night	12% 6% 2 5% 4 3 4 4 5% 7% 47%	3600
	21st to end	Night	9% 5% 2 5% 4 3 4 4 6% 8% 50%	3926
August	1st to 10th	Night	11% 5% 2 7% 4 5% 4 5% 6% 8% 44%	2849
	11th to 20th	Night	15% 6% 2 6% 4 4 4 4 5% 7% 44%	2875
	21st to end	Night	13% 5% 2 6% 4 4 5% 4 6% 8% 44%	3453
September	1st to 10th	Night	12% 5% 2 5% 5% 4 4 4 5% 7% 48%	2000
	11th to 20th	Night	13% 6% 2 5% 3 4 3 3 4 7% 50%	1981
	21st to end	Night	16% 8% 3 6% 4 4 5% 3 4 6% 41%	2190
October	1st to 10th	Night	20% 8% 3 6% 3 3 4 3 4 6% 40%	2280
	11th to 20th	Night	20% 12% 3 8% 5% 4 4 4 4 6% 29%	2280
	21st to end	Night	22% 15% 4 9% 6% 4 4 3 5% 5% 25%	2574
November	1st to 10th	Night	16% 13% 4 9% 5% 4 4 3 5% 6% 31%	2637
	11th to 20th	Night	16% 14% 5% 11% 7% 5% 4 3 5% 6% 25%	2800
	21st to end	Night	18% 18% 5% 13% 6% 5% 4 3 4 5% 19%	2800
December	1st to 10th	Night	16% 21% 8% 15% 6% 5% 4 3 4 5% 12%	4580
	11th to 20th	Night	17% 19% 7% 12% 5% 5% 3 3 3 5% 21%	5208
	21st to end	Night	22% 19% 5% 14% 7% 4 4 2 3 4 16%	6996

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	70% 6% 9% 9% 7%	3598
	11th to 20th	Day	69% 5% 8% 9% 8% 1	3600
	21st to end	Day	69% 4 6% 11% 8% 1	4356
February	1st to 10th	Day	66% 5% 8% 15% 6% 1	1800
	11th to 20th	Day	61% 5% 11% 13% 8% 1	1762
	21st to end	Day	63% 6% 8% 12% 10% 1	1565
March	1st to 10th	Day	61% 4 9% 11% 14% 2	4743
	11th to 20th	Day	55% 4 15% 15% 8% 2	4980
	21st to end	Day	53% 4 6% 19% 16% 3	5592
April	1st to 10th	Day	57% 5% 6% 18% 11% 3	2400
	11th to 20th	Day	53% 4 7% 21% 14% 1	2382
	21st to end	Day	54% 5% 7% 18% 15% 3	2600
May	1st to 10th	Day	52% 5% 8% 20% 10% 5%	6263
	11th to 20th	Day	47% 7% 9% 21% 15% 1	6322
	21st to end	Day	51% 5% 9% 19% 13% 2	6949
June	1st to 10th	Day	53% 6% 10% 20% 12% 1	2800
	11th to 20th	Day	43% 7% 12% 24% 13% 2	2800
	21st to end	Day	47% 8% 12% 20% 12% 1	2800
July	1st to 10th	Day	44% 5% 14% 27% 9% 1	6290
	11th to 20th	Day	36% 5% 13% 31% 14%	6285
	21st to end	Day	34% 5% 14% 35% 11%	6728
August	1st to 10th	Day	48% 6% 13% 23% 9%	4269
	11th to 20th	Day	45% 6% 15% 26% 7% 1	4213
	21st to end	Day	37% 8% 12% 32% 10% 1	4411
September	1st to 10th	Day	41% 7% 13% 27% 11% 1	2400
	11th to 20th	Day	39% 6% 11% 31% 13%	2376
	21st to end	Day	49% 6% 12% 23% 10%	1986
October	1st to 10th	Day	51% 5% 10% 27% 7%	3160
	11th to 20th	Day	54% 4 11% 21% 10%	3140
	21st to end	Day	61% 5% 13% 15% 4	3314
November	1st to 10th	Day	52% 6% 14% 21% 7%	1656
	11th to 20th	Day	61% 7% 11% 12% 8% 1	1600
	21st to end	Day	71% 6% 10% 8% 5% 1	1600
December	1st to 10th	Day	78% 5% 8% 7% 2	2600
	11th to 20th	Day	68% 6% 5% 12% 8%	2986
