Victoriaville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Victoriaville 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	19% 12% 4 9% 5% 5% 4 4 5% 6% 28%	130485
	Night	19% 14% 5% 10% 5% 4 4 3 4 5% 26%	131010
Transparency	Day	58% 6% 11% 17% 7% 1	133940
	Night	61% 5% 10% 16% 8% 1	135643
Seeing	Day	26% 15% 28% 20% 8% 2	16245
	Night	26% 11% 29% 25% 8% 1	25426

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	16% 21% 7% 16% 5% 6% 4 3 4 4 15%	4661
	11th to 20th	Day	11% 20% 8% 21% 8% 5% 4 3 3 3 13%	4650
	21st to end	Day	8% 15% 7% 14% 9% 9% 6% 5% 5% 5% 19%	5124
February	1st to 10th	Day	15% 17% 5% 13% 6% 6% 5% 3 4 5% 21%	1727
	11th to 20th	Day	15% 19% 5% 12% 8% 5% 4 3 4 4 21%	2032
	21st to end	Day	14% 18% 6% 10% 7% 5% 4 3 4 6% 23%	1730
March	1st to 10th	Day	19% 17% 6% 12% 5% 4 3 3 4 4 21%	4576
	11th to 20th	Day	17% 17% 4 9% 4 4 4 3 4 6% 28%	4765
	21st to end	Day	20% 15% 5% 9% 5% 4 3 3 3 4 29%	5896
April	1st to 10th	Day	24% 14% 4 8% 5% 4 3 3 4 5% 27%	2400
	11th to 20th	Day	21% 11% 4 7% 4 4 4 2 4 6% 34%	2427
	21st to end	Day	25% 10% 4 7% 5% 5% 3 3 5% 5% 28%	2600
May	1st to 10th	Day	29% 9% 3 8% 4 5% 4 3 5% 6% 23%	6059
	11th to 20th	Day	21% 8% 3 8% 5% 5% 5% 4 6% 7% 30%	6318
	21st to end	Day	20% 10% 3 7% 5% 5% 5% 4 5% 6% 30%	6949
June	1st to 10th	Day	23% 8% 3 6% 5% 4 6% 4 6% 8% 28%	2800
	11th to 20th	Day	17% 7% 3 7% 4 4 5% 4 7% 8% 34%	2800
	21st to end	Day	24% 8% 3 8% 6% 4 4 4 6% 6% 28%	2800
July	1st to 10th	Day	18% 7% 3 8% 6% 6% 6% 5% 7% 9% 26%	6360
	11th to 20th	Day	16% 6% 3 7% 5% 5% 5% 4 6% 9% 34%	6360
	21st to end	Day	14% 6% 2 5% 3 4 4 4 6% 9% 42%	6926
August	1st to 10th	Day	19% 7% 2 7% 5% 5% 5% 4 7% 10% 29%	4550
	11th to 20th	Day	17% 7% 3 8% 5% 5% 6% 4 6% 8% 30%	4175
	21st to end	Day	21% 7% 2 6% 4 4 4 3 6% 6% 37%	4361
September	1st to 10th	Day	15% 7% 2 6% 5% 4 4 4 6% 7% 41%	2400
	11th to 20th	Day	18% 6% 2 5% 3 3 4 3 5% 8% 44%	2245
	21st to end	Day	20% 6% 2 5% 4 4 4 3 6% 7% 37%	2200
October	1st to 10th	Day	21% 8% 2 6% 6% 4 3 4 5% 8% 34%	2167
	11th to 20th	Day	24% 10% 4 8% 4 5% 4 3 5% 7% 26%	1869
	21st to end	Day	29% 13% 4 7% 4 4 4 3 4 6% 23%	1980
November	1st to 10th	Day	22% 16% 3 7% 4 4 3 3 4 5% 29%	1851
	11th to 20th	Day	20% 19% 5% 10% 4 4 3 3 4 4 23%	1890
	21st to end	Day	23% 22% 5% 8% 4 4 4 3 4 4 19%	1680
December	1st to 10th	Day	20% 19% 6% 13% 7% 5% 4 3 4 4 16%	2359
	11th to 20th	Day	21% 17% 6% 10% 4 4 3 2 3 4 24%	2750
	21st to end	Day	22% 17% 4 13% 5% 4 4 3 4 4 20%	4048
January	1st to 10th	Night	15% 22% 8% 14% 6% 4 4 2 4 4 18%	8234
	11th to 20th	Night	14% 23% 9% 19% 7% 5% 4 3 3 2 12%	8235
	21st to end	Night	8% 15% 6% 16% 11% 6% 5% 3 4 5% 22%	9057
February	1st to 10th	Night	14% 17% 5% 13% 8% 6% 4 3 4 5% 22%	2891
	11th to 20th	Night	14% 18% 5% 15% 7% 5% 4 3 3 4 22%	2474
