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 2024-01-16.

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	20% 11% 4 7% 6% 3 4 4 5% 6% 29%	74418
	Night	20% 12% 5% 8% 6% 3 4 4 4 5% 28%	75378
Transparency	Day	57% 7% 11% 17% 8% 1	74123
	Night	59% 6% 10% 16% 8% 1	75208
Seeing	Day	26% 15% 28% 20% 9% 2	13528
	Night	26% 11% 28% 26% 8% 1	22672

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	22% 20% 7% 12% 8% 3 3 3 4 5% 14%	1517
	11th to 20th	Day	21% 17% 7% 11% 7% 3 4 3 4 4 19%	1480
	21st to end	Day	12% 15% 6% 10% 9% 3 6% 6% 4 5% 24%	1584
February	1st to 10th	Day	16% 18% 6% 12% 6% 4 5% 5% 5% 5% 19%	1480
	11th to 20th	Day	16% 18% 7% 10% 8% 4 5% 4 3 4 20%	1734
	21st to end	Day	15% 17% 7% 9% 6% 4 4 4 5% 6% 22%	1480
March	1st to 10th	Day	16% 15% 5% 10% 7% 3 4 4 5% 5% 25%	1797
	11th to 20th	Day	19% 13% 5% 8% 6% 3 5% 4 3 6% 28%	1862
	21st to end	Day	18% 13% 5% 8% 7% 3 5% 4 4 5% 29%	2344
April	1st to 10th	Day	25% 12% 5% 7% 6% 3 4 4 4 5% 26%	2160
	11th to 20th	Day	22% 10% 4 5% 4 3 4 3 4 6% 35%	2181
	21st to end	Day	25% 10% 4 6% 5% 3 4 4 5% 5% 28%	2340
May	1st to 10th	Day	23% 8% 3 7% 5% 3 4 3 4 6% 33%	2401
	11th to 20th	Day	19% 7% 3 6% 5% 4 4 4 6% 7% 34%	2478
	21st to end	Day	21% 7% 3 6% 6% 4 6% 5% 5% 6% 30%	2725
June	1st to 10th	Day	23% 8% 3 5% 5% 3 5% 6% 6% 8% 27%	2520
	11th to 20th	Day	18% 7% 3 5% 5% 3 5% 5% 7% 7% 35%	2520
	21st to end	Day	23% 7% 4 7% 7% 3 5% 4 6% 6% 28%	2520
July	1st to 10th	Day	17% 6% 3 6% 6% 4 5% 6% 6% 8% 33%	2520
	11th to 20th	Day	15% 6% 3 8% 5% 4 5% 6% 7% 9% 33%	2520
	21st to end	Day	17% 7% 3 6% 5% 4 5% 6% 6% 8% 32%	2744
August	1st to 10th	Day	19% 8% 3 6% 6% 3 4 6% 7% 8% 30%	2506
	11th to 20th	Day	15% 7% 3 7% 5% 4 6% 5% 6% 8% 34%	2304
	21st to end	Day	18% 5% 2 5% 6% 3 5% 5% 6% 7% 37%	2409
September	1st to 10th	Day	17% 7% 2 6% 5% 3 5% 4 5% 7% 39%	2160
	11th to 20th	Day	20% 6% 3 4 3 2 4 4 5% 8% 42%	2021
	21st to end	Day	20% 6% 2 5% 5% 3 4 5% 6% 7% 38%	1980
October	1st to 10th	Day	23% 8% 3 6% 6% 3 3 4 5% 8% 31%	1951
	11th to 20th	Day	25% 9% 4 7% 6% 4 5% 5% 5% 6% 24%	1683
	21st to end	Day	31% 12% 4 6% 5% 3 4 4 4 7% 21%	1782
November	1st to 10th	Day	22% 13% 3 6% 4 3 3 4 4 5% 31%	1671
	11th to 20th	Day	22% 16% 5% 9% 6% 3 4 4 5% 5% 23%	1710
	21st to end	Day	23% 18% 5% 7% 5% 3 4 4 4 5% 21%	1520
December	1st to 10th	Day	27% 18% 6% 10% 6% 4 3 4 3 4 17%	1339
	11th to 20th	Day	22% 16% 6% 8% 6% 4 4 3 3 4 25%	1703
	21st to end	Day	26% 18% 5% 12% 5% 3 3 3 3 4 18%	2772
January	1st to 10th	Night	21% 19% 8% 11% 7% 3 5% 3 4 4 16%	2649
	11th to 20th	Night	18% 18% 7% 12% 7% 3 4 4 3 4 20%	2602
	21st to end	Night	13% 16% 6% 11% 9% 4 5% 4 4 5% 23%	2772
February	1st to 10th	Night	15% 16% 6% 11% 8% 5% 5% 4 4 5% 21%	2479
	11th to 20th	Night	15% 17% 6% 13% 8% 4 5% 4 4 4 21%	2112
	21st to end	Night	15% 17% 5% 8% 6% 3 4 4 4 4 29%	1776
