Barrie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Barrie clear sky chart from 2005-11-06 to 2026-03-18.

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	14% 10% 4 9% 6% 5% 5% 4 5% 7% 31%	132225
	Night	14% 11% 4 11% 6% 5% 5% 4 5% 6% 29%	129263
Transparency	Day	50% 7% 12% 19% 11% 1	135814
	Night	52% 7% 12% 18% 10% 1	133762
Seeing	Day	17% 11% 28% 25% 14% 5%	16511
	Night	18% 9% 29% 30% 12% 1	25525

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% 13% 6% 15% 7% 5% 6% 3 6% 6% 20%	4661
	11th to 20th	Day	7% 17% 7% 20% 10% 9% 7% 4 4 5% 10%	5043
	21st to end	Day	10% 15% 6% 15% 8% 9% 7% 5% 5% 5% 15%	5780
February	1st to 10th	Day	12% 15% 6% 15% 9% 6% 6% 4 4 5% 19%	1890
	11th to 20th	Day	12% 13% 6% 14% 9% 7% 5% 4 5% 5% 21%	1843
	21st to end	Day	13% 17% 6% 13% 7% 6% 5% 4 5% 6% 20%	1600
March	1st to 10th	Day	17% 11% 5% 11% 5% 5% 5% 3 4 5% 29%	5042
	11th to 20th	Day	12% 12% 5% 10% 7% 6% 5% 4 5% 7% 27%	5057
	21st to end	Day	17% 12% 5% 11% 5% 4 3 3 4 4 31%	5465
April	1st to 10th	Day	18% 13% 4 8% 6% 5% 5% 3 4 6% 29%	2357
	11th to 20th	Day	20% 10% 3 6% 4 3 4 3 4 6% 36%	2481
	21st to end	Day	20% 10% 4 8% 5% 4 3 2 5% 6% 34%	2600
May	1st to 10th	Day	17% 9% 3 8% 5% 4 3 3 6% 6% 35%	5888
	11th to 20th	Day	16% 9% 3 8% 5% 4 3 4 5% 6% 37%	6313
	21st to end	Day	19% 8% 3 6% 4 4 4 3 5% 7% 38%	6949
June	1st to 10th	Day	18% 7% 3 6% 5% 4 4 4 6% 7% 38%	2800
	11th to 20th	Day	13% 5% 2 5% 5% 4 5% 4 7% 10% 40%	2929
	21st to end	Day	15% 7% 3 6% 4 5% 5% 4 6% 8% 39%	3000
July	1st to 10th	Day	11% 6% 3 8% 5% 5% 5% 5% 6% 9% 38%	6784
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 6% 8% 47%	6360
	21st to end	Day	7% 5% 2 6% 4 4 5% 4 6% 8% 48%	6524
August	1st to 10th	Day	13% 7% 3 6% 5% 4 4 4 6% 8% 39%	4234
	11th to 20th	Day	11% 8% 3 7% 4 5% 5% 4 7% 10% 36%	4174
	21st to end	Day	10% 5% 2 7% 4 4 5% 4 6% 9% 44%	4525
September	1st to 10th	Day	13% 7% 2 7% 4 4 5% 4 5% 7% 40%	2400
	11th to 20th	Day	12% 5% 2 5% 4 4 5% 4 5% 8% 45%	2270
	21st to end	Day	16% 6% 3 7% 5% 5% 5% 4 6% 6% 37%	2166
October	1st to 10th	Day	18% 8% 3 9% 4 4 5% 4 5% 7% 35%	2000
	11th to 20th	Day	20% 10% 3 9% 6% 6% 6% 4 6% 6% 25%	2000
	21st to end	Day	24% 15% 3 10% 6% 5% 4 3 5% 5% 20%	2200
November	1st to 10th	Day	17% 13% 4 10% 6% 4 4 4 5% 6% 27%	1736
	11th to 20th	Day	15% 16% 5% 11% 5% 6% 5% 4 5% 7% 19%	1680
	21st to end	Day	18% 20% 5% 10% 8% 6% 5% 4 6% 4 14%	1680
December	1st to 10th	Day	14% 23% 9% 15% 8% 5% 5% 3 4 5% 9%	2680
	11th to 20th	Day	14% 20% 6% 14% 7% 5% 4 4 5% 5% 17%	3066
	21st to end	Day	23% 18% 6% 15% 6% 4 4 3 4 4 12%	4048
January	1st to 10th	Night	13% 15% 7% 18% 7% 6% 5% 3 4 5% 16%	8234
	11th to 20th	Night	10% 14% 7% 18% 12% 8% 6% 4 5% 5% 11%	7837
	21st to end	Night	10% 13% 6% 13% 10% 8% 7% 5% 6% 6% 16%	8401
February	1st to 10th	Night	11% 17% 5% 14% 9% 6% 5% 5% 5% 5% 19%	2730
	11th to 20th	Night	13% 13% 6% 13% 7% 6% 6% 3 6% 6% 22%	2663