	21st to end	Day	73% 3 6% 14% 5%	3960
January	1st to 10th	Night	73% 5% 8% 10% 4	6349
	11th to 20th	Night	68% 6% 9% 10% 6%	6360
	21st to end	Night	68% 5% 6% 9% 10% 1	6582
February	1st to 10th	Night	64% 6% 9% 14% 6% 1	2600
	11th to 20th	Night	60% 5% 11% 17% 7% 1	2535
	21st to end	Night	57% 6% 9% 19% 8% 1	2065
March	1st to 10th	Night	60% 4 8% 14% 10% 4	5108
	11th to 20th	Night	52% 8% 16% 16% 8% 1	4980
	21st to end	Night	52% 5% 9% 19% 13% 2	5339
April	1st to 10th	Night	56% 4 8% 18% 11% 2	2000
	11th to 20th	Night	50% 5% 7% 24% 13% 1	1975
	21st to end	Night	54% 5% 8% 16% 15% 2	1810
May	1st to 10th	Night	50% 6% 9% 20% 10% 4	3692
	11th to 20th	Night	40% 8% 14% 21% 15% 3	3576
	21st to end	Night	48% 7% 12% 20% 12% 1	3927
June	1st to 10th	Night	45% 8% 12% 22% 13% 1	1600
	11th to 20th	Night	39% 6% 11% 27% 15% 1	1600
	21st to end	Night	46% 7% 14% 20% 13% 1	1600
July	1st to 10th	Night	42% 5% 17% 22% 12% 1	3560
	11th to 20th	Night	36% 5% 14% 33% 12%	3552
	21st to end	Night	32% 6% 12% 38% 12%	3809
August	1st to 10th	Night	37% 7% 16% 27% 13% 1	2839
	11th to 20th	Night	39% 6% 17% 29% 9% 1	2902
	21st to end	Night	36% 7% 15% 30% 10% 2	3453
September	1st to 10th	Night	36% 7% 14% 30% 13% 1	2000
	11th to 20th	Night	36% 5% 13% 34% 11%	1981
	21st to end	Night	45% 6% 11% 28% 10%	2190
October	1st to 10th	Night	40% 5% 12% 29% 14%	3800
	11th to 20th	Night	50% 5% 15% 19% 11%	3779
	21st to end	Night	54% 6% 18% 17% 6%	4234
November	1st to 10th	Night	54% 6% 14% 18% 8%	2637
	11th to 20th	Night	61% 6% 10% 16% 7% 1	2800
	21st to end	Night	68% 7% 10% 12% 3	2800
December	1st to 10th	Night	74% 5% 11% 8% 2	4580
	11th to 20th	Night	66% 5% 7% 12% 10% 1	5208
	21st to end	Night	73% 3 6% 11% 7%	6996

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	19% 26% 38% 15% 3 1	200
	11th to 20th	Day	27% 15% 38% 17% 3 1	200
	21st to end	Day	24% 22% 33% 17% 4	307
February	1st to 10th	Day	27% 32% 31% 7% 2 1	300
	11th to 20th	Day	27% 29% 39% 6%	300
	21st to end	Day	31% 23% 33% 12% 1	329
March	1st to 10th	Day	27% 24% 33% 14% 2	500
	11th to 20th	Day	26% 19% 34% 16% 4 1	500
	21st to end	Day	31% 23% 31% 11% 4 1	550
April	1st to 10th	Day	30% 23% 29% 12% 5% 1	500
	11th to 20th	Day	36% 21% 21% 13% 7% 2	492
	21st to end	Day	31% 19% 32% 12% 6% 1	500
May	1st to 10th	Day	25% 19% 29% 17% 8% 2	503
	11th to 20th	Day	20% 18% 31% 20% 8% 2	527
	21st to end	Day	19% 19% 31% 20% 9% 2	573
June	1st to 10th	Day	24% 14% 37% 18% 7% 1	530
	11th to 20th	Day	18% 16% 33% 21% 10% 2	530
	21st to end	Day	20% 15% 35% 20% 9% 2	530
July	1st to 10th	Day	11% 10% 34% 34% 9% 2	525