March	1st to 10th	Night	17% 15% 5% 9% 7% 3 4 3 4 4 28%	2150
	11th to 20th	Night	20% 13% 5% 8% 7% 3 5% 4 3 4 28%	2096
	21st to end	Night	19% 13% 5% 6% 5% 3 4 4 4 5% 33%	2009
April	1st to 10th	Night	25% 11% 5% 7% 6% 4 3 3 4 6% 27%	1800
	11th to 20th	Night	23% 9% 4 6% 5% 2 4 4 4 7% 33%	1728
	21st to end	Night	25% 11% 3 6% 5% 2 3 5% 5% 5% 30%	1620
May	1st to 10th	Night	24% 10% 3 6% 5% 2 3 4 5% 6% 31%	1575
	11th to 20th	Night	21% 9% 3 5% 6% 3 4 5% 5% 6% 34%	1415
	21st to end	Night	21% 5% 2 5% 6% 2 5% 4 5% 7% 36%	1550
June	1st to 10th	Night	22% 8% 3 7% 6% 4 5% 5% 6% 8% 28%	1440
	11th to 20th	Night	20% 5% 3 4 5% 3 5% 5% 5% 8% 35%	1440
	21st to end	Night	19% 7% 3 6% 6% 4 5% 6% 7% 6% 30%	1440
July	1st to 10th	Night	16% 5% 3 5% 6% 4 5% 5% 7% 10% 36%	1440
	11th to 20th	Night	14% 6% 3 6% 5% 4 5% 6% 6% 9% 35%	1440
	21st to end	Night	14% 6% 3 7% 6% 4 6% 5% 7% 8% 34%	1574
August	1st to 10th	Night	16% 5% 2 5% 5% 3 5% 6% 6% 9% 37%	1432
	11th to 20th	Night	16% 7% 3 7% 6% 3 5% 5% 6% 7% 35%	1579
	21st to end	Night	16% 7% 3 5% 6% 3 4 4 6% 8% 39%	1944
September	1st to 10th	Night	19% 6% 3 5% 6% 3 4 4 4 6% 40%	1800
	11th to 20th	Night	19% 4 2 5% 4 2 3 5% 4 6% 45%	1939
	21st to end	Night	20% 6% 3 6% 4 2 4 4 4 6% 42%	1980
October	1st to 10th	Night	21% 7% 3 5% 6% 3 5% 4 5% 6% 36%	2006
	11th to 20th	Night	25% 10% 3 7% 5% 3 4 4 5% 5% 29%	2276
	21st to end	Night	28% 12% 2 7% 5% 3 4 4 4 6% 26%	2574
November	1st to 10th	Night	22% 12% 5% 7% 5% 3 4 4 5% 5% 28%	2407
	11th to 20th	Night	21% 13% 6% 8% 5% 3 3 4 4 5% 28%	2470
	21st to end	Night	24% 16% 5% 9% 5% 3 3 3 4 4 24%	2658
December	1st to 10th	Night	25% 18% 7% 10% 6% 3 4 4 3 4 16%	2835
	11th to 20th	Night	23% 18% 7% 10% 6% 3 3 3 4 4 19%	3487
	21st to end	Night	25% 21% 7% 9% 4 2 3 3 3 3 21%	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	76% 5% 7% 9% 3	1518
	11th to 20th	Day	72% 5% 6% 11% 5% 1	1480
	21st to end	Day	62% 7% 9% 13% 8% 1	1584
February	1st to 10th	Day	72% 5% 6% 11% 5% 1	1480
	11th to 20th	Day	71% 5% 8% 10% 6% 1	1743
	21st to end	Day	66% 5% 7% 14% 6% 2	1480
March	1st to 10th	Day	63% 5% 8% 15% 8% 2	1800
	11th to 20th	Day	60% 5% 11% 11% 11% 1	1862
	21st to end	Day	61% 5% 7% 17% 9% 2	2344
April	1st to 10th	Day	63% 6% 8% 13% 8% 2	2160
	11th to 20th	Day	53% 5% 8% 20% 12% 2	2181
	21st to end	Day	59% 5% 7% 15% 10% 2	2340
May	1st to 10th	Day	55% 4 8% 18% 13% 2	2401
	11th to 20th	Day	49% 7% 12% 19% 11% 1	2482
	21st to end	Day	54% 7% 10% 17% 12%	2725
June	1st to 10th	Day	53% 9% 11% 19% 7% 1	2520
	11th to 20th	Day	47% 7% 13% 21% 11% 1	2520
	21st to end	Day	58% 7% 10% 18% 8%	2520
July	1st to 10th	Day	46% 9% 14% 23% 7%	2450
	11th to 20th	Day	47% 9% 16% 22% 7%	2445
	21st to end	Day	50% 9% 14% 20% 6%	2591
August	1st to 10th	Day	51% 9% 17% 20% 3	2492
	11th to 20th	Day	47% 9% 16% 21% 8%	2304