	21st to end	Night	15% 19% 5% 9% 5% 3 4 4 4 4 29%	2076
March	1st to 10th	Night	21% 15% 5% 11% 6% 4 4 3 3 5% 24%	5484
	11th to 20th	Night	16% 17% 5% 10% 5% 5% 5% 3 5% 6% 24%	5348
	21st to end	Night	18% 17% 5% 9% 4 4 3 3 4 4 28%	5019
April	1st to 10th	Night	24% 13% 4 8% 4 4 3 3 5% 5% 28%	2000
	11th to 20th	Night	23% 11% 3 6% 4 3 3 3 4 6% 31%	1922
	21st to end	Night	25% 12% 3 6% 4 3 3 4 4 5% 31%	1800
May	1st to 10th	Night	28% 10% 3 8% 5% 5% 4 4 5% 5% 24%	3925
	11th to 20th	Night	25% 9% 3 7% 4 4 4 4 5% 6% 31%	3575
	21st to end	Night	20% 7% 3 9% 5% 4 5% 3 5% 8% 32%	3926
June	1st to 10th	Night	22% 8% 2 8% 5% 5% 5% 4 6% 7% 29%	1600
	11th to 20th	Night	20% 5% 3 6% 4 4 5% 5% 5% 8% 35%	1600
	21st to end	Night	20% 8% 3 7% 5% 5% 5% 4 6% 6% 31%	1600
July	1st to 10th	Night	18% 7% 3 7% 5% 6% 5% 4 7% 9% 29%	3600
	11th to 20th	Night	21% 6% 2 6% 4 4 4 4 5% 7% 36%	3600
	21st to end	Night	13% 6% 3 7% 5% 5% 5% 4 6% 8% 38%	3926
August	1st to 10th	Night	22% 8% 2 7% 4 4 5% 4 5% 7% 32%	2586
	11th to 20th	Night	18% 8% 3 7% 5% 5% 5% 4 6% 7% 32%	2841
	21st to end	Night	19% 7% 3 6% 5% 4 4 3 5% 6% 38%	3520
September	1st to 10th	Night	19% 6% 3 6% 4 4 3 3 4 6% 42%	2000
	11th to 20th	Night	17% 5% 2 6% 4 3 3 3 5% 6% 47%	2155
	21st to end	Night	19% 7% 2 7% 4 3 4 3 5% 6% 41%	2200
October	1st to 10th	Night	20% 7% 2 6% 4 5% 4 3 5% 6% 38%	2230
	11th to 20th	Night	23% 10% 2 7% 4 5% 4 3 5% 5% 31%	2530
	21st to end	Night	27% 12% 2 8% 4 4 4 3 4 6% 27%	2860
November	1st to 10th	Night	23% 14% 4 8% 4 4 4 3 4 5% 27%	2667
	11th to 20th	Night	20% 15% 6% 9% 4 3 3 3 4 5% 28%	2730
	21st to end	Night	23% 18% 5% 9% 4 4 3 3 4 4 22%	2938
December	1st to 10th	Night	18% 23% 9% 14% 5% 4 3 2 3 4 14%	5044
	11th to 20th	Night	22% 19% 6% 11% 5% 4 4 3 4 4 20%	5667
	21st to end	Night	21% 20% 6% 10% 4 4 3 2 3 4 24%	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	75% 5% 7% 10% 3	4662
	11th to 20th	Day	79% 5% 3 9% 4	4680
	21st to end	Day	69% 7% 5% 9% 9%	5124
February	1st to 10th	Day	69% 5% 6% 13% 6% 1	1727
	11th to 20th	Day	70% 4 7% 12% 6% 1	2041
	21st to end	Day	66% 4 7% 14% 7% 2	1730
March	1st to 10th	Day	68% 5% 5% 11% 9% 2	4579
	11th to 20th	Day	59% 6% 14% 11% 10% 1	4765
	21st to end	Day	61% 4 5% 15% 13% 1	5896
April	1st to 10th	Day	63% 5% 8% 14% 9% 2	2400
	11th to 20th	Day	54% 5% 8% 20% 12% 1	2427
	21st to end	Day	59% 5% 8% 16% 10% 2	2600
May	1st to 10th	Day	62% 6% 9% 16% 7% 1	6070
	11th to 20th	Day	52% 8% 16% 15% 7% 2	6322
	21st to end	Day	53% 8% 11% 17% 11% 1	6949
June	1st to 10th	Day	53% 9% 10% 19% 8% 1	2800
	11th to 20th	Day	47% 7% 13% 22% 10% 1	2800
	21st to end	Day	58% 7% 10% 18% 8%	2800
July	1st to 10th	Day	55% 5% 15% 20% 4	6290
	11th to 20th	Day	47% 6% 16% 26% 6%	6285
	21st to end	Day	41% 5% 15% 32% 7%	6728
August	1st to 10th	Day	51% 6% 18% 20% 4	4536
	11th to 20th	Day	52% 7% 18% 18% 5%	4214
