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 2024-12-06.

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% 11% 4 8% 5% 4 4 4 5% 6% 29%	101385
	Night	20% 13% 4 9% 5% 4 4 3 4 5% 28%	98322
Transparency	Day	56% 7% 12% 18% 7% 1	104858
	Night	58% 6% 11% 17% 8% 1	102939
Seeing	Day	26% 15% 28% 20% 9% 2	14709
	Night	26% 11% 28% 26% 8% 1	23753

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	18% 21% 6% 16% 5% 4 3 3 4 4 15%	2517
	11th to 20th	Day	13% 17% 8% 18% 8% 4 3 3 4 3 19%	2520
	21st to end	Day	12% 18% 6% 12% 7% 6% 5% 4 5% 5% 20%	2772
February	1st to 10th	Day	16% 19% 5% 12% 6% 6% 5% 3 4 5% 20%	1562
	11th to 20th	Day	16% 19% 5% 12% 8% 6% 4 3 4 4 20%	1833
	21st to end	Day	14% 18% 6% 9% 6% 5% 4 3 5% 6% 23%	1570
March	1st to 10th	Day	19% 15% 4 11% 5% 4 3 3 5% 5% 25%	3116
	11th to 20th	Day	18% 21% 5% 11% 5% 4 3 3 3 4 22%	3278
	21st to end	Day	17% 14% 5% 9% 4 4 3 3 4 4 34%	4120
April	1st to 10th	Day	24% 14% 3 8% 5% 4 4 3 4 5% 27%	2280
	11th to 20th	Day	21% 11% 4 7% 4 4 4 2 4 6% 34%	2304
	21st to end	Day	25% 10% 4 7% 5% 5% 3 3 5% 5% 29%	2470
May	1st to 10th	Day	24% 9% 3 8% 4 4 4 3 5% 7% 29%	4223
	11th to 20th	Day	18% 8% 3 7% 5% 5% 5% 5% 7% 9% 29%	4398
	21st to end	Day	17% 8% 3 7% 6% 5% 6% 5% 6% 6% 31%	4837
June	1st to 10th	Day	23% 8% 3 6% 5% 4 6% 4 6% 8% 27%	2660
	11th to 20th	Day	17% 7% 3 6% 4 4 5% 4 7% 8% 34%	2660
	21st to end	Day	24% 8% 3 8% 6% 4 4 4 5% 6% 27%	2660
July	1st to 10th	Day	16% 7% 3 8% 5% 5% 5% 5% 6% 8% 31%	4440
	11th to 20th	Day	17% 7% 3 8% 5% 5% 6% 5% 6% 8% 31%	4440
	21st to end	Day	15% 6% 2 6% 4 4 4 4 6% 7% 42%	4814
August	1st to 10th	Day	19% 7% 2 7% 5% 5% 5% 4 8% 9% 28%	4410
	11th to 20th	Day	18% 7% 3 8% 5% 5% 6% 5% 7% 8% 29%	4045
	21st to end	Day	21% 6% 2 6% 4 4 4 3 6% 6% 37%	4227
September	1st to 10th	Day	16% 7% 2 7% 5% 4 4 4 6% 7% 40%	2280
	11th to 20th	Day	19% 6% 2 5% 3 3 4 3 5% 8% 42%	2133
	21st to end	Day	20% 7% 2 6% 4 4 4 3 6% 7% 37%	2090
October	1st to 10th	Day	22% 8% 3 6% 6% 4 3 4 5% 8% 32%	2059
	11th to 20th	Day	25% 10% 4 8% 4 5% 4 4 5% 6% 25%	1776
	21st to end	Day	29% 13% 4 7% 4 4 4 3 4 7% 23%	1881
November	1st to 10th	Day	21% 15% 3 7% 4 4 3 3 4 5% 31%	1761
	11th to 20th	Day	21% 17% 4 9% 5% 4 3 3 5% 5% 24%	1800
	21st to end	Day	23% 21% 5% 8% 4 4 4 3 4 5% 20%	1600
December	1st to 10th	Day	25% 19% 6% 11% 6% 5% 3 3 3 4 16%	1374
	11th to 20th	Day	21% 17% 5% 9% 5% 5% 3 2 3 4 24%	1703
	21st to end	Day	26% 18% 5% 13% 4 4 3 3 3 4 18%	2772
January	1st to 10th	Night	18% 21% 7% 13% 5% 4 4 2 4 4 19%	4429
	11th to 20th	Night	14% 18% 7% 17% 7% 5% 4 3 4 3 17%	4440
	21st to end	Night	14% 18% 6% 13% 8% 5% 5% 3 4 4 22%	4884
February	1st to 10th	Night	15% 17% 5% 13% 8% 6% 4 3 4 5% 21%	2617
	11th to 20th	Night	14% 18% 5% 15% 7% 5% 4 3 4 4 21%	2233
	21st to end	Night	15% 18% 4 9% 5% 4 4 4 4 5% 29%	1884
March	1st to 10th	Night	23% 13% 3 8% 5% 4 4 2 3 4 30%	3724
	11th to 20th	Night	18% 22% 6% 10% 5% 5% 4 2 3 3 22%	3680
	21st to end	Night	17% 16% 5% 10% 5% 4 3 3 4 4 30%	3509
April	1st to 10th	Night	24% 13% 3 8% 4 4 3 3 5% 5% 28%	1900
	11th to 20th	Night	23% 11% 3 6% 4 3 3 3 5% 6% 32%	1825
	21st to end	Night	24% 12% 3 7% 4 3 3 4 5% 5% 31%	1710
May	1st to 10th	Night	24% 10% 3 8% 5% 4 4 4 5% 6% 28%	2747
	11th to 20th	Night	21% 9% 3 6% 5% 3 4 4 5% 7% 34%	2495
	21st to end	Night	18% 6% 2 7% 5% 4 5% 3 6% 9% 35%	2738
June	1st to 10th	Night	22% 8% 2 8% 5% 5% 5% 4 6% 7% 29%	1520
	11th to 20th	Night	20% 5% 3 6% 4 4 5% 4 5% 8% 36%	1520
	21st to end	Night	20% 9% 3 7% 5% 5% 5% 5% 6% 6% 30%	1520
July	1st to 10th	Night	16% 7% 3 7% 5% 6% 5% 4 7% 9% 31%	2520
	11th to 20th	Night	19% 7% 3 7% 4 4 5% 4 6% 7% 35%	2520
	21st to end	Night	14% 6% 2 7% 5% 4 4 4 6% 7% 39%	2739
August	1st to 10th	Night	22% 8% 2 8% 4 5% 5% 4 5% 7% 30%	2506
	11th to 20th	Night	19% 8% 3 7% 5% 5% 5% 4 6% 7% 31%	2752
	21st to end	Night	20% 7% 3 6% 5% 4 4 3 5% 6% 38%	3412
September	1st to 10th	Night	19% 6% 3 6% 5% 4 3 3 4 6% 41%	1900
	11th to 20th	Night	18% 5% 2 5% 4 3 3 3 5% 6% 46%	2047
	21st to end	Night	19% 7% 2 7% 4 3 4 3 4 6% 41%	2090
October	1st to 10th	Night	21% 7% 3 6% 4 5% 4 3 5% 6% 36%	2118
	11th to 20th	Night	25% 11% 2 7% 4 5% 4 3 5% 5% 30%	2403
	21st to end	Night	27% 11% 2 8% 4 4 4 3 4 6% 27%	2717
November	1st to 10th	Night	22% 13% 4 8% 4 4 4 3 4 6% 27%	2537
	11th to 20th	Night	21% 14% 5% 9% 4 3 3 3 4 5% 29%	2600
	21st to end	Night	24% 18% 5% 9% 5% 4 3 3 4 4 23%	2798
December	1st to 10th	Night	23% 21% 7% 11% 4 4 3 3 3 4 16%	2917
	11th to 20th	Night	22% 19% 7% 11% 5% 4 3 3 4 4 19%	3487
	21st to end	Night	24% 21% 6% 10% 4 3 3 2 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	73% 8% 8% 9% 2	2518
	11th to 20th	Day	70% 8% 4 14% 3 1	2520
	21st to end	Day	64% 11% 8% 10% 6% 1	2772
February	1st to 10th	Day	70% 5% 6% 12% 5% 1	1562
	11th to 20th	Day	71% 5% 8% 10% 6% 1	1842
	21st to end	Day	65% 5% 8% 14% 6% 2	1570
March	1st to 10th	Day	61% 6% 7% 15% 9% 2	3119
	11th to 20th	Day	66% 7% 10% 10% 8% 1	3278
	21st to end	Day	56% 5% 7% 17% 13% 2	4120
April	1st to 10th	Day	63% 5% 8% 14% 8% 2	2280
	11th to 20th	Day	53% 6% 8% 20% 12% 1	2304
	21st to end	Day	59% 5% 8% 16% 10% 2	2470
May	1st to 10th	Day	54% 8% 10% 18% 9% 1	4237
	11th to 20th	Day	49% 10% 19% 14% 7% 1	4402
	21st to end	Day	48% 10% 11% 19% 12%	4837
June	1st to 10th	Day	53% 9% 11% 19% 7% 1	2660
	11th to 20th	Day	47% 7% 14% 21% 11% 1	2660
	21st to end	Day	58% 7% 10% 17% 8%	2660
July	1st to 10th	Day	51% 6% 14% 23% 6%	4370
	11th to 20th	Day	51% 6% 17% 22% 4	4365
	21st to end	Day	43% 7% 14% 30% 7%	4661
August	1st to 10th	Day	52% 6% 17% 20% 4	4396
	11th to 20th	Day	53% 7% 19% 17% 4	4084
	21st to end	Day	48% 5% 15% 18% 12% 1	4227
September	1st to 10th	Day	44% 8% 15% 24% 9% 1	2280
	11th to 20th	Day	41% 7% 13% 29% 11%	2133
	21st to end	Day	47% 7% 12% 24% 9%	2090
October	1st to 10th	Day	51% 5% 15% 24% 5%	3423
	11th to 20th	Day	57% 4 14% 23% 2	2927
	21st to end	Day	56% 4 17% 17% 5%	3081
November	1st to 10th	Day	58% 5% 11% 18% 7%	1761
	11th to 20th	Day	64% 5% 9% 14% 8% 1	1800
	21st to end	Day	70% 6% 10% 11% 3	1600
December	1st to 10th	Day	76% 4 7% 9% 4	1374
	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	70% 8% 10% 9% 3	4429
	11th to 20th	Night	70% 9% 7% 10% 3 1	4440
	21st to end	Night	68% 6% 9% 11% 5% 1	4884
February	1st to 10th	Night	67% 4 8% 13% 7% 1	2617
	11th to 20th	Night	69% 6% 6% 12% 8%	2235
	21st to end	Night	59% 7% 8% 13% 11% 1	1884
March	1st to 10th	Night	58% 6% 10% 14% 9% 3	3734
	11th to 20th	Night	67% 6% 6% 12% 7% 1	3681
	21st to end	Night	58% 7% 7% 18% 9% 2	3509
April	1st to 10th	Night	58% 5% 8% 15% 12% 1	1900
	11th to 20th	Night	54% 6% 8% 19% 12% 2	1825
	21st to end	Night	55% 7% 9% 16% 11% 2	1710
May	1st to 10th	Night	55% 7% 13% 16% 8% 1	2753
	11th to 20th	Night	48% 8% 15% 19% 9% 1	2496
	21st to end	Night	45% 8% 13% 17% 16% 1	2739
June	1st to 10th	Night	53% 8% 10% 20% 8% 1	1520
	11th to 20th	Night	46% 6% 11% 22% 12% 2	1520
	21st to end	Night	53% 8% 12% 16% 11%	1520
July	1st to 10th	Night	50% 6% 16% 20% 8%	2480
	11th to 20th	Night	48% 6% 20% 19% 7%	2472
	21st to end	Night	43% 7% 18% 25% 7%	2651
August	1st to 10th	Night	52% 6% 14% 23% 4	2496
	11th to 20th	Night	53% 7% 15% 19% 5%	2779
	21st to end	Night	48% 5% 11% 23% 13%	3412
September	1st to 10th	Night	45% 6% 13% 24% 11% 1	1900
	11th to 20th	Night	38% 6% 15% 31% 9% 1	2047
	21st to end	Night	46% 6% 11% 24% 12% 1	2090
October	1st to 10th	Night	52% 5% 11% 23% 9%	3534
	11th to 20th	Night	55% 4 13% 24% 4	3991
	21st to end	Night	55% 4 14% 18% 8% 2	4467
November	1st to 10th	Night	60% 6% 12% 16% 6% 1	2537
	11th to 20th	Night	60% 6% 11% 14% 9% 1	2600
	21st to end	Night	68% 5% 10% 13% 4	2798
December	1st to 10th	Night	76% 5% 8% 9% 3	2917
	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	34% 19% 29% 13% 4	180
	21st to end	Day	28% 16% 31% 18% 7% 1	198
February	1st to 10th	Day	33% 27% 31% 9% 1 1	200
	11th to 20th	Day	27% 22% 35% 14% 2	441
	21st to end	Day	26% 25% 28% 18% 3	382
March	1st to 10th	Day	26% 17% 31% 21% 4	460
	11th to 20th	Day	28% 20% 28% 19% 5% 1	460
	21st to end	Day	28% 20% 26% 17% 7% 2	506
April	1st to 10th	Day	34% 14% 29% 16% 6% 1	460
	11th to 20th	Day	32% 19% 24% 17% 7% 2	452
	21st to end	Day	30% 19% 30% 14% 5% 2	460
May	1st to 10th	Day	29% 16% 29% 19% 6% 1	463
	11th to 20th	Day	22% 13% 32% 22% 10% 1	487
	21st to end	Day	22% 19% 31% 17% 9% 1	529
June	1st to 10th	Day	27% 16% 30% 18% 8% 2	490
	11th to 20th	Day	21% 12% 31% 24% 12% 1	490
	21st to end	Day	25% 14% 29% 21% 9% 2	490
July	1st to 10th	Day	18% 10% 27% 29% 13% 2	485
	11th to 20th	Day	20% 9% 33% 27% 8% 2	484
	21st to end	Day	21% 8% 28% 30% 11% 2	532
August	1st to 10th	Day	22% 8% 24% 27% 15% 2	486
	11th to 20th	Day	20% 6% 24% 30% 19% 2	479
	21st to end	Day	21% 13% 24% 21% 14% 8%	539
September	1st to 10th	Day	18% 12% 29% 23% 13% 6%	490
	11th to 20th	Day	21% 8% 21% 24% 18% 7%	490
	21st to end	Day	21% 13% 24% 24% 13% 5%	490
October	1st to 10th	Day	23% 12% 27% 23% 12% 3	490
	11th to 20th	Day	32% 17% 24% 17% 10% 1	424
	21st to end	Day	36% 14% 28% 17% 6%	429
November	1st to 10th	Day	34% 13% 28% 19% 5% 1	395
	11th to 20th	Day	32% 16% 27% 18% 7% 1	400
	21st to end	Day	36% 22% 28% 13% 3	200
December	1st to 10th	Day	38% 14% 24% 18% 4 2	190
	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% 16% 32% 20% 5%	760
	21st to end	Night	21% 12% 34% 27% 5%	836
February	1st to 10th	Night	24% 15% 33% 23% 5%	760
	11th to 20th	Night	24% 15% 37% 19% 4	743
	21st to end	Night	26% 15% 31% 23% 5%	628
March	1st to 10th	Night	25% 13% 32% 26% 4	760
	11th to 20th	Night	28% 14% 31% 21% 5% 1	760
	21st to end	Night	25% 12% 30% 25% 7% 1	836
April	1st to 10th	Night	32% 12% 27% 24% 5%	760
	11th to 20th	Night	27% 16% 29% 22% 6%	701
	21st to end	Night	32% 11% 30% 21% 6% 1	570
May	1st to 10th	Night	28% 8% 31% 26% 7% 1	522
	11th to 20th	Night	25% 7% 29% 29% 7% 1	374
	21st to end	Night	23% 7% 36% 27% 9%	411
June	1st to 10th	Night	24% 8% 28% 31% 9%	380
	11th to 20th	Night	21% 6% 26% 35% 12%	380
	21st to end	Night	21% 7% 25% 35% 11%	380
July	1st to 10th	Night	17% 4 28% 38% 13% 1	370
	11th to 20th	Night	17% 3 24% 42% 13% 1	368
	21st to end	Night	16% 3 25% 44% 12%	416
August	1st to 10th	Night	20% 4 17% 37% 21% 1	378
	11th to 20th	Night	17% 4 23% 35% 19% 1	544
	21st to end	Night	20% 4 23% 32% 19% 2	798
September	1st to 10th	Night	22% 6% 22% 36% 12% 2	760
	11th to 20th	Night	20% 5% 22% 31% 20% 2	760
	21st to end	Night	21% 8% 27% 27% 16% 2	760
October	1st to 10th	Night	23% 8% 28% 28% 12% 1	760
	11th to 20th	Night	31% 10% 26% 25% 8% 1	760
	21st to end	Night	33% 11% 30% 22% 4	836
November	1st to 10th	Night	29% 14% 27% 25% 6%	780
	11th to 20th	Night	27% 15% 29% 19% 10% 1	800
	21st to end	Night	33% 14% 27% 20% 5% 1	800
December	1st to 10th	Night	34% 13% 29% 18% 6%	871
	11th to 20th	Night	29% 17% 29% 18% 6% 1	835
	21st to end	Night	36% 15% 27% 18% 4	836

Page generated at 2024-12-03 06:45:11. Version ac07

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