	11th to 20th	Day	14% 12% 36% 24% 12% 2	524
	21st to end	Day	13% 11% 36% 28% 10% 3	576
August	1st to 10th	Day	15% 8% 31% 30% 12% 4	526
	11th to 20th	Day	15% 8% 29% 26% 17% 5%	519
	21st to end	Day	15% 13% 32% 25% 11% 5%	583
September	1st to 10th	Day	18% 13% 29% 22% 13% 5%	530
	11th to 20th	Day	13% 12% 22% 24% 20% 8%	522
	21st to end	Day	19% 16% 25% 22% 13% 5%	490
October	1st to 10th	Day	26% 18% 25% 17% 11% 4	490
	11th to 20th	Day	28% 25% 27% 15% 5% 1	490
	21st to end	Day	34% 17% 29% 16% 3	504
November	1st to 10th	Day	28% 19% 32% 16% 5%	290
	11th to 20th	Day	29% 23% 32% 10% 6% 1	200
	21st to end	Day	34% 21% 36% 7% 2 1	200
December	1st to 10th	Day	32% 16% 38% 13% 3	200
	11th to 20th	Day	31% 31% 25% 11% 2 2	200
	21st to end	Day	31% 23% 28% 12% 5% 1	220
January	1st to 10th	Night	23% 20% 37% 16% 4 1	800
	11th to 20th	Night	25% 19% 31% 20% 5% 1	800
	21st to end	Night	17% 16% 38% 23% 6%	880
February	1st to 10th	Night	19% 21% 40% 17% 3	800
	11th to 20th	Night	21% 20% 39% 16% 3	783
	21st to end	Night	22% 21% 33% 21% 3	660
March	1st to 10th	Night	23% 21% 33% 19% 3	800
	11th to 20th	Night	22% 20% 34% 19% 5% 1	800
	21st to end	Night	20% 17% 34% 21% 7%	880
April	1st to 10th	Night	28% 16% 31% 20% 4	800
	11th to 20th	Night	25% 18% 30% 18% 8%	791
	21st to end	Night	23% 15% 27% 25% 9%	610
May	1st to 10th	Night	20% 11% 29% 28% 10% 1	440
	11th to 20th	Night	20% 11% 35% 27% 7%	394
	21st to end	Night	14% 10% 36% 30% 11%	433
June	1st to 10th	Night	17% 8% 36% 34% 5% 1	400
	11th to 20th	Night	19% 9% 31% 30% 10% 1	400
	21st to end	Night	19% 11% 29% 30% 11%	400
July	1st to 10th	Night	10% 6% 36% 35% 13% 1	390
	11th to 20th	Night	14% 6% 28% 39% 13% 1	388
	21st to end	Night	9% 8% 34% 37% 11% 1	438
August	1st to 10th	Night	10% 6% 24% 38% 21% 1	557
	11th to 20th	Night	12% 4 24% 38% 20% 3	594
	21st to end	Night	13% 8% 29% 32% 16% 2	799
September	1st to 10th	Night	16% 7% 30% 28% 17% 2	800
	11th to 20th	Night	17% 7% 24% 27% 22% 3	793
	21st to end	Night	19% 12% 22% 27% 17% 2	760
October	1st to 10th	Night	24% 11% 29% 21% 12% 2	760
	11th to 20th	Night	26% 17% 31% 18% 8% 1	760
	21st to end	Night	30% 19% 26% 20% 5%	836
November	1st to 10th	Night	27% 17% 29% 22% 5% 1	780
	11th to 20th	Night	22% 23% 30% 16% 8% 1	800
	21st to end	Night	29% 19% 28% 20% 3	800
December	1st to 10th	Night	29% 19% 33% 14% 5%	800
	11th to 20th	Night	26% 20% 30% 20% 3 1	800
	21st to end	Night	33% 18% 28% 19% 3 1	880

Page generated at 2025-09-16 01:49:12. Version ac07

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