Murdochville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Murdochville 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	14% 14% 4 10% 6% 5% 5% 4 6% 6% 25%	131179
	Night	12% 13% 5% 12% 8% 7% 6% 4 5% 6% 24%	130541
Transparency	Day	57% 4 11% 18% 9% 1	134607
	Night	57% 4 11% 18% 8% 1	135203
Seeing	Day	28% 21% 30% 15% 5% 1	18154
	Night	25% 20% 29% 19% 7% 1	25905

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	6% 19% 10% 17% 8% 8% 7% 4 6% 5% 11%	4093
	11th to 20th	Day	6% 15% 5% 21% 12% 9% 6% 5% 5% 6% 10%	4084
	21st to end	Day	2 5% 3 13% 7% 8% 8% 9% 11% 9% 25%	5129
February	1st to 10th	Day	6% 11% 4 12% 8% 8% 9% 5% 6% 7% 23%	1890
	11th to 20th	Day	7% 16% 7% 14% 8% 6% 6% 4 5% 6% 23%	1843
	21st to end	Day	5% 13% 4 12% 9% 7% 6% 5% 6% 7% 25%	1568
March	1st to 10th	Day	10% 15% 6% 12% 7% 7% 6% 4 5% 7% 21%	4853
	11th to 20th	Day	12% 21% 6% 11% 6% 6% 5% 4 5% 5% 19%	5057
	21st to end	Day	16% 19% 7% 12% 5% 4 4 3 4 5% 21%	5466
April	1st to 10th	Day	13% 18% 6% 14% 8% 6% 4 3 4 4 20%	2407
	11th to 20th	Day	13% 17% 5% 11% 5% 5% 4 3 5% 5% 26%	2572
	21st to end	Day	17% 18% 5% 10% 5% 4 4 2 3 4 27%	2600
May	1st to 10th	Day	18% 22% 5% 9% 5% 4 4 3 4 5% 23%	6197
	11th to 20th	Day	18% 17% 4 9% 5% 4 4 3 5% 5% 26%	6351
	21st to end	Day	18% 17% 3 7% 5% 5% 4 3 5% 5% 27%	7451
June	1st to 10th	Day	21% 12% 4 8% 5% 5% 4 4 6% 5% 26%	3000
	11th to 20th	Day	20% 8% 3 8% 5% 4 5% 4 6% 7% 31%	3000
	21st to end	Day	23% 10% 3 8% 6% 5% 4 4 6% 6% 26%	3000
July	1st to 10th	Day	16% 8% 3 7% 5% 5% 5% 4 7% 8% 31%	6820
	11th to 20th	Day	15% 10% 3 8% 6% 6% 6% 5% 7% 8% 27%	6820
	21st to end	Day	14% 7% 2 6% 5% 4 5% 4 6% 8% 39%	7339
August	1st to 10th	Day	16% 7% 3 7% 5% 5% 6% 4 6% 8% 32%	4272
	11th to 20th	Day	18% 9% 3 8% 7% 5% 6% 5% 6% 8% 26%	4175
	21st to end	Day	13% 9% 3 7% 5% 5% 5% 4 6% 8% 38%	4675
September	1st to 10th	Day	20% 8% 3 6% 4 5% 5% 4 5% 6% 36%	2415
	11th to 20th	Day	18% 10% 3 6% 3 4 3 2 5% 6% 39%	2260
	21st to end	Day	15% 13% 4 8% 6% 4 4 3 5% 5% 33%	2181
October	1st to 10th	Day	14% 16% 3 7% 5% 4 5% 3 4 6% 33%	2000
	11th to 20th	Day	18% 23% 4 9% 4 3 3 3 4 6% 22%	2000
	21st to end	Day	19% 20% 8% 9% 4 4 3 3 5% 6% 19%	2023
November	1st to 10th	Day	14% 20% 8% 12% 6% 5% 4 4 5% 4 18%	1645
	11th to 20th	Day	14% 16% 6% 19% 6% 5% 4 3 5% 5% 16%	1680
	21st to end	Day	14% 18% 7% 18% 9% 4 3 3 5% 5% 14%	1680
December	1st to 10th	Day	9% 11% 6% 23% 15% 7% 6% 4 5% 5% 11%	2392
	11th to 20th	Day	7% 16% 6% 17% 12% 8% 6% 5% 5% 5% 15%	2688
	21st to end	Day	7% 12% 4 16% 11% 8% 6% 5% 5% 5% 21%	3553
January	1st to 10th	Night	8% 17% 8% 18% 9% 9% 8% 4 5% 4 10%	8831
	11th to 20th	Night	7% 14% 6% 17% 13% 9% 6% 4 5% 5% 15%	8831
	21st to end	Night	2 5% 4 12% 8% 8% 10% 12% 9% 7% 23%	9042
February	1st to 10th	Night	6% 11% 4 11% 9% 9% 10% 6% 6% 7% 21%	2730
	11th to 20th	Night	8% 17% 6% 11% 8% 8% 8% 6% 6% 5% 17%	2663
