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 2024-01-15.

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% 9% 4 8% 6% 3 5% 5% 5% 7% 32%	75145
	Night	15% 11% 4 8% 7% 4 5% 5% 5% 6% 30%	74626
Transparency	Day	51% 7% 12% 19% 10% 1	74855
	Night	53% 7% 12% 18% 9% 1	74451
Seeing	Day	17% 10% 28% 26% 15% 5%	13715
	Night	19% 9% 29% 29% 12% 1	22771

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% 15% 6% 10% 10% 5% 6% 5% 5% 6% 19%	1517
	11th to 20th	Day	15% 16% 7% 11% 9% 4 6% 6% 4 5% 16%	1595
	21st to end	Day	12% 15% 8% 13% 9% 4 6% 6% 5% 5% 17%	1782
February	1st to 10th	Day	13% 14% 6% 13% 11% 4 8% 5% 4 4 18%	1620
	11th to 20th	Day	12% 12% 7% 12% 8% 5% 6% 5% 5% 5% 23%	1573
	21st to end	Day	15% 15% 7% 11% 8% 4 5% 4 4 5% 21%	1368
March	1st to 10th	Day	13% 10% 4 10% 7% 5% 6% 5% 5% 6% 29%	1977
	11th to 20th	Day	12% 12% 6% 9% 8% 4 5% 4 4 5% 30%	1980
	21st to end	Day	17% 11% 4 6% 6% 3 5% 4 4 5% 35%	2178
April	1st to 10th	Day	18% 12% 4 7% 7% 4 5% 4 4 6% 29%	2121
	11th to 20th	Day	20% 9% 3 5% 4 3 4 4 4 7% 36%	2229
	21st to end	Day	20% 10% 4 7% 6% 3 3 3 4 6% 35%	2340
May	1st to 10th	Day	18% 8% 3 7% 7% 3 4 4 6% 7% 35%	2340
	11th to 20th	Day	15% 7% 2 5% 5% 3 3 5% 5% 7% 42%	2473
	21st to end	Day	12% 5% 3 5% 6% 3 5% 5% 6% 8% 44%	2725
June	1st to 10th	Day	18% 5% 3 5% 4 2 5% 4 6% 7% 39%	2520
	11th to 20th	Day	14% 4 2 5% 4 3 5% 5% 6% 10% 42%	2635
	21st to end	Day	14% 6% 3 5% 5% 3 5% 5% 6% 8% 40%	2700
July	1st to 10th	Day	9% 5% 2 5% 6% 3 4 5% 6% 9% 45%	2693
	11th to 20th	Day	11% 6% 2 5% 6% 4 5% 5% 6% 9% 41%	2520
	21st to end	Day	11% 5% 3 6% 6% 4 6% 6% 7% 10% 38%	2591
August	1st to 10th	Day	11% 4 2 5% 6% 3 4 6% 7% 9% 42%	2327
	11th to 20th	Day	9% 5% 3 6% 5% 4 6% 6% 7% 10% 40%	2303
	21st to end	Day	11% 6% 2 6% 6% 3 5% 5% 7% 9% 40%	2498
September	1st to 10th	Day	14% 6% 3 6% 6% 3 5% 5% 5% 7% 39%	2160
	11th to 20th	Day	14% 5% 2 5% 5% 4 5% 5% 5% 8% 42%	2044
	21st to end	Day	15% 6% 3 6% 7% 4 6% 5% 6% 6% 37%	1950
October	1st to 10th	Day	19% 8% 4 8% 5% 3 5% 5% 5% 7% 32%	1800
	11th to 20th	Day	22% 10% 4 9% 7% 5% 5% 6% 5% 6% 23%	1800
	21st to end	Day	25% 14% 3 9% 7% 4 5% 3 5% 5% 19%	1980
November	1st to 10th	Day	16% 12% 4 9% 7% 4 5% 5% 5% 6% 27%	1568
	11th to 20th	Day	16% 14% 6% 10% 6% 5% 6% 6% 5% 7% 19%	1520
	21st to end	Day	19% 18% 6% 9% 8% 4 6% 4 6% 5% 15%	1520
December	1st to 10th	Day	15% 20% 9% 13% 8% 4 5% 5% 5% 6% 12%	1520
	11th to 20th	Day	17% 15% 7% 10% 9% 4 5% 6% 5% 5% 18%	1906
	21st to end	Day	27% 17% 7% 13% 7% 3 4 4 3 4 11%	2772
January	1st to 10th	Night	15% 16% 7% 11% 9% 4 6% 5% 5% 6% 17%	2649
	11th to 20th	Night	18% 14% 6% 11% 9% 5% 7% 5% 5% 5% 14%	2466
	21st to end	Night	13% 13% 7% 12% 10% 4 6% 5% 6% 6% 18%	2574
February	1st to 10th	Night	12% 15% 7% 13% 10% 4 6% 6% 5% 5% 16%	2340
	11th to 20th	Night	13% 13% 6% 12% 7% 4 6% 5% 5% 6% 23%	2273