	21st to end	Night	14% 14% 5% 12% 6% 4 5% 4 5% 5% 24%	2201
March	1st to 10th	Night	15% 10% 4 11% 6% 6% 5% 4 5% 6% 28%	5018
	11th to 20th	Night	9% 10% 4 9% 6% 6% 6% 5% 7% 8% 31%	5057
	21st to end	Night	19% 9% 4 11% 6% 5% 5% 3 5% 5% 28%	5467
April	1st to 10th	Night	18% 12% 3 10% 6% 5% 4 4 5% 5% 29%	2042
	11th to 20th	Night	17% 9% 3 7% 5% 4 4 4 5% 6% 36%	1886
	21st to end	Night	17% 9% 4 8% 6% 4 4 4 4 6% 35%	1800
May	1st to 10th	Night	18% 7% 2 7% 4 5% 5% 3 6% 6% 36%	4053
	11th to 20th	Night	12% 7% 3 7% 4 5% 5% 4 6% 7% 41%	3579
	21st to end	Night	17% 6% 2 6% 5% 4 4 3 5% 7% 42%	3926
June	1st to 10th	Night	14% 6% 2 7% 6% 4 4 4 7% 7% 40%	1600
	11th to 20th	Night	9% 5% 2 7% 4 5% 6% 4 6% 10% 42%	1465
	21st to end	Night	11% 7% 3 6% 5% 5% 5% 4 4 8% 42%	1400
July	1st to 10th	Night	9% 6% 3 7% 5% 5% 4 4 5% 7% 45%	3176
	11th to 20th	Night	10% 6% 2 6% 4 3 3 3 5% 8% 50%	3600
	21st to end	Night	8% 6% 2 6% 3 4 4 3 6% 8% 50%	4325
August	1st to 10th	Night	9% 6% 3 6% 4 5% 4 4 6% 7% 46%	2915
	11th to 20th	Night	12% 6% 3 7% 4 3 4 3 5% 7% 47%	2875
	21st to end	Night	11% 6% 2 6% 3 4 5% 4 6% 8% 46%	3340
September	1st to 10th	Night	10% 6% 2 6% 4 4 5% 4 5% 8% 46%	2000
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 5% 7% 52%	2125
	21st to end	Night	16% 7% 3 7% 4 4 4 4 5% 5% 41%	2233
October	1st to 10th	Night	17% 6% 3 8% 5% 5% 4 3 5% 6% 38%	2400
	11th to 20th	Night	20% 10% 3 7% 5% 5% 6% 4 4 6% 31%	2400
	21st to end	Night	22% 12% 3 9% 6% 5% 5% 4 5% 6% 24%	2640
November	1st to 10th	Night	17% 11% 4 8% 5% 5% 4 3 6% 6% 32%	2777
	11th to 20th	Night	14% 18% 5% 10% 6% 5% 5% 3 6% 6% 22%	2940
	21st to end	Night	19% 17% 5% 10% 7% 5% 5% 4 6% 5% 18%	2940
December	1st to 10th	Night	14% 20% 7% 15% 8% 6% 5% 4 4 5% 12%	4720
	11th to 20th	Night	14% 18% 6% 14% 7% 6% 5% 4 5% 5% 16%	5348
	21st to end	Night	22% 19% 6% 16% 6% 5% 4 3 4 4 13%	7150

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	62% 7% 12% 13% 7%	4662
	11th to 20th	Day	73% 6% 8% 8% 4	5077
	21st to end	Day	65% 7% 10% 9% 8%	5780
February	1st to 10th	Day	66% 7% 8% 14% 4	1890
	11th to 20th	Day	63% 5% 11% 14% 6% 1	1852
	21st to end	Day	63% 6% 10% 14% 6%	1600
March	1st to 10th	Day	55% 6% 13% 13% 12%	5045
	11th to 20th	Day	54% 5% 15% 17% 7% 2	5057
	21st to end	Day	55% 4 9% 17% 13% 1	5465
April	1st to 10th	Day	57% 5% 9% 18% 10% 1	2357
	11th to 20th	Day	49% 6% 9% 22% 14% 1	2481
	21st to end	Day	51% 6% 10% 18% 12% 3	2600
May	1st to 10th	Day	46% 7% 12% 19% 11% 5%	5897
	11th to 20th	Day	47% 8% 10% 16% 18% 1	6317
	21st to end	Day	45% 6% 11% 22% 14% 3	6949
June	1st to 10th	Day	43% 8% 11% 22% 16% 1	2800
	11th to 20th	Day	37% 8% 12% 25% 16% 1	2929
	21st to end	Day	41% 8% 13% 23% 14% 1	3000
July	1st to 10th	Day	40% 7% 14% 22% 14% 1	6711
	11th to 20th	Day	33% 7% 12% 32% 16% 1	6285
	21st to end	Day	32% 7% 13% 33% 15% 1	6337
August	1st to 10th	Day	41% 8% 14% 24% 12% 1	4221