	21st to end	Night	5% 13% 4 11% 9% 8% 7% 4 6% 5% 26%	2233
March	1st to 10th	Night	11% 15% 5% 9% 8% 6% 8% 4 4 5% 24%	5206
	11th to 20th	Night	12% 19% 5% 11% 7% 6% 6% 3 6% 6% 18%	5057
	21st to end	Night	18% 15% 6% 10% 8% 7% 4 3 4 5% 20%	5466
April	1st to 10th	Night	15% 16% 4 13% 7% 6% 6% 3 6% 5% 20%	1989
	11th to 20th	Night	16% 14% 4 7% 5% 5% 4 3 5% 7% 31%	1778
	21st to end	Night	18% 14% 5% 9% 5% 3 4 3 5% 5% 30%	1800
May	1st to 10th	Night	18% 16% 5% 7% 5% 4 4 3 4 6% 28%	3757
	11th to 20th	Night	18% 11% 3 7% 5% 4 4 4 5% 6% 33%	3596
	21st to end	Night	12% 13% 5% 9% 6% 4 6% 4 5% 7% 29%	3455
June	1st to 10th	Night	20% 10% 3 7% 5% 5% 5% 4 5% 8% 30%	1400
	11th to 20th	Night	19% 9% 4 6% 4 5% 4 3 5% 7% 34%	1400
	21st to end	Night	21% 7% 3 7% 3 6% 6% 4 7% 6% 31%	1400
July	1st to 10th	Night	17% 8% 3 7% 4 5% 5% 4 6% 7% 34%	3160
	11th to 20th	Night	11% 8% 2 7% 4 5% 6% 6% 7% 10% 33%	3160
	21st to end	Night	10% 8% 3 7% 4 5% 4 4 5% 8% 43%	3488
August	1st to 10th	Night	14% 7% 3 6% 5% 4 5% 5% 7% 8% 36%	2876
	11th to 20th	Night	14% 7% 3 7% 5% 4 5% 4 7% 7% 35%	2872
	21st to end	Night	16% 7% 2 5% 4 3 4 3 4 6% 46%	3223
September	1st to 10th	Night	17% 8% 2 6% 4 4 4 3 5% 6% 40%	1985
	11th to 20th	Night	16% 10% 2 7% 4 4 4 4 5% 6% 38%	2137
	21st to end	Night	17% 9% 2 6% 4 3 4 3 4 6% 42%	2218
October	1st to 10th	Night	16% 10% 4 6% 5% 4 5% 4 5% 7% 35%	2400
	11th to 20th	Night	18% 17% 4 8% 5% 5% 4 3 5% 6% 26%	2400
	21st to end	Night	17% 17% 5% 9% 6% 6% 5% 4 5% 6% 21%	2811
November	1st to 10th	Night	16% 17% 8% 13% 5% 4 4 3 5% 5% 21%	2873
	11th to 20th	Night	15% 17% 6% 17% 7% 5% 4 3 5% 4 17%	2940
	21st to end	Night	13% 17% 7% 18% 9% 6% 5% 3 4 5% 13%	2940
December	1st to 10th	Night	8% 13% 5% 19% 20% 7% 5% 4 4 4 10%	5016
	11th to 20th	Night	7% 14% 7% 20% 13% 8% 5% 3 4 4 15%	5741
	21st to end	Night	10% 14% 5% 15% 9% 12% 6% 4 5% 5% 15%	7667

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	70% 4 7% 14% 4	4094
	11th to 20th	Day	73% 4 7% 11% 5%	4110
	21st to end	Day	44% 5% 9% 22% 19% 1	5129
February	1st to 10th	Day	56% 5% 8% 18% 11% 2	1890
	11th to 20th	Day	62% 4 7% 14% 12% 1	1851
	21st to end	Day	54% 6% 7% 22% 11% 2	1568
March	1st to 10th	Day	63% 3 7% 15% 11% 1	4857
	11th to 20th	Day	66% 4 7% 11% 9% 3	5057
	21st to end	Day	65% 2 4 16% 11% 1	5466
April	1st to 10th	Day	67% 4 4 12% 10% 2	2407
	11th to 20th	Day	58% 5% 7% 17% 12% 1	2572
	21st to end	Day	63% 2 8% 16% 11% 1	2600
May	1st to 10th	Day	65% 3 7% 15% 10% 1	6209
	11th to 20th	Day	60% 4 13% 17% 7%	6355
	21st to end	Day	59% 4 8% 20% 9% 1	7451
June	1st to 10th	Day	59% 4 10% 17% 10% 1	3000
	11th to 20th	Day	53% 5% 12% 18% 11% 1	3000
	21st to end	Day	59% 4 11% 17% 8%	3000
July	1st to 10th	Day	48% 5% 12% 23% 11%	6745
	11th to 20th	Day	51% 6% 18% 20% 5%	6739
	21st to end	Day	42% 5% 18% 26% 9%	7128