	21st to end	Night	16% 12% 6% 11% 7% 3 5% 5% 5% 5% 25%	1884
March	1st to 10th	Night	13% 11% 4 8% 8% 5% 6% 4 4 5% 32%	1970
	11th to 20th	Night	14% 10% 7% 8% 7% 3 4 4 5% 6% 33%	1979
	21st to end	Night	16% 9% 4 7% 6% 3 5% 4 5% 6% 37%	2178
April	1st to 10th	Night	19% 10% 4 7% 7% 4 4 4 5% 6% 30%	1838
	11th to 20th	Night	17% 8% 3 5% 6% 3 4 5% 5% 6% 37%	1696
	21st to end	Night	18% 9% 4 7% 7% 3 4 4 3 6% 35%	1620
May	1st to 10th	Night	18% 6% 2 6% 4 3 5% 4 6% 7% 39%	1620
	11th to 20th	Night	14% 6% 3 5% 4 4 4 4 6% 6% 45%	1419
	21st to end	Night	10% 4 2 4 4 3 5% 4 5% 9% 49%	1550
June	1st to 10th	Night	14% 5% 2 6% 6% 4 4 5% 7% 7% 40%	1440
	11th to 20th	Night	9% 4 3 5% 5% 4 6% 6% 5% 10% 43%	1319
	21st to end	Night	11% 6% 3 6% 6% 3 5% 5% 5% 8% 43%	1260
July	1st to 10th	Night	6% 5% 2 4 5% 3 5% 3 5% 7% 56%	1263
	11th to 20th	Night	8% 6% 3 5% 5% 3 4 5% 5% 9% 47%	1440
	21st to end	Night	8% 4 3 5% 5% 4 6% 4 7% 7% 49%	1724
August	1st to 10th	Night	8% 5% 2 4 5% 3 4 5% 7% 8% 49%	1611
	11th to 20th	Night	7% 4 3 5% 5% 2 5% 5% 6% 8% 50%	1598
	21st to end	Night	11% 6% 2 5% 5% 3 6% 6% 6% 7% 43%	1840
September	1st to 10th	Night	10% 5% 2 5% 5% 3 5% 5% 5% 8% 45%	1800
	11th to 20th	Night	12% 5% 2 5% 4 2 4 4 6% 7% 49%	1912
	21st to end	Night	15% 6% 3 7% 5% 3 4 5% 5% 6% 42%	2009
October	1st to 10th	Night	18% 6% 3 7% 7% 4 5% 4 5% 6% 35%	2160
	11th to 20th	Night	21% 10% 3 6% 7% 4 5% 6% 4 5% 29%	2160
	21st to end	Night	24% 12% 4 7% 7% 4 5% 5% 5% 6% 22%	2376
November	1st to 10th	Night	18% 10% 3 6% 5% 3 5% 5% 6% 6% 33%	2506
	11th to 20th	Night	16% 16% 5% 9% 6% 4 6% 5% 6% 7% 22%	2660
	21st to end	Night	19% 14% 5% 8% 7% 5% 5% 5% 6% 5% 20%	2660
December	1st to 10th	Night	18% 17% 8% 11% 8% 4 5% 4 5% 5% 16%	2660
	11th to 20th	Night	16% 17% 6% 11% 8% 4 5% 5% 6% 6% 17%	3288
	21st to end	Night	27% 19% 7% 13% 7% 4 4 3 3 4 10%	4884

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	65% 9% 12% 11% 4	1518
	11th to 20th	Day	67% 9% 10% 7% 6% 1	1595
	21st to end	Day	66% 6% 11% 11% 6% 1	1782
February	1st to 10th	Day	68% 8% 8% 12% 4	1620
	11th to 20th	Day	62% 5% 11% 14% 7% 1	1582
	21st to end	Day	63% 5% 10% 14% 7%	1368
March	1st to 10th	Day	55% 7% 13% 16% 9% 1	1980
	11th to 20th	Day	54% 6% 11% 16% 11% 2	1980
	21st to end	Day	51% 4 10% 17% 15% 2	2178
April	1st to 10th	Day	57% 5% 9% 18% 10% 1	2121
	11th to 20th	Day	48% 6% 9% 22% 15% 1	2229
	21st to end	Day	51% 5% 11% 18% 12% 3	2340
May	1st to 10th	Day	48% 5% 9% 21% 14% 2	2340
	11th to 20th	Day	42% 7% 10% 25% 15% 1	2477
	21st to end	Day	37% 8% 14% 23% 14% 3	2725
June	1st to 10th	Day	42% 8% 11% 23% 15% 1	2520
	11th to 20th	Day	37% 9% 12% 25% 16% 1	2635
	21st to end	Day	40% 8% 14% 23% 14% 1	2700
July	1st to 10th	Day	34% 8% 13% 24% 19% 2	2619
	11th to 20th	Day	37% 9% 14% 28% 11% 1	2445
	21st to end	Day	41% 10% 12% 24% 12% 1	2446
August	1st to 10th	Day	36% 10% 16% 24% 12% 1	2314