	11th to 20th	Day	40% 8% 17% 25% 10%	4213
	21st to end	Day	36% 7% 14% 33% 11% 1	4525
September	1st to 10th	Day	41% 7% 14% 27% 10% 1	2400
	11th to 20th	Day	37% 6% 14% 30% 13% 1	2270
	21st to end	Day	45% 9% 11% 25% 9%	2166
October	1st to 10th	Day	43% 6% 13% 25% 13% 1	3260
	11th to 20th	Day	44% 6% 15% 23% 12%	3240
	21st to end	Day	58% 7% 14% 15% 5%	3538
November	1st to 10th	Day	54% 8% 14% 17% 6%	1736
	11th to 20th	Day	60% 9% 12% 12% 6% 1	1680
	21st to end	Day	68% 9% 11% 10% 2	1680
December	1st to 10th	Day	75% 8% 9% 6% 1	2680
	11th to 20th	Day	67% 8% 10% 9% 6%	3066
	21st to end	Day	76% 6% 7% 7% 5%	4048
January	1st to 10th	Night	65% 9% 10% 12% 4	8234
	11th to 20th	Night	70% 8% 8% 8% 5% 1	7878
	21st to end	Night	63% 7% 10% 10% 10%	8401
February	1st to 10th	Night	63% 7% 9% 16% 4	2730
	11th to 20th	Night	61% 6% 12% 15% 6%	2665
	21st to end	Night	57% 6% 12% 17% 7%	2201
March	1st to 10th	Night	54% 6% 11% 16% 11% 2	5028
	11th to 20th	Night	45% 6% 19% 20% 8% 2	5058
	21st to end	Night	54% 5% 11% 16% 13% 2	5467
April	1st to 10th	Night	55% 6% 9% 18% 12% 1	2042
	11th to 20th	Night	48% 5% 10% 19% 16% 2	1886
	21st to end	Night	50% 5% 11% 17% 16% 2	1800
May	1st to 10th	Night	47% 7% 12% 14% 15% 6%	4060
	11th to 20th	Night	39% 8% 13% 22% 16% 2	3580
	21st to end	Night	41% 7% 12% 25% 14% 1	3927
June	1st to 10th	Night	41% 6% 11% 24% 16% 2	1600
	11th to 20th	Night	36% 7% 14% 22% 20% 1	1465
	21st to end	Night	38% 9% 12% 25% 15% 1	1400
July	1st to 10th	Night	36% 6% 13% 26% 16% 2	3141
	11th to 20th	Night	32% 5% 12% 31% 19% 1	3552
	21st to end	Night	31% 7% 10% 33% 17% 1	4197
August	1st to 10th	Night	35% 6% 14% 28% 16% 1	2904
	11th to 20th	Night	34% 7% 18% 27% 14% 1	2902
	21st to end	Night	34% 8% 14% 31% 12% 1	3340
September	1st to 10th	Night	34% 8% 14% 30% 12% 1	2000
	11th to 20th	Night	30% 7% 13% 33% 16% 1	2125
	21st to end	Night	43% 7% 13% 26% 10% 1	2233
October	1st to 10th	Night	35% 6% 11% 27% 21% 1	3920
	11th to 20th	Night	44% 6% 15% 23% 12%	3899
	21st to end	Night	47% 9% 15% 22% 7%	4252
November	1st to 10th	Night	50% 8% 14% 20% 8% 1	2777
	11th to 20th	Night	60% 7% 14% 12% 6% 1	2940
	21st to end	Night	64% 8% 14% 12% 1	2940
December	1st to 10th	Night	71% 8% 11% 8% 3	4720
	11th to 20th	Night	65% 8% 11% 11% 5%	5348
	21st to end	Night	75% 5% 8% 7% 5%	7150

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	14% 19% 38% 20% 7% 2	220
	11th to 20th	Day	18% 14% 42% 18% 6% 1	292
	21st to end	Day	21% 15% 34% 24% 5% 1	363
February	1st to 10th	Day	18% 20% 41% 15% 6% 1	330
	11th to 20th	Day	22% 18% 37% 21% 2	330
	21st to end	Day	23% 22% 32% 22% 1	273
March	1st to 10th	Day	18% 14% 39% 23% 7%	540
	11th to 20th	Day	18% 19% 32% 23% 6% 1	528
	21st to end	Day	27% 9% 35% 20% 8% 1	550
April	1st to 10th	Day	23% 15% 34% 20% 7% 1	500
	11th to 20th	Day	27% 13% 26% 18% 11% 4	492
	21st to end	Day	24% 13% 25% 26% 10% 2	500