	21st to end	Day	46% 7% 14% 22% 10%	2409
September	1st to 10th	Day	45% 8% 15% 23% 9% 1	2160
	11th to 20th	Day	42% 7% 13% 28% 11%	2021
	21st to end	Day	47% 7% 13% 24% 9%	1980
October	1st to 10th	Day	52% 7% 12% 22% 7%	1951
	11th to 20th	Day	61% 7% 13% 16% 3	1683
	21st to end	Day	65% 6% 9% 15% 5% 1	1782
November	1st to 10th	Day	58% 6% 12% 17% 7%	1671
	11th to 20th	Day	65% 5% 9% 13% 7% 1	1710
	21st to end	Day	69% 6% 10% 12% 3	1520
December	1st to 10th	Day	75% 4 7% 9% 5%	1339
	11th to 20th	Day	67% 4 7% 15% 6%	1703
	21st to end	Day	73% 6% 5% 10% 6% 1	2772
January	1st to 10th	Night	75% 5% 6% 10% 3	2649
	11th to 20th	Night	71% 6% 7% 11% 5% 1	2602
	21st to end	Night	66% 5% 8% 13% 6% 1	2772
February	1st to 10th	Night	68% 4 7% 13% 6% 1	2479
	11th to 20th	Night	68% 5% 6% 12% 8%	2114
	21st to end	Night	60% 7% 7% 13% 11% 1	1776
March	1st to 10th	Night	62% 5% 8% 16% 8% 1	2160
	11th to 20th	Night	61% 6% 7% 12% 11% 2	2097
	21st to end	Night	55% 6% 7% 18% 10% 3	2009
April	1st to 10th	Night	60% 5% 8% 14% 12% 1	1800
	11th to 20th	Night	53% 6% 8% 20% 12% 2	1728
	21st to end	Night	56% 7% 9% 16% 11% 2	1620
May	1st to 10th	Night	54% 5% 9% 16% 14% 2	1575
	11th to 20th	Night	50% 6% 11% 17% 14% 2	1416
	21st to end	Night	48% 7% 12% 18% 14% 1	1551
June	1st to 10th	Night	54% 8% 10% 20% 8% 1	1440
	11th to 20th	Night	46% 6% 10% 23% 12% 2	1440
	21st to end	Night	52% 8% 13% 17% 10%	1440
July	1st to 10th	Night	42% 9% 16% 22% 10%	1400
	11th to 20th	Night	43% 10% 16% 21% 10%	1392
	21st to end	Night	46% 10% 15% 22% 7%	1486
August	1st to 10th	Night	42% 9% 18% 25% 6%	1422
	11th to 20th	Night	46% 9% 16% 22% 8%	1579
	21st to end	Night	44% 7% 14% 26% 9%	1944
September	1st to 10th	Night	46% 7% 13% 23% 11% 1	1800
	11th to 20th	Night	40% 6% 14% 30% 9% 1	1939
	21st to end	Night	45% 6% 11% 24% 13% 1	1980
October	1st to 10th	Night	49% 6% 10% 23% 12%	2006
	11th to 20th	Night	58% 7% 12% 19% 4	2276
	21st to end	Night	62% 6% 10% 14% 8% 1	2574
November	1st to 10th	Night	59% 6% 12% 17% 6% 1	2407
	11th to 20th	Night	60% 6% 11% 13% 8% 1	2470
	21st to end	Night	66% 6% 10% 13% 5%	2658
December	1st to 10th	Night	75% 5% 8% 9% 3	2835
	11th to 20th	Night	72% 6% 6% 11% 6%	3488
	21st to end	Night	70% 5% 7% 13% 5%	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	33% 20% 28% 17% 2 1	180
	11th to 20th	Day	36% 19% 28% 14% 4	170
	21st to end	Day	29% 16% 30% 18% 6% 1	176
February	1st to 10th	Day	34% 29% 30% 6% 1 1	178
	11th to 20th	Day	28% 21% 35% 13% 2	402
	21st to end	Day	26% 24% 28% 18% 3	346
March	1st to 10th	Day	26% 16% 32% 21% 4	420
	11th to 20th	Day	27% 20% 27% 19% 5% 1	420
	21st to end	Day	28% 20% 25% 18% 7% 2	462
April	1st to 10th	Day	33% 14% 30% 15% 6% 1	420
	11th to 20th	Day	32% 18% 24% 17% 7% 2	412
	21st to end	Day	31% 18% 29% 15% 5% 2	420
May	1st to 10th	Day	29% 15% 30% 18% 6% 1	423