	11th to 20th	Day	35% 10% 18% 26% 10% 1	2303
	21st to end	Day	39% 8% 16% 25% 11% 1	2498
September	1st to 10th	Day	42% 8% 13% 26% 10% 2	2160
	11th to 20th	Day	39% 7% 14% 27% 11% 1	2044
	21st to end	Day	45% 9% 12% 26% 7% 1	1950
October	1st to 10th	Day	51% 6% 13% 17% 11% 1	1800
	11th to 20th	Day	59% 7% 12% 16% 5% 1	1800
	21st to end	Day	66% 7% 12% 10% 5%	1980
November	1st to 10th	Day	54% 8% 15% 16% 7%	1568
	11th to 20th	Day	60% 8% 12% 12% 6% 1	1520
	21st to end	Day	67% 9% 11% 10% 2	1520
December	1st to 10th	Day	72% 8% 11% 7% 1	1520
	11th to 20th	Day	67% 9% 12% 9% 3	1906
	21st to end	Day	79% 6% 8% 6% 1	2772
January	1st to 10th	Night	66% 8% 12% 11% 3	2649
	11th to 20th	Night	71% 8% 9% 7% 4 1	2466
	21st to end	Night	64% 7% 11% 12% 6% 1	2574
February	1st to 10th	Night	66% 7% 10% 15% 3	2340
	11th to 20th	Night	61% 6% 12% 16% 6%	2275
	21st to end	Night	59% 5% 11% 16% 7%	1884
March	1st to 10th	Night	53% 5% 14% 16% 9% 1	1980
	11th to 20th	Night	52% 5% 11% 20% 11% 2	1980
	21st to end	Night	48% 5% 11% 19% 14% 2	2178
April	1st to 10th	Night	54% 6% 9% 18% 12% 1	1838
	11th to 20th	Night	47% 5% 11% 19% 17% 2	1696
	21st to end	Night	51% 5% 10% 16% 16% 2	1620
May	1st to 10th	Night	43% 6% 12% 20% 17% 3	1620
	11th to 20th	Night	39% 4 12% 24% 18% 3	1420
	21st to end	Night	31% 8% 15% 26% 17% 3	1551
June	1st to 10th	Night	42% 6% 11% 24% 16% 1	1440
	11th to 20th	Night	35% 7% 14% 22% 20% 1	1319
	21st to end	Night	38% 9% 13% 25% 15% 1	1260
July	1st to 10th	Night	28% 6% 11% 30% 22% 2	1228
	11th to 20th	Night	33% 6% 13% 32% 15% 1	1392
	21st to end	Night	33% 9% 12% 30% 15% 2	1628
August	1st to 10th	Night	31% 7% 18% 29% 14% 1	1600
	11th to 20th	Night	28% 9% 18% 27% 17% 1	1598
	21st to end	Night	36% 10% 14% 25% 13% 1	1840
September	1st to 10th	Night	35% 9% 15% 27% 13% 1	1800
	11th to 20th	Night	33% 7% 13% 32% 14% 1	1912
	21st to end	Night	43% 7% 14% 26% 10%	2009
October	1st to 10th	Night	48% 8% 12% 19% 12% 1	2160
	11th to 20th	Night	54% 8% 13% 19% 6%	2160
	21st to end	Night	61% 8% 11% 13% 7%	2376
November	1st to 10th	Night	50% 8% 13% 21% 8% 1	2506
	11th to 20th	Night	60% 7% 14% 12% 6% 1	2660
	21st to end	Night	63% 8% 15% 12% 1	2660
December	1st to 10th	Night	69% 8% 12% 9% 3	2660
	11th to 20th	Night	66% 9% 13% 10% 2	3288
	21st to end	Night	79% 5% 8% 6% 1	4884

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	13% 19% 36% 22% 8% 2	180
	11th to 20th	Day	20% 12% 41% 18% 7% 1	222
	21st to end	Day	22% 12% 36% 23% 6% 1	264
February	1st to 10th	Day	19% 20% 43% 13% 5%	240
	11th to 20th	Day	21% 16% 38% 23% 2	240
	21st to end	Day	24% 24% 30% 21% 1	198
March	1st to 10th	Day	17% 12% 41% 23% 7%	420
	11th to 20th	Day	17% 16% 34% 25% 7% 1	420
	21st to end	Day	27% 7% 34% 21% 9% 1	462
April	1st to 10th	Day	21% 13% 35% 20% 9% 2	420
	11th to 20th	Day	26% 12% 26% 19% 12% 5%	412