August	1st to 10th	Day	49% 6% 17% 23% 6%	4258
	11th to 20th	Day	55% 5% 17% 17% 6%	4214
	21st to end	Day	44% 5% 16% 26% 8% 1	4675
September	1st to 10th	Day	48% 5% 14% 23% 10%	2415
	11th to 20th	Day	47% 3 14% 26% 10%	2260
	21st to end	Day	53% 5% 11% 23% 9% 1	2181
October	1st to 10th	Day	52% 4 12% 22% 9% 1	3260
	11th to 20th	Day	62% 4 11% 16% 7%	3240
	21st to end	Day	59% 4 12% 18% 7% 1	3238
November	1st to 10th	Day	65% 6% 11% 13% 5%	1645
	11th to 20th	Day	68% 5% 10% 12% 5%	1680
	21st to end	Day	71% 4 10% 12% 3	1680
December	1st to 10th	Day	67% 4 10% 17% 2	2392
	11th to 20th	Day	65% 4 8% 16% 7%	2688
	21st to end	Day	62% 3 9% 17% 8% 1	3553
January	1st to 10th	Night	71% 3 10% 13% 3	8831
	11th to 20th	Night	67% 4 8% 13% 7% 1	8880
	21st to end	Night	46% 5% 10% 23% 14% 2	9042
February	1st to 10th	Night	54% 6% 8% 19% 11% 2	2730
	11th to 20th	Night	61% 5% 7% 17% 9% 1	2666
	21st to end	Night	53% 5% 7% 22% 11% 1	2233
March	1st to 10th	Night	61% 3 7% 17% 10% 2	5215
	11th to 20th	Night	64% 4 7% 16% 7% 1	5058
	21st to end	Night	65% 3 6% 16% 9% 1	5466
April	1st to 10th	Night	63% 6% 6% 13% 12% 1	1989
	11th to 20th	Night	52% 5% 8% 20% 14% 1	1778
	21st to end	Night	55% 3 9% 19% 12% 2	1800
May	1st to 10th	Night	57% 3 10% 19% 9% 2	3762
	11th to 20th	Night	52% 3 10% 22% 12%	3597
	21st to end	Night	54% 4 10% 23% 9%	3456
June	1st to 10th	Night	54% 3 12% 20% 10%	1400
	11th to 20th	Night	50% 3 15% 18% 13% 1	1400
	21st to end	Night	53% 6% 13% 18% 9% 1	1400
July	1st to 10th	Night	45% 7% 15% 23% 11%	3125
	11th to 20th	Night	41% 6% 23% 27% 3	3118
	21st to end	Night	37% 5% 24% 21% 12%	3385
August	1st to 10th	Night	44% 6% 20% 23% 6%	2865
	11th to 20th	Night	45% 6% 23% 20% 6%	2899
	21st to end	Night	39% 4 16% 30% 11%	3223
September	1st to 10th	Night	44% 5% 15% 27% 9%	1985
	11th to 20th	Night	45% 5% 16% 24% 10%	2137
	21st to end	Night	42% 5% 13% 26% 13% 1	2218
October	1st to 10th	Night	51% 4 10% 26% 8% 1	3920
	11th to 20th	Night	53% 5% 12% 20% 10%	3899
	21st to end	Night	56% 8% 13% 18% 5% 1	4548
November	1st to 10th	Night	61% 7% 12% 15% 5%	2873
	11th to 20th	Night	67% 5% 10% 12% 5%	2940
	21st to end	Night	70% 6% 10% 12% 2 1	2940
December	1st to 10th	Night	66% 5% 11% 16% 2	5016
	11th to 20th	Night	65% 4 10% 13% 7%	5742
	21st to end	Night	68% 3 9% 14% 5%	7667

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% 23% 32% 13% 3 1	220
	11th to 20th	Day	30% 27% 22% 15% 5% 1	220
	21st to end	Day	16% 30% 36% 13% 5% 1	287
February	1st to 10th	Day	19% 28% 31% 13% 7% 2	430
	11th to 20th	Day	24% 28% 30% 11% 5% 1	426
	21st to end	Day	22% 27% 32% 14% 5% 1	362
March	1st to 10th	Day	30% 24% 34% 8% 3 1	540
	11th to 20th	Day	31% 23% 27% 12% 5% 1	528
	21st to end	Day	30% 24% 32% 9% 3 2	550
April	1st to 10th	Day	36% 26% 26% 9% 3 1	500
	11th to 20th	Day	32% 25% 29% 11% 3 1	492
	21st to end	Day	35% 20% 28% 13% 2 2	500