	11th to 20th	Day	22% 14% 34% 20% 9% 1	447
	21st to end	Day	22% 20% 31% 16% 10% 1	485
June	1st to 10th	Day	28% 17% 31% 16% 8% 2	450
	11th to 20th	Day	22% 12% 30% 23% 13% 1	450
	21st to end	Day	23% 13% 30% 22% 10% 2	450
July	1st to 10th	Day	18% 9% 26% 30% 14% 2	445
	11th to 20th	Day	19% 9% 32% 28% 9% 2	444
	21st to end	Day	22% 8% 28% 30% 10% 2	488
August	1st to 10th	Day	22% 9% 24% 26% 16% 2	446
	11th to 20th	Day	19% 6% 23% 30% 20% 3	439
	21st to end	Day	21% 13% 25% 20% 13% 8%	495
September	1st to 10th	Day	18% 11% 28% 23% 14% 6%	450
	11th to 20th	Day	22% 9% 22% 23% 17% 7%	450
	21st to end	Day	21% 12% 25% 24% 14% 5%	450
October	1st to 10th	Day	23% 13% 26% 23% 12% 3	450
	11th to 20th	Day	31% 17% 24% 17% 10% 1	391
	21st to end	Day	38% 13% 27% 17% 6%	396
November	1st to 10th	Day	34% 12% 28% 20% 5% 1	365
	11th to 20th	Day	31% 17% 27% 17% 7% 1	370
	21st to end	Day	34% 23% 27% 14% 3	180
December	1st to 10th	Day	40% 14% 23% 18% 3 2	180
	11th to 20th	Day	31% 24% 30% 12% 3 1	180
	21st to end	Day	38% 19% 22% 17% 3 1	198
January	1st to 10th	Night	31% 15% 30% 20% 4	760
	11th to 20th	Night	27% 15% 33% 20% 5%	744
	21st to end	Night	21% 12% 34% 27% 5% 1	792
February	1st to 10th	Night	25% 15% 33% 22% 5%	720
	11th to 20th	Night	25% 14% 36% 19% 4	703
	21st to end	Night	26% 15% 30% 23% 5%	592
March	1st to 10th	Night	25% 13% 33% 25% 4	720
	11th to 20th	Night	28% 14% 31% 21% 5% 1	720
	21st to end	Night	25% 12% 29% 26% 7% 1	792
April	1st to 10th	Night	32% 12% 27% 24% 5%	720
	11th to 20th	Night	27% 14% 29% 23% 7%	664
	21st to end	Night	32% 10% 30% 21% 6% 1	540
May	1st to 10th	Night	28% 8% 30% 26% 7% 1	495
	11th to 20th	Night	25% 8% 30% 29% 7% 1	354
	21st to end	Night	23% 7% 35% 26% 9%	389
June	1st to 10th	Night	25% 7% 29% 30% 9%	360
	11th to 20th	Night	21% 5% 27% 35% 12%	360
	21st to end	Night	20% 7% 26% 36% 11%	360
July	1st to 10th	Night	17% 4 28% 37% 14% 1	350
	11th to 20th	Night	17% 3 24% 43% 13% 1	348
	21st to end	Night	16% 3 26% 43% 12%	394
August	1st to 10th	Night	19% 4 17% 38% 22% 1	358
	11th to 20th	Night	18% 4 23% 35% 19% 1	515
	21st to end	Night	20% 4 23% 32% 19% 2	756
September	1st to 10th	Night	21% 6% 22% 36% 12% 2	720
	11th to 20th	Night	21% 5% 23% 30% 19% 2	720
	21st to end	Night	21% 8% 27% 26% 15% 2	720
October	1st to 10th	Night	23% 8% 28% 28% 12% 1	720
	11th to 20th	Night	30% 10% 26% 25% 9% 1	720
	21st to end	Night	34% 11% 30% 22% 4	792
November	1st to 10th	Night	29% 14% 26% 25% 6%	740
	11th to 20th	Night	28% 15% 29% 18% 10% 1	760
	21st to end	Night	32% 14% 27% 21% 6% 1	760
December	1st to 10th	Night	35% 13% 29% 18% 6%	843
	11th to 20th	Night	29% 17% 29% 18% 6% 1	835
	21st to end	Night	36% 15% 27% 18% 4	836

Page generated at 2024-01-13 09:37:57. Version ac07

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