	21st to end	Day	24% 11% 25% 27% 11% 2	420
May	1st to 10th	Day	20% 7% 27% 27% 13% 5%	423
	11th to 20th	Day	15% 7% 25% 30% 19% 5%	447
	21st to end	Day	15% 5% 23% 31% 20% 7%	485
June	1st to 10th	Day	17% 6% 25% 29% 19% 3	450
	11th to 20th	Day	14% 6% 23% 32% 21% 5%	565
	21st to end	Day	15% 6% 27% 31% 16% 5%	630
July	1st to 10th	Day	8% 5% 23% 33% 24% 7%	614
	11th to 20th	Day	11% 4 22% 30% 23% 10%	444
	21st to end	Day	10% 4 20% 39% 19% 8%	488
August	1st to 10th	Day	10% 4 17% 28% 28% 13%	446
	11th to 20th	Day	8% 3 18% 29% 27% 14%	439
	21st to end	Day	13% 4 23% 29% 21% 11%	495
September	1st to 10th	Day	13% 7% 22% 23% 23% 12%	450
	11th to 20th	Day	11% 6% 20% 26% 22% 14%	450
	21st to end	Day	14% 8% 26% 25% 21% 7%	450
October	1st to 10th	Day	18% 9% 27% 22% 15% 9%	450
	11th to 20th	Day	22% 14% 33% 23% 8% 1	450
	21st to end	Day	28% 15% 30% 21% 6%	495
November	1st to 10th	Day	18% 23% 28% 21% 9% 1	228
	11th to 20th	Day	19% 21% 35% 17% 6% 2	180
	21st to end	Day	23% 17% 42% 16% 3	180
December	1st to 10th	Day	19% 21% 35% 20% 4 1	180
	11th to 20th	Day	22% 22% 30% 21% 4 1	180
	21st to end	Day	25% 13% 44% 16% 2	198
January	1st to 10th	Night	21% 13% 39% 19% 7% 1	760
	11th to 20th	Night	24% 11% 33% 25% 6%	740
	21st to end	Night	18% 7% 34% 32% 9% 1	792
February	1st to 10th	Night	21% 11% 40% 24% 4	720
	11th to 20th	Night	19% 11% 37% 27% 5%	703
	21st to end	Night	20% 12% 37% 26% 5%	592
March	1st to 10th	Night	18% 11% 36% 29% 6%	720
	11th to 20th	Night	17% 13% 35% 28% 7% 1	720
	21st to end	Night	20% 9% 31% 28% 12%	792
April	1st to 10th	Night	23% 11% 32% 28% 6%	720
	11th to 20th	Night	20% 8% 30% 29% 11% 2	632
	21st to end	Night	23% 7% 26% 30% 14%	540
May	1st to 10th	Night	19% 3 24% 37% 16% 1	540
	11th to 20th	Night	18% 5% 26% 37% 13% 1	358
	21st to end	Night	10% 4 23% 43% 19%	389
June	1st to 10th	Night	14% 5% 27% 40% 13% 1	360
	11th to 20th	Night	11% 6% 20% 46% 17% 1	360
	21st to end	Night	13% 5% 21% 42% 19% 1	360
July	1st to 10th	Night	7% 4 17% 47% 24% 1	350
	11th to 20th	Night	9% 5% 24% 39% 21% 2	348
	21st to end	Night	10% 3 19% 43% 25% 1	544
August	1st to 10th	Night	10% 3 15% 41% 29% 2	537
	11th to 20th	Night	6% 1 15% 38% 37% 3	534
	21st to end	Night	13% 4 21% 33% 27% 2	652
September	1st to 10th	Night	13% 4 20% 35% 23% 5%	720
	11th to 20th	Night	13% 4 22% 32% 23% 7%	720
	21st to end	Night	17% 8% 20% 30% 20% 5%	720
October	1st to 10th	Night	19% 6% 30% 26% 17% 2	720
	11th to 20th	Night	23% 12% 31% 25% 9% 1	720
	21st to end	Night	29% 11% 29% 24% 6%	792
November	1st to 10th	Night	22% 12% 29% 26% 11% 1	740
	11th to 20th	Night	22% 15% 34% 21% 8% 1	760
	21st to end	Night	25% 14% 32% 24% 4	760
December	1st to 10th	Night	26% 16% 36% 17% 5% 1	760
	11th to 20th	Night	23% 14% 37% 21% 5% 1	760
	21st to end	Night	29% 13% 33% 22% 3	836

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