	21st to end	Day	48% 5% 15% 19% 12% 1	4361
September	1st to 10th	Day	43% 7% 15% 26% 9% 1	2400
	11th to 20th	Day	40% 6% 13% 30% 11%	2245
	21st to end	Day	47% 7% 12% 24% 10%	2200
October	1st to 10th	Day	50% 4 15% 25% 6%	3531
	11th to 20th	Day	56% 4 14% 24% 2	3020
	21st to end	Day	56% 4 16% 17% 5%	3180
November	1st to 10th	Day	60% 5% 11% 17% 7%	1851
	11th to 20th	Day	66% 5% 9% 13% 7%	1890
	21st to end	Day	71% 6% 9% 11% 3	1680
December	1st to 10th	Day	76% 3 8% 9% 4	2359
	11th to 20th	Day	68% 3 6% 16% 7%	2750
	21st to end	Day	69% 5% 5% 12% 9% 1	4048
January	1st to 10th	Night	73% 5% 8% 10% 4	8234
	11th to 20th	Night	80% 5% 5% 7% 3	8280
	21st to end	Night	69% 4 6% 11% 9%	9057
February	1st to 10th	Night	66% 4 8% 14% 7% 1	2891
	11th to 20th	Night	68% 5% 6% 12% 8%	2476
	21st to end	Night	60% 7% 7% 14% 11% 1	2076
March	1st to 10th	Night	65% 4 8% 11% 9% 2	5494
	11th to 20th	Night	62% 5% 11% 13% 7% 1	5349
	21st to end	Night	61% 5% 5% 18% 9% 1	5019
April	1st to 10th	Night	59% 5% 8% 15% 12% 1	2000
	11th to 20th	Night	55% 6% 7% 18% 12% 2	1922
	21st to end	Night	55% 7% 8% 17% 11% 2	1800
May	1st to 10th	Night	61% 6% 11% 14% 7% 1	3931
	11th to 20th	Night	53% 6% 12% 20% 7% 1	3576
	21st to end	Night	51% 6% 13% 14% 15% 1	3927
June	1st to 10th	Night	53% 8% 10% 20% 9% 1	1600
	11th to 20th	Night	47% 6% 11% 22% 12% 2	1600
	21st to end	Night	52% 7% 12% 17% 11%	1600
July	1st to 10th	Night	52% 5% 18% 18% 6%	3560
	11th to 20th	Night	47% 5% 18% 22% 7%	3552
	21st to end	Night	44% 6% 17% 26% 8%	3809
August	1st to 10th	Night	51% 6% 15% 23% 5%	2576
	11th to 20th	Night	52% 7% 15% 20% 6%	2868
	21st to end	Night	48% 5% 11% 23% 12%	3520
September	1st to 10th	Night	45% 6% 13% 25% 11% 1	2000
	11th to 20th	Night	38% 6% 14% 32% 10% 1	2155
	21st to end	Night	45% 6% 11% 25% 13% 1	2200
October	1st to 10th	Night	51% 4 11% 23% 10%	3646
	11th to 20th	Night	55% 4 12% 25% 4	4118
	21st to end	Night	55% 4 13% 18% 8% 1	4610
November	1st to 10th	Night	61% 6% 11% 16% 6% 1	2667
	11th to 20th	Night	61% 6% 11% 13% 8% 1	2730
	21st to end	Night	68% 5% 10% 12% 4	2938
December	1st to 10th	Night	79% 3 8% 8% 2	5044
	11th to 20th	Night	71% 4 5% 13% 6%	5668
	21st to end	Night	67% 4 7% 13% 9%	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	32% 20% 30% 15% 2	220
	11th to 20th	Day	33% 19% 31% 14% 3	220
	21st to end	Day	29% 17% 31% 16% 6%	242
February	1st to 10th	Day	29% 24% 31% 13% 1 1	245
	11th to 20th	Day	27% 21% 35% 15% 2	520
	21st to end	Day	26% 24% 30% 17% 3	446
March	1st to 10th	Day	28% 19% 30% 19% 4	540
	11th to 20th	Day	30% 18% 28% 18% 4 1	528
	21st to end	Day	29% 21% 27% 16% 6% 1	550
April	1st to 10th	Day	35% 14% 28% 17% 6% 1	500
	11th to 20th	Day	34% 18% 24% 17% 6% 1	492
	21st to end	Day	31% 19% 29% 14% 5% 2	500
May	1st to 10th	Day	30% 15% 29% 19% 6% 1	503