May	1st to 10th	Day	18% 9% 29% 27% 13% 5%	503
	11th to 20th	Day	14% 8% 25% 28% 19% 5%	527
	21st to end	Day	16% 6% 24% 30% 18% 6%	573
June	1st to 10th	Day	17% 8% 26% 28% 18% 3	530
	11th to 20th	Day	13% 6% 25% 34% 19% 4	659
	21st to end	Day	17% 7% 28% 30% 14% 4	730
July	1st to 10th	Day	9% 5% 24% 33% 23% 6%	712
	11th to 20th	Day	11% 5% 22% 29% 23% 9%	524
	21st to end	Day	9% 4 22% 36% 19% 9%	576
August	1st to 10th	Day	10% 5% 19% 28% 27% 12%	526
	11th to 20th	Day	10% 5% 18% 29% 25% 14%	519
	21st to end	Day	12% 5% 22% 30% 21% 11%	583
September	1st to 10th	Day	12% 8% 23% 22% 23% 12%	530
	11th to 20th	Day	9% 5% 18% 25% 24% 18%	530
	21st to end	Day	15% 7% 25% 25% 21% 6%	530
October	1st to 10th	Day	16% 10% 27% 22% 16% 8%	530
	11th to 20th	Day	20% 15% 32% 23% 8% 2	530
	21st to end	Day	26% 15% 30% 22% 6%	583
November	1st to 10th	Day	22% 22% 28% 19% 8% 1	276
	11th to 20th	Day	18% 23% 37% 15% 5% 1	220
	21st to end	Day	23% 18% 40% 16% 3	220
December	1st to 10th	Day	20% 20% 34% 20% 4 1	220
	11th to 20th	Day	21% 25% 29% 20% 5% 1	220
	21st to end	Day	25% 14% 41% 16% 3	242
January	1st to 10th	Night	20% 13% 40% 19% 7% 1	840
	11th to 20th	Night	22% 12% 34% 25% 6%	840
	21st to end	Night	17% 9% 35% 31% 8% 1	924
February	1st to 10th	Night	19% 11% 39% 26% 4	840
	11th to 20th	Night	18% 12% 36% 28% 5%	823
	21st to end	Night	19% 13% 36% 27% 4	692
March	1st to 10th	Night	18% 12% 35% 29% 5%	840
	11th to 20th	Night	17% 14% 36% 28% 6% 1	829
	21st to end	Night	20% 10% 32% 27% 11%	880
April	1st to 10th	Night	24% 11% 32% 28% 5%	800
	11th to 20th	Night	21% 8% 31% 29% 10% 2	702
	21st to end	Night	22% 8% 28% 30% 13%	600
May	1st to 10th	Night	19% 3 25% 37% 15% 1	600
	11th to 20th	Night	17% 5% 26% 38% 14% 1	398
	21st to end	Night	12% 4 23% 43% 18%	433
June	1st to 10th	Night	14% 4 28% 40% 13% 1	400
	11th to 20th	Night	11% 6% 20% 47% 16% 1	400
	21st to end	Night	13% 6% 22% 41% 18% 1	400
July	1st to 10th	Night	7% 3 17% 50% 22% 1	390
	11th to 20th	Night	9% 5% 23% 40% 21% 2	388
	21st to end	Night	10% 3 19% 43% 24% 1	606
August	1st to 10th	Night	10% 3 14% 42% 30% 2	597
	11th to 20th	Night	6% 2 15% 38% 35% 3	594
	21st to end	Night	12% 4 21% 35% 26% 2	725
September	1st to 10th	Night	12% 5% 21% 35% 22% 6%	800
	11th to 20th	Night	12% 3 20% 32% 26% 7%	800
	21st to end	Night	18% 8% 20% 31% 20% 4	800
October	1st to 10th	Night	18% 6% 30% 27% 17% 2	800
	11th to 20th	Night	21% 12% 31% 25% 9% 1	800
	21st to end	Night	27% 11% 30% 26% 6%	880
November	1st to 10th	Night	21% 13% 30% 25% 10% 1	820
	11th to 20th	Night	21% 15% 34% 21% 8% 1	840
	21st to end	Night	25% 15% 33% 23% 4	840
December	1st to 10th	Night	24% 16% 37% 18% 5%	840
	11th to 20th	Night	22% 15% 38% 20% 5% 1	840
	21st to end	Night	28% 13% 33% 22% 3	924

Page generated at 2026-03-15 02:23:56. Version ac07

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