May	1st to 10th	Day	32% 21% 27% 13% 6% 1	633
	11th to 20th	Day	31% 19% 26% 16% 6% 1	724
	21st to end	Day	35% 20% 26% 14% 5% 1	790
June	1st to 10th	Day	29% 18% 30% 18% 4 1	730
	11th to 20th	Day	28% 17% 28% 17% 8% 1	730
	21st to end	Day	30% 17% 27% 18% 5% 2	730
July	1st to 10th	Day	22% 15% 37% 17% 8% 1	720
	11th to 20th	Day	17% 17% 37% 22% 6% 1	718
	21st to end	Day	21% 14% 31% 24% 8% 2	795
August	1st to 10th	Day	20% 15% 36% 22% 7% 1	550
	11th to 20th	Day	21% 13% 33% 24% 8% 2	519
	21st to end	Day	20% 18% 35% 16% 9% 2	583
September	1st to 10th	Day	26% 18% 31% 17% 7% 2	530
	11th to 20th	Day	29% 17% 32% 15% 3 3	530
	21st to end	Day	27% 25% 27% 13% 6% 2	519
October	1st to 10th	Day	25% 25% 29% 12% 8% 2	420
	11th to 20th	Day	32% 24% 22% 12% 8% 2	420
	21st to end	Day	34% 23% 23% 13% 6% 1	462
November	1st to 10th	Day	32% 27% 27% 11% 3 1	425
	11th to 20th	Day	30% 25% 28% 13% 3 2	430
	21st to end	Day	34% 23% 28% 10% 3 1	430
December	1st to 10th	Day	27% 25% 32% 11% 4 2	249
	11th to 20th	Day	31% 29% 29% 10% 1	220
	21st to end	Day	29% 27% 28% 12% 3 1	242
January	1st to 10th	Night	22% 23% 34% 16% 3 1	950
	11th to 20th	Night	24% 24% 30% 16% 6% 1	950
	21st to end	Night	17% 28% 31% 17% 6% 1	947
February	1st to 10th	Night	17% 28% 33% 15% 7% 1	840
	11th to 20th	Night	23% 26% 30% 16% 5%	823
	21st to end	Night	17% 27% 33% 15% 6% 2	692
March	1st to 10th	Night	24% 24% 33% 12% 6% 1	840
	11th to 20th	Night	26% 24% 26% 16% 6% 1	829
	21st to end	Night	26% 21% 30% 17% 6% 1	880
April	1st to 10th	Night	30% 20% 31% 14% 4	639
	11th to 20th	Night	25% 22% 28% 18% 6% 1	594
	21st to end	Night	31% 16% 27% 19% 7% 1	600
May	1st to 10th	Night	30% 13% 27% 22% 9% 1	600
	11th to 20th	Night	29% 13% 25% 22% 10% 1	592
	21st to end	Night	23% 18% 33% 20% 5%	442
June	1st to 10th	Night	24% 13% 27% 29% 8% 1	400
	11th to 20th	Night	25% 11% 28% 27% 10%	400
	21st to end	Night	28% 10% 25% 27% 9% 1	400
July	1st to 10th	Night	19% 8% 37% 23% 12% 1	390
	11th to 20th	Night	15% 8% 34% 35% 9%	388
	21st to end	Night	16% 10% 29% 33% 11%	455
August	1st to 10th	Night	18% 7% 32% 32% 11% 1	598
	11th to 20th	Night	19% 8% 28% 32% 13% 1	592
	21st to end	Night	18% 11% 29% 26% 14% 2	660
September	1st to 10th	Night	21% 16% 30% 24% 9%	600
	11th to 20th	Night	22% 14% 32% 21% 9% 1	737
	21st to end	Night	25% 18% 28% 21% 7% 1	800
October	1st to 10th	Night	25% 18% 31% 19% 7% 1	800
	11th to 20th	Night	29% 19% 26% 16% 10% 1	800
	21st to end	Night	29% 22% 26% 16% 7% 1	892
November	1st to 10th	Night	33% 22% 27% 14% 4	930
	11th to 20th	Night	30% 23% 27% 13% 5% 1	950
	21st to end	Night	30% 23% 28% 13% 5%	950
December	1st to 10th	Night	25% 27% 31% 13% 4 1	950
	11th to 20th	Night	30% 26% 28% 13% 3 1	950
	21st to end	Night	27% 24% 26% 18% 4 2	1045

Page generated at 2026-03-15 02:23:52. Version ac07

Copyright © 2026 Attilla Danko.