	11th to 20th	Day	23% 13% 31% 22% 10% 1	527
	21st to end	Day	23% 20% 29% 18% 9% 1	573
June	1st to 10th	Day	26% 15% 31% 18% 8% 2	530
	11th to 20th	Day	21% 12% 31% 24% 11% 1	530
	21st to end	Day	25% 13% 31% 20% 9% 2	530
July	1st to 10th	Day	18% 11% 28% 28% 12% 2	525
	11th to 20th	Day	18% 10% 33% 28% 8% 2	524
	21st to end	Day	20% 9% 30% 29% 10% 2	576
August	1st to 10th	Day	21% 8% 25% 29% 16% 3	526
	11th to 20th	Day	19% 6% 24% 29% 20% 2	519
	21st to end	Day	21% 14% 24% 21% 14% 7%	583
September	1st to 10th	Day	17% 12% 29% 23% 13% 6%	530
	11th to 20th	Day	19% 8% 22% 25% 18% 8%	530
	21st to end	Day	21% 13% 24% 24% 13% 5%	530
October	1st to 10th	Day	22% 12% 28% 24% 12% 3	530
	11th to 20th	Day	30% 17% 24% 18% 10% 1	457
	21st to end	Day	36% 14% 28% 17% 6%	462
November	1st to 10th	Day	36% 12% 28% 19% 4	425
	11th to 20th	Day	32% 16% 27% 17% 7% 1	430
	21st to end	Day	37% 21% 27% 12% 2	220
December	1st to 10th	Day	36% 14% 27% 18% 3 1	220
	11th to 20th	Day	31% 23% 31% 12% 2	220
	21st to end	Day	36% 18% 24% 17% 3 1	242
January	1st to 10th	Night	30% 15% 30% 21% 4	840
	11th to 20th	Night	28% 16% 32% 20% 4	840
	21st to end	Night	20% 13% 35% 26% 5%	924
February	1st to 10th	Night	23% 15% 33% 23% 6%	840
	11th to 20th	Night	24% 15% 37% 19% 4	823
	21st to end	Night	26% 15% 32% 23% 4	692
March	1st to 10th	Night	26% 14% 32% 24% 4	840
	11th to 20th	Night	28% 16% 30% 21% 5% 1	829
	21st to end	Night	26% 12% 30% 25% 6% 1	880
April	1st to 10th	Night	32% 13% 27% 23% 5%	800
	11th to 20th	Night	28% 16% 29% 22% 6%	738
	21st to end	Night	33% 10% 30% 21% 6% 1	600
May	1st to 10th	Night	27% 9% 31% 26% 7% 1	549
	11th to 20th	Night	25% 7% 31% 28% 8% 1	394
	21st to end	Night	23% 6% 35% 28% 9%	433
June	1st to 10th	Night	24% 8% 29% 31% 8%	400
	11th to 20th	Night	21% 7% 26% 35% 12%	400
	21st to end	Night	21% 8% 26% 35% 10%	400
July	1st to 10th	Night	17% 4 28% 38% 13% 1	390
	11th to 20th	Night	18% 4 24% 42% 12% 1	388
	21st to end	Night	15% 4 26% 43% 12%	438
August	1st to 10th	Night	19% 4 18% 38% 22% 1	398
	11th to 20th	Night	17% 5% 23% 35% 20% 1	573
	21st to end	Night	20% 5% 23% 32% 18% 2	840
September	1st to 10th	Night	21% 6% 22% 37% 12% 2	800
	11th to 20th	Night	19% 5% 22% 32% 21% 2	800
	21st to end	Night	21% 8% 27% 27% 16% 2	800
October	1st to 10th	Night	23% 8% 29% 28% 12% 1	800
	11th to 20th	Night	29% 10% 27% 26% 9% 1	800
	21st to end	Night	33% 11% 30% 22% 4	880
November	1st to 10th	Night	30% 14% 26% 24% 5%	820
	11th to 20th	Night	27% 15% 28% 19% 10% 1	840
	21st to end	Night	33% 15% 27% 20% 5%	840
December	1st to 10th	Night	33% 13% 30% 18% 6%	942
	11th to 20th	Night	30% 17% 29% 18% 5% 1	931
	21st to end	Night	35% 16% 26% 19% 4 1	924

Page generated at 2026-03-15 02:23:51. Version ac07

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