Trois-Rivières
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Trois-Rivières clear sky chart from 2005-11-06 to 2024-11-04.

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	18% 9% 3 7% 5% 4 5% 4 5% 7% 33%	101313
	Night	19% 11% 3 8% 5% 4 4 3 5% 6% 31%	97669
Transparency	Day	50% 5% 13% 21% 9% 1	104775
	Night	54% 5% 12% 19% 9% 1	102297
Seeing	Day	22% 11% 29% 24% 11% 3	14567
	Night	24% 9% 29% 29% 9% 1	23515

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	19% 15% 5% 9% 5% 4 4 3 5% 6% 26%	2517
	11th to 20th	Day	13% 14% 6% 10% 7% 4 5% 3 4 5% 29%	2520
	21st to end	Day	12% 14% 7% 10% 6% 5% 5% 4 5% 7% 26%	2772
February	1st to 10th	Day	14% 17% 4 8% 7% 6% 4 4 4 5% 26%	1582
	11th to 20th	Day	15% 13% 5% 10% 7% 5% 5% 3 6% 5% 26%	1796
	21st to end	Day	16% 14% 4 10% 6% 5% 4 2 5% 5% 29%	1570
March	1st to 10th	Day	19% 11% 3 8% 6% 5% 5% 3 4 6% 30%	3116
	11th to 20th	Day	15% 16% 5% 10% 5% 4 3 3 4 5% 29%	3242
	21st to end	Day	15% 12% 3 8% 4 4 4 3 5% 5% 36%	4166
April	1st to 10th	Day	23% 10% 3 7% 4 4 4 4 5% 5% 31%	2280
	11th to 20th	Day	21% 6% 2 6% 3 4 4 4 5% 6% 37%	2285
	21st to end	Day	23% 10% 3 7% 5% 4 4 3 5% 6% 31%	2470
May	1st to 10th	Day	22% 8% 3 7% 5% 4 4 3 5% 7% 34%	4296
	11th to 20th	Day	16% 6% 3 8% 6% 5% 5% 5% 7% 8% 32%	4398
	21st to end	Day	16% 6% 3 8% 5% 5% 6% 4 6% 7% 35%	4837
June	1st to 10th	Day	20% 8% 3 7% 5% 5% 5% 4 6% 6% 31%	2660
	11th to 20th	Day	16% 7% 2 6% 4 5% 5% 3 6% 8% 36%	2660
	21st to end	Day	21% 9% 2 8% 5% 4 5% 4 6% 6% 30%	2660
July	1st to 10th	Day	12% 7% 3 7% 6% 5% 5% 4 7% 9% 35%	4440
	11th to 20th	Day	15% 6% 2 7% 5% 5% 5% 5% 7% 9% 34%	4440
	21st to end	Day	13% 6% 2 5% 4 4 5% 4 6% 8% 43%	4814
August	1st to 10th	Day	15% 5% 2 7% 5% 5% 6% 5% 8% 12% 29%	4423
	11th to 20th	Day	17% 6% 3 6% 5% 4 5% 4 6% 9% 35%	4090
	21st to end	Day	19% 5% 2 6% 4 4 4 3 5% 7% 39%	4188
September	1st to 10th	Day	15% 5% 2 6% 5% 4 4 4 6% 8% 41%	2280
	11th to 20th	Day	16% 5% 2 5% 4 3 4 3 5% 7% 48%	2157
	21st to end	Day	20% 6% 2 5% 4 4 4 3 5% 6% 40%	2090
October	1st to 10th	Day	21% 7% 3 7% 4 4 5% 3 5% 8% 34%	2022
	11th to 20th	Day	21% 8% 3 9% 5% 5% 4 4 6% 7% 28%	1796
	21st to end	Day	26% 10% 3 8% 3 3 4 3 5% 6% 29%	1881
November	1st to 10th	Day	19% 11% 3 7% 5% 4 5% 3 4 5% 34%	1698
	11th to 20th	Day	21% 13% 4 9% 5% 4 3 3 5% 5% 28%	1665
	21st to end	Day	23% 14% 3 7% 6% 4 4 3 5% 6% 25%	1520
December	1st to 10th	Day	27% 15% 4 8% 5% 4 3 3 4 3 24%	1409
	11th to 20th	Day	22% 15% 5% 9% 5% 4 3 3 3 5% 26%	1801
	21st to end	Day	24% 16% 5% 10% 4 4 3 3 4 4 22%	2772
January	1st to 10th	Night	17% 17% 5% 10% 5% 4 4 3 4 5% 24%	4429
	11th to 20th	Night	13% 15% 5% 13% 7% 6% 5% 4 5% 5% 25%	4440
	21st to end	Night	15% 14% 5% 13% 7% 5% 5% 4 5% 5% 24%	4884
February	1st to 10th	Night	14% 14% 5% 11% 7% 5% 4 4 5% 5% 26%	2594
	11th to 20th	Night	14% 16% 5% 11% 7% 5% 4 3 4 5% 26%	2269
	21st to end	Night	16% 14% 4 8% 5% 4 4 4 4 4 32%	1884
March	1st to 10th	Night	26% 12% 3 8% 4 3 4 3 4 5% 30%	3724
	11th to 20th	Night	19% 18% 5% 10% 5% 5% 3 3 3 4 25%	3699
	21st to end	Night	15% 12% 5% 9% 5% 4 5% 3 4 5% 34%	3466
April	1st to 10th	Night	24% 11% 3 8% 4 3 4 3 5% 6% 30%	1900
	11th to 20th	Night	22% 9% 2 6% 5% 3 4 4 4 6% 35%	1843
	21st to end	Night	23% 10% 3 6% 3 3 3 3 4 6% 35%	1710
May	1st to 10th	Night	23% 9% 3 8% 4 4 5% 3 5% 6% 29%	2660
	11th to 20th	Night	21% 8% 3 6% 5% 4 4 3 5% 7% 34%	2495
	21st to end	Night	19% 6% 3 6% 4 5% 5% 4 6% 9% 33%	2738
June	1st to 10th	Night	21% 7% 3 5% 4 5% 4 4 6% 8% 33%	1520
	11th to 20th	Night	19% 7% 2 6% 4 4 5% 5% 5% 8% 37%	1520
	21st to end	Night	20% 8% 2 6% 5% 4 5% 5% 7% 7% 31%	1520
July	1st to 10th	Night	13% 6% 3 7% 6% 6% 6% 5% 7% 9% 30%	2520
	11th to 20th	Night	18% 6% 2 7% 5% 4 4 4 6% 8% 37%	2520
	21st to end	Night	12% 5% 2 6% 4 5% 4 3 6% 7% 44%	2739
August	1st to 10th	Night	16% 7% 3 8% 5% 5% 5% 4 6% 8% 32%	2506
	11th to 20th	Night	18% 8% 2 7% 4 4 5% 4 6% 7% 35%	2705
	21st to end	Night	19% 6% 3 7% 5% 4 4 3 4 7% 38%	3466
September	1st to 10th	Night	16% 5% 2 6% 4 3 4 4 5% 7% 44%	1900
	11th to 20th	Night	17% 4 2 4 3 3 3 3 4 7% 49%	2023
	21st to end	Night	18% 6% 2 6% 5% 5% 4 3 4 6% 41%	2090
October	1st to 10th	Night	19% 6% 2 7% 5% 5% 4 3 5% 5% 39%	2156
	11th to 20th	Night	22% 8% 3 7% 4 4 4 3 5% 5% 34%	2384
	21st to end	Night	26% 8% 3 7% 5% 4 4 3 5% 6% 29%	2717
November	1st to 10th	Night	20% 10% 3 8% 5% 4 5% 3 5% 5% 32%	2453
	11th to 20th	Night	21% 11% 4 9% 4 4 4 3 4 5% 30%	2512
	21st to end	Night	24% 14% 3 8% 4 4 3 2 4 5% 27%	2660
December	1st to 10th	Night	23% 14% 5% 10% 5% 4 4 4 5% 4 22%	2759
	11th to 20th	Night	22% 16% 5% 9% 5% 3 4 2 4 5% 25%	3380
	21st to end	Night	26% 19% 4 8% 4 3 3 2 3 4 23%	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	60% 5% 13% 17% 5%	2518
	11th to 20th	Day	57% 6% 10% 20% 7%	2520
	21st to end	Day	58% 6% 10% 19% 6% 1	2772
February	1st to 10th	Day	61% 3 9% 18% 8% 2	1582
	11th to 20th	Day	59% 5% 12% 14% 9% 1	1805
	21st to end	Day	58% 3 10% 18% 9% 2	1570
March	1st to 10th	Day	56% 6% 10% 19% 8% 2	3119
	11th to 20th	Day	57% 5% 12% 13% 11% 1	3242
	21st to end	Day	49% 5% 7% 22% 14% 4	4166
April	1st to 10th	Day	55% 4 10% 17% 12% 2	2280
	11th to 20th	Day	49% 4 9% 23% 13% 2	2285
	21st to end	Day	55% 4 9% 16% 13% 3	2470
May	1st to 10th	Day	49% 6% 10% 20% 13% 2	4310
	11th to 20th	Day	46% 9% 18% 17% 9% 1	4402
	21st to end	Day	46% 7% 10% 20% 16% 1	4837
June	1st to 10th	Day	51% 6% 11% 21% 9% 2	2660
	11th to 20th	Day	45% 5% 13% 23% 12% 2	2660
	21st to end	Day	55% 5% 11% 18% 10% 1	2660
July	1st to 10th	Day	45% 6% 15% 26% 8%	4370
	11th to 20th	Day	44% 6% 20% 24% 6%	4365
	21st to end	Day	39% 6% 15% 31% 9%	4661
August	1st to 10th	Day	46% 7% 19% 22% 6%	4409
	11th to 20th	Day	46% 6% 21% 21% 6%	4130
	21st to end	Day	45% 4 15% 21% 14% 1	4188
September	1st to 10th	Day	40% 5% 16% 26% 11% 1	2280
	11th to 20th	Day	37% 5% 15% 31% 12% 1	2157
	21st to end	Day	45% 5% 13% 27% 11%	2090
October	1st to 10th	Day	47% 4 14% 28% 7%	3360
	11th to 20th	Day	51% 6% 18% 22% 3	2960
	21st to end	Day	47% 4 19% 21% 7% 1	3081
November	1st to 10th	Day	54% 4 12% 21% 9% 1	1698
	11th to 20th	Day	58% 4 11% 17% 10%	1665
	21st to end	Day	60% 6% 13% 17% 4 1	1520
December	1st to 10th	Day	66% 4 10% 16% 5%	1409
	11th to 20th	Day	64% 3 7% 19% 6%	1802
	21st to end	Day	66% 4 10% 11% 8%	2772
January	1st to 10th	Night	62% 6% 14% 13% 5%	4429
	11th to 20th	Night	61% 7% 10% 17% 4 1	4440
	21st to end	Night	62% 5% 12% 14% 7%	4884
February	1st to 10th	Night	61% 4 8% 17% 9% 1	2594
	11th to 20th	Night	61% 5% 8% 15% 10% 1	2271
	21st to end	Night	56% 3 9% 17% 13% 2	1884
March	1st to 10th	Night	57% 5% 11% 16% 8% 3	3734
	11th to 20th	Night	63% 6% 7% 14% 10% 2	3700
	21st to end	Night	53% 6% 6% 22% 11% 3	3466
April	1st to 10th	Night	56% 4 8% 16% 14% 2	1900
	11th to 20th	Night	50% 5% 8% 21% 14% 2	1843
	21st to end	Night	52% 4 8% 19% 15% 3	1710
May	1st to 10th	Night	54% 6% 11% 18% 9% 2	2666
	11th to 20th	Night	48% 8% 13% 19% 11% 2	2496
	21st to end	Night	46% 6% 10% 18% 18% 2	2739
June	1st to 10th	Night	48% 6% 12% 21% 12% 1	1520
	11th to 20th	Night	45% 6% 10% 22% 14% 3	1520
	21st to end	Night	50% 6% 11% 19% 13% 1	1520
July	1st to 10th	Night	47% 6% 17% 20% 9% 1	2480
	11th to 20th	Night	44% 6% 20% 23% 7% 1	2472
	21st to end	Night	38% 6% 20% 25% 11%	2651
August	1st to 10th	Night	48% 6% 15% 24% 6%	2496
	11th to 20th	Night	48% 6% 18% 22% 6%	2731
	21st to end	Night	47% 4 11% 24% 13% 1	3466
September	1st to 10th	Night	40% 5% 15% 27% 12% 2	1900
	11th to 20th	Night	37% 4 15% 32% 11% 1	2023
	21st to end	Night	45% 5% 9% 27% 14%	2090
October	1st to 10th	Night	51% 4 13% 24% 8%	3598
	11th to 20th	Night	48% 5% 15% 26% 6%	3959
	21st to end	Night	48% 4 16% 20% 10% 2	4467
November	1st to 10th	Night	54% 5% 11% 21% 8% 1	2453
	11th to 20th	Night	57% 5% 11% 17% 9% 1	2512
	21st to end	Night	61% 5% 12% 16% 7%	2660
December	1st to 10th	Night	66% 4 11% 14% 5%	2759
	11th to 20th	Night	63% 4 8% 18% 7%	3380
	21st to end	Night	67% 3 8% 17% 5% 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	28% 9% 34% 24% 4 1	180
	11th to 20th	Day	26% 15% 32% 19% 7% 1	180
	21st to end	Day	18% 9% 38% 23% 11% 1	198
February	1st to 10th	Day	27% 16% 38% 17% 2	210
	11th to 20th	Day	23% 12% 38% 24% 3	404
	21st to end	Day	23% 15% 34% 24% 4	382
March	1st to 10th	Day	25% 12% 30% 27% 7%	460
	11th to 20th	Day	25% 15% 32% 21% 5% 2	460
	21st to end	Day	25% 13% 33% 19% 9% 2	506
April	1st to 10th	Day	29% 10% 28% 25% 8% 1	460
	11th to 20th	Day	26% 16% 28% 21% 8% 3	452
	21st to end	Day	29% 11% 34% 17% 8% 1	460
May	1st to 10th	Day	24% 14% 33% 19% 9% 2	463
	11th to 20th	Day	18% 10% 34% 23% 12% 3	487
	21st to end	Day	20% 14% 35% 19% 11% 2	529
June	1st to 10th	Day	20% 11% 31% 25% 9% 3	490
	11th to 20th	Day	18% 11% 29% 26% 14% 3	490
	21st to end	Day	23% 8% 27% 25% 15% 2	490
July	1st to 10th	Day	14% 9% 28% 31% 16% 2	485
	11th to 20th	Day	17% 8% 29% 31% 14% 3	484
	21st to end	Day	16% 7% 26% 31% 17% 3	532
August	1st to 10th	Day	16% 6% 23% 31% 19% 5%	486
	11th to 20th	Day	15% 7% 20% 32% 19% 7%	479
	21st to end	Day	16% 9% 28% 19% 19% 9%	539
September	1st to 10th	Day	17% 8% 29% 27% 13% 6%	490
	11th to 20th	Day	14% 8% 23% 29% 18% 8%	490
	21st to end	Day	20% 9% 26% 23% 15% 6%	490
October	1st to 10th	Day	22% 13% 24% 26% 12% 3	490
	11th to 20th	Day	25% 10% 29% 23% 11% 2	435
	21st to end	Day	30% 12% 28% 23% 7%	429
November	1st to 10th	Day	27% 14% 27% 26% 6% 1	374
	11th to 20th	Day	27% 15% 27% 25% 6%	325
	21st to end	Day	31% 19% 23% 19% 6% 2	180
December	1st to 10th	Day	36% 10% 24% 22% 6% 2	180
	11th to 20th	Day	26% 19% 33% 15% 6% 1	180
	21st to end	Day	32% 16% 27% 16% 7% 2	198
January	1st to 10th	Night	30% 9% 31% 24% 5%	760
	11th to 20th	Night	28% 10% 32% 25% 6%	760
	21st to end	Night	19% 7% 32% 35% 7%	836
February	1st to 10th	Night	19% 9% 38% 27% 6% 1	760
	11th to 20th	Night	22% 11% 37% 24% 5% 1	743
	21st to end	Night	25% 10% 31% 28% 5%	628
March	1st to 10th	Night	24% 10% 32% 31% 4	760
	11th to 20th	Night	24% 13% 32% 26% 6%	760
	21st to end	Night	22% 12% 32% 26% 7%	836
April	1st to 10th	Night	29% 9% 27% 28% 7%	760
	11th to 20th	Night	26% 13% 29% 27% 5%	719
	21st to end	Night	29% 10% 30% 24% 7%	570
May	1st to 10th	Night	28% 9% 29% 28% 7%	474
	11th to 20th	Night	24% 6% 32% 31% 6% 1	374
	21st to end	Night	23% 7% 34% 28% 8%	411
June	1st to 10th	Night	23% 6% 26% 35% 9% 1	380
	11th to 20th	Night	21% 4 24% 40% 11%	380
	21st to end	Night	21% 5% 27% 34% 13%	380
July	1st to 10th	Night	15% 5% 28% 36% 15% 1	370
	11th to 20th	Night	16% 4 21% 42% 15% 1	368
	21st to end	Night	14% 4 25% 41% 15% 1	416
August	1st to 10th	Night	15% 3 14% 45% 21% 1	378
	11th to 20th	Night	15% 3 23% 38% 20% 1	509
	21st to end	Night	17% 5% 23% 35% 18% 2	826
September	1st to 10th	Night	17% 6% 26% 38% 12% 2	760
	11th to 20th	Night	18% 6% 23% 31% 21% 1	760
	21st to end	Night	21% 6% 26% 30% 15% 2	760
October	1st to 10th	Night	21% 7% 30% 30% 11%	760
	11th to 20th	Night	25% 10% 27% 29% 9% 1	760
	21st to end	Night	29% 10% 32% 24% 5%	836
November	1st to 10th	Night	26% 11% 27% 28% 7% 1	755
	11th to 20th	Night	27% 10% 31% 22% 10% 1	760
	21st to end	Night	32% 12% 25% 24% 7%	760
December	1st to 10th	Night	31% 10% 28% 24% 7%	807
	11th to 20th	Night	29% 10% 30% 24% 7%	803
	21st to end	Night	34% 11% 25% 23% 6% 1	836

Page generated at 2024-11-01 22:47:39. Version